MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'NMR in Biomedicine' source. Thu, 09 Feb 2012 03:37:48 +0100 http://www.medworm.com/index.php?rid=5669845&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2779 The objective of this study was to demonstrate the feasibility of simultaneous bilateral hip imaging at 7 Tesla. Hip joint MRI becomes clinically critical since recent advances have made hip arthroscopy an efficacious approach to treat a variety of early hip diseases. The success of these treatments requires a reliable and accurate diagnosis of intraarticular abnormalities at an early stage. Articular cartilage assessment is especially important to guide surgical decisions but is difficult to achieve with current MR methods. Because of gains in tissue contrast and spatial resolution reported at ultra high magnetic fields, there are strong expectations that imaging the hip joint at 7 Tesla will improve diagnostic accuracy. Furthermore, there is growing evidence that the majority of these hi... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5669845 Tue, 07 Feb 2012 05:00:00 +0100 5669845 http://www.medworm.com/index.php?rid=5669844&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2777 We report studies of the effect of ischemia on the metabolic activity of the intact perfused lung and its restoration after a period of reperfusion. Two groups of rat lungs were studied using hyperpolarized 1‐13C pyruvate to compare the rate of lactate labeling differing only in the temporal ordering of ischemic and normoxic acquisitions. In both cases, a several‐fold increase in lactate labeling was observed immediately after a 25‐min ischemia event as was its reversal back to the baseline after 30–40 min of resumed perfusion (n = 5, p < 0.025 for both comparisons). These results were corroborated by 31P spectroscopy and correspond well to measured changes in lactate pool size determined by 1H spectroscopy of freeze‐clamped specimens. Copyright © 2012 John Wiley &a... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5669844 Tue, 07 Feb 2012 05:00:00 +0100 5669844 http://www.medworm.com/index.php?rid=5669848&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2768 The use of contrast agents has added considerable value to the existing cardiac MRI toolbox that can be used to study murine myocardial infarction, as it enables detailed in vivo visualization of the molecular and cellular processes that occur in the infarcted and remote tissue. A variety of non‐targeted and targeted contrast agents to study myocardial infarction are available and under development. Manganese, which acts as a calcium analogue, can be used to assess cell viability. Traditionally, low‐molecular‐weight Gd‐containing contrast agents are employed to measure infarct size in a late gadolinium enhancement experiment. Gd‐based blood‐pool agents are used to study the vascular status of the myocardium. The use of targeted contrast agents facilitates more detailed imaging ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5669848 Mon, 06 Feb 2012 05:00:00 +0100 5669848 http://www.medworm.com/index.php?rid=5669847&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2767 Mouse models are increasingly used to study the pathophysiology of myocardial infarction in vivo. In this area, MRI has become the gold standard imaging modality, because it combines high spatial and temporal resolution functional imaging with a large variety of methods to generate soft tissue contrast. In addition, (target‐specific) MRI contrast agents can be employed to visualize different processes in the cascade of events following myocardial infarction. Here, the MRI sequence has a decisive role in the detection sensitivity of a contrast agent. However, a straightforward translation of clinically available protocols for human cardiac imaging to mice is not feasible, because of the small size of the mouse heart and its extremely high heart rate. This has stimulated intense research i... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5669847 Mon, 06 Feb 2012 05:00:00 +0100 5669847 http://www.medworm.com/index.php?rid=5669846&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2775 In conclusion, the R2* response to hyperoxic respiratory challenge was stronger for carbogen than for oxygen, and increased quadratically with the static magnetic field strength for both challenges, which highlights the importance of high field strengths for future studies aimed at probing oxygen physiology in clinical settings. Copyright © 2012 John Wiley & Sons, Ltd.In this study, the R2* response of the cortical gray matter to respiratory challenges was quantified at 1.5, 3 and 7 T. Hyperoxic challenges resulted in a decrease in the relaxation rate at all field strengths. The response to hyperoxic hypercapnia was 1.3 times larger than to hyperoxia. Both challenges led to a quadratic increase in the R2* response with B0. High field strengths may allow the probing of oxygen physiol... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5669846 Mon, 06 Feb 2012 05:00:00 +0100 5669846 http://www.medworm.com/index.php?rid=5651982&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2776 Glioblastoma is the most common primary brain tumor and is uniformly fatal despite aggressive surgical and adjuvant therapy. As survival is short, it is critical to determine the value of therapy early on in treatment. Improved early predictive assessment would allow neuro‐oncologists to personalize and adjust or change treatment sooner to maximize the use of efficacious therapy. During carcinogenesis, tumor suppressor genes can be silenced by aberrant histone deacetylation. This epigenetic modification has become an important target for tumor therapy. Suberoylanilide hydroxamic acid (SAHA, Vorinostat, Zolinza) is an orally active, potent inhibitor of histone deacetylase (HDAC) activity. A major shortcoming of the use of HDAC inhibitors in the treatment of patients with brain tumors is t... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5651982 Thu, 02 Feb 2012 05:00:00 +0100 5651982 http://www.medworm.com/index.php?rid=5669842&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2774 Adoptive transfer of cells for therapeutic purposes requires efficient and precise delivery to the target organ whilst preserving cell function. Therefore, therapeutically applied cells need to migrate and integrate within their target tissues after delivery, e.g. dendritic cells (DCs) need to migrate to lymph nodes to elicit an antigen‐specific immune response. Previous studies have shown that inappropriate cell delivery can hinder DC migration and result in insufficient immune induction. As migration can be extremely difficult to study quantitatively in vivo, we propose an in vitro assay that reproduces key in vivo conditions to optimize cell delivery and migration in vivo. Using DC migration along a chemokine gradient, we describe here a novel 19 F MR‐based, large‐scale, quantit... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5669842 Wed, 01 Feb 2012 05:00:00 +0100 5669842 http://www.medworm.com/index.php?rid=5651981&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2780 In this study, the BOLD effect is investigated under different levels of oxygen inhalation for the development of a novel angiographic MRI technique, blood oxygen level dependent angiography (BOLDangio). Under short‐term (<10 min) generalized hypoxia induced by inhalation of 8% oxygen, we measure BOLD contrast as high as 25% from vessels at 9.4T using a simple gradient echo (GRE) pulse sequence. This produces high‐resolution 2D and 3D maps of normal and tumour brain vasculature in less than 10 minutes. Additionally, this technique reliably detects metastatic tumours and tumour‐induced intracranial hemorrhage. BOLDangio provides a sensitive research tool for MRI of vasculature under normal and pathological conditions. Thus, it may be applied as a simple monitoring technique for mea... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5651981 Wed, 01 Feb 2012 05:00:00 +0100 5651981 http://www.medworm.com/index.php?rid=5651988&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2781 The aim of this study was to gage the magnitude of changes of the apparent renal medullary transverse relaxation time (ΔT2*) induced by inhalation of pure oxygen (O2) or carbogen (95% O2, 5% CO2) versus baseline breathing of room air. Eight healthy volunteers underwent 2D multi‐gradient echo MR imaging at 1.5 T and 3.0 T. Parametrical T2* relaxation time maps were computed and average T2* was measured in regions of interest placed in the renal medulla and cortex. The largest T2* changes were measured in the renal medulla, with a relative ∆T2* of 33.8 ± 22.0% (right medulla) and 34.7 ± 17.6% (left medulla) as compared to room air for oxygen breathing (p > 0.01), and 53.8 ± 23.9% and 53.5 ± 33.9% (p < 0.01) for carbogen breathing, respectively at 3�... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5651988 Tue, 31 Jan 2012 05:00:00 +0100 5651988 http://www.medworm.com/index.php?rid=5651987&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2773 A new pulse sequence based on intermolecular double‐quantum coherences was proposed to obtain one‐dimensional high‐resolution liquid NMR spectra in inhomogeneous magnetic fields via Hadamard encoding. In contrast with the conventional intermolecular multiple‐quantum coherences method with a two‐dimensional acquisition to obtain one one‐dimensional high‐resolution spectrum, the new method can provide relatively high‐resolution spectra directly through one‐dimensional acquisition, and can greatly improve the signal‐to‐noise ratio of the spectrum within a relatively short acquisition time. Theoretical derivation was performed and analytical expressions of the resulting signals are given. Solution samples in purposely de‐shimmed magnetic fields and pig brain tissue samp... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5651987 Tue, 31 Jan 2012 05:00:00 +0100 5651987 http://www.medworm.com/index.php?rid=5651986&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2764 A novel spectroscopic method for submillisecond TEs and three‐dimensional arbitrarily shaped voxels was developed and applied to phantom and in vivo measurements, with additional parallel excitation (PEX) implementation. A segmented spherical shell excitation trajectory was used in combination with appropriate radiofrequency weights for target selection in three dimensions. Measurements in a two‐compartment phantom realized a TE of 955 µs, excellent spectral quality and comparable signal‐to‐noise ratios between accelerated (R = 2) and nonaccelerated modes. The two‐compartment model allowed a comparison of the spectral suppression qualities of the method and, although outer volume signals were suppressed by factors of 1434 and 2246 compared with the theoretical unsuppressed... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5651986 Tue, 31 Jan 2012 05:00:00 +0100 5651986 http://www.medworm.com/index.php?rid=5651985&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2771 In this study, mean global CBF was measured in 21 infants under the age of one, using non‐invasive MRI techniques adapted to the neonatal population. Mean CBF was computed as the ratio of blood flow delivered to the brain (measured using phase contrast MRI) and brain volume (computed by segmenting anatomical MR images). Tests in adult volunteers and repeated measurements showed the flow measurements using the proposed method to be both accurate and reproducible. It was also found that cardiac gating need not be employed in infants with no known cardiac pathology.The developed technique can easily be appended to a neonatal MRI examination to provide rapid, robust, and non‐invasive estimates of mean CBF, thus providing a means to monitor developmental or pathology‐related alterations i... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5651985 Tue, 31 Jan 2012 05:00:00 +0100 5651985 http://www.medworm.com/index.php?rid=5651984&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2763 The noninvasive assessment of regional lung ventilation is of critical importance in the quantification of the severity of disease and evaluation of response to therapy in many pulmonary diseases. This work presents, for the first time, the implementation of a hyperpolarized (HP) gas MRI technique to measure whole‐lung regional fractional ventilation (r) in Yorkshire pigs (n = 5) through the use of a gas mixing and delivery device in the supine position. The proposed technique utilizes a series of back‐to‐back HP gas breaths with images acquired during short end‐inspiratory breath‐holds. In order to decouple the radiofrequency pulse decay effect from the ventilatory signal build‐up in the airways, the regional distribution of the flip angle (α) was estimated in the imaged ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5651984 Tue, 31 Jan 2012 05:00:00 +0100 5651984 http://www.medworm.com/index.php?rid=5651983&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2783 MRI with zero echo time (ZTE) is achieved by 3D radial centre‐out encoding and hard‐pulse RF excitation while the projection gradient is already on. Targeting short‐T2 samples, the efficient, robust and silent ZTE approach was implemented for high‐bandwidth high‐resolution imaging requiring particularly rapid transmit‐receive switching and algebraic image reconstruction. The ZTE technique was applied to image extracted human teeth at 11.7T field strength, yielding detailed depictions with very good delineation of the mineralised dentine and enamel layers. ZTE results are compared with UTE (ultra‐short echo time) MRI and micro‐computed tomography (μCT), revealing significant differences in SNR and CNR yields. Compared to μCT, ZTE MRI appears to be less susceptible to artef... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5651983 Tue, 31 Jan 2012 05:00:00 +0100 5651983 http://www.medworm.com/index.php?rid=5640127&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1804 We present two new approaches for noninvasive monitoring of tissue engineered constructs and apply them to maturing engineered cartilage. First, multiexponential T2 analysis showed a significant increase in proteoglycan‐associated water content with maturation. Second, multivariate support vector machine analysis using multiple MR parameters improved characterization of maturation stage as compared with univariate analysis, using individual parameters. Thus, multiexponential and multivariate approaches show substantial potential for improving sensitivity and molecular specificity in the evaluation of engineered cartilage tissue. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5640127 Mon, 30 Jan 2012 09:21:41 +0100 5640127 http://www.medworm.com/index.php?rid=5631455&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2766 Altered choline phospholipid metabolism is a hallmark of cancer, leading to malignant choline metabolite profiles consisting of low glycerophosphocholine (GPC) and high phosphocholine (PC) in human breast cancers. Glycerophosphocholine phosphodiesterase (GPC‐PDE) catalyzes the degradation of GPC to free choline and glycerol‐3‐phosphate. The gene(s) encoding for the GPC‐PDE(s) responsible for GPC degradation in breast cancers have not yet been identified. Here, we demonstrate for the first time that the GPC‐PDE encoded by glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5) is associated with breast cancer malignancy. Two human breast cancer cell lines (n = 8 and n = 10) and primary human breast tumor samples (n = 19) were studied with combined MRS and q... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5631455 Fri, 27 Jan 2012 08:25:29 +0100 5631455 http://www.medworm.com/index.php?rid=5640128&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2772 Chronic fatigue syndrome (CFS) is a complex illness, which is often misdiagnosed as a psychiatric illness. In two previous reports, using 1H MRSI, we found significantly higher levels of ventricular cerebrospinal fluid (CSF) lactate in patients with CFS relative to those with generalized anxiety disorder and healthy volunteers (HV), but not relative to those with major depressive disorder (MDD). In this third independent cross‐sectional neuroimaging study, we investigated a pathophysiological model which postulated that elevations of CSF lactate in patients with CFS might be caused by increased oxidative stress, cerebral hypoperfusion and/or secondary mitochondrial dysfunction. Fifteen patients with CFS, 15 with MDD and 13 HVs were studied using the following modalities: (i) 1H MRSI to m... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5640128 Fri, 27 Jan 2012 05:00:00 +0100 5640128 http://www.medworm.com/index.php?rid=5631457&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2765 ABSTRACTThe apparent diffusion coefficient (ADC) of hyperpolarized (HP) gases is a parameter that reflects changes in lung microstructure. However, ADC is dependent on many physiological and experimental variables that need to be controlled or specified in order to ensure the reliability and reproducibility of this parameter. A single breath‐hold experiment is desirable in order to reduce the amount of consumed HP gas. The application of a positive end‐expiratory pressure (PEEP) causes an increase in the residual gas volume. Depending on the applied PEEP, the ratio between the incoming and residual gas volumes will change and the ADC will vary, as long as both gases do not have the same diffusion coefficient. The most standard method for human applications uses air for breathing and a ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5631457 Wed, 25 Jan 2012 05:00:00 +0100 5631457 http://www.medworm.com/index.php?rid=5631456&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2778 In this study, hyperpolarized [1‐13C]lactate was used to acquire time‐resolved spectra from the healthy rat heart in vivo and to measure dichloroacetate (DCA)‐modulated changes in flux through pyruvate dehydrogenase (PDH). Both primary oxidation of lactate to pyruvate and subsequent conversion of pyruvate to alanine and bicarbonate could reliably be detected. Since DCA stimulates the activity of PDH through inhibition of PDH kinase, a more than 2.5‐fold increase in bicarbonate‐to‐substrate ratio was found after administration of DCA, similar to the effect when using [1‐13C]pyruvate as the substrate. Copyright © 2012 John Wiley & Sons, Ltd.Since lactate serves as an important energy source for the heart, hyperpolarized [1‐13C]lactate could potentially be used as an alte... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5631456 Wed, 25 Jan 2012 05:00:00 +0100 5631456 http://www.medworm.com/index.php?rid=5612582&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2751 No abstract is available for this article. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5612582 Sat, 21 Jan 2012 07:56:57 +0100 5612582 http://www.medworm.com/index.php?rid=5600461&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1815 Fiber tracking in combination with functional MRI has recently attracted strong interest, as it may help to elucidate the structural basis for functional connectivities and may be selective in the determination of the fiber bundles responsible for a particular circuit. Diffusion spectrum imaging provides a more complex analysis of fiber circuits than the commonly used diffusion tensor imaging approach, also allowing the discrimination of crossing fibers in the brain. For the understanding of pathophysiological alterations during brain lesion and recovery, such studies need to be extended to small‐animal models. In this article, we present the first study combining functional MRI with high‐resolution diffusion spectrum imaging in vivo. We have chosen the well‐characterized electrical ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5600461 Mon, 16 Jan 2012 05:00:00 +0100 5600461 http://www.medworm.com/index.php?rid=5600460&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1801 This study aimed to use Magnetic Resonance Elastography (MRE), a noninvasive imaging technique, to assess the time‐course of passive elasticity changes in the medial gastrocnemius and soleus muscles before and after a bout of eccentric exercise. Shear storage modulus (G′) and loss modulus (G′′) measurements were made in eight healthy subjects for both muscles in vivo before, one hour after, 48 hours after and 1 week after eccentric exercise. The results show a 21% increase in medial gastrocnemius storage modulus following eccentric exercise with a peak occurring ~48 hours after exercise (before exercise 1.15 ± 0.23 kPa, 48 hours after 1.38 ± 0.27 kPa). No significant changes in soleus muscle storage modulus were measured for the exercise protocol used in this study,... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5600460 Mon, 16 Jan 2012 05:00:00 +0100 5600460 http://www.medworm.com/index.php?rid=5600459&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1810 In this study, we investigated the relationship between white matter structure and diffusion parameters measured by DTI. We used micrographs from light microscopy of fixed, myelin‐stained brain sections as a gold standard for direct comparison with data from DTI. Relationships between microscopic tissue properties observed with light microscopy (fiber orientation, density and coherence) and fiber properties observed by DTI (tensor orientation, diffusivities and fractional anisotropy) were investigated. Agreement between the major eigenvector of the tensor and myelinated fibers was excellent in voxels with high fiber coherence. In addition, increased fiber spread was strongly associated with increased radial diffusivity (p = 6 × 10–6) and decreased fractional anisotropy (p =�... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5600459 Mon, 16 Jan 2012 05:00:00 +0100 5600459 http://www.medworm.com/index.php?rid=5600458&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2770 The prognostic potential of apparent diffusion coefficient (ADC) mapping was studied as complemented by high‐resolution 3D T1‐weighted MRI in the assessment of dentin‐pulp complex response to caries. Twenty‐six extracted human teeth, with or without caries lesions of different grades in accord with the International Caries Detection and Assessment System (ICDAS), were analyzed by high‐resolution MRI at 2.35 T. A signal rise in demineralized hard dental tissues in high‐resolution T1‐weighted MR images enabled assessment of the demineralization depth over the whole range of ICDAS scores. ADC maps of the teeth were calculated from corresponding diffusion‐weighted images of four different b values: 0, 132, 317, 635 s/mm2. These maps enabled reliable differentiation between ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5600458 Sun, 01 Jan 2012 05:00:00 +0100 5600458 http://www.medworm.com/index.php?rid=5586672&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.2750 No abstract is available for this article. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5586672 Sun, 01 Jan 2012 05:00:00 +0100 5586672 http://www.medworm.com/index.php?rid=5528334&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1814 In conclusion, kinetic MRI parameters and change in ADC have been found to serve as sensitive and early biomarkers of VEGF‐Trap anti‐vascular targeted therapy. Copyright © 2011 John Wiley & Sons, Ltd.DCE‐MRI and MRI DW‐MRI were evaluated for detecting response of intracerebral 9L gliomas to the antivascular agent VEGF‐Trap. A significant drop in permeability parameters was observed 24 hours following the first dose of VEGF‐Trap accompanied by a decline in ADC values. VEGF‐Trap‐treated animals also required a significantly longer time for their tumors to reach 300% initial tumor volume compared to the untreated animals. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5528334 Thu, 22 Dec 2011 05:00:00 +0100 5528334 http://www.medworm.com/index.php?rid=5528333&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1805 This work describes a new approach for high‐spatial‐resolution 1H MRSI of the human brain at 7 T. 1H MRSI at 7 T using conventional approaches, such as point‐resolved spectroscopy and stimulated echo acquisition mode with volume head coils, is limited by technical difficulties, including chemical shift displacement errors, B0/B1 inhomogeneities, a high specific absorption rate and decreased T2 relaxation times. The method presented here is based on free induction decay acquisition with an ultrashort acquisition delay (TE*) of 1.3 ms. This allows full signal detection with negligible T2 decay or J‐modulation. Chemical shift displacement errors were reduced to below 5% per part per million in the in‐slice direction and were eliminated in‐plane. The B1 sensitivity was reduce... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5528333 Thu, 22 Dec 2011 05:00:00 +0100 5528333 http://www.medworm.com/index.php?rid=5528335&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1809 This study demonstrates the use of the higher signal‐to‐noise ratio at 7 T for significant improvement in anatomical resolution of the cervical spinal cord. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5528335 Tue, 20 Dec 2011 05:00:00 +0100 5528335 http://www.medworm.com/index.php?rid=5489459&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1807 In this study, we have developed a direct 17O MRS approach to examine the feasibility and sensitivity of detecting metabolically produced H217O in isolated rat hearts perfused with 17O2‐enriched Krebs–Henseleit buffer containing normal (1.5 mm) and high (2.5 mm) calcium (Ca2+) concentrations to induce high workload. Consistent with increased workload at high Ca2+ concentration, the measured myocardial oxygen consumption rate (MVO2) increased by 82%. Dynamic 17O MRS showed an accelerated increase in the H217O signal at high Ca2+ concentration, suggesting increased mitochondrial production of H217O in concordance with the increased workload. A compartment model was developed to describe the kinetics of H217O production as a function of MVO2. The myocardial 17O2 consumption rate (MV17... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5489459 Fri, 09 Dec 2011 05:00:00 +0100 5489459 http://www.medworm.com/index.php?rid=5489458&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1811 The numerical optimization of a three‐channel radiofrequency (RF) coil with a physical aperture for the open, vertical‐field, MR‐guided, focused ultrasound surgery (MRgFUS) system using the hybrid method of moment (MoM)/finite difference time domain (FDTD) method is reported. The numerical simulation of the current density distribution on an RF coil with a complicated irregular structure was performed using MoM. The electromagnetic field simulation containing the full coil–tissue interactions within the region of interest was accomplished using the FDTD method. Huygens' equivalent box with six surfaces smoothly connected the MoM and FDTD method. An electromagnetic model of the human pelvic region was reconstructed and loaded in the FDTD zone to optimize the three‐channel RF coil ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5489458 Fri, 09 Dec 2011 05:00:00 +0100 5489458 http://www.medworm.com/index.php?rid=5489457&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1803 T2 relaxation time mapping provides information about the biochemical status of intervertebral discs. The present study aimed to determine whether texture features extracted from T2 maps or geometric parameters are sensitive to the presence of abnormalities at the posterior aspect of lumbar intervertebral discs, i.e. bulging and herniation. Thirty‐one patients (21 women and 10 men; age range 18–51 years) with low back pain were enrolled. MRI of the lumbar spine at 3.0 Tesla included morphological T1‐ and T2‐weighted fast spin‐echo sequences, and multi‐echo spin‐echo sequences that were used to construct T2 maps. On morphological MRI, discs were visually graded into ‘normal’, ‘bulging’ or ‘herniation’. On T2 maps, texture analysis (based on the co‐occurrence ma... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5489457 Fri, 09 Dec 2011 05:00:00 +0100 5489457 http://www.medworm.com/index.php?rid=5470863&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1799 A new 2 T 3‐element orthogonal knee coil array based on the three‐dimensional orthogonality principle was designed, constructed and used in a series of pilot magnetic resonance imaging (MRI) studies on a standardized phantom, and human and pig knees. The coil elements within this new coil array are positioned orthogonal to one another allowing problematic mutual coupling effects to be minimized without the use of any passive mutual decoupling schemes. The proposed method is appropriate for the design of transmit, receive and/or transceive radiofrequency (RF) coil arrays for applications in animal/human MRI and spectroscopic studies. Experimental results demonstrated that the 3‐element orthogonal knee coil array could be angled arbitrarily, including at 90°, relative to the main st... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5470863 Fri, 02 Dec 2011 05:00:00 +0100 5470863 http://www.medworm.com/index.php?rid=5470862&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1800 This study highlights the importance of clinically relevant osteogenic models of human prostate cancer and the value of such models not only in enhancing our understanding of tumorigenesis, metastasis and response to therapy, but also for development of appropriate methods for noninvasive imaging of these processes. Copyright © 2011 John Wiley & Sons, Ltd.Macromolecular contrast enhanced MRI combined with histology reveals differences in vascular permeability patterns in osteolytic (PC‐3MM2; A) and osteoblastic (MDA‐PCa‐118b; B) prostate bone metastases‐derived models. PC‐3MM2 forms thin tumor‐core blood vessels and enlarged leaky peripheral vessels, whereas MDA‐PCa‐118b recruits bone‐forming cells and pericytes such that small tumor nests are encircled with leaky ve... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5470862 Fri, 02 Dec 2011 05:00:00 +0100 5470862 http://www.medworm.com/index.php?rid=5470861&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1806 (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5470861 Fri, 02 Dec 2011 05:00:00 +0100 5470861 http://www.medworm.com/index.php?rid=5470860&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1798 Chemical exchange saturation transfer (CEST) imaging has been used experimentally in a large range of applications. However, full quantification of CEST effects in vivo using standard imaging sequences is time consuming as a large number of saturation frequency offsets, each followed by an imaging readout, are required to define a z spectrum. Furthermore, outside the brain, the presence of fat can confound the interpretation of z spectra. A novel acquisition and post‐processing technique is presented in this study, named exchange‐modulated point‐resolved spectroscopy (EXPRESS), which aims to address these limitations and to enable spatially localised, high signal‐to‐noise measurements of CEST effects in vivo. Using amide proton exchange (APT) measurements in tumours, it is de... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5470860 Fri, 02 Dec 2011 05:00:00 +0100 5470860 http://www.medworm.com/index.php?rid=5470859&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1808 Multiple pulsed field gradient diffusion sequences have received renewed interest in recent years as a potentially new type of MRI contrast. This attention is largely a result of the ability to measure pore sizes using low‐amplitude diffusion gradients, and to distinguish between macroscopically isotropic systems of anisotropic pores and systems of isotropic pores. In this article, it is shown that, under many circumstances, the same type of information can be obtained by combining two or more standard single pulse diffusion‐weighted experiments acquired at different diffusion times. Similarly, information from multiple pulsed field gradient diffusion can be reconstructed from several single pulsed diffusion experiments. This possibility is rooted in the information contained in the ti... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5470859 Fri, 02 Dec 2011 05:00:00 +0100 5470859 http://www.medworm.com/index.php?rid=5563292&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1689 In conclusion, the results of DWI in combination with whole‐body MRI were comparable with those of integrated PET/CT. Copyright © 2011 John Wiley & Sons, Ltd.Eight patients with aggressive non‐Hodgkin's lymphoma were imaged by MRI, including diffusion‐weighted imaging, and positron emission tomography/computed tomography (PET/CT) before treatment (E1), and after 1 week (E2) and two cycles (E3) of chemotherapy. The mean pre‐therapy apparent diffusion coefficient (ADC) was 0.71 × 10–3 mm2/s; it increased by 77% at E2 (p<0.05) and 24% more at E3. The results of DWI in combination with whole‐body MRI were found to be comparable with those of integrated PET/CT. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5563292 Thu, 01 Dec 2011 05:00:00 +0100 5563292 http://www.medworm.com/index.php?rid=5554151&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1813 MRS of hyperpolarized 13C‐labeled compounds represents a promising technique for in vivo metabolic studies. However, robust quantification and metabolic modeling are still important areas of investigation. In particular, time and spatial resolution constraints may lead to the analysis of MRS signals with low signal‐to‐noise ratio (SNR). The relationship between SNR and the precision of quantitative analysis for the evaluation of the in vivo kinetic behavior of metabolites is unknown. In this article, this topic is addressed by Monte Carlo simulations, covering the problem of MRS signal model parameter estimation, with strong emphasis on the peak amplitude and kinetic model parameters. The results of Monte Carlo simulation were confirmed by in vivo experiments on medium‐sized animal... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5554151 Tue, 01 Nov 2011 04:00:00 +0100 5554151 http://www.medworm.com/index.php?rid=5528332&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1802 In this study abdominal spectra acquired from single‐voxel ‘free‐breathing’ measurements in liver of healthy volunteers and in abdominal tumours of cancer patients were compared with those of prospective gating and with an implementation of offline correction. The two motion compensation methodologies were assessed in terms of SNR, linewidth and repeatability.Our experiments show that prospective gating and offline correction result in a 12–22% reduction in median tCho linewidth, while offline correction also provides a significant increase in SNR. The repeatability coefficient (the expected interval for 95% of repeat measurements) for tCho/water ratio was reduced by 37% (prospective gating) and 41% (offline correction).Both methods of motion compensation substantially improved t... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5528332 Tue, 01 Nov 2011 04:00:00 +0100 5528332 http://www.medworm.com/index.php?rid=5517089&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1812 We describe a new method for quantitative flow measurements using phase‐contrast MRI in real time. The approach combines bipolar velocity‐encoding gradients of alternating polarity with strongly undersampled radial fast low‐angle shot (FLASH) acquisitions and phase‐sensitive image reconstructions by regularized nonlinear inversion. Preliminary applications focused on through‐plane flow in the ascending aorta of healthy subjects at a temporal resolution of 48 ms. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5517089 Tue, 01 Nov 2011 04:00:00 +0100 5517089 http://www.medworm.com/index.php?rid=5489456&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1780 An important step in the implementation of three‐dimensional in vivo proton magnetic resonance spectroscopic imaging (1H‐MRSI) of the prostate is the placement of spatial saturation pulses around the region of interest (ROI) for the removal of unwanted contaminating signals from peripheral tissue. The present study demonstrates the use of a technique called conformal voxel magnetic resonance spectroscopy (CV‐MRS). This method automates the placement, orientation, timing and flip angle of very selective saturation (VSS) pulses around an irregularly‐shaped, user‐defined ROI. The method employs a user adjustable number of automatically positioned VSS pulses (20 used in the present study) which null the signal from periprostatic lipids while closely conforming the shape of the excita... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5489456 Tue, 01 Nov 2011 04:00:00 +0100 5489456 http://www.medworm.com/index.php?rid=5470858&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1792 In this study, we used a different approach and measured white matter δa (mean ± standard deviation, 1541 ± 173 ms) by determining the arrival times of exogenous contrast agent in a bolus tracking experiment. The data also confirmed δa of gray matter to be 912 ± 209 ms. In the second part of this study, we used these parameters in PCASL kinetic models and compared relative CBF (rCBF, with respect to the whole brain) maps with those measured using a single photon emission computed tomography (SPECT) technique. It was found that the use of tissue‐specific δa in the PCASL model was helpful in improving the correspondence between the two modalities. On a regional level, the gray/white matter CBF ratios were 2.47 ± 0.39 and 2.44 ± 0.18 for PCASL and SPECT, resp... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5470858 Tue, 01 Nov 2011 04:00:00 +0100 5470858 http://www.medworm.com/index.php?rid=5451305&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1788 This study demonstrates the feasibility of using the MR reporter ferritin for the noninvasive imaging and quantification of metastatic melanoma cells in the lymph nodes (LNs) of living mice. A B16F10 murine melanoma cell line expressing human ferritin heavy chain (hFTH) and green fluorescent protein (GFP) was constructed to allow the detection of cells by MRI and fluorescence imaging. Stable overexpression of hFTH and GFP in B16F10 murine melanoma cells was feasible and showed no cellular toxicity. In addition, hFTH cells were detectable by 9.4‐T MRI in vitro and in vivo, yielding significant changes in T2* relative to control cells. In BALB/c nude mice, the presence of hFTH‐ and GFP‐expressing metastatic melanoma cells in deep‐seated axillary LNs was demonstrated as areas of l... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5451305 Tue, 01 Nov 2011 04:00:00 +0100 5451305 http://www.medworm.com/index.php?rid=5433927&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1794 Over 20 000 MR systems are currently installed worldwide and, although the majority operate at magnetic fields of 1.5 T and below (i.e. about 70%), experience with 3‐T (in high‐field clinical diagnostic imaging and research) and 7‐T (research only) human MR scanners points to a future in functional and metabolic MR diagnostics. Complementary to previous studies, this review attempts to provide an overview of ultrahigh‐field MR research with special emphasis on emerging clinical applications at 7 T. We provide a short summary of the technical development and the current status of installed MR systems. The advantages and challenges of ultrahigh‐field MRI and MRS are discussed with special emphasis on radiofrequency inhomogeneity, relaxation times, signal‐to‐noise improvem... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5433927 Tue, 01 Nov 2011 04:00:00 +0100 5433927 http://www.medworm.com/index.php?rid=5412635&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1797 This article investigates methods for the accurate and robust differentiation of metastases from glioblastomas on the basis of single‐voxel 1H MRS information. Single‐voxel 1H MR spectra from a total of 109 patients (78 glioblastomas and 31 metastases) from the multicenter, international INTERPRET database, plus a test set of 40 patients (30 glioblastomas and 10 metastases) from three different centers in the Barcelona (Spain) metropolitan area, were analyzed using a robust method for feature (spectral frequency) selection coupled with a linear‐in‐the‐parameters single‐layer perceptron classifier. For the test set, a parsimonious selection of five frequencies yielded an area under the receiver operating characteristic curve of 0.86, and an area under the convex hull of the rece... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5412635 Tue, 01 Nov 2011 04:00:00 +0100 5412635 http://www.medworm.com/index.php?rid=5402396&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1791 Previous studies have shown that skeletal muscle diffusion tensor imaging (DTI) can noninvasively probe changes in the muscle fiber architecture and microstructure in diseased and damaged muscles. However, DTI fiber reconstruction in small muscles and in muscle regions close to aponeuroses and tendons remains challenging because of partial volume effects. Increasing the spatial resolution of skeletal muscle single‐shot diffusion‐weighted echo planar imaging (DW‐EPI) can be hindered by the inherently low signal‐to‐noise ratio (SNR) of muscle DW‐EPI because of the short muscle T2 and the high sensitivity of single‐shot EPI to off‐resonance effects and T2* blurring. In this article, eddy current‐compensated diffusion‐weighted stimulated‐echo preparation is combined with ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5402396 Tue, 01 Nov 2011 04:00:00 +0100 5402396 http://www.medworm.com/index.php?rid=5391873&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1793 This study represents the first direct comparison of intravoxel incoherent motion (IVIM) metrics with IFP, with the results supporting the feasibility of using IVIM diffusion‐weighted imaging metrics as noninvasive biomarkers for tumor IFP. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5391873 Tue, 01 Nov 2011 04:00:00 +0100 5391873 http://www.medworm.com/index.php?rid=5351055&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1779 In this study, MRI/MRS were used to characterise solid tumour models obtained by subcutaneous (s.c.) or intraperitoneal (i.p.) implantation of human SKOV3.ip cells in severe combined immunodeficiency (SCID) mice. In vivo MRI/MRS, ex vivo magic‐angle‐spinning (MAS), and in vitro1H‐NMR measurements were carried out at 4.7 T, 9.4 T, and 9.4/16.5 T, respectively. MRI evaluation was performed by T1‐, T2‐, and diffusion‐weighted (DW) multislice spin‐echo imaging. The in vivo1H spectra of all tumour models showed a prominent resonance of total choline‐containing metabolites (tCho). Quantitative in vivo MRS of both i.p. and s.c. SKOV3.ip xenografts showed that the mean tCho content was in the 2.9‐4.5 mM range, with a mean PCho/tCho ratio of 0.99 ± 0.01 [23 examinatio... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5351055 Thu, 27 Oct 2011 08:43:00 +0100 5351055 http://www.medworm.com/index.php?rid=5339528&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1795 Many axons follow wave‐like undulating courses. This is a general feature of extracranial nerve segments, but is also found in some intracranial nervous tissue. The importance of axonal undulation has previously been considered, for example, in the context of biomechanics, where it has been shown that posture affects undulation properties. However, the importance of axonal undulation in the context of diffusion MR measurements has not been investigated. Using an analytical model and Monte Carlo simulations of water diffusion, this study compared undulating and straight axons in terms of diffusion propagators, diffusion‐weighted signal intensities and parameters derived from diffusion tensor imaging, such as the mean diffusivity (MD), the eigenvalues and the fractional anisotropy (FA). ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5339528 Sun, 23 Oct 2011 09:16:53 +0100 5339528 http://www.medworm.com/index.php?rid=5339529&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1796 Previous studies have provided evidence of structural and task‐related functional changes in the brains of patients with migraine without aura. Resting‐state brain activity in patients with migraine provides clues to the pathophysiology of the disease. However, few studies have focused on the resting‐state abnormalities in patients with migraine without aura. In the current study, we employed a data‐driven method, regional homogeneity (ReHo), to analyze the local features of spontaneous brain activity in patients with migraine without aura during the resting state. Twenty‐six patients with migraine without aura and 26 age‐, education‐ and gender‐matched healthy volunteers participated in this study. Compared with healthy controls, patients with migraine without aura showed ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5339529 Fri, 21 Oct 2011 04:00:00 +0100 5339529 http://www.medworm.com/index.php?rid=5326537&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1774 This study was undertaken to evaluate, dynamically and noninvasively, prostaglandin E2 (PGE2)‐enhanced migration of DCs using a 1.5 T clinical MR scanner. DC2.4 cells were labeled with superparamagnetic iron oxide (SPIO), a clinically approved MRI contrast agent. DCs were stimulated with tumor necrosis factor‐α and interferon‐γ in the presence or absence of PGE2. Before and after subcutaneous injection of labeled DCs into the hind leg footpads of mice, MRI detailing the extent of DC migration into popliteal LNs was performed using a 1.5 T clinical MR scanner. SPIO labeling did not influence the viability, endocytic activity, migratory ability and/or co‐stimulatory molecule expression of DCs. PGE2 enhanced significantly chemokine receptor‐7 expression and the migration of DCs (p... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5326537 Wed, 19 Oct 2011 06:32:53 +0100 5326537 http://www.medworm.com/index.php?rid=5277256&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1736 The aim of the study was the testing of sustained intrapericardial delivery of vascular growth factors (GFs) from alginate beads on cryoinjury size and perfusion. In domestic pigs (15–20 kg, n = 21), the left ventricular (LV) anterolateral wall of exposed hearts was cryoinjured using an aluminum rod (25 mm o.d.) cooled in liquid nitrogen. Alginate beads (d = 3.2 ± 0.2 mm), containing human recombinant basic fibroblast GF (bFGF, 50 µg) and vascular endothelial GF (VEGF, 50 µg) + heparin (50 µg) or heparin alone (Con, n = 5), were sutured to the cryoinjured epicardium (GF, n = 5; Con, n = 3 ) or pericardium (GF, n = 3; Con, n = 2), or no beads were implanted (n = 4). Four pigs were sham‐operated. Cine and T1‐weighted MRI was perfo... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5277256 Sat, 01 Oct 2011 04:00:00 +0100 5277256 http://www.medworm.com/index.php?rid=5277258&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1776 Independent component analysis (ICA) can automatically extract individual metabolite, macromolecular and lipid (MMLip) components from a series of in vivo MR spectra. The traditional feature extraction (FE)‐based ICA approach is limited, in that a large sample size is required and a combination of metabolite and MMLip components can appear in the same independent component. The alternative ICA approach, based on blind source separation (BSS), is weak when dealing with overlapping peaks. Combining the advantages of both BSS and FE methods may lead to better results. Thus, we propose an ICA approach involving a hybrid of the BSS and FE techniques for the automated decomposition of a series of MR spectra. Experiments were performed on synthesised and patient in vivo childhood brain tumo... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5277258 Fri, 30 Sep 2011 04:00:00 +0100 5277258 http://www.medworm.com/index.php?rid=5277257&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1777 Recently, both Magnetic Resonance (MR) Imaging (MRI) and Spectroscopy (MRS) have emerged as promising tools for detection of prostate cancer (CaP). However, due to the inherent dimensionality differences in MR imaging and spectral information, quantitative integration of T2 weighted MRI (T2w MRI) and MRS for improved CaP detection has been a major challenge. In this paper, we present a novel computerized decision support system called multimodal wavelet embedding representation for data combination (MaWERiC) that employs, (i) wavelet theory to extract 171 Haar wavelet features from MRS and 54 Gabor features from T2w MRI, (ii) dimensionality reduction to individually project wavelet features from MRS and T2w MRI into a common reduced Eigen vector space, and (iii), a random forest classifier... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5277257 Fri, 30 Sep 2011 04:00:00 +0100 5277257 http://www.medworm.com/index.php?rid=5253882&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1790 1H MRSI of the prostate reveals relative metabolite levels that vary according to the presence or absence of tumour, providing a sensitive method for the identification of patients with cancer. Current interpretations of prostate data rely on quantification algorithms that fit model metabolite resonances to individual voxel spectra and calculate relative levels of metabolites, such as choline, creatine, citrate and polyamines. Statistical pattern recognition techniques can potentially improve the detection of prostate cancer, but these analyses are hampered by artefacts and sources of noise in the data, such as variations in phase and frequency of resonances. Phase and frequency variations may arise as a result of spatial field gradients or local physiological conditions affecting the freq... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5253882 Mon, 26 Sep 2011 12:58:12 +0100 5253882 http://www.medworm.com/index.php?rid=5253883&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1781 In conclusion, our method seems to be a powerful tool to non‐invasively perform accurate in vivo quantitative measurements in the liver and spleen using 19 F MRI. Copyright © 2011 John Wiley & Sons, Ltd.High‐sensitivity perfluorooctyl bromide (PFOB) imaging was performed for quantitative measurements in the mouse liver and spleen after intravenous (i.v.) injection of PFOB emulsions. Our method proved to be efficient in performing accurate oxygenation maps in both organs shortly after injection and with a single dose of emulsion. Furthermore, dynamic biodistribution could be achieved just after injection, and we were able to point out stealth differences between emulsions incorporating increasing quantities of polyethylene glycol (PEG). (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5253883 Mon, 26 Sep 2011 04:00:00 +0100 5253883 http://www.medworm.com/index.php?rid=5253886&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1784 In this study, we propose an algorithm for the automatic detection of AIF from mouse DCE‐MR images using Kendall's coefficient of concordance. The proposed method was tested with computer simulations and then applied to tumor‐bearing mice (n = 8). Results from computer simulations showed that the proposed algorithm is capable of categorizing simulated AIF signals according to their noise levels. We found that the resulting pharmacokinetic parameters computed from our method were comparable with those from the manual determination of AIF, with acceptable differences in Ktrans (5.14 ± 3.60%), ve (6.02 ± 3.22%), vp (5.10 ± 7.05%) and kep (5.38 ± 4.72%). The results of the current study suggest the usefulness of an automatically defined AIF using Kendall's coefficie... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5253886 Fri, 23 Sep 2011 04:00:00 +0100 5253886 http://www.medworm.com/index.php?rid=5253885&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1782 The purpose of this study was to evaluate whether single‐voxel 1H MRS could add useful information to conventional MRI in the preoperative characterisation of the type and grade of brain tumours. MRI and MRS examinations from a prospective cohort of 40 consecutive patients were analysed double blind by radiologists and spectroscopists before the histological diagnosis was known. The spectroscopists had only the MR spectra, whereas the radiologists had both the MR images and basic clinical details (age, sex and presenting symptoms). Then, the radiologists and spectroscopists exchanged their predictions and re‐evaluated their initial opinions, taking into account the new evidence. Spectroscopists used four different systems of analysis for 1H MRS data, and the efficacy of each of these m... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5253885 Fri, 23 Sep 2011 04:00:00 +0100 5253885 http://www.medworm.com/index.php?rid=5253884&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1785 The assessment of metabolites by 1H MRS can provide information regarding glioma growth, and may be able to distinguish between different glioma models. Rat C6, 9 L/LacZ, F98 and RG2, and mouse GL261, cells were intracerebrally implanted into the respective rodents, and human U87 MG cells were implanted into athymic rats. Ethyl‐nitrosourea induction was also used. Glioma metabolites [e.g. total choline (tCho), total creatine (tCr), N‐acetylaspartate (NAA), lactate (Lac), glutamine (Gln), glutamate (Glu), aspartate (Asp), guanosine (Gua), mobile lipids and macromolecules (MMs)] were assessed from 1H MRS using point‐resolved spectroscopy (PRESS) [TE = 24 ms; TR = 2500 ms; variable pulse power and optimized relaxation delay (VAPOR) water suppression; 27‐μL and 8‐μL v... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5253884 Fri, 23 Sep 2011 04:00:00 +0100 5253884 http://www.medworm.com/index.php?rid=5241714&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1786 In conclusion, phase contrast MRI is believed to be sensitive to vascular remodeling in co‐opting brain tumor metastases independent of sprouting angiogenesis, and may therefore aid in preclinical studies of angiogenic‐independent tumors or in the monitoring of continued tumor growth following anti‐angiogenic therapy. Published 2011. This article is a US Government work and is in the public domain in the USA.Phase contrast MRI is an intrinsic contrast exquisitely sensitive to deoxyhemoglobin. In an experimental model of metastatic breast cancer in the brain, phase images were more sensitive than magnitude images to vascular abnormalities in tumors. Serial phase contrast changes demonstrated the early growth of micrometastatic breast cancer in the brain, suggestive of vascular remodel... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5241714 Thu, 22 Sep 2011 20:54:12 +0100 5241714 http://www.medworm.com/index.php?rid=5241716&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1789 The expression of cyclooxygenase‐2 (COX‐2) is observed in approximately 40% of breast cancers. A major product of the COX‐2‐catalyzed reaction, prostaglandin E2, is an inflammatory mediator that participates in several biological processes, and influences invasion, vascularization and metastasis. Using noninvasive MRI and MRS, we determined the effect of COX‐2 downregulation on the metabolism and invasion of intact poorly differentiated MDA‐MB‐231 human breast cancer cells stably expressing COX‐2 short hairpin RNA. Dynamic tracking of invasion, extracellular matrix degradation and metabolism was performed with an MRI‐ and MRS‐compatible cell perfusion assay under controlled conditions of pH, temperature and oxygenation over the course of 48 h. COX‐2‐silenced cells... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5241716 Thu, 22 Sep 2011 04:00:00 +0100 5241716 http://www.medworm.com/index.php?rid=5241715&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1783 The increased blood oxygenation level‐dependent contrast‐to‐noise ratio at ultrahigh field (7 T) has been exploited in a comparison of the spatial location and strength of activation in high‐resolution (1.5 mm isotropic) gradient echo (GE) and spin echo (SE), echo planar imaging data acquired during the execution of a simple motor task in five subjects. SE data were acquired at six echo times from 30 to 55 ms. Excellent fat suppression was achieved in the SE echo planar images using slice‐selective gradient reversal. Threshold‐free cluster enhancement was used to define regions of interest (ROIs) containing voxels showing significant stimulus‐locked signal changes from the GE and average SE data. These were used to compare the signal changes and spatial locations of act... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5241715 Thu, 22 Sep 2011 04:00:00 +0100 5241715 http://www.medworm.com/index.php?rid=5229550&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1787 (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5229550 Mon, 19 Sep 2011 10:37:58 +0100 5229550 http://www.medworm.com/index.php?rid=5165375&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1778 The purpose of the present study was to use magnetic resonance imaging (MRI) as a tool for monitoring transplant‐mediated repair of the adult rat visual pathway. We labelled rat olfactory ensheathing cells (OECs) using micron‐sized particles of iron oxide (MPIO) and transplanted them by: i) intravitreal injection (ivit) and ii) intra‐optic nerve (ON) injection (iON) in adult rats with ON crush (ONC) injury. We applied T2‐weighted MRI and manganese‐enhanced MRI (MEMRI) to visualise transplanted cells and ON axons at specific times after injury and cell engraftment. Our findings demonstrate that ivit MPIO‐labelled OECs are unequivocally detected by T2‐weighted MRI in vivo and that the T1‐weighted 3D FLASH sequence applied for MEMRI facilitates simultaneous visualisation of Mn... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5165375 Thu, 25 Aug 2011 23:00:00 +0100 5165375 http://www.medworm.com/index.php?rid=5165374&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1773 This study demonstrates that oral manganese is a viable method for the imaging of nerves associated with increased nociceptive activity. Copyright © 2011 John Wiley & Sons, Ltd.Animals with neuropathic pain [spared nerve injury (SNI) model] were given increasing amounts of oral manganese chloride and analyzed for preferential MRI enhancement of peripheral nerves associated with nociception. Compared with control rats, SNI animals demonstrated increased MR signal‐to‐background on T1‐weighted fast spin echo that correlated strongly with spectrometry measurements of nerve manganese concentration. This study sets a precedent for oral manganese in the imaging of nociceptive activity. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5165374 Thu, 25 Aug 2011 23:00:00 +0100 5165374 http://www.medworm.com/index.php?rid=5150057&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1761 In this study, the various aspects of direct 13C and indirect 1H‐[13C] NMR are reviewed with the aim of providing a practical guide. Copyright © 2011 John Wiley & Sons, Ltd.(A) 1H and (B) 1H‐[13C] NMR spectra acquired from rat brain at 9.4 T in the presence of adiabatic broadband decoupling. The spectra are acquired circa 90 min following the start of [1,6‐13C2]‐glucose infusion. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5150057 Mon, 22 Aug 2011 23:00:00 +0100 5150057 http://www.medworm.com/index.php?rid=5150056&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1764 Activation of the PI3K/Akt pathway is associated with the development of numerous human cancers. As a result, many emerging therapies target this pathway. Previous studies have shown that targeting the PI3K/Akt pathway at the level of PI3K is associated with a drop in phosphocholine (PCho) and a reduction in hyperpolarized lactate production. However, the consequences of targeting downstream of PI3K at the level of Akt have not been investigated. Perifosine is an anticancer alkylphospholipid used in clinical trials. It acts by inhibiting phosphorylation of Akt and has been shown to inhibit CTP‐phosphocholine cytidyltransferase (CT). The goal of this study was to identify the MRS‐detectable metabolic consequences of treatment with perifosine in MCF‐7 breast cancer cells. We found that... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5150056 Mon, 22 Aug 2011 23:00:00 +0100 5150056 http://www.medworm.com/index.php?rid=5150059&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1768 In this study, sodium T1, and relaxation maps were measured in vivo at 7 T on 8 healthy volunteers and in 4 different regions of the cartilage in the knee joint. The patellar, femoro‐tibial medial, lateral, and femoral condyle cartilage have an average T1 ∼ 20 ms, but different (from 0.5 ms to 1.4 ms) and (from 11.4 ms to 14.8 ms). Statistically significant differences in T1, and were observed between the different regions in cartilage (p ≪ 10− 5). Statistical differences in T1 were also observed between male and female data (p ≪ 10− 5). These relaxation times measurements can further be applied as correction factors for sodium concentration maps in vivo and can also be useful as complementary information to quantitative sodium MRI in the quest for det... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5150059 Thu, 18 Aug 2011 23:00:00 +0100 5150059 http://www.medworm.com/index.php?rid=5150058&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1775 In this study, a retrospective analysis of 140 volumetric MRSI datasets was carried out to investigate the value of including BMI in the subject selection relative to age and gender. The findings replicate earlier reports of strong associations of N‐acetylaspartate, creatine, choline and gray matter with age and gender, with additional observations of slightly increased spectral linewidth with age and in female relative to male subjects. Associations of metabolite levels, linewidth and gray matter volume with BMI were also observed, although only in some regions. Using voxel‐based analyses, it was also observed that the patterns of the relative changes of metabolites with BMI matched those of linewidth with BMI or weight, and that residual magnetic field inhomogeneity and measures of s... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5150058 Thu, 18 Aug 2011 23:00:00 +0100 5150058 http://www.medworm.com/index.php?rid=5150061&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1770 The compartment‐specific lipid changes in femoral–tibial bone of healthy controls and mild osteoarthritis (OA) patients were quantified at 3.0 T. Healthy volunteers [Kellgren–Lawrence (KL) grade = 0; n = 15, 4 females, 11 males, mean age 39 ± 16 years, age range = 24–78 years] and mild OA patients (KL = 1, 2; n = 26, 12 females, 14 males, mean age 61 ± 14 years, age range = 27–80 years) were scanned on a 3 T scanner. Clinical proton density (PD)‐weighted fast spin echo (FSE) images in the sagittal (without fat‐saturation), axial and coronal (fat‐saturation) planes were acquired for cartilage Whole‐Organ MR Imaging Score (WORMS) grading. A voxel of 10 × 10 × 10 mm3 was positioned in the medial and lateral compartmen... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5150061 Wed, 17 Aug 2011 23:00:00 +0100 5150061 http://www.medworm.com/index.php?rid=5150060&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1769 Osteoarthritis (OA) is a degenerative disease of the joints and results in changes in the biochemical composition of cartilage. Previous studies have been undertaken that have used high‐resolution NMR spectroscopy to study the biochemical composition of porcine, canine and bovine cartilage. In the present study, high‐resolution magical angle spinning (HR‐MAS) NMR spectroscopy at 11.7 T has been used to characterize metabolites and detect differences in the spectral signature of human knee articular cartilage from non‐OA healthy cadaver knees and samples acquired from severe OA patients at the time of total knee replacement surgery. A statistically significant difference in the alanine (1.47 p.p.m.), N‐acetyl (2.04 p.p.m.), choline (3.25 p.p.m.) and glycine (3.55 p.p.m.)... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5150060 Wed, 17 Aug 2011 23:00:00 +0100 5150060 http://www.medworm.com/index.php?rid=5127934&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1757 A detailed description of the construction and use of a device for hyperpolarization of select contrast agents is presented. The device is based on molecular incorporation of the spin‐order inherent to parahydrogen, followed by order transfer to a metastable heteronuclear alignment. Design considerations and experimental results relating to catalyst/solvent choice and handling, solvent heating, efficient gas entrainment and spin‐order transfer are described. The resulting degree of hyperpolarization is shown to be substantial, ranging from a few to over 50%, depending on the choice of target molecule. Finally, the use of the hyperpolarized agent is demonstrated in a series of in vivo images. Copyright © 2011 John Wiley & Sons, Ltd.A detailed description of the construction and use... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5127934 Sun, 14 Aug 2011 23:00:00 +0100 5127934 http://www.medworm.com/index.php?rid=5127933&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1767 Proton T2 relaxation times of metabolites in the human brain were measured using point resolved spectroscopy at 3T in vivo. Four echo times (54, 112, 246 and 374 ms) were selected from numerical and phantom analyses for effective detection of the glutamate multiplet at ~ 2.35 ppm. In vivo data were obtained from medial and left occipital cortices of five healthy volunteers. The cortices contained predominantly gray and white matter, respectively. Spectra were analyzed with LCModel software using volume‐localized calculated spectra of brain metabolites. The estimate of the signal strength vs. TE was fitted to a monoexponential function for estimation of apparent T2 (T2†). T2† was estimated to be similar between the brain regions for creatine, choline, glutamate and myo‐inosi... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5127933 Sun, 14 Aug 2011 23:00:00 +0100 5127933 http://www.medworm.com/index.php?rid=5112889&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1762 ConclusionsOur results demonstrate that HR MAS MR metabolic profiles consisting of important metabolic characteristics of breast cancer tumors could potentially assist the classification and prediction of long‐term survival in locally advanced breast cancer patients, in addition to being used as an adjunct for evaluation of treatment response to NAC. Copyright © 2011 John Wiley & Sons, Ltd.HR‐MAS spectra of pre (n = 26) and posttreatment (n = 22) breast cancer biopsies were successfully used to classify and predict long‐term breast cancer survival in patients. Different pre treatment MR metabolic profiles characterized by higher levels of tCho and lower levels of lactate were observed for patients with long‐term survival (≥5 years) compared to patients who died of ca... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5112889 Sun, 07 Aug 2011 23:00:00 +0100 5112889 http://www.medworm.com/index.php?rid=5112888&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1752 Hepatocellular carcinoma (HCC) and liver metastases are an increasing problem worldwide. Non‐invasive methods for the early detection of HCC and understanding of the tumor growth mechanisms are highly desirable. Both the diffusion‐weighted 1H (DWI) and 23Na MRI reflect alterations in tissue compartment volumes in tumors, as well as physiological and metabolic transformation in cells. Effects of untreated growth on apparent diffusion coefficient of water (ADC), single quantum (SQ) and triple quantum‐filtered (TQF) 23Na MRI were compared in intrahepatically and subcutaneously implanted HCCs in rats. Animals were examined weekly for 4 weeks after injection of N1S1 cells. ADC of intrahepatic HCC was 1.5‐times higher compared to the nearby liver tissue, and with growth, the ADC did no... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5112888 Sun, 07 Aug 2011 23:00:00 +0100 5112888 http://www.medworm.com/index.php?rid=5090623&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1742 pH is a fundamental physiological parameter that is tightly controlled by endogenous buffers. The acid–base balance is altered in many disease states, such as inflammation, ischemia and cancer. Despite the importance of pH, there are currently no routine methods for imaging the spatial distribution of pH in humans. The enormous gain in sensitivity afforded by dynamic nuclear polarization (DNP) has provided a novel way in which to image tissue pH using MR, which has the potential to be translated into the clinic. This review explores the advantages and disadvantages of current pH imaging techniques and how they compare with DNP‐based approaches for the measurement and imaging of pH with hyperpolarized 13C. Intravenous injection of hyperpolarized 13C‐labeled bicarbonate results in the ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5090623 Tue, 02 Aug 2011 23:00:00 +0100 5090623 http://www.medworm.com/index.php?rid=5187039&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1772 In the last 25 years, 13 C MRS has been established as the only noninvasive method for the measurement of glutamate neurotransmission and cell‐specific neuroenergetics. Although technically and experimentally challenging, 13 C MRS has already provided important new information on the relationship between neuroenergetics and neuronal function, the energy cost of brain function, the high neuronal activity in the resting brain state and how neuroenergetics and neurotransmitter cycling are altered in neurological and psychiatric disease. In this article, the current state of 13 C MRS as it is applied to the study of neuroenergetics and neurotransmitter cycling in humans is reviewed. The focus is predominantly on recent findings in humans regarding metabolic pathways, applications to ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5187039 Sun, 31 Jul 2011 23:00:00 +0100 5187039 http://www.medworm.com/index.php?rid=5165373&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1712 Transgenic models of human disease can be used to understand pathology and to discover biomarkers of disease presence, progression and response to therapy. Here we report a study of longitudinal metabolic differences between TASTPM transgenic Alzheimer's disease (AD) mice and their wild type counterparts using 1H magnetic resonance spectroscopy (MRS) to look for potential biomarkers for use in AD research and drug discovery. Chloroform methanol extractions were performed on the brains of mice aged between 3 and 18 months. 1H MR spectra were recorded from the aqueous fractions. Absolute metabolite concentrations, determined from resonance integrals relative to an internal standard, were analysed by 2‐way ANOVA (genotype x age). Significant effects of age alone were identified for creati... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5165373 Sun, 31 Jul 2011 23:00:00 +0100 5165373 http://www.medworm.com/index.php?rid=5150055&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1765 This study illustrates the need for multimodal imaging in assessing tumor response to treatment to compensate for individual limitations. Copyright © 2011 John Wiley & Sons, Ltd.Non‐invasive assessment of early tumor response to chemotherapy by different magnetic resonance protocols: diffusion‐weighted MRI; choline measurement by 1H MRS and contrast enhanced MRI using ultrasmall iron oxide nanoparticles targeted at phosphatidylserine. This work illustrates the need for multimodal imaging in assessing tumor response to treatment to compensate for individual limitations.The figure shows ADCw maps of tumor‐bearing mice before and 24 h after injection of different cytotoxic treatments. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5150055 Sun, 31 Jul 2011 23:00:00 +0100 5150055 http://www.medworm.com/index.php?rid=5134615&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1771 Online MR temperature monitoring during radiofrequency (RF) ablation of cardiac arrhythmias may improve the efficacy and safety of the treatment. MR thermometry at 1.5 T using the proton resonance frequency (PRF) method was assessed in 10 healthy volunteers under normal breathing conditions, using a multi‐slice, ECG‐gated, echo planar imaging (EPI) sequence in combination with slice tracking. Temperature images were post‐processed to remove residual motion‐related artifacts. Using an MR‐compatible steerable catheter and electromagnetic noise filter, RF ablation was performed in the ventricles of two sheep in vivo. The standard deviation of the temperature evolution in time (TSD) was computed. Temperature mapping of the left ventricle was achieved at an update rate of approximat... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5134615 Sun, 31 Jul 2011 23:00:00 +0100 5134615 http://www.medworm.com/index.php?rid=5127932&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1732 Evaluation of the skin phenotype in osteogenesis imperfecta (OI) typically involves biochemical measurements, such as histologic or biochemical assessment of the collagen produced from biopsy‐derived dermal fibroblasts. As an alternative, the current study utilized non‐invasive magnetic resonance imaging (MRI) microscopy and optical spectroscopy to define biophysical characteristics of skin in an animal model of OI. MRI of skin harvested from control, homozygous oim/oim and heterozygous oim/+ mice demonstrated several differences in anatomic and biophysical properties. Fourier transform infrared imaging spectroscopy (FT‐IRIS) was used to interpret observed MRI signal characteristics in terms of chemical composition. Differences between wild‐type and OI mouse skin included the appea... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5127932 Sun, 31 Jul 2011 23:00:00 +0100 5127932 http://www.medworm.com/index.php?rid=5121895&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1766 In hyperpolarised 3He lung MRI with constant flip angles, the transverse magnetisation decays with each RF excitation imposing a k‐space filter on the acquired data. For radial data acquired in an angularly‐sequential order, this filter causes streaking, angular shading and loss of spatial resolution in the images. The main aim of this work was to reduce the effects of the RF depletion k‐space filter in radial acquisitions. Two approaches are presented; (i) retrospective deconvolution of the k‐space filter for sequentially‐acquired data and (ii) golden angle acquisition order. Radial trajectories sample the centre of k‐space with every projection, thereby self‐tracking signal decay. The inverse of the signal decay function was used to retrospectively deconvolve RF depolarisat... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5121895 Sun, 31 Jul 2011 23:00:00 +0100 5121895 http://www.medworm.com/index.php?rid=5112887&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1726 We examined pyruvate doses of 0.1–0.4 mmol/kg (body mass) in male Wistar rats by acquiring slice‐selective free induction decay signals in slices dominated by heart, liver and kidney tissue. Dose effects were noted in all cases, except for alanine in the cardiac slice below the dose of 0.2 mmol/kg. Our results indicate unlimited cellular uptake of pyruvate up to this dose and limited enzymatic activity of lactate dehydrogenase. In the cardiac slice above 0.2 mmol/kg and in liver and kidney slices, reflect limited cellular uptake or enzymatic activity, or a combination of both effects. The results indicate that the dose of pyruvate must be recognized as an important determinant for metabolic tissue kinetics, and saturation effects must be taken into account for the quantitative in... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5112887 Sun, 31 Jul 2011 23:00:00 +0100 5112887 http://www.medworm.com/index.php?rid=5072871&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1763 In the last decade, evidence has emerged indicating that the growth of a vast majority of tumors including gliomas is sustained by a subpopulation of cancer cells with stem cell properties called cancer initiating cells. These cells are able to initiate and propagate tumors and constitute only a fraction of all tumor cells. In the present study, we showed that intracerebral injection of cultured glioma‐initiating cells into nude mice produced fast growing tumors showing necrosis and gadolinium enhancement in MR images, whereas gliomas produced by injecting freshly purified glioma‐initiating cells grew slowly and showed no necrosis and very little gadolinium enhancement. Using proton localized spectroscopy at 14.1 Tesla, decreasing trends of N‐acetylaspartate, glutamate and glucose co... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5072871 Tue, 26 Jul 2011 23:00:00 +0100 5072871 http://www.medworm.com/index.php?rid=5072870&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1754 At the high field strength of 7 T, in vivo spectra of the human brain with exceptional spectral quality sufficient to quantify 16 metabolites have been obtained previously only in the occipital lobe. However, neurochemical abnormalities associated with many brain disorders are expected to occur in brain structures other than the occipital lobe. The purpose of the present study was to obtain high‐quality spectra from various brain regions at 7 T and to quantify the concentrations of different metabolites. To obtain concentrations of metabolites within four different regions of the brain, such as the occipital lobe, motor cortex, basal ganglia and cerebellum, the T2 relaxation times of the singlets and J‐coupled metabolites in these regions were measured for the first time at 7 T. ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5072870 Tue, 26 Jul 2011 23:00:00 +0100 5072870 http://www.medworm.com/index.php?rid=5072869&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1759 This study showed for the first time that in a mouse model of coronary occlusion‐reperfusion, Mn2+ wash‐in kinetics are different at 24 h after surgery (acute infarction) than at eight days after surgery (chronic infarction). A fast but transient entry of Mn2+ into the acute infarct area led to a double contrast between infarct and remote areas, whereas entry of Mn2+ into the chronic infarct area remained reduced compared to remote regions during both wash‐in and washout phases. The main hypothesis is that extracellular space is largely enhanced in acute infarction due to cell membrane rupture and interstitial edema, whereas scar tissue is densely composed of collagen fibers that reduce the distribution volume of free Mn2+ ions. In addition to its ability to accurately depict the i... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5072869 Tue, 26 Jul 2011 23:00:00 +0100 5072869 http://www.medworm.com/index.php?rid=5072868&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1744 The potential of MRI to provide quantitative measures of neuromuscular pathology for use in therapeutic trials is being increasingly recognised. Magnetisation transfer (MT) imaging shows particular promise in this context, being sensitive to pathological changes, particularly in skeletal muscle, where measurements correlate with clinically measured muscle strength. Radiofrequency (RF) transmit field (B1) inhomogeneities can be particularly problematic in measurements of the MT ratio (MTR) and may obscure genuine muscle MTR changes caused by disease. In this work, we evaluate, for muscle imaging applications, a scheme previously proposed for the correction of RF inhomogeneity artefacts in cerebral MTR maps using B1 information acquired in the same session. We demonstrate the theoretical app... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5072868 Tue, 26 Jul 2011 23:00:00 +0100 5072868 http://www.medworm.com/index.php?rid=5072867&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1753 This study presents a novel method for the direct classification of 1H single‐voxel MR brain tumour spectra using the widespread analysis tool LCModel. LCModel is designed to estimate individual metabolite proportions by fitting a linear combination of in vitro metabolite spectra to an in vivo MR spectrum. In this study, it is used to fit representations of complete tumour spectra and to perform a classification according to the highest estimated tissue proportion. Each tumour type is represented by two spectra, a mean component and a variability term, as calculated using a principal component analysis of a training dataset. In the same manner, a mean component and a variability term for normal white matter are also added into the analysis to allow a mixed tissue approach. An unbiase... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5072867 Tue, 26 Jul 2011 23:00:00 +0100 5072867 http://www.medworm.com/index.php?rid=5059165&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1710 In imaging of human lungs with hyperpolarised noble gases, measurements of apparent diffusion coefficient (ADC) and relaxation time provide valuable information for the assessment of lung microstructure. In this work, a sequence was developed for interleaved acquisition of ventilation images, ADC, T2* and flip angle maps in a single scan from the human lungs with a single dose of inhaled 3He at 3 T. Spatially registered ventilation images with parametric maps were obtained. The total acquisition time was reduced by random undersampling of the k‐space and reconstruction using compressed sensing (CS). The gain in speed was used for an increase in spatial resolution. Mean ADC values from the fully sampled and undersampled CS data exhibit no statistically significant difference in a given ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5059165 Sun, 24 Jul 2011 23:00:00 +0100 5059165 http://www.medworm.com/index.php?rid=5059164&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1758 This study investigated the factors that affect diagnostic accuracy in the use of MRS for the characterization of musculoskeletal neoplasms. During a 7‐year period, 210 consecutive patients with musculoskeletal lesions larger than 1.5 cm in diameter were examined. MRS of a single‐voxel point‐resolved spectroscopy sequence with TE = 135 ms was undertaken using a 1.5‐T scanner. Lesions with a choline signal‐to‐noise ratio larger than 3.0 were considered to be malignant tumors. The diagnostic accuracy was calculated for all lesions and for subgroups on the basis of lesion type (bone and soft tissue), lesion composition (mixed and solid nonsclerotic), lesion size (≤4, >4–10 and >10 cm), MR scanner (MR scanner 1 and 2) and selected voxel size (≤3, >3–8 and... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5059164 Sun, 24 Jul 2011 23:00:00 +0100 5059164 http://www.medworm.com/index.php?rid=5059163&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1741 In this study, it is shown that the chemical exchange saturation transfer (CEST) method for hydroxyl protons can be used to detect changes in glycosaminoglycan (GAG) concentration in the intervertebral disc. The method, termed gagCEST, was demonstrated ex vivo by correlating the CEST effect with the fixed charge density (FCD) of the nucleus pulposus (NP), as well as by correlating tissue CEST images with their corresponding 23Na images. Incubation of five NP samples with trypsin produced samples with varying GAG content (n = 19). A good correlation was found between the –OH CEST effect and FCD, as well as with the N‐acetyl signal amplitude. gagCEST images in vitro further illustrated the amount of detail obtainable from this contrast mechanism when compared with conventional im... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5059163 Sun, 24 Jul 2011 23:00:00 +0100 5059163 http://www.medworm.com/index.php?rid=5043833&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1708 We report the first comparison of cardiovascular magnetic resonance imaging (CMR) at 1.5 T, 3 T and 7 T field strengths using steady state free precession (SSFP) and fast low angle shot (FLASH) cine sequences. Cardiac volumes and mass measurements were assessed for feasibility, reproducibility and validity at each given field strength using FLASH and SSFP sequences. Ten healthy volunteers underwent retrospectively electrocardiogram (ECG) gated CMR at 1.5 T, 3 T and 7 T using FLASH and SSFP sequences. B1 and B0 shimming and frequency scouts were used to optimise image quality. Cardiac volume and mass measurements were not significantly affected by field strength when using the same imaging sequence (P > 0.05 for all parameters at 1.5 T, 3 T and 7 T). SSFP imaging re... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5043833 Mon, 18 Jul 2011 23:00:00 +0100 5043833 http://www.medworm.com/index.php?rid=5043832&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1749 13C MR spectroscopy studies performed on hearts ex vivo and in vivo following perfusion of prepolarized [1‐13C]pyruvate have shown that changes in pyruvate dehydrogenase (PDH) flux may be monitored non‐invasively. However, to allow investigation of Krebs cycle metabolism, the 13C label must be placed on the C2 position of pyruvate. Thus, the utilization of either C1 or C2 labeled prepolarized pyruvate as a tracer can only afford a partial view of cardiac pyruvate metabolism in health and disease. If the prepolarized pyruvate molecules were labeled at both C1 and C2 positions, then it would be possible to observe the downstream metabolites that were the results of both PDH flux (13CO2 and H13CO3‐) and Krebs cycle flux ([5‐13C]glutamate) with a single dose of the agent. Cardiac pH co... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5043832 Mon, 18 Jul 2011 23:00:00 +0100 5043832 http://www.medworm.com/index.php?rid=5043831&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1735 The purpose was to assess effects of intrapericardially deposited adipose‐derived stem cells (ADSC) as a source of angiogenic factors on cryoinjury infarction. To enhance this effect and reduce incorporation of ADSC into tissue, the cells were immobilized in agarose gel patches transplanted onto cryoinjured epicardium. In domestic pigs (15–20 kg) the left ventricular (LV) anterior wall of exposed hearts was cryoinjured using aluminum rod (Φ=25 mm) cooled in liquid nitrogen. Sterilized circular patches made of agarose gel were placed in a nylon bag and sutured to cryoinjured epicardium. In 4 pigs, the patches contained 650,000 human ADSCs; in control animals patches were cell‐free (n,=,2) or no patches were implanted (n,=,2). Cine and T1‐weighted MRI was performed in vivo weekl... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5043831 Mon, 18 Jul 2011 23:00:00 +0100 5043831 http://www.medworm.com/index.php?rid=5032790&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1740 After ischemic stroke, the ischemic damage to brain tissue evolves over time and with an uneven spatial distribution. Early irreversible changes occur in the ischemic core, whereas, in the penumbra, which receives more collateral blood flow, the damage is more mild and delayed. A better characterization of the penumbra, irreversibly damaged and healthy tissues is needed to understand the mechanisms involved in tissue death. MRSI is a powerful tool for this task if the scan time can be decreased whilst maintaining high sensitivity. Therefore, we made improvements to a 1H MRSI protocol to study middle cerebral artery occlusion in mice. The spatial distribution of changes in the neurochemical profile was investigated, with an effective spatial resolution of 1.4 μL, applying the protocol on... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5032790 Thu, 14 Jul 2011 23:00:00 +0100 5032790 http://www.medworm.com/index.php?rid=5032789&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1727 In this study, the feasibility of acquiring and quantifying short‐echo (TE = 8 ms), single‐voxel 1H MR spectra from multiple brain regions was demonstrated by utilizing a 16‐channel transceiver array coil with 16 independent transmit channels, allowing local transmit B1 (B1+) shimming. Spectra were acquired from volumes of interest of 1–8 mL in brain regions that are of interest for various neurological disorders: frontal white matter, posterior cingulate, putamen, substantia nigra, pons and cerebellar vermis. Local B1+ shimming substantially increased the transmit efficiency, especially in the peripheral and ventral brain regions. By optimizing a STEAM sequence for utilization with a 16‐channel coil, artifact‐free spectra were acquired with a small chemical shift displ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5032789 Thu, 14 Jul 2011 23:00:00 +0100 5032789 http://www.medworm.com/index.php?rid=5032793&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1733 A fast method has been established for the precise measurement and quantification of the dynamics of hyperpolarized (HP) xenon‐129 (129Xe) in the mouse brain. The key technique is based on repeatedly applying radio frequency (RF) pulses and measuring the decrease of HP 129Xe magnetization after the brain Xe concentration has reached a steady state due to continuous HP 129Xe ventilation. The signal decrease of the 129Xe nuclear magnetic resonance (NMR) signal was well described by a simple theoretical model. The technique made it possible to rapidly evaluate the rate constant α, which is composed of cerebral blood flow (CBF), the partition coefficient of Xe between the tissue and blood (λi), and the longitudinal relaxation time (T1i) of HP 129Xe in the brain tissue, without any effect o... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5032793 Wed, 13 Jul 2011 23:00:00 +0100 5032793 http://www.medworm.com/index.php?rid=5032792&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1711 In this study, the method is applied to human brain tissue in vivo, using whole‐body gradients. Data are reported for the corticospinal tracts. The characteristics of the observed signal difference between parallel and antiparallel gradient orientations are consistent with both analytical and numerical predictions. As an estimate of pore size, the resulting mean squared radius of gyration of the pores amounts to approximately 4 µm2. An analysis that accounts for the finite values of gradient pulse duration and diffusion time yields a volume contribution‐weighted mean pore diameter of 13 μm if a cylindrical pore shape is assumed. The results demonstrate that the technique can be applied in vivo. Copyright © 2011 John Wiley & Sons, Ltd.In restricted diffusion, the MR signal wi... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5032792 Wed, 13 Jul 2011 23:00:00 +0100 5032792 http://www.medworm.com/index.php?rid=5032791&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1729 Transverse relaxation time (T2) is a basic but very informative MRI parameter, widely used in imaging to examine a host of diseases, including multiple sclerosis, stroke, and tumor. However, short repetition time (TR) is often used to minimize scan time, which may introduce non‐negligible errors in T2 measurement. Specifically, due to the use of refocusing pulse, the steady state magnetization depends not only on TR but also on the TE. Hence, if the TE dependence is not properly accounted for, it may be mistaken as T2‐induced signal attenuation, leading to non‐negligible T2 underestimation. Our study proposed a fast radio‐frequency enforced steady state (FRESS) spin echo (SE) MRI sequence, which saturates the magnetization after the echo and ensures a TE‐independent steady state.... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5032791 Wed, 13 Jul 2011 23:00:00 +0100 5032791 http://www.medworm.com/index.php?rid=5013339&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1748 We describe a novel magnetic resonance imaging technique to directly assess the metabolic integrity of penumbral tissue following stroke. For ischemically stressed tissue to be salvageable, it has to be capable of recovering aerobic metabolism (in place of anaerobic metabolism) on reperfusion. We probed ischemic brain tissue by altering the rate of oxygen delivery using a challenge of 100% oxygen ventilation. Any change from anaerobic to aerobic metabolism should alter the rate of lactate production and hence, levels of tissue lactate. Stroke was induced by permanent middle cerebral artery occlusion in rats. In Series 1 (n = 6), changes in tissue lactate during and following 100% oxygen challenge were monitored using 1H magnetic resonance spectroscopy (MRS). Diffusion weighted imaging ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5013339 Mon, 11 Jul 2011 23:00:00 +0100 5013339 http://www.medworm.com/index.php?rid=5013338&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1734 Vessel size index (VSI), a parameter related to the distribution of vessel diameters, may be estimated using two MRI approaches: (i) dynamic susceptibility contrast (DSC) MRI following the injection of a bolus of Gd‐chelate. This technique is routinely applied in the clinic to assess intracranial tissue perfusion in patients; (ii) steady‐state susceptibility contrast with USPIO contrast agents, which is considered here as the standard method. Such agents are not available for human yet and the steady‐state approach is currently limited to animal studies. The aim is to compare VSI estimates obtained with these two approaches on rats bearing C6 glioma (n = 7). In a first session, VSI was estimated from two consecutive injections of Gd‐Chelate (Gd1 and Gd2). In a second session (4... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5013338 Mon, 11 Jul 2011 23:00:00 +0100 5013338 http://www.medworm.com/index.php?rid=5013337&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1746 PARACEST (PARAmagnetic Chemical Exchange Saturation Transfer) agents offer the ability to generate “contrast on demand”, negating the need to image before contrast agent injection. Perfluorocarbon (PFC) nanoparticles can deliver very large payloads of PARACEST agents, lowering the effective detection limit for molecular imaging of sparse biomarkers. Also, the PFC core provides a quantitative 19F signal for measuring particle binding with high signal intensity and no background signal. 19F quantization coupled with mathematical modeling of the PARACEST signal showed that incorporating PARACEST chelates onto the nanoparticle surface reduces the bound water lifetime and diminishes the available contrast to noise ratio compared to the parent small molecule PARACEST chelate. PARACEST nanopa... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5013337 Mon, 11 Jul 2011 23:00:00 +0100 5013337 http://www.medworm.com/index.php?rid=5013336&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1743 Dynamic nuclear polarization and dissolution offer the exciting possibility of imaging biochemical reactions in vivo, including some of the key enzymatic reactions involved in cellular metabolism. The development of new pulse sequence strategies has been motivated by demanding applications, such as the imaging of hyperpolarized metabolite distributions in the heart. In this article, the key considerations surrounding the application of spectral–spatial imaging pulse sequences for hyperpolarized 13C metabolic imaging in cardiac and cancer applications are explored. Spiral pulse sequences for multislice imaging of [1‐13C]pyruvate in the heart were developed, as well as time‐resolved, three‐dimensional, echo‐planar imaging sequences for the imaging of [1‐13C]pyruvate–lactate exc... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5013336 Mon, 11 Jul 2011 23:00:00 +0100 5013336 http://www.medworm.com/index.php?rid=5013340&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1725 In conclusion, texture analysis can be used to quantify changes in lung ventilation as measured with HP 3He MRI after therapeutic intervention with budesonide. Copyright © 2011 John Wiley & Sons, Ltd.The effect of steroid (budesonide) treatment on lung inflammation in rats caused by ovalbumin can be visualised using hyperpolarised 3He MRI. Changes in lung ventilation in this asthma model were quantified using texture analysis. The texture analysis showed significant differences between the control, vehicle‐treated and budesonide‐treated groups, which was in agreement with a biological marker. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5013340 Wed, 06 Jul 2011 23:00:00 +0100 5013340 http://www.medworm.com/index.php?rid=5002469&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1724 This study provides the first evidence for the direct detection of a magnetic field from an evoked action potential using MR. Copyright © 2011 John Wiley & Sons, Ltd.This study provides the first evidence for the direct detection of the transient magnetic field induced by a single evoked action potential in the nerve cord of earthworms. Using simultaneous MRS and electrophysiology, we observed a phase change at a submillisecond temporal resolution in the free induction decay that corresponded to the time‐locked action potential. Amplitude and temporal characteristics of our experimental results correlate well with the theoretical predictions of the volume conductor model. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5002469 Mon, 04 Jul 2011 23:00:00 +0100 5002469 http://www.medworm.com/index.php?rid=5090622&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1747 We present a technique termed anomalous diffusion tensor imaging, allowing directional properties of the distributed diffusion coefficient α and the anomalous diffusion exponent γ to be analysed using the analytical techniques of regular diffusion tensor imaging (DTI). These parameters quantify the rate of diffusion (α) and complexity of the diffusion environment (γ). We observe that distributed diffusivity tensor show similar anisotropic geometry to regular DTI, whereas anomalous exponent tensors exhibit different shape characteristics that may be informative of tissue microstructure. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5090622 Thu, 30 Jun 2011 23:00:00 +0100 5090622 http://www.medworm.com/index.php?rid=5082576&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1755 A method for the measurement of temperature in the lateral ventricle using diffusion‐weighted imaging (DWI) has been proposed recently. This method uses predetermined arbitrary thresholds, but a more objective method of calculation would be useful. We therefore compared four different calculation methods, two of which were newly created and did not require predetermined thresholds. A rectangular polyethylene terephthalate bottle (8 × 10 × 28 cm3) was filled with heated water (35.0–38.8 °C) and used as a water phantom. The DWI data of 23 healthy subjects (aged 26–75 years; mean ± standard deviation, 50.13 ± 19.1 years) were used for this study. The temperature was calculated using the following equation: T(°C) = 2256.74/ln(4.39221/D) − 273.15, w... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5082576 Thu, 30 Jun 2011 23:00:00 +0100 5082576 http://www.medworm.com/index.php?rid=5072866&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1756 A method is presented to correct the effects of motion and motion‐related B0 perturbations on spectroscopic imaging in real time through the use of a volumetric navigator. It is demonstrated that, for an axial slice, lifting the chin significantly disrupts the B0 homogeneity in the zero‐order (frequency), first‐order Y (coronal) axis and second‐order ZY term. This volumetric navigator is able to measure and correct in real time both head pose and zero‐ to first‐order B0 inhomogeneities. The volumetric navigator was validated in six volunteers who deliberately lifted and then dropped their chin during the scan. These scans show that motion correction alone is not sufficient to recover the spectral quality. By applying real‐time shim adjustments, spectral quality was fully reco... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5072866 Thu, 30 Jun 2011 23:00:00 +0100 5072866 http://www.medworm.com/index.php?rid=5065773&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1731 This article provides a literature review of the use of MRI in monitoring the treatment response of soft tissue sarcomas. The basic classification and physiology of soft tissue tumors are introduced. Then, the major treatment options for soft tissue sarcomas are summarized with brief coverage of possible responses and grading systems. Four major branches of MRI techniques are covered, including conventional T1‐ and T2‐weighted imaging, contrast‐enhanced MRI, MR diffusion and perfusion imaging, and MRS, with a focus on the tumor microenvironment. Although this literature survey focuses on recent clinical developments using these MRI techniques, research venues in preclinical studies, as well as in potential applications other than soft tissue sarcomas, are also included when comparabl... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5065773 Thu, 30 Jun 2011 23:00:00 +0100 5065773 http://www.medworm.com/index.php?rid=5065772&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1738 This study investigates the relationship between phospholipid metabolite concentrations, Gleason score, rate of cellular proliferation and surgical stage in malignant prostatectomy samples by performing one‐ and two‐dimensional, high‐resolution magic angle spinning, total correlation spectroscopy, pathology and Ki‐67 staining on the same surgical samples. At radical prostatectomy, surgical samples were obtained from 49 patients [41 with localized TNM stage T1 and T2, and eight with local cancer spread (TNM stage T3)]. Thirteen of the tissue samples were high‐grade prostate cancer [Gleason score: 4 + 3 (n = 7); 4 + 4 (n = 6)], 22 low‐grade prostate cancer [Gleason score: 3 + 3 (n = 17); 3 + 4 (n = 5)] and 14 benign prostate tissues. This study dem... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5065772 Thu, 30 Jun 2011 23:00:00 +0100 5065772 http://www.medworm.com/index.php?rid=5065771&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1751 MRS and MRSI are valuable tools for the detection of metabolic changes in tumors. The currently emerging era of molecular medicine, which is shaped by molecularly targeted anticancer therapies combined with molecular imaging of the effects of such therapies, requires powerful imaging technologies that are able to detect molecular information. MRS and MRSI are such technologies that are able to detect metabolites arising from glucose and choline metabolism in noninvasive in vivo settings and at higher resolution in tissue samples. The roles played by MRS and MRSI in the diagnosis of different types of cancer, as well as in the early monitoring of the tumor response to traditional chemotherapies, are reviewed. The emerging roles of MRS and MRSI in the development and detection of novel targe... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5065771 Thu, 30 Jun 2011 23:00:00 +0100 5065771 http://www.medworm.com/index.php?rid=5059162&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1760 In this report, we evaluate the utility of three different intravascular ultrasmall superparamagnetic iron oxide (USPIO) contrast agents for phMRI using a gradient‐echo technique, with temporal resolution of one min at high magnetic field. The tissue half‐life of the USPIOs was studied using a nonlinear detrending model. The three USPIOs are candidates for CBV weighted phMRI experiments, with r2/r1 ratios ≥ 20 and apparent half‐lives ≥ 1.5 h at the described doses. An echo‐time of about 10 ms or longer results in a functional contrast to noise ratio (fCNR) > 75 after USPIO injection, with negligible decrease between 1.5‐2 h. phMRI experiments were conducted at 7 T using cocaine as a psychotropic substance and acetazolamide, a global vasodilator, as a po... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5059162 Tue, 31 May 2011 23:00:00 +0100 5059162 http://www.medworm.com/index.php?rid=5054723&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1737 In this study, for the first time, we show that angular d‐PFG experiments can be used to accurately measure cellular size and shape anisotropy of fixed yeast cells employing relatively weak gradients. The cell size, as measured by light microscopy, was found to be 5.32 ± 0.83 µm, whereas the results from noninvasive angular d‐PFG experiments yielded a cell size of 5.46 ± 0.45 µm. Moreover, the low compartment shape anisotropy of the cells could be inferred from experiments conducted at long mixing times. Finally, similar experiments were conducted in a phantom comprising anisotropic compartments that were randomly oriented, showing that angular d‐PFG MR provides novel information on compartment eccentricity that could not be accessed using conventional methods. Angula... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5054723 Tue, 31 May 2011 23:00:00 +0100 5054723 http://www.medworm.com/index.php?rid=5043830&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1730 In this work we introduce the concept of correlation chemical shift imaging (CCSI). Novel CCSI pulse sequences are demonstrated on clinical scanners for two‐dimensional Correlation Spectroscopy (COSY) and Total Correlation Spectroscopy (TOCSY) imaging experiments. To date there has been limited progress reported towards a feasible and robust multivoxel 2D COSY. Localized 2D TOCSY imaging is shown for the first time in this work. Excitation with adiabatic GOIA‐W(16,4) pulses (Gradient Offset Independent Adiabaticity Wurst modulation) provides minimal chemical shift displacement error, reduced lipid contamination from subcutaneous fat, uniform optimal flip angles, and efficient mixing for coupled spins, while enabling short repetition times due to low power requirements. Constant‐densi... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5043830 Tue, 31 May 2011 23:00:00 +0100 5043830 http://www.medworm.com/index.php?rid=5032788&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1728 In this study, two‐dimensional, multi‐slice, ultrashort echo time spectroscopic imaging (UTESI) was used with bi‐component analysis to detect bound and free water components in musculoskeletal tissues. Feasibility studies were performed using numerical simulation. Imaging was performed on bovine cortical bone, human cadaveric menisci and the Achilles' tendons of volunteers. The simulation study demonstrated that UTESI, together with bi‐component analysis, could reliably quantify both T2* and fractions of the short and long T2* components. The in vitro and in vivo studies each took less than 14 min. The bound water components showed a short T2* of ~0.3 ms for bovine bone, ~1.8 ms for meniscus and ~0.6 ms for the Achilles' tendon. The free water components showed about an ord... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5032788 Tue, 31 May 2011 23:00:00 +0100 5032788 http://www.medworm.com/index.php?rid=5013335&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1745 The metabolism of glycine into glutathione was monitored noninvasively in vivo in intact rat mammary adenocarcinomas (R3230Ac) by MRI and MRS. Metabolism was tracked by following the isotope label from intravenously infused [2‐13C]‐glycine into the glycinyl residue of glutathione. Signals from [2‐13C]‐glycine and γ‐glutamylcysteinyl‐[2‐13C]‐glycine (13C‐glutathione) were detected by nonlocalized 13C spectroscopy, as these resonances are distinct from background signals. In addition, using spectroscopic imaging methods, heterogeneity in the in vivo tumor distribution of glutathione was observed. In vivo spectroscopy also detected isotope incorporation from [2‐13C]‐glycine into both the 2‐ and 3‐carbons of serine. Analyses of tumor tissue extracts showed single‐ ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5013335 Tue, 31 May 2011 23:00:00 +0100 5013335 http://www.medworm.com/index.php?rid=5002468&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1709 Catheter ablation using radio frequency (RF) has been used increasingly for the treatment of cardiac arrhythmias and may be combined with proton resonance frequency shift (PRFS) ‐based MR thermometry to determine the therapy endpoint. We evaluated the suitability of two different MR thermometry sequences (TFE and TFE‐EPI) and three blood suppression techniques.Experiments were performed without heating, using an optimized imaging protocol including navigator respiratory compensation, cardiac triggering, and image processing for the compensation of motion and susceptibility artefacts. Blood suppression performance and its effect on temperature stability were evaluated in the ventricular septum of eight healthy volunteers using multislice double inversion recovery (MDIR), motion sensitiz... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=5002468 Tue, 31 May 2011 23:00:00 +0100 5002468 http://www.medworm.com/index.php?rid=4988494&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1707 In order to investigate simultaneous MR temperature imaging and direct validation of tissue damage during thermal therapy, temperature‐dependent signal changes in proton resonance frequency (PRF) shifts, R2* values, and T1‐weighted amplitudes are measured from one technique in ex vivo tissue. Using a multigradient echo acquisition and the Stieglitz‐McBride algorithm, the temperature sensitivity coefficients of these parameters are measured in each tissue at high spatiotemporal resolutions (1.6x1.6x4mm3, ≤ 5sec) at the range of 25‐61 °C. Non‐linear changes in MR parameters are examined and correlated with an Arrhenius rate dose model of thermal damage. Using logistic regression, the probability of changes in these parameters is calculated as a function of thermal dose to de... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4988494 Tue, 31 May 2011 23:00:00 +0100 4988494 http://www.medworm.com/index.php?rid=4956655&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1739 Breast MRI has several roles in the clinical management of breast cancer, including as a screening method for high‐risk women, as a diagnostic tool used as an adjunct to mammography and ultrasound, and for the staging of disease extent prior to treatment. In addition to these uses, MRI is also employed to track small changes in tumor size and microenvironment. MRI has produced several early indicators of treatment response in clinical trials over the last 10 years, including initial lesion pattern, changes in lesion size, kinetic parameters, apparent diffusion coefficient and T2 value; the related technique of 1H MRS has also shown that choline concentration, T2 value and water‐to‐fat ratio are response indicators. In addition to measuring anatomical changes in the lesion size, as ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4956655 Tue, 31 May 2011 23:00:00 +0100 4956655 http://www.medworm.com/index.php?rid=4857565&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1723 Longitudinal studies of lactate MRSI and dynamic contrast‐enhanced MRI were performed at 4.7 T in two prostate tumor models grown in rats, Dunning R3327‐AT (AT) and Dunning R3327‐H (H), to determine the potential of lactate and the perfusion/permeability parameter Akep as markers of tumor aggressiveness. Subcutaneous AT (n = 12) and H (n = 6) tumors were studied at different volumes between 100 and 2900 mm3 (Groups 1–5). Lactate concentration was determined using selective multiple quantum coherence MRSI with the phantom substitution method. Tumor enhancement after the administration of gadolinium diethylenetriaminepenta‐acetic acid was analyzed using the Brix–Hoffmann model and the Akep parameter was used as a measure of tumor perfusion/permeability. Lactate was no... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4857565 Tue, 24 May 2011 23:00:00 +0100 4857565 http://www.medworm.com/index.php?rid=4857564&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1722 This study demonstrates the feasibility of using DTI to detect brain regions associated with sociability in a mouse model system. Copyright © 2011 John Wiley & Sons, Ltd.The purpose of this study was to use high‐resolution diffusion tensor imaging (DTI) to investigate the association between DTI metrics and sociability in BALB/cJ inbred mice. Strong positive regression between the social sniffing time and fractional anisotropy was found in 10 clusters located in the thalamic nuclei, zona incerta/substantia nigra, visual/orbital/somatosensory cortices, and entorhinal cortex. In addition, strong negative regression between the social sniffing time and apparent diffusion coefficient was found in five areas located in the sensory cortex, motor cortex, external capsule and amygdaloid reg... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4857564 Tue, 24 May 2011 23:00:00 +0100 4857564 http://www.medworm.com/index.php?rid=4857567&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1693 Arterial cerebral blood volume (CBVa) is a vital indicator of tissue perfusion and vascular reactivity. We extended the recently developed inflow vascular‐space‐occupancy (iVASO) MRI technique, which uses spatially selective inversion to suppress the signal from blood flowing into a slice, with a control scan to measure absolute CBVa using cerebrospinal fluid (CSF) for signal normalization. Images were acquired at multiple blood nulling times to account for the heterogeneity of arterial transit times across the brain, from which both CBVa and arterial transit times were quantified. Arteriolar CBVa was determined separately by incorporating velocity‐dependent bipolar crusher gradients. Gray matter (GM) CBVa values (n = 11) were 2.04 ± 0.27 and 0.76 ± 0.17 ml blood/100�... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4857567 Mon, 23 May 2011 23:00:00 +0100 4857567 http://www.medworm.com/index.php?rid=4857566&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1718 Even at this early stage of development, it is clear that the imaging of hyperpolarized 13C‐enriched molecules and their metabolic products offers a new approach to the study of the physiology and disease of the heart. The technology is practical in humans and, for this reason, we consider whether a role in clinical decision‐making should motivate further development. The range of interventions available to treat coronary and valvular heart disease is already extensive, and new options are imminent. Yet the appropriate management of patients with left ventricular dysfunction can be challenging because the mechanism of reduced function may be unclear and the ability of the ventricle to respond to therapy may be difficult to predict. Pyruvate is a promising early target for development a... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4857566 Mon, 23 May 2011 23:00:00 +0100 4857566 http://www.medworm.com/index.php?rid=4857568&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1701 AbstractThe extracellular pH (pHe) of solid tumors is acidic, and there is evidence that an acidic pHe is related to invasiveness. Herein, we describe an MRI single‐infusion method to measure pHe in gliomas using a cocktail of contrast agents (CAs). The cocktail contained gadolinium–1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraaminophosphonate (GdDOTA‐4AmP) and dysprosium–1,4,7,10‐tetraazacyclododecane‐N,N′,N′′,N′′′‐tetrakis(methylenephosphonic acid) (DyDOTP), whose effects on relaxation are sensitive and insensitive to pH, respectively. The Gd‐CA dominated the spin–lattice relaxivity ΔR1, whereas the Dy‐CA dominated the spin–spin relaxivity ΔR2*. The ΔR2* effects were used to determine the pixel‐wise concentration of [Dy] which, in turn, was us... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4857568 Sun, 22 May 2011 23:00:00 +0100 4857568 http://www.medworm.com/index.php?rid=4816535&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1713 Retinal detachment results in visual loss and requires surgical treatment. The risk of retinal detachment depends, among other factors, on the vitreous rheology, which varies with age. To date, the viscoelasticity of the vitreous body has only been measured in cadaver eyes. However, the ex vivo and in vivo viscoelasticity may differ as a result of the effect of intravitreal membranes. Therefore, an MRI method and appropriate postprocessing tools were developed to determine the vitreous deformation and viscoelastic properties in the eyes of living humans. Nineteen subjects (eight women and 11 men; mean age, 33 years; age range, 14–62 years) gazed at a horizontal sinusoidal moving target during the segmented acquisition of complementary spatial modulation of magnetization images. The c... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4816535 Wed, 11 May 2011 23:00:00 +0100 4816535 http://www.medworm.com/index.php?rid=4808719&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1692 To explore brain involvement in chronic fatigue syndrome (CFS), the statistical parametric mapping of brain MR images has been extended to voxel‐based regressions against clinical scores. Using SPM5 we performed voxel‐based morphometry (VBM) and analysed T1‐ and T2‐weighted spin‐echo MR signal levels in 25 CFS subjects and 25 normal controls (NC). Clinical scores included CFS fatigue duration, a score based on the 10 most common CFS symptoms, the Bell score, the hospital anxiety and depression scale (HADS) anxiety and depression, and hemodynamic parameters from 24‐h blood pressure monitoring. We also performed group × hemodynamic score interaction regressions to detect locations where MR regressions were opposite for CFS and NC, thereby indicating abnormality in the CFS gr... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4808719 Tue, 10 May 2011 23:00:00 +0100 4808719 http://www.medworm.com/index.php?rid=4785097&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1716 We describe a simple algorithm that can accomplish similar results without a time‐consuming search. Significant reductions in g‐factor‐related noise were achieved using this new algorithm with in vivo acquisitions at 1.5 T with an eight‐element array. Copyright © 2011 John Wiley & Sons, Ltd.Parallel MRI usually leads to a deterioration in the signal‐to‐noise ratio when compared to otherwise equivalent unaccelerated acquisitions. We describe a simple algorithm that achieves significant noise reductions in highly accelerated in vivo images by taking advantage of the fact that the parallel image reconstruction matrix tends to become dominated by one principal component at large acceleration factors. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4785097 Tue, 03 May 2011 23:00:00 +0100 4785097 http://www.medworm.com/index.php?rid=4772884&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1697 AbstractIn the present study, a balanced steady‐state free precession pulse sequence combined with compressed sensing was applied to hyperpolarized 129Xe lung imaging in spontaneously breathing mice. With the aid of fast imaging techniques, the temporal resolution was markedly improved in the resulting images. Using these protocols and respiratory gating, 129Xe lung images in end‐inspiratory and end‐expiratory phases were obtained successfully. The application of these techniques for pulmonary functional imaging made it possible to simultaneously evaluate regional ventilation and gas exchange in the same animal. A comparative study between healthy and elastase‐induced mouse models of emphysema showed abnormal ventilation as well as gas exchange in elastase‐treated mice. Copyright... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4772884 Sun, 01 May 2011 23:00:00 +0100 4772884 http://www.medworm.com/index.php?rid=4907330&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1750 (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4907330 Sat, 30 Apr 2011 23:00:00 +0100 4907330 http://www.medworm.com/index.php?rid=4857563&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1721 Diffusion tensor imaging (DTI) was used to study traumatic brain injury. The impact–acceleration trauma model was used in rats. Here, in addition to diffusivities (mean, axial and radial), fractional anisotropy (FA) was used, in particular, as a parameter to characterize the cerebral tissue early after trauma. DTI was implemented at 7 T using fast spiral k‐space sampling and the twice‐refocused spin echo radiofrequency sequence for eddy current minimization. The method was carefully validated on different phantom measurements. DTI of a trauma group (n = 5), as well as a sham group (n = 5), was performed at different time points during 6 h following traumatic brain injury. Two cerebral regions, the cortex and corpus callosum, were analyzed carefully. A significant decrease... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4857563 Sat, 30 Apr 2011 23:00:00 +0100 4857563 http://www.medworm.com/index.php?rid=4816534&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1720 MRI and MRS techniques are being applied to the characterisation of various aspects of the tumour microenvironment and to the assessment of tumour response to therapy. For example, kinetic parameters describing tumour blood vessel flow and permeability can be derived from dynamic contrast‐enhanced MRI data and have been correlated with a positive tumour response to antivascular therapies. The ongoing development and validation of noninvasive, high‐resolution anatomical/molecular MR techniques will equip us with the means to detect specific tumour biomarkers early on, and then to monitor the efficacy of cancer treatments efficiently and reliably, all within a clinically relevant time frame. Reliable tumour microenvironment imaging biomarkers will provide obvious advantages by enabling t... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4816534 Sat, 30 Apr 2011 23:00:00 +0100 4816534 http://www.medworm.com/index.php?rid=4808718&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1681 AbstractSubanesthetic doses of ketamine, a noncompetitive N‐methyl‐D‐aspartate (NMDA) receptor antagonist, impair prefrontal cortex (PFC) function in the rat and produce symptoms in humans similar to those observed in patients with schizophrenia. In the present study, in vivo1H‐MRS and ex vivo1H high‐resolution magic angle spinning (HR‐MAS) spectroscopy was used to examine the brain metabolism of rats treated with subanesthetic doses of ketamine (30 mg/kg) for 6 days. A single voxel localization sequence (PRESS, TR/TE = 4000/20 ms and NEX = 512) was used to acquire the spectra in a 30‐µl voxel positioned in the cerebral cortex (including mainly PFC) of the rats (ketamine group: n = 12; saline group: n = 12) anesthetized with isoflurane. After the in vivo1... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4808718 Sat, 30 Apr 2011 23:00:00 +0100 4808718 http://www.medworm.com/index.php?rid=4799556&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1714 This study aims to identify the impact of gadolinium‐based contrast agents on Cho detection and quantification in postcontrast breast MRS. Consecutive patients were recruited prospectively and randomly allocated to two groups. Group A received a neutral (gadolinium diethylenetriaminepentaacetic acid bis‐methylamide) and group B an ionic (gadolinium diethylenetriaminepentaacetic acid) contrast agent, each at a dosage of 0.1 mmol/kg. First, the presence of Cho was identified visually. Then, the normalized Cho intensity in malignant lesions was quantified. Multivariate analysis was applied to identify ind ependent influencing factors on Cho. Sixty‐three lesions were investigated [A, n = 34; B, n = 29; 43 malignant (one bilaterally malignant), 20 benign]. Cho was identified vis... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4799556 Sat, 30 Apr 2011 23:00:00 +0100 4799556 http://www.medworm.com/index.php?rid=4785096&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1694 In this study, hypothalamic activation was performed by dehydration‐induced anorexia (DIA) and overnight food suppression (OFS) in female rats. The assessment of the hypothalamic response to these challenges by manganese‐enhanced MRI showed increased neuronal activity in the paraventricular nuclei (PVN) and lateral hypothalamus (LH), both known to be areas involved in the regulation of food intake. The effects of DIA and OFS were compared by generating T‐score maps. Increased neuronal activation was detected in the PVN and LH of DIA rats relative to OFS rats. In addition, the neurochemical profile of the PVN and LH were measured by 1H MRS at 14.1 T. Significant increases in metabolite levels were measured in DIA and OFS relative to control rats. Statistically significant increases ... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4785096 Sat, 30 Apr 2011 23:00:00 +0100 4785096 http://www.medworm.com/index.php?rid=4772883&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1684 AbstractCell‐based therapies represent important novel strategies for the improved treatment of various diseases. To monitor the progress of therapy and cell migration, noninvasive imaging methods are needed. MRI represents such a modality, allowing, for example, for the tracking of cells labeled with superparamagnetic iron oxide nanoparticles. Unfortunately, the labeled cells cannot always be identified nonambiguously in the MR images. In this article, we present the combination of two different types of MR experiment to identify iron oxide‐labeled cells nonambiguously. The labeled cells appear as hypointense spots on standard T2*‐weighted MR images. Furthermore, they can be heated magnetically and subsequently identified by MR thermometry as a result of their heat dissipation. Othe... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4772883 Sat, 30 Apr 2011 23:00:00 +0100 4772883 http://www.medworm.com/index.php?rid=4765291&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1719 In this study, we focus on the 13C labeling of lactate and alanine and do not differentiate the labeling mechanism (net flux or isotopic exchange) or the respective contribution of various factors (organ perfusion rate, substrate transport kinetics, enzyme activities and the size of the unlabeled lactate and alanine pools) to the labeling process. Copyright © 2011 John Wiley & Sons, Ltd.We have developed an efficient quantification framework employing a spiral‐based dynamic spectroscopic imaging approach. The approach demonstrates that in vivo13C labeling of lactate and alanine after a bolus injection of [1‐13C]pyruvate is well approximated by saturatable kinetics, which can be mathematically modeled using a Michaelis–Menten‐like formulation, with the resulting estimated app... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4765291 Sat, 30 Apr 2011 04:11:53 +0100 4765291 http://www.medworm.com/index.php?rid=4760284&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1717 We present MR hyperpolarized reagents with bio‐sensing specificity. This concept is exemplified by 13C parahydrogen‐induced polarization of 17% hyperpolarized (corresponding to a 42 000‐fold signal gain at 4.7 T) 2,2,3,3‐tetrafluoropropyl 1‐13C‐propionate‐d2,3,3 (TFPP). TFPP senses lipids, which is achieved by the exchange of hyperpolarized TFPP between lipids and aqueous medium, resulting in two 13C hyperpolarized MR signals. Proof‐of‐concept in vivo results suggest that hyperpolarized TFPP may be potentially useful as a molecular probe for atheromatous plaque imaging. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4760284 Thu, 28 Apr 2011 20:15:17 +0100 4760284 http://www.medworm.com/index.php?rid=4760286&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1715 In conclusion, quantitative MEMRI with ADC/T2 mapping provides objective information for the in vivo assessment of cellular level alterations by prenatal radiation exposure, and has the potential to be used as a standard approach for the evaluation of the cellular damage of radiotherapy. Copyright © 2011 John Wiley & Sons, Ltd.We quantitatively assessed the central nervous system of a developmental disorder induced by prenatal X‐ray exposure using manganese‐enhanced MRI (MEMRI). ΔR1 (increase in the longitudinal relaxation rate (R1) from before and after MnCl2 administration.) of MEMRI in radiation‐exposed rats (0.59 ± 0.02 s–1) was significant smaller in comparison with that for normal rats (0.81 ± 0.08 s–1). MEMRI predominantly reflected the decrease in cell... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4760286 Wed, 27 Apr 2011 23:00:00 +0100 4760286 http://www.medworm.com/index.php?rid=4760285&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1704 We propose a Bayesian smoothness prior in the spectral fitting of MRS images which can be used in addition to commonly employed prior knowledge. By combining a frequency‐domain model for the free induction decay with a Gaussian Markov random field prior, a new optimization objective is derived that encourages smooth parameter maps. Using a particular parameterization of the prior, smooth damping, frequency and phase maps can be obtained whilst preserving sharp spatial features in the amplitude map. A Monte Carlo study based on two sets of simulated data demonstrates that the variance of the estimated parameter maps can be reduced considerably, even below the Cramér–Rao lower bound, when using spatial prior knowledge. Long‐TE 1H MRSI at 1.5 T of a patient with a brain tumor shows t... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4760285 Wed, 27 Apr 2011 23:00:00 +0100 4760285 http://www.medworm.com/index.php?rid=4760289&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1669 AbstractMRI is routinely used for diagnosis, treatment planning and assessment of response to therapy for patients with glioma. Gliomas are spatially heterogeneous and infiltrative lesions that are quite variable in terms of their response to therapy. Patients classified as having low‐grade histology have a median overall survival of 7 years or more, but need to be monitored carefully to make sure that their tumor does not upgrade to a more malignant phenotype. Patients with the most aggressive grade IV histology have a median overall survival of 12–15 months and often undergo multiple surgeries and adjuvant therapies in an attempt to control their disease. Despite improvements in the spatial resolution and sensitivity of anatomic images, there remain considerable ambiguities in the in... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4760289 Tue, 26 Apr 2011 23:00:00 +0100 4760289 http://www.medworm.com/index.php?rid=4760288&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1672 In this study, we tested whether a 4‐week treatment with this bile acid (12–15 mg/kg/day) could improve hepatic fatty acid oxidation in obese Zucker rats – a model for nonalcoholic fatty liver disease and steatosis. After 24 h of fasting, livers were perfused with physiological concentrations of [U‐13C]nonesterified fatty acids and [3‐13C]lactate/[3‐13C]pyruvate. Steatosis was associated with abundant intracellular glucose, lactate, alanine and methionine, and low concentrations of choline and betaine. Steatotic livers also showed the highest output of glucose and lactate. Glucose and glycolytic products were mostly unlabeled, indicating active glycogenolysis and glycolysis after 24 h of fasting. UDCA treatment resulted in a general amelioration of liver metabolic abnorma... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4760288 Tue, 26 Apr 2011 23:00:00 +0100 4760288 http://www.medworm.com/index.php?rid=4760287&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1661 AbstractMR‐visible lipids or mobile lipids are defined as lipids that are observable using proton MRS in cells and tissues. These MR‐visible lipids are composed of triglycerides and cholesterol esters that accumulate in neutral lipid droplets, where their MR visibility is conferred as a result of the increased molecular motion available in this unique physical environment. This review discusses the factors that lead to the biogenesis of MR‐visible lipids in cancer cells and in other cell types, such as immune cells and fibroblasts. We focus on the accumulations of mobile lipids that are inducible in cultured cells by a number of stresses, including culture conditions, and in response to activating stimuli or apoptotic cell death induced by anticancer drugs. This is compared with anim... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4760287 Tue, 26 Apr 2011 23:00:00 +0100 4760287 http://www.medworm.com/index.php?rid=4689343&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1702 In this study, we investigated possible differences in neural correlates of negative emotional experiences between abstinent MA abusers and healthy subjects using complex visual scenes depicting fear or threat derived from the International Affective Picture System. In within‐group analyses, healthy subjects and MA abusers activated a similarly distributed cortical network, prominently including the amygdala, fusiform gyrus, parahippocampal gyrus, ventrolateral prefrontal cortex and inferior frontal cortex. In between‐group analyses, however, MA abusers showed a reduced activation in the bilateral dorsolateral prefrontal cortex and insula, and increased activation in the fusiform gyrus, hippocampus, parahippocampal gyrus and posterior cingulate cortex, relative to healthy subjects. Hyp... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4689343 Wed, 06 Apr 2011 23:00:00 +0100 4689343 http://www.medworm.com/index.php?rid=4679027&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1705 This study reports in vivo MRS findings in 11 patients with histologically diagnosed central neurocytomas, which are rare intraventricular tumors of neuronal origin. Single‐voxel 1H MRS was carried out prior to surgery using a point‐resolved spectroscopy sequence with TR = 6 s, TE = 135 ms and 128 scans. In vitro high‐resolution 1H spectroscopy was also carried out on two surgically excised samples. The striking features of the spectra from the central neurocytomas were the presence of high glycine, decreased N‐acetylaspartate, increased choline and alanine. Retrospective, blind analysis of the spectra by two independent observers correctly identified all but one central neurocytoma based on the presence of glycine. The presence of glycine and prominent choline in the 1... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4679027 Sun, 03 Apr 2011 23:00:00 +0100 4679027 http://www.medworm.com/index.php?rid=4679026&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1703 Localized in vivo1H NMR spectroscopy is playing an increasing role in preclinical studies, because of its ability to quantify the concentrations of up to 20 metabolites in rat brain. To assess the differences between often‐used rat strains, the neurochemical profiles of Sprague‐Dawley, Wistar and Fischer rats were determined at ultrashort TE at 16.4 T. To ascertain high‐qualitative quantification, a first experiment examined the dependence of the measuring time on the quantification results and precision by precisely the number of averages between 16 and 320. It was shown that most metabolites can be quantified accurately within a short scan time, yielding Cramér–Rao lower bounds below 20% and stable concentrations for 16 metabolites with as few as 32 or 64 averages in the thalamu... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4679026 Sun, 03 Apr 2011 23:00:00 +0100 4679026 http://www.medworm.com/index.php?rid=4689342&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1706 This article aims to validate high‐resolution, time‐resolved, three‐dimensional phase contrast MRI (PC‐MRI) measurements in a real‐size intracranial aneurysm phantom by comparing velocity vectors from PC‐MRI with velocity vectors derived from particle image velocimetry (PIV) measurements and computational fluid dynamics (CFD) simulations. Good agreement was found in the comparison of flow patterns between the PC‐MRI measurements and both PIV measurements and CFD simulations. We conclude that high‐resolution, time‐resolved, three‐dimensional PC‐MRI can accurately measure complex flow patterns in an intracranial aneurysm phantom. (Source: NMR in Biomedicine) NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4689342 Thu, 31 Mar 2011 23:00:00 +0100 4689342 http://www.medworm.com/index.php?rid=4679025&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1690 We present a multiexponential approach which does not require contrast agents or specialized hardware, and uses a standard multiple‐echo spin‐echo sequence. Experiments were performed on tissue models of degenerative cartilage using enzymes with distinct actions. MR results were validated using histologic, biochemical and infrared spectroscopic analyses. The sulfated glycosaminoglycan per dry weight (dw) in bovine nasal cartilage was 0.72 ± 0.06 mg/mg dw and was reduced through chondroitinase AC and collagenase digestion to 0.56 ± 0.12 and 0.58 ± 0.13 mg/mg dw, respectively. Multiexponential analysis of data obtained at 9.4 T permitted the identification of tissue compartments assigned to the proteoglycan component of the matrix and to bulk water. Enzymatic treatment... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4679025 Thu, 31 Mar 2011 23:00:00 +0100 4679025 http://www.medworm.com/index.php?rid=4673223&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1683 AbstractTumor cells have increased glycolytic activity, and glucose is mainly used to form lactate and alanine, even when high concentrations of oxygen are present (Warburg effect). The purpose of the present study was to investigate glucose metabolism in two xenograft models representing basal‐like and luminal‐like breast cancer using 13C high‐resolution‐magic angle spinning (HR‐MAS) MRS and gene expression analysis. Tumor tissue was collected from two groups for each model: untreated mice (n = 19) and a group of mice (n = 16) that received an injection of [1‐13C]‐glucose 10 or 15 min before harvesting the tissue. 13C HR‐MAS MRS was performed on the tumor samples and differences in the glucose/alanine (Glc/Ala), glucose/lactate (Glc/Lac) and alanine/lactate (Ala/... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4673223 Thu, 31 Mar 2011 23:00:00 +0100 4673223 http://www.medworm.com/index.php?rid=4628756&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1698 AbstractMRI is being used increasingly for the noninvasive longitudinal monitoring of cellular processes in various pathophysiological conditions. Macrophages are the main stromal cells in neoplasms and have been suggested to be the major cell type ingesting superparamagnetic iron oxide (SPIO) nanoparticles. However, no MRI study has described longitudinally the presence of tumor‐associated macrophages (TAMs) during tumorigenesis with histological confirmation. To address this, we injected SPIO nanoparticles into the circulation of tumor‐bearing mice and used MRI and post‐mortem histology to monitor TAMs at different time points. The MRI results demonstrated that TAMs, as hypointense signals, appeared continually with the expansion of the tumor. The histological findings also reveale... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4628756 Thu, 24 Mar 2011 22:00:32 +0100 4628756 http://www.medworm.com/index.php?rid=4628761&cid=s_33609_37_f&fid=33609&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fnbm.1676 AbstractIt was our aim to investigate the gadolinium diethylenetriaminepentaacetate (Gd‐DTPA2−) enhancement kinetics in the menisci of the knee joint over a prolonged period of time. Six asymptomatic volunteers (four men and two women; mean age, 25 ± 2.4 years) were enrolled. Sagittal, T1‐weighted, spin‐echo MR sequences of the right knee joint were obtained at 3 T. Imaging was performed before (baseline), 1 h after and in half‐hour intervals up to 9 h after the intravenous administration of 0.2 mmol/kg of Gd‐DTPA2−. To measure the rates of contrast enhancement relative to the baseline, regions of interest that covered the anterior and posterior horns of the medial and lateral meniscus were defined on each of two adjacent sections, and enhancement curves were con... NMR in Biomedicine journals http://www.medworm.com/rss/comments.php?id=4628761 Thu, 24 Mar 2011 00:00:00 +0100 4628761