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 'Magnetic Resonance Imaging' source. Thu, 09 Feb 2012 03:37:45 +0100 http://www.medworm.com/index.php?rid=5586794&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11004991%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586794 Sat, 14 Jan 2012 19:42:39 +0100 5586794 http://www.medworm.com/index.php?rid=5586793&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11004966%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586793 Sat, 14 Jan 2012 19:42:38 +0100 5586793 http://www.medworm.com/index.php?rid=5586801&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003523%2Fabstract%3Frss%3Dyes In this study, we demonstrate that high quality prostate spectra can be obtained by reducing the TE to 40 ms to detect short T2 metabolites, while maintaining positive signal intensity of the spin-coupled citrate multiplet and managing lipid suppression. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586801 Mon, 12 Dec 2011 05:00:00 +0100 5586801 http://www.medworm.com/index.php?rid=5479430&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11004346%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479430 Wed, 07 Dec 2011 20:59:01 +0100 5479430 http://www.medworm.com/index.php?rid=5479429&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11004310%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479429 Wed, 07 Dec 2011 20:59:01 +0100 5479429 http://www.medworm.com/index.php?rid=5586806&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003353%2Fabstract%3Frss%3Dyes Abstract: The successful translation of stem-cell therapies requires a detailed understanding of the fate of transplanted cells. Magnetic resonance imaging (MRI) has provided a noninvasive means of imaging cell dynamics in vivo by prelabeling cell with T2⁎ shortening iron oxide particles. However, this approach suffers from a gradual loss of sensitivity since active cell mitosis could decrease the cellular contrast agent (CA) concentration below detection level. In addition, the interpretation of images may be confounded by hypointensities induced by factors other than this CA susceptibility effect (CASE). We therefore examined the feasibility of exploiting the phase information in MRI to increase the sensitivity of cellular imaging and to differentiate the CASE from endogenous image hyp... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586806 Fri, 02 Dec 2011 05:00:00 +0100 5586806 http://www.medworm.com/index.php?rid=5586805&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003390%2Fabstract%3Frss%3Dyes Abstract: Magnetic resonance imaging (MRI) is a valuable diagnostic tool in medical science due to its capability for soft-tissue characterization and three-dimensional visualization. One potential application of MRI in clinical practice is brain parenchyma classification and segmentation. Based on fuzzy knowledge and modified seeded region growing, this work proposes a novel image segmentation method, called Fuzzy Knowledge-Based Seeded Region Growing (FKSRG), for multispectral MR images. In this work, fuzzy knowledge includes the fuzzy edge, fuzzy similarity and fuzzy distance, which are obtained from relationships between pixels in multispectral MR images and are applied to the modified seeded regions growing process. In conventional regions merging, the final number of regions is unkno... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586805 Fri, 02 Dec 2011 05:00:00 +0100 5586805 http://www.medworm.com/index.php?rid=5586797&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003511%2Fabstract%3Frss%3Dyes Abstract: At present, accurate assessment of therapeutic efficacy at the early stage of treatment is still a challenge for radiologists. As a new non-radiation whole body imaging technology, Whole body-diffusion weighted imaging (WB-DWI) had shown promising application prospects in therapeutic assessment, which confirmed by many premier animal studies. Here we report that in the chemotherapeutic assessment of malignant non-Hodgkin's lymphoma, WB-DWI can not only detect the morphological change of solid infiltrated lesion as the convention (such as CT, PET, etc.) but also provide information about the growth and decline process of tumor cells in the lesion combining with the dynamic changes of apparent diffusion coefficient (ADC) value, which is sooner than the morphological changes. (Sourc... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586797 Fri, 02 Dec 2011 05:00:00 +0100 5586797 http://www.medworm.com/index.php?rid=5461151&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003298%2Fabstract%3Frss%3Dyes Abstract: The number of functional magnetic resonance imaging (fMRI) studies performed on the human spinal cord (SC) has considerably increased in recent years. The lack of a validated processing pipeline is, however, a significant obstacle to the spread of SC fMRI. One component likely to be involved in any such pipeline is the process of SC masking, analogous to brain extraction in cerebral fMRI. In general, SC masking has been performed manually, with the incumbent costs of being very time consuming and operator dependent.To overcome these drawbacks, we have developed a tailored semiautomatic method for segmenting echoplanar images (EPI) of human spine that is able to identify the spinal canal and the SC. The method exploits both temporal and spatial features of the EPI series and was t... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461151 Thu, 01 Dec 2011 05:00:00 +0100 5461151 http://www.medworm.com/index.php?rid=5461136&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11004176%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461136 Thu, 01 Dec 2011 05:00:00 +0100 5461136 http://www.medworm.com/index.php?rid=5461135&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11004000%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461135 Thu, 01 Dec 2011 05:00:00 +0100 5461135 http://www.medworm.com/index.php?rid=5586808&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003377%2Fabstract%3Frss%3Dyes Conclusion: Numerous studies suggest a critical role of monoamines in the behavioral, pharmacological and addictive properties of psychostimulants. It is suggested that l-THP holds great potential to be a therapeutic medication for drug addiction. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586808 Mon, 14 Nov 2011 05:00:00 +0100 5586808 http://www.medworm.com/index.php?rid=5586798&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003845%2Fabstract%3Frss%3Dyes Abstract: Background and Purpose: Current approaches to diffusion tensor imaging (DTI) analysis do not permit identification of individual-level changes in DTI indices. We investigated the ability of wild bootstrapping analysis to detect subject-specific changes in brain white matter (WM) before and after sports-related concussion.Materials and Methods: A prospective cohort study was performed in nine high school athletes engaged in hockey or football and six controls. Subjects underwent DTI pre- and postseason within a 3-month interval. One athlete was diagnosed with concussion (scanned within 72 h), and eight suffered between 26 and 399 subconcussive head blows. Fractional anisotropy (FA) and mean diffusivity (MD) were measured in each WM voxel. Bootstrap samples were generated, and a pe... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586798 Mon, 14 Nov 2011 05:00:00 +0100 5586798 http://www.medworm.com/index.php?rid=5586809&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003572%2Fabstract%3Frss%3Dyes Conclusion: We conclude that there are definite relationships between cartilaginous changes as seen on MRI and late-stage microstructural bony changes after traumatic ACL injury in rabbits. In addition, doxycycline may show promise in mitigating early-stage cartilage damage that may serve to lessen late-stage osteoarthritic changes. This study demonstrates the ability to track OA progression and therapeutic efficacy with imaging modalities in vivo. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586809 Wed, 09 Nov 2011 05:00:00 +0100 5586809 http://www.medworm.com/index.php?rid=5586804&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003481%2Fabstract%3Frss%3Dyes Abstract: White matter loss, ventricular enlargement and white matter lesions are common findings on brain scans of older subjects. Accurate assessment of these different features is therefore essential for normal aging research. Recently, we developed a novel unsupervised classification method, named ‘Multispectral Coloring Modulation and Variance Identification’ (MCMxxxVI), that fuses two different structural magnetic resonance imaging (MRI) sequences in red/green color space and uses Minimum Variance Quantization (MVQ) as the clustering technique to segment different tissue types. Here we investigate how this method performs compared with several commonly used supervised image classifiers in segmenting normal-appearing white matter, white matter lesions and cerebrospinal fluid in th... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586804 Wed, 09 Nov 2011 05:00:00 +0100 5586804 http://www.medworm.com/index.php?rid=5479434&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003365%2Fabstract%3Frss%3Dyes Abstract: Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is performed by obtaining sequential MRI images, before, during and after the injection of a contrast agent. It is usually used to observe the exchange of contrast agent between the vascular space and extravascular extracellular space (EES), and provide information about blood volume and microvascular permeability. To estimate the kinetic parameters derived from the pharmacokinetic model, accurate knowledge of the arterial input function (AIF) is very important. However, the AIF is usually unknown, and it remains very difficult to obtain such information noninvasively. In this article, without knowledge of the AIF, we applied a reference region (RR) model to analyze the kinetic parameters. The RR model usually depends... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479434 Wed, 09 Nov 2011 05:00:00 +0100 5479434 http://www.medworm.com/index.php?rid=5586803&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003468%2Fabstract%3Frss%3Dyes Abstract: SENSitivity Encoding (SENSE) is a mathematically optimal parallel magnetic resonance (MRI) imaging technique when the coil sensitivities are known. In recent times, compressed sensing (CS)-based techniques are incorporated within the SENSE reconstruction framework to recover the underlying MR image. CS-based techniques exploit the fact that the MR images are sparse in a transform domain (e.g., wavelets). Mathematically, this leads to an l1-norm-regularized SENSE reconstruction.In this work, we show that instead of reconstructing the image by exploiting its transform domain sparsity, we can exploit its rank deficiency to reconstruct it. This leads to a nuclear norm-regularized SENSE problem. The reconstruction accuracy from our proposed method is the same as the l1-norm-regularize... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586803 Mon, 07 Nov 2011 05:00:00 +0100 5586803 http://www.medworm.com/index.php?rid=5586802&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003493%2Fabstract%3Frss%3Dyes Abstract: In magnetic resonance elastography (MRE), shear waves at a certain frequency are encoded through bipolar gradients that switch polarity at a controlled encoding frequency and are offset in time to capture wave propagation using a controlled sampling frequency. In brain MRE, there is a possibility that the mechanical actuation frequency is different from the vibration frequency, leading to a mismatch with encoding and sampling frequencies. This mismatch can occur in brain MRE from causes both extrinsic and intrinsic to the brain, such as scanner bed vibrations or active damping in the head. The purpose of this work was to investigate how frequency mismatch can affect MRE shear stiffness measurements. Experiments were performed on a dual-medium agarose gel phantom, and the results ... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586802 Mon, 07 Nov 2011 05:00:00 +0100 5586802 http://www.medworm.com/index.php?rid=5586800&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003560%2Fabstract%3Frss%3Dyes Abstract: Prostate cancer detection using diffusion-weighted imaging is highly affected by the accuracy of the apparent diffusion coefficient (ADC) values in an image. Echo planar imaging (EPI) is a fast sequence commonly used for diffusion imaging but has inherent magnetic susceptibility and chemical shift artefacts associated. A diffusion sequence that is less affected by these artefacts is therefore advantageous. The half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence was chosen. The diffusion sequences were compared in image quality, repeatability of the ADC value and the effect on the ADC value with varied b values. Eight volunteers underwent three scans of each sequence, on a 1.5-T Siemens system, using b values of 0, 150, 300, 450, 600, 750, 900 and 1000 s/mm2. ADC... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586800 Mon, 07 Nov 2011 05:00:00 +0100 5586800 http://www.medworm.com/index.php?rid=5479446&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003389%2Fabstract%3Frss%3Dyes Abstract: Purpose: The purpose of the study was to investigate the relationship between gas challenge–blood oxygen level-dependent (GC-BOLD) response angiogenesis and tumor size in rat Novikoff hepatoma model.Materials and Methods: Twenty adult male Sprague–Dawley rats (weighting 301–325 g) were used for our Animal Care and Use Committee-approved experiments. N1-S1 Novikoff hepatomas were grown in 14 rats with sizes ranging from 0.42 to 2.81 cm. All experiments were performed at 3.0 T using a custom-built rodent receiver coil. A multiple gradient-echo sequence was used for R2⁎ measurements, first during room air (78% N2/20% O2) breathing and then after 10 min of carbogen (95% O2/5% CO2) breathing. After image acquisition, rats were euthanized, and the tumors were harvested for hist... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479446 Mon, 07 Nov 2011 05:00:00 +0100 5479446 http://www.medworm.com/index.php?rid=5479441&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002852%2Fabstract%3Frss%3Dyes Conclusions: HSA was successfully labeled, and an albumin-based microbubble with Gd was synthesized. This contrast agent, Gd-PESDA, may serve as an additional agent for the MRI evaluation of innate inflammation and used to noninvasively image early vascular pathophysiologic processes.Condensed Abstract: In this study, Gd-PESDA microbubbles and were synthesized and shown to detect the binding of these microbubbles using MRI in injured aortic tissue. The method for synthesizing Gd-PESDA is detailed, and the proposed utility of this new contrast agent is discussed. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479441 Mon, 07 Nov 2011 05:00:00 +0100 5479441 http://www.medworm.com/index.php?rid=5479440&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100333X%2Fabstract%3Frss%3Dyes Abstract: Intensity inhomogeneities cause considerable difficulty in the quantitative analysis of magnetic resonance (MR) images. Thus, bias field correction is a necessary step before quantitative analysis of MR data can be undertaken. This paper presents an anisotropic approach to bias correction and segmentation for images with intensity inhomogeneities and noise. Intensity-based methods are usually applied to estimate the bias field; however, most of them only concern the intensity information. When the images have noise or slender topological objects, these methods cannot obtain accurate results or bias fields. We use structure information to construct an anisotropic Gibbs field and combine the anisotropic Gibbs field with the Bayesian framework to segment images while estimating the ... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479440 Mon, 07 Nov 2011 05:00:00 +0100 5479440 http://www.medworm.com/index.php?rid=5479438&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002402%2Fabstract%3Frss%3Dyes We present a novel design of an MRI RF volume microcoil based on a microstrip structure. The coil consists of two parallel microstrip elements conducting RF currents in the opposite directions, thus creating homogenous RF field within the space between the microstrips. The construction of the microcoil is simple, efficient and cost-effective.Theoretical calculations and finite element method simulations were used to optimize the coil geometry to achieve optimal B1 and SNR distributions within the sample and predict parameters of the coil. The theoretical calculations were confirmed with MR images of a 1-mm-diameter capillary and a plant obtained with the double microstrip RF microcoil at 11.7 T. The in-plane resolution of MR images was 24 μm×24 μm. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479438 Mon, 07 Nov 2011 05:00:00 +0100 5479438 http://www.medworm.com/index.php?rid=5586812&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003432%2Fabstract%3Frss%3Dyes Conclusions: Based on the tests performed, this particular hospital ID wristband is considered MR safe and will not pose a hazard to a patient undergoing an MRI examination. Importantly, it is not necessary to remove this item for a patient referred for MRI. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586812 Fri, 04 Nov 2011 04:00:00 +0100 5586812 http://www.medworm.com/index.php?rid=5586811&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003547%2Fabstract%3Frss%3Dyes Abstract: In this work, an eight-element by eight-element dual-tuned quadrature volume coil with a mix of capacitor terminated half-wavelength (λ/2) and quarter-wavelength (λ/4) microstrip resonators is proposed for multinuclear magnetic resonance imaging/spectroscopy studies at 7 T. In the proton channel, λ/2 microstrip resonators with capacitive terminations on both ends are employed for operation at higher frequency of 298.1 MHz; in the heteronucleus channel, capacitor-terminated λ/4 resonators, suitable for low frequency operations, are used to meet the low frequency requirement. This mixed structure design is particularly advantageous for high field heteronuclei magnetic resonance applications with large difference in Larmor frequency of the nuclei in question. The proposed design... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586811 Fri, 04 Nov 2011 04:00:00 +0100 5586811 http://www.medworm.com/index.php?rid=5586810&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003559%2Fabstract%3Frss%3Dyes Abstract: Acetaminophen (APAP) toxicity is responsible for approximately half of all cases of acute liver failure in the United States. The mouse model of APAP toxicity is widely used to examine mechanisms of APAP toxicity. Noninvasive approaches would allow for serial measurements in a single animal to study the effects of experimental interventions on the development and resolution of hepatocellular necrosis. The following study examined the time course of hepatic necrosis using small animal magnetic resonance imaging (MRI) following the administration of 200 mg/kg ip APAP given to B6C3F1 male mice. Mice treated with saline served as controls (CON). Other mice received treatment with the clinical antidote N-acetylcysteine (APAP+NAC). Mouse liver pathology was characterized using T1- and ... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586810 Fri, 04 Nov 2011 04:00:00 +0100 5586810 http://www.medworm.com/index.php?rid=5586807&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100350X%2Fabstract%3Frss%3Dyes Conclusion: Our findings demonstrated that DCE-MRI can assess peripheral tissue perfusion disorder in diabetes. DCE-MRI could be suitable for noninvasive evaluation of peripheral tissue perfusion in both preclinical and clinical studies. It may also be useful for developing novel drugs to protect against diabetic vascular complications. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586807 Fri, 04 Nov 2011 04:00:00 +0100 5586807 http://www.medworm.com/index.php?rid=5586799&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003535%2Fabstract%3Frss%3Dyes This study aimed to investigate age-related degenerative changes in human lumbar IVDs using DTI. Thirty asymptomatic volunteers ranging in age from 25 to 67 years underwent single-shot diffusion weighted echo-planar imaging on a 3 T scanner. DTI-derived metrics including fractional anisotropy (FA) and mean diffusivity (MD) were analyzed by a histogram analysis method. A Mann–Whitney test was used to compare subject groups (young and elderly) with respect to the diffusion measures, and piecewise linear regression was used to characterize the change in each metric as a function of age. We found significant age-related changes in the elderly adult group, with decrease of MD (11%, P (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586799 Fri, 04 Nov 2011 04:00:00 +0100 5586799 http://www.medworm.com/index.php?rid=5586796&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003456%2Fabstract%3Frss%3Dyes Abstract: A three-dimensional balanced steady-state free precession (b-SSFP)-Dixon technique with a novel group-encoded k-space segmentation scheme called GUINNESS (Group-encoded Ungated Inversion Nulling for Non-contrast Enhancement in the Steady State) was developed. GUINNESS was evaluated for breath-held non–contrast-enhanced MR angiography of the renal arteries on 18 subjects (6 healthy volunteers, 12 patients) at 3.0 T. The method provided high signal-to-noise and contrast renal angiograms with homogeneous fat and background suppression in short breath-holds on the order of 20 s with high spatial resolution and coverage. GUINNESS has potential as a short breath-hold alternative to conventional respiratory-gated methods, which are often suboptimal in pediatric subjects and patients w... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586796 Fri, 04 Nov 2011 04:00:00 +0100 5586796 http://www.medworm.com/index.php?rid=5586795&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003420%2Fabstract%3Frss%3Dyes Abstract: The purpose of this study was to investigate the effect of parameter changes that can potentially lead to unreliable measurements in fat quantification. Chemical shift imaging was performed using spoiled gradient echo sequences with systematic variations in the following: two-dimensional/three-dimensional sequence, number of echoes, delta echo time, fractional echo factor, slice thickness, repetition time, flip angle, bandwidth, matrix size, flow compensation and field strength. Results indicated no significant (or significant but small) changes in fat fraction with parameter. The significant changes can be attributed to the known effects of T1 bias and two forms of noise bias. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5586795 Fri, 04 Nov 2011 04:00:00 +0100 5586795 http://www.medworm.com/index.php?rid=5479448&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003328%2Fabstract%3Frss%3Dyes We present an unusual artefact due to occupational reason. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479448 Fri, 04 Nov 2011 04:00:00 +0100 5479448 http://www.medworm.com/index.php?rid=5479444&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003407%2Fabstract%3Frss%3Dyes This study has provided evidence of the effectiveness of using MRE to directly assess the stiffness change in aortic wall. The results offer motivation to pursue MRE as a noninvasive method for the evaluation of arterial wall mechanical properties. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479444 Fri, 04 Nov 2011 04:00:00 +0100 5479444 http://www.medworm.com/index.php?rid=5479439&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003304%2Fabstract%3Frss%3Dyes Abstract: A practical multinuclear transceiver RF volume coil with improved efficiency for in vivo small animal 1H/13C/23Na MR applications at the ultrahigh magnetic field of 7 T is reported. In the proposed design, the coil's resonance frequencies for 1H and 13C are realized by using a traditional double-tuned approach, while the resonant frequency for 23Na, which is only some 4 MHz away from the 13C frequency, is tuned based upon 13C channel by easy-operating capacitive “frequency switches”. In contrast to the traditional triple-tuned volume coil, the volume coil with the proposed design possesses less number of resonances, which helps improve the coil efficiency and alleviate the design and operation difficulties. This coil design strategy is advantageous and well suitable for multi... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479439 Fri, 04 Nov 2011 04:00:00 +0100 5479439 http://www.medworm.com/index.php?rid=5479437&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003444%2Fabstract%3Frss%3Dyes Abstract: Manganese-enhanced magnetic resonance imaging (MEMRI) is a powerful tool for visualizing neuronal pathways and mapping brain activity modulation. A potential drawback of MEMRI lies in the toxic effects of manganese (Mn), which also depend on its administration route. The aim of this study was to analyze the effects of Mn doses injected into the nostrils of rats on both olfactory perception and MRI contrast enhancement. For this purpose, doses in the range 0–8 μmol MnCl2 were tested. Behavioral items were quantified with and without odor stimulation during the first 2 h following Mn injection. The MRI study was performed after 16 h of intermittent olfactory stimulations. Behavioral results showed that, during the early period following Mn administration, spontaneous motor activ... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479437 Fri, 04 Nov 2011 04:00:00 +0100 5479437 http://www.medworm.com/index.php?rid=5479435&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003419%2Fabstract%3Frss%3Dyes Abstract: Functional magnetic resonance imaging (fMRI) at high magnetic field strength can suffer from serious degradation of image quality because of motion and physiological noise, as well as spatial distortions and signal losses due to susceptibility effects. Overcoming such limitations is essential for sensitive detection and reliable interpretation of fMRI data. These issues are particularly problematic in studies of awake animals. As part of our initial efforts to study functional brain activations in awake, behaving monkeys using fMRI at 4.7 T, we have developed acquisition and analysis procedures to improve image quality with encouraging results.We evaluated the influence of two main variables on image quality. First, we show how important the level of behavioral training is for ob... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479435 Fri, 04 Nov 2011 04:00:00 +0100 5479435 http://www.medworm.com/index.php?rid=5461137&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003316%2Fabstract%3Frss%3Dyes Spatially resolved nuclear magnetic resonance (NMR) is an extremely powerful set of methods for research on living organisms; moreover, the number of methods is constantly increasing over time. However, the complexity of biological functions requires the integration of all possible available tools. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461137 Fri, 04 Nov 2011 04:00:00 +0100 5461137 http://www.medworm.com/index.php?rid=5339650&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003754%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339650 Sun, 23 Oct 2011 09:30:19 +0100 5339650 http://www.medworm.com/index.php?rid=5339649&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003730%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339649 Sun, 23 Oct 2011 09:30:19 +0100 5339649 http://www.medworm.com/index.php?rid=5479447&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002906%2Fabstract%3Frss%3Dyes Abstract: Malignant glioma is a rare tumor type characterized by prominent vascular proliferation. Antiangiogenic therapy with the monoclonal antibody bevacizumab is considered as a promising therapeutic strategy, although the effect on tumor vascularization is unclear. High-field susceptibility-weighted imaging (SWI) visualizes the microvasculature and may contribute to the investigation of antiangiogenic therapy responses in gliomas. We prospectively studied five adult malignant glioma patients treated with bevacizumab-containing regimens. In each patient, we performed three 7-T SWI and T1-weighted imaging investigations (baseline and 2 and 4 weeks after the start of bevacizumab treatment). In addition, we imaged a postmortem brain of a patient with glioblastoma using 7-T SWI and perform... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479447 Mon, 10 Oct 2011 04:00:00 +0100 5479447 http://www.medworm.com/index.php?rid=5479436&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002372%2Fabstract%3Frss%3Dyes In this study, group-independent component analysis was conducted for resting-state fMRI data, with slices acquired perpendicular to the long axis of the hippocampus, from eight subjects with aMCI and eight normal control subjects. Subjects with aMCI showed an increased DMN activity in middle cingulate cortex, medial prefrontal cortex and left inferior parietal cortex compared to the normal control group. Decreased DMN activity for the aMCI group compared to the normal control group was noted in lateral prefrontal cortex, left medial temporal lobe (MTL), left medial temporal gyrus, posterior cingulate cortex/retrosplenial cortex/precuneus and right angular gyrus. Although MTL volume difference between the two groups was not statistically significant, a decreased activity in left MTL was ob... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479436 Mon, 10 Oct 2011 04:00:00 +0100 5479436 http://www.medworm.com/index.php?rid=5461139&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002803%2Fabstract%3Frss%3Dyes Abstract: High-resolution functional magnetic resonance imaging (fMRI) at high field (9.4 T) has been used to measure functional connectivity between subregions within the primary somatosensory (SI) cortex of the squirrel monkey brain. The hand–face region within the SI cortex of the squirrel monkey has been previously well mapped with functional imaging and electrophysiological and anatomical methods, and the orderly topographic map of the hand region is characterized by a lateral to medial representation of individual digits in four subregions of areas 3a, 3b, 1 and 2. With submillimeter resolution, we are able to detect not only the separate islands of activation corresponding to vibrotactile stimulations of single digits but also, in subsequent acquisitions, the degree of correlation... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461139 Mon, 10 Oct 2011 04:00:00 +0100 5461139 http://www.medworm.com/index.php?rid=5479443&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002931%2Fabstract%3Frss%3Dyes Abstract: Purpose: To investigate the feasibility of in vivo assessment of hepatic lipid composition using 3.0-T proton magnetic resonance spectroscopy (1H-MRS) in a steatotic rat model and compare it to histopathological and biochemical assessment.Materials and Methods: Hepatic steatosis was induced by feeding rats with a methionine/choline-deficient (MCD) diet for 1, 2, 3, 5 or 7 weeks (n=5 per group). At the end of the diet period, 1H-MRS of the liver was performed, and rats were sacrificed for histopathological and biochemical assessment of the liver. Spectra were acquired in a single voxel (1.2 cc) using a point-resolved spectroscopic sequence with TE/TR=35/2000 ms and 64 signal acquisitions. From the MR spectra, peak area ratios were calculated to estimate hepatic lipid composition.R... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479443 Thu, 22 Sep 2011 04:00:00 +0100 5479443 http://www.medworm.com/index.php?rid=5479445&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002918%2Fabstract%3Frss%3Dyes In this study, 104 consecutive patients (mean age, 67.7±9.4 years) underwent MRE using a 1.5-T MR scanner equipped with a cylindrical passive driver that was placed across the right chest wall for delivering vibrations. Axial gradient-echo images, which were automatically converted to elastograms that represented stiffness (kPa), were acquired using a continuous sinusoidal vibration of 60 Hz. Two raters independently placed a region of interest on the right lobe of the liver on the elastograms obtained before and after Gd-EOB-DTPA was administered. Liver stiffness was measured using these two elastograms and compared using a paired t test and correlation analysis. No significant difference was observed in liver stiffness before and after Gd-EOB-DTPA was administered (Rater 1, P=.1200; Rat... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479445 Wed, 21 Sep 2011 04:00:00 +0100 5479445 http://www.medworm.com/index.php?rid=5479442&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100292X%2Fabstract%3Frss%3Dyes Abstract: Diffusion tensor imaging (DTI) was performed on 25 patients with neurocysticercosis (NCC). The aim of this study was to investigate the changes in DTI measures during the evolutionary course of NCC lesions from vesicular to calcified stage in the brain. DTI measures were quantified from the NCC lesions of all patients. On the basis of conventional imaging findings, NCC lesions were classified into vesicular, vesicular colloidal, granular nodular and calcified stages. Significant inverse correlation was observed between the evolutionary stage of NCC lesion and mean diffusivity (MD; r=−0.748, P (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479442 Wed, 21 Sep 2011 04:00:00 +0100 5479442 http://www.medworm.com/index.php?rid=5479433&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002487%2Fabstract%3Frss%3Dyes Abstract: Magnetic resonance imaging of cortical lesions due to multiple sclerosis (MS) has been hampered by the lesions' small size and low contrast to adjacent, normal-appearing tissue. Knowing cortical lesion T1 and proton density (PD) would be highly beneficial for the process of developing and optimizing dedicated magnetic resonance (MR) sequences through computer modeling of MR tissue responses. Eight patients and seven healthy control subjects were scanned at 7 T using a series of inversion recovery turbo field echo scans with varying inversion times. Regions of interest were drawn in white matter, gray matter, cortical lesions, white matter lesions and cerebrospinal fluid. White matter and gray matter T1s were significantly higher in MS patients than in controls. Cortical and white... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479433 Wed, 21 Sep 2011 04:00:00 +0100 5479433 http://www.medworm.com/index.php?rid=5479432&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002839%2Fabstract%3Frss%3Dyes Abstract: The reconstruction of magnetic resonance (MR) images from the partial samples of their k-space data using compressed sensing (CS)-based methods has generated a lot of interest in recent years. To reconstruct the MR images, these techniques exploit the sparsity of the image in a transform domain (wavelets, total variation, etc.). In a recent work, it has been shown that it is also possible to reconstruct MR images by exploiting their rank deficiency. In this work, it will be shown that, instead of exploiting the sparsity of the image or rank deficiency alone, better reconstruction results can be achieved by combining transform domain sparsity with rank deficiency.To reconstruct an MR image using its transform domain sparsity and its rank deficiency, this work proposes a combined l... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479432 Wed, 21 Sep 2011 04:00:00 +0100 5479432 http://www.medworm.com/index.php?rid=5479431&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002499%2Fabstract%3Frss%3Dyes This study proposes simultaneous excitation of subslices with total width equal to the desired slice thickness, employing alternating Hadamard-encoded radiofrequency pulses coupled with incoherent addition of the subslices to achieve reduction of through-plane dephasing with minimal SNR loss but at the expense of a reduction in temporal resolution. Using a sensory task and hypercapnic challenge with breathholding (BH), results with two subslices per slice and a twofold reduction in temporal resolution show improved activation relative to a conventional acquisition. Average (eight subjects) T-scores in the BH task increased by 16% (P (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5479431 Wed, 21 Sep 2011 04:00:00 +0100 5479431 http://www.medworm.com/index.php?rid=5339651&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100289X%2Fabstract%3Frss%3Dyes In conclusion, the extremely high perfusion within an AVM could be successfully quantified using CASL. A shorter postlabeling delay time of w=800 ms seems to be more appropriate than a longer time of w=1200 ms because of possible inflow of unlabeled spins at the latter. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339651 Mon, 19 Sep 2011 04:00:00 +0100 5339651 http://www.medworm.com/index.php?rid=5461142&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002815%2Fabstract%3Frss%3Dyes Abstract: We have recently used combined electrostimulation, neurophysiology, microinjection and functional magnetic resonance imaging (fMRI) to study the cortical activity patterns elicited during stimulation of cortical afferents in monkeys. We found that stimulation of a site in lateral geniculate nucleus (LGN) increases the fMRI signal in the regions of primary visual cortex receiving input from that site, but suppresses it in the retinotopically matched regions of extrastriate cortex. Intracortical injection experiments showed that such suppression is due to synaptic inhibition. During these experiments, we have consistently observed activation of superior colliculus (SC) following LGN stimulation. Since LGN does not directly project to SC, the current study investigated the origin of... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461142 Thu, 15 Sep 2011 04:00:00 +0100 5461142 http://www.medworm.com/index.php?rid=5339660&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002840%2Fabstract%3Frss%3Dyes Abstract: Magnetic resonance imaging (MRI) studies of tissue engineered constructs prior to implantation clearly demonstrate the utility of the MRI technique for studying the bone formation process. To test the utility of our MRI protocols for explant studies, we present a novel test platform in which osteoblast-seeded scaffolds were implanted on the chorioallantoic membrane of a chick embryo. Scaffolds from the following experimental groups were examined by high-resolution MRI: (a) cell-seeded implanted scaffolds (CIM), (b) unseeded implanted scaffolds (UCIM), (c) cell-seeded scaffolds in static culture (CIV) and (d) unseeded scaffolds in static culture (UCIV). The reduction in water proton transverse relaxation times and the concomitant increase in water proton magnetization transfer rat... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339660 Thu, 15 Sep 2011 04:00:00 +0100 5339660 http://www.medworm.com/index.php?rid=5339657&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002864%2Fabstract%3Frss%3Dyes In this study, we assessed the influence of intravoxel fat signal on breast diffusion measures by comparing ADC values obtained using a diffusion-weighted single shot fast spin-echo sequence with and without fat suppression. The influence of breast density on ADC measures was also evaluated. ADC values were calculated for both tumor and normal fibroglandular tissue in a group of 21 women with diagnosed breast cancer. There were systematic underestimations of ADC for both tumor and normal breast tissue due to intravoxel contribution from fat signal on non–fat-suppressed DWI. This ADC underestimation was more pronounced for normal tissue values (mean difference=40%) than for tumors (mean difference=27%, P (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339657 Thu, 15 Sep 2011 04:00:00 +0100 5339657 http://www.medworm.com/index.php?rid=5461150&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002438%2Fabstract%3Frss%3Dyes Abstract: Information theory is a probabilistic framework that allows the quantification of statistical non-independence between signals of interest. In contrast to other methods used for this purpose, it is model free, i.e., it makes no assumption about the functional form of the statistical dependence or the underlying probability distributions. It thus has the potential to unveil important signal characteristics overlooked by classical data analysis techniques. In this review, we discuss how information theoretic concepts have been applied to the analysis of functional brain imaging data such as functional magnetic resonance imaging and magneto/electroencephalography. We review studies from a number of imaging domains, including the investigation of the brain's functional specialization... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461150 Wed, 14 Sep 2011 04:00:00 +0100 5461150 http://www.medworm.com/index.php?rid=5339655&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002451%2Fabstract%3Frss%3Dyes Abstract: This work utilises general numerical magnetic resonance imaging MRI simulations to predict the spatial specificity of the blood oxygenation level-dependent (BOLD) functional MRI (fMRI) signal. A Monte Carlo simulation approach was utilized on a microvascular structure consisting of randomly oriented cylinders representing blood vessels. This framework was employed to numerically investigate the spatial specificity, defined as ratio of pial vessel to microvascular signal, of the spin echo BOLD fMRI signal as a function of field strength, echo time and tissue types [grey matter (GM) and cerebrospinal fluid (CSF), respectively]. Spatial specificity of spin echo BOLD fMRI signal was determined to increase with field strength up to 16 T and with maximal specificity for echo time short... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339655 Wed, 14 Sep 2011 04:00:00 +0100 5339655 http://www.medworm.com/index.php?rid=5213317&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100316X%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213317 Tue, 13 Sep 2011 10:48:58 +0100 5213317 http://www.medworm.com/index.php?rid=5213316&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11003158%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213316 Tue, 13 Sep 2011 10:48:58 +0100 5213316 http://www.medworm.com/index.php?rid=5461144&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002396%2Fabstract%3Frss%3Dyes Abstract: A number of different methods have been developed in order to detect the spreading of neuronal currents by means of noninvasive imaging techniques. However, all of these are subjected to limitations in the temporal or spatial resolution. A new approach of neuronal current detection is based on the use of low-field nuclear magnetic resonance (LF-NMR) that records brain activity directly. In the following, we describe a phantom study in order to assess the feasibility of neuronal current detection using LF-NMR. In addition to that, necessary preliminary subject studies examining somatosensory evoked neuronal currents are presented. During the phantom study, the influences of two different neuronal time signals on 1H-NMR signals were observed. The measurements were carried out by us... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461144 Mon, 12 Sep 2011 04:00:00 +0100 5461144 http://www.medworm.com/index.php?rid=5339664&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100244X%2Fabstract%3Frss%3Dyes Abstract: Manganese (Mn)-enhanced magnetic resonance imaging (MEMRI) is an emerging technique for visualizing neuronal pathways and mapping brain activity modulation in animal models. Spatial and intensity normalizations of MEMRI images acquired from different subjects are crucial steps as they can influence the results of groupwise analysis. However, no commonly accepted procedure has yet emerged. Here, a normalization method is proposed that performs both spatial and intensity normalizations in a single iterative process without the arbitrary choice of a reference image. Spatial and intensity normalizations benefit from this iterative process. On one hand, spatial normalization increases the accuracy of region of interest (ROI) positioning for intensity normalization. On the other hand, ... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339664 Mon, 12 Sep 2011 04:00:00 +0100 5339664 http://www.medworm.com/index.php?rid=5339663&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002475%2Fabstract%3Frss%3Dyes Abstract: Constrained independent component analysis (CICA) eliminates the order ambiguity of standard ICA by incorporating prior information into the learning process to sort the components intrinsically. However, the original CICA (OCICA) and its variants depend on a learning rate, which is not easy to be tuned for various applications. To solve this problem, two learning-rate-free CICA algorithms were derived in this paper using the fixed-point learning concept. A complete stability analysis was provided for the proposed methods, which also made a correction to the stability analysis given to OCICA. Variations for adding constraints either to the components or to the associated time courses were derived too. Using synthetic data, the proposed methods yielded a better stability and a bet... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339663 Mon, 12 Sep 2011 04:00:00 +0100 5339663 http://www.medworm.com/index.php?rid=5339662&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002463%2Fabstract%3Frss%3Dyes Abstract: In magnetic resonance imaging, the parallel acquisition of subsampled spatial frequencies from an array of multiple receiver coils has become a common means of reducing data acquisition time. SENSitivity Encoding (SENSE) is a popular parallel image reconstruction model that uses a complex-valued least squares estimation process to unfold aliased images. In this article, the linear mathematical framework derived in Rowe et al. [J Neurosci Meth 159 (2007) 361–369] is built upon to perform image reconstruction with subsampled data acquired from multiple receiver coils, where the SENSE model is represented as a real-valued isomorphism. A statistical analysis is performed of the various image reconstruction operators utilized in the SENSE model, with an emphasis placed on the effect... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339662 Mon, 12 Sep 2011 04:00:00 +0100 5339662 http://www.medworm.com/index.php?rid=5339659&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002888%2Fabstract%3Frss%3Dyes Conclusion: For assessment of hypervascular HCC, DWI in combination with dynamic MRI provides comparable or slightly better information compared with the combination of dynamic and SPIO-enhanced MRI. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339659 Mon, 12 Sep 2011 04:00:00 +0100 5339659 http://www.medworm.com/index.php?rid=5339658&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002876%2Fabstract%3Frss%3Dyes In conclusion, a comprehensive MRI exam was developed for assessing patients with HFNEF. Heart failure with normal EF is associated with impaired LV diastolic function and significant ventricular and aortic stiffening. The degree of aortic stiffness involvement suggests reduced aortic compliance as a major factor in HFNEF. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339658 Mon, 12 Sep 2011 04:00:00 +0100 5339658 http://www.medworm.com/index.php?rid=5339656&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002827%2Fabstract%3Frss%3Dyes Conclusion: The MURPS method enables temperature monitoring over multiple slices without loss of temporal resolution compared with single-slice imaging and, if combined with multishot EPI, enables volume temperature monitoring in moving organs. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339656 Mon, 12 Sep 2011 04:00:00 +0100 5339656 http://www.medworm.com/index.php?rid=5339654&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002414%2Fabstract%3Frss%3Dyes Abstract: Respiratory motion and capnometry monitoring were performed during blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) of the brain while a series of paced hyperventilation tasks were performed that caused significant hypocapnia. Respiration volume per time (RVT) and end-tidal carbon dioxide (ETCO2) were determined and compared for their ability to explain BOLD contrast changes in the data. A 35% decrease in ETCO2 was observed along with corresponding changes in RVT. A best-fit ETCO2 response function, with an average initial peak delay time of 12 s, was empirically determined. ETCO2 data convolved with this response function was more strongly and prevalently correlated to BOLD signal changes than RVT data convolved with the corresponding respiration ... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339654 Mon, 12 Sep 2011 04:00:00 +0100 5339654 http://www.medworm.com/index.php?rid=5339652&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002426%2Fabstract%3Frss%3Dyes Abstract: Diffusion tensor imaging (DTI) was used to investigate the involvement of brain white matter in Williams syndrome (WS), a genetic neurodevelopmental disorder. Whole-brain DTIs were obtained from 16 young adults with WS and 16 normal controls. A voxel-based analysis was performed to compare fractional anisotropy (FA) values between the two groups. A tract-based analysis was also performed to compare FA values between the two groups along two major white matter tracts that pass through the external capsule: the uncinate and inferior fronto-occipital fasciculi. Several regions of both increased and decreased FA were found within major white matter tracts that connect functional regions that have previously been implicated in the cognitive and neurological symptoms of the syndrome. T... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339652 Mon, 12 Sep 2011 04:00:00 +0100 5339652 http://www.medworm.com/index.php?rid=5339661&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002359%2Fabstract%3Frss%3Dyes This study proposes an expectation–maximization (EM)-based curve evolution algorithm for segmentation of magnetic resonance brain images. In the proposed algorithm, the evolution curve is constrained not only by a shape-based statistical model but also by a hidden variable model from image observation. The hidden variable model herein is defined by the local voxel labeling, which is unknown and estimated by the expected likelihood function derived from the image data and prior anatomical knowledge. In the M-step, the shapes of the structures are estimated jointly by encoding the hidden variable model and the statistical prior model obtained from the training stage. In the E-step, the expected observation likelihood and the prior distribution of the hidden variables are estimated. In expe... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339661 Mon, 29 Aug 2011 04:00:00 +0100 5339661 http://www.medworm.com/index.php?rid=5339653&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002360%2Fabstract%3Frss%3Dyes Abstract: Modeling of water diffusion in white matter is useful for revealing microstructure of the brain tissue and hence diagnosis and evaluation of white matter diseases. Researchers have modeled diffusion in white matter using mathematical and mechanical analysis at the cellular level. However, less work has been devoted to evaluate these models using macroscopic real data such as diffusion tensor magnetic resonance imaging (DTMRI) data. DTMRI is a noninvasive tool for evaluating white matter microstructure by measuring random motion of water molecules referred to as diffusion. It reflects directional information of microscopic structures such as fibers. Thus, it is applicable for evaluation and modification of mathematical models of white matter. Nevertheless, a realistic relation bet... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5339653 Mon, 29 Aug 2011 04:00:00 +0100 5339653 http://www.medworm.com/index.php?rid=5213329&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002384%2Fabstract%3Frss%3Dyes Abstract: Four different techniques for 3-T whole-heart coronary magnetic resonance angiography (MRA) using free-breathing three-dimensional segmented parallel imaging and adiabatic T2-preparation were assessed. Coronary MRA at 3 T is improved by shortening the acquisition window more than employing the highest spatial resolution. Double-oblique whole-heart acquisitions result in better overall image quality and allow for better delineation of the left anterior descending coronary artery. It is possible to attain shorter acquisition windows and a smaller voxel size at 3 T than previously reported at 1.5 T. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213329 Mon, 29 Aug 2011 04:00:00 +0100 5213329 http://www.medworm.com/index.php?rid=5213326&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002335%2Fabstract%3Frss%3Dyes Conclusions: Vascular endothelial growth factor expression in plasma and CSF in the CSF metastasis model was higher than in normal tissues. Therefore, DCE-MRI reliably indicated VEGF expression in the rabbit CSF metastasis model. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213326 Thu, 25 Aug 2011 04:00:00 +0100 5213326 http://www.medworm.com/index.php?rid=5213319&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002347%2Fabstract%3Frss%3Dyes This study presents and validates a theoretical model for estimating the number of double bonds in triglyceride molecules using magnetic resonance imaging. The model enables reliable estimation of the number of double bonds from a small number of time points, as are typically acquired with chemical shift imaging. Prior knowledge from the US Department of Agriculture (USDA) is used to constrain the properties of triglyceride. Validation in oil phantoms shows agreement between the measured number of double bonds and USDA reference values (correlation 0.95, significance P=.0003, slope 0.95±0.31, intercept 0.08±1.24). Feasibility in a human subject was demonstrated using a long breath-hold (43 s) scan. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213319 Thu, 25 Aug 2011 04:00:00 +0100 5213319 http://www.medworm.com/index.php?rid=5150136&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100261X%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150136 Wed, 24 Aug 2011 22:00:04 +0100 5150136 http://www.medworm.com/index.php?rid=5150135&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002608%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150135 Wed, 24 Aug 2011 22:00:04 +0100 5150135 http://www.medworm.com/index.php?rid=5213333&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002323%2Fabstract%3Frss%3Dyes Abstract: The misunderstanding of the labeling for an “MR conditional” respiratory ventilator system resulted in the placement of this device, which had substantial ferromagnetic components, too close to a 3-T magnetic resonance (MR) system, causing a projectile incident. Magnetic resonance imaging health care professionals should be aware of the potentially dangerous consequences when such medical devices that have Food and Drug Administration-approved MR conditional labeling are brought into the MR system room. Recommendations to prevent future incidents are provided herein. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213333 Mon, 22 Aug 2011 04:00:00 +0100 5213333 http://www.medworm.com/index.php?rid=5213323&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100227X%2Fabstract%3Frss%3Dyes Abstract: Muscle volume measurements are essential for an array of diseases ranging from peripheral arterial disease, muscular dystrophies, neurological conditions to sport injuries and aging. In the clinical setting, muscle volume is not routinely measured due to the lack of standardized ways for its repeatable quantification. In this paper, we present magnetic resonance muscle quantification (MRMQ), a method for the automatic quantification of thigh muscle volume in magnetic resonance imaging (MRI) scans. MRMQ integrates a thigh segmentation and nonuniform image gradient correction step, followed by feature extraction and classification. The classification step leverages prior probabilities, introducing prior knowledge to a maximum a posteriori classifier. MRMQ was validated on 344 slice... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213323 Mon, 22 Aug 2011 04:00:00 +0100 5213323 http://www.medworm.com/index.php?rid=5213321&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002293%2Fabstract%3Frss%3Dyes The objective of this work was to evaluate the diagnostic performance of the intravoxel incoherent motion (IVIM) model to differentiate between healthy and malignant prostate tissue.Materials and Methods: Regions of interest were drawn in healthy and cancerous tissue of 13 patients with histologically proven prostate carcinoma and fitted to a monoexponential model [yielding the apparent diffusion coefficient (ADC)] and the IVIM signal equation (yielding the perfusion fraction f, the diffusion constant D and the pseudodiffusion coefficient of perfusion D⁎). Parameter maps were calculated for all parameters.Results: The ADC, D and f were significantly (P (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213321 Mon, 22 Aug 2011 04:00:00 +0100 5213321 http://www.medworm.com/index.php?rid=5213318&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002311%2Fabstract%3Frss%3Dyes Abstract: Hyperpolarized technology utilizing dynamic nuclear polarization has enabled rapid and high-sensitivity measurements of 13C metabolism in vivo. The most commonly used in vivo agent for hyperpolarized 13C metabolic imaging thus far has been [1-13C]pyruvate. In preclinical studies, not only is its uptake detected, but also its intracellular enzymatic conversion to metabolic products including [1-13C]lactate and [1-13C]alanine. However, the ratio of 13C-lactate/13C-pyruvate measured in this data does not accurately reflect cellular values since much of the [1-13C]pyruvate is extracellular depending on timing, vascular properties, and extracellular space and monocarboxylate transporter activity. In order to measure the relative levels of intracellular pyruvate and lactate, in this pr... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213318 Mon, 22 Aug 2011 04:00:00 +0100 5213318 http://www.medworm.com/index.php?rid=5213322&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100230X%2Fabstract%3Frss%3Dyes Conclusion: Electroacupuncture stimulation induced different power fluctuation patterns related to GB37 and KI8. We suggest that these findings might be attributed to the specific function action of these acupoints. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213322 Wed, 17 Aug 2011 04:00:00 +0100 5213322 http://www.medworm.com/index.php?rid=5461138&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001433%2Fabstract%3Frss%3Dyes Abstract: Glutamate plays a double role in 13C-nuclear magnetic resonance (NMR) spectroscopic determination of glucose metabolism in the brain. Bidirectional exchange between initially unlabeled glutamate and labeled α-ketoglutarate, formed from pyruvate via pyruvate dehydrogenase (PDH), indicates the rate of energy metabolism in the tricarboxylic acid (VTCA) cycle in neurons (VPDH, n) and, with additional computation, also in astrocytes (VPDH, g), as confirmed using the astrocyte-specific substrate [13C]acetate. Formation of new molecules of glutamate during increased glutamatergic activity occurs only in astrocytes by combined pyruvate carboxylase (VPC) and astrocytic PDH activity. VPDH, g accounts for ∼15% of total pyruvate metabolism in the brain cortex, and VPC accounts for another... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461138 Mon, 08 Aug 2011 04:00:00 +0100 5461138 http://www.medworm.com/index.php?rid=5213334&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001822%2Fabstract%3Frss%3Dyes In the above article, Equation (1) was incorrect. The corrected Equation (1) is: The authors regret any inconvenience this error may have caused. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213334 Mon, 01 Aug 2011 04:00:00 +0100 5213334 http://www.medworm.com/index.php?rid=5213324&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002281%2Fabstract%3Frss%3Dyes Abstract: Glaucoma is an optic neuropathy affecting the entire visual system. The understanding of the glaucoma mechanism and causes remains unresolved. Diffusion tensor imaging (DTI) has been used to analyze the optic nerve and optic radiation showing global fiber abnormalities associated with glaucoma. Nevertheless, the complex structure of the optic radiation and the limitations of DTI make the localization of the glaucoma effect a difficult task. The aim of this work is to establish a framework for the determination of the local changes of the optic radiation due to glaucoma using DTI. The proposed system utilizes a semiautomated algorithm to produce an efficient identification of the optic radiation. Segmented optic radiations are transformed to a unified space using shape-based nonri... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213324 Mon, 01 Aug 2011 04:00:00 +0100 5213324 http://www.medworm.com/index.php?rid=5213320&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001846%2Fabstract%3Frss%3Dyes Conclusion: Corrected liver-enhancement ratio with gadoxetic acid-enhanced MRI is correlated to the stage of liver fibrosis. APRI, however, has greater reliability for predicting severe fibrosis and cirrhosis than does the imaging-based fibrosis marker tested in this study. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213320 Wed, 20 Jul 2011 04:00:00 +0100 5213320 http://www.medworm.com/index.php?rid=5461145&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001354%2Fabstract%3Frss%3Dyes Abstract: Combining electrical stimulation with fMRI (esfMRI) has proven to be an important tool to study the global effects of electrical stimulation on neural networks in the brain. Here we extend our previous studies to stimulating the upper superior temporal sulcus (STS) in the anesthetized monkey. Our results show that stimulating area V5/MT and surrounding areas leads to positive BOLD responses in the majority of cortical areas known to receive direct/monosynaptic connections from the stimulation site. We confirm our previous results from stimulating primary visual cortex that the propagation of electrically induced activity is limited in its transsynaptic propagation to the first synapse also for extrastriate areas. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461145 Fri, 15 Jul 2011 04:00:00 +0100 5461145 http://www.medworm.com/index.php?rid=5213332&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001858%2Fabstract%3Frss%3Dyes Conclusions: Nitric oxide can be administered through 35 ft. of standard oxygen tubing without significantly affecting dose delivery. This technique has potential application in patients with right-sided structural heart disease for determination of dynamic physiological changes. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213332 Mon, 27 Jun 2011 04:00:00 +0100 5213332 http://www.medworm.com/index.php?rid=5213330&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001834%2Fabstract%3Frss%3Dyes Abstract: Purpose: The aim of this study was to develop a targeted volumetric radiofrequency field (B1+) mapping technique to provide region-of-interest B1+ information.Materials and Methods: Targeted B1+ maps were acquired using three-dimensional (3D) reduced field-of-view (FOV) inner-volume turbo spin echo-catalyzed double-angle method (DAM). Targeted B1+ maps were compared with full-FOV B1+ maps acquired using 3D catalyzed DAM in a phantom and in the brain of a healthy volunteer. In addition, targeted volumetric abdomeninal B1+ mapping was demonstrated in the abdomen of another healthy volunteer.Results: The targeted reduced-FOV images demonstrated no aliasing artifacts in all experiments. Close match between targeted B1+ map and reference full-FOV B1+ map in the same region was observe... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213330 Mon, 27 Jun 2011 04:00:00 +0100 5213330 http://www.medworm.com/index.php?rid=5213328&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001378%2Fabstract%3Frss%3Dyes Abstract: Accurate depiction of the vessels of the lower leg, foot or hand benefits from suppression of bright MR signal from lipid (such as bone marrow) and long-T1 fluid (such as synovial fluid and edema). Signal independence of blood flow velocities, good arterial/muscle contrast and arterial/venous separation are also desirable. The high SNR, short scan times and flow properties of balanced steady-state free precession (SSFP) make it an excellent candidate for flow-independent angiography. In this work, a new magnetization-prepared 3D SSFP sequence for flow-independent peripheral angiography is presented. The technique combines a number of component techniques (phase-sensitive fat detection, inversion recovery, T2-preparation and square-spiral phase-encode ordering) to achieve high-con... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213328 Mon, 27 Jun 2011 04:00:00 +0100 5213328 http://www.medworm.com/index.php?rid=5213327&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100186X%2Fabstract%3Frss%3Dyes In this study, the displacement processes were observed as gaseous or supercritical CO2 was injected into n-decane-saturated glass beads packs using a 400-MHz magnetic resonance imaging (MRI) system. Two-dimensional images of oil distribution in the vertical median section were obtained using a spin-echo pulse sequence. Gas channeling and viscous fingering appeared obviously in immiscible gaseous CO2 displacement. A piston-like displacement front was detected in miscible supercritical CO2 displacement that provided high sweep efficiency. MRI images were processed with image intensity analysis methods to obtain the saturation profiles. Final oil residual saturations and displacement coefficients were also estimated using this imaging intensity analysis. It was proved that miscible displacem... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213327 Mon, 27 Jun 2011 04:00:00 +0100 5213327 http://www.medworm.com/index.php?rid=5150150&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001317%2Fabstract%3Frss%3Dyes Conclusion: This study confirms that it is possible to build such small-looped MRIG at 0.014 in. for intravascular 3.0-T MR imaging. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150150 Sun, 26 Jun 2011 23:00:00 +0100 5150150 http://www.medworm.com/index.php?rid=5150140&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001494%2Fabstract%3Frss%3Dyes Abstract: In diffusion magnetic resonance imaging with high-angular-resolution diffusion imaging, a set of techniques has become available that allows better acquisition and representation of multidirectional diffusion profiles, e.g., in voxels with crossing, branching and kissing fibers. The poor spatial resolution and low signal-to-noise ratio of the data, particularly when acquired under clinical conditions, prevent tractography algorithms from reliably reconstructing complex white matter structures. With cone-beam regularization, an intervoxel smoothing approach has been described, which, in this article, is refined and adapted to fibers with subvoxel bending. By introducing the concept of asymmetric orientation distribution functions (aODFs), we are able to sharpen diffusion profiles ... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150140 Sun, 26 Jun 2011 23:00:00 +0100 5150140 http://www.medworm.com/index.php?rid=4948397&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100213X%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948397 Tue, 21 Jun 2011 01:40:50 +0100 4948397 http://www.medworm.com/index.php?rid=4948396&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11002049%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948396 Tue, 21 Jun 2011 01:40:50 +0100 4948396 http://www.medworm.com/index.php?rid=5461147&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001809%2Fabstract%3Frss%3Dyes Abstract: Functional magnetic resonance imaging (fMRI) experiments with awake nonhuman primates (NHPs) have recently seen a surge of applications. However, the standard fMRI analysis tools designed for human experiments are not optimal for NHP data collected at high fields. One major difference is the experimental setup. Although real head movement is impossible for NHPs, MRI image series often contain visible motion artifacts. Animal body movement results in image position changes and geometric distortions. Since conventional realignment methods are not appropriate to address such differences, algorithms tailored specifically for animal scanning become essential. We have implemented a series of high-field NHP specific methods in a software toolbox, fMRI Sandbox (http://kyb.tuebingen.mpg.d... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461147 Mon, 13 Jun 2011 04:00:00 +0100 5461147 http://www.medworm.com/index.php?rid=5213325&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001445%2Fabstract%3Frss%3Dyes Abstract: The study was aimed to test the feasibility of utilizing an algorithmically determinable stable fiber mass (SFM) map obtained by an unsupervised principal eigenvector field segmentation (PEVFS) for automatic delineation of 18 white matter (WM) tracts: (1) corpus callosum (CC), (2) tapetum (TP), (3) inferior longitudinal fasciculus (ILF), (4) uncinate fasciculus (UNC), (5) inferior fronto-occipital fasciculus (IFO), (6) optic pathways (OP), (7) superior longitudinal fasciculus (SLF), (8) arcuate fasciculus (AF), (9) fornix (FX), (10) cingulum (CG), (11) anterior thalamic radiation (ATR), (12) superior thalamic radiation (STR), (13) posterior thalamic radiation (PTR), (14) corticospinal/corticopontine tract (CST/CPT), (15) medial lemniscus (ML), (16) superior cerebellar peduncle (S... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213325 Mon, 13 Jun 2011 04:00:00 +0100 5213325 http://www.medworm.com/index.php?rid=5150153&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001305%2Fabstract%3Frss%3Dyes Abstract: High-pass filtering is required for the removal of background field inhomogeneities in magnetic resonance phase images. This high-pass filtering smooths across boundaries between areas with large differences in phase. The most prominent boundary is the surface of the brain where areas with large phase values inside the brain are located close to areas outside the brain where the phase is, on average, zero. Cortical areas, which are of great interest in brain MRI, are therefore often degraded by high-pass filtering. Here, we propose the use of the bilateral filter for the high-pass filtering step. The bilateral filter is essentially a Gaussian filter that stops smoothing at boundaries. We show that the bilateral filter improves image quality at the brain's surface, without sacrifi... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150153 Sun, 12 Jun 2011 23:00:00 +0100 5150153 http://www.medworm.com/index.php?rid=5461143&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001470%2Fabstract%3Frss%3Dyes Abstract: Many statistical models of coupling between time changes of the band-limited power of neural signals and functional magnetic resonance imaging Blood Oxygenation Level Dependent (BOLD) signal time changes rely on linear convolution. The effect of nonlinear behaviors in single-trial relationships between neural signals and BOLD responses is rarely tested and included in models. Here we investigate whether using a static nonlinearity improves the prediction of single-trial BOLD responses from neural signals. A static nonlinearity is a nonlinear transformation of the convolution of neural responses which is implemented by the same nonlinear function for all time points. We evaluated this approach by applying it to simultaneous recordings of functional magnetic resonance imaging BOLD ... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461143 Mon, 06 Jun 2011 04:00:00 +0100 5461143 http://www.medworm.com/index.php?rid=5213331&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001482%2Fabstract%3Frss%3Dyes Abstract: The ratio of inorganic phosphate to phosphocreatine (Pi:PCr) is a validated marker of mitochondrial function in human muscle. The magnetic resonance imaging rapid acquisition with relaxation enhancement (RARE) pulse sequence can acquire phosphorus-31 (31P) images with higher spatial and temporal resolution than traditional spectroscopic methods, which can then be used to create Pi:PCr ratio maps of muscle regions. While the 31P RARE method produces images that reflect the content of the 31P metabolites, it has been limited to producing an image of only one chemical shift in a scan. This increases the scan time required to acquire images of multiple chemical shifts as well as the likelihood of generating inaccurate Pi:PCr maps due to gross motion. This work is a preliminary study ... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5213331 Mon, 06 Jun 2011 04:00:00 +0100 5213331 http://www.medworm.com/index.php?rid=5150147&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001457%2Fabstract%3Frss%3Dyes Abstract: Venous thrombus is subsequently organized and replaced by fibrous connective tissue. However, the sequential changes in venous thrombi are not reliably detected by current noninvasive diagnostic techniques. The purpose of this study is to reveal whether magnetic resonance (MR) can detect venous thrombus, define thrombus age and predict thrombolytic responses. Thrombus in the rabbit jugular vein was imaged with a 1.5-T MR system at 4 h and at 1, 2 and 4 weeks using three-dimensional (3D) fast asymmetric spin echo T2-weighted (T2W) and 3D-gradient echo T1-weighted (T1W) sequences. The jugular veins were histologically assessed at each time point. Magnetic resonance imaging (MRI) was also performed in vivo before and 30 min after tissue plasminogen activator (t-PA) administration. T... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150147 Sun, 05 Jun 2011 23:00:00 +0100 5150147 http://www.medworm.com/index.php?rid=5150146&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001421%2Fabstract%3Frss%3Dyes In conclusion, each technique has its own advantages and disadvantages. The two techniques result in similar measurements, although the QA method is more subjective due to its dependency on operator intervention. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150146 Sun, 05 Jun 2011 23:00:00 +0100 5150146 http://www.medworm.com/index.php?rid=5150139&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001469%2Fabstract%3Frss%3Dyes Abstract: Undersampling k-space is an effective way to decrease acquisition time for MRI. However, aliasing artifacts introduced by undersampling may blur the edges of magnetic resonance images, which often contain important information for clinical diagnosis. Moreover, k-space data is often contaminated by the noise signals of unknown intensity. To better preserve the edge features while suppressing the aliasing artifacts and noises, we present a new wavelet-based algorithm for undersampled MRI reconstruction. The algorithm solves the image reconstruction as a standard optimization problem including a ℓ2 data fidelity term and ℓ1 sparsity regularization term. Rather than manually setting the regularization parameter for the ℓ1 term, which is directly related to the threshold, an aut... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150139 Sun, 05 Jun 2011 23:00:00 +0100 5150139 http://www.medworm.com/index.php?rid=5150154&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001020%2Fabstract%3Frss%3Dyes Abstract: The authors report a case of unilateral xanthogranulomatous pyelonephritis, associated with chronic lithiasis studied by standard clinical magnetic resonance imaging protocol and diffusion tensor imaging (DTI). Maps of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) and tractography were reconstructed on both healthy and pathologic kidney. ADC and FA values are in agreement with the literature. Tractography reconstruction of tubular renal architecture was confirmed by histology. This result suggests the potential ability of DTI to detect structural alterations in the architecture of the kidney, as noninvasive tool, preceding the onset of clinical-laboratory alterations. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150154 Thu, 26 May 2011 23:00:00 +0100 5150154 http://www.medworm.com/index.php?rid=5150152&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000853%2Fabstract%3Frss%3Dyes Conclusion: We presented the active contour model with shape prior for extracting the cerebellum from T1-weighted brain MR images. The proposed method yielded a robust and accurate segmentation result. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150152 Thu, 26 May 2011 23:00:00 +0100 5150152 http://www.medworm.com/index.php?rid=5150148&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001408%2Fabstract%3Frss%3Dyes Conclusion: Due to its higher detection rate of subcentimeter lesions, DWI could be considered complementary to dynamic MRI in the diagnosis of intrahepatic metastases of HCCs. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150148 Thu, 26 May 2011 23:00:00 +0100 5150148 http://www.medworm.com/index.php?rid=5150145&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001391%2Fabstract%3Frss%3Dyes In this study, we sought to investigate the functional correlations throughout the entire brain following acupuncture at acupoint ST36 (ACUP) in comparison with acupuncture at nearby nonacupoint (SHAM). We divided the whole brain into 90 regions and constructed functional brain network for each condition. Then we examined the network hubs and identified statistically significant differences in functional correlations between the two conditions. Following ACUP, but not SHAM, the limbic/paralimbic regions such as the amygdala, hippocampus and anterior cingulate gyrus emerged as network hubs. For direct comparisons, increased correlations for ACUP compared to SHAM were primarily related with the limbic/paralimbic and subcortical regions such as the insula, amygdala, anterior cingulate gyrus, ... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150145 Thu, 26 May 2011 23:00:00 +0100 5150145 http://www.medworm.com/index.php?rid=5150141&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000695%2Fabstract%3Frss%3Dyes Abstract: Dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) allows the noninvasive assessment of brain hemodynamics alterations by quantifying, via deconvolution, the cerebral blood flow (CBF) and mean transit time (MTT). Singular value decomposition (SVD) and block-circulant SVD (cSVD) are the most widely adopted deconvolution method, although they bear some limitations, including unphysiological oscillations in the residue function and bias in the presence of delay and dispersion between the tissue and the arterial input function. A nonlinear stochastic regularization (NSR) has been proposed, which performs better than SVD and cSVD on simulated data both in the presence and absence of dispersion. Moreover, NSR allows to quantify the dispersion level. Here, cSVD and NSR... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150141 Thu, 26 May 2011 23:00:00 +0100 5150141 http://www.medworm.com/index.php?rid=5150137&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100141X%2Fabstract%3Frss%3Dyes Abstract: Positive contrast imaging methods produce enhanced signal at large magnetic field gradient in magnetic resonance imaging. Several postprocessing algorithms, such as susceptibility gradient mapping and phase gradient mapping methods, have been applied for positive contrast generation to detect the cells targeted by superparamagnetic iron oxide nanoparticles. In the phase gradient mapping methods, smoothness condition has to be satisfied to keep the phase gradient unwrapped. Moreover, there has been no discussion about the truncation artifact associated with the algorithm of differentiation that is performed in k-space by the multiplication with frequency value. In this work, phase gradient methods are discussed by considering the wrapping problem when the smoothness condition is n... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150137 Thu, 26 May 2011 23:00:00 +0100 5150137 http://www.medworm.com/index.php?rid=4857674&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001639%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857674 Wed, 25 May 2011 18:09:25 +0100 4857674 http://www.medworm.com/index.php?rid=4857673&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001627%2Fabstract%3Frss%3Dyes (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857673 Wed, 25 May 2011 18:09:25 +0100 4857673 http://www.medworm.com/index.php?rid=5461149&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001366%2Fabstract%3Frss%3Dyes Abstract: The departure from purely mono-exponential decay of the signal, as observed from brain tissue following a diffusion-sensitized sequence, has prompted the search for alternative models to characterize these unconventional water diffusion dynamics. Several approaches have been proposed in the last few years. While multi-exponential models have been applied to characterize brain tissue, several unresolved controversies about the interpretations of the results have motivated the search for alternative models that do not rely on the Gaussian diffusion hypothesis. In this brief review, diffusional kurtosis imaging (DKI) and anomalous diffusion imaging (ADI) techniques are addressed and compared with diffusion tensor imaging. Theoretical and experimental issues are briefly described to ... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461149 Wed, 25 May 2011 04:00:00 +0100 5461149 http://www.medworm.com/index.php?rid=5461141&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001329%2Fabstract%3Frss%3Dyes Abstract: Estimation of magnetization transfer (MT) parameters in vivo can be compromised by an inability to drive the magnetization to a steady state using allowable levels of radiofrequency (RF) irradiation, due to safety concerns (tissue heating and specific absorption rate (SAR)). Rather than increasing the RF duration or amplitude, here we propose to circumvent the SAR limitation by sampling the formation of the steady state in separate measurements made with the magnetization initially along the -z and +z axis of the laboratory frame, i.e. with or without an on-resonance inversion pulse prior to the off-resonance irradiation. Results from human brain imaging demonstrate that this choice provides a tremendous benefit in the fitting procedure used to estimate MT parameters. The resulti... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461141 Wed, 25 May 2011 04:00:00 +0100 5461141 http://www.medworm.com/index.php?rid=5150151&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100138X%2Fabstract%3Frss%3Dyes Abstract: After obtaining experimental data of CO2 hydrate formation and dissociation in a porous medium using magnetic resonance imaging (MRI), the purpose of this study was to analyze the different dissociation rate of CO2 hydrate using two heating rates. Images were obtained by using a fast spin-echo sequence, and the field of view was set to 40×40×40 mm. The vessel pressure was monitored during hydrate formation and dissociation, which was used to compare with MRI mean intensity. The result indicated that the MRI could visualize hydrate formation and dissociation, and the MRI mean intensity of water was in good agreement with the vessel pressure changes. The hydrate formation and dissociation rates were also quantified using the MRI mean intensity of water. The experimental results s... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150151 Tue, 24 May 2011 23:00:00 +0100 5150151 http://www.medworm.com/index.php?rid=4948415&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001810%2Fabstract%3Frss%3Dyes In the above article, the authors omitted the following acknowledgement: Dr. Myerson would like to acknowledge the support from the Oxford NIHR Biomedical Research Centre programme. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948415 Thu, 19 May 2011 23:00:00 +0100 4948415 http://www.medworm.com/index.php?rid=5150149&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001342%2Fabstract%3Frss%3Dyes Conclusion: Cho/nCho of MRS, rCBV of MRP, and percent increase of MRI volume modeling provide the best discrimination of intra-axial metastatic tumor progression from radiation injury for their respective modalities. Cho/nCho and rCBV appear to have high specificities but low sensitivities. In contrast, percent volume increase of 65% can be a highly sensitive and moderately specific predictor for tumor progression after radiotherapy. Future incorporation of 65% volume increase as a pretest selection criterion may compensate for the low sensitivities of MRS and MRP. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150149 Sun, 15 May 2011 23:00:00 +0100 5150149 http://www.medworm.com/index.php?rid=5150144&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001330%2Fabstract%3Frss%3Dyes Abstract: A theoretical method for direct imaging of neural activity is presented here. It is based on a mechanism of random spin-lock along the magnetic field generated by active neurons. Lock conditions are fulfilled in a rotating frame whose properties are determined by the amplitude and frequency of neural field fluctuations. This technique can be implemented on scanners commonly used for blood oxygen level-dependent functional magnetic resonance imaging. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150144 Sun, 15 May 2011 23:00:00 +0100 5150144 http://www.medworm.com/index.php?rid=5150138&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001299%2Fabstract%3Frss%3Dyes Abstract: This works addresses the problem of reconstructing multiple T1- or T2-weighted images of the same anatomical cross section from partially sampled K-space data. Previous studies in reconstructing magnetic resonance (MR) images from partial samples of the K-space used compressed sensing (CS) techniques to exploit the spatial correlation of the images (leading to sparsity in wavelet domain). Such techniques can be employed to reconstruct the individual T1- or T2-weighted images. However, in the current context, the different images are not really independent; they are images of the same cross section and, hence, are highly correlated. We exploit the correlation between the images, along with the spatial correlation within the images to achieve better reconstruction results than expl... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150138 Sun, 15 May 2011 23:00:00 +0100 5150138 http://www.medworm.com/index.php?rid=4948408&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100097X%2Fabstract%3Frss%3Dyes Abstract: Cerebral microbleeds (CMBs) are increasingly being recognized as an important biomarker for neurovascular diseases. So far, all attempts to count and quantify them have relied on manual methods that are time-consuming and can be inconsistent. A technique is presented that semiautomatically identifies CMBs in susceptibility weighted images (SWI). This will both reduce the processing time and increase the consistency over manual methods. This technique relies on a statistical thresholding algorithm to identify hypointensities within the image. A support vector machine (SVM) supervised learning classifier is then used to separate true CMB from other marked hypointensities. The classifier relies on identifying features such as shape and signal intensity to identify true CMBs. The res... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948408 Sun, 15 May 2011 23:00:00 +0100 4948408 http://www.medworm.com/index.php?rid=4948405&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000804%2Fabstract%3Frss%3Dyes This study quantified the impact of the well-known physiologic noise correction algorithm RETROICOR applied to a pain functional magnetic resonance imaging (FMRI) experiment at two field strengths: 1.5 and 3.0 T. In the 1.5-T acquisition, there was an 8.2% decrease in time course variance (σ) and a 227% improvement in average model fit (increase in mean R2a). In the 3.0-T acquisition, significantly greater improvements were seen: a 10.4% decrease in σ and a 240% increase in mean R2a. End-tidal carbon dioxide data were also collected during scanning and used to account for low-frequency changes in cerebral blood flow; however, the impact of this correction was trivial compared to applying RETROICOR. Comparison between two implementations of RETROICOR demonstrated that oversampled physiolo... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948405 Sun, 15 May 2011 23:00:00 +0100 4948405 http://www.medworm.com/index.php?rid=4948404&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000713%2Fabstract%3Frss%3Dyes Abstract: Functional magnetic resonance imaging (fMRI) is a non-invasive neuroimaging tool that indirectly identifies areas of neural activity in the brain and more recently has been applied to the adult spinal cord (spinal fMRI). Spinal fMRI could clearly benefit pediatric populations as well. The purpose of this work was to characterize the response observed with spinal fMRI in the brainstem and cervical (C) spinal cord of awake, healthy children during thermal stimulation (17°C and 27°C) applied to the right hand. Functional MRI detected neuronal activity in the expected region of the spinal cord (C6 and C7) as well as in the brainstem and thalamus. The observed magnitudes of signal change of the responses to 17°C and 27°C were similar; however, the spatial distribution of active pi... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948404 Sun, 15 May 2011 23:00:00 +0100 4948404 http://www.medworm.com/index.php?rid=4948398&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000725%2Fabstract%3Frss%3Dyes Abstract: Diffusion tensor imaging (DTI) and advanced related methods such as diffusion spectrum and kurtosis imaging are limited by low signal-to-noise ratio (SNR) at conventional field strengths. DTI at 7 T can provide increased SNR; however, B0 and B1 inhomogeneity and shorter T2⁎ still pose formidable challenges. The purpose of this study was to quantify and compare SNR at 7 and 3 T for different parallel imaging reduction factors, R, and TE, and to evaluate SNRs influences on fractional anisotropy (FA) and apparent diffusion coefficient (ADC). We found that R>4 at 7 T and R≥2 at 3 T were needed to reduce geometric distortions due to B0 inhomogeneity. For these R at 7 T, SNR was 70–90 for b=0 s/mm2 and 22–28 for b=1000s/mm2 in central brain regions. SNR was lower at 3 T (40 for... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948398 Sun, 15 May 2011 23:00:00 +0100 4948398 http://www.medworm.com/index.php?rid=5461148&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001019%2Fabstract%3Frss%3Dyes In this study, we instructed healthy subjects to make deliberate brief ( (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461148 Tue, 10 May 2011 04:00:00 +0100 5461148 http://www.medworm.com/index.php?rid=5150142&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000920%2Fabstract%3Frss%3Dyes Abstract: Phased-array volume coils were used in conjunction with the phase rotation STEAM (PR-STEAM) spectroscopy technique to acquire very short TE data from the anterior cingulate gyrus at 3 T. A method for combining PR-STEAM data from multiple subcoils is presented. The data were acquired from seven healthy participants using PR-STEAM (repetition time/mixing time/echo time=3500/10/6.5 ms, 6 cm3, NEX=128, spectral width=2000 Hz, 2048 complex points, Δφ1=135°, Δφ2=22.5°, Δφ3=112.5° and ΔφADC=0°). In addition to the primary metabolites, LCModel fit results suggest that glutathione and glutamate can also be identified with Cramér–Rao lower bounds of 10% or less. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150142 Mon, 09 May 2011 23:00:00 +0100 5150142 http://www.medworm.com/index.php?rid=4948409&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100083X%2Fabstract%3Frss%3Dyes Abstract: Purpose: Quantification of cardiac magnetic resonance (CMR) myocardial perfusion remains time consuming since it requires manual interventions to compensate for motion. Thus, the aim of this study was to evaluate a semiautomated registration method.Materials and Methods: A rigid edge-based registration algorithm was applied on 10 patients who had rest and stress CMR acquisitions on three slice levels (apical, midventricular and basal slices). Registration efficiency was assessed qualitatively by evaluating the quality of k-means maps in terms of symmetry and heart structures identification before and after registration and quantitatively by estimating noise amplitude within the myocardium. Finally, residual registration errors were manually estimated.Results: Before registration,... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948409 Mon, 09 May 2011 23:00:00 +0100 4948409 http://www.medworm.com/index.php?rid=4948406&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000828%2Fabstract%3Frss%3Dyes Conclusions: The proposed quantitative method based on ΔSI measurement is accurate and applicable for real-time neuroimaging at 3.0 T. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948406 Mon, 09 May 2011 23:00:00 +0100 4948406 http://www.medworm.com/index.php?rid=4948403&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000774%2Fabstract%3Frss%3Dyes Abstract: The purpose of this study was to verify in healthy liver parenchyma the possible influence of age on DwI-related parameters: apparent diffusion coefficient (ADC), perfusion fraction (PF), diffusion and pseudodiffusion coefficient (D and D⁎). Forty healthy adult volunteers (age range 26–86 years), divided into four age groups, were prospectively submitted to a breath-hold magnetic resonance diffusion imaging (MR-DwI) (two b values, 0–300 and 0–1000 s/mm2). A smaller cohort of 16 subjects underwent a free-breath multi-b acquisition (16 b values, 0–750 s/mm2). Quantitative analysis was performed by two observers with manually defined regions of interest, on the most homogeneous portion of the right liver lobe. Individual and group statistical analysis of data was performed... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948403 Mon, 09 May 2011 23:00:00 +0100 4948403 http://www.medworm.com/index.php?rid=4948402&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000932%2Fabstract%3Frss%3Dyes Abstract: The uncertainty in the estimation of diffusion model parameters in diffusion tensor imaging (DTI) can be reduced by optimally selecting the diffusion gradient directions utilizing some prior structural information. This is beneficial for spinal cord DTI, where the magnetic resonance images have low signal-to-noise ratio and thus high uncertainty in diffusion model parameter estimation. Presented is a gradient optimization scheme based on D-optimality, which reduces the overall estimation uncertainty by minimizing the Rician Cramer-Rao lower bound of the variance of the model parameter estimates. The tensor-based diffusion model for DTI is simplified to a four-parameter axisymmetric DTI model where diffusion transverse to the principal eigenvector of the tensor is assumed isotropi... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948402 Mon, 09 May 2011 23:00:00 +0100 4948402 http://www.medworm.com/index.php?rid=4948401&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11001007%2Fabstract%3Frss%3Dyes In this study, the geometric relations of DW quantities are examined, in particular, the effects of Rician noise in the measured magnetic resonance signal. This geometric analysis is used to make theoretical predictions for selecting a b value to reduce the influence of noise. It is shown that the optimal b value for DTI studies in healthy human parenchyma is approximately b=1200 s mm−2, with a simple relation given as well for a given expected apparent diffusion coefficient. Monte-Carlo simulations on sets of realistic DTI measures are then performed, verifying the optimal DW for minimizing estimate errors. The effects of noise on various DTI parameters such as anisotropy indices (fractional anisotropy and scaled relative anisotropy), mean diffusivity, radial diffusivity, eigenvalues an... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948401 Mon, 09 May 2011 23:00:00 +0100 4948401 http://www.medworm.com/index.php?rid=4948399&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000798%2Fabstract%3Frss%3Dyes Abstract: Ultra-high-field clinical MRI scanners (e.g., 7 T and above) are becoming increasingly prevalent and can potentially enhance diagnostic ability through higher contrast, resolution and/or sensitivity. Diffusion-weighted MRI is a highly valued component in today's radiological exam and may benefit from the enhanced signal-to-noise ratio provided by high field with the appropriate imaging strategy. The most common diffusion pulse sequence readout (echo-planar imaging (EPI)) has been widely employed for in vivo human 7 T diffusion tensor imaging (DTI). In this article, we present results of brain DTI at 7 T with two diffusion-weighted imaging pulse sequence readouts: echo-planar imaging (EPI-DTI) and turbo spin echo (TSE-DTI). Results indicate that analogous coverage, quality and res... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948399 Mon, 09 May 2011 23:00:00 +0100 4948399 http://www.medworm.com/index.php?rid=4948400&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000919%2Fabstract%3Frss%3Dyes Abstract: The intravoxel incoherent motion (IVIM) theory provides a framework for the separation of perfusion and diffusion effects in diffusion-weighted imaging (DWI). To measure the three free IVIM parameters, DWIs with several diffusion weightings b must be acquired. To date, the used b value distributions are chosen heuristically and vary greatly among researchers. In this work, optimal b value distributions for the three parameter fit are determined using Monte-Carlo simulations for the measurement of a low, medium and high IVIM perfusion regime. The first 16 b values of a b value distribution, which was optimized to be appropriate for all three regimes, are {0, 40, 1000, 240, 10, 750, 90, 390, 170, 10, 620, 210, 100, 0, 530 and 970} in units of seconds per square meter. This distribu... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948400 Sun, 08 May 2011 23:00:00 +0100 4948400 http://www.medworm.com/index.php?rid=5461146&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000993%2Fabstract%3Frss%3Dyes Abstract: Pulsed arterial spin labeling (PASL) is an increasingly common technique for noninvasively measuring cerebral blood flow (CBF) and has previously been shown to have good repeatability. It is likely to find a place in clinical trials and in particular the investigation of pharmaceutical agents active in the central nervous system. We aimed to estimate the sample sizes necessary to detect regional changes in CBF in common types of clinical trial design including (a) between groups, (b) a two-period crossover and (3) within-session single dosing. Whole brain CBF data were acquired at 3 T in two independent groups of healthy volunteers at rest; one of the groups underwent a repeat scan. Using these data, we were able to estimate between-groups, between-session and within-session vari... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461146 Fri, 06 May 2011 04:00:00 +0100 5461146 http://www.medworm.com/index.php?rid=4948412&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000981%2Fabstract%3Frss%3Dyes In conclusion, STIR with single-axis DWI is superior to SFS with trace DWI in the suppression of bowel signal and peripheral nerves. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948412 Thu, 05 May 2011 23:00:00 +0100 4948412 http://www.medworm.com/index.php?rid=4948407&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000889%2Fabstract%3Frss%3Dyes Abstract: Peripheral MR angiography requires high resolution and arterial contrast. Neither can be obtained simultaneously due to the short arterial phase of the contrast agent. To improve temporal resolution, keyhole imaging was developed, which combines high resolution and arterial k-spaces at the time of image acquisition. Here, a related approach is introduced for image post-processing in the Fourier domain. It is demonstrated that simple substitution of the central k-space with low-resolution data leads to severe distortion. Hence, a dedicated calculation scheme is necessary for composite k-space post-processing. A solution is presented for high-resolution arterial peripheral MR angiography that uses subtraction of venous intensities from the central high-resolution k-space. The calcu... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948407 Thu, 05 May 2011 23:00:00 +0100 4948407 http://www.medworm.com/index.php?rid=4857685&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000877%2Fabstract%3Frss%3Dyes Abstract: Consistent scan prescription for MRI of the knee is very important for accurate comparison of images in a longitudinal study. However, consistent scan region selection is difficult due to the complexity of the knee joint. We propose a novel method for registering knee images using a mutual information registration algorithm to align images in a baseline and follow-up exam. The output of the registration algorithm, three translations and three Euler angles, is then used to redefine the region to be imaged and acquire an identical oblique imaging volume in the follow-up exam as in the baseline. This algorithm is robust to articulation of the knee and anatomical abnormalities due to disease (e.g., osteophytes). The registration method is performed only on the distal femur and is not... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857685 Thu, 05 May 2011 23:00:00 +0100 4857685 http://www.medworm.com/index.php?rid=4857684&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000865%2Fabstract%3Frss%3Dyes Abstract: A multistep procedure was developed to register magnetic resonance imaging (MRI) and histological data from the same sample in the light microscopy image space, with the ultimate goal of allowing quantitative comparisons of the two datasets. The fixed brain of an owl monkey was used to develop and test the procedure. In addition to the MRI and histological data, photographic images of the brain tissue block acquired during sectioning were assembled into a blockface volume to provide an intermediate step for the overall registration process. The MR volume was first registered to the blockface volume using a combination of linear and nonlinear registration, and two dimensional (2D) blockface sections were registered to corresponding myelin-stained sections using a combination of li... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857684 Thu, 05 May 2011 23:00:00 +0100 4857684 http://www.medworm.com/index.php?rid=4857681&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000737%2Fabstract%3Frss%3Dyes Abstract: Introduction: A substantial, common shortcoming of the currently used semiautomated techniques for the quantification of myocardial infarct with delayed enhancement magnetic resonance imaging is the assumption that the whole myocardial slab that corresponds to the hyperenhanced tomographic area is 100% nonviable. This assumption is, however, incorrect. To resolve this conflict, we have recently proposed the signal intensity percent-infarct mapping method and validated it in an ex vivo, canine experiment. The purpose of the current study has been the validation of the signal intensity percent-infarct mapping method in vivo, using a porcine model of reperfused myocardial infarct.Methods: In swines (n=6), reperfused myocardial infarct was generated occluding for 90 min by an angiopl... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857681 Thu, 05 May 2011 23:00:00 +0100 4857681 http://www.medworm.com/index.php?rid=4857680&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000816%2Fabstract%3Frss%3Dyes Abstract: Dynamic contrast-enhanced magnetic resonance imaging commonly uses compartment models to estimate tissue parameters in general and perfusion parameters in particular. Compartment models assume a homogeneous distribution of the injected tracer throughout the compartment volume. Since tracer distribution within a compartment cannot be assessed, the parameters obtained by means of a compartment model might differ from the actual physical values.This work systematically examines the widely used permeability-surface-limited one-compartment model to determine the reliability of the parameters obtained by comparing them with their actual values. A computer simulation was used to model spatial tracer distribution within the interstitial volume using diffusion of contrast agent in tissue.... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857680 Thu, 05 May 2011 23:00:00 +0100 4857680 http://www.medworm.com/index.php?rid=4857678&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000890%2Fabstract%3Frss%3Dyes Abstract: Magnetic resonance (MR) perfusion imaging is a clinical technique for measuring brain blood flow parameters during stroke and other ischemic events. Ischemia in brain tissue can be difficult to accurately measure or visualize when using MR-derived cerebral blood flow (CBF) maps. The deconvolution techniques used to estimate flow can introduce a mean transit time-dependent bias following application of noise stabilization techniques. The underestimation of the CBF values, greatest in normal tissues, causes a decrease in the image contrast observed in CBF maps between normally perfused and ischemic tissues; resulting in ischemic areas becoming less conspicuous. Through application of the proposed simple extrapolation technique, CBF biases are reduced when missing high-frequency sig... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857678 Thu, 05 May 2011 23:00:00 +0100 4857678 http://www.medworm.com/index.php?rid=5461140&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000968%2Fabstract%3Frss%3Dyes Abstract: Functional magnetic resonance imaging (fMRI) research has revealed not only important aspects of the neural basis of cognitive and perceptual functions, but also important information on the relation between high-level brain functions and physiology. One of the central outstanding questions, given the features of the blood oxygenation level-dependent (BOLD) signal, is whether and how autonomic nervous system (ANS) functions are related to changes in brain states as measured in the human brain. A straightforward way to address this question has been to acquire external measurements of ANS activity such as cardiac and respiratory data, and examine their relation to the BOLD signal. In this article, we describe two conceptual approaches to the treatment of ANS measures in the contex... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5461140 Wed, 04 May 2011 04:00:00 +0100 5461140 http://www.medworm.com/index.php?rid=5150143&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000907%2Fabstract%3Frss%3Dyes Abstract: Acupoint specificity, as a crucial issue in acupuncture neuroimaging studies, is still a controversial topic. Previous studies have generally adopted a block-based general linear model (GLM) approach, which predicts the temporal changes in the blood oxygenation level-dependent signal conforming to the “on–off” specifications. However, this method might become impractical since the precise timing and duration of acupuncture actions cannot be specified a priori. In the current study, we applied a data-driven multivariate classification approach, namely, support vector machine (SVM), to explore the neural specificity of acupuncture at gall bladder 40 (GB40) using kidney 3 (KI3) as a control condition (belonging to different meridians but the same nerve segment). In addition, t... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=5150143 Sun, 01 May 2011 23:00:00 +0100 5150143 http://www.medworm.com/index.php?rid=4948414&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000841%2Fabstract%3Frss%3Dyes The aim of the study by Novak et al. was to investigate the hypothesis that white matter hyperintensities (WMH) may affect feedback mechanisms controlling the dynamics of postural control. To this end, a fractional Brownian motion (FBM) model for the center of pressure (COP) motion was used. In particular, the conclusion was drawn that “WMHs affect long-term dynamics of postural control, which requires engagement of feedback mechanisms.” As will be shown below, this conclusion is invalid because Novak et al. misinterpreted the FBM model. An alternative interpretation of the results obtained in Ref. is offered consistent with the FMB model. Accordingly, the results obtained in Ref. suggest that WMHs are correlated to changes in the distributions of neurophysiological delays relevant for... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948414 Sun, 01 May 2011 23:00:00 +0100 4948414 http://www.medworm.com/index.php?rid=4948411&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000944%2Fabstract%3Frss%3Dyes Abstract: This work presents a simple design for a mobile single-sided nuclear magnetic resonance (NMR) apparatus with a relatively homogeneous static magnetic field (B0) distribution. In the proposed design, the B0 magnetic field of the apparatus is synthesized using only two permanent magnet blocks, i.e., a cube (main) magnet and a small shim magnet placed above the main magnet. The magnetic flux of the shim magnet partially cancels out that of the main magnet, subsequently creating a smooth B0 profile above the shim magnet where low-resolution NMR experiments are performed. Compared with many previously published designs, this straightforward design simplifies the construction of the apparatus and simultaneously generates a B0 field parallel to the apparatus surface, allowing the use of... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948411 Sun, 01 May 2011 23:00:00 +0100 4948411 http://www.medworm.com/index.php?rid=4857690&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000701%2Fabstract%3Frss%3Dyes Abstract: Spatial smoothing is typically used to denoise magnetic resonance imaging (MRI) data. Gaussian smoothing kernels, associated with heat equations or isotropic diffusion (ISD), are widely adopted for this purpose because of their easy implementation and efficient computation, but despite these advantages, Gaussian smoothing kernels blur the edges, curvature and texture of images. To overcome these issues, researchers have proposed anisotropic diffusion (ASD) and non-local means [i.e., diffusion (NLD)] kernels. However, these new filtering paradigms are rarely applied to MRI analyses. In the current study, using real degraded MRI data, we demonstrated the effect of denoising using ISD, ASD and NLD kernels. Furthermore, we evaluated their impact on three common preprocessing steps of... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857690 Sun, 01 May 2011 23:00:00 +0100 4857690 http://www.medworm.com/index.php?rid=4857687&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000956%2Fabstract%3Frss%3Dyes In conclusion, the GPU computation method is a practical way to accelerate automatic image registration. This technology promises a broader scope of application in the field of image registration. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857687 Sun, 01 May 2011 23:00:00 +0100 4857687 http://www.medworm.com/index.php?rid=4857686&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000762%2Fabstract%3Frss%3Dyes Abstract: Dysfunction of the corticolimbic circuitry has been highlighted in social anxiety disorder (SAD) during social stimuli. However, few studies have investigated functional connectivity in SAD during the resting state, which may improve our understanding of SAD pathophysiology. The aim of this study was to investigate whether whole-brain functional connectivity might be aberrant in SAD patients, and if so, whether these changes are related to the measured clinical severity. Seventeen SAD patients and 19 healthy controls participated in resting-state functional magnetic resonance imaging. The brain was first divided into 90 paired brain regions and functional connectivity was then estimated by temporal correlation between each of these regions. Furthermore, connections that were sign... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857686 Sun, 01 May 2011 23:00:00 +0100 4857686 http://www.medworm.com/index.php?rid=4857683&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000750%2Fabstract%3Frss%3Dyes Abstract: Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is increasingly in use as an investigational biomarker of response in cancer clinical studies. Proper registration of images acquired at different time points is essential for deriving diagnostic information from quantitative pharmacokinetic analysis of these data. Motion artifacts in the presence of time-varying intensity due to contrast enhancement make this registration problem challenging. DCE-MRI of chest and abdominal lesions is typically performed during sequential breath-holds, which introduces misregistration due to inconsistent diaphragm positions and also places constraints on temporal resolution vis-à-vis free-breathing. In this work, we have employed a computer-generated DCE-MRI phantom to compare the pe... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857683 Sun, 01 May 2011 23:00:00 +0100 4857683 http://www.medworm.com/index.php?rid=4857682&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000786%2Fabstract%3Frss%3Dyes Abstract: Echo-planar diffusion-weighted images can display significant geometric distortions due to eddy current fields. Several preparation schemes have been proposed, which can null eddy currents with a single time constant. The aim of this work was to compare the performance of three such pulse sequences in the presence of multiple components and investigate whether affine registration is capable of correcting for the resulting distortions. A magnetic resonance imaging simulator was used to eliminate potential confounding factors. The doubly refocused sequences showed substantially reduced effects. Applying affine registration to the single spin-echo images leads to reduced residuals, but not to the level observed for the doubly refocused sequences. Modified versions of the standard si... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857682 Sun, 01 May 2011 23:00:00 +0100 4857682 http://www.medworm.com/index.php?rid=4857679&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000671%2Fabstract%3Frss%3Dyes Abstract: MRI techniques have been developed that can noninvasively probe the apparent diffusion coefficient (ADC) of water via diffusion-weighted MRI (DW-MRI). These methods have found much application in cancer where it is often found that the ADC within tumors is inversely correlated with tumor cell density, so that an increase in ADC in response to therapy can be interpreted as an imaging biomarker of positive treatment response. Dynamic contrast enhanced MRI (DCE-MRI) methods have also been developed and can noninvasively report on the extravascular extracellular volume fraction of tissues (denoted by ve). By conventional reasoning, the ADC should therefore also be directly proportional to ve. Here we report measurements of both ADC and ve obtained from breast cancer patients at both ... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857679 Sun, 01 May 2011 23:00:00 +0100 4857679 http://www.medworm.com/index.php?rid=4857676&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000634%2Fabstract%3Frss%3Dyes Abstract: Inhomogeneity in static field B0 and/or RF field B1 is inevitable under some circumstances. In this work, a method based on intermolecular double-quantum coherences is employed for high-resolution 1D MR spectroscopy via 2D acquisition under such a condition. High-resolution information on chemical shifts, multiplet patterns, J coupling constants and relative peak areas can be retained in the resulting 1D projected spectra, as shown with results from a narrow-bore NMR spectrometer and a whole-body clinical scanner. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857676 Sun, 01 May 2011 23:00:00 +0100 4857676 http://www.medworm.com/index.php?rid=4948413&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000622%2Fabstract%3Frss%3Dyes Abstract: Congenital absence of the portal vein (CAPV) is a rare anomaly in which the intestinal and splenic venous drainage bypass the liver and drain directly into the systemic veins through various porto-systemic shunts. In this article, we illustrate a case of multiple focal nodular hyperplasia (FNH) with congenital absence of the portal vein in a male, which, to our knowledge, is the third reported case in the literature since its first description in 1793. Furthermore, we discuss the embryology of the portal vein and the Morgan and Superina classification of portosystemic anomalies, the association between portal vein agenesis and multiple FNHs, and, lastly, the use of a hepatocellular-specific MRI contrast agent as an important diagnostic tool in the confirmation of FNH. (Source: Ma... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948413 Tue, 26 Apr 2011 23:00:00 +0100 4948413 http://www.medworm.com/index.php?rid=4948410&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000749%2Fabstract%3Frss%3Dyes Abstract: A free-breathing 3D cine steady-state free precession (SSFP) technique was developed using the z intensity-weighted position (ZIP) which is the center of mass of a projection along the slice direction as a respiratory gating signal. The ZIP signal was continuously acquired using a slice encoded k-space center sampling in every TR. The performance of this gating method was compared with a method using the k-space center signal (KC) and with conventional 2D breath-hold cine SSFP in healthy subjects by measuring image quality and left ventricular function. The preliminary data obtained here demonstrated that the ZIP gating method provided superior respiratory motion artifact suppression when compared to the KC gating and provided left ventricular ejection fractions, and end-diastoli... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4948410 Tue, 26 Apr 2011 23:00:00 +0100 4948410 http://www.medworm.com/index.php?rid=4857689&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000683%2Fabstract%3Frss%3Dyes In conclusion, we derived a generalized equation for describing the magnetization in SPGR imaging. This equation will provide a suitable basis for understanding the signal intensity in SPGR imaging and/or T1 measurement using an SPGR sequence in cases in which the effect of in-pulse relaxation and/or MT cannot be neglected. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857689 Tue, 26 Apr 2011 23:00:00 +0100 4857689 http://www.medworm.com/index.php?rid=4857688&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X1100066X%2Fabstract%3Frss%3Dyes This study introduces a quantitative comparison between two known methods for B1+/actual FA and reception sensitivity mapping: the double-angle method (DAM) and the fitting (FIT) method. Experimental data obtained using DAM and FIT methods are also compared with numerical simulation results. (Source: Magnetic Resonance Imaging) Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857688 Tue, 26 Apr 2011 23:00:00 +0100 4857688 http://www.medworm.com/index.php?rid=4857677&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000646%2Fabstract%3Frss%3Dyes We report on a phase-cycling method which can eliminate B1 RF inhomogeneity effects in T1ρ imaging. This method does not only correct for image artifacts but also for T2ρ contamination caused by B1 RF inhomogeneity. The presence of B0 magnetic field inhomogeneity can compromise the effectiveness of this method for B1 RF inhomogeneity correction. We demonstrate that, by combining the spin-locking scheme reported by Dixon et al. (Myocardial suppression in vivo by spin locking with composite pulses. Magn Reson Med 1996; 36:90–94) with phase cycling, we can simultaneously correct B0 magnetic field inhomogeneity effects and B1 RF inhomogeneity effects in T1ρ imaging. Phantom and in vivo data sets are used to demonstrate the proposed methods and to compare them with other existing T1ρ prep... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857677 Tue, 26 Apr 2011 23:00:00 +0100 4857677 http://www.medworm.com/index.php?rid=4857675&cid=s_36808_37_f&fid=36808&url=http%3A%2F%2Fwww.mrijournal.com%2Farticle%2FPIIS0730725X11000658%2Fabstract%3Frss%3Dyes Abstract: Magnetic resonance imaging (MRI) has played an important role in the diagnosis and management of cancer since it was first developed, but other modalities also continue to advance and provide complementary information on the status of tumors. In the future, there will be a major continuing role for noninvasive imaging in order to obtain information on the location and extent of cancer, as well as assessments of tissue characteristics that can monitor and predict treatment response and guide patient management. Developments are currently being undertaken that aim to provide improved imaging methods for the detection and evaluation of tumors, for identifying important characteristics of tumors such as the expression levels of cell surface receptors that may dictate what types of th... Magnetic Resonance Imaging journals http://www.medworm.com/rss/comments.php?id=4857675 Tue, 26 Apr 2011 23:00:00 +0100 4857675