Radiological Physics and Technology
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62 records returned
Development of pulmonary blood flow evaluation method with a dynamic flat-panel detector: quantitative correlation analysis with findings on perfusion scan
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Abstract Pulmonary blood flow is reflected in dynamic chest radiographs as changes in X-ray translucency, i.e., pixel values. Thus,
decreased blood flow should be observed as a reduction of the variation of X-ray translucency. We performed the present study
to investigate the feasibility of pulmonary blood flow evaluation with a dynamic flat-panel detector (FPD). Sequential chest
radiographs of 14 subjects were obtained with a dynamic FPD system. The changes in pixel value in each local area were measured
and mapped on the original image by use of a gray scale in which small and large changes were shown in w...
Source: Radiological Physics and Technology - November 6, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Measurement of absorbed doses in organs of medical staff at 18F-FDG pet examinationEmail this article to a colleague.
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In this study, the organ doses were measured using a human- body phantom simulating a medical staff member, and we considered
an effective method for decreasing exposure to staff in positron emission tomography examinations. A fluorescence glass dosimeter
was arranged for measurements in various organs. Regarding exposure, the average ratio of the dose at 100 cm from the source
to the dose at 30 cm was 0.35. The ratio of the dose at 100 cm with a 3 cm lead shield to the dose at 100 cm with no shielding
device was 0.01. To reduce the radiation exposure effectively, medical staff members should i...
Source: Radiological Physics and Technology - November 3, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Practical approaches to four-dimensional heavy-charged-particle lung therapyEmail this article to a colleague.
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Abstract We have developed new design algorithms for compensating boli to facilitate the implementation of four-dimensional charged-particle
lung therapy in clinical applications. Four-dimensional CT (4DCT) data for eight lung cancer patients were acquired with a
16-slice CT under free breathing. Six compensating boli were developed that may be categorized into three classes: (1) boli-based
on contoured gross tumor volumes (GTV) from a 4DCT data set during each respiratory phase, subsequently combined into one
(GTV-4DCT bolus); (2) boli-based on contoured internal target volume (ITV) from image-processed 3DC...
Source: Radiological Physics and Technology - October 13, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
A parameter study of pencil beam proton dose distributions for the treatment of ocular melanoma utilizing spot scanningEmail this article to a colleague.
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Abstract The results of Monte Carlo calculated dose distributions of proton treatment of ocular melanoma are presented. An efficient
spot scanning method utilizing active energy modulation, which also minimizes the number of target spots was developed. We
simulated various parameter values for the particle energy spread and the pencil beam diameter in order to determine values
suitable for medical treatment. We found that a 2.5-mm-diameter proton beam with a 5% Gaussian energy spread was suitable
for treatment of ocular melanoma while preserving vision for the typical case that we simulated. The energy spect...
Source: Radiological Physics and Technology - September 18, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Detectability of a lung nodule displayed on a liquid-crystal display monitor with different maximum luminance settingsEmail this article to a colleague.
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Abstract Our purpose in this study was to examine the detectability of a lung nodule at different maximum luminance settings of a liquid-crystal
display (LCD) monitor by utilizing receiver operating characteristic (ROC) analysis. The LCD monitor used in this study was
calibrated to the grayscale standard display function with different maximum luminance settings (670, 450, and 170 cd/m2). The average area under the ROC curve (AUC) and the standard deviation for all observers at 670, 450, and 170 cd/m2 were 0.837 ± 0.076, 0.832 ± 0.051, and 0.830 ± 0.078, respectively....
Source: Radiological Physics and Technology - September 3, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Creation and application of three-dimensional computer-graphic animations for introduction to radiological physics and technologyEmail this article to a colleague.
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Abstract Physics-related subjects are important in the educational fields of radiological physics and technology. However, conventional
teaching tools, for example texts, equations, and two-dimensional figures, are not very effective in attracting the interest
of students. Therefore, we have created several multimedia educational materials covering radiological physics and technology.
Each educational presentation includes several segments of high-quality computer-graphic animations designed to attract students’
interest. We used personal computers (PCs) and commercial software to create and compile these....
Source: Radiological Physics and Technology - July 27, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
AcknowledgmentEmail this article to a colleague.
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Content Type Journal ArticleDOI 10.1007/s12194-009-0064-3
Journal Radiological Physics and TechnologyOnline ISSN 1865-0341Print ISSN 1865-0333 (Source: Radiological Physics and Technology)
Source: Radiological Physics and Technology - July 15, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
An EGSnrc investigation of the air-kerma strength, dose rate constant, and radial dose function of 125I brachytherapy sourcesEmail this article to a colleague.
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Abstract Titanium-encapsulated 125I brachytherapy sources are in use for treatment of the eye, brain, and head and neck region, and for early stage prostate
cancer. The photoelectric interaction of 125I photons with titanium encapsulation generates Ti K X-rays (~5 keV). According to the National Institute of Standards and
Technology (NIST) 1999 air-kerma strength, S
k, standard, these X-rays should be excluded from S
k. We used the EGSnrc Monte Carlo code system to calculate the S
k (including the contribution of ~5-keV X-rays), dose rate constant, and radial dose function for five different 125I source mod...
Source: Radiological Physics and Technology - July 11, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Monte Carlo simulations of electron beams collimated with a dual electron multileaf collimator: a feasibility studyEmail this article to a colleague.
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Abstract Electron applicators and cut-outs have been used for some time in the delivery of electron beam therapy. A dual electron multileaf
collimator (eMLC) consisting of upper and lower eMLCs was designed, and dose distributions of electron beams delivered by
it were evaluated by Monte Carlo simulations by use of the EGSnrc Monte Carlo code. The percentage depth dose (PDD), dose
profiles, dose gradient falloff (G), depth of maximum dose (R
100), surface dose, bremsstrahlung background, beam flatness, and penumbra of the dual eMLC were evaluated and compared with
those simulated and measured with the stand...
Source: Radiological Physics and Technology - July 6, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Study of intra-abdominal fat distribution in sigmoid colon cancer in Japanese patients by use of MDCT dataEmail this article to a colleague.
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Abstract To assess the relationship between intra-abdominal fat and sigmoid colon cancer, we investigated the intra-abdominal fat distribution
in 172 examples of sigmoid colon cancer and 767 examples of various other pathologies by using data from multidetector-row
computed tomography. One significant finding was that the intra-abdominal fat area in sigmoid colon cancer presents a small
secondary peak in the pelvis on the profile of the intra-abdominal fat, which we called the pelvic sub-peak. The presence
or absence of the pelvic sub-peak was determined based on the sub-peak ratio, which was calculated by d...
Source: Radiological Physics and Technology - July 1, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Feasibility study of near-infrared fluorescence tomography using a positron emission tomograph equipped with depth-of-interaction PET detectorsEmail this article to a colleague.
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In this study, we demonstrate the feasibility of 3D NIR fluorescence tomography imaging
by employing DOI-PET detectors in computer simulations. In the simulations, we used a 40 mm × 40 mm × 40 mm cubic phantom,
a square detector geometry, and an optical diffusion equation to approximate the light propagation. We then evaluated imaging
systems for 3D fluorescence tomography with different detector resolutions and excitation light arrangements using singular-value
analysis and imaging simulation. We confirmed that the reconstructed images from low-resolution detectors (8 × ...
Source: Radiological Physics and Technology - June 30, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Investigation on the optimal position for the quantification of hepatic perfusion by use of dynamic contrast-enhanced computed tomography in ratsEmail this article to a colleague.
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Abstract Our purpose in this study was to investigate the optimal position for the quantification of hepatic perfusion by using a dual-input,
single-compartment model and dynamic contrast-enhanced computed tomography (DCE-CT) in rats. The DCE-CT studies were performed
with the animals in the supine and prone position, with an interval of 1 day, on six male Sprague–Dawley rats. The distance
between the inferior vena cava (IVC) and portal vein was calculated. The arterial hepatic blood flow (AHBF) and portal hepatic
blood flow (PHBF) were also estimated by use of time–density curves (TDCs) in the aort...
Source: Radiological Physics and Technology - June 5, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Measurement of thermal neutron fluence distribution with use of 23Na radioactivation around a medical compact cyclotronEmail this article to a colleague.
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Abstract A medical compact cyclotron produces about 1015 neutrons per day along with 100 GBq of 18F. Therefore, it is important to establish radiation safety guidelines on residual radioactivity for routine operation, maintenance
work, and decommissioning. Thus, we developed a simple method for measuring the thermal neutrons in a cyclotron room. In order
to verify the feasibility of our proposed method, we measured the thermal neutron distribution around a cyclotron by using
the activation of 23Na in salt. We installed 78 salt dosimeters in the cyclotron room with a 50 cm mesh. The photopeak of 24Na...
Source: Radiological Physics and Technology - May 16, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Application of an artificial neural network to the computer-aided differentiation of focal liver disease in MR imagingEmail this article to a colleague.
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Abstract The differentiation of focal liver lesions in magnetic resonance (MR) imaging is primarily based on the intensity and homogeneity
of lesions with different imaging sequences. However, these imaging findings are falsely interpreted in some patients because
of the complexities involved. Our aim is to establish a computer-aided diagnosis system named LiverANN for classifying the
pathologies of focal liver lesions into five categories using the artificial neural network (ANN) technique. On each MR image,
a region of interest (ROI) in the focal liver lesion was delineated by a radiologist. The intensity ...
Source: Radiological Physics and Technology - May 14, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Comparison of viewing angle and observer performances in different types of liquid-crystal display monitorsEmail this article to a colleague.
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Abstract It is known that the performance of liquid-crystal display (LCD) monitors, such as the luminance and contrast ratio, is dependent
on the viewing angle. Our purpose in this study was to compare the angular performance and the effect on observer performance
of different types of LCD monitors. The luminance performance and contrast ratio as a function of viewing angle (−60° to 60°)
in each direction for two types of LCD monitors, namely, a general-purpose LCD monitor and one especially designed for medical
use, were measured in this study. Furthermore, the observer performance at various viewing an...
Source: Radiological Physics and Technology - May 14, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Effect of daily setup errors on individual dose distribution in conventional radiotherapy: an initial studyEmail this article to a colleague.
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Abstract Recent linear accelerators can perform cone-beam computed tomography to correct setup errors immediately before dose delivery.
We calculated the dose distribution with setup errors acquired from cone-beam computed tomography to determine a more realistic
and individual effect of setup errors. The differences in dose distribution were analyzed. The setup errors of three patients
who were irradiated in the neck, esophagus, and pelvic area were obtained retrospectively. We found that the maximum dose
variances for the three cases were 19.9–35.9%. The maximum dose variance points were relatively far f...
Source: Radiological Physics and Technology - May 1, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Bulk motion-independent analyses of water diffusion changes in the brain during the cardiac cycleEmail this article to a colleague.
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Abstract We evaluated dynamic changes in water diffusion in the brain during the cardiac cycle by using cine diffusion MRI. On a 1.5-T
MRI, ECG-triggered single-shot diffusion echo planar imaging was used with sensitivity encoding, halfscan, and rectangular
field of view techniques for minimizing bulk motion effects such as brain pulsation, with a data-sampling window of 3 ms.
The apparent diffusion coefficient (ADC) and fractional anisotropy (FA) in the white matter zone were determined in ten healthy
volunteers and then compared with the intracranial volume change (ICVC) revealed by phase-contrast cin...
Source: Radiological Physics and Technology - April 23, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
A statistical clustering approach to visualizing the relationship between early and delayed images in whole-body FDG-PETEmail this article to a colleague.
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Abstract We propose a new method for diagnostic assistance in oncology, [fluorine-18]-2-fluoro-2-deoxy-d-glucose (FDG)-positron emission tomography (PET). Early and delayed scans were performed on 10 patients with lung cancer
by use of an ECAT EXACT 47 PET scanner, and standardized-uptake-value (SUV) images were created. Three segmentation (S1, S2,
and S3) maps were created from the early and delayed SUV images according to various thresholds (SUVthreshold = 2.0, 2.5, and 3.0) based on the early image and the percentage change defined as (SUVdelayed − SUVearly) × 100/SUVearly. ...
Source: Radiological Physics and Technology - April 21, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
EditorialEmail this article to a colleague.
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Content Type Journal ArticleDOI 10.1007/s12194-009-0055-4Authors
Kunio Doi, The University of Chicago Department of Radiology Chicago IL USA
Journal Radiological Physics and TechnologyOnline ISSN 1865-0341Print ISSN 1865-0333 (Source: Radiological Physics and Technology)
Source: Radiological Physics and Technology - April 14, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Investigation of scatter fractions for estimating leakage dose in medical X-ray imaging facilitiesEmail this article to a colleague.
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Abstract It is essential to make accurate estimates of the scatter of radiation from the human body when calculating the leakage dose
in medical X-ray imaging facilities. The scatter fraction varies with the size and shape of the radiation field in a way that
is not exactly proportional to the area of the field. Japanese law quotes values for the scatter fraction that are provided
by the National Council on Radiation Protection and Measurements, but these data were obtained 30 years ago, using equipment
that differed considerably from that employed nowadays. To date, no attempt has been made to confirm ...
Source: Radiological Physics and Technology - April 8, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Nationwide survey on the operational status of medical compact cyclotrons in JapanEmail this article to a colleague.
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Abstract The management of induced radioactivity of the cyclotron itself and structures is an important issue in decommissioning of
medical compact cyclotrons. To obtain basic data on the actual operational conditions of cyclotrons, we performed nationwide
survey. The actual beam current was about half of the maximum beam current indicated in the official permits for cyclotron
operation. The actual operating time was about 10% of the maximum operating time indicated in the official permits. The average
daily radioactive-nuclide (18F) production was only 10% of the allowed maximum quantity. From these results...
Source: Radiological Physics and Technology - March 27, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Evaluation of errors influencing accuracy in image-guided neurosurgeryEmail this article to a colleague.
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Abstract Neurosurgeons sometimes find it difficult to locate tumors precisely during microsurgery, particularly tumors located in the
brain parenchyma because of the absence of boundaries in this region. Image-guided neurosurgical techniques conducted with
the help of neuronavigation systems have been developed and have gained importance recently. Accuracy is vital during image-guided
neurosurgery. We used a phantom to evaluate the errors introduced during navigation. The three errors evaluated were skin-shift,
marker-gap, and table-rotation errors. The skin-shift error occurs if the fiducial markers positio...
Source: Radiological Physics and Technology - March 17, 2009 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Dosimetric verification in inhomogeneous phantom geometries for the XiO radiotherapy treatment planning system with 6-MV photon beamsEmail this article to a colleague.
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Abstract We have developed a practical dose verification method for radiotherapy treatment planning systems by using only a Farmer
ionization chamber in inhomogeneous phantoms. In particular, we compared experimental dose verifications of multi-layer phantom
geometries and laterally inhomogeneous phantom geometries for homogeneous and inhomogenous dose calculations by using the
fast-Fourier-transform convolution, fast-superposition, and superposition in the XiO radiotherapy treatment-planning system.
We applied the dose verification method to three kernel-based algorithms in various phantom geometries with w...
Source: Radiological Physics and Technology - December 30, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Water-equivalent pathlength reproducibility due to respiratory pattern variation in charged-particle pancreatic radiotherapyEmail this article to a colleague.
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Abstract We evaluated the water-equivalent length (WEL) reproducibility due to variation in the external respiratory marker position
when using a 4DCT scan in respiratory-gated charged-particle treatment. Two sets of pancreatic 4DCT data from two patients
were acquired under free breathing conditions with 256-slice CT. The 4DCT data included two exhalation phases and the respiratory
patterns in each patient differed, one being regular and the other irregular. The WEL calculation region is defined in the
first respiratory cycle by two planes, one at the patient entrance surface and the other behind the target...
Source: Radiological Physics and Technology - December 25, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Polarity effect in commercial ionization chambers used in photon beams with small fieldsEmail this article to a colleague.
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This study concentrated on measuring the dependence of the polarity effect at various energies, and for various field size,
ionization chamber, and electrometer combinations. Of the seven chambers, CC01, PTW23323, and PTW31006 had the largest polarity
effect for small field sizes. The materials of the central electrode of these three chambers were steel or air-equivalent
plastic C-552. The magnitude of the polarity effect was shown to be strongly dependent on the material of the collecting electrode.
This polarity effect dependence was observed for the ionization chambers and small field sizes studied.
Content Type ...
Source: Radiological Physics and Technology - December 18, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Embossed radiography utilizing energy subtractionEmail this article to a colleague.
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Abstract Currently, it is difficult to carry out refraction-contrast radiography by using a conventional X-ray generator. Thus, we
developed an embossed radiography system utilizing dual-energy subtraction for decreasing the absorption contrast in unnecessary
regions, and the contrast resolution of a target region was increased by use of image-shifting subtraction and a linear-contrast
system in a flat panel detector (FPD). The X-ray generator had a 100-μm-focus tube. Energy subtraction was performed at tube
voltages of 45 and 65 kV, a tube current of 0.50 mA, and an X-ray exposure time of 5.0&nbs...
Source: Radiological Physics and Technology - December 18, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Need for liquid–crystal display monitors having the capability of rendering higher than 8 bits in display-bit depthEmail this article to a colleague.
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Abstract Our purpose in this study was to examine the potential usefulness of liquid–crystal display (LCD) monitors having the capability
of rendering higher than 8 bits in display-bit depth. An LCD monitor having the capability of rendering 8, 10, and 12 bits
was used. It was calibrated to the grayscale standard display function with a maximum luminance of 450 cd/m2 and a minimum of 0.75 cd/m2. For examining the grayscale resolution reported by ten observers, various simple test patterns having two different combinations
of luminance in 8, 10, and 12 bits were randomly displayed on the LCD monito...
Source: Radiological Physics and Technology - December 16, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
A review of image-guided radiotherapyEmail this article to a colleague.
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We present a review of the rationale, technology, and methodology of image guidance, as well as an
overview of current work in IGRT at the Massachusetts General Hospital. The technology is rapidly evolving, and synergisms
between the various acquisition approaches are converging to provide unparalleled information on target and normal tissue
location and motion. With these new approaches to patient localization, we expect improved clinical results to be forthcoming.
Content Type Journal ArticleDOI 10.1007/s12194-008-0045-yAuthors
George T. Y. Chen, Massachusetts General Hospital Department of Radiation Oncology 100...
Source: Radiological Physics and Technology - December 15, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
New protocol of myocardial SPECT imaging with technetium-99m sestamibi for reducing the time interval between rest and adenosine stress phasesEmail this article to a colleague.
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Abstract We have developed a new protocol of myocardial perfusion-gated single-photon emission computed tomography (SPECT), by use
of technetium-99m sestamibi (MIBI), in which SPECT imaging at rest followed by SPECT imaging after adenosine with low level
ergometer stress can be conducted by use of the Monzen position within a shortened total testing time of 1 h or less. The
study group consisted of 137 patients who underwent this new imaging protocol. The diagnostic quality of the images was as
good as that of images obtained with the conventional method (30–60 min after the injection of MIBI). T...
Source: Radiological Physics and Technology - December 11, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Imaging simulations of an “OpenPET” geometry with shifting detector ringsEmail this article to a colleague.
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Abstract We have proposed a new “OpenPET” geometry consisting of two detector rings of axial length W each separated by a gap G. For obtaining an axially continuous field of view (FOV) of 2W + G, the maximum limit for G must be W. However, two valleys of sensitivity appear on both sides of the gap. Setting a more limited range for the gap as G < W, which is desirable for filling in the sensitivity valleys, results in not only a shortened gap, but also a shortened axial
FOV. In this paper, we propose an alternative method for improving the uniformity of sensitivity by shifting two dete...
Source: Radiological Physics and Technology - December 10, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Numerical evaluation of the effectiveness of colloidal gold as a contrast agentEmail this article to a colleague.
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Abstract Monte Carlo numerical simulations were conducted to evaluate the effectiveness of colloidal gold as a contrast agent. The
simulations were conducted using a simple configuration, modeling a phantom to maintain the generality of the results, and
the effects of the mass percentage of gold accumulated inside the tumor and the energy of the irradiating X-rays were evaluated,
as well as other information, such as the energy spectrum of the photons reaching the detector and the change in the energy
deposited inside the phantom. The contrast of the X-ray image due to the layer is calculated from the total ...
Source: Radiological Physics and Technology - November 18, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Evaluating the performance of a MOSFET dosimeter at diagnostic X-ray energies for interventional radiologyEmail this article to a colleague.
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Abstract For reducing the risk of skin injury during interventional radiology (IR) procedures, it has been suggested that physicians
track patients’ exposure doses. The metal-oxide semiconductor field effect transistor (MOSFET) dosimeter is designed to measure
patient exposure dose during radiotherapy applications at megavoltage photon energies. Our purpose in this study was to evaluate
the feasibility of using a MOSFET dosimeter (OneDose system) to measure patients’ skin dose during exposure to diagnostic
X-ray energies used in IR. The response of the OneDose system was almost constant at diagnostic X-r...
Source: Radiological Physics and Technology - November 14, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Differentiation of hepatic tumors by use of image contrast with T2-weighted MRIEmail this article to a colleague.
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In conclusion,
the quantitative analysis of hepatic tumors was able to differentiate among these lesions by use of the T2-shine ratio.
Content Type Journal ArticleDOI 10.1007/s12194-008-0043-0Authors
Akio Ogura, Kyoto City Hospital Department of Radiology 1-2, Higashitakada-cho, Mibu, Nakagyo-ku Kyoto JapanKatsumi Hayakawa, Kyoto City Hospital Department of Radiology 1-2, Higashitakada-cho, Mibu, Nakagyo-ku Kyoto JapanTosiaki Miyati, Kanazawa University Graduate School of Medical Science Kanazawa JapanFumie Maeda, Kyoto City Hospital Department of Radiology 1-2, Higashitakada-cho, Mibu, Nakagyo-ku Kyoto JapanAkira Mi...
Source: Radiological Physics and Technology - November 10, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
X-ray fluorescence camera for imaging of iodine media in vivoEmail this article to a colleague.
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Abstract X-ray fluorescence (XRF) analysis is useful for measuring density distributions of contrast media in vivo. An XRF camera was
developed for carrying out mapping for iodine-based contrast media used in medical angiography. Objects are exposed by an
X-ray beam from a cerium target. Cerium K-series X-rays are absorbed effectively by iodine media in objects, and iodine fluorescence
is produced from the objects. Next, iodine Kα fluorescence is selected out by use of a 58-µm-thick stannum filter and is detected
by a cadmium telluride (CdTe) detector. The Kα rays are discriminated out by a multichannel a...
Source: Radiological Physics and Technology - November 10, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Development of a GPU-based multithreaded software application to calculate digitally reconstructed radiographs for radiotherapyEmail this article to a colleague.
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Abstract To provide faster calculation of digitally reconstructed radiographs (DRRs) in patient-positioning verification, we developed
and evaluated a graphic processing unit (GPU)-based DRR software application and compared it with a central processing unit
(CPU)-based application. The evaluation metrics were calculation speed and image quality for various slice thicknesses. The
results showed that the GPU-based DRR computation was an average of 50 times faster than the CPU-based methodology, whereas
the image quality was very similar. This excellent performance may increase the accuracy of patient position...
Source: Radiological Physics and Technology - November 7, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Deriving the modulation transfer function of CT from extremely noisy edge profilesEmail this article to a colleague.
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We describe a technique for rendering the ESF method robust to image noise. We smooth out the noisy ESF
through multiple stages of filtering. Invariably, the line spread function (LSF) obtained from the smoothed ESF is blurred,
and the MTF obtained from the LSF is incorrect. However, because the filtering that has been applied is known, much of the
LSF blurring can be corrected. An estimate of the true LSF is obtainable from the blurred LSF, assuming that the true LSF
is not very different from either a Gaussian or a composite of multiple Gaussians. For an image reconstructed with a kernel
for soft-tissue imaging, the...
Source: Radiological Physics and Technology - October 6, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Use of a clinical MRI scanner for preclinical research on ratsEmail this article to a colleague.
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This study evaluated the feasibility of imaging rat brains using a human whole-body 3-T magnetic resonance imaging (MRI) scanner
with specially developed transmit-and-receive radiofrequency coils. The T1- and T2-weighted images obtained showed reasonable contrast. Acquired contrast-free time-of-flight magnetic resonance angiography
images clearly showed the cortical middle cerebral artery (MCA) branches, and interhemispheric differences could be observed.
Dynamic susceptibility contrast MRI at 1.17 mm3 voxel resolution, performed three times following administration of gadolinium diethylenetriamine pentaacetic acid...
Source: Radiological Physics and Technology - October 1, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
AcknowledgmentEmail this article to a colleague.
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Content Type Journal ArticleDOI 10.1007/s12194-008-0037-y
Journal Radiological Physics and TechnologyOnline ISSN 1865-0341Print ISSN 1865-0333 (Source: Radiological Physics and Technology)
Source: Radiological Physics and Technology - July 22, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Comparison of dosimetric characteristics of 120-leaf and 80-leaf multi-leaf collimators in a Varian linear accelerator for a 6-MV photon beamEmail this article to a colleague.
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In this study, the dosimetric characteristics of multileaf collimators (MLCs) with 120 leaves and 80 leaves were evaluated.
The dose rate, percentage depth dose, surface dose, dose in the build-up region, beam profile, flatness, symmetry, and penumbra
width were measured by three field-defining methods: (1) “Jaw only”, (2) “MLC only”, and (3) “MLC + Jaw”, for a 6-MV photon
beam with the two MLC systems. Analysis of the dose rate showed that the dose rate for the “MLC only” field was higher than
that for the other two fields. The surface dose was more pronounced for the “MLC only” fields. T...
Source: Radiological Physics and Technology - July 14, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Low-dose CT screening for lung cancer with automatic exposure control: phantom studyEmail this article to a colleague.
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Abstract We conducted a study to determine optimal scan conditions for automatic exposure control (AEC) in computed tomography (CT)
of low-dose chest screening in order to provide consistent image quality without increasing the collective dose. Using a chest
CT phantom, we set CT-AEC scan conditions with a dose-reduction wedge (DR-Wedge) to the same radiation dose as those for low-tube
current, fixed-scan conditions. Image quality was evaluated with the use of the standard deviation of the CT number, contrast-noise
ratios (CNR), and receiver-operating characteristic (ROC) analysis. At the same radiation dose...
Source: Radiological Physics and Technology - July 11, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Evaluation of chest and abdominal exposure dose appropriate for a digital image reader system incorporating a columnar-crystal structured phosphor plate and a contrast-detail phantomEmail this article to a colleague.
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Abstract We evaluated a newly developed digital image reader incorporating a columnar-crystal structured phosphor plate (CPP) to determine
its effectiveness for chest and abdominal exposures by assessing contrast–detail (C–D) curves and image quality figure values
obtained from a C–D phantom. With the help of five radiologic technologists with 5 years or more of experience in the interpretation
of plain radiographs, we assessed chest and abdominal radiographic films that had undergone image processing. The exposure
dose required for obtaining the same image quality under chest exposure conditions ...
Source: Radiological Physics and Technology - July 5, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Evaluation of the accuracy of CT numbers in statistical correction of nonlinearity for polychromatic X-ray CT projection dataEmail this article to a colleague.
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Abstract The CT number is theoretically independent of the number of incident photons and the thickness of a subject. However, when
noise is added, the CT number becomes dependent on the number of incident photons because of the nonlinearity of the logarithm
operation, and so the accuracy of the CT number is degraded, especially in a photon-starved state. The inconsistency of the
CT number due to nonlinearity generates an intense streak artifact in a reconstructed image. We have theoretically clarified
the statistical characteristics of both the nonlinearity of the logarithm transform and the non-zero/non-ne...
Source: Radiological Physics and Technology - July 3, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Dosimetric evaluation of nuclear interaction models in the Geant4 Monte Carlo simulation toolkit for carbon-ion radiotherapyEmail this article to a colleague.
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Abstract We tested the ability of two separate nuclear reaction models, the binary cascade and JQMD (Jaeri version of Quantum Molecular
Dynamics), to predict the dose distribution in carbon-ion radiotherapy. This was done by use of a realistic simulation of
the experimental irradiation of a water target. Comparison with measurement shows that the binary cascade model does a good
job reproducing the spread-out Bragg peak in depth-dose distributions in water irradiated with a 290 MeV/u (per nucleon) beam.
However, it significantly overestimates the peak dose for a 400 MeV/u beam. JQMD underestimates ...
Source: Radiological Physics and Technology - June 30, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Automated segmentation of hepatic vessels in non-contrast X-ray CT imagesEmail this article to a colleague.
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Abstract Hepatic-vessel trees are the key structures in the liver. Knowledge of the hepatic-vessel tree is required because it provides
information for liver lesion detection in the computer-aided diagnosis (CAD) system. However, hepatic vessels cannot easily
be distinguished from other liver tissues in plain CT images. Automated segmentation of hepatic vessels in plain (non-contrast)
CT images is a challenging issue. In this paper, an approach to automatic segmentation of hepatic vessels is proposed. The
approach consists of two processing steps: enhancement of hepatic vessels and hepatic-vessel extractions...
Source: Radiological Physics and Technology - June 30, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Evaluation of the spatial resolution of multiplanar reconstruction imagesEmail this article to a colleague.
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We present a simple method for evaluating the spatial resolution of multi-slice computed tomography (MSCT) multiplanar reconstruction
images (MPRs). We scanned a bead phantom to obtain the three-dimensional point spread function (PSF), and bead-centric MPRs
were generated. The modulation transfer function (MTF) was calculated from the MPRs via a two-dimensional Fourier transform
(2DFFT) of the PSF. The results showed that, when MPRs were reconstructed using axial images less than or equal to a nominal
1.0-mm slice-width with a standard kernel for the abdomen, the MTF in the longitudinal direction (z-direction) was supe...
Source: Radiological Physics and Technology - June 26, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Application of breath-holding SPECT with high-speed-rotation technique in hepatic-function scintigraphyEmail this article to a colleague.
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Abstract Recently, a new method for acquiring SPECT data in deep inspiratory breath hold with a high-speed rotation (HSR-SPECT) technique
was developed for pulmonary perfusion scintigraphy. Our purpose in this study was to apply this method to hepatic-function
scintigraphy. A phantom study was performed for determining data acquisition times. The coefficient of variation (CV) value
was used for evaluating nonuniformity of radioactivity in the liver area. Data acquisition times were determined based on
the CV value. According to the results of the phantom study, this method needs at least ten projection data ...
Source: Radiological Physics and Technology - June 24, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Optimal timing of MR sialography by use of a simple method of stimulating the salivary gland: a preliminary reportEmail this article to a colleague.
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Abstract The present study was performed for determining the optimal timing of MR sialography by use of the Japanese pickled plum (umeboshi) for promoting secretion by the salivary glands. MR sialography was performed in four healthy male volunteers. The four volunteers
were examined before and 10 min after stimulation with umeboshi. On the next examination, three volunteers were examined before and after umeboshi stimulation every 1 min up to 5 min to allow assessment of the temporal changes in duct visualization. Dilatation of the
salivary gland ducts and improvement of the visualization of th...
Source: Radiological Physics and Technology - June 24, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Method for reducing noise in X-ray images by averaging pixels based on the normalized difference with the relevant pixelEmail this article to a colleague.
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Abstract A real-time digital filter for noise reduction in X-ray images is proposed. The filter is based on averaging of only similar
pixels (pixels that differ only little) rather than neighboring pixels, which are averaged in conventional linear low-pass
filters. The effectiveness of the filter was evaluated by computer simulation, where original images that were acquired by
X-ray exposure were processed in accordance with the filter algorithm. The resulting images were evaluated in terms of the
pre-sampled modulation transfer function (MTF), the noise power spectrum (NPS), and the lag. Comparison of the f...
Source: Radiological Physics and Technology - June 20, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Analysis method of noise power spectrum for medical monochrome liquid crystal displaysEmail this article to a colleague.
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Abstract We investigated methods of analyzing the noise power spectrum (NPS) measurement for medical liquid crystal displays (LCDs).
Uniform images displayed on the LCDs were imaged with a high-performance digital camera equipped with a close-up lens, and
then the NPSs were calculated from the image data by means of several analysis methods. In a method using the 2D fast Fourier
transform (FFT) with a 256 × 256 pixels data segment (basic method), we examined the efficacy of a background trend correction
(BTC) and a Hanning windowing process used for reducing the spectral estimation errors in ...
Source: Radiological Physics and Technology - June 16, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
Customization of normal data base specific for 3-tesla MRI is mandatory in VSRAD analysisEmail this article to a colleague.
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Abstract A voxel-based specific regional analysis system for Alzheimer’s disease (VSRAD) was used for quantitative analysis of parahippocampal
atropy with 1.5-tesla (T) MRI in a voxel-wise manner. The analysis of images acquired under a different imaging condition
provides an error factor that has a calculated value. Clinical application of 3T-MRI is necessary for establishing a normal
data base (N-DB) specific for 3T-MRI data, which permits appropriate application of VSRAD. We established an N-DB specific
for 3T-MRI for use in VSRAD. The “Z-score of the parahippocampal gyrus” was 0.79 ± 0.3...
Source: Radiological Physics and Technology - June 16, 2008 Category: Physics Tags: Radiological Physics and Technology Source Type: journals
