Effects of Iodinated Contrast Agent on Diffusion Weighted Magnetic Resonance Imaging

京都市立病院金沢大学医薬保健研究域保健学系Rationale and Objectives: To evaluate the effects of iodine contrast agent on diffusion signal intensity and apparent diffusion coefficient (ADC) in diffusion-weighted imaging (DWI) studies in magnetic resonance imaging (MRI) examination just after computed tomography (CT) contrast imaging. Materials and Methods: On a 1.5 T MRI scanner, ADC was calculated from the signal intensity of DWI (b = 0 and 1000) using phantoms filled with contrast agent (0, 4.5, 6.0, 9.0, 30, and 60 mgI/mL). We evaluated the signal intensities of DWI and ADC in 10 patients (3 women, 7 men, 35-68 years old) examined by MRI study less than 40 minutes after injection of 100 mL of iopamidol (300 mgI/mL) for CT study. Results: The DWI signal increased until a CT value of 190 HU, but showed no changes above this value. The ADC decreased with increases in CT value. Less than 40 minutes after injection of iopamidol (300 mgI/mL) for CT scan, the signal intensity of DWI was significantly increased and ADC was significantly decreased. Conclusions: It is necessary to recognize the rate of decrease of ADC, because it is dependent on the density of iodine contrast agents. © 2009 AUR

Imaging parameter effects in apparent diffusion coefficient determination of magnetic resonance imaging

金沢大学医薬保健研究域保健学系京都市立病院Purpose: Although an apparent diffusion coefficient (ADC) value is often used for differential diagnosis of tumours, it varies with scanning parameters. The present study was performed to investigate the influence of imaging parameters, i.e., b value, repetition time (TR) and echo time (TE), on ADC value. Methods: The phantoms were scanned using diffusion weighted imaging (DWI) with changing b values (b = 0-3000 s/mm2), TR and TE to determine the influence on ADC. Moreover, ADC of the brain in normal volunteers was determined with varying b values (b = 0-1000 s/mm2). Results: Diffusion decay curves were obtained by biexponential fitting in all phantoms. The points where fast and slow components of the biexponential decay crossed were called turning points. The b values of turning points that crossed from the biexponential curve were different in each phantom. The b values of turning points depended on ADC of fast diffusion component. When ADC is calculated using two b values of front and back for the turning point, the ADC value may be different. Therefore, it was necessary to perform calculations by b value until the turning point to obtain the ADC value of the fast component. In addition, b ≥ 100 was recommended to avoid the influence of perfusion by blood. Furthermore, the choice of long TR and short TE was effective for accurate measurement of ADC. Conclusion: It is important to determine the turning point for measuring ADC. © 2009 Elsevier Ireland Ltd. All rights reserved

Improvement on detectability of early ischemic changes for acute stroke using nonenhanced computed tomography: Effect of matrix size

京都市立病院金沢大学医薬保健研究域保健学系Purpose: It has recently been reported that intravenous recombinant tissue plasminogen activator improves the clinical outcome after acute stroke. Computed tomography (CT) is the standard imaging method used to determine the indication for thrombolysis. However, detection of early ischemic change often results in an increase in local radiation exposure. Therefore, the effects of decreased matrix size and use of a noise reduction filter were evaluated. Materials and methods: The low contrast resolution was compared for different matrix sizes and imaging filters using a contrast-detail phantom. In addition, early ischemic change in clinical images with matrix sizes of 256 × 256 and 128 × 128 processed using three imaging filters (Gaussian, smoothing, and unsharp mask) from 11 patients within 3 h of stroke onset was evaluated by seven radiologists in a blind manner. Results: The use of images with a matrix size of 256 × 256 and processed with the Gaussian filter increased the detection of early signs of acute stroke. Conclusions: This study was performed to determine whether the converted matrix size and use of imaging filters could improve the detectability of early ischemic change on CT images in acute stroke. To reduce the dose of radiation exposure for patients, it was effective to use an optimal noise reduction filter and reasonable matrix size. In particular, changing the matrix size to 256 × 256 was the most effective for detection of early ischemic change in examinations using clinical images. © 2009 Elsevier Ireland Ltd. All rights reserved

The Effect of Susceptibility of Gadolinium Contrast Media on Diffusion-weighted Imaging and the Apparent Diffusion Coefficient

京都市立病院金沢大学医薬保健研究域保健学系Rationale and Objectives: The development of parallel magnetic resonance imaging has resulted in the frequent use of diffusion-weighted imaging (DWI) in clinical medicine, which usually involves the use of contrast medium. However, gadolinium (Gd) contrast medium may have some effect on DWI and the apparent diffusion coefficient (ADC). The present study was performed to determine whether the magnetic susceptibility of contrast medium alters the DWI signal and the value of ADC in some imaging techniques. Materials and Methods: Nonfat suppression DWI, short-time inversion recovery (STIR) combination, and chemical shift selective (CHESS) combination DWI were performed to examine 10 phantoms with gadolinium-meglumine gadopentetate (Gd-DTPA) dissolved at concentrations from 0.0005 to 0.1 mmol in physiologic saline as a contrast medium. The average pixel value and ADC of each method were determined. Results: ADC showed no differences between before and after treatment with contrast medium for all imaging techniques with Gd considered distributed over the whole tumor. The signal intensity did not change on nonfat suppression or CHESS combination DWI, but deteriorated on STIR. Conclusions: ADC was not influenced by the magnetic susceptibility of contrast medium. In addition, it was suggested that the ability of tumor detection may be reduced if STIR is used as fat suppression. © 2008 AUR

Suzaku Observation of the Brightest Broad-Line Radio Galaxy 4C 50.55 (IGR J 21247+5058)

We report the results from a deep Suzaku observation of 4C 50.55 (IGR J 21247+5058), the brightest broad-line radio galaxy in the hard X-ray (> 10 keV) sky. The simultaneous broad band spectra over 1-60 keV can be represented by a cut-off power law with two layers of absorption and a significant reflection component from cold matter with a solid angle of \Omega/2\pi \approx 0.2. A rapid flux rise by ~ 20% over 2 \times 10^4 sec is detected in the 2-10 keV band. The spectral energy distribution suggests that there is little contribution to the total X-ray emission from jets. Applying a thermal Comptonization model, we find that corona is optically thick (\tau_e \approx 3) and has a relatively low temperature (kT_e \approx 30 keV). The narrow iron-K emission line is consistent with a picture where the standard disk is truncated and/or its inner part is covered by optically thick Comptonizing corona smearing out relativistic broad line features. The inferred disk structure may be a common feature of accretion flows onto black holes that produce powerful jets.Comment: 8 pages, 7 figure

Differentiation of hepatic tumors by use of image contrast with T2-weighted MRI

金沢大学医薬保健研究域Differentiation of hepatic tumors is often evaluated in terms of qualitative diagnostic performance. The signal intensity patterns of hepatic masses are known to differ on certain T2-weighted imaging sequences. In this study, we investigated the quantitative analysis of hepatic masses by using an index called the "T2-shine ratio." Fast-spin-echo (FSE), half-Fourier acquisition single-shot turbo spin echo (HASTE), and true-FISP sequences obtained with quick-imaging techniques during a single breath-hold were examined in 74 patients. T2-shine ratios were calculated by use of the signals of regions of interest (ROIs) placed on a tumor and peripheral tissue: the T2-shine ratio is defined as (tumor signal-liver signal)/liver signal. The rate of change in the T2-shine ratio was compared among three sequences of FSE, HASTE, and true-FISP. The T2-shine ratio of FSE deducted from HASTE was significantly higher for hepatic cysts than for other masses. The T2-shine ratio of HASTE deducted from True-FISP was less than zero for hemangioma. For the value that deducted the T2-shine ratio of HASTE from the T2-shine ratio of true-FISP, hemangiomas had a significantly lower value than did cysts and metastases (P < 0.05), but there was no significant difference from hepatocellular carcinomas (HCCs). Although liver cysts, cavernous hemangiomas, and other lesions could be differentiated, it was virtually impossible to distinguish HCCs from metastatic tumors. In conclusion, the quantitative analysis of hepatic tumors was able to differentiate among these lesions by use of the T2-shine ratio. © 2008 Japanese Society of Radiological Technology and Japan Society of Medical Physics

Amplification of Emerging Viruses in a Bat Colony

Concentration and prevalence of coronaviruses and astroviruses increase when bats form maternity roosts and bear young

Deep-vein thrombosis detection rates and consideration of the living environment in a tsunami disaster area during the disaster reconstruction phase: A cross-sectional study

Introduction: Tsunami victims of the Great East Japan Earthquake were screened for deep-vein thrombosis(DVT) in order to compare the DVT incidence rates between temporary and non-temporary housing residentgroups. Material and methods: Lower extremity venous ultrasonography was performed on 290 subjects (64 menand 226 women; mean age = 71.9 ± 7.9 years) at 44 months after the disaster. All subjects completedquestionnaires to gather information about their background factors which included the Kessler PsychologicalDistress Scale: K6. Results: The DVT detection rate was 10.7% in the temporary group. In the non-temporary group, it was 11.3%among the subjects who previously lived in temporary housing. For the subjects who were living in their own homes it was 9.2%. Psychological distress levels measured by K6 were significantly higher in the temporary housinggroup than in the non-temporary housing group. The multivariate analysis showed that the background factorassociated with DVT risk was SV (soleal vein) dilatation in all subjects as well as in the non-temporary housinggroup, while hypertension and use of sleeping pills were found to be the factors in the temporary housing group. Conclusions: DVT detection rates were similar between the temporary and non-temporary housing groups,and were higher than that in the Japanese general population. The psychological distress level of the tsunamivictims measured by K6 was also higher in the temporary housing group than in the non-temporary housinggroup. It is necessary to establish a long-term and awareness-raising disaster victim support system

The ASTRO-H X-ray Observatory

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the high-energy universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV. These instruments include a high-resolution, high-throughput spectrometer sensitive over 0.3-2 keV with high spectral resolution of Delta E < 7 eV, enabled by a micro-calorimeter array located in the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5-80 keV, located in the focal plane of multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12 keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the 40-600 keV band. The simultaneous broad bandpass, coupled with high spectral resolution, will enable the pursuit of a wide variety of important science themes.Comment: 22 pages, 17 figures, Proceedings of the SPIE Astronomical Instrumentation "Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray