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To quantify dose delivery errors for high-dose-rate image-guided brachytherapy (HDR-IGBT) using an independent end-to-end dose delivery quality assurance test at multiple institutions. The novelty of our study is that this is the first multi-institutional end-to-end dose delivery study in the world.The postal audit used a polymer gel dosimeter in a cylindrical acrylic container for the afterloading system. Image acquisition using computed tomography, treatment planning, and irradiation were performed at each institution. Dose distribution comparison between the plan and gel measurement was performed. The percentage of pixels satisfying the absolute-dose gamma criterion was reviewed.Thirty-five institutions participated in this study. The dose uncertainty was 3.6% ± 2.3% (mean ± 1.96σ). The geometric uncertainty with a coverage factor of k = 2 was 3.5 mm. The tolerance level was set to the gamma passing rate of 95% with the agreement criterion of 5% (global)/3 mm, which was determined from the uncertainty estimation. The percentage of pixels satisfying the gamma criterion was 90.4% ± 32.2% (mean ± 1.96σ). Sixty-six percent (23/35) of the institutions passed the verification. Of the institutions that failed the verification, 75% (9/12) had incorrect inputs of the offset between the catheter tip and indexer length in treatment planning and 17% (2/12) had incorrect catheter reconstruction in treatment planning.The methodology should be useful for comprehensively checking the accuracy of HDR-IGBT dose delivery and credentialing clinical studies. The results of our study highlight the high risk of large source positional errors while delivering dose for HDR-IGBT in clinical practices.

This study proposes to make effective use of plutonium transmuted from minor actinides (MA) by fusion reactors as fertile fuel in a light water reactor (LWR). The plutonium transmuted from MA, particularly Pu-238, has a large neutron capture cross section and becomes fissile Pu-239 by the reaction. If the plutonium transmuted from MA is loaded into LWR appropriately, there is a possibility to maintain a constant effective multiplication factor. This study evaluated the effects of the plutonium transmuted from MA on a full MOX boiled water reactor (BWR) core by Monte Carlo-based neutron transport and burnup calculation. We revealed that some fuel assemblies achieved the effective multiplication factor is greater than 1.0 and its decrease was significantly small (−0.013) during 400 days operation. However, under this condition, the power peaking factor was 1.4, which should be unacceptable from the viewpoint of thermal design. Inventories of heavy nuclides in fuel cycles was evaluated using a simple diagram and its result indicated that the accumulation of MA in the fuel cycle was reduced by introducing the MA transmutation and the Pu recycle system. Furthermore, the amount of MA production and MA transmutation are balanced by introducing two fusion reactors with 3 GW thermal output into the fuel cycle, and the MA inventory was equilibrated.

This study demonstrates by numerical simulations how transmuting minor actinides in fusion reactors can contribute to nuclear fuel cycles in Japan. Minor actinides are installed into blankets of a helical-type fusion reactor to transmute them rather moderately so that neither large neutron wall loading nor removal of large heat are required. Neutron transport and burn-up simulations are conducted to optimize the position of minor actinides and the blanket's structure for transmutation. Whereas the ratio of transmuted minor actinides is not large, the total amount of transmuted minor actinides is revealed to be sufficient because of the system's large inventory. The simulations are followed by a plan that introduces fusion reactors intended for transmutation. Discussion based on Japan's present situation confirms that introduction of fusion reactors with a thermal fusion output of 1 GW by the year 2050 would mitigate many issues concerning disposal of high-level radioactive waste.

The present study evaluates the thermal design of a blanket system using Flinabe in order to facilitate further discussions on its applicability as a self-cooled liquid blanket system. Molecular dynamics simulations were performed to evaluate the Prandtl number of mixtures in five compositions (LiF–NaF–BeF2 = 31–31–38, 36–27–37, 42–22–36, 49–16–35, and 67–0–33). Thermofluid analysis was carried out to estimate the temperature margin and pressure drop per unit length in a simple geometry model of the blanket system. The Prandtl number of Flinabe is above 100 at 400°C. The present study reveals that Flinabe remarkably relaxes the design conditions compared to Flibe as a coolant owing to its low melting point. In contrast, the pressure drop per unit length of Flinabe is higher than that of Flibe because the viscosity exponentially increases at low temperature. The temperature margin is quite dependent on the heat load on the first wall. If the pressure drop per unit length is around 1.0 MPa/m, the he...

This study evaluates the physical properties of the molten salt Flinabe, using molecular dynamics simulations to discuss its applicability to a fusion blanket system. More specifically, the simulations calculate the density and viscosity of Flinabe to facilitate further discussion of the applicability from the viewpoint of the heat removal of the first wall. The results of the simulations are compared with data reported in earlier publications, which support the validity of the simulations. This study reveals that Flinabe tends to have lower viscosity than Flibe even when they contain almost the same BeF2. Analyzing the results of the simulations confirms that the degree of polymerization in Flinabe correlates with its viscosity, as that in Flibe does. The analyses also revealed, however, that the correlation in the case of Flibe is not directly applicable to the case of Flinabe.

This study discusses the applicability of eddy current testing to the non-destructive evaluation of the depth of a flaw. Three-dimensional finite element simulations are carried out to calculate eddy current signals due to a flaw, and subsequent calculations correlate the difference between signals due to two flaws with the difference between the depths of the flaws. Standard deviation of the difference between the depths of the flaws is used to discuss the ill-posedness of the problem. A flaw is modeled as a sufficiently long rectangular region with a constant width and uniform electrical conductivity; an absolute pancake probe is considered. This study reveals that lift-off and coil diameter do not have a large effect on the ill-posedness, which supports that it is reasonable to decide parameters in actual inspections so that signal-to-noise ratio is maximized. The results obtained also indicate the difficulty in evaluating the depth of a flaw deeper than 1 mm using the signals obtained using an absolute pancake probe.

PURPOSE We measured T2 relaxation time of the intervertebral discs (IVD) and facet joints (FJ) in patients with degenerative spondylolisthesis (DS) and no spondylolisthesis (NS) and investigated the characteristics of these parts in DS. METHODS In 40 patients with DS and 40 patients with NS, we measured T2 relaxation time of the IVD and FJ and compared them between groups. In the group with DS, we also examined the relationship between the degree of slippage using Meyerding grade and T2 relaxation of each part in the IVD and FJ. RESULTS T2 relaxation time of the IVD tended to be lower in the DS than NS group and differed significantly (P < 0.01) within the anterior annulus fibrosus. T2 relaxation time in the FJ was significantly higher in the DS than NS group. T2 relaxation time in the FJ was significantly higher for those assessed Meyerding Grade II than Grade I, although we observed no significant differences in T2 relaxation time in any area of the IVD. CONCLUSION T2 relaxation time decreased in the anterior annulus fibrosus of the IVD and increased in the FJ in patients with DS, suggesting an association of IVD and FJ degeneration with the development of lumbar DS.

The objective of our study was to optimize magnetic resonance image (MRI) sequences and parameters using operative assisted images (three-dimensional images) for radical prostatectomy at 3 tesla (T) MRI. Five healthy volunteers underwent MRI on the 3.0 T scanner. Various sequences and parameters [Cube (TE/TR = 18, 50, 90 ms/2000 ms), FIESTA (TE/TR/FA = 2.4 ms/5 ms/40 degrees, 90 degrees), fSPGR (TE/TR/FA = 2.3 ms/11.2 ms/20 degrees), slice thickness = 1.2 mm, matrix = 192 x 160] were respectively compared. Several structures of the pelvis (the central zones and transition zones of the prostate, the peripheral zones of the prostate, seminal vesicles, rectum wall, bladder, muscle and fat) were determined. The signal intensities of these structures were measured on reformatted axial images and compared against several structures of the pelvis. Correlation with various sequences and parameters was based on the signal-to-noise ratio (SNR), the contrast ratio (CR) and the presence of artifacts. Student's t-test was used for statistical analysis. With Cube (TE/TR = 50 ms/2000 ms), the average value of visual evaluation with artifacts was high, and SNR and CR were higher than for other sequence and parameters. Optimized MRI sequences and parameters were Cube (TE/TR = 50 ms/2000 ms) which provides improved SNR and CR and the presence of artifacts with operative assisted images for radical prostatectomy. These operative assisted images obtained from Cube (TE/TR = 50 ms/2000 ms) are likely to be useful for surgery.

Muscle proton magnetic resonance spectroscopy (MRS) has been developed for non-invasive measurement of intramyocellular lipid (IMCL) levels. The majority of previous studies measuring IMCL with MRS have been performed on the calf muscle. The appearance of muscle MRS is influenced by bulk magnetic susceptibility and residual dipolar couplings, which depend on the angle between the muscle fibers and the main magnetic field. Our objective in this study was to evaluate the effect of ankle flexion and of the pennation angle on IMCL quantification in the calf muscle using proton MRS. The subjects comprised ten healthy male volunteers. In proton MRS, the ankle flexion angle was changed, and the pennation angle was measured from the tibialis anterior (TA) and the medial gastrocnemius (MG), respectively. We considered the relationship between the quantification of IMCL with (1)H MRS and the pennation angle by ankle flexion angle. The pennation angle of the TA and MG changed with the ankle flexion angle. The IMCL on the TA decreased significantly with plantar flexion (p 0.05). However, the IMCL on the MG demonstrated no significant difference. The MR spectrum and IMCL quantitation changed with the pennation angle. Therefore, when spectra of individual subjects in longitudinal studies or between subjects are compared in cross-sectional studies, the foot position or calf muscle orientation must be considered.

Identification of the compression factor in cervical disc herniation and cervical spondylotic radioculopathy is often problematic when using two-dimensional magnetic resonance imaging (MRI). This prompted us to compare and examined three-dimensional sequences, coherent oscillatory state acquisition for the manipulation of image contrast (COSMIC), fast imaging employing steady state acquisition (FIESTA) and T2 star weighted MR angiography (SWAN) with 3.0-Tesla (T) MRI to visualize the foramen intervertebral nerve root for the cervical spine. Fat-suppressed COSMIC (FS-COSMIC) sequence gave the highest signal intensity ratio (1.85 ± 0.06) of the nerve root and vertebral arch. A significant difference in signal intensity ratio of the nerve root was found between FS-COSMIC and FIESTA sequences. No significant difference was found between the FS-COSMIC and FIESTA sequences in the cerebrospinal fluid and the spinal cord. The FS-COSMIC sequence proved to be the most suitable sequence for intra and extra dura matter.

This study proposes LiF-BeF2-LiI as a molten salt for a liquid blanket system of a fusion reactor. Firstly, the melting point of LiF-BeF2-LiI is measured as a function of the molar ratio of LiI. The experimental results confirmed that the melting point decreases to 398.2 °C when LiF:BeF2:LiI = 19:9.5:71.5, which is consistent with an earlier report. Experiments to evaluate the density and viscosity of LiF-BeF2-LiI are also carried out. The experiments revealed that the density of LiF-BeF2-LiI increases with the molar ratio of LiI, and the viscosity of LiF-BeF2-LiI (LiF:BeF2:LiI = 2:1:1) is somewhat larger than that of LiF-BeF2 (LiF:BeF2 = 2:1) but much smaller than that of LiF-BeF2 (LiF:BeF2 = 3:2). Monte Carlo numerical simulations using MVP-2.0 with JENDL-4.0 data library are conducted on the basis of the measured density to discuss the feasibility of a blanket system using LiF-BeF2-LiI. The numerical simulations demonstrate that LiF-BeF2-LiI can realize TBR>1.4, which is required for a fusion blanket system, with Be pebble layer and enriching 6Li.Copyright © 2013 by ASME

Coronary vasomotor response might be impaired in metabolic syndrome (MS); however, the precise abnormality has not been elucidated. The aim of this study was to assess coronary-vasomotor response in MS subjects using N-13 labeled ammonia and positron emission tomography.Myocardial blood flow (MBF) was measured at rest and during adenosine infusion in MS subjects (n = 13, MS group) with no definite evidence of heart disease and in subjects without MS (n = 14, non-MS group). Coronary vascular resistance (CVR) was calculated by dividing the mean aortic blood pressure by MBF. Myocardial blood flow reserve (MFR) was calculated as the ratio of the MBF during adenosine infusion to that during rest. Blood chemical parameters were measured to evaluate their relationship with MFR. During adenosine infusion, MBF was lower (p = 0.0085) and CVR higher (p = 0.0128) in the MS group than in the non-MS group and MFR was significantly lower in the MS group than in the non-MS group (2.13 +/- 0.99 vs. 3.38 +/- 0.95, p = 0.0027). Multivariate analysis demonstrated that the homeostasis model assessment-insulin resistance (p0.05) and the presence of hypertension (p0.05) were independent determinants of MFR.The results indicate that MFR was impaired in MS subjects, suggesting that an abnormal coronary microvascular response occurred in these subjects. This abnormality may have been partially due to insulin resistance and hypertension.

Study Design: Prospective study based on magnetic resonance (MR) imaging of the lumbar spinal root of the intervertebral foramen. Purpose: This study was to compare MR three-dimensional (3D) sequences for the evaluation of the lumbar spinal root of the intervertebral foramen. Overview of Literature: The diagnosis of spinal disorders by MR imaging is commonly performed using two-dimensional T1- and T2-weighted images, whereas 3D MR images can be used for acquiring further detailed data using thin slices with multi-planar reconstruction. Methods: On twenty healthy volunteers, we investigated the contrast-to-noise ratio (CNR) of the lumbar spinal root of the intervertebral foramen with a 3D balanced sequence. The sequences used were the fast imaging employing steady state acquisition and the coherent oscillatory state acquisition for the manipulation of image contrast (COSMIC). COSMIC can be used with or without fat suppression (FS). We compared these sequence to determine the optimized visualization sequence for the lumbar spinal root of the intervertebral foramen. Results: For the CNR between the nerve root and the peripheral tissue, these were no significant differences between the sequences at the entry of foramen. There was a significant difference and the highest CNR was seen with COSMIC-FS for the intra- and extraforamen. Conclusions: In this study, the findings suggest that the COSMIC-FS sequences should be used for the internal or external foramen for spinal root disorders.

The purpose of this study was to determine the best bed overlaps in PET/CT 3D acquisition to reconstruct a transverse image with uniform quality not depending on axial slice position. First, the value of the image contrast ratio, non-uniformity (NU) value, and coefficient of variation (COV) were examined in the image of a cylindrical phantom at each slice position. The image-contrast ratio was almost constant in all slice images, and the NU value and COV were also constant in the slice images up to 13 and 19 slices from the center, respectively, but these values increased with closeness to the edge of the detector. Secondly, COV and image contrast ratios at different sizes of (18)F-FDG concentration (phi 19 mm, phi 16 mm, phi 13 mm, phi 10 mm) were examined in the case of overlapping the bed frame with 11, 15, and 21 slices in acquiring data in 3D mode. In 21 and 15 slices overlapping in acquisition, the image contrast ratios for all concentrations were greater than 0.13, which was the threshold image contrast ratio needed to identify FDG concentration from the background image with naked eye scanning under our conditions. However, in 11 slices with overlapping acquisition, the image-contrast ratio for a phi 10 mm concentration were close to or less than 0.13 in the all slice images. As a result, 15 overlapping slices was a reasonable minimum number of slices to identify a phi 10 mm (18)F-FDG concentration while maintaining the image quality in PET/CT 3D acquisition in our institution.