Purpose: StarGuide (GE HealthCare, Haifa, Israel) is a full-ring SPECT/CT system based on Cadmium Zinc Telluride (CZT) technology. In this study, we aimed to compare the image quality of this CZT-based SPECT/CT to a conventional Anger-type SPECT/CT system (NM/CT 870 DR, 870DR; GE HealthCare). Methods: Tomographic sensitivity was calculated by recording the total number of counts detected during tomographic acquisition for a point source. We evaluated spatial resolution and image uniformity on each system using the full width half maximum (FWHM) of line sources and root mean square uniformity (%RMSU) of pool phantom, respectively. The voxel size of the StarGuide SPECT images was 2.46×2.46×2.46 mm³, compared to 4.42×4.42×4.42 mm³ on 870DR. These projection data were reconstructed using 3D-OSEM with a resolution recovery technique (RR). We compared 3 different algorithms: non-correction (NCRR), scatter correction (SCRR), and attenuation correction and scatter correction (ACSCRR). Results: Tomographic sensitivity of StarGuide and 870DR were estimated at 200.0 counts・s⁻¹・MBq⁻¹ and 193.3 counts・s⁻¹・MBq⁻¹, respectively. Spatial resolution at the center of the FOV was estimated at 2.6 mm for StarGuide and 5.4 mm for 870DR with ACSCRR. Likewise, the %RMSU was 21.7 for StarGuide and 24.6 for 870DR. Conclusion: The full-ring CZT SPECT/CT system has a superior spatial resolution and better image uniformity than the conventional Anger-type SPECT instrument, whereas tomographic sensitivity remains similar.

Purpose: The purpose of this study is to clarify the amount and distribution of scattered radiation in portable dynamic chest radiography (DCR) compared to portable conventional chest radiography (CCR), and to consider appropriate operation methods. Methods: Using a portable X-ray unit, we evaluated the imaging time characteristics in DCR and obtained the scattered X-ray dose distributions of DCR and CCR. The scattered X-ray dose was measured 200 cm from the irradiation field center, varying DCR imaging time (5, 10, 15 s). Scattered X-ray dose distribution was measured at 48 points between 100–300 cm from the irradiation field center for CCR and DCR (10 s). DCR (15 s) values were calculated from DCR (10 s) measurements. DCR 15 s was calculated from the calculated values for each measured value of DCR 10 s. Measurements were taken at the level of the abdomen and the lens. Results: It was found that the amount of scattered X-ray was higher with DCR than with CCR, and that the amount of scattered X-ray increased with increasing imaging time. In addition, the distribution of scattered X-rays with DCR showed a tendency for the amount of scattered X-rays to decrease behind the mobile X-ray unit and at the foot of the bed. Conclusion: When taking portable DCR images, radiologists must understand its characteristics and the scattered X-ray dose distributions, and must be even more considerate of and manage the surrounding area based on the 3 fundamental principles of radiological protection.

Purpose: We investigated the relationship between dose variation and gamma analysis pass rate in in vivo dosimetry (IVD) and verified the detectivity of errors by using the tolerance of the pass rate determined on a dose variation basis. Methods: We used a treatment planning system and water-equivalent phantoms to simulate discrepancies between treatment planning and actual irradiation. These discrepancies were created by either deforming structures outlined in the phantom’s computed tomography (CT) images or by modifying the CT values within those structures. We performed gamma analysis to compare the intensity distributions of the planned data (including discrepancies) with the distributions acquired by irradiating real phantoms using an electronic portal imaging device (EPID). We investigated the relationship between the gamma analysis pass rate and dose variation with and without the discrepancies. Results: For gamma analysis pass rates below 70%, a dose variation of approximately 5% was estimated. The accuracy of using the pass rate to predict a dose variation of 5% was 86%. In validation of the prediction, when the gamma analysis pass rate was below 70%, differences were detected in clinical cases with an 82% accuracy. Conclusion: A method for determining the tolerance of gamma analysis pass rate based on dose variation in phantoms is useful.

Purpose: Motion artifacts likely occur in patients with acute intracerebral hemorrhage (ICH). This study aimed to validate the image quality characteristics of non-contrast brain computed tomography (CT) with high-speed imaging technology, named Flash spiral (FS) (Siemens Healthineers, Erlangen, Germany). We verified the differences in CT values using a phantom that simulated hematoma. Methods: A dual-source CT scanner (SOMATOM Drive; Siemens Healthineers) was used to obtain reference and FS images of a Catphan700 phantom (The Phantom Laboratory, Greenwich, NY, USA). The CT values were measured in the hematoma-simulated acrylic module and urethane within the phantom. The noise power spectrum (NPS), task transfer function (TTF), and system performance function (SPF) between reference and FS images were obtained to compare image quality in each scan. Results: Compared with the phantom's reference and FS images, no significant differences were observed in the CT values between the samples simulating hematoma and their surrounding areas. The NPS showed lower values in the FS images than the reference images at spatial frequencies above approximately 0.4 cycles/mm, while the peak frequencies were nearly equivalent. The 10% TTF values were almost the same between both images. The SPF values were also equivalent between the two images at spatial frequencies above approximately 0.5 cycles/mm. Conclusion: In the phantom experiment, the 10% TTF values of the FS images were comparable to those of the reference images, indicating similar resolution in the high spatial frequency domain. FS is expected to expand the applicability for detecting cerebral hemorrhage in patients with significant body movement, where detection is challenging under standard conditions.

Purpose: We investigated the factors that influence the eye lens dose to the operator during cardiac catheterization using a cylindrical acrylic phantom, which can place small dosimeters at 3-mm depth from the surface. Methods: A cylindrical acrylic phantom was placed on top of the thoracic phantom, which was used as the operator’s phantom. The absorbed doses at the assumed positions of the eye lenses of the operator’s phantom were measured by two irradiation modes. It was integrated from two projections in fluoroscopy mode. In cine mode, it was integrated from 15 projections. The measurement was performed by changing height of eye lenses (150, 165, and 180 cm), orientation of the cylindrical phantom (0°, 15°, 30°, and 45°), and the position of the operator’s phantom (radial access, femoral access, and the position of the second operator). Results: The lens doses decreased as the phantom height increased. The doses at the left neck were 1.2 to 1.4 times higher than those at the eye lens. The lens doses tended to decrease as the cylindrical phantom was oriented away from the X-ray tube, and it was the highest when the phantom was at the radial access approach position. Conclusions: During cardiac catheterization, the absorbed dose of the operator’s lens depends on the operator’s height, head orientation, and position. If the dosimeter is placed on the neck, the eye lens dose can be conservatively estimated.

Purpose: The objective of this study was to determine the standard settings of the angiography system during EVT in Japan. Methods: Survey requests were mailed to 493 facilities across Japan. The survey items included in the survey were system display dose setting of fluoroscopy dose (FL dose)/digital angiography dose (DA dose)/digital subtraction angiography dose (DSA dose), detector size, fluoroscopy pulse rate, DA/DSA frame rate, and standard additional filter settings. The number of valid responses for each item was system display dose setting: 187 systems (128 institutions), detector size: 187 systems (128 institutions), fluoroscopy pulse rate and DA/DSA frame rate: 185 systems (127 institutions), standard additional filter settings: 182 systems (125 institutions). Results: Median (interquartile range) of each system display dose setting was FL: 5.9 (4.2–7.8) mGy/min, DA: 0.10 (0.06–0.16) mGy/frame, DSA: 0.82 (0.64–1.40) mGy/frame. The detector size for dose measurements was 103 systems (55%) with a diagonal of 35 cm or less and 84 systems (45%) with a diagonal of more than 35 cm. The most used FL pulse rate was 7.5 pulse/s (132 systems: 71%), DA frame rate was 7.5 frame/s (72 systems: 39%), and DSA frame rate was 3 frame/s (97 systems: 52%). More than 90% of the institutions used some kind of additional filter for imaging. Conclusion: This survey showed the standard setting of the angiography system during EVT in Japan.