Nihon Hoshasen Gijutsu Gakkai zasshi最新文献

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: Beam profiles of enhanced dynamic wedge (EDW), a non-physical wedge, were obtained using EPID and 2D array detector, and the effectiveness of the QA/QC method for EDW using EPID was investigated.

Methods: Using a radiotherapy unit (Clinac iX; Varian Medical Systems, Palo Alto, CA, USA), the EDW beam profile was measured 10 times with an EPID (aS1000; Varian Medical Systems) and a 2D array detector (Profiler2; Sun Nuclear, Melbourne, FL, USA) to evaluate the reproducibility of the set-up and the EDW beam profiles. The beam profiles of the physical wedge were also obtained with EPID and Profiler2 as a comparison for the EDW beam profiles. In addition, EDW irradiation logs were obtained to analyze output fluctuations during EDW irradiation.

Results: Comparing the EPID and Profiler2 reproducibility of beam profiles, the EPID showed better setup position reproducibility, but the Profiler2 showed better EDW reproducibility of beam profiles. The coefficient of variation for the physical wedge reproducibility of beam profiles was equal or smaller for EPID, and for the EDW irradiation log, the variation was more significant for larger EDW angles.

Conclusion: The effectiveness of the QA/QC method for EDW by EPID is high because EPID is considered to capture the EDW variation in detail and the installation accuracy is also excellent.

Purpose: This study aimed to evaluate whether low-dose CT imaging using an Sn filter can provide image quality sufficient for the differential diagnosis of cranial deformities in infants while maintaining an effective dose comparable to that of conventional radiography.

Methods: We calculated the effective dose for both head X-ray imaging and low-dose CT with an Sn filter. Phantom images acquired using a CT scanner equipped with an Sn filter were evaluated for bone suture visibility at various conditions (from 10 mAs to 50 mAs, every 10 mAs) using a 4-point visual grading scale. In addition, a visual assessment of low-dose CT versus standard-dose CT was performed for infants with cranial deformities.

Results: The effective dose for 2-directional X-ray imaging was 0.011 mSv. At 50 mAs, the effective dose for low-dose CT was 0.008 mSv, with good visibility of the bone sutures, showing nearly equivalent effective doses. The visual assessment results did not differ significantly between low-dose CT and normal-dose CT for infants with cranial deformities (P>0.05).

Conclusion: Low-dose CT using an Sn filter can visualize the infant skull at an effective dose equivalent to conventional X-ray imaging, and the image quality was found to be sufficient for the differential diagnosis of cranial deformities.

Purpose: Stent enhancement processing (SV) is an image processing technique that improves the visibility of coronary artery stents, and its usefulness in percutaneous coronary intervention (PCI) has been reported. However, the re-acquisition of image reconstruction errors increases patient exposure dose. This study aims to retrospectively evaluate cases of SV and identify the effect of improving image reconstruction errors using the region of interest (ROI) function of SV.

Methods: The evaluation targets were 584 PCI cases where SV was used from January 2016 to December 2020. SV error was defined as the image reconstruction error in SV imaging. We evaluated the improvement of SV errors by using the ROI function of SV for images that exhibited SV errors. Significant differences in the improvement effect on SV error by using the ROI function of SV were determined using a paired t-test. A chi-squared test was performed to determine the significance of the relationship between each evaluation item and the SV error.

Results: There were 53 cases of SV errors when the ROI function of SV was not used. The ROI function of SV improved SV errors in 52 cases (p<0.05). In addition, there was no significant relationship between SV errors when using the ROI function of SV and each evaluation item.

Conclusion: The ROI function of SV improved the SV error in 98.11% of the cases where the SV error occurred. The ROI function of SV is useful for reducing SV errors.

Purpose: In DRLs 2020, in addition to the fluoroscopic dose rate, air kerma at the patient entrance reference point (K_a,r) and air kerma-area product (P_KA) by types of medical treatment and diseases were set as DRL quantity. We surveyed the current equipment setting dose at each facility and the exposure dose in clinical practice. We considered the optimal DRL classification of K_a,r and P_KA for the next DRLs update.

Methods: We conducted a questionnaire survey of 428 facilities in Japan with angiography devices and analyzed the obtained angiography dose data.

Results: Fluoroscopic dose rate, K_a,r, and P_KA were lower values compared to past studies and DRLs 2020 data, and significant differences were observed in K_a,r and P_KA by procedure.

Conclusion: Equipment setting doses have been optimized at each facility, and it is expected that radiological protection will be optimized by setting DRL values that reflect the current situation.