Nihon Hoshasen Gijutsu Gakkai zasshi最新文献

Purpose: At our institution, the method previously used for bladder filling in prostate cancer radiation therapy involved drinking 500 ml of water and voiding 30 minutes prior to treatment. However, achieving consistent bladder volume had been challenging. We therefore developed and evaluated a new protocol.

Methods: The new method involves drinking 200 ml of water 2 hours before treatment, followed by voiding, and then drinking another 200 ml of water 1 hour prior. Bladder volumes during treatment planning computed tomography (CT) and during treatment were measured using an ultrasound device and compared between the method previously used at our institution and the new method. Ten patients were evaluated for each protocol.

Results: The mean bladder volumes at the time of planning CT and during treatment were 247.4±99.6 ml and 315.7±158.2 ml, respectively, with the method previously used at our institution, and 201.5±33.0 ml and 192.6±37.2 ml, respectively, with the new method. The new protocol resulted in more consistent bladder volumes.

Conclusion: The newly developed protocol achieved bladder volumes within the range of 100-250 ml, improved reproducibility at the time of treatment, and is expected to enhance workflow efficiency.

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: 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: 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: 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.