Nihon Hoshasen Gijutsu Gakkai zasshi最新文献

Purpose: The purpose of this study was to perform auto-segmentation on cases in the head and neck region and to elucidate the characteristics of the extraction performance.

Methods: Auto-segmentation was performed on 100 cases in the head and neck region in Japan. The Auto-segmentation contours were compared with the clinical contours. The evaluation structures were the brain, brainstem, spinal cord, mandible, parotid gland, larynx, and eyeballs. DSC and HD were used for similarity evaluation.

Results: Overall, there was a high similarity in the eyeball and spinal cord. However, the lower the contrast with neighboring objects and the greater the variation in shape, the lower the similarity. In addition, metal artifacts lowered the similarity in some areas.

Conclusion: When auto-segmentation extraction was performed, differences were observed in the degree of similarity between organs. Depending on the case and morphology, the accuracy of auto-segmentation extraction varied from site to site, even for the same organ. The characteristics of the extractability found in this study make it useful for the manual modification of contouring.

Purpose: This study aimed to clarify the effects of radiopharmaceuticals and buffer solutions on the accuracy of the Hoffman phantom examination.

Methods: The Hoffman phantom was prepared using the water immersion method and was injected with 3 different solutions: ¹²³I-MIBG, ¹²³I-IMP only, and ¹²³I-IMP plus buffer solution. Single photon emission computed tomography (SPECT) / computed tomography (CT) imaging was performed at 3-time points: immediately after encapsulation, after 10 min of stirring, and after 20 min of stirring. The relative SPECT counts and left-right ratios of the images obtained under each condition were evaluated.

Results: The results revealed that the buffer solution facilitated the mixing of ¹²³I-IMP, affecting the initial distribution of the radiopharmaceutical. However, after 20 min of stirring, no significant differences were observed in the relative SPECT counts and the left-right ratio of SPECT images among the different solutions, regardless of the radiopharmaceutical type or the presence of the buffer, in most regions.

Conclusion: Buffer solution promotes the mixing process; however, it was confirmed that sufficient agitation alone can produce comparable SPECT images, indicating that the use of a buffer may not be necessary if proper agitation is ensured during phantom preparation.

When performing magnetic resonance imaging (MRI) scans, MRI compatibility must be confirmed as well as the presence of implantable devices in the body prior to scanning to prevent or minimize adverse events. In addition, medical staff must prepare for the risks of MRI scans through a complex process that includes checking for the presence of implanted metals in the body and non-medical materials such as tattoos and permanent cosmetics, which makes it important to update information and review the system at one's own institution. This study conducted a questionnaire survey of 950 facilities in Japan that perform MRI examinations of patients with implantable devices. 622 facilities responded to the survey. The response rate was 65.5%. The survey on the system for conducting MRI examinations of patients with implantable devices revealed the percentage of patients who are ready for each implantable device and the occupations involved in changing the mode of each device and providing informed consent before the MRI is performed. The survey on the checklist of in-vivo and out-of-vivo MRI devices used to pre-confirm the presence of metals in the body revealed the percentage of patients who use the checklist and the types of jobs that are involved in the interview process. Furthermore, it was found that there was a large variation in the content of items checked on the MRI intra- and extra-intracorporeal metal checklists among institutions. It is hoped that learning about the actual conditions at other facilities will help to further reduce the risks associated with MRI examinations by reviewing the implementation systems and checklist contents at their own facilities.

Purpose: The purpose of this study is to create teaching materials that visualize the direction of scattered radiation as directional vectors in a virtual reality (VR) space.

Methods: The directional vector distribution of scattered radiation during X-ray fluoroscopy was created using the Particle and Heavy Ion Transport code System (PHITS), a Monte Carlo code. The directional vector distribution of scattered radiation was visualized as red arrows using the three-dimensional visualization software ParaView (Kitware, Clifton Park, NY, USA), and the directional vector distribution of scattered radiation was confirmed using the VR headset Meta Quest 3 (Meta Platforms, Menlo Park, CA, USA).

Results: The direction of the scattered radiation was visualized three-dimensionally in the VR space and checked from any direction. The effect of the protective plate was also confirmed by superimposing it on the dose distribution.

Conclusion: Visualization of directional vector distribution in VR space is useful as an educational tool that allows the direction of the scattered radiation to be grasped in relation to the position of the fluoroscopy system, patient phantom, protection plate, and the user.

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.