Nihon Hoshasen Gijutsu Gakkai zasshi最新文献

Purpose: We created a phantom and analysis program for the assessment of IGRT positional accuracy. We verified the accuracy of analysis and the practicality of this evaluation method at several facilities.

Method: End-to-end test was performed using an in-house phantom, and EPID images were acquired after displacement by an arbitrary amount using a micrometer, with after image registration as the reference. The difference between the center of the target and the irradiated field was calculated using our in-house analysis program and commercial software. The end-to-end test was conducted at three facilities, and the IGRT positional accuracy evaluation was verified.

Result: The maximum difference between the displacement of the target determined from the EPID image and the arbitrary amount of micrometer displacement was 0.24 mm for the in-house analysis program and 0.30 mm for the commercial software. The maximum difference between the center of the target and the irradiation field on EPID images acquired at the three facilities was 0.97 mm.

Conclusion: The proposed evaluation method using our in-house phantom and analysis program can be used for the assessment of IGRT positional accuracy.

Purpose: This study aimed to identify disposable items with low amyloid positron emission tomography (PET) agent radioactivity adsorption for accurate injections using a radiopharmaceutical activity supplier.

Methods: First, we investigated disposable items currently used for amyloid PET agent injection. Next, we measured the residual radioactivity rates of amyloid PET agents on three-way stopcocks, extension tubes, butterfly needles, and indwelling needles to identify disposable items with low radioactivity adsorption. Finally, we evaluated the accuracy of amyloid PET agent injection using the selected disposable items and a radiopharmaceutical activity supplier.

Results: The polybutadiene extension tube exhibited a significantly lower residual activity rate than that of the polyvinyl chloride extension tube. Similarly, the indwelling needles showed significantly lower residual activity rate than that of butterfly needles. The dose indicated by a radiopharmaceutical activity supplier was 184.1 MBq, while the dose calibrator measured the radioactivity which flowed into the vial as 170.2 MBq, resulting in an administration accuracy of 8.2%.

Conclusion: To ensure accurate amyloid PET agent injections, we recommend using polybutadiene extension tubes and indwelling needles due to their lower radioactivity adsorption.

Purpose: The purposes of this study were to investigate the number and percentage of items that changed magnetic resonance (MR) safety information labeling for implantable medical devices (IMDs) and to confirm the importance of checking the latest MR safety information database (117 types and 10031 items).

Methods: We investigated the number and percentage of MR safety labeling changed for IMDs in the MR safety information database as of December 2021 and August 2022.

Results: IMDs of MR Safety Unlabeled decreased from 4116 items (41.1%) to 859 items (8.6%). IMDs of MR Conditional increased from 4141 items (41.3%) to 5896 items (58.8%).

Conclusions: Since there have been changes in the MR safety labeling for many IMDs, this study shows that it is important to confirm the latest MR safety information for IMDs.

We have been developing protective equipment for portable radiography in neonatal intensive care units because the portable radiography's X-ray tube is in close proximity to the head of the nurse who is assisting the patient. Although our initial protective-equipment design was highly effective, there were some concerns that it obstructed the view of the patient and was difficult to handle. To overcome this problem, we have developed two new types of protective device: a narrow-type 0.13 mmPb device, 17 cm long and 45 cm wide (weight 200 g); and a wide type with a wider core material, 45 cm long and 25 cm wide (weight 300 g), both of which can be hung from the collimator cover of mobile X-ray equipment. The measured protective effectiveness was 80.6% at head height for the wide type and 76.8% for the narrow type. A survey of nurses regarding the new protective devices revealed no significant differences between the two types in terms of visibility and whether the devices would be an obstacle when assisting patients. The nurses preferred the wider type, which offered better protection. Radiological technologists also liked that both types were easy to handle because the irradiation field could be adjusted even after the device was fitted. Both types of the new protective device are thus expected to be useful in clinical practice in terms of their high protective effect and improved ease of handling.

Purpose: The purpose of this study was to understand the PDD and OAR during electron beam therapy using lead cutout on the body surface.

Methods: The Monte Carlo code PHITS version 3.24 was used to simulate PDD and OAR. The simulation results were compared with actual measurements using a silicon diode detector to evaluate the validity of the simulation results.

Results: The simulated PDD and OAR parameters of the linac agreed with the measured values within 2 mm. When the lead cutout on the body surface was used, all parameters except for R₁₀₀ agreed with the measured values within 2 mm. The cutout sizes of the broad-beam square irradiation fields were 3 cm for 6 MeV, 5 cm for 12 MeV, and 8 cm for 18 MeV when the lead cutout on the body surface was used.

Conclusion: The Monte Carlo simulation was useful for understanding the PDD and OAR of the lead cutout irradiation fields, which are difficult to measure.

The purpose of this study was to investigate the correlation between patient characteristics and contrast enhancement during the hepatic arterial phase (HAP) and portal venous phase (PVP) CT scanning. All were examined using a hepatic dynamic CT protocol; the scanning parameters were tube voltage 120 kVp, tube current 50 to 600 mA (noise index 8.0 HU), 0.5-s rotation, 5-mm detector row width, 0.813 or 0.825 beam pitch, and the contrast material 600 mg/kg iodine. We calculated contrast enhancement (per gram of iodine: ΔHU/gI) of the abdominal aorta during the HAP and that of the hepatic parenchyma during the PVP. There was a significant difference in the contrast enhancement of the abdominal aorta during the HAP (8.6±2.7 ΔHU/gI) and (9.5±1.7 ΔHU/gI) and that of the hepatic parenchyma during the PVP (1.4±0.5 ΔHU/gI) and (2.9±0.5 ΔHU/gI) between male and female patients (p<0.05). A significant positive correlation was seen between the ΔHU/gI of aortic enhancement and age in male and female patients (r=-0.382 and 0.213) (p<0.05). A significant inverse correlation was observed between the ΔHU/gI of aortic enhancement and the height (HT; r=-0.466 and -0.251), total body weight (TBW; r=-0.609 and -0.535), body mass index (BMI; r=-0.505 and -0.465), lean body weight (LBW; r=-0.642 and -0.576), and body surface area (BSA; r=-0.644 and -0.557) (p<0.05 for all) in male and female patients. A significant positive correlation was seen between the ΔHU/gI of hepatic parenchymal enhancement and the patient age in male and female patients (r=0.258 and 0.150) (p<0.05). A significant inverse correlation was observed between the ΔHU/gI of hepatic parenchymal enhancement and the HT (r=-0.487 and -0.321), TBW (r=-0.580 and -0.525), BMI (r=-0.473 and -0.413), LBW (r=-0.615 and -0.576) (p<0.05 for all), and BSA (r=-0.617 and -0.558) in male and female patients. The BSA was significantly correlated with the ΔHU/gI of aortic and hepatic parenchymal enhancement of the hepatic dynamic CT in male patients. However, LBW was significantly correlated with the ΔHU/gI of aortic and hepatic parenchymal enhancement of the hepatic dynamic CT in female patients. Since the patient factors that affect the contrast enhancement of the abdominal aorta and hepatic parenchyma may differ from facility to facility, we should therefore consider reassessing at each facility.

The Japanese Ministry of Health, Labour and Welfare announced about the expansion of duties by the radiological technologists in team medical care in April, 2010, and the importance of image interpretation assistance by the radiological technologists became higher. In that respect, for improvement in ability of image interpretation assistance by the radiological technologists in emergency medicine, we developed a support package for learning of image interpretation assistance (support package) and evaluated the usefulness for learning of image interpretation assistance by questionnaires. The support package included digital imaging and communications in medicine (DICOM) data of case, explainer video of urgent imaging findings, and DICOM viewer. In 100% of evaluators, the support package was useful for urgent imaging findings in emergency medicine. Moreover, 68.9% of the evaluators had an experience helped by learning to use the support package in the clinical site. In conclusion, we confirmed that the support package was useful for learning of image interpretation assistance by the radiological technologists.

Purpose: National diagnostic reference levels in Japan 2020 (DRLs 2020) have been published. In the field of angiography, in addition to the fluoroscopic dose rate, incident air kerma at the patient entrance reference point displayed on the equipment (K_a,r: mGy) and air kerma-area product displayed on the equipment (P_KA: Gycm²) were set. A questionnaire survey was conducted at each facility in the Tokai region to confirm the status of medical radiation dose control in the region.

Method: A questionnaire survey was conducted at each facility in the Tokai region. The items were fluoroscopic dose rate in each area (head and neck, cardiac, chest and abdomen, and limbs), DA and DSA dose rates, and dose area product meter (K_a,r, P_KA) for the main procedures in each area.

Result: The median values in this study were lower than those in the DRLs 2020, indicating that appropriate dose control is being implemented in the Tokai region. The trends of fluoroscopic and radiographic dose rates were different in each area, and there was some variation among the facilities.

Conclusion: We believe that the incorporation of fluoroscopic and radiographic dose rates by area into the DRLs will facilitate more appropriate dose control at each facility in the future.

Purpose: The purpose of this study was to optimize radiopharmaceutical dosage in single-photon emission computed tomography (SPECT) nuclear medicine. Therefore, we examined a variable dose (VD) method using body weight as an index in resting myocardial scintigraphy using a ^99mTechnetium (^99mTc) preparation.

Methods: In this study, we compared the VD method with the fixed dose (FD) method without a variable by body weight. There were 50 patients using the VD method and 50 patients using the FD method. For the VD method, we set the target average count (counts/pixel) per SPECT view. Using the myocardial average count of the FD method, and the estimated intracorporeal radioactivity at the start of the examination, the dose of the VD method, which varies appropriately depending on the body weight, was calculated.

Results: The VD method had less variation in myocardial counting and was closer to the target count than the FD method, and the median dosage decreased.

Conclusion: The VD method suggested the possibility of obtaining a count independent of physique and stable image quality, reducing medical and occupational radiation exposure in resting myocardial blood flow scintigraphy.

Purpose: The purpose of this study was to evaluate the changes in membranous septum (MS) length during the cardiac cycle and by measurement methods using the preoperative computed tomography (CT) images for transcatheter aortic valve replacement (TAVR).

Method: Among 34 consecutive patients who underwent preoperative contrast-enhanced CT for TAVR, we measured MS lengths by three measurement methods (coronal, stretched, and reformatted coronal view method) at 10% intervals in the cardiac cycle.

Result: MS lengths differed between the three measurement methods in all cardiac phases. Moderate correlations were observed between the MS lengths measured by the coronal view method and the other two methods. In contrast, strong correlations were observed between the MS lengths measured by the stretched view method and the reformatted coronal view method. The frequencies of the minimum and maximum MS lengths during the cardiac cycle tended to be highest at R-R 90% and R-R 30%, respectively. The median MS lengths at R-R 90% were smaller than those at R-R 30% in all measurement methods.

Conclusion: The MS length in patients undergoing contrast-enhanced CT for TAVR varies notably depending on the cardiac cycle and measurement methods. When evaluating MS length, it is crucial to consider the measurement method and to perform measurements during diastole in order to evaluate the minimum value during the cardiac cycle.