Nihon Hoshasen Gijutsu Gakkai zasshi最新文献

Increased occupational exposure of radiation workers is a major problem during open reduction and internal fixation (ORIF) of the hip joint, as the surgeon's eye lens is in close proximity to the patient and the X-ray tube. The purposes of this study were to clarify the occupational exposure of radiation workers during ORIF of the hip joint and to examine the need for radiation protection measures. The radiation exposure of radiation workers was evaluated by making an airborne dose distribution map using phantom experiments. The radiation goggles attached with a small optically stimulated luminescence dosimeter were used in clinical practice to measure the lens dose received by the surgeon, and the necessity of radiation goggles was examined. The airborne dose distribution in ORIF of the hip joint showed a wider area of high dose rate during axial fluoroscopy of the femoral neck than during posterior-anterior fluoroscopy. In axial fluoroscopy of the femoral neck, the surgeon was always in the high dose rate range of 10 µGy/min or higher, the nurses were in the dose rate range of 4 to 10 µGy/min, and the radiologic technologists were in the dose rate range of 0.5 µGy/min or lower. The maximum 3 mm dose equivalent to the surgeon per case was 0.38 mSv. In contradiction, radiation goggles were useful in ORIF because they provided approximately 60% shielding. It is advisable to work with radiation goggles to avoid cataracts.

Purpose: Incidents are recommended to be analyzed by root cause analysis (RCA). Our institution also conducts RCA for incidents and takes measures to prevent recurrence. The purpose of this study was to evaluate the effectiveness of countermeasures against the root causes analyzed by RCA in order to prevent recurrence of incidents.

Methods: Since the treatment planning CT scanner was replaced, incidents of failure to zero adjustment the coordinates of the bed position occurred four times during a three-month period. The RCA was used to investigate the root causes of these incidents and to formulate measures to prevent recurrence. To evaluate the effectiveness of the recurrence prevention measures, we collected the number of recurrence of incidents during the first year after the effectiveness of the recurrence prevention measures, and used the chi-square test to determine the significant difference in the probability of an incident occurring at a significance level of 5% or less.

Results: The measures to prevent the recurrence of incidents were to double-check that the coordinates of the bed position were adjusted to zero and to simulate operations based on a work flow that incorporated this double-check. During the first year period following the implementation of these recurrence prevention measures, the number of recurrence incidents was zero, and the probability of their occurrence decreased statistically significantly (p<0.05).

Conclusion: Thorough double-checks and work simulation based on the work flow are effective methods for preventing the recurrence of incidents.

Purpose: In recent years, there has been a growing movement in Western countries toward the abolition of gonadal protection during radiography. The reasons for this recommendation are that there are few reports of increased risk of genetic effects, that the ovarian dose is not due to direct X-rays but due to internally scattered X-rays that cannot be shielded, and that the presence of gonadal protection may adversely affect the automatic exposure control mechanism and may mask important findings. In addition, the gonadal protection is a large high absorber of X-rays, and its presence in the irradiation field may have some effect on image quality, but the effect of the gonadal protection on image quality has not been clarified. In addition, after the abolition of gonadal protection, the optimal irradiation field setting is expected to become even more important to avoid unnecessary exposure. In this study, we investigated the effect of gonadal protection on image quality in frontal hip radiographs of adults with different radiation qualities and clarified the image quality under conditions in which the irradiation field is appropriately narrowed.

Method: Frontal hip radiographs were taken using a human phantom as the subject, and the image quality of the femoral head was evaluated. Two irradiation fields were used: (a) 14×17 inch field and (b) an appropriate field (11.6×15 inch) that does not impair the reference line and image information necessary for reading hip joint images. The imaging tube voltage was set at 70 kV, and conditions for adding a copper filter were also considered. The incident surface air kerma was set to 1.25 mGy. The incident surface dose at this time was sufficiently lower than the diagnostic reference level (2.5 mGy) in Japan and was judged to be appropriate for imaging using an indirect conversion flat panel detector. The image quality evaluation item was the signal difference to noise ratio (SdNR) including scatterers.

Result: The SdNR decreased by 4.6% when a gonadal shield was placed, indicating that the gonadal shield reduced image quality. When the irradiation field size was appropriately narrowed down, SdNR slightly increased or decreased depending on the quality of the imaging material, but the change was small compared to the change in SdNR with and without the gonadal protection shield.

Conclusion: The results of this study confirm that the elimination of gonadal protection in hip radiography has significant advantages, such as reducing unnecessary X-ray exposure while ensuring image quality, when the irradiation field is set appropriately.

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.

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.

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.

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.