共找到 20 条结果
暂无摘要（点击查看详情）
暂无摘要（点击查看详情）
暂无摘要（点击查看详情）
暂无摘要（点击查看详情）
暂无摘要（点击查看详情）
Reducing unnecessary retakes is a critical responsibility of radiologic technologists and plays an important role in promoting medical safety by minimizing patient radiation exposure. This study aimed to evaluate the impact of retake visualization using the general radiography management system "RADInsight" and the effectiveness of the educational interventions through periodic retake review meetings. General radiographic examinations performed at our institution from June 2023 to October 2024 were retrospectively analyzed. Retake rates and contributing factors were examined by anatomical region and cause. The overall retake rate significantly decreased from a maximum of 7.5% to 2.1%. Positioning errors were the most frequent cause of retakes, with notable improvements observed in lateral views of the knee and elbow following educational intervention. Inexperienced technologists showed a higher incidence of retakes due to motion artifacts and insufficient exposure. The combined use of RADInsight for retake monitoring and targeted educational intervention effectively reduced retake rates. This approach demonstrated its value as a practical strategy to support radiologic technologist training and reduce patient radiation exposure, thereby contributing to enhanced medical safety. Wider adoption and multi-institutional application are anticipated in the future.
暂无摘要（点击查看详情）
暂无摘要（点击查看详情）
In radiation therapy, the absorbed dose is corrected for changes in the nominal treatment distance using the inverse square law. However, in the case of electron beams, the inverse square law using the nominal treatment distance is invalid. Therefore, an effective source-to-surface distance (SSD) should be determined. The effective SSD must be measured for all electron beam energies and applicator sizes. Here, we calculated the effective SSD using a radiotherapy planning system with an electron Monte Carlo (eMC) calculation algorithm and evaluated its usefulness. The effective SSD was calculated from the absorbed dose ratio at dmax at extended SSDs under 5 gap conditions, using both eMC calculations and LINAC measurements. The consistency between calculated and measured values was evaluated based on the absorbed dose ratio at dmax, effective SSD, and distance correction factor. The difference in the absorbed dose ratio at dmax between eMC calculations and measurements at extended SSDs was within 1.38%, and the effective SSD values agreed within 5.40 cm. Larger discrepancies in effective SSD were observed under conditions of high energy with large field sizes and low energy with small field sizes. The good agreement in absorbed dose ratio at dmax, effective SSD, and distance correction factor between eMC calculations and measurements indicates that effective SSD calculation using eMC is feasible and can be employed for comparative verification against measured values.
The half-value layer (HVL), an indicator of X-ray quality, is defined as the thickness of an aluminum (Al) filter that reduces the air kerma by half and is used to calculate the backscatter coefficient. HVL is determined from the attenuation curve of air kerma using log-linear interpolation. However, there are no references detailing the specific measurement method. This study aims to investigate the impact of varying the interval of Al filters used in the log-linear interpolation on the HVL, using Monte Carlo simulations. The Monte Carlo simulation was performed using Particle and Heavy Ion Transport code System (PHITS) Ver. 3.29. A photon point source was placed in the air, and the rectangular irradiation field was set to 5×5 cm at the detector position. The detector, simulated as a volume of 1 cm3 of air, was positioned 100 cm from the source. The Al filter thickness for the HVL was varied in increments of 0.1 mm. The HVL was calculated by linear interpolation, and the relative error was determined based on the minimum Al spacing. The X-ray tube voltages used were those of the RQR series (40, 50, 60, 70, 80, 90, 100, 120, and 150 kV). The beam qualities obtained from the measurements and the Monte Carlo simulation system were consistent with those specified for the RQR series in IEC 61267 within ±3.5%. The relative error of HVL for each tube voltage determined by simulation ranged from -0.5 to 4.6%, with a mean±standard deviation (median) of 1.12±0.95% (0.88%). The relative error was larger when the difference between the Al filter combinations was large and the interpolation coefficient α was 0.5. When the filter spacing is less than half the HVL, the accuracy of log-linear interpolation in HVL is less than ±1.5% relative error.
This study aimed to verify the contouring accuracy of the artificial intelligence (AI)-based auto-segmentation software Contour+ (MVision AI Oy, Helsinki, Finland) both quantitatively and visually, and to evaluate its clinical validity for the thoracic region in Japanese patients. Ten thoracic radiotherapy cases with lung lesions were analyzed. Contour+ was used to automatically delineate both lungs, trachea, bronchus, esophagus, spinal cord, and heart. Three observers visually evaluated the auto-contours using a five-point scoring system, and the final manually corrected contours were used as the reference to calculate the dice similarity coefficient (DSC), Hausdorff distance (HD), and volume differences. In all cases, the AI auto-contours were evaluated as "clinically acceptable with minor modifications (score ≥3)," with an average score of 4.4. The mean DSC values were 1.00 for the lungs, 0.99 for the trachea, 0.91 for the bronchi, 0.86 for the esophagus, 0.99 for the spinal cord, and 0.99 for the heart, indicating high agreement. The mean HD values were 5.68 mm, 8.72 mm, and 3.30 mm for the bronchi, esophagus, and heart, respectively. The mean volume changes after manual correction were 4.02 cc for the bronchi, 2.55 cc for the esophagus, and 2.58 cc for the heart. AI-based auto-segmentation software Contour+ demonstrated high geometric agreement and clinical validity for major thoracic organs in Japanese patients, suggesting its potential to reduce the contouring workload and promote standardization in radiotherapy treatment planning.
The objective of this study was to evaluate metal artifacts on axial planes without visible metal by simulating postoperative computed tomography (CT) examinations following coil embolization of dural arteriovenous fistulas. Specifically, we assessed the behavior of metal artifacts in the pericoil region and aimed to propose an imaging protocol that minimizes metal artifact occurrence. An intracranial metallic coil phantom was constructed and scanned using two different area detector CT systems. The behavior of metal artifacts around the coil was evaluated according to the axial position of the metal coil, collimation width, reconstruction algorithm, scan mode, and the presence or absence of metal artifact reduction (MAR). We confirmed that CT value elevation occurred on axial planes without visible metal due to artifacts originating from the metallic coil. This phenomenon was observed regardless of coil position, scan mode, or the use of MAR. It also occurred with all reconstruction algorithms except model-based iterative reconstruction. Furthermore, narrowing the collimation width reduced the magnitude of CT value elevation. Because artifacts occurring on axial planes without visible metal may be reduced by using a narrower collimation width, scanning with narrow collimation is recommended for postoperative CT examinations following cerebral aneurysm embolization.
暂无摘要（点击查看详情）
暂无摘要（点击查看详情）