Radiological Physics and Technology最新文献

One radiation protection measure for medical personnel in X-ray fluoroscopy is using radiation protective plates. A real-time interactive tool visualizing radiation-dose distribution varied with the protective plate position will help greatly to train medical personnel to protect themselves from unnecessary radiation exposure. Monte Carlo simulation can calculate the individual interactions between radiations and objects in the X-ray room, and reproduce the complex dose distribution inside the room. However, Monte Carlo simulation is computationally time-consuming and not suited for real-time feedback. Therefore, we developed a new method to calculate the dose distribution with the presence of protective plates instantly using pre-computed directional vectors, named Directional vector-based Quick evaluation method for Protective plates Effects in X-ray fluoroscopy (DQPEX). DQPEX uses a database of dose distributions and directional vectors precomputed by Monte Carlo code, Particle and Heavy Ion Transport code System (PHITS). Assuming the dose at each position was all contributed from radiations in the direction indicated by the directional vector, the dose reduction by the protective plates at the position was determined whether the backtrace line of the directional vector has a intersect with the protective plate or not. With DQPEX, the whole dose distribution in X-ray room with the presence of a protective plate can be computed about 13 s, which is approximately 1/6000 of the full PHITS simulation. Sufficient accuracy of DQPEX to visualize the effect of a protective plate was confirmed by comparing the obtained dose distribution with those obtained by the full PHITS simulation and measurements.

This study aimed to estimate the effective dose and the risk of exposure-induced cancer death (REID), as well as to establish diagnostic reference levels (DRLs) for common CT examinations conducted in Tabriz, Iran. The investigation included adult patients undergoing abdomen-pelvis, brain, neck, sinus, and chest CT scans. Patient data, exposure parameters, and radiation dose metrics, such as volume CT dose index (CTDI_vol) and dose length product (DLP), were collected and analyzed. The results showed significant variations in radiation dose across different centers for the CT scans. The average effective doses for the different CT scans were 5.65, 1.08, 1.40, 0.46, and 3.68 mSv for abdomen-pelvis, brain, neck, sinus, and chest scans, respectively. The REID values ranged from 14 per million (for sinus scans) to 196 per million (for abdomen-pelvis scans). Additionally, the DRL values for CTDIvol were 11.03 (for abdomen-pelvis), 59.52 (for brain), 8.33 (for neck), 17.05 (for sinus), and 7.83 mGy (for chest). Our results showed that most of the investigated CT scans had lower effective doses compared to the literature and the REIDs were estimated to be low. Minimizing radiation risk can be achieved by reducing CT exams and keeping doses as low as reasonably achievable. The local DRLs from this study were comparable to previous reports and can serve as benchmarks for setting national and international DRLs, helping healthcare facilities optimize radiation practices and improve patient safety in diagnostic imaging.

This study investigated the effectiveness of augmenting datasets for super-resolution processing of brain Magnetic Resonance Images (MRI) T1-weighted images (T1WIs) using deep learning. By incorporating images with different contrasts from the same subject, this study sought to improve network performance and assess its impact on image quality metrics, such as peak signal-to-noise ratio (PSNR) and structural similarity (SSIM). This retrospective study included 240 patients who underwent brain MRI. Two types of datasets were created: the Pure-Dataset group comprising T1WIs and the Mixed-Dataset group comprising T1WIs, T2-weighted images, and fluid-attenuated inversion recovery images. A U-Net-based network and an Enhanced Deep Super-Resolution network (EDSR) were trained on these datasets. Objective image quality analysis was performed using PSNR and SSIM. Statistical analyses, including paired t test and Pearson's correlation coefficient, were conducted to evaluate the results. Augmenting datasets with images of different contrasts significantly improved training accuracy as the dataset size increased. PSNR values ranged 29.84-30.26 dB for U-Net trained on mixed datasets, and SSIM values ranged 0.9858-0.9868. Similarly, PSNR values ranged 32.34-32.64 dB for EDSR trained on mixed datasets, and SSIM values ranged 0.9941-0.9945. Significant differences in PSNR and SSIM were observed between models trained on pure and mixed datasets. Pearson's correlation coefficient indicated a strong positive correlation between dataset size and image quality metrics. Using diverse image data obtained from the same subject can improve the performance of deep-learning models in medical image super-resolution tasks.

¹⁶⁷Tm is an effective radioisotope for use in theragnostic purposes. This study aims to find the best alternative routes for producing ¹⁶⁷Tm for appropriate cancer therapy and diagnostics. In this study, we comprehensively analyzed production cross-sections of ¹⁶⁷Tm and investigated the behavior of these reactions using six different level density models and refined optical model potential (OMP) parameters with the nuclear reaction code TALYS 1.96. Using this code, we estimated the specific activity and production yield for promising production routes. For characterizing the ¹⁶⁷Tm isotopes, the energy distribution of ¹⁶⁷Tm was also analyzed for each prominent reaction by particle and heavy ion transport code system (PHITS). The maximum specific activity was estimated as 52.6-75.2 GBq/g with a production yield of 20.2-32.7 GBq/mAh for the route ¹⁶⁹Tm(p,x)¹⁶⁷Tm. The experimental value was reproduced with good agreement by TALYS adjusting different OMP parameters. ¹⁶⁹Tm(p,x)¹⁶⁷Tm is the alternative route for producing ¹⁶⁷Tm, for which TALYS can reproduce the result more accurately.

This study developed a system to reduce the treatment planning time for cervical cancer brachytherapy. An in-house Excel spreadsheet was developed to streamline dosimetric evaluation by combining external beam radiotherapy and brachytherapy doses, while also displaying daily dose constraints, a novel feature of the system. This system was validated in 46 consecutive patients who underwent intracavitary and interstitial brachytherapy using several applicators and required more complex dose calculation procedures than intracavitary brachytherapy alone. The proposed system included contouring and catheter reconstruction using multiple treatment planning systems simultaneously and was integrated with Excel spreadsheets for rapid dosimetric evaluation. The median time required for treatment planning was 36 min (range: 12-72 min), which was a much shorter time than those reported previously. This optimized system demonstrated the potential to increase the efficiency of brachytherapy planning to meet prescribed dose constraints without compromising treatment quality.

Determination of spread-out Bragg peak (SOBP) inside media other than water is important for research or clinical purposes. Current study aims to characterize the optimal "p" values needed for the simulation of proton SOBP inside some dosimetry media using MCNPX Monte Carlo code. Following the provided data by ICRU-49 and applying the Bortfeld and Jette recommendations, the "p" values were determined for muscle, compact bone, and PMMA. Then, "p" values were optimized to reach accurate weight fractions for the Monte Carlo simulation of SOBP curves. Obtained optimal "p" values can produce accurate proton weight fractions for flat SOBP simulation. The slope of the SOBP region was highly dependent on the "p" value, so small changes in this parameter can largely tilt up or down the SOBP. The tabulated optimal "p" values can be reliably used for proton weight fraction determination during the Monte Carlo simulation of the proton beam SOBP curve inside the investigated media.

The objective of this study is to verify whether X-ray can be visualized for imaging scattered radiation sources in X-ray radiography using a semiconductor radiation visualization camera with image processing and to evaluate its characteristics. Measurements were performed using a C-arm X-ray fluoroscopy device with a portable radiation visualization camera. The height of the radiation protective board and size of the irradiation field were the conditions that were varied during X-ray radiography. Based on the data obtained from the radiation visualization camera, output images were created displaying the intensity of the scattered radiation in color, which were then superimposed on the images captured with an optical camera. The scattered radiation generated by the phantom and within the X-ray tube were confirmed. These results indicate the feasibility of using this radiation visualization camera for imaging.

The number of patients requiring breast reconstruction with artificial implants has been increasing, and so is the use of carbon-ion radiotherapy (CIRT). Consequently, a growing number of patients with artificial breast implants are expected to undergo CIRT. Because artificial breasts are composed of a silicone polymer gel with a silicon-oxygen backbone, which differs significantly from human tissues, the stopping power ratio for carbon beams cannot be accurately converted from CT values using standard CT-to-stopping power ratio tables (CT-SP tables). Incorrect stopping power ratios can lead to significant problems in CIRT, including erroneous calculations of carbon beam range. To address this, we measured the CT values and stopping power ratios of three commercial artificial breasts using a 380 MeV/u carbon beam. Our results revealed significant deviations from the CT-SP table values. For instance, calculations for treating lung cancer with incorrect stopping power ratios resulted in errors of approximately 5 mm in range calculations, adversely affecting dose distribution to the target. Although further studies with various products are needed, it is crucial to conduct thorough patient consultations and develop treatment plans using accurate stopping power ratios.

To determine whether visually observed biliary excretion of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) can be used to assess contrast adequacy of hepatobiliary phase (HBP) images. Images of 121 patients undergoing Gd-EOB-DTPA-enhanced magnetic resonance imaging were used. Adequate HBP images were defined as a quantitative liver-spleen contrast ratio (Q-LSC) ≥ 1.5. Visual evaluation was performed to determine if an adequate HBP image could be obtained based on the presence or absence of bile excretion. Common bile duct-paravertebral contrast (CPC) was used to assess the degree of bile excretion, the albumin-bilirubin (ALBI) grade was used to assess liver reserve, and the Q-LSC was used to assess HBP image contrast. The results were used to quantitatively evaluate the relationships of the degree of bile excretion with HBP image contrast and liver reserve. The cases correctly determined by visual evaluation via bile excretion were 80 (66.1%) at HBP 10 min after injection and 89 (73.6%) at HBP 20 min after injection. Among cases with Q-LSC ≥ 1.5 indicating bile excretion, there were 33 cases at HBP 10 min after injection and 86 cases at HBP 20 min after injection. Furthermore, among cases with Q-LSC < 1.5, indicating no bile excretion, there were 47 cases at HBP 10 min after injection and 3 cases at HBP 20 min after injection. Visually observed biliary excretion of Gd-EOB-DTPA is not a criterion for adequate HBP image contrast.