Background and purpose In external beam radiotherapy for prostate cancer, inclusion of the seminal vesicles (SV) in the clinical target volume (CTV) is often complicated by considerable SV motion and deformation. This study aimed to investigate the feasibility of predicting patient-specific SV motion using anatomical features surrounding the prostate on planning CT (pCT) images. Materials and methods Interfractional SV motion was quantified using five pretreatment cone-beam CT (CBCT) scans per patient from a cohort of 191 prostate cancer patients. Patients whose SV was not fully covered by a 3-mm margin were assigned to the High SV Motion Group, which served as the target for prediction. A total of 42 anatomical features were extracted from the contours of the prostate, SV, bladder, and rectum on the pCT. Feature selection was performed using Random-Forest Recursive Feature Elimination, and a machine learning model was developed and evaluated using both internal and external patient cohorts. Results Four anatomical features were selected, including those based on the anatomical relationship between the prostate and the SV. Using these features, the best-performing light gradient boosting machine model achieved an area under the receiver operating characteristic curve of 0.724 in the internal test and 0.632 in the external test for identifying patients in the High SV Motion Group. Conclusion This study suggests an association between anatomical features derived from pCT and patient-specific SV motion. Although the current predictive performance is moderate, this approach may help support radiotherapy strategies when the SV is included in the CTV.

In radiology practice, patient body weight is important for contrast media and radiopharmaceutical dosing, radiation dose management, and examination-related workflows, yet it is not consistently available in routine clinical settings. The purpose of this study was to investigate the feasibility of estimating adult body weight using diagnostic CT dose report metrics across CT systems. This retrospective single-center study included 2496 consecutive adults who underwent diagnostic CT on three scanners. Measured body weight served as the reference standard. LightGBM regression was evaluated in three settings: (1) a baseline model using dose report–derived patient size and exposure metrics, including water-equivalent diameter and sex; (2) an extended model additionally incorporating body region and CT system; and (3) scanner-wise cross-validation to assess cross-scanner generalizability. For settings 1 and 2, data were split into training, validation, and test sets (75

18F-FDG PET/CT is crucial for cancer diagnosis; however, respiratory motion often causes misregistration between PET and CT images. This study aimed to evaluate the impact of a custom-made respiratory motion reduction block (RRB) in reducing misregistration and improving image quality in 18F-FDG PET/CT. Methods: The RRB was developed to minimize the effects of respiratory motion. It is a pentagonal block made of Styrofoam designed to compress the upper abdomen. This study included 170 patients who underwent whole-body 18F-FDG PET/CT. Patients were categorized into 4 groups based on the CT and PET scanning technique used: a control free-breathing (FB) group (breath-holding [BH] CT without RRB and respiration-gated [RG] PET), a control RG group (BH CT without RRB with RG PET), a BH RRB group (BH CT with RRB), and a FB RRB group (FB CT with RRB). Various parameters, including the incidence rate and distance of anatomic misregistration, and signal-to-noise ratio, were measured and compared. Results: For the control FB, control RG, BH RRB, and FB RRB groups, the incidence rates of anatomic misregistration between PET and CT images were 47.1%, 27.5%, 34.0%, and 16.7%, respectively. The mean misregistration distances in these groups were 5.1 ± 6.0, 3.1 ± 5.5, 3.8 ± 6.2, and 1.3 ± 3.2 mm, respectively. Furthermore, the RRB improved the signal-to-noise ratio of the liver. Conclusion: The RRB effectively improved registration between PET and CT images. Our approach is cost-effective and provides respiratory motion suppression not only during PET but also during CT scans. The use of RRB with FB PET scanning was found to be more beneficial than respiratory gating.

Patient motion, particularly due to respiration, often introduces image distortions that compromise diagnostic accuracy in myocardial perfusion single-photon emission computed tomography (SPECT). To address this issue, we developed a novel respiratory motion reduction block (RRB) designed to minimize the respiratory motion of the heart. This study aims to evaluate the impact of the cardiac-centered with RRB (CCRRB) orbit, achieved using the RRB, on myocardial perfusion SPECT image quality. SPECT acquisition of a cardiac phantom was performed at the circular, neighboring elliptical (NE), and CCRRB orbits. The CCRRB orbit was achieved with RRB placed in front of the phantom based on the NE orbit. Count profile curves of the lesion and uniform slice images were obtained from the circumferential profile. Lesion contrast, normal accumulation uniformity, and count distortion were calculated from the circumferential profiles. Full width at half maximum (FWHM) was measured in the lateral, anterior, septal, and inferior walls of the myocardium, and both the mean and standard deviation (SD) were calculated. The lesion contrast was the highest in the NE orbit, slightly lower in the CCRRB orbit, and remarkably lower in the circular orbit than in the NE orbit. The uniformity and count distortion were superior for the CCRRB orbits. The SD of FWHM was greater in the circular and NE orbits. The CCRRB orbit effectively improves uniformity in SPECT imaging, preserving lesion contrast and spatial resolution. The CCRRB orbit provides a practical, accessible approach for enhancing image quality in clinical settings.

Dynamic WaveArc (DWA) is a technique used for continuous, non-coplanar volumetric-modulated arc therapy on the Vero4DRT platform. This study aimed to evaluate the application of single-isocenter DWA (SI-DWA) for treating multiple brain metastases by comparing dose distribution and irradiation time with multi-isocenter DWA (MI-DWA) through retrospective treatment planning. Treatment plans were developed for SI-DWA and MI-DWA in 14 cases with 3-5 brain metastases. Parameters assessed included target dose indices, such as conformity index (CI) of the planning target volume (PTV), volumes of normal brain excluding gross tumor volumes (GTVs) receiving a single dose equivalent of 14 Gy (V14), V30%, V20%, V10%, volumes of normal brain, including GTVs receiving a single dose equivalent of 12 Gy (V12), D2% for other organs at risk, and beam-on time. SI-DWA showed inferior CI, V14, and V12 values for lesions with PTV volumes < 1 cc, whereas it performed equivalently to MI-DWA for lesions with PTV volumes >= 1 cc. SI-DWA resulted in higher volumes of normal brain receiving low doses compared to MI-DWA. SI-DWA exhibited significantly shorter beam-on times than MI-DWA. In conclusion, SI-DWA is an effective method for treating multiple brain metastases with PTV volumes >= 1 cc, offering an index of radiation-induced brain necrosis comparable with MI-DWA while allowing for shorter irradiation times.

OBJECTIVES:The aim of this study was to evaluate an influence of post-processing scatter correction in portable abdominal radiography using a low ratio anti-scatter grid (grid). METHODS:To assess tube voltage on portable abdominal radiography, a burger phantom was used to measure for inverse of image quality figure (IQFinv). For evaluation of the influence on using or not the grid, IQFinv were measured. Abdominal phantom radiographies were assessed subjectively, in random order, by six radiologic technologists. The radiographies were performed without scatter correction [IG (-)] and with scatter correction at equivalent for grid ratio 6 [IG (6)] and 8 [IG (8)]. RESULTS:There was no significant decrease in IQFinv with 75 and 80 kV in comparison of 70 kV. Even processing scatter correction, IQFinv with using the grid was significantly higher than that without using the grid. The ability to detect nasogastric tube and stomach gas were significantly better in the scatter correction. Deviation index for IG (6) and IG (8) were significantly lower than that of IG (-). DISCUSSION:Portable abdominal radiographies will be improved image quality by utilizing scatter correction, although, it is necessary to consider the scatter correction processing as this may significant decrease deviation index in the practical situation. CONCLUSION:The post-processing scatter correction should be useful for detection nasogastric tube and stomach gas in portable abdominal radiography.

OBJECTIVES:The aim of this study was to evaluate the effectiveness of scatter correction in the portable chest radiography.METHODS:Digital radiographies were performed without anti-scatter grid (grid), with the scatter correction and with the grid ratio of 3 : 1 in this study. The scatter fraction and the detectability of low contrast signals were measured using the four acrylic phantoms of different thicknesses. The chest phantom radiographs were assessed subjectively, in random order, by six radiologic technologists.RESULTS:The scatter fraction was higher in the no-grid technique, and was lower for the grid technique. The detectability of low contrast signals did not significantly differ between the scatter correction and the grid technique (p>0.05). The area under the receiver operating characteristic curve for the grid technique was higher than that for the scatter correction technique (0.888 vs. 0.855), although no significant difference was found between the grid and the scatter correction technique (p> 0.05). The ability to detect the nasogastric tube was significantly better in the grid technique (p<0.001).DISCUSSION:In the scatter correction technique, the ability of scatter removal increased as the scatter fraction increased. The scatter correction technique was unnecessary to extremely accurate alignment. In addition, patient dose can be reduced by the scatter correction technique.CONCLUSIONS:It seemed to be effective for the scatter correction in the portable chest radiography.

OBJECTIVES:The goal of this study was to assess the diagnostic accuracy of Pixon-processed images in comparison with raw images for computer-assisted interpretation of bone scintigraphy (BONENAVI).METHODS:Whole-body scans of 57 patients with prostate cancer who had undergone bone scintigraphy for suspected bone metastases were obtained approximately 3 h after intravenous injection of 740 MBq (99m)Tc-methylene diphosphonate. We obtained two image sets: raw images and images processed using the Pixon method. Artificial neural network (ANN) values, bone scan index (BSI), number of hotspots and regional ANN value of two images set were automatically calculated by the BONENAVI software. Areas under the receiver operator characteristic curves (AUC) were calculated in patient-based and lesion-based analyses.RESULTS:In ten cases with bone metastases, ANN, BSI and number of hotspots for processed images were equivalent to those in the raw images. However, in 47 cases without bone metastases, ANN, BSI and number of hotspots for processed images showed significantly lower values than those for the raw images (p<0.05). Sensitivity, specificity and accuracy of the raw images were 90.2, 44.7 and 65.9%, and those of the processed images were 90.2, 57.4 and 72.7%, respectively. The AUC for processed images was equivalent to that for raw images.CONCLUSIONS:Specificity and accuracy in the detection of bone metastases showed the Pixon-processed images to have high diagnostic performance. We conclude that the precision of computer-assisted interpretation of bone scintigraphy can be enhanced by using Pixon processing.

We investigated artifacts due to late-arriving contrast medium (CM) during C-arm cone-beam computed tomography. We scanned a phantom filled with water or with 100, 50, or 5% v/v concentrations of CM and then virtually produced CM-delayed projection data by partially replacing the projection images. Artifacts as a function of concentration, percentage of filling time, and size and position of the filling area were assessed. In addition, we used an automatic power injector with different injection delays to inject CM during the scans. A decrease in filling times caused by a lag in CM arrival during the scan resulted in a decrease in pixel values, distortion of the filling area, and appearance of streak artifacts. Even a delay of approximately 20% in CM arrival in the total scan time resulted in obvious distortion of the filling area. The distortion and streak artifacts tended to worsen at higher CM concentrations. Use of a minimum CM concentration based on the purpose of the examination and constant filling at the target region are effective for avoiding these artifacts.

The coherent-scattering distribution is useful for characterization of materials in the medical field, and obtaining this information from a given position in the object is a useful new diagnostic approach. We propose a simpler geometric approach, which requires only a single-direction X-ray beam with no collimator in front of the detector. This method iteratively estimates coherent-scattering profiles from given positions along the beam path, based on the projections positioned at different object-to-detector distances. We confirmed the proposed calculation algorithm by numerical simulation and performed a simple experiment including attenuation correction. The accuracy of matching with the original profiles was dependent on the number of iterations, the distance between the first and second detectors, the distance between two objects, and the shape of the scattering profile. Whereas multiple scattering was the main problem in the experiment, the calculated scattering profiles matched well with the original profile. This technique indicates the feasibility of developing a coherent-scatter imaging system.

The distribution of coherent scatter is useful for determining the structure of a material, hence computed tomography applying coherent scatter has been developed by several authors. To obtain the exact distribution of coherent scatter a monochromatic, high flux, and highly parallel X-ray beam is required, and therefore, this technique is suited for a synchrotron radiation source. If a synchrotron radiation source is used, rotating the source around the patient or even rotating the patient is difficult. We propose a method for the estimation of coherent scatter distributions from any point, by moving only the position of the detector along the beam path. We acquired projection data at different positions along the beam path, and applied the maximum likelihood expectation maximization algorithm. Simulations and experiments were performed to confirm the effectiveness of this method. The estimated scatter profiles were in approximate agreement with that of the original data. Although improvement in accuracy of the estimation is necessary, this new method is useful if the X-ray source cannot be rotated around the patient.

: Coherent-scatter computed tomography （ CT ） is a technique that produces images based on low-angle X-ray coherent scatter. The number of coherent-scatter photons corresponding to the scattered angles is sensitive to the molecular structure, and hence, their contrast properties on CT images are expected to be higher at specific angles. However, very few studies have reported such image contrasts. Therefore, we attempted to evaluate and compare the contrast properties of coherent-scatter CT images with those of conventional CT images. First, simulation studies using coherent-scatter distributions were performed with monoenergetic beams of 30, 60, and 90 keV, and a polyenergetic beam of 40 kV. This was followed by an experimental study using coherent-scatter CT images with a plastic phantom measuring 6 cm in diameter radiated by a polyenergetic beam of 40 kV. The relative contrast in coherent-scatter CT images at a low-scatter angle was higher than that in conventional CT images. This result suggests that coherent-scatter CT is useful in the detection of low-contrast lesions.