Radiological Physics and Technology最新文献

In therapy with Synchrony® mounted on Radixact®, the fiducial marker (FM) and adrenal gland metastasis, which shift with respiratory phase, require margin compensation for high-dose prescriptions. Although compensation is critical, no studies have examined the margin to compensate for the respiratory phase shift. Therefore, we aimed to suggest the compensating margin for the FM and adrenal metastasis shift along with respiratory phase. We used images from four-dimensional computed tomography (4DCT) taken twice and gated CT taken once before therapy initiation with available contour data for FM and adrenal gland metastasis in each image. The distance between the FM and the center of the gross tumor volume (GTV) in each image of a ten-set 4DCT was defined as the correlating association, and a relative cumulative frequency distribution was created based on it. The values of the margins compensating for respiratory displacement were obtained from the relative cumulative frequency distribution in the right-left/posterior-anterior/superior-inferior (S-I) directions. In cases wherein the FM was placed inside the GTV, the margin values decreased in the S-I direction.

To quantify radiation dose reduction in radiotherapy treatment-planning CT (RTCT) using a deep learning-based reconstruction (DLR; AiCE) algorithm compared with adaptive iterative dose reduction (IR; AIDR). To evaluate its potential to inform RTCT-specific diagnostic reference levels (DRLs). In this single-institution retrospective study, 4-part RTCT scans (head, head and neck, lung, and pelvis) were acquired on a large-bore CT. Scans reconstructed with IR (n = 820) and DLR (n = 854) were compared. The 75th-percentile CTDI_vol and DLP (CTDI_IR, DLP_IR vs. CTDI_DLR, DLP_DLR) were determined per site. Dose reduction rates were calculated as (CTDI_DLR - CTDI_IR)/CTDI_IR × 100% and similarly for DLP. Statistical significance was assessed by the Mann-Whitney U-test. DLR yielded CTDI_vol reductions of 30.4-75.4% and DLP reductions of 23.1-73.5% across sites (p < 0.001), with the greatest reductions in head and neck RTCT (CTDI_vol: 75.4%; DLP: 73.5%). Variability also narrowed. Compared with published national DRLs, DLR achieved 34.8 mGy and 18.8 mGy lower CTDI_vol for head and neck versus UK-DRLs and Japanese multi-institutional data, respectively. DLR substantially lowers RTCT dose indices, providing quantitative data to guide RTCT-specific DRLs and optimize clinical workflows.

Rotational cerebral angiography requires accurate dosimetry. The National Cancer Institute Dosimetry System for Radiography and Fluoroscopy (NCIRF), a Monte Carlo-based dosimetry software, can evaluate the organ dose (OD) and effective dose (ED) with higher accuracy than the conventional Monte Carlo software (PCXMC). We estimated the OD and ED for three-dimensional digital subtraction angiography (3D-DSA) and cone beam computed tomography (CBCT) using the NCIRF, reflecting dose variations during rotational cerebral angiography. The 3D-DSA and CBCT simulation parameters were obtained by rotational imaging of a physical head phantom using the Artis Q biplane system. The air kerma area product for each projection was determined based on the ratio of the tube current-time product for each projection; the NCIRF was used with male and female voxel-type reference computational phantoms. To validate the simulation results, the lens dose of the phantom was measured using radiophotoluminescence glass dosimeters and compared to the simulated lens dose. The highest ODs were delivered to the brain: 8.8 mGy (males) and 11.6 mGy (females) in 3D-DSA and 50.0 mGy (males) and 59.4 mGy (females) in CBCT. The EDs were 0.27 mSv (males) and 0.35 mSv (females) in 3D-DSA and 1.49 mSv (males) and 1.83 mSv (females) in CBCT. Lens doses differed within 8.0% between measurements and simulations, with 45.9-65.5% overestimation in simulations that did not account for dose variability. Simulations that considered dose variability using the NCIRF more accurately estimated OD and ED in rotational cerebral angiography.

Accurate lateral knee radiographs are essential for assessing pathology and planning surgery. However, achieving adequate femoral condyle overlap is technically challenging because of individual variations in lower limb alignment. We analyzed the alignment-dependent bone morphology and proposed practical X-ray tube angles to optimize lateral imaging. Full-length lower limb radiographs of 212 normal and 191 knees with osteoarthritis (KOA) were examined. The lateral distal femoral angle (LDFA) and medial proximal tibial angle were measured to classify the alignment into varus, neutral, and valgus types. The LDFA increased with varus alignment in both the normal (89.1°, 88.0°, and 85.2°) and KOA knees (90.2°, 88.0°, and 85.0°). The joint line orientation consistently exhibited an apex-distal pattern. The distal femoral tangent angle (θ = 90° - LDFA) ranged from - 0.2° to 5.0°, providing reference targets for X-ray tube inclination. This alignment-based approach improved imaging reproducibility and diagnostic accuracy in both normal and KOA knees.

We evaluated atlas selection methods for multi-atlas-based segmentation (MABS) in breast cancer radiotherapy planning. Forty-five patients were divided into 30 atlas and 15 test cases. The 30 atlases were stratified into three groups based on breast separation, height, and volume. Firstly, MABS was performed on each of the 30 atlas cases using the remaining 29 atlases. Secondly, MABS was performed on 15 test cases using the 30 atlases. The Dice similarity coefficient (DSC) was calculated to assess the agreement between MABS and manual segmentation. The DSC was found to increase as more atlases were selected. Although this led to an increase in the computational time, the implementation of patient stratification reduced the computational time compared with using the entire dataset. Atlas selection from the height-matched and volume-matched tertile datasets provided median DSC values > 0.9. Breast height may be a practical surrogate for breast volume which is unknown before segmentation.

This study aimed to develop a deep learning-based method for automatic segmentation of the pharyngeal area (PA) and measurement of the pharyngeal contraction ratio (PCR) during deglutition using cine magnetic resonance imaging (MRI). The proposed algorithm combines PA region extraction by a 2D U-Net with automatic calculation of PA and PCR. Segmentation performance was evaluated using the Dice coefficient (DC), and the PCR measured by the model ([Formula: see text]) was compared with that obtained manually ([Formula: see text]) using correlation and Bland-Altman analyses. Cine MRI data of 20 healthy adults (10 men, 10 women; age 22-29 years) were analyzed. The average DC in the test cases was 0.890 ± 0.025, and the PA of the model correlated well with the manual reference (r = 0.70-0.97). The mean [Formula: see text] was 0.105 ± 0.035, consistent with values reported in videofluoroscopic swallowing studies. These results demonstrate the technical feasibility of automatic PCR measurement from cine MRI using deep learning.

The use of radioprotective glasses alone may not reduce radiation sufficiently to protect the eyes of endoscopists performing endoscopic retrograde cholangiopancreatography (ERCP). In this study, we aimed to develop a radioprotective side shield that could be attached to radioprotective glasses. Air kerma was measured at the lens surface of an endoscopist phantom using optically stimulated luminescence dosimeters in an arrangement that simulated ERCP. The protective effect of the radioprotective side shield was evaluated by changing three factors: the number of sheets to be layered from 1 to 5, the front-side length of the sheet from 6 to 10 cm, and the rear-side length of the sheet from 5 to 7 cm. By increasing the front length of the sheets to 8 cm, their rear length to 6 cm, and increasing the number of sheets to three with a lead equivalent of 0.14 ± 0.02 mmPb, the air kerma on the ocular surface could be reduced considerably; hence, these changes were implemented. This achieved a dose reduction of 48.2-87.3% compared with the use of radioprotective glasses alone, especially when the endoscopist phantom was rotated 60° and 75° from the direction directly opposite to that of the patient phantom. The results suggest that radioprotective side shields can reduce radiation exposure in the eyes of endoscopists by < 0.03 mGy in 10-min fluoroscopy under most conditions during ERCP.