Radiological Physics and Technology最新文献

{"title":"Optimization of entrance skin dose assessment: integration of a new mathematical model and Monte Carlo simulation.","authors":"Alex Eclador Ngankem, Cebastien Joel Guembou Shouop, Daniel Bongue, Francis Chamberlain Djoumessi Zamo, Clemence Raïssa Tchatchouang Simo, Odette Ngano Samba, Maurice Moyo Ndontchueng","doi":"10.1007/s12194-026-01089-z","DOIUrl":"10.1007/s12194-026-01089-z","url":null,"abstract":"<p><p>Accurate estimation of entrance skin dose (ESD) is essential for radiation protection and protocol optimization. This study proposes a new analytical formulation for ESD estimation, the New Mathematical Model Equation for ESD (NMME_ESD), which explicitly integrates both technical and geometric beam-formation parameters, notably the ripple factor and anode angle. These parmeters are often neglected in conventional ESD models. A dataset comprising 3800 examinations acquired from four high-frequency X-ray generators was analyzed. NMME_ESD predictions were compared with experimental measurements, Monte Carlo simulations using PHITS, and the Davies and Edmonds models. The ripple factor and anode angle influence on ESD was evaluated using sensitivity analysis based on Friedman tests and Wilcoxon signed-rank post-hoc comparisons. NMME_ESD predictions showed strong agreement with both experimental measurements and PHITS simulations (with deviations of ≤ 8.6%, r = 0.996, p > 0.05). Compared with conventional formulations, the proposed model demonstrated comparable predictive performance to the Davies model while offering improved robustness under practical clinical conditions and reduced discrepancies compared with the Edmonds model (up to 59.6%, p < 0.01). Sensitivity analysis indicated statistically significant ESD variations associated with ripple factor and anode angle (p < 0.001). Furthermore, the NMME_ESD analytical model provided instantaneous dose estimates. The NMME_ESD model provides a reliable, non-invasive analytical approach for ESD estimation. Explicit inclusion of ripple factor and anode angle in the proposed formulation improves predictive dose estimation accuracy under realistic operating conditions, offering measurable practical benefit for routine clinical dosimetry.</p>","PeriodicalId":46252,"journal":{"name":"Radiological Physics and Technology","volume":" ","pages":"1106-1118"},"PeriodicalIF":1.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148354157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Calibration of diffusion MRI measurements using aqueous glycerin phantoms with controlled viscosity.","authors":"Mayuka Seguchi, Yuki Kanazawa, Tosiaki Miyati, Masafumi Harada, Mitsuharu Miyoshi, Hiroaki Hayashi, Tetsuya Wakayama, Akihiro Haga","doi":"10.1007/s12194-026-01083-5","DOIUrl":"10.1007/s12194-026-01083-5","url":null,"abstract":"<p><p>To characterize the relationship between the apparent diffusion coefficient (ADC) and dynamic viscosity in aqueous glycerin phantoms across different concentrations and temperatures, and to establish a controlled calibration framework for diffusion MRI measurements. Eight glycerin-water solutions (10-60 wt%) were prepared, and viscosities were measured with capillary viscometers at 24, 37, and 40 °C. Diffusion-weighted imaging (DWI) was performed on a 3.0-T scanner using 15 b-values (0-1500 s/mm²). Voxel-wise ADC maps were calculated by mono-exponential fitting, and ADC-viscosity relationships were modeled using linear and inverse fitting approaches. Viscosity increased with concentration and decreased with temperature, consistent with the known physical behavior of glycerin-water mixtures. ADC values were inversely related to viscosity and showed strong relationships at all temperatures (R² > 0.98). High-concentration samples exhibited reduced signal-to-noise ratio and greater fitting instability, limiting reliable analysis in the highest-viscosity range. Aqueous glycerin solutions provide practical phantom materials for evaluating ADC-viscosity relationships under controlled conditions. By anchoring MRI-derived ADC measurements to standard viscometer data, this study established a reproducible calibration framework for diffusion MRI system evaluation across a defined viscosity range.</p>","PeriodicalId":46252,"journal":{"name":"Radiological Physics and Technology","volume":" ","pages":"1068-1076"},"PeriodicalIF":1.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148278944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Clinical edge-case stress testing of two Asia-developed AI auto-contouring systems using prostate radiotherapy planning CT images.","authors":"Yuya Nagake, Keisuke Yasui, Ayami Sugiyama, Yasunori Saito, Hidetoshi Shimizu, Haruka Uezono, Naoki Hayashi","doi":"10.1007/s12194-026-01080-8","DOIUrl":"10.1007/s12194-026-01080-8","url":null,"abstract":"<p><p>To compare the geometric accuracy of two Asia‑developed AI auto‑contouring systems (RatoGuide and OncoStudio) for prostate radiotherapy planning CT, including performance in clinical edge cases. Planning CT data from 45 patients were stratified into four groups (Normal, Spacer, Seed/Spacer, GM/Spacer). Manual contours of prostate, rectum, bladder, seminal vesicles, and femoral heads served as reference. Segmentation accuracy was assessed using DSC and 95% Hausdorff distance; Wilcoxon signed‑rank and Mann-Whitney U tests were applied, with edge‑case analyses treated as exploratory. Median DSC exceeded 0.7 for all structures. RatoGuide performed better for the rectum, whereas OncoStudio performed better for the bladder, seminal vesicles, and femoral heads. Outliers were concentrated in combined implant/spacer groups. Both tools showed generally favorable geometric agreement, with structure‑dependent advantages and edge‑case outliers that warrant workflow‑aware quality assurance and future dosimetric validation.</p>","PeriodicalId":46252,"journal":{"name":"Radiological Physics and Technology","volume":" ","pages":"1380-1386"},"PeriodicalIF":1.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148220164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of meal ingestion on parotid gland T2 values.","authors":"Itsumi Maehata, Yutaka Shigenaga, Yuji Hirayama","doi":"10.1007/s12194-026-01123-0","DOIUrl":"https://doi.org/10.1007/s12194-026-01123-0","url":null,"abstract":"<p><p>Parotid T2 mapping is used for quantitative evaluation, for example to assess early radiation‑induced changes in the parotid gland. However, the effects of pre-scan meals on parotid gland T2 values have not yet been reported. We investigated the temporal changes in parotid T2 values induced by meal ingestion. This prospective, single-center repeated-measures study included sixteen healthy volunteers. 3.0 T axial multi-slice multi-echo TSE T2 mapping was performed with and without fat suppression. Measurements were performed at fasting (baseline) and then alternated between 10 and 30 min after meal ingestion. T2 values at each time point were calculated by averaging the measurements obtained from six ROIs, which were drawn to avoid Stensen's duct and major vessels. Repeated-measures ANOVA with Greenhouse-Geisser correction and Bonferroni adjustment was applied. Without fat suppression, the mean parotid T2 value increased from 63.4 ± 4.63 ms at baseline to 65.8 ± 4.52 ms at 26 min after the start of meal ingestion, with no significant differences from baseline in the pairwise comparisons at any time point. With fat suppression, the mean T2 value increased from 55.7 ± 3.10 ms to 58.6 ± 3.01 ms; significant differences were observed from 16 min onward and persisted through the final time point (p < 0.05). These findings suggest the importance of standardizing pre-scan meal status for quantitative parotid T2 mapping.</p>","PeriodicalId":46252,"journal":{"name":"Radiological Physics and Technology","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148867225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"3D magnetic field modeling and beam optics validation for a static gantry system.","authors":"H Zhao, M Fukuda, A Gerbershagen, H Kanda, K P Nesteruk, J M Schippers","doi":"10.1007/s12194-026-01120-3","DOIUrl":"https://doi.org/10.1007/s12194-026-01120-3","url":null,"abstract":"<p><p>In this work, we developed a 3D computational framework to evaluate the beam transport performance of a static gantry proposed in previous studies. This static gantry enables magnetically driven azimuthal angle selection via tailored fields rather than mechanical rotation, yet its practical feasibility requires rigorous simulation-based evaluation. Our approach utilizes full 3D magnetic field modeling in Opera3D coupled with a custom phase-ellipse tracking program. This integrated workflow captures realistic 3D fringe-field effects and quantitatively evaluates the optical limits driven by momentum spread and boundary edge-focusing. By identifying these primary limitations, this platform provides the requirements and a practical foundation to guide the development and optimization of future static gantry designs.</p>","PeriodicalId":46252,"journal":{"name":"Radiological Physics and Technology","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148867263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development and validation of a DICOM-based prediction model for instantaneous dose rate and delivery time in VMAT.","authors":"Hideharu Miura, Masahiro Hayata, Masahiro Kenjo, Yuji Murakami","doi":"10.1007/s12194-026-01128-9","DOIUrl":"https://doi.org/10.1007/s12194-026-01128-9","url":null,"abstract":"<p><p>This study developed and validated a deterministic, constraint-based model for predicting instantaneous dose rates and total delivery times. A constraint-based Python model extracted treatment plan parameters from DICOM-RT Plan files and simulated the dose rate using three mechanical constraints: multileaf collimator (MLC) velocity, gantry rotation speed, and nominal dose rate, and incorporated geometric beam-off constraints such as avoidance sectors. Validation used high-resolution trajectory logs from a TrueBeam STx across 26 clinical VMAT arcs, including flattened and flattening-filter-free modes. Predicted dose rates agreed well with trajectory logs, with a mean absolute error of 60 MU/min and a root-mean-square error of 140 MU/min for the instantaneous dose rate. Predicted and actual delivery times showed a mean error of - 0.8 ± 0.8 s. This deterministic framework provides an accurate and efficient tool for pre-delivery plan assessment and clinical scheduling, as supported by its high agreement with trajectory log data.</p>","PeriodicalId":46252,"journal":{"name":"Radiological Physics and Technology","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148833261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of breast-level surface dose between single-energy CT and fast kilovoltage-switching dual-energy CT under matched CTDIvol conditions: a chest phantom study.","authors":"Mako Yamada, Takanori Masuda, Norimi Nishiyama, Junichi Nakagawa, Nanami Usui, Hitoshi Takahata, Takashi Amano, Shinichi Arao, Takeshi Nakaura","doi":"10.1007/s12194-026-01129-8","DOIUrl":"https://doi.org/10.1007/s12194-026-01129-8","url":null,"abstract":"<p><p>This phantom study compared breast-level surface dose and image noise between single-energy CT (SECT) and fast kilovoltage-switching dual-energy CT (DECT) under matched volume CT dose index (CTDIvol) conditions. A chest phantom was scanned using a 256-row CT scanner. Surface dose was measured with real-time dosimeters placed on the bilateral anterior chest wall at the breast level and corresponding bilateral posterior positions. Tube currents of 195 mA for SECT and 250 mA for DECT provided matched console-displayed CTDIvol values. Each protocol was repeated 20 times as technical replicates. Image noise was measured in five circular regions of interest at the bilateral anterior and posterior chest walls and heart. Mean surface dose was lower with DECT than SECT at the breast level (15.86 vs. 17.02 mGy; mean difference [DECT minus SECT], -1.16 mGy; 95% confidence interval [CI], -1.71 to -0.61; P < 0.001) and posterior surface (15.77 vs. 17.26 mGy; mean difference, -1.49 mGy; 95% CI, -2.21 to -0.77; P < 0.001). Mean image noise was 7.08 HU with DECT and 6.66 HU with SECT, with no statistically significant difference (mean difference, 0.42 HU; 95% CI, -0.17 to 1.01; P = 0.160). Under the tested conditions, DECT showed lower anterior and posterior surface doses than SECT performed without CT automatic exposure control. No statistically significant difference in image noise was observed, but this does not establish equivalent image quality. These findings should not be generalized to clinically optimized SECT protocols.</p>","PeriodicalId":46252,"journal":{"name":"Radiological Physics and Technology","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148819544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of a CT/MRI-compatible anthropomorphic multimodal deformable male pelvic phantom for end-to-end quality assurance testing in MR-guided online adaptive radiotherapy.","authors":"Masato Nishitani, Hiroyuki Okamoto, Weishan Chang, Junichi Kuwahara, Masataka Ueda, Takahito Chiba, Hiroki Nakayama, Puspen Chakraborty, Koji Inaba, Tairo Kashihara, Satoshi Nakamura, Tetsu Nakaichi, Yasunori Shuto, Tatsuya Sakasai, Tomonori Goka, Hiroshi Igaki","doi":"10.1007/s12194-026-01118-x","DOIUrl":"https://doi.org/10.1007/s12194-026-01118-x","url":null,"abstract":"<p><p>Current quality assurance phantoms often lack MR signal, deformability, or real-time dosimetry capability, limiting comprehensive end-to-end evaluation for MR-guided online adaptive radiotherapy (MRgOART), including verification of deformable image registration (DIR) accuracy and the adaptive workflow within a single phantom. This study aimed to develop a CT/MRI-compatible anthropomorphic, deformable male pelvic phantom for a comprehensive end-to-end test of MRgOART. Reference CT value and MR signal intensity of the prostate, bone, and urine were obtained from a cohort of 30 prostate cancer patients who underwent treatment with a 0.35 T MR-Linac. MR images were acquired using a TRUFI (balanced steady-state free precession) sequence. Candidate materials were optimized to reproduce patient-like CT and MR signal characteristics, and their temporal stability was evaluated over 6 months. Relative electron density (rED) was validated using elemental analysis to ensure dose-calculation reliability. The phantom incorporated deformable prostate, rectum, and bladder models and allowed insertion of an ionization chamber for real-time internal dose measurement. The optimized materials reproduced CT value and MR signal intensity within the mean ± 1 standard deviation of patient reference data, providing clear image contrast without artifacts. CT values remained stable over time, while minor fluctuations in MR signal intensity remained within the range of physiological variability. Composition-based rED values showed small deviations from those derived by CT, which were deemed acceptable for the end-to-end test. The developed phantom enables realistic, multimodal, and deformable end-to-end evaluation of MRgOART, supporting accurate assessment of DIR, adaptive planning, and dose delivery with real-time dosimetry.</p>","PeriodicalId":46252,"journal":{"name":"Radiological Physics and Technology","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148819675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Agreement and reproducibility of quantitative values depend on acquisition parameters in magnetic resonance fingerprinting.","authors":"Kazuhiko Oyu, Yuta Urushibata, Takuma Daimaruya, Yoshito Ichiba, Yasuyuki Takahashi, Shingo Kakeda","doi":"10.1007/s12194-026-01127-w","DOIUrl":"https://doi.org/10.1007/s12194-026-01127-w","url":null,"abstract":"<p><p>This study evaluated the effects of acquisition parameters on relaxation times measured using magnetic resonance fingerprinting (MRF). MRF enables the simultaneous acquisition of multiple quantitative maps by varying the flip angle (FA) and repetition time (TR) in a pseudo-random manner and by pattern-matching signal evolutions to a pre-calculated dictionary. To assess parameter dependency, multiple acquisition protocols were generated with varying numbers of echoes (500, 1000, 1500, and 3000), TR widths (12-14 ms, 12-17 ms, and 12-20 ms), and maximum FA ranges using the MRF Development Kit. The International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology system phantom was scanned ten times per condition on a 3-Tesla scanner. Coefficients of variation (CVs) and agreement were calculated for T1 and T2 values. Results indicated that 1500 and 3000 echoes produced comparable agreement and reproducibility (agreement within ± 7.77% and CVs ≤ 1.13% for both T1 and T2). At 500 echoes, CVs increased substantially and agreement decreased, with T2 values being more affected than T1 values. At 1000 echoes with an expanded TR width (12-20 ms), CVs were 1.15% or less and agreement was within ± 5.20%, comparable to higher echo counts while reducing scan time by approximately 20%. This study demonstrated that the number of echoes, TR width, and maximum FA significantly influence T1 and T2 agreement and reproducibility, suggesting that expanding the TR range can stabilize relaxation times even with fewer echoes.</p>","PeriodicalId":46252,"journal":{"name":"Radiological Physics and Technology","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148814181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"End-to-end technical validation of multi-isocenter total body irradiation using an anthropomorphic phantom.","authors":"Dipesh, Raj Pal Singh, Manindra Bhushan","doi":"10.1007/s12194-026-01125-y","DOIUrl":"https://doi.org/10.1007/s12194-026-01125-y","url":null,"abstract":"<p><p>The objective of this study is to perform an end-to-end (E2E) technical validation of a total body irradiation (TBI) workflow using an anthropomorphic phantom, integrating simulation, treatment planning, patient-specific quality assurance, and phantom-based dosimetry to ensure accurate and reproducible dose delivery. A full E2E test was performed using the Rando Phantom and Varian Eclipse TPS. CT scans were acquired in head-first supine (HFS) and feet-first supine (FFS) orientations and registered to simulate full-body imaging. Treatment plans were optimized for both orientations, with specific gradient dose regions defined for overlap zones. ArcCHECK and OSLDs were used for pre-treatment and phantom-embedded dosimetric verification, respectively. Cone Beam CT (CBCT) assessed positional accuracy across eight treatment fractions. Dose discrepancies and alignment errors were evaluated across anatomical regions. HU comparison between the CT console and TPS revealed only minor deviations, all within ± 6 HU, supporting the consistency of HU representation in the TPS. Gamma passing rates exceeded 97% across most regions. OSLD dose differences remained within ± 2.5% for most sites, except thorax and overlap zones, which reached ± 4.8%. CBCT-based setup verification demonstrated sub-millimeter alignment deviations across fractions, indicating consistent positional accuracy. E2E validation using the Rando Phantom supports technical accuracy and consistency in the TBI workflow. Notable dose variations in overlap and heterogeneous regions highlight the need for enhanced QA in complex geometries. The findings support the technical feasibility and reproducibility of the workflow, while further patient-specific and motion-inclusive studies are required to establish broader clinical applicability.</p>","PeriodicalId":46252,"journal":{"name":"Radiological Physics and Technology","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148814341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}