Physics and Imaging in Radiation Oncology最新文献

{"title":"A proof-of-concept study of direct magnetic resonance imaging-based proton dose calculation for brain tumors via neural networks with Monte Carlo-comparable accuracy","authors":"Muheng Li ,&nbsp;Carla Winterhalter ,&nbsp;Xia Li ,&nbsp;Sairos Safai ,&nbsp;Antony Lomax ,&nbsp;Ye Zhang","doi":"10.1016/j.phro.2025.100806","DOIUrl":"10.1016/j.phro.2025.100806","url":null,"abstract":"<div><h3>Background and purpose</h3><div>Proton therapy currently relies on computed tomography (CT) imaging despite magnetic resonance imaging’s (MRI) superior soft-tissue contrast. While synthetic CTs can be generated from magnetic resonance (MR) images, this introduces additional complexity. We present a deep learning-based dose engine enabling direct proton dose calculation from MR images to streamline workflows while maintaining Monte Carlo (MC)-level accuracy.</div></div><div><h3>Materials and methods</h3><div>Using paired MR-CT scans from 39 brain tumor patients (29/3/7 for training/validation/testing), we developed a deep learning framework using various sequence models for individual proton pencil beam dose prediction. The framework processes beam-eye-view patches from 2000 random beam configurations per patient, varying in angles and energy, with corresponding MC dose distributions pre-calculated on CT. Models using CT images were trained for comparison.</div></div><div><h3>Results</h3><div>The xLSTM architecture performed best for both MR and CT-based scenarios among the evaluated sequence models. For full treatment plans, our model achieved gamma pass rates with median 99.8 % (range: 98.6 %–99.9 %, 1 mm/1%), and median percentage dose errors of 0.2 % (range: 0.1 %–0.4 %) within patient bodies and 1.3 % (range: 0.8 %–3.7 %) in high-dose regions (&gt;90 % prescription dose). The model required only 3 ms per beam prediction compared to 2 s for MC simulation.</div></div><div><h3>Conclusion</h3><div>This study demonstrated the feasibility of MC-quality proton dose calculations directly from MR images for brain tumor patients, achieving comparable accuracy with faster computation and simplified implementation.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"35 ","pages":"Article 100806"},"PeriodicalIF":3.4,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144596154","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":"First in vitro and in vivo experiments with ultra high-dose rate oxygen ion radiotherapy","authors":"Celine Karle ,&nbsp;Domenico I. Filosa ,&nbsp;Mahdi Akbarpour ,&nbsp;Nora Schuhmacher ,&nbsp;Stephan Brons ,&nbsp;Rainer Cee ,&nbsp;Christian Schömers ,&nbsp;Stefan Scheloske ,&nbsp;Kristoffer Petersson ,&nbsp;Thomas Haberer ,&nbsp;Amir Abdollahi ,&nbsp;Jürgen Debus ,&nbsp;Thomas Tessonnier ,&nbsp;Mahmoud Moustafa ,&nbsp;Andrea Mairani ,&nbsp;Ivana Dokic","doi":"10.1016/j.phro.2025.100803","DOIUrl":"10.1016/j.phro.2025.100803","url":null,"abstract":"<div><div>Within this study, we demonstrated the feasibility of ultra-high dose rate (UHDR) oxygen ion irradiation at three different levels of biological complexity. The difference in oxygen consumption between UHDR and standard dose rates (SDR) was negligible in a protein-enriched saline solution. For the studied conditions of dose, dose rate and linear energy transfer (LET), UHDR irradiation showed comparable efficacy to SDR in pancreatic cancer cell killing in vitro, along with inducing a similar tumor growth delay in vivo. These findings emphasize the potential of high-LET UHDR irradiation and support further investigation of oxygen ions at UHDR.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"35 ","pages":"Article 100803"},"PeriodicalIF":3.4,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144604696","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":"Feasibility of Monte Carlo-based patient-specific quality assurance in 1.5 Tesla magnetic resonance-guided online adaptive radiotherapy: a multi-institutional study","authors":"Ruiqi Li ,&nbsp;Yao Zhao ,&nbsp;Jingying Lin ,&nbsp;Tsuicheng Chiu ,&nbsp;Weiguo Lu ,&nbsp;Jinzhong Yang ,&nbsp;Mu-Han Lin","doi":"10.1016/j.phro.2025.100800","DOIUrl":"10.1016/j.phro.2025.100800","url":null,"abstract":"<div><h3>Introduction</h3><div>To evaluate the feasibility of Monte Carlo (MC)-based patient-specific quality assurance (PSQA) for MR-guided online adaptive radiotherapy and to explore the potential to eliminate the post-delivery measurement-based PSQA.</div></div><div><h3>Material and methods</h3><div>A total of 113 cases from two institutions, treated on MR-Linac machines, were included in the study. A customized GPU-accelerated, Monte Carlo-based secondary dose verification software (ART2Dose) was developed and integrated into the QA workflow, accounting for a 1.5 Tesla magnetic field. PSQA included ArcCheck (AC) delivery QA and online MC calculation-based QA. Reference plans underwent offline validation with AC and MC, while adapt-to-shape (ATS) plans were processed through MC and post-delivery QA. Gamma pass rates (GPR) with 3 %/2mm criteria were compared statistically across methods. Radcalc was applied to compare point dose difference with MC.</div></div><div><h3>Results</h3><div>MC QA achieved GPRs of 97.5 % ± 2.0 % and 97.1 % ± 2.9 % for reference and ATS plans, comparable to AC QA (97.6 % ± 2.0 % and 96.9 % ± 3.0 %). Wilcoxon signed-rank test showed statistically significant differences between reference and ATS plan QA (p &lt; 0.05), but a Pearson correlation coefficient of 0.76 confirmed a linear relationship for MC GPR. Lung cases exhibited lower GPRs with MC compared to AC QA. MC QA demonstrated supaireerior point dose agreement with TPS (1.7 % ± 1.2 %) compared to RadCalc (4.1 % ± 1.7 %). No significant differences were observed between institutions.</div></div><div><h3>Conclusion</h3><div>MC-based QA is a robust tool for adaptive QA workflows in 1.5-T MR-Linac systems. It enhances efficiency and potentially supports the elimination of post-delivery measurement-based QA for adaptive plans.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"35 ","pages":"Article 100800"},"PeriodicalIF":3.4,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144557536","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":"Dose-response mapping of bladder and rectum in prostate cancer patients undergoing radiotherapy with and without baseline toxicity correction","authors":"Tanuj Puri ,&nbsp;Tiziana Rancati ,&nbsp;Petra Seibold ,&nbsp;Adam Webb ,&nbsp;Eliana Vasquez Osorio ,&nbsp;Andrew Green ,&nbsp;Eliana Gioscio ,&nbsp;David Azria ,&nbsp;Marie-Pierre Farcy-Jacquet ,&nbsp;Jenny Chang-Claude ,&nbsp;Alison Dunning ,&nbsp;Maarten Lambrecht ,&nbsp;Barbara Avuzzi ,&nbsp;Dirk de Ruysscher ,&nbsp;Elena Sperk ,&nbsp;Ana Vega ,&nbsp;Liv Veldeman ,&nbsp;Barry Rosenstein ,&nbsp;Jane Shortall ,&nbsp;Sarah Kerns ,&nbsp;Marcel van Herk","doi":"10.1016/j.phro.2025.100805","DOIUrl":"10.1016/j.phro.2025.100805","url":null,"abstract":"<div><h3>Background and purpose</h3><div>Radiotherapy dose–response maps (DRM) combine dose-surface maps (DSM) and toxicity outcomes to identify high-risk subregions in organ-at-risk. This study assesses the impact of baseline toxicity correction on the identification of high-risk subregions in dose–response modeling for prostate cancer patients undergoing radiotherapy.</div></div><div><h3>Materials and methods</h3><div>The analysis included 1808 datasets, with 589 exclusions before toxicity-specific data removal. Bladder/rectum were automatically segmented on planning computed tomography scans, DSMs unwrapped into 91x90 voxel grids, and converted to equivalent doses in 2 Gy fractions (EQD2; α/β = 1 Gy). Seventeen late toxicities were assessed with two methods: (i) baseline toxicity subtracted from the maximum of 12- and 24-months toxicity scores, dichotomized at grade 1, and (ii) maximum of 12- and 24-months toxicity scores dichotomized at grade 1. DSMs were split accordingly, and voxel-wise t-values computed using Welch’s t-equation. Statistically significant voxels were identified via the 95th percentile of maximum of t-value (Tmax) distribution.</div></div><div><h3>Results</h3><div>Event counts with baseline correction were 82/82/286/226 for urinary tract obstruction/retention/urgency/incontinence, respectively; without baseline correction, they were 93/104/465/361. For bladder DSMs, urinary incontinence, obstruction, retention, and urgency had 1143/186, 1768/1848, 516/0, and 33/0 significant voxels without/with baseline correction. For rectum DSMs, urinary incontinence and tract obstruction had 604/0 and 1980/889 significant voxels without/with baseline correction. However, no significant associations between rectal DSMs and rectum-related toxicities were found.</div></div><div><h3>Conclusions</h3><div>DRM without baseline correction appears more sensitive to high-risk subregions due to higher event counts. Non-linear toxicity grading and multivariable analysis may enhance DRM reliability.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"35 ","pages":"Article 100805"},"PeriodicalIF":3.4,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144570063","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":"In-vitro effects of modern radiotherapy regimes on cardiac implanted electrical devices","authors":"Steven Manley ,&nbsp;Amy Fenwick ,&nbsp;Megan Fraser ,&nbsp;Mark Lowrey ,&nbsp;Anna Walaszczyk ,&nbsp;Nick West","doi":"10.1016/j.phro.2025.100804","DOIUrl":"10.1016/j.phro.2025.100804","url":null,"abstract":"<div><h3>Background and purpose</h3><div>External Beam Radiotherapy (EBRT) of patients with Cardiac Implanted Electrical Devices (CIEDs) have guidelines developed over many decades, during which both technologies have advanced. Consequently, guidelines may not reflect modern device interactions. Asynchronous modes, with pace sensing and shocks turned off whilst regulating pacing output, is used routinely for MRI scanning and could reduce risks for pace sensing errors in radiotherapy. Evidence is limited on modern radiotherapy using high dose, high doserate beams, with CIEDs in asynchronous mode. We present the effects of irradiating modern CIEDs using contemporary radiotherapy regimes.</div></div><div><h3>Materials and methods</h3><div>One hundred and sixty explanted CIEDs were irradiated, to corroborate historical findings for modern devices in normal operational modes, and explore effects when in asynchronous mode. Regimes knowingly detrimental to CIEDs; 48 Gy single fraction, neutron producing, alongside clinically relevant regimes of 60 Gy in 5 fractions using 10 MV flattening filter free [FFF] beams at clinical, and maximal dose rates.</div></div><div><h3>Results</h3><div>No significant changes occurred to pacing voltages from 60 Gy in 5 fractions 10 MV FFF deliveries in asynchronous mode.</div><div>No evidence supported restricting 6 MV flattened beams for CIED patients, including defibrillation capable devices.</div></div><div><h3>Conclusions</h3><div>This study demonstrates asynchronous mode can reduce the frequency of CIED malfunctions during EBRT. However, clinical context, risks and benefit must be evaluated per patient. While some current guidelines potentially compromise plan quality to reduce dose to the CIED, the use of asynchronous mode may provide planning options, which more closely align to non-CIED cases.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"35 ","pages":"Article 100804"},"PeriodicalIF":3.4,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144534824","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":"Temporal drift in calibration of Ir-192 brachytherapy sources: A multi-center study on dosimetric discrepancies and metrological consistency","authors":"Javier Vijande ,&nbsp;Jacob G. Johansen ,&nbsp;Marisol De Brabandere ,&nbsp;Taran Paulsen Hellebust ,&nbsp;Antonio Herreros ,&nbsp;Christian Kirisits ,&nbsp;Ruud van Leeuwen ,&nbsp;Panagiotis Papagiannis ,&nbsp;Mark J. Rivard ,&nbsp;Frank-André Siebert ,&nbsp;Frank Verhaegen ,&nbsp;Jan Wiersma ,&nbsp;Åsa Carlsson Tedgren","doi":"10.1016/j.phro.2025.100801","DOIUrl":"10.1016/j.phro.2025.100801","url":null,"abstract":"<div><h3>Background and purpose</h3><div>High-dose-rate (HDR) brachytherapy relies on accurate and metrologically traceable source strength determination. Recent anecdotal reports and preliminary studies have suggested a possible temporal drift in the reference air kerma rate (<em>RAKR</em>) measured by clinical users compared to manufacturer certificates for ¹⁹²Ir sources. This study investigates the existence and magnitude of such drift across a large, multicenter European dataset and explores potential underlying causes.</div></div><div><h3>Materials and methods</h3><div>A total of over 1700 <em>RAKR</em> measurements for HDR and PDR brachytherapy sources, collected over two decades from 29 centers in 10 European countries, were analyzed. The ratio of hospital-measured <em>RAKR</em> to manufacturer-certified <em>RAKR</em> was assessed using linear regression and t-tests to evaluate drift. Data were corrected for center-dependent systematics and segmented around key dates corresponding to changes in primary standards. Supplementary analyses included leave-one-out testing and time-segmented trend assessment.</div></div><div><h3>Results</h3><div>A statistically significant drift (+0.15 %/year) was detected for all ¹⁹²Ir source types after 2018, correlating temporally with updates in the German Physikalisch-Technische Bundesanstalt (PTB) primary standards laboratory. Removing PTB corrections from manufacturer values nearly eliminated the observed drift. No such trend was observed for ⁶⁰Co sources.</div></div><div><h3>Conclusion</h3><div>The findings reveal a drift in hospital-to-manufacturer Ir-192 <em>RAKR</em> ratios that is temporally correlated with changes in metrology standards, not uniformly implemented across calibration chains. The true cause is however still unknown. The study aimed to investigate that greater transparency and harmonization among all stakeholders are essential to ensure dosimetric accuracy in HDR brachytherapy.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"35 ","pages":"Article 100801"},"PeriodicalIF":3.4,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144534823","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":"Three-dimensional dose uncertainty maps based on the fraction of field edge dose for volumetric modulated arc therapy plans","authors":"Emmanouil Terzidis ,&nbsp;Fredrik Nordström ,&nbsp;Magnus Gustafsson ,&nbsp;Anna Karlsson ,&nbsp;Julia Götstedt ,&nbsp;Anna Bäck","doi":"10.1016/j.phro.2025.100802","DOIUrl":"10.1016/j.phro.2025.100802","url":null,"abstract":"<div><h3>Background and purpose</h3><div>Absorbed dose uncertainties in radiotherapy plans are generally larger near field edges compared to the center of the field. The aim of this study was to investigate dose uncertainties related to the field edge in 3D for plans of varying complexities.</div></div><div><h3>Materials and methods</h3><div>A method was developed for calculation of the fraction of field edge dose (FED), that could be visualized as a 3D uncertainty map (3DUM_FED). Twelve clinical treatment plans were included for four different treatment sites that were reoptimized to create one plan with reduced complexity and one of increased complexity. 3DUM_FED was calculated for all 36 plans. The highest FED for a 2 cm³ volume (FED_{2 cm}³) and average FED (FED_mean) were calculated for the planning target volumes (PTV) and organs at risk (OAR) and compared with the edge area metric (EAM).</div></div><div><h3>Results</h3><div>High FED (above 20 %) were mainly found just outside the PTV border. FED_mean in PTV was highest for the plans of increased complexity. The FED_mean for PTVs and OARs, as well as the FED_{2 cm}³ for PTVs, correlated with ρ ≥ 0.81 to EAM. The FED_{2 cm}³ for OARs had a weaker correlation with EAM (ρ = 0.55). 3DUM_FED analysis revealed that plan complexity affects different parts of the patient volume in different ways.</div></div><div><h3>Conclusions</h3><div>3DUM_FED offers a way to estimate dose uncertainties related to the field edge in 3D. It also allows for separate evaluation in different regions of interest, unlike EAM, which mainly correlates with the dose uncertainty related to the PTV.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"35 ","pages":"Article 100802"},"PeriodicalIF":3.4,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144517364","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 proton and photon therapy in stereotactic arrhythmia radioablation for ventricular tachycardia","authors":"Keyur D. Shah ,&nbsp;Chih-Wei Chang ,&nbsp;Pretesh Patel ,&nbsp;Sibo Tian ,&nbsp;Yuan Shao ,&nbsp;Kristin A Higgins ,&nbsp;Yinan Wang ,&nbsp;Justin Roper ,&nbsp;Jun Zhou ,&nbsp;Zhen Tian ,&nbsp;Xiaofeng Yang","doi":"10.1016/j.phro.2025.100807","DOIUrl":"10.1016/j.phro.2025.100807","url":null,"abstract":"<div><h3>Background and Purpose</h3><div>Ventricular tachycardia (VT) is a life-threatening arrhythmia commonly treated with catheter ablation; however, some cases remain refractory. Stereotactic arrhythmia radioablation (STAR) offers a non-invasive alternative. While photon-based STAR is effective, proton therapy may improve dose conformity and spare critical organs at risk (OARs), including the heart itself. The aim of this study was to compare the dose-volume metrics between proton and photon therapy for VT.</div></div><div><h3>Materials and Methods</h3><div>We retrospectively analyzed 34 VT patients who received photon STAR. Proton STAR plans were generated using robust optimization in a commercial treatment planning system to deliver the same prescription dose of 25 Gy in a single fraction. Dose-volume metrics, including <em>D₉₉</em>, <em>D₉₅</em>, <em>D_mean</em>, and <span><math><mrow><msub><mi>D</mi><msup><mrow><mn>0.03</mn><mi>c</mi><mi>m</mi></mrow><mn>3</mn></msup></msub></mrow></math></span>, were extracted for critical OARs (heart, lungs, cardiac-chambers) and target. Shapiro-Wilk tests were used to assess normality, with paired t-tests or Wilcoxon signed-rank tests for statistical comparisons between modalities, with Bonferroni correction applied for multiple comparisons.</div></div><div><h3>Results</h3><div>Proton and photon plans achieved comparable target coverage, with CTV <em>D₉₅</em> of 25.8 [21.6–28.7] Gy(RBE) vs. 27.2 [21.6–29.3] Gy (p &lt; 0.001). Proton therapy significantly reduced OAR doses, including heart <em>D_mean</em> (3.6 ± 1.5 Gy(RBE) vs. 5.5 ± 2.0 Gy, p &lt; 0.001) and lungs <em>D_mean</em> (0.6 [0.0–1.9] Gy(RBE) vs. 1.2 [0.2–2.6] Gy, p &lt; 0.001), while maintaining optimal target coverage.</div></div><div><h3>Conclusion</h3><div>Proton therapy for STAR demonstrated significant potential for OARs sparing compared to photon therapy for VT, while maintaining equivalent target coverage. These findings highlight the potential of proton therapy to improve outcomes for VT patients.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"35 ","pages":"Article 100807"},"PeriodicalIF":3.4,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144588456","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":"Topogram and 3DCT geometry calibration for image-guided proton therapy with in-room CT-on-rails","authors":"Giovanni Fattori ,&nbsp;Riccardo Via ,&nbsp;Antony J. Lomax ,&nbsp;Sairos Safai","doi":"10.1016/j.phro.2025.100799","DOIUrl":"10.1016/j.phro.2025.100799","url":null,"abstract":"<div><div>In-room computer tomography (CT) on-rails scanners are available in proton therapy centers but often limited to control imaging, due to geometric distortion and lack of integration. We present a calibration method combining CT-on-rails with a robotic table to achieve sub-millimeter patient positioning accuracy. Geometric distortions in 3DCT and topogram images were corrected using affine models and validated with laser tracker data. Phantom experiments simulating clinical conditions showed errors below 0.15 mm for 3D/3D and 0.3–0.55 mm for 2D/3D registration, the latter using a novel algorithm for digitally reconstructed topograms. The workflow enables accurate positioning without isocenter verification, supporting high-precision radiotherapy.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"35 ","pages":"Article 100799"},"PeriodicalIF":3.4,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144502089","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":"Cone-beam CT-based estimations of prostate motion and dose distortion during radiotherapy","authors":"Karolina A Klucznik ,&nbsp;Thomas Ravkilde ,&nbsp;Simon Skouboe ,&nbsp;Ditte S Møller ,&nbsp;Steffen Hokland ,&nbsp;Paul Keall ,&nbsp;Simon Buus ,&nbsp;Lise Bentzen ,&nbsp;Per R Poulsen","doi":"10.1016/j.phro.2025.100798","DOIUrl":"10.1016/j.phro.2025.100798","url":null,"abstract":"<div><h3>Background and purpose</h3><div>Intra-fractional prostate translational and rotational (6DoF) motion can cause dose distortions. As intra-fractional motion monitoring is often unavailable, this study compares three methods to use pre- and post-treatment cone beam CTs (CBCT) to estimate prostate positioning errors during treatment and their dosimetric impact.</div></div><div><h3>Material and Methods</h3><div>Eighteen patients received prostate radiotherapy with pre-treatment CBCT setup. For 7–10 fractions per patient (total:174), triggered kV-images were acquired every 3 s during beam-on and a CBCT was acquired post-treatment. The 6DoF prostate position error during treatment was determined from the kV-images (ground truth) and estimated from the CBCTs assuming a static position as in the pre-CBCT(Scenario1), a linear drift between pre- and post-CBCT position(Scenario2) or a static position as in the post-CBCT(Scenario3). The positioning errors and prostate dose from each scenario were compared with the ground truth.</div></div><div><h3>Results</h3><div>Scenario1 was inferior to the others with prostate position root-mean-square errors of 1.1 mm(LR), 1.7 mm(AP) and 1.8 mm(CC). Scenario2 and 3 were similarly accurate with root-mean-square errors of 0.5 mm(LR), 0.9 mm(AP) and 0.8 mm(CC) (Scenario2) and 0.6 mm(LR), 1.1 mm(AP) and 0.9 mm(CC) (Scenario3). The prostate position errors reduced the CTV D_99.5% by more than 2/3 % at 24/15 % of the fractions, respectively. The sensitivity in detecting these dose deficits was low for Scenario1 (9–16 %) and considerably higher for Scenario2 (68–76 %) and Scenario3 (86–91 %). All scenarios showed high specificity (93–99 %).</div></div><div><h3>Conclusion</h3><div>Using the post-CBCT prostate position, acquired right after treatment, performed best in detecting intra-fractional prostate position errors and CTV dose deficits. It offers a scalable and conservative estimate of motion-induced dose distortions.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"35 ","pages":"Article 100798"},"PeriodicalIF":3.4,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144502088","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}