Pub Date : 2025-01-01DOI: 10.1016/j.phro.2025.100722
Sebastian Klüter , Karolin Milewski , Wibke Johnen , Stephan Brons , Jakob Naumann , Stefan Dorsch , Cedric Beyer , Katharina Paul , Kilian A. Dietrich , Tanja Platt , Jürgen Debus , Julia Bauer
This work presents an experimental dosimetric evaluation of raster-scanning particle beam delivery during simultaneous in-beam magnetic resonance (MR) imaging. Using an open MR scanner at an experimental treatment room, radiochromic film comparisons for protons, helium and carbon ions, each with and without simultaneous in-beam cine MR imaging, yielded 2D gamma pass rates ≥ 98.8 % for a 3 % / 1.5 mm criterion, and ≥ 99.9 % for 5 % / 1.5 mm. These results constitute a first experimental confirmation that time varying magnetic fields of MR gradients do not result in clinically relevant additional dose perturbations.
{"title":"First dosimetric evaluation of clinical raster-scanned proton, helium and carbon ion treatment plan delivery during simultaneous real-time magnetic resonance imaging","authors":"Sebastian Klüter , Karolin Milewski , Wibke Johnen , Stephan Brons , Jakob Naumann , Stefan Dorsch , Cedric Beyer , Katharina Paul , Kilian A. Dietrich , Tanja Platt , Jürgen Debus , Julia Bauer","doi":"10.1016/j.phro.2025.100722","DOIUrl":"10.1016/j.phro.2025.100722","url":null,"abstract":"<div><div>This work presents an experimental dosimetric evaluation of raster-scanning particle beam delivery during simultaneous in-beam magnetic resonance (MR) imaging. Using an open MR scanner at an experimental treatment room, radiochromic film comparisons for protons, helium and carbon ions, each with and without simultaneous in-beam cine MR imaging, yielded 2D gamma pass rates ≥ 98.8 % for a 3 % / 1.5 mm criterion, and ≥ 99.9 % for 5 % / 1.5 mm. These results constitute a first experimental confirmation that time varying magnetic fields of MR gradients do not result in clinically relevant additional dose perturbations.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"33 ","pages":"Article 100722"},"PeriodicalIF":3.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143387666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cancer affects 1 in 1000–2000 pregnancies annually worldwide, creating challenges in balancing cancer treatment and fetal safety. This study compares out-of-field radiation doses between two treatment modalities: 6MV external photon radiotherapy (XRT) and pencil beam scanning proton-therapy (PBS-PRT) for breast cancer, including imaging, to evaluate PBS-PRT as a potential new treatment option.
Materials and methods
For breast cancer involving lymph node levels 1–4 and the intramammary lymph nodes, treatment plans were created for XRT (with Flattening Filter (FF) and FF-Free (FFF)) and PBS-PRT, prescribing 15 × 2.67 Gy(RBE). Measurements were conducted using an adapted anthropomorphic phantom representing 20- and 30-week pregnancy. Bubble detectors placed in the phantom’s abdomen assessed neutron dose from PBS-PRT, while a Farmer ion chamber was used for imaging and XRT dose.
Results
At 20 weeks, PBS-PRT including imaging delivered 22.4 mSv, reducing dose 3.4-fold versus 6FF XRT and 2.5-fold versus 6FFF XRT. At 30 weeks, the PBS-PRT dose was 25.4 mSv, resulting in 7.6-fold and 6.3-fold reductions compared to 6FF and 6FFF XRT, respectively.
Conclusions
This study presents the first one-by-one comparison between PBS-PRT and different XRT modalities for pregnant breast cancer patients with an adapted anthropomorphic phantom. PBS-PRT measurements showed that the total equivalent dose was below the 100 mSv threshold outlined in AAPM Task Group Report No. 36 for a 30-week pregnancy, even under a worst-case scenario, maintaining treatment goals. These findings support the adoption of PBS-PRT as the preferred approach for treating pregnant breast cancer patients, should radiotherapy be required.
{"title":"Out-of-field dose assessment for pencil beam scanning proton radiotherapy versus photon radiotherapy for breast cancer in pregnant women","authors":"Menke Weessies, Murillo Bellezzo, Britt J.P. Hupkens, Frank Verhaegen, Gloria Vilches-Freixas","doi":"10.1016/j.phro.2025.100721","DOIUrl":"10.1016/j.phro.2025.100721","url":null,"abstract":"<div><h3>Background and purpose</h3><div>Cancer affects 1 in 1000–2000 pregnancies annually worldwide, creating challenges in balancing cancer treatment and fetal safety. This study compares out-of-field radiation doses between two treatment modalities: 6MV external photon radiotherapy (XRT) and pencil beam scanning proton-therapy (PBS-PRT) for breast cancer, including imaging, to evaluate PBS-PRT as a potential new treatment option.</div></div><div><h3>Materials and methods</h3><div>For breast cancer involving lymph node levels 1–4 and the intramammary lymph nodes, treatment plans were created for XRT (with Flattening Filter (FF) and FF-Free (FFF)) and PBS-PRT, prescribing 15 × 2.67 Gy(RBE). Measurements were conducted using an adapted anthropomorphic phantom representing 20- and 30-week pregnancy. Bubble detectors placed in the phantom’s abdomen assessed neutron dose from PBS-PRT, while a Farmer ion chamber was used for imaging and XRT dose.</div></div><div><h3>Results</h3><div>At 20 weeks, PBS-PRT including imaging delivered 22.4 mSv, reducing dose 3.4-fold versus 6FF XRT and 2.5-fold versus 6FFF XRT. At 30 weeks, the PBS-PRT dose was 25.4 mSv, resulting in 7.6-fold and 6.3-fold reductions compared to 6FF and 6FFF XRT, respectively.</div></div><div><h3>Conclusions</h3><div>This study presents the first one-by-one comparison between PBS-PRT and different XRT modalities for pregnant breast cancer patients with an adapted anthropomorphic phantom. PBS-PRT measurements showed that the total equivalent dose was below the 100 mSv threshold outlined in AAPM Task Group Report No. 36 for a 30-week pregnancy, even under a worst-case scenario, maintaining treatment goals. These findings support the adoption of PBS-PRT as the preferred approach for treating pregnant breast cancer patients, should radiotherapy be required.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"33 ","pages":"Article 100721"},"PeriodicalIF":3.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.phro.2025.100715
Fatemeh Nosrat , Cem Dede , Lucas B. McCullum , Raul Garcia , Abdallah S.R. Mohamed , Jacob G. Scott , James E. Bates , Brigid A. McDonald , Kareem A. Wahid , Mohamed A. Naser , Renjie He , Aysenur Karagoz , Amy C. Moreno , Lisanne V. van Dijk , Kristy K. Brock , Jolien Heukelom , Seyedmohammadhossein Hosseinian , Mehdi Hemmati , Andrew J. Schaefer , Clifton D. Fuller
Background and purpose
Prior work on adaptive organ-at-risk (OAR)-sparing radiation therapy has typically reported outcomes based on fixed-number or fixed-interval re-planning, which represent one-size-fits-all approaches and do not account for the variable progression of individual patients’ toxicities. The purpose of this study was to determine the personalized optimal timing of re-planning in adaptive OAR-sparing radiation therapy, considering limited re-planning resources, for patients with head and neck cancer (HNC).
Materials and methods
A novel Markov decision process (MDP) model was developed to determine optimal timing of re-planning based on the patient’s expected toxicity, characterized by normal tissue complication probability (NTCP), for four toxicities. The MDP parameters were derived from a dataset comprising 52 HNC patients treated between 2007 and 2013. Kernel density estimation was used to smooth the sample distributions. Optimal re-planning strategies were obtained when the permissible number of re-plans throughout the treatment was limited to 1, 2, and 3, respectively.
Results
The MDP (optimal) solution recommended re-planning when the difference between planned and actual NTCPs (ΔNTCP) was greater than or equal to 1%, 2%, 2%, and 4% at treatment fractions 10, 15, 20, and 25, respectively, exhibiting a temporally increasing pattern. The ΔNTCP thresholds remained constant across the number of re-planning allowances (1, 2, and 3).
Conclusion
In limited-resource settings that impeded high-frequency adaptations, ΔNTCP thresholds obtained from an MDP model could derive optimal timing of re-planning to minimize the likelihood of treatment toxicities.
{"title":"Optimal timing of organs-at-risk-sparing adaptive radiation therapy for head-and-neck cancer under re-planning resource constraints","authors":"Fatemeh Nosrat , Cem Dede , Lucas B. McCullum , Raul Garcia , Abdallah S.R. Mohamed , Jacob G. Scott , James E. Bates , Brigid A. McDonald , Kareem A. Wahid , Mohamed A. Naser , Renjie He , Aysenur Karagoz , Amy C. Moreno , Lisanne V. van Dijk , Kristy K. Brock , Jolien Heukelom , Seyedmohammadhossein Hosseinian , Mehdi Hemmati , Andrew J. Schaefer , Clifton D. Fuller","doi":"10.1016/j.phro.2025.100715","DOIUrl":"10.1016/j.phro.2025.100715","url":null,"abstract":"<div><h3>Background and purpose</h3><div>Prior work on adaptive organ-at-risk (OAR)-sparing radiation therapy has typically reported outcomes based on fixed-number or fixed-interval re-planning, which represent one-size-fits-all approaches and do not account for the variable progression of individual patients’ toxicities. The purpose of this study was to determine the personalized optimal timing of re-planning in adaptive OAR-sparing radiation therapy, considering limited re-planning resources, for patients with head and neck cancer (HNC).</div></div><div><h3>Materials and methods</h3><div>A novel Markov decision process (MDP) model was developed to determine optimal timing of re-planning based on the patient’s expected toxicity, characterized by normal tissue complication probability (NTCP), for four toxicities. The MDP parameters were derived from a dataset comprising 52 HNC patients treated between 2007 and 2013. Kernel density estimation was used to smooth the sample distributions. Optimal re-planning strategies were obtained when the permissible number of re-plans throughout the treatment was limited to 1, 2, and 3, respectively.</div></div><div><h3>Results</h3><div>The MDP (optimal) solution recommended re-planning when the difference between planned and actual NTCPs (ΔNTCP) was greater than or equal to 1%, 2%, 2%, and 4% at treatment fractions 10, 15, 20, and 25, respectively, exhibiting a temporally increasing pattern. The ΔNTCP thresholds remained constant across the number of re-planning allowances (1, 2, and 3).</div></div><div><h3>Conclusion</h3><div>In limited-resource settings that impeded high-frequency adaptations, ΔNTCP thresholds obtained from an MDP model could derive optimal timing of re-planning to minimize the likelihood of treatment toxicities.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"33 ","pages":"Article 100715"},"PeriodicalIF":3.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.phro.2025.100703
Paolo Caricato , Francesca Cavagnetto , Silvia Meroni , Salvina Barra , Laura Brambilla , Enrica Bovo , Samuele Cavinato , Alessio Cirone , Flavio Giannelli , Marta Paiusco , Emilia Pecori , Emanuele Pignoli , Margherita Pollara , Giovanni Scarzello , Alessandro Scaggion
Background and purpose
Knowledge-Based Planning (KBP) is increasingly used to standardize and optimize radiotherapy planning. This study aims to develop, refine, and compare multicentric KBP models for craniospinal irradiation (CSI) in pediatric patients.
Materials and methods
A total of 113 CSI treatments from three Italian centers were collected, comprising Computed Tomography scans, target and organ contours, and treatment plans. Treatment techniques included Helical Tomotherapy (HT) and Volumetric Modulated Arc Therapy (VMAT). Three KBP models were developed: a full model (F-model) using data from 87 patients, a reduced model (R-model) based on a subset of the same sample, and a replanned model (RP-model) using KBP re-optimized plans. Models’ quality was evaluated using goodness-of-fit and goodness-of-prediction metrics, and their performance was assessed on a validation set of 26 patients through dose-volume histogram (DVH) comparisons, prediction bias, and variance analysis.
Results
The F-model and R-model exhibited similar quality and predictive ability, reflecting the variability of the original dataset and resulting in broad prediction intervals in low to mid-dose ranges. The RP-model achieved the highest quality, with narrower prediction bands. The RP-model is preferable for standardizing planning across centers, while the F-model is better suited for quality assurance as it captures clinical variability.
Conclusions
KBP models can effectively predict DVHs despite extreme geometric variability. However, models trained on highly variable datasets cannot simultaneously achieve high precision and accuracy. Comparing KBP models is essential for establishing benchmarks to meet specific clinical goals, particularly for complex pediatric CSI treatments.
{"title":"Critical assessment of knowledge-based models for craniospinal irradiation of paediatric patients","authors":"Paolo Caricato , Francesca Cavagnetto , Silvia Meroni , Salvina Barra , Laura Brambilla , Enrica Bovo , Samuele Cavinato , Alessio Cirone , Flavio Giannelli , Marta Paiusco , Emilia Pecori , Emanuele Pignoli , Margherita Pollara , Giovanni Scarzello , Alessandro Scaggion","doi":"10.1016/j.phro.2025.100703","DOIUrl":"10.1016/j.phro.2025.100703","url":null,"abstract":"<div><h3>Background and purpose</h3><div>Knowledge-Based Planning (KBP) is increasingly used to standardize and optimize radiotherapy planning. This study aims to develop, refine, and compare multicentric KBP models for craniospinal irradiation (CSI) in pediatric patients.</div></div><div><h3>Materials and methods</h3><div>A total of 113 CSI treatments from three Italian centers were collected, comprising Computed Tomography scans, target and organ contours, and treatment plans. Treatment techniques included Helical Tomotherapy (HT) and Volumetric Modulated Arc Therapy (VMAT). Three KBP models were developed: a full model (F-model) using data from 87 patients, a reduced model (R-model) based on a subset of the same sample, and a replanned model (RP-model) using KBP re-optimized plans. Models’ quality was evaluated using goodness-of-fit and goodness-of-prediction metrics, and their performance was assessed on a validation set of 26 patients through dose-volume histogram (DVH) comparisons, prediction bias, and variance analysis.</div></div><div><h3>Results</h3><div>The F-model and R-model exhibited similar quality and predictive ability, reflecting the variability of the original dataset and resulting in broad prediction intervals in low to mid-dose ranges. The RP-model achieved the highest quality, with narrower prediction bands. The RP-model is preferable for standardizing planning across centers, while the F-model is better suited for quality assurance as it captures clinical variability.</div></div><div><h3>Conclusions</h3><div>KBP models can effectively predict DVHs despite extreme geometric variability. However, models trained on highly variable datasets cannot simultaneously achieve high precision and accuracy. Comparing KBP models is essential for establishing benchmarks to meet specific clinical goals, particularly for complex pediatric CSI treatments.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"33 ","pages":"Article 100703"},"PeriodicalIF":3.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143130346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.phro.2025.100699
Djoya Hattu, Daisy Emans, Janine Bouten, Richard Canters, Judith van Loon, Dirk De Ruysscher
Background and purpose
In non-small cell lung cancer (NSCLC) a significant portion of the planning target volume (PTV) margin accommodates for anatomical changes during treatment. Patients with no or minimal anatomical changes might therefore benefit from a reduced PTV margin, resulting in lower organ at risk (OAR) doses. We evaluated a plan of the day approach using different PTV margins to quantify its effect on OAR and clinical target volume (CTV) dose.
Materials and methods
Twenty NSCLC patients were included in this retrospective study. CBCTs of all fractions were evaluated using an image-guided radiotherapy (IGRT) protocol to classify fractions into two groups: no or minimal anatomical changes to which reduced PTV margin plans (5 or 2 mm) were assigned, or with anatomical changes that received the reference treatment plan (8 mm PTV margin). OAR doses were investigated and CTV coverage was evaluated using CBCT dose recalculations.
Results
All plans showed decreased OAR dose when the PTV margin was reduced from 8 mm to 5 mm or 2 mm. The IGRT protocol selected 254/600 fractions in 19/20 patients, that could be treated with a smaller margin. CTV V95% remained ≥95% in 94% of the 5 mm plans and 87% of the 2 mm plans, compared to 98% of the reference 8 mm plans.
Conclusion
The IGRT protocol could identify fractions with no or minimal anatomical changes allowing a plan of the day approach to reduce PTV margins. Target coverage remained adequate in the majority of patients, while reducing OAR doses.
{"title":"Adaptive treatment margins to reduce organs at risk dose in patients with no or minimal anatomical changes in radiotherapy of non-small cell lung cancer","authors":"Djoya Hattu, Daisy Emans, Janine Bouten, Richard Canters, Judith van Loon, Dirk De Ruysscher","doi":"10.1016/j.phro.2025.100699","DOIUrl":"10.1016/j.phro.2025.100699","url":null,"abstract":"<div><h3>Background and purpose</h3><div>In non-small cell lung cancer (NSCLC) a significant portion of the planning target volume (PTV) margin accommodates for anatomical changes during treatment. Patients with no or minimal anatomical changes might therefore benefit from a reduced PTV margin, resulting in lower organ at risk (OAR) doses. We evaluated a plan of the day approach using different PTV margins to quantify its effect on OAR and clinical target volume (CTV) dose.</div></div><div><h3>Materials and methods</h3><div>Twenty NSCLC patients were included in this retrospective study. CBCTs of all fractions were evaluated using an image-guided radiotherapy (IGRT) protocol to classify fractions into two groups: no or minimal anatomical changes to which reduced PTV margin plans (5 or 2 mm) were assigned, or with anatomical changes that received the reference treatment plan (8 mm PTV margin). OAR doses were investigated and CTV coverage was evaluated using CBCT dose recalculations.</div></div><div><h3>Results</h3><div>All plans showed decreased OAR dose when the PTV margin was reduced from 8 mm to 5 mm or 2 mm. The IGRT protocol selected 254/600 fractions in 19/20 patients, that could be treated with a smaller margin. CTV V<sub>95%</sub> remained ≥95% in 94% of the 5 mm plans and 87% of the 2 mm plans, compared to 98% of the reference 8 mm plans.</div></div><div><h3>Conclusion</h3><div>The IGRT protocol could identify fractions with no or minimal anatomical changes allowing a plan of the day approach to reduce PTV margins. Target coverage remained adequate in the majority of patients, while reducing OAR doses.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"33 ","pages":"Article 100699"},"PeriodicalIF":3.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143130457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.phro.2025.100723
Moritz Schneider , Simon Gutwein , David Mönnich , Cihan Gani , Paul Fischer , Christian F. Baumgartner , Daniela Thorwarth
Background and purpose
Online adaptive magnetic resonance imaging (MRI)-guided radiotherapy requires fast dose calculation algorithms to reduce intra-fraction motion uncertainties and improve workflow efficiency. While Monte-Carlo simulations are precise but computationally intensive, neural networks promise fast and accurate dose modelling in strong magnetic fields. This study aimed to train and evaluate a deep neural network for dose modelling in MRI-guided radiotherapy using a comprehensive clinical dataset.
Materials and methods
A dataset of 6595 clinical irradiation segments from 125 1.5 T MRI-Linac radiotherapy plans for various tumors sites was used. A 3D U-Net was trained with 3961 segments using 3D imaging data and field parameters as input, Root Mean Squared Error and a custom loss function, with full Monte-Carlo simulations as ground truth. For 2656 segments from 50 patients, gamma pass rates (γ-PR) for 3 mm/3%, 2 mm/2%, and 1 mm/1% criteria were calculated to assess dose modelling accuracy. Performance was also tested in a standardized water phantom to evaluate basic radiation physics properties.
Results
The neural network accurately modeled dose distributions in both patient and water phantom settings. Median (range) γ-PR of 97.7% (87.5–100.0%), 89.1% (69.7–99.4%), and 60.8% (38.5–82.1%) were observed for treatment plans, and 97.1% (55.5–100.0%), 88.8% (38.8–99.7%), and 61.7% (17.9–94.4%) for individual segments, across the three criteria.
Conclusion
High median γ-PR and accurate modelling in both water phantom and clinical data demonstrate the high potential of neural networks for dose modelling. However, instances of lower γ-PR highlight the need for comprehensive test data, improved robustness and future built-in uncertainty estimation.
{"title":"Development and comprehensive clinical validation of a deep neural network for radiation dose modelling to enhance magnetic resonance imaging guided radiotherapy","authors":"Moritz Schneider , Simon Gutwein , David Mönnich , Cihan Gani , Paul Fischer , Christian F. Baumgartner , Daniela Thorwarth","doi":"10.1016/j.phro.2025.100723","DOIUrl":"10.1016/j.phro.2025.100723","url":null,"abstract":"<div><h3>Background and purpose</h3><div>Online adaptive magnetic resonance imaging (MRI)-guided radiotherapy requires fast dose calculation algorithms to reduce intra-fraction motion uncertainties and improve workflow efficiency. While Monte-Carlo simulations are precise but computationally intensive, neural networks promise fast and accurate dose modelling in strong magnetic fields. This study aimed to train and evaluate a deep neural network for dose modelling in MRI-guided radiotherapy using a comprehensive clinical dataset.</div></div><div><h3>Materials and methods</h3><div>A dataset of 6595 clinical irradiation segments from 125 1.5 T MRI-Linac radiotherapy plans for various tumors sites was used. A 3D U-Net was trained with 3961 segments using 3D imaging data and field parameters as input, Root Mean Squared Error and a custom loss function, with full Monte-Carlo simulations as ground truth. For 2656 segments from 50 patients, gamma pass rates (γ-PR) for 3 mm/3%, 2 mm/2%, and 1 mm/1% criteria were calculated to assess dose modelling accuracy. Performance was also tested in a standardized water phantom to evaluate basic radiation physics properties.</div></div><div><h3>Results</h3><div>The neural network accurately modeled dose distributions in both patient and water phantom settings. Median (range) γ-PR of 97.7% (87.5–100.0%), 89.1% (69.7–99.4%), and 60.8% (38.5–82.1%) were observed for treatment plans, and 97.1% (55.5–100.0%), 88.8% (38.8–99.7%), and 61.7% (17.9–94.4%) for individual segments, across the three criteria.</div></div><div><h3>Conclusion</h3><div>High median γ-PR and accurate modelling in both water phantom and clinical data demonstrate the high potential of neural networks for dose modelling. However, instances of lower γ-PR highlight the need for comprehensive test data, improved robustness and future built-in uncertainty estimation.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"33 ","pages":"Article 100723"},"PeriodicalIF":3.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143480620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tumors and fiducial markers do not always exhibit synchronous motion across different respiratory phases, in a phenomenon called the target localization error (TLE). We determined the margin to compensate for the TLE using four-dimensional computed tomography (4D-CT).
Materials and methods
We analyzed data from 21 lung tumor patients with fiducial markers; 11 for TLE determination and 10 for validation. Shifted CT images were generated by aligning the centroids of the fiducial markers in the reference phase of 4D-CT with those in each respiratory phase, and the union of gross tumor volumes (GTVs) was determined (). Conversely, variations in GTV centroids across the respiratory phases were calculated, and the 95th percentile of the root mean square error was defined as the TLE. Using this TLE, a GTV with an added TLE () was generated in the reference phase. Subsequently, a treatment plan assuming dynamic tumor tracking (DTT) was created for the planning target volume, derived by adding an isotropic 5 mm margin to , and the dose coverage for was evaluated.
Results
The TLEs (standard deviations of the root mean square error) were 2.0 (0.8) mm, 2.1(0.7) mm, and 3.2 (1.1) mm in the left − right, anterior − posterior, and superior − inferior directions, respectively. A dosimetric evaluation revealed that did not receive 100 % of the prescribed dose in four of 10 cases owing to artifacts.
Conclusion
The TLE can be compensated by adding an anisotropic margin to the GTV in the reference phase, a critical consideration in DTT.
{"title":"Margins to compensate for respiratory-induced mismatches between lung tumor and fiducial marker positions using four-dimensional computed tomography","authors":"Seiya Matsumoto , Nobutaka Mukumoto , Tomohiro Ono , Hiraku Iramina , Hideaki Hirashima , Takanori Adachi , Yuki Miyabe , Noriko Kishi , Takashi Mizowaki , Mitsuhiro Nakamura","doi":"10.1016/j.phro.2025.100728","DOIUrl":"10.1016/j.phro.2025.100728","url":null,"abstract":"<div><h3>Background and purpose</h3><div>Tumors and fiducial markers do not always exhibit synchronous motion across different respiratory phases, in a phenomenon called the target localization error (TLE). We determined the margin to compensate for the TLE using four-dimensional computed tomography (4D-CT).</div></div><div><h3>Materials and methods</h3><div>We analyzed data from 21 lung tumor patients with fiducial markers; 11 for TLE determination and 10 for validation. Shifted CT images were generated by aligning the centroids of the fiducial markers in the reference phase of 4D-CT with those in each respiratory phase, and the union of gross tumor volumes (GTVs) was determined (<span><math><msubsup><mrow><mi>G</mi><mi>T</mi><mi>V</mi></mrow><mrow><mi>u</mi><mi>n</mi><mi>i</mi><mi>o</mi><mi>n</mi></mrow><mrow><mi>s</mi><mi>h</mi><mi>i</mi><mi>f</mi><mi>t</mi></mrow></msubsup></math></span>). Conversely, variations in GTV centroids across the respiratory phases were calculated, and the 95th percentile of the root mean square error was defined as the TLE. Using this TLE, a GTV with an added TLE (<span><math><msubsup><mrow><mi>G</mi><mi>T</mi><mi>V</mi></mrow><mrow><mi>T</mi><mi>L</mi><mi>E</mi></mrow><mrow><mi>r</mi><mi>e</mi><mi>f</mi></mrow></msubsup></math></span>) was generated in the reference phase. Subsequently, a treatment plan assuming dynamic tumor tracking (DTT) was created for the planning target volume, derived by adding an isotropic 5 mm margin to <span><math><msubsup><mrow><mi>G</mi><mi>T</mi><mi>V</mi></mrow><mrow><mi>T</mi><mi>L</mi><mi>E</mi></mrow><mrow><mi>r</mi><mi>e</mi><mi>f</mi></mrow></msubsup></math></span>, and the dose coverage for <span><math><msubsup><mrow><mi>G</mi><mi>T</mi><mi>V</mi></mrow><mrow><mi>u</mi><mi>n</mi><mi>i</mi><mi>o</mi><mi>n</mi></mrow><mrow><mi>s</mi><mi>h</mi><mi>i</mi><mi>f</mi><mi>t</mi></mrow></msubsup></math></span> was evaluated.</div></div><div><h3>Results</h3><div>The TLEs (standard deviations of the root mean square error) were 2.0 (0.8) mm, 2.1(0.7) mm, and 3.2 (1.1) mm in the left − right, anterior − posterior, and superior − inferior directions, respectively. A dosimetric evaluation revealed that <span><math><msubsup><mrow><mi>G</mi><mi>T</mi><mi>V</mi></mrow><mrow><mi>u</mi><mi>n</mi><mi>i</mi><mi>o</mi><mi>n</mi></mrow><mrow><mi>s</mi><mi>h</mi><mi>i</mi><mi>f</mi><mi>t</mi></mrow></msubsup></math></span> did not receive 100 % of the prescribed dose in four of 10 cases owing to artifacts.</div></div><div><h3>Conclusion</h3><div>The TLE can be compensated by adding an anisotropic margin to the GTV in the reference phase, a critical consideration in DTT.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"33 ","pages":"Article 100728"},"PeriodicalIF":3.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143446138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.phro.2025.100747
Deqi Chen , Xiongtao Yang , Shirui Qin , Xiufen Li , Jianrong Dai , Yuan Tang , Kuo Men
Background and purpose
Adaptive radiotherapy for patients with rectal cancer using a magnetic resonance–guided linear accelerator has limitations in managing bladder shape variations. Conventional couch shifts may result in missing the target while requiring a large margin. Conversely, fully adaptive strategy is time-consuming. Therefore, a more efficient strategy for online adaptive radiotherapy is required.
Materials and methods
This retrospective study included 50 fractions from 10 patients with rectal cancer undergoing preoperative radiotherapy. The proposed method involved preparing a library of reference plans (LoRP) based on diverse bladder shapes. For each fraction, a plan from the LoRP was selected based on daily bladder filling. This plan was compared with those generated by conventional couch shift and fully adaptive strategies. The clinical acceptability of the plans (i.e., per protocol, variation-acceptable, or unacceptable) was assessed.
Results
In per protocol criterion, 44 %, 6 %, and 100 % of the plans for LoRP, conventional couch shift, and fully adaptive strategies were achieved, respectively. In variation-acceptable criterion, 92 % of LoRP plans and 74 % of conventional couch shift plans were achieved. LoRP demonstrated 94 % target coverage (100 % prescription dose) in the fully adaptive strategy compared with 91 % in conventional couch shift strategy. The fully adaptive strategy had the best performance in sparing the intestine and colon. LoRP reduced the treatment session duration by more than a third (>20 min) compared with the fully adaptive strategy.
Conclusion
LoRP achieved adequate target coverage with a short treatment session duration, potentially increasing treatment efficiency and improving patient comfort.
{"title":"Efficient strategy for magnetic resonance image-guided adaptive radiotherapy of rectal cancer using a library of reference plans","authors":"Deqi Chen , Xiongtao Yang , Shirui Qin , Xiufen Li , Jianrong Dai , Yuan Tang , Kuo Men","doi":"10.1016/j.phro.2025.100747","DOIUrl":"10.1016/j.phro.2025.100747","url":null,"abstract":"<div><h3>Background and purpose</h3><div>Adaptive radiotherapy for patients with rectal cancer using a magnetic resonance–guided linear accelerator has limitations in managing bladder shape variations. Conventional couch shifts may result in missing the target while requiring a large margin. Conversely, fully adaptive strategy is time-consuming. Therefore, a more efficient strategy for online adaptive radiotherapy is required.</div></div><div><h3>Materials and methods</h3><div>This retrospective study included 50 fractions from 10 patients with rectal cancer undergoing preoperative radiotherapy. The proposed method involved preparing a library of reference plans (LoRP) based on diverse bladder shapes. For each fraction, a plan from the LoRP was selected based on daily bladder filling. This plan was compared with those generated by conventional couch shift and fully adaptive strategies. The clinical acceptability of the plans (i.e., per protocol, variation-acceptable, or unacceptable) was assessed.</div></div><div><h3>Results</h3><div>In per protocol criterion, 44 %, 6 %, and 100 % of the plans for LoRP, conventional couch shift, and fully adaptive strategies were achieved, respectively. In variation-acceptable criterion, 92 % of LoRP plans and 74 % of conventional couch shift plans were achieved. LoRP demonstrated 94 % target coverage (100 % prescription dose) in the fully adaptive strategy compared with 91 % in conventional couch shift strategy. The fully adaptive strategy had the best performance in sparing the intestine and colon. LoRP reduced the treatment session duration by more than a third (>20 min) compared with the fully adaptive strategy.</div></div><div><h3>Conclusion</h3><div>LoRP achieved adequate target coverage with a short treatment session duration, potentially increasing treatment efficiency and improving patient comfort.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"33 ","pages":"Article 100747"},"PeriodicalIF":3.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143547974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-01DOI: 10.1016/j.phro.2024.100662
Martina Murr , Daniel Wegener , Simon Böke , Cihan Gani , David Mönnich , Maximilian Niyazi , Moritz Schneider , Daniel Zips , Arndt-Christian Müller , Daniela Thorwarth
Background and purpose
Conventional image-guided radiotherapy (conv-IGRT) is standard in prostate cancer (PC) but does not account for inter-fraction anatomical changes. Online-adaptive magnetic resonance-guided RT (OA-MRgRT) may improve organ-at-risk (OARs) sparing and clinical target volume (CTV) coverage. The aim of this study was to analyze accumulated OAR and target doses in PC after OA-MRgRT and conv-IGRT in comparison to pre-treatment reference planning (refPlan).
Material and methods
Ten patients with PC, previously treated with OA-MRgRT at the 1.5 T MR-Linac (20x3Gy), were included. Accumulated OA-MRgRT doses were determined by deformably registering all fraction’s MR-images. Conv-IGRT was simulated through rigid registration of the planning computed tomography with each fraction’s MR-image for dose mapping/accumulation. Dose-volume parameters (DVPs), including CTV D50% and D98%, rectum, bladder, urethra, Dmax and V56Gy for OA-MRgRT, conv-IGRT and refPlan were compared using the Wilcoxon signed-rank test. Clinical relevance of accumulated dose differences was analyzed using a normal-tissue complication-probability model.
Results
CTV-DVPs were comparable, whereas OA-MRgRT yielded decreased median OAR-DVPs compared to conv-IGRT, except for bladder V56Gy. OA-MRgRT demonstrated significantly lower median rectum Dmax over conv-IGRT (59.1/59.9 Gy, p = 0.006) and refPlan (60.1 Gy, p = 0.012). Similarly, OA-MRgRT yielded reduced median bladder Dmax compared to conv-IGRT (60.0/60.4 Gy, p = 0.006), and refPlan (61.2 Gy, p = 0.002). Overall, accumulated dose differences were small and did not translate into clinically relevant effects.
Conclusion
Deformably accumulated OA-MRgRT using 20x3Gy in PC showed significant but small dosimetric differences comparted to conv-IGRT. Feasibility of a dose accumulation methodology was demonstrated, which may be relevant for evaluating future hypo-fractionated OA-MRgRT approaches.
{"title":"Comparison of online adaptive and non-adaptive magnetic resonance image-guided radiation therapy in prostate cancer using dose accumulation","authors":"Martina Murr , Daniel Wegener , Simon Böke , Cihan Gani , David Mönnich , Maximilian Niyazi , Moritz Schneider , Daniel Zips , Arndt-Christian Müller , Daniela Thorwarth","doi":"10.1016/j.phro.2024.100662","DOIUrl":"10.1016/j.phro.2024.100662","url":null,"abstract":"<div><h3>Background and purpose</h3><div>Conventional image-guided radiotherapy (conv-IGRT) is standard in prostate cancer (PC) but does not account for inter-fraction anatomical changes. Online-adaptive magnetic resonance-guided RT (OA-MRgRT) may improve organ-at-risk (OARs) sparing and clinical target volume (CTV) coverage. The aim of this study was to analyze accumulated OAR and target doses in PC after OA-MRgRT and conv-IGRT in comparison to pre-treatment reference planning (refPlan).</div></div><div><h3>Material and methods</h3><div>Ten patients with PC, previously treated with OA-MRgRT at the 1.5 T MR-Linac (20x3Gy), were included. Accumulated OA-MRgRT doses were determined by deformably registering all fraction’s MR-images. Conv-IGRT was simulated through rigid registration of the planning computed tomography with each fraction’s MR-image for dose mapping/accumulation. Dose-volume parameters (DVPs), including CTV D50% and D98%, rectum, bladder, urethra, Dmax and V56Gy for OA-MRgRT, conv-IGRT and refPlan were compared using the Wilcoxon signed-rank test. Clinical relevance of accumulated dose differences was analyzed using a normal-tissue complication-probability model.</div></div><div><h3>Results</h3><div>CTV-DVPs were comparable, whereas OA-MRgRT yielded decreased median OAR-DVPs compared to conv-IGRT, except for bladder V56Gy. OA-MRgRT demonstrated significantly lower median rectum Dmax over conv-IGRT (59.1/59.9 Gy, p = 0.006) and refPlan (60.1 Gy, p = 0.012). Similarly, OA-MRgRT yielded reduced median bladder Dmax compared to conv-IGRT (60.0/60.4 Gy, p = 0.006), and refPlan (61.2 Gy, p = 0.002). Overall, accumulated dose differences were small and did not translate into clinically relevant effects.</div></div><div><h3>Conclusion</h3><div>Deformably accumulated OA-MRgRT using 20x3Gy in PC showed significant but small dosimetric differences comparted to conv-IGRT. Feasibility of a dose accumulation methodology was demonstrated, which may be relevant for evaluating future hypo-fractionated OA-MRgRT approaches.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"32 ","pages":"Article 100662"},"PeriodicalIF":3.4,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142552813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-01DOI: 10.1016/j.phro.2024.100667
Cora Warda , Cihan Gani , Simon Boeke , David Mönnich , Moritz Schneider , Maximilian Niyazi , Daniela Thorwarth
Background and purpose
Despite recent advances of online image-guided high-precision patient positioning and adaptation using magnetic resonance imaging (MRI) or cone-beam computed tomography (CT), standard radiation therapy pathway still involves a dedicated simulation scan. The aim of this study was to evaluate the feasibility and planning quality of integrating a simulation-free treatment planning workflow for adaptive online MRI-guided radiation therapy on a 1.5 T MRI linear accelerator (MRI-Linac) in prostate cancer using diagnostic CT (dCT) scans.
Materials and methods
For ten patients with prostate cancer previously treated at the MRI-Linac with adaptive radiation therapy (42.7 Gy in 7 fractions), simulation-free reference plans based on dCT were retrospectively created, and adaptive plans were simulated for the first treatment fraction. Reference and adapted plans derived from both standard and simulation-free workflows were compared with regard to institutional dose/volume criteria, followed by statistical assessment using the paired Wilcoxon signed-rank test with a Bonferroni-corrected significance level of α = 0.025.
Results
Simulation-free reference and adapted plans consistently met dose/volume criteria. Statistical analysis revealed no significant differences between both workflows, except median values for near-maximum dose (D2%) in the planning target volume: 44.2 Gy (standard) vs. 44.5 Gy (simulation-free) in reference plans (p = 0.01), and 44.5 Gy vs. 44.6 Gy in adapted plans (p = 0.01).
Conclusion
This study demonstrated the feasibility of simulation-free radiation therapy planning using dCT. Comparable treatment plan quality was observed for both reference and adapted radiation therapy plans in a curative setting for patients with prostate cancer.
{"title":"Simulation-free magnetic resonance-guided radiation therapy of prostate cancer","authors":"Cora Warda , Cihan Gani , Simon Boeke , David Mönnich , Moritz Schneider , Maximilian Niyazi , Daniela Thorwarth","doi":"10.1016/j.phro.2024.100667","DOIUrl":"10.1016/j.phro.2024.100667","url":null,"abstract":"<div><h3>Background and purpose</h3><div>Despite recent advances of online image-guided high-precision patient positioning and adaptation using magnetic resonance imaging (MRI) or cone-beam computed tomography (CT), standard radiation therapy pathway still involves a dedicated simulation scan. The aim of this study was to evaluate the feasibility and planning quality of integrating a simulation-free treatment planning workflow for adaptive online MRI-guided radiation therapy on a 1.5 T MRI linear accelerator (MRI-Linac) in prostate cancer using diagnostic CT (dCT) scans.</div></div><div><h3>Materials and methods</h3><div>For ten patients with prostate cancer previously treated at the MRI-Linac with adaptive radiation therapy (42.7 Gy in 7 fractions), simulation-free reference plans based on dCT were retrospectively created, and adaptive plans were simulated for the first treatment fraction. Reference and adapted plans derived from both standard and simulation-free workflows were compared with regard to institutional dose/volume criteria, followed by statistical assessment using the paired Wilcoxon signed-rank test with a Bonferroni-corrected significance level of α = 0.025.</div></div><div><h3>Results</h3><div>Simulation-free reference and adapted plans consistently met dose/volume criteria. Statistical analysis revealed no significant differences between both workflows, except median values for near-maximum dose (D2%) in the planning target volume: 44.2 Gy (standard) vs. 44.5 Gy (simulation-free) in reference plans (p = 0.01), and 44.5 Gy vs. 44.6 Gy in adapted plans (p = 0.01).</div></div><div><h3>Conclusion</h3><div>This study demonstrated the feasibility of simulation-free radiation therapy planning using dCT. Comparable treatment plan quality was observed for both reference and adapted radiation therapy plans in a curative setting for patients with prostate cancer.</div></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"32 ","pages":"Article 100667"},"PeriodicalIF":3.4,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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