Accuracy-dependent dose-constraints and dose-based safety margins for organs-at-risk in radiotherapy
Background and purpose: Geometrical uncertainties in radiotherapy are generally accounted for by margins for tumors, but their effect on organs-at-risk (OARs) is often ignored. We developed a model that incorporates dose- and geometry-based uncertainties in OAR planning using dose constraints. Mater...
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Elsevier
2025-01-01
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| Series: | Physics and Imaging in Radiation Oncology |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2405631625000181 |
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| author | Joep C. Stroom Sandra C. Vieira Carlo Greco Sebastiaan M.J.J.G. Nijsten |
| author_facet | Joep C. Stroom Sandra C. Vieira Carlo Greco Sebastiaan M.J.J.G. Nijsten |
| author_sort | Joep C. Stroom |
| collection | DOAJ |
| description | Background and purpose: Geometrical uncertainties in radiotherapy are generally accounted for by margins for tumors, but their effect on organs-at-risk (OARs) is often ignored. We developed a model that incorporates dose- and geometry-based uncertainties in OAR planning using dose constraints. Materials and methods: Radiotherapy uncertainties cause real dose-volume histograms (DVHs) to spread around the planned DVH. With a published OAR dose constraint D(Vcrit) < Dcrit such that complication probability < Y%, real differences from planned Dcrit can be described by mean- (MDDcrit) and standard deviations (SDDcrit). Assuming complications are associated with the worst DVHs, New dose constraints that maintain complication probability can be derived for new treatments:Dcrit,New = Dcrit,publ + Φ−1(1 - Y%) * (SDDcrit,publ - SDDcrit,New) + (MDDcrit,publ - MDDcrit,New),with Φ−1(x) the inverse cumulative normal distribution function. Setting SDDcrit,New = MDDcrit,New = 0 in the recipe yields the “True” critical dose, and Dcrit,True - Dcrit,publ can be considered a dose-based safety margin (DSM).As hypothetical example, we estimated MDDcrit and SDDcrit values by simulating geometric errors in our clinical treatment plans and adding dose-based uncertainty. Over 1000 OARs with 108 different regular- and hypo-fractionation constraints were simulated. We assumed accuracy SDs to change from 2.5mm/3% to 1.5mm/2%. Results: Results varied per OAR, fractionation, and constraint-type. If our 2.5mm/3% MDDcrit and SDDcrit values approximated dose-constraint studies, on average the DSM would be 4.5 Gy (18%) and our dose constraints would increase with 1.2 Gy (5%). Conclusions: We introduced a first model relating dose constraints and complication probabilities with treatment uncertainties and safety margins for OARs. Among other things, it quantified how higher constraints can be applied with increasing radiotherapy accuracy. |
| format | Article |
| id | doaj-art-ce0c1b50fb9346ba837fd3c1eb68e3a6 |
| institution | Kabale University |
| issn | 2405-6316 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Physics and Imaging in Radiation Oncology |
| spelling | doaj-art-ce0c1b50fb9346ba837fd3c1eb68e3a62025-02-06T05:12:28ZengElsevierPhysics and Imaging in Radiation Oncology2405-63162025-01-0133100713Accuracy-dependent dose-constraints and dose-based safety margins for organs-at-risk in radiotherapyJoep C. Stroom0Sandra C. Vieira1Carlo Greco2Sebastiaan M.J.J.G. Nijsten3Department of Radiation Oncology Champalimaud Centre for the Unknown Lisbon Portugal; Corresponding authors at: Department of Radiation Oncology, Champalimaud Centre for the Unknown, Av. De Brasília s/n (Doca de Pedrouços), 1400 - 038 Lisboa, Portugal.Department of Radiation Oncology Champalimaud Centre for the Unknown Lisbon PortugalDepartment of Radiation Oncology Champalimaud Centre for the Unknown Lisbon PortugalRadiotherapy Department MAASTRO Clinic Maastricht the NetherlandsBackground and purpose: Geometrical uncertainties in radiotherapy are generally accounted for by margins for tumors, but their effect on organs-at-risk (OARs) is often ignored. We developed a model that incorporates dose- and geometry-based uncertainties in OAR planning using dose constraints. Materials and methods: Radiotherapy uncertainties cause real dose-volume histograms (DVHs) to spread around the planned DVH. With a published OAR dose constraint D(Vcrit) < Dcrit such that complication probability < Y%, real differences from planned Dcrit can be described by mean- (MDDcrit) and standard deviations (SDDcrit). Assuming complications are associated with the worst DVHs, New dose constraints that maintain complication probability can be derived for new treatments:Dcrit,New = Dcrit,publ + Φ−1(1 - Y%) * (SDDcrit,publ - SDDcrit,New) + (MDDcrit,publ - MDDcrit,New),with Φ−1(x) the inverse cumulative normal distribution function. Setting SDDcrit,New = MDDcrit,New = 0 in the recipe yields the “True” critical dose, and Dcrit,True - Dcrit,publ can be considered a dose-based safety margin (DSM).As hypothetical example, we estimated MDDcrit and SDDcrit values by simulating geometric errors in our clinical treatment plans and adding dose-based uncertainty. Over 1000 OARs with 108 different regular- and hypo-fractionation constraints were simulated. We assumed accuracy SDs to change from 2.5mm/3% to 1.5mm/2%. Results: Results varied per OAR, fractionation, and constraint-type. If our 2.5mm/3% MDDcrit and SDDcrit values approximated dose-constraint studies, on average the DSM would be 4.5 Gy (18%) and our dose constraints would increase with 1.2 Gy (5%). Conclusions: We introduced a first model relating dose constraints and complication probabilities with treatment uncertainties and safety margins for OARs. Among other things, it quantified how higher constraints can be applied with increasing radiotherapy accuracy.http://www.sciencedirect.com/science/article/pii/S2405631625000181OAR dose constraintsTreatment uncertaintiesOAR safety marginsError simulationsRecipes |
| spellingShingle | Joep C. Stroom Sandra C. Vieira Carlo Greco Sebastiaan M.J.J.G. Nijsten Accuracy-dependent dose-constraints and dose-based safety margins for organs-at-risk in radiotherapy Physics and Imaging in Radiation Oncology OAR dose constraints Treatment uncertainties OAR safety margins Error simulations Recipes |
| title | Accuracy-dependent dose-constraints and dose-based safety margins for organs-at-risk in radiotherapy |
| title_full | Accuracy-dependent dose-constraints and dose-based safety margins for organs-at-risk in radiotherapy |
| title_fullStr | Accuracy-dependent dose-constraints and dose-based safety margins for organs-at-risk in radiotherapy |
| title_full_unstemmed | Accuracy-dependent dose-constraints and dose-based safety margins for organs-at-risk in radiotherapy |
| title_short | Accuracy-dependent dose-constraints and dose-based safety margins for organs-at-risk in radiotherapy |
| title_sort | accuracy dependent dose constraints and dose based safety margins for organs at risk in radiotherapy |
| topic | OAR dose constraints Treatment uncertainties OAR safety margins Error simulations Recipes |
| url | http://www.sciencedirect.com/science/article/pii/S2405631625000181 |
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