A concept for anisotropic PTV margins including rotational setup uncertainties and its impact on the tumor control probability in canine brain tumors.

Autor:	Radonic S; Department of Physics, University of Zurich, Zurich, Switzerland.; Division of Radiation Oncology, Small Animal Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland., Besserer J; Department of Physics, University of Zurich, Zurich, Switzerland.; Radiotherapy Hirslanden AG, Rain 34, Aarau, Switzerland., Bley CR; Division of Radiation Oncology, Small Animal Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland., Schneider U; Department of Physics, University of Zurich, Zurich, Switzerland.; Radiotherapy Hirslanden AG, Rain 34, Aarau, Switzerland., Meier V; Department of Physics, University of Zurich, Zurich, Switzerland.; Division of Radiation Oncology, Small Animal Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.; Division of Radiation Oncology, Small Animal Department, University of Zurich Vetsuisse Faculty, Winterthurerstrasse 260, Zurich, Zürich, 8057, Switzerland.; Department of Physics, University of Zurich Faculty of Science, Winterthurerstrasse 190, Zurich, ZH, 8057, Switzerland.
Jazyk:	angličtina
Zdroj:	Biomedical physics & engineering express [Biomed Phys Eng Express] 2022 Sep 07; Vol. 8 (6). Date of Electronic Publication: 2022 Sep 07.
DOI:	10.1088/2057-1976/ac8a9f
Abstrakt:	Objective. In this modelling study, we pursued two main goals. The first was to establish a new CTV-to-PTV expansion which considers the closest and most critical organ at risk (OAR). The second goal was to investigate the impact of the planning target volume (PTV) margin size on the tumor control probability (TCP) and its dependence on the geometrical setup uncertainties. The aim was to achieve a smaller margin expansion close to the OAR while allowing a moderately larger expansion in less critical areas further away from the OAR and whilst maintaining the TCP. Approach. Imaging data of radiation therapy plans from pet dogs which had undergone radiation therapy for brain tumor were used to estimate the clinic specific rotational setup uncertainties. A Monte-Carlo methodology using a voxel-based TCP model was used to quantify the implications of rotational setup uncertainties on the TCP. A combination of algorithms was utilized to establish a computational CTV-to-PTV expansion method based on probability density. This was achieved by choosing a center of rotation close to an OAR. All required software modules were developed and integrated into a software package that directly interacts with the Varian Eclipse treatment planning system. Main results. Several uniform and non-isotropic PTVs were created. To ensure comparability and consistency, standardized RT plans with equal optimization constraints were defined, automatically applied and calculated on these targets. The resulting TCPs were then computed, evaluated and compared. Significance. The non-isotropic margins were found to result in larger TCPs with smaller margin excess volume. Further, we presented an additional application of the newly established CTV-to-PTV expansion method for radiation therapy of the spinal axis of human patients. (Creative Commons Attribution license.)
Databáze:	MEDLINE
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