Evaluating the effect of higher Monte Carlo statistical uncertainties on accumulated doses after daily adaptive fractionated radiotherapy in prostate cancer.

Autor: Jagt TZ; Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands., Janssen TM; Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands., Sonke JJ; Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands.
Jazyk: angličtina
Zdroj: Physics and imaging in radiation oncology [Phys Imaging Radiat Oncol] 2024 Sep 05; Vol. 32, pp. 100636. Date of Electronic Publication: 2024 Sep 05 (Print Publication: 2024).
DOI: 10.1016/j.phro.2024.100636
Abstrakt: Background and Purpose: Monte Carlo (MC) based dose calculations are widely used in radiotherapy with a low statistical uncertainty, being accurate but slow. Increasing the uncertainty accelerates the calculation, but reduces quality. In online adaptive planning, however, dose is recalculated every treatment fraction, potentially decreasing the cumulative calculation error. This study aimed to evaluate the effect of higher MC statistical uncertainty in the context of daily online plan adaptation.
Materials and Methods: For twenty prostate cancer patients, daily plans were simulated for 5 fractions and three modes of variation: rigid whole body translations, local-rigid prostate translations and local-rigid prostate rotations. For each mode and fraction, adaptive plans were generated from a clinical reference plan using three MC uncertainty values: 1 % (standard), 2 % and 3 % per plan. Dose-volume criteria were evaluated for accumulated doses, checking plan acceptability and comparing higher uncertainty plans to the standard.
Results: Increasing the statistical uncertainty setting from 1 % to 2-3 % caused an accumulated median target D 98 % reduction of 0.1 Gy, with interquartile ranges (IQRs) up to 0.12 Gy. Rectum V 35Gy increased in median up to 0.16 cm 3 with IQRs up to 0.33 cm 3 . The bladder V 28Gy and V 32Gy showed median increases up to 0.24 %-point, with IQRs up to 0.54 %-point. Using 2 % uncertainty reduced calculation times by more than a minute for all modes of variation, with no further time gain when increasing to 3 %.
Conclusion: A 2-3 % MC statistical uncertainty was clinically feasible. Using a 2 % uncertainty setting reduced calculation times at the cost of limited relative dose-volume differences.
Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: T. Janssen reports institutional funding from Elekta AB (Stockholm). J.-J. Sonke reports research grants from Elekta AB (Stockholm). Our department receives license fees from Elekta AB (Stockholm) for IGRT software.
(© 2024 The Authors. Published by Elsevier B.V. on behalf of European Society of Radiotherapy & Oncology.)
Databáze: MEDLINE
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