Four-dimensional dose calculations for dynamic tumour tracking with a gimbal-mounted linear accelerator.

Autor: Carpentier EE; Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada.; Department of Medical Physics, BC Cancer - Vancouver, Vancouver, BC, Canada., McDermott RL; Radiation Oncology, BC Cancer Vancouver, Vancouver, BC, Canada., Dunne EM; Radiation Oncology, BC Cancer Vancouver, Vancouver, BC, Canada., Camborde MA; Department of Medical Physics, BC Cancer - Vancouver, Vancouver, BC, Canada., Bergman AM; Department of Medical Physics, BC Cancer - Vancouver, Vancouver, BC, Canada., Karan T; Department of Medical Physics, BC Cancer - Vancouver, Vancouver, BC, Canada., Liu MCC; Radiation Oncology, BC Cancer Vancouver, Vancouver, BC, Canada., Ma RMK; Radiation Oncology, BC Cancer Vancouver, Vancouver, BC, Canada., Mestrovic A; Department of Medical Physics, BC Cancer - Vancouver, Vancouver, BC, Canada.
Jazyk: angličtina
Zdroj: Journal of applied clinical medical physics [J Appl Clin Med Phys] 2021 Jun; Vol. 22 (6), pp. 16-25. Date of Electronic Publication: 2021 May 27.
DOI: 10.1002/acm2.13265
Abstrakt: Purpose: In this study we present a novel method for re-calculating a treatment plan on different respiratory phases by accurately modeling the panning and tilting beam motion during DTT (the "rotation method"). This method is used to re-calculate the dose distribution of a plan on multiple breathing phases to accurately assess the dosimetry.
Methods: sIMRT plans were optimized on a breath hold computed tomography (CT) image taken at exhale (BH exhale ) for 10 previous liver stereotactic ablative radiotherapy patients. Our method was used to re-calculate the plan on the inhale (0%) and exhale (50%) phases of the four-dimensional CT (4DCT) image set. The dose distributions were deformed to the BH exhale CT and summed together with proper weighting calculated from the patient's breathing trace. Subsequently, the plan was re-calculated on all ten phases using our method and the dose distributions were deformed to the BH exhale CT and accumulated together. The maximum dose for certain organs at risk (OARs) was compared between calculating on two phases and all ten phases.
Results: In total, 26 OARs were examined from 10 patients. When the dose was calculated on the inhale and exhale phases six OARs exceeded their dose limit, and when all 10 phases were used five OARs exceeded their limit.
Conclusion: Dynamic tumor tracking plans optimized for a single respiratory phase leave an OAR vulnerable to exceeding its dose constraint during other respiratory phases. The rotation method accurately models the beam's geometry. Using deformable image registration to accumulate dose from all 10 breathing phases provides the most accurate results, however it is a time consuming procedure. Accumulating the dose from two extreme breathing phases (exhale and inhale) and weighting them properly provides accurate results while requiring less time. This approach should be used to confirm the safety of a DTT treatment plan prior to delivery.
(© 2021 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.)
Databáze: MEDLINE
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