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Type: Journal article
Title: Pre-treatment and real-time image guidance for a fixed-beam radiotherapy system
Author: Liu, P.Z.Y.
Gardner, M.
Heng, S.M.
Shieh, C.-C.
Nguyen, D.T.
Debrot, E.
O’Brien, R.
Downes, S.
Jackson, M.
Keall, P.J.
Citation: Physics in Medicine and Biology, 2021; 66(6):064003-1-064003-12
Publisher: IOP Publishing
Issue Date: 2021
ISSN: 0031-9155
Statement of
Paul Z Y Liu, Mark Gardner, Soo Min Heng, Chun-Chen Shieh, Doan Trang Nguyen, Emily Debrot ... et al.
Abstract: Purpose. A radiotherapy system with a fixed treatment beam and a rotating patient positioning system could be smaller, more robust and more cost effective compared to conventional rotating gantry systems. However, patient rotation could cause anatomical deformation and compromise treatment delivery. In this work, we demonstrate an image-guided treatment workflow with a fixed beam prototype system that accounts for deformation during rotation to maintain dosimetric accuracy. Methods. The prototype system consists of an Elekta Synergy linac with the therapy beam orientated downward and a custom-built patient rotation system (PRS). A phantom that deforms with rotation was constructed and rotated within the PRS to quantify the performance of two image guidance techniques: motion compensated cone-beam CT (CBCT) for pre-treatment volumetric imaging and kilovoltage infraction monitoring (KIM) for real-time image guidance. The phantom was irradiated with a 3D conformal beam to evaluate the dosimetric accuracy of the workflow. Results. The motion compensated CBCT was used to verify pre-treatment position and the average calculated position was within −0.3 ± 1.1 mm of the phantom's ground truth position at 0°. KIM tracked the position of the target in real-time as the phantom was rotated and the average calculated position was within −0.2 ± 0.8 mm of the phantom's ground truth position. A 3D conformal treatment delivered on the prototype system with image guidance had a 3%/2 mm gamma pass rate of 96.3% compared to 98.6% delivered using a conventional rotating gantry linac. Conclusions. In this work, we have shown that image guidance can be used with fixed-beam treatment systems to measure and account for changes in target position in order to maintain dosimetric coverage during horizontal rotation. This treatment modality could provide a viable treatment option when there insufficient space for a conventional linear accelerator or where the cost is prohibitive.
Keywords: Humans
Imaging, Three-Dimensional
Radiotherapy Planning, Computer-Assisted
Reproducibility of Results
Materials Testing
Phantoms, Imaging
Particle Accelerators
Cone-Beam Computed Tomography
Radiotherapy, Image-Guided
Description: Published 8 March 2021
Rights: © 2021 Institute of Physics and Engineering in Medicine
DOI: 10.1088/1361-6560/abdc12
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