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First study of on‐treatment volumetric imaging during respiratory gated VMAT
Author(s) -
Choi Kihwan,
Xing Lei,
Koong Albert,
Li Ruijiang
Publication year - 2013
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4794925
Subject(s) - imaging phantom , truebeam , medical imaging , linear particle accelerator , image guided radiation therapy , biomedical engineering , breathing , nuclear medicine , projection (relational algebra) , medicine , computer science , computer vision , radiology , beam (structure) , physics , anatomy , optics , algorithm
Purpose: To obtain on‐treatment volumetric patient anatomy during respiratory gated volumetric modulated arc therapy (VMAT).Methods: On‐board imaging device integrated with Linacs offers a viable tool for obtaining patient anatomy during radiation treatment delivery. In this study, the authors acquired beam‐level kV images during gated VMAT treatments using a Varian TrueBeam™STx Linac. These kV projection images are triggered by a respiratory gating signal and can be acquired immediately before treatment MV beam on at every breathing cycle during delivery. Because the kV images are acquired with an on‐board imaging device during a rotational arc therapy, they provide the patient anatomical information from many different angles or projection views (typically 20–40). To reconstruct the volumetric image representing patient anatomy during the VMAT treatment, the authors used a compressed sensing method with a fast first‐order optimization algorithm. The conventional FDK reconstruction was also used for comparison purposes. The method was tested on a dynamic anthropomorphic physical phantom as well as a lung patient.Results: The reconstructed volumetric images for a dynamic anthropomorphic physical phantom and a lung patient showed clearly visible soft‐tissue target as well as other anatomical structures, with the proposed compressed sensing‐based image reconstruction method. Compared with FDK, the compressed sensing method leads to a ∼two and threefold increase in contrast‐to‐noise ratio around the target area in the phantom and patient case, respectively.Conclusions: The proposed technique provides on‐treatment volumetric patient anatomy, with only a fraction (<10%) of the imaging dose used in conventional CBCT procedures. This anatomical information may be valuable for geometric verification and treatment guidance, and useful for verification of treatment dose delivery, accumulation, and adaptation in the future.