Open AccessReal‐time high spatial resolution dose verification in stereotactic motion adaptive arc radiotherapy
Author(s) -
Duncan Mitchell,
Newall Matthew K.,
Caillet Vincent,
Booth Jeremy T.,
Keall Paul J.,
Lerch Michael,
Perevertaylo Vladimir,
Rosenfeld Anatoly B.,
Petasecca Marco
Publication year - 2018
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.12364
Subject(s) - multileaf collimator , imaging phantom , quality assurance , nuclear medicine , collimator , tracking (education) , computer science , physics , linear particle accelerator , optics , medicine , beam (structure) , psychology , pedagogy , external quality assessment , pathology
Purpose Radiation treatments delivered with real‐time multileaf collimator ( MLC ) tracking currently lack fast pretreatment or real‐time quality assurance. The purpose of this study is to test a 2D silicon detector, MagicPlate‐512 ( MP 512), in a complex clinical environment involving real‐time reconfiguration of the MLC leaves during target tracking. Methods MP 512 was placed in the center of a solid water phantom and mounted on a motion platform used to simulate three different patient motions. Electromagnetic target tracking was implemented using the Calypso system (Varian Medical Systems, Palo Alto, CA , USA) and an MLC tracking software. A two‐arc VMAT plan was delivered and 2D dose distributions were reconstructed by MP 512, EBT 3 film, and the Eclipse treatment planning system ( TPS ). Dose maps were compared using gamma analysis with 2%/2 mm and 3%/3 mm acceptance criteria. Dose profiles were generated in sup‐inf and lateral directions to show the agreement of MP 512 to EBT 3 and to highlight the efficacy of the MLC tracking system in mitigating the effect of the simulated patient motion. Results Using a 3%/3 mm acceptance criterion for 2D gamma analysis, MP 512 to EBT 3 film agreement was 99% and MP 512 to TPS agreement was 100%. For a 2%/2 mm criterion, the agreement was 95% and 98%, respectively. Full width at half maximum and 80%/20% penumbral width of the MP 512 and EBT 3 dose profiles agreed within 1 mm and 0.5 mm, respectively. Patient motion increased the measured dose profile penumbral width by nearly 2 mm (with respect to the no‐motion case); however, the MLC tracking strategy was able to mitigate 80% of this effect. Conclusions MP 512 is capable of high spatial resolution 2D dose reconstruction during adaptive MLC tracking, including arc deliveries. It shows potential as an effective tool for 2D small field dosimetry and pretreatment quality assurance for MLC tracking modalities. These results provide confidence that detector‐based pretreatment dosimetry is clinically feasible despite fast real‐time MLC reconfigurations.