An EPID-based system for gantry-resolved MLC quality assurance for VMAT.

An EPID-based system for gantry-resolved MLC quality assurance for VMAT.
J Appl Clin Med Phys. 2016;17(5):6312
Authors: Zwan BJ, Barnes MP, Fuangord T, Stanton CJ, O'Connor DJ, Keall PJ, Greer PB
Abstract
Multileaf collimator (MLC) positions should be precisely and independently mea-sured as a function of gantry angle as part of a comprehensive quality assurance (QA) program for volumetric-modulated arc therapy (VMAT). It is also ideal that such a QA program has the ability to relate MLC positional accuracy to patient-specific dosimetry in order to determine the clinical significance of any detected MLC errors. In this work we propose a method to verify individual MLC trajectories during VMAT deliveries for use as a routine linear accelerator QA tool. We also extend this method to reconstruct the 3D patient dose in the treatment planning sys-tem based on the measured MLC trajectories and the original DICOM plan file. The method relies on extracting MLC positions from EPID images acquired at 8.41fps during clinical VMAT deliveries. A gantry angle is automatically tagged to each image in order to obtain the MLC trajectories as a function of gantry angle. This analysis was performed for six clinical VMAT plans acquired at monthly intervals for three months. The measured trajectories for each delivery were compared to the MLC positions from the DICOM plan file. The maximum mean error detected was 0.07 mm and a maximum root-mean-square er...

Source: Journal of Applied Clinical Medical Physics - September 30, 2016 Category: Physics Authors: Zwan BJ, Barnes MP, Fuangord T, Stanton CJ, O'Connor DJ, Keall PJ, Greer PB Tags: J Appl Clin Med Phys Source Type: research