Dosimetric impact and detectability of multi-leaf collimator positioning errors on Varian Halcyon.

Dosimetric impact and detectability of multi-leaf collimator positioning errors on Varian Halcyon.
J Appl Clin Med Phys. 2019 Jul 11;:
Authors: Gay SS, Netherton TJ, Cardenas CE, Ger RB, Balter PA, Dong L, Mihailidis D, Court LE
Abstract
The purpose of this study is to investigate the dosimetric impact of multi-leaf collimator (MLC) positioning errors on a Varian Halcyon for both random and systematic errors, and to evaluate the effectiveness of portal dosimetry quality assurance in catching clinically significant changes caused by these errors. Both random and systematic errors were purposely added to 11 physician-approved head and neck volumetric modulated arc therapy (VMAT) treatment plans, yielding a total of 99 unique plans. Plans were then delivered on a preclinical Varian Halcyon linear accelerator and the fluence was captured by an opposed portal dosimeter. When comparing dose-volume histogram (DVH) values of plans with introduced MLC errors to known good plans, clinically significant changes to target structures quickly emerged for plans with systematic errors, while random errors caused less change. For both error types, the magnitude of clinically significant changes increased as error size increased. Portal dosimetry was able to detect all systematic errors, while random errors of ±5 mm or less were unlikely to be detected. Best detection of clinically significant errors, while minimizing false positives, was achieved b...

Source: Journal of Applied Clinical Medical Physics - July 10, 2019 Category: Physics Authors: Gay SS, Netherton TJ, Cardenas CE, Ger RB, Balter PA, Dong L, Mihailidis D, Court LE Tags: J Appl Clin Med Phys Source Type: research