End-to-end quality assurance for Volumetric Modulated Arc Therapy with Fricke-Xylenol orange-Gelatin gel dosimeters and dual-wavelength cone-beam optical CT scanner

Abstract

The whole treatment process undergone by patients in clinics with Volumetric Modulated Arc Therapy (VMAT) can be tested by implementing 3D end-to-end (E2E) quality assurance with gel dosimetry. In this work, a 3D E2E test was performed in a head phantom for the verification of a VMAT treatment, using FXG (Fricke-Xylenol orange-Gelatin) gel dosimetry and a newly developed dual-wavelength reading method on a cone-beam optical CT scanner. This dosimetric method intends to enable accurate measurements in the out-of-field zone and in the tumor volume, with an effective dose range up to 10 Gy. CT images of the phantom with a gel flask were used to create a treatment plan with a brain tumor of complex shape. A very good agreement between 90 %, 80 %, 60 % and 40 % isodose curves and high 3D γ passing rates (2%/2mm) of 98.6 % and 96.7 % between measured and computed dose maps showed that E2E tests can be successfully implemented with this novel dosimetric method.