Commissioning and Comprehensive Quality Assurance of commercial 3D Treatment Planning System using IAEA Technical Report Series — 430

Abstract

The purpose of this work is to report the results of commissioning and to establish a quality assurance (QA) program for commercial 3D treatment planning system (TPS) based on IAEA Technical Report Series 430. Eclipse v 7.3.10, (Varian Medical Systems, Palo Alto, CA, U.S.A.) TPS was commissioned for a Clinac 6EX (Varian Medical Systems, Palo Alto, CA, USA) linear accelerator. CT images of a phantom with various known in-homogeneities were acquired. The images were transferred to TPS and tested for various parameters related to patient data acquisition, anatomical modeling, plan evaluation and dose calculation. Dosimetric parameters including open, asymmetric and wedged shaped fields, oblique incidence, buildup region behavior and SSD dependence were evaluated. Representative clinical cases were tested for MU calculation and point doses. The maximum variation between the measured and the known CT numbers was 20 +/- 11.7 HU (1 SD). The results of all non-dosimetric tests were found within tolerance, however expansion at the sharp corners was found distorted. The accuracy of the DVH calculations depends on the grid size. TPS calculations of all the dosimetric parameters were in good agreement with the measured values, however for asymmetric open and wedged fields, few points were found out of tolerance. Smaller grid size calculation showed better agreement of dose calculation in the build-up region. Independent tests for MU calculation showed a variation within +/-2% (relative to planning system), meanwhile variation of 3.0% was observed when the central axis was blocked. The test results were in agreement with the tolerance specified by IAEA TRS 430. A subset of the commissioning tests has been identified as a baseline data for an ongoing QA program.