Evaluation of a treatment planning and dose control system in external radiotherapy by experimental thermoluminescence dosimetry

Abstract

This thesis project aims to examine the compatibly of the calculated doses by the anisotropic analytical algorithm (AAA) and measured doses by thermoluminescent dosimeters (TLD) and therefore to evaluate the Eclipse-Varian TPS performance used in radiotherapy. Thus, it was a question to check if the treatment plans validated during the calculation phase is valid by dose measurement according to the ICRU recommendations on dose delivery to the treated volume (PTV) reported in reports 50 and 62. In this work, dose measurements was performed to evaluate an external radiotherapy treatment plan and, particularly, to validate dose calculations for a lung lesion case. Doses were calculated by the Varian Eclipse treatment planning system using the AAA algorithm. The measurements were performed using TLD700 and a Rando anthropomorphic phantom. The comparison between calculated and measured doses shows compatibility except for a few points, due to the limitations in the heterogeneity correction used for the case studied here. The deviation between calculated and measured doses was about 6.5% for low (<0.5Gy) doses, and about 1% for higher doses (>0.5Gy).The deviation between calculated and measured doses were also found to be higher in proximity to heterogeneous tissue interfaces.