Quantitative comparison of different dosimetry methods in orthovoltage X-ray therapy

Abstract

Gamma index metric is frequently used for dose verification in quality control (QC) procedures for clinical radiation therapy. Monte Carlo (MC) simulations and radiochromic films can be used to validate complex dose plans for recording dose distributions in irradiated volume. When metal artifacts are present in the anatomical region of interest, a quantitative comparison of planned and experimental (mathematical simulation/physical study) dose using the gamma index metric and its 2D derivative may allow better weighted dose planning decisions. The purpose of this study was to use the gamma index derivative - 2D-dose/distance index (2DDI) to compare quantitatively different dosimetry methods used for evaluating dose distributions in orthovoltage X-ray therapy. 2DDI was validated by assessing the program's capabilities when comparing Monte Carlo simulated (FLUKA) dose distribution with EBT3 and RTQA2 film dosimetry. The proposed 2D-dose/distance index was found to be sensitive enough to assess dose discrepancies and dose distribution misalignments between two dosimetry methods that were also used to verify doses in objects with metal artifacts inside. The findings imply that 2DDI could be used for quality control in orthovoltage radiotherapy in complex cases involving metal artifacts in the anatomic region of interest.