Comparative Analysis of Absolute Dosimetry of a Varian 2300iX LINAC for Photon and Electron Beams Using IAEA TRS-398 Rev. 1

Abstract

The accuracy of radiation dose output is one of the factors that determines the success of radiation therapy and patient safety. Therefore, an absolute dosimetry process based on international standards is required to ensure that the dose output from the Linear Accelerator (LINAC) is consistent with the planned dose. This study aimed to analyze absolute dosimetry results on a Varian 2300iX LINAC using the IAEA TRS-398 Rev.1 protocol for 6 MV photon and 6 MeV electron beams. Measurements were performed using a water phantom, a PTW 30013 Farmer Ionization Chamber for the photon beam, a PTW 34045 Advanced Markus Chamber for the electron beam, an electrometer, a thermometer, and a barometer under reference conditions with an SSD of 100 cm, a 10 × 10 cm² irradiation field, and 200 MU. Absorbed dose to water was calculated using the absorbed-dose-to-water approach with temperature and pressure (kTP), polarity (kpol), ion recombination (ks), and beam quality (kQ) correction factors. The results showed that before adjustment, the dose-output deviations were −0.860% for the 6 MV photon beam and −0.600% for the 6 MeV electron beam. After adjustment, the deviations changed to −0.050% for the 6 MV photon beam and 0.190% for the 6 MeV electron beam. All measurement results were within the ±2% tolerance recommended by IAEA TRS-398 Rev.1. Correction factors close to one indicated that the measurement conditions met international dosimetry requirements. The results demonstrate that the Varian 2300iX LINAC has good dosimetric performance and is suitable for radiotherapy services, provided that periodic quality assurance is maintained.