Abstract
Introduction
Accurate electron beam dosimetry is crucial for effective radiotherapy treatment. This study aimed to validate modified electron beam calibration methods through a comprehensive cross-calibration analysis against the established IAEA TRS-398 and AAPM TG-51 protocols.
Materials and methods
A Varian Trilogy linac with electron beam energy of 6, 9, 12, 15, and 18 MeV was used to perform dosimetric assessments using cylindrical (FC65-G and CC13) and parallel-plate (PPC40) ion chambers. The sequential method was employed for cross-calibration at 18 MeV, with each chamber alternatively serving as the reference and field chambers according to TRS-398 (yielding calibration correction factor NTRS–398) and TG-51 (yielding calibration correction factor NTG–51) protocols. The ratios of NTRS–398 and NTG–51 compared to the calibration correction factors from country SSDL (NCo) it ranged from 0.990 to 1.020. Absorbed doses to water per monitor unit (cGy/MU) were calculated at maximum absorption depths.
Results
For modified calibration methods, the values of NTRS–398 and NTG–51 yielded absorbed dose values between 0.977-1.005 cGy/MU and 0.980-1.009 cGy/MU, respectively. Dose ratios of the modified methods compared to TRS-398 ranged from 0.982 to 1.010, while ratios compared to TG-51 varied between 0.985 and 1.021. The average absorbed dose to water using NTRS–398 and NTG–51 ranged from 0.984-0.996 cGy/MU and 0.986-0.997 cGy/MU, respectively. The results were also compared with previous studies to demonstrate that the modified calibration methods closely align with the established protocols, with discrepancies within the IAEA’s ±2% tolerance threshold.
Conclusions
The study highlights the importance of cross-calibration in ensuring the accuracy and reliability of modified electron beam calibration methods. These findings suggest that the modified approaches can serve as effective alternatives to traditional protocols, potentially enhancing dosimetric precision and flexibility in clinical radiotherapy settings.