Comparative analysis of dosimetric uncertainty using Gafchromic™ EBT4 and EBT3 films in radiochromic film dosimetry

Abstract

Advancements in radiotherapy dosimetry aim to enhance precision and accuracy, with Gafchromic™ EBT4 film emerging as a promising tool. However, its performance compared to EBT3 remains underexplored, necessitating a comprehensive analysis of dosimetric uncertainties. This study evaluates the efficacy of EBT4 in radiochromic dosimetry, comparing it to EBT3. Employing a 6 MV beam quality, absorbed doses ranging from 0 to 10 Gy were investigated using different measurement quantities and fitting functions. Gafchromic™ EBT3 and EBT4 films (8′′ × 10″) were irradiated in a water-equivalent phantom, with calibration doses delivered using a Varian Truebeam Stx linear accelerator. Two measurement quantities, pixel values (PV) and net change transmittance (netΔT), were analyzed, along with calibration functions including a rational function for PV and a logarithmic function for netΔT. Uncertainty analyses considered experimental, fitting, and calibration dose uncertainties. Dose-response curves for EBT3 and EBT4 films demonstrated robust fits, emphasizing the reliability of both. EBT4 consistently exhibited lower uncertainties, particularly below 2 Gy, showcasing superior precision in low-dose scenarios. The choice of response quantity and calibration function influenced results, with PV-rational function excelling for doses 2–10 Gy, and netΔT-logarithmic function showing enhanced precision in the 0–2 Gy range. The uncertainty analysis emphasized EBT4's superior performance, especially in low-dose ranges, with lower relative uncertainties and absolute errors, indicating enhanced reliability in dose measurements. The study underscores EBT4's potential to contribute to improved accuracy in various clinical scenarios. However, users should tailor the choice of response quantities and calibration functions to specific dose calibration ranges, suggesting a nuanced approach.