Validation of an alanine-based postal dosimetry audit system for radiotherapy quality assurance

Abstract

In radiotherapy practice, external dosimetry audits represent a valuable tool for identifying systematic errors, improving the quality and safety of treatments, and ensuring consistency in clinical dosimetry procedures. Despite their proven importance, many radiotherapy centers are still unable to access these audits, especially in resource-constrained settings. With this in mind, the present study aimed to validate an independent postal dosimetry audit service for photon radiotherapy, currently being developed at the Department of Nuclear Energy of Federal University of Pernambuco (DEN/UFPE), using alanine-EPR dosimeters. The proposed system features a structure designed to support six dosimeter holders simultaneously, allowing the evaluation of central-axis and off-axis dose, as well as quality index, flatness and symmetry of photon beams generated by linear accelerators. The system's performance was assessed by comparing measurements from the DEN/UFPE QA setup with results from the TLD-based dosimetry audit program of the Brazilian National Cancer Institute (PQRT/INCA) and with reference data obtained using a PTW 30013 ionization chamber under identical irradiation conditions. The interlaboratory comparison results demonstrated agreement among the systems, with dose deviations relative to the ionization chamber not exceeding 2.0% for the DEN/UFPE system and 1.9% for the PQRT/INCA system. Therefore, these findings provide robust evidence supporting the reliability, accuracy, and overall effectiveness of the proposed alanine-based postal dosimetry audit system, confirming its suitability for clinical implementation.