Dosimetric analysis of true beam linear accelerators and assessment of dosimetry of photon beams for various treatment parameters

The True beam linear accelerator is a state-of-the-art device widely used in cancer treatment for its ability to deliver flattening-filter-free (FFF) and flattened photon beams. Despite its clinical significance, detailed information on its dosimetric characteristics remains limited. This study systematically evaluated dosimetric parameters for photon beam energies of 6 MV, 6 MV FFF, and 15 MV using high-resolution diode detectors and ion chambers. Measurements were conducted at a source-to-surface distance of 100 cm for field sizes ranging from 10 × 10 cm² to 40 × 40 cm² and depths of D_max, 5 cm, 10 cm, 20 cm, and 30 cm in water. Key metrics, including percentage depth doses (PDDs) and beam profiles, were analyzed to assess the effect of beam energy, field size, and depth on dosimetry. Comparisons of measured data from NORI Cancer Hospital and Shaukat Khanum Memorial Hospital demonstrated consistent and accurate performance across systems. These findings provide valuable insights into the dosimetric behavior of TrueBeam accelerators, contributing to the optimization of treatment protocols and ensuring improved patient outcomes.