Evaluating the Transmission Type Reference Chamber for Small Field Dosimetry

To assess the efficacy of a transmission-type parallel plane reference chamber (T-REF) for small-field percentage depth dose (PDD) measurements using two high-resolution detectors. The study utilizes microSilicon and microDiamond detectors for small-field measurements, both with and without a T-REF reference chamber. TrueBeam linear accelerator provides various photon energies (6X, 6XFFF, 10X, 10XFFF) for depth dose measurements. A sun-nuclear 3D water tank is used to measure the PDD up to a depth of 15 cm. Analysis of the data includes a 1D gamma passing rate calculated using an in-house MATLAB program. The study compares the PDD measurements obtained with and without the T-REF. The T-REF exhibits negligible beam perturbations across different field sizes and energies. The overall maximum mean PDD differences are 0.31 ± 0.16% for microSilicon and 0.33 ± 0.17% for microdiamond. The overall mean 1D gamma passing rate is 99.6 ± 0.2%. This study demonstrates that the T-REF is a reliable and effective reference detector for small-field radiation dosimetry.