Dosimetric assessment of radiation fields up to 5 × 5 cm2 and architectural optimization of a diode-based 3D Detector for radiotherapy

Abstract

An initial 3D electronic detector array prototype for radiotherapy, consisting of 2645 diodes (8.0 mm pitch), was modelled with Geant4 and MCNP6.2 Monte Carlo codes to simulate irradiations of 2×2, 3×3, 4×4, and 5×5 cm2 field sizes with a 6 MV photon beam. Comparisons with Treatment Planning Software (TPS) data revealed maximum percent depth dose (PDD) differences of 2.90% for MCNP6.2 and 1.74% for Geant4. However, spatial resolution limitations in the initial prototype caused dosimetric discrepancies in the high-gradient penumbra regions. Consequently, an optimized high-density prototype featuring variable spatial resolution (3.0 mm central pitch, 6.0 mm peripheral pitch) was developed. The results demonstrate that the new high-density architecture mitigates the spatial undersampling previously observed, ensuring a reliable volumetric dosimetric assessment of small radiation fields.