Monte Carlo simulations of a new 3D electronic detector for radiotherapy quality assurance

Objective. Evaluate the dosimetric performance of a novel three-dimensional (3D) electronic detector array for radiotherapy quality assurance using Monte Carlo simulations. Approach. Monte Carlo simulations were performed with Geant4 and MCNP6.2. A detailed detector model (MCModel) was implemented consisting of a 50 × 50 × 50 cm3 PMMA phantom with 20 imbedded active matrices (AMs) at strategic depths, 1,169 pixels per AM, and 23,380 pixels for the entire detector. A pixel comprises a diode, capacitor, and MOSFET, where the diode elements provide a 42 × 42 cm2 sensitive area within an AM. Photon beam energy spectra of 6 MV and 10 MV, respectively, of a Varian radiotherapy linear accelerator (linac) were used in the simulations. Dosimetric data consisting of percent depth-doses (PDDs) and cross- / in-plane profiles for field sizes of 5 × 5 cm2 through 40 × 40 cm2 were simulated for the MCModel, and a homogeneous PMMA phantom (MCPMMA) of similar dimensions. Main results. MCModel versus MCPMMA PDD data difference for Geant4 and MCNP6 were within 3.44% and 3.83%, while profiles (cross- / in-plane) were within 5.54% and 5.68%, for all field sizes and energies. Significance. These results suggest that a 3D electronic detector could provide suitable dosimetric data for radiotherapy QA, and if realized, it could likely provide it in less time than current methods.