Feasibility study of using epitaxial silicon diodes for clinical electron and photon beams dosimetry

In this work the feasibility of using epitaxial (EPI) silicon diodes for clinical dosimetry was studied with a Siemens Primus Linear Accelerator from Sírio-Libanês Hospital. Three samples of EPI diodes were investigated, concerning the influence of pre-irradiation on their response as on-line clinical photon and electron beam dosimeter. All measurements were performed with the diodes unbiased, operating in the direct current mode and inserted into a PMMA phantom. The dynamic current responses of the diodes under irradiation with electron beams in the energy range of 6 MeV-21 MeV and photon beams of the 6 and 18 MV were measured at different dose-rates. The dose-response curves of the diodes are quite linear in the range of zero up to 29.54 kGy for electrons and evaluated from 63 cGy up to 370 cGy for photon beams. The percentage depth dose profile (PDD) and transversal dose profile (TDP) for both electron and photon beams were also measured in PMMA with the EPI diodes. The results were in excellent agreement with those calculated with Monte Carlo code using the Oncentra MasterPlan® Treatment Planning System (TPS). The TDP was also evaluated with a commercialized array of 2D pixel ionization chambers MatriXX from IBA Dosimetry®.