Author: Mohamad Ahmad Alissa, Carson Brame, Damian Czarnecki, Olivier Evrard, Charbel A. Habib, Jeff Hildreth, Andy Murray, Andreas Schönfeld, Ann-Britt Schönfeld, David Towle, Gerd Wessing 👨🔬
Affiliation: CDT-West - Centrum für Diagnostik und Therapie, Radiologie Vechta, Technische Hochschule Mittelhessen, MyMichigan Health, Sun Nuclear Corp., Mirion Technologies 🌍
Purpose: To characterize the performance of novel shielded and unshielded silicon diode detectors in relative photon and electron beam dosimetry.
Methods: The novel shielded and unshielded silicon diode detectors were characterized experimentally in lateral beam profile and percent depth dose (PDD) profile measurements using motorized water phantoms at various linear accelerators with and without flattening filter. Nominal photon energies ranged from 4 MV to 25 MV and nominal electron energies from 6 to 22 MeV. The unshielded silicon diode was investigated in square photon fields from 0.4 to 10 cm and square electron fields from 6 to 25 cm. The shielded silicon diode was investigated in photon fields from 1 to 40 cm. PDDs were measured to a depth of 30 cm. A 1D gamma index analysis with a 0.5% dose difference, a 0.5 mm distance criterion and no low dose threshold was performed to compare the profile measurements against those of suitable reference detectors.
Detailed virtual models of the shielded and unshielded silicon detectors were generated in the EGSnrc code system to calculate corresponding PDDs and lateral beam profiles. A full linear accelerator head model was used to generate realistic high energy 6 MV photon fields with field sizes of 0.4 to 40 cm, and electron fields corresponding to those used for measurements.
Results: The gamma passing rate exceeded 90% for all measurements when comparing the new silicon diode detectors with the reference detectors. The measured dose profiles and PDDs also showed excellent agreement with Monte Carlo data.
Conclusion: This study demonstrated, both through measurements and Monte Carlo simulations, that the novel shielded and unshielded silicon diode detectors are suitable for relative dose measurements in photon and electron beams.