Characterization of Inorganic Scintillator Detectors for Dosimetry in Image-Guided Small Animal Radiotherapy Platforms

SIMPLE SUMMARY: Dosimetry for preclinical radiotherapy research requires the standardization of dose validation and quality assurance procedures. Except for dose reference measurements, dosimetric quality control of image-guided small animal irradiation platforms is mostly performed with passive detectors (alanine and gafchromic films). This results in the inconvenient task of lengthy post-processing. In this paper, we carried out a dosimetric characterization of an active detection system based on inorganic scintillators in medium-energy X-rays. We implemented a cross-calibration framework based on international dosimetric protocols to assess the energy dependence of the detector. Additionally, we determined relative output factors for very small fields and compared them to other measurement systems (EBT3 film and CMOS sensor). We demonstrated the suitability of the inorganic scintillation system for the development of phantom-based end-to-end tests for dose verification in newly implemented preclinical radiotherapy irradiation techniques. ABSTRACT: The purpose of the study was to characterize a detection system based on inorganic scintillators and determine its suitability for dosimetry in preclinical radiation research. Dose rate, linearity, and repeatability of the response (among others) were assessed for medium-energy X-ray beam qualities. The response’s variation with temperature and beam angle incidence was also evaluated. Absorbed dose quality-dependent calibration coefficients, based on a cross-calibration against air kerma secondary standard ionization chambers, were determined. Relative output factors (ROF) for small, collimated fields (≤10 mm × 10 mm) were measured and compared with Gafchromic film and to a CMOS imaging sensor. Independently of the beam quality, the scintillator signal repeatability was adequate and linear with dose. Compared with EBT3 films and CMOS, ROF was within 5% (except for smaller circular fields). We demonstrated that when the detector is cross-calibrated in the user’s beam, it is a useful tool for dosimetry in medium-energy X-rays with small fields delivered by Image-Guided Small Animal Radiotherapy Platforms. It supports the development of procedures for independent “live” dose verification of complex preclinical radiotherapy plans with the possibility to insert the detectors in phantoms.