Initial evaluation of the performance of novel inorganic scintillating detectors for small animal irradiation dosimetry

The purpose of this study was to design and evaluate the performance of four novel inorganic scintillating detectors (ISDs) on the Small Animal Radiation Research Platform (SARRP). Relative scintillator output, measurement repeatability, setup uncertainty, linearity with dose rate, and signal reproducibility over time were investigated. The Gd₂O₂S:Tb detector had the highest relative signal output, generating up to 219 times more charge than a previously characterized BCF-60-based plastic scintillating detector (PSD). The Gd₂O₂S:Tb detector was then used to measure 220 kVp therapy beam profiles of 10 × 10 and 5 × 5 mm² fields. Beam profiles using the ZnS-based phosphor were also obtained and compared to investigate the performance of a lower density inorganic scintillator. 10 × 10 and 5 × 5 mm² therapy beam profile measurements made with the Gd₂O₂S:Tb and BCF-60 detectors differed, on average, by 1.1% and 1.9%, respectively. The ZnS:Ag measurements differed, on average, by 2.5% and 6% relative to BCF-60 measurements of the 10 × 10 and 5 × 5 mm² beam profiles, respectively. MicroCT imaging of the detector volumes was also performed, revealing poor packing of the ZnS:Ag crystalline phosphor in the deepest region of the cylindrical cavity. The Gd₂O₂S:Tb detector, in particular, has proven to be a promising candidate for real-time dosimetry of small fields in small animal irradiators, primarily because of the very large signal intensities observed, along with good repeatability, dose rate linearity, reproducibility and agreement with beam profile measurements made with a previously validated detector.