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-60based plastic scintillating detector (PSD). The Gd2O2S:Tb detector was then used to measure 220 kVp therapy beam profiles of 10 x 10 and 5 x 5 mm 2 fields. Beam profiles using the ZnS-based phosphor were also obtained and compared to investigate the performance of a lower density inorganic scintillator. 10 x 10 and 5 x 5 mm 2 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 x 10 and 5 x 5 mm 2 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.

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In the field of radiation therapy, optical fiber dosimeters (OFD) offer several advantages over conventional dosimeters for real-time dosimetry. Their sensing tips can be small in size affording them the potential for high spatial resolution capabilities. In previous work, a novel inorganic scintillating detector (ISD) based on Gadolinium Oxysulfide (gadox) was fabricated for in vivo optical fiber dosimetry of conformal small animal irradiators. The performance of this detector was evaluated for 40 and 80 kVp imaging beams and the 220 kVp therapy beam of the Small Animal Research Platform (SARRP). The purpose of this study was to use a validated Monte Carlo (MC) model of the SARRP to investigate (i) dose absorption in the ISD active volume and (ii) dose perturbation by the inorganic scintillating phosphor volume. A comparison was also drawn between the perturbation by the gadox phosphor and a ZnS-based phosphor. The gadox-based detector was seen to cause high levels of dose perturbation in the radiation field, leaving significant dose shadows in the irradiated media. The use of ZnS:Ag phosphor reduces the perturbations with just over half as much dose absorbed relative to the gadox phosphor. An optimized ISD design which utilizes the higher light yield of the less perturbing ZnS:Ag phosphor to allow for a smaller high-density active volume, and significantly mitigating kV dose perturbation, has been proposed.

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