Dose reduction in small animal imaging using a modified phosphor screen

494 Objectives Dose reduction is a key area of interest for preclinical longitudinal studies. Through hardware adaptation, it is possible to achieve significant dose savings with minimal compromises in resolution. This work seeks to characterize the dose savings that result by reassessing the phosphor screen used in microCT. Methods The phosphor screens provided on many small animal imaging systems are designed to acquire data at high resolution at the cost of higher dose. A thicker phosphor screen was developed to fit into an existing commercial imaging system. This adaptation provides improved sensitivity with slight degradations in resolution (~2x). Dose reduction was assessed using 30 wild type mice (15 standard, 15 low dose) imaged with 2 dosimeters surgically implanted with 1 located at the base of the neck and the other in the abdomen. CT protocols were created using a 360 degree acquisition with 1 projection per degree of rotation for standard and low dose scans. The standard protocol used X-ray tube settings of 80 kVp @ 0.5 mA with a 225 ms exposure time while the low dose protocol used settings of 80 kVp @ 0.2 mA with a 50 ms exposure time with noise characteristics matched between protocols. Results Significant dose savings are seen with the adapted detector. Dose reduction averaged >14x for the abdomen and >13.5x for skin. The average dose in the abdomen was reduced from 13.8 cGy to 0.97 cGy and from 15.9 cGy to 1.2 cGy for skin. Conclusions Significant dose savings can be realized with minor modification to the microCT detector. Previous studies (Osborne, et. al.) have shown that protocol optimization can reduce dose by > 2x. Additional modifications to CT hardware can yield an additional 12x-14x reduction in dose. Combining both optimizations can lead to dose savings of > 20x from typical scan protocols. Research Support Dosimeters for the study provided by Siemens Medical Solutions, USA