Task–based Optimization of In–Vivo Micro–CT Scan Protocols using Energy Integrating and Photon Counting Detectors

Optimizing imaging protocols in small animal micro-CT for dose minimization is important, especially in longitudinal studies. To find the optimal number of projection angles over a full 360 rotation given a fixed dose as constraint, the tradeoff to be found is between elevated image noise for projections approaching the quantum limit and streak artifacts due to sparse angular sampling. Scan protocols are therefore simulated by forward projections of a quasi-noise-free mouse volume using different numbers ofview angles and addition of an appropriate amount of noise to preserve a constant overall dose. Energy integrating (EI) and photon counting (PC) detectors are considered and compared. Evaluation is based on the performance of imaging tasks: The left ventricular volume is determined using the segmentation algorithm by Otsu and compared to a ground truth. A model observer with nonprewhitening matched filter template is used for the detection of a small lesion and its performance is evaluated to confirm the findings. Results for EI detectors indicate an optimal number of 180 view angles over 360. The absence of electronic noise in the case of a PC detector leads to increasing image quality for an increasing number of view angles. The findings will allow for designing and improving future in-vivo imaging protocols for both detector types.