High-resolution CT reconstruction from Zoom-In Partial Scans (ZIPS) with simultaneous estimation of inter-scan ROI motion

The Zoom-In Partial Scans (ZIPS) method is a recently introduced high-resolution CT technique that utilizes the high geometric magnification in off-center regions in the CT scanner's field-of-view to boost the intrinsic spatial resolution of existing clinical multi-slice CT. ZIPS performs two off-center partial high-resolution scans of a region of interest (ROI), then an image reconstruction algorithm merges the partial scan data to produce a final high-resolution reconstructed image. In this study, we illustrate the feasibility of ZIPS image reconstruction with simultaneous estimation of inter-scan rigid ROI motion between the two partial scans. A total-variation and an entropy-based image alignment loss function was introduced for registration of the ROI between the two partial scans. Optional denoising filters were also introduced to stabilize the image alignment loss function. The feasibility of the ZIPS reconstruction framework is evaluated in a Catsim simulation environment. Results show that the proposed algorithmic compensation of ROI motion produced images visually indistinguishable from the images reconstructed with the ground truth positions of the ROI. The residual errors of the estimated ROI positions were no greater than 0.12 mm in x- and y- translation and 0.26 degree in rotation. Up to twofold improvement in the modulation transfer function (MTF) was achieved by ZIPS CT relative to a conventional centered scan.