Image reconstruction from data over two orthogonal arcs of limited-angular ranges.

Abstract

Computed tomography (CT) scanning over limited-angular ranges (LARs) is of practical interest in possible reduction of imaging dose and time and in design of nonstandard scans. This work aims to investigate image reconstruction for two nonoverlapping arcs of LARs, and to demonstrate that they may allow more accurate image reconstruction than may a single arc ofLAR. We consider a configuration with two nonoverlapping arcs of LARs and , whose centers are separated by , and refer to it as a two-orthogonal-arc configuration. Data are generated from a chest phantom with two-orthogonal-arc configurations over total angular coverage ranging from to , and images are reconstructed subsequently by use of the directional-total-variation (DTV) algorithm. For comparison, we also consider image reconstruction for a single-arc configuration of angular range . Quantitative metrics such as the normalized root-mean-square-error (nRMSE) are used for evaluation of image reconstructionaccuracy. Visual inspection and quantitative analysis of images reconstructed reveal that a two-orthogonal-arc configuration generally yields more accurate image reconstruction than does its single-arc counterpart. As total angular range increases, the DTV algorithm yields image reconstruction with enhanced accuracy, as expected. Also, if remains constant, the two-orthogonal-arc configuration with generally leads to image reconstruction more accurate than those of two-orthogonal-arc configurations with , as the nRMSE of the former can be lower than that of the latter for up to more than one order ofmagnitude. Appropriately designed two-orthogonal-arc configurations may be exploited for improving image-reconstruction accuracy in CT imaging with reduced angular coverage. This study may yield insights into the design of innovative CT scans for lowering scan time and radiation dose, and/or for avoiding scan collision in, for example, C-armCT.