Sparse-view image reconstruction from gated cardiac data

In recent years, combined SPECT/CBCT systems have been developed and become commercially available for yielding spatially registered SPECT and CT images. The CBCT unit of the Philips SPECT/CBCT system (BrightView XCT) adopts a flat-panel detector for detecting X-rays. Because of heart motion and relatively slow data acquisition speed of the CBCT unit, the reconstruction of a beating heart is challenging for CBCT. Gating is often used in cardiac imaging for acquiring CBCT projection data of the heart. In order to acquire projection data of a certain phase over 360 degree, multiple turns of projection data of the heart have to be acquired, after which the data are sorted to form subsets for different phases. For cardiac data within one source rotation, projection data for each phase are sparsely and non-uniformly distributed over the scanning angular range. In this work, we investigate image reconstruction for different heart phases from both simulation and patient cardiac data sets within one source rotation. The reconstruction task is formulated as a constrained minimization of image total variation (TV) problem, and an ASD-POCS algorithm is used for solving the constrained TV-minimization problem. The approach proposed to image reconstruction can potentially reduce scanning time and imaging dose to the patient. More important for cardiac imaging, this approach may reduce artifacts caused by heart motion. For the cases studied, our results suggest that images of potential practical utility can be reconstructed from both simulation and patient data within a single phase.