Z-range Extension of Volume Imaged with Clinical C-arm Computed Tomography from A Single Rotation Helical Cone-beam Scan

Abstract

In conventional computed tomography (CT) imaging, cone-beam (CB) projection data generated with a helical scanning trajectory (namely helical CB scan) are complete for an exact analytic reconstruction according to data sufficiency condition (DSC). As for clinical C-arm CT imaging, a helical CB scanning is intuitively useful for extending the z-range of volume to be imaged effectively, which is equivalent to the reduction of total dose delivered to patient as compared with conventional circular CB scanning. Nevertheless, this z-range extension of imaged volume is relatively limited, since at most a single rotation is available for clinical C-arm CT imaging. Meanwhile, only approximate CB-FBP reconstruction algorithm is feasible for this task by relaxing the requirement on the exactness of image reconstruction. It has been well known that, using the conventional helical CB-FBP reconstruction algorithm, the severe CB artifacts are observable, especially within the outer slices, while extending the z-range of imaged volume. To effectively suppress these CB artifacts within the outer slices, in this work a three-dimensional (3D) weighted helical CB-FBP reconstruction algorithm is proposed for specifically improving the image quality in the extended z-range. Using the digitalized patient data simulated by computer with the geometrical parameters of an actual C-arm CT imaging system, we conduct an initial study to investigate the performance of the proposed algorithm. The preliminary results show that the proposed algorithm does improve the image quality for clinical C-arm CT imaging with a single rotation helical CB scan.