BPF-Type Reconstruction for Dual Helical Cone-Beam CT

In three dimensional (3D) imaging, the field of view (FOV) is a significant factor that defines the ability of the system. Due to the small flat detector, the size of the FOV is limited. It is known that the FOV can be enlarged by using a horizontally shifted detector and x-ray source, but the projection data are horizontally truncated at each view angle. We have developed a dual-helical cone-beam computed tomography (CT), in which the x-ray source and planar detector are shifted a given distance before two helical scans. This work presents another reconstruction algorithm for dual-helical cone-beam CT. The method utilizes the property that PI-line segment within the imaged object can be reconstructed if the data, on the PI-line segment, can be available. The method presented in this paper is an extension of backprojection filtration (BPF) algorithm for single helical cone-beam CT, and consists of a weight during the backprojection step. Computer simulation shows that the BPF-type algorithm for dual-helical scanning can obtain better quality images than other reconstruction method, despite the large pitch.