A Rebinning-type Backprojection-Filtration Algorithm for Image Reconstruction in Helical Cone-beam CT

We developed an exact algorithm for image reconstruction in helical cone-beam CT based upon the backprojection-filtration (BPF) algorithm. This algorithm has the same backprojection-filtration form while reconstructing images in a rebinning geometry. It first converts the cone-beam data into fan-parallel-beam data, and then backprojects the data derivatives onto the PI-line segments, finally performs a finite inverse Hilbert transform on each PI-line segment to obtain the reconstruction. It retains the properties of the original BPF algorithm in that it also requires minimum data and can reconstruct ROI images from truncated data. More importantly, due to the elimination of the weighting factor before the backprojection, it improves the computational efficiency and the noise and resolution properties in reconstructed images.