An improved helical cone-beam CT image reconstruction

This paper describes a flexible new method for accurate cone-beam reconstruction with source position on a helical orbit, which is called hybrid filter method. The inversion formula employed by this hybrid filter method is based on first applying Hilbert and ramp transforms for a combination with a simple rotation angular derivative and a direct weight in the projection space and then backprojecting the filtered data. First, about the derivatives with respect to the coordinates on the detector panel have been avoided,which results in quality improvement and reduced artifacts. Second, the new algorithm still performs a 1D shift-invariant filtering to the modified data on the detector panel and the redundancy weight to the filtered data is applied after filtering. Third, the introduction of ramp filter can further promote image resolution than Hilbert filter.