A modified FDK with misaligned parameters of flat-panel detector in Cone-Beam CT

FDK reconstruction algorithm is the most widely used for Cone Beam CT imaging system due to its simplicity and fast implementation. However, if misalignments exist in the detector, the original FDK reconstruction algorithm will result in deteriorated reconstruction quality because of the wrong correspondence of the voxels from the object and the pixels from the projection. One way is to apply rotation-based interpolation for each projection, which not only will cause blurring of the details due to the effect of interpolation but also is very time-consuming. In back-projection based reconstruction, the key factor is to correctly relate the voxels from the object and the pixels from the projections. Based on this point of view, we propose a method that will correctly find the correspondence of the voxels and pixels. With this method, reconstruction result can be obtained with good accuracy if all the misaligned parameters of the detector are known. And also, detail information can be better preserved compared with the rotation-based interpolation method. In the validation period, a simulation program of Cone-Beam CT was developed. In this program, all misaligned parameters of detector are able to be set. And the simulated result proves that our method is efficient and feasible although it suffers a little deterioration, and can further be used in online calibration of CBCT.