Length selection method of ramp filter to avoid corner errors of CT image
Zhiwei Qiao · Jisuanji gongcheng yu sheji · 2012
To avoid the inherent errors of the four corners of CT image,a better length selection method for the unit impulse response of the ramp filter is proposed.The theory of the usual length selection method is analyzed,which is doubled and subtracted by 1.The errors of the CT image reconstructed are described by using the method.The reason of the errors is analyzed and a correction method is proposed and a simulation experiment is made to verify it.The correction principle is that padding zeros symmetrically to the projection signal to make its length is 2N and selecting 22N-1 to be the filter's length and selecting 2N to be the filtered projection signal's length.The length of the unit impulse response of the ramp filter should be 22N-1 in the filtered back projection type algorithm when the length of the projection signal is N and the size of the reconstructed image is N×N.