Three-dimensionally reconstructed images are not ideal due to blur or smear that is caused by various sources in an X-ray CT scanner. In order to substantially minimize the blur in the three-dimensionally reconstructed image, a known PSF is weighed according to a combination of predetermined parameters. The parameters include two types of information. One group of the parameters is related to device characteristics of the scanner device while the other is related to the scanning conditions of a particular scan. The improvement is performed in any combination of the X, Y and Z directions. The improved PSF's are used to de-convolute the three-dimensionally reconstructed CT image. As a result, the blur and smear are substantially removed from the three-dimensionally reconstructed image data for good visualization as well as accurate physical measurements in the scanned image. The improved techniques according to the current invention are applicable to two-dimensional image data.