Enhancement of computed tomographic scanner based digital radiographic images

Scanned digital radiographs are one of the imaging facilities available on the EMI 7070 scanner. The images offered by the system were found to be clinically poor and the reason for this was that the round shape of the patient was forming the major component of the image. Two empirical methods to account effectively for patient shape have been investigated and are now in clinical use. The first method assumes that the patient shape is approximated to a second-order polynomial of the picture element position. For each line of the image a second-order polynomial function is fitted to the image data, then removed from the image data. The second method involves using the existing CT wedge as an average compensation wedge to remove the majority of the effect of the patient shape. The relative merits and clinical application of both techniques are discussed.