Using scout images to reduce metal artifacts in CT with application to revision total hip surgery

Abstract

X-ray CT images of objects containing metal are often corrupted by 'blooming' and streaking artifacts that radiate from the regions of the image where the metal is present. The best strategy for reducing these artifacts is to modify the noisy projection data before reconstructing the image. Unfortunately this approach does not lead to a very practical solution, since it assumes that one has access to the unencoded projection data. In reality, these data are virtually impossible to get, even for isolated research studies, let alone for routine clinical use. Our goal is to produce a practical, clinically useful system of reducing metal artifacts in real patient CT scans on a regular basis. So we need a method that is not dependent on sinogram data. However, it is extremely difficult, if not impossible, to reduce metal artifacts using just the information than exists in the noisy CT image itself. As we show, crucial image details may be completely erased by the artifacts. Therefore we have developed a new approach for suppressing these reconstruction artifacts by using scout images. We have applied this method successfully to real CT data.