Approaches to Region of Interest Tomography

Abstract

The objective of computed tomography is to obtain good quality images while keeping the dose to the patient as low as possible. Unfortunately, the interdependence of patient dose, contrast and spatial resolution puts limitations on the arbitrary variations of these parameters. In other words, one can not change one without affecting the others. In some clinical situations, reconstruction of the whole slice is not needed, especially when a disease is well localized from a previous study and a follow-up scan of the same area is required. If one could scan and reconstruct only the region of interest (ROI) one could increase the spatial resolution within the region of interest and reduce the dose in the outside region. However, it should be remembered that since the same dose-contrast-resolution relation mentioned earlier still applies, in order to improve the resolution within the ROI one would also have to increase the dose in that region. Thus the region of interest tomography techniques could involve a redistribution of the dose within the whole slice if one tries to improve the resolution within the ROI.