Weighted backprojection implemented with a non-uniform attenuation map for improved SPECT quantitation

A method is developed to improve quantitation in single-photon-emission computed tomography (SPECT) imaging by using an attenuation compensation method that includes the correct nonuniform attenuation spatial distribution (i.e. map). The method is based on the technique of weighted back projection, previously developed for uniform attenuation. It is tested by imaging a nonuniform phantom, reconstructing it with the known attenuation map, and quantitatively comparing the resultant image with the known activity distribution. Reconstructed image profiles are dramatically improved in comparison to reconstructions without compensation or with an assumed uniform attenuation map. Contrast measurements further quantify the improvement. Line-spread-function distortions seen previously in nonuniform geometries are essentially eliminated by the method, making it appropriate for these geometries if the nonuniform map can be determined. Some additional image distortions introduced by the compensation method are noted that will require further study.<>