ADAPTIVE, SEGMENTED ATTENUATION CORRECTION FOR WHOLE-BODY PET IMAGING

A technique is presented for segmented attenuation correction in posit ron emission tomography (PET) based on the local thresholding techniqu e (LTS) described previously. To accommodate the substantially differe nt body sections encountered in whole-body PET, an adaptive thresholdi ng has been added to yield more uniform results throughout the body. B y evaluating the intensity distribution of a set of transverse transmi ssion images, the algorithm determines an optimal threshold for separa ting two or three different groups or classes of similar pixels. Inter class variance is maximized and intra-class errors are minimized. The algorithm also switches automatically between a three-class mode (back ground, lungs/air pockets, soft tissue) and a two-class mode (backgrou nd, soft tissue), thereby achieving more uniform segmentation where lu ng spaces and bowel air pockets are alternately present then absent fr om the volume of interest. The addition of adaptive thresholding virtu ally eliminates the need for operator intervention. The clinical imple mentation requires short-duration, count-limited, transmission images that would otherwise be too noisy for direct attenuation correction, E mission images corrected with adaptive LTS were shown to be equivalent , both quantitatively and qualitatively, to those corrected using conv entional measured attenuation correction.