COMPENSATION METHODS FOR HEAD MOTION DETECTED DURING PET IMAGING

We describe two methods to correct for motion artifacts in head images obtained by positron emission tomography (PET), The methods are based on six-dimensional motion data of the head that have to be acquired s imultaneously during scanning, The data are supposed to represent the rotational and translational deviations of the head as a function of t ime, with respect to the initial head position, The first compensation method is a rebinning procedure by which the lines of response are ge ometrically transformed according to the current values of the motion data, assuming a cylindrical scanner geometry, An approximation of the rebinning transformations by use of large look-up tables, having the potential of on-line event processing, is presented, The second method comprises post-processing of the reconstructed images by unconstraine d or constrained deconvolution of the image or image segments with ker nels that are generated from the motion data, We use motion data that were acquired with a volunteer in supine position, immobilized by a th ermoplastic head holder, to demonstrate the effects of the compensatio n methods, Preliminary results obtained with test data indicate that t he methods have the potential to improve the resolution of Positron Em ission Tomography images in cases where significant head motion has oc curred, provided that the head position and orientation can be accurat ely measured.