Compensation methods for head motion detected during PET scans

We describe two methods to correct for motion artifacts in head scans in positron emission tomography. The methods are based on 6D motion data that have to be acquired simultaneously during scanning. The data are supposed to represent the rotational and translational deviations of the head as a function of the motion measurement cycle, with respect to the initial head position. The first compensation method is a re-binning procedure by which the lines of response are geometrically transformed according to the current values of the motion data, assuming a cylindrical scanner geometry. An approximation of the re-binning transformations by use of large look-up tables, having the potential of on-line event processing, is presented. The second method describes post-processing of the reconstructed images by unconstrained or constrained deconvolution of the image or image segments with kernels that are generated from the motion data. We use motion data that were acquired with a volunteer in supine position to demonstrate the effects of the compensation methods