Compensation for head movement in 3D PET

Motion correction of neurological 3D PET data by the multiple acquisition frame (MAF) method presents some challenges that do not apply to the same extent in 2D. One of the most significant is that 3D PET scans have a much higher scatter component, and the inclusion of valid correction for scatter is essential for accurate quantification. This paper describes a technique for motion correction of PET data acquired in 3D that uses information provided by an optical motion tracking system, and includes corrections for temporal variations in attenuation and scatter. The technique is demonstrated in 3D dynamic and list mode scans of a Hoffman 3D brain phantom performed on a Siemens/CTI ECAT EXACT HR+ scanner in which multiple arbitrary movements were applied to the phantom during data acquisition. The MAF method cannot correct for motion that occurs during the acquisition of an individual frame. The feasibility of avoiding this limitation by acquiring the data in list mode, and re-framing into a dynamic scan in which a new frame is commenced whenever significant motion occurs was investigated. Both approaches provided a major reduction in motion distortion when compared to a conventional reconstruction without motion correction. It appears that effective motion compensation is achievable in 3D neurological PET.