Detection of motion in hybrid PET/SPECT imaging based on the correlation of partial sinograms

This paper describes a motion detection method specific to hybrid positron emission tomography/single photon emission computed tomography systems. The method relies on temporal fractionation of the acquisition into three data sets followed by an algorithm based on the cross correlation (CC) of parti al sinograms from successive sets at different rotations of the camera. Spa tial inconsistencies due to motion are detected by decreases in the CC betw een two sets. This permits to separate data into premotion and postmotion s ets of consistent data that are reconstructed independently then registered and summed. Rigid motions greater than 1-cm translation or 10 degrees rota tion were detected with this method from experimental data obtained by manu ally moving phantoms made of radioactive spheres as well as from a patient lung study corrupted by artificial motion. The different motion studies sho wed that the image contrast does not seem to be a limiting factor and that the motion is best detected when the gantry is parallel to the direction of motion. The registration and fusion of the reconstructed premotion and pos tmotion sets lead in all cases to a reduction of the motion artifacts and a n increase in signal-to-noise ratio.