MOTION DETECTION IN TRIPLE SCAN SPECT IMAGING

An algorithm to automatically detect and eliminate motion in projectio n data from triple scan SPECT imaging is proposed. The approach relies on a protocol where each head acquires projections over a full 360 de grees orbit rather than over the conventional 120 degrees partial orbi t. Projection acquisition times are reduced to one third of that used for the partial orbit protocol to keep comparable total scan times. Th is protocol permits the acquisition of three full sets of SPECT data w hich can be adequately combined in order to reconstitute a motion-free set of projection data. Cross-correlation of the projection sets as a function of angle are used to detect motion. Plateaus of high correla tion are estimated and matched in order to identify projections corres ponding to the same position of a subject throughout a study. The moti on correction algorithm was tested on experimental data obtained by ma nually moving a cardiac phantom at different times. In all cases, it w as possible to reconstitute the evolution of the motion during the stu dy. When no motion occurred during an interval equal to at least one t hird of the total acquisition time, high correlation plateaus were ide ntified and complete sets of consistent projections were assembled fro m the longest matching plateaus. When more frequent motion occurred, a n averaging of the three sets provided a means to improve the quality of the reconstructed slices compared to conventional imaging protocol.