Correcting organ motion artifacts in x-ray CT systems based on tracking ofmotion phase by the spatial overlap correlator. II. Experimental study

This paper presents the experimental part of an investigation on tracking a nd eliminating organ motion artifacts in x-ray CT cardiac applications with emphasis on imaging coronary calcification. The system methodology consist s of a software implementation of the spatial overlap correlator (SSOC) con cept in x-ray CT scanners to track the net amplitude and phase of organ mot ion during the CT data acquisition process. A coherent sinogram synthesis ( CSS) method is then used to identify the repeated phases of a periodic orga n motion from the information provided by the SSOC process and hence synthe size a new sinogram with no motion effects. Since the SSOC scheme is capabl e of tracking cardiac motion, it identifies also the projection points asso ciated with minimum amplitude cardiac motion effects. These points are used to identify a 180 degrees plus the fan angle sino,gram for image reconstru ction. This leads to a retrospective gating (RG) scheme that is based on th e output of the SSOC process. Performance comparison of the proposed method ology with the retrospective ECG gating using real data sets with phantoms and human patients provides a performance assessment of the merits of the p roposed methods. Real results demonstrate that the new methodology eliminat es the requirement for ECG gating. Moreover, the CSS and the new RG methods do not require breath holding and they can be implemented in x-ray CT scan ners to image coronary calcification and the heart's ventricles. (C) 2001 A merican Association of Physicists in Medicine.