AUTOMATIC REORIENTATION OF 3-DIMENSIONAL, TRANSAXIAL MYOCARDIAL PERFUSION SPECT IMAGES

We developed a completely automatic technique to reorient transaxial i mages into short-axis (oblique) myocardial perfusion SPECT images. Met hods: The algorithm starts by isolating (segmenting) the left ventricl e (LV) myocardium using a combination of iterative clusterification an d rule-based location/size/ shape criteria. The three-dimensional, mid -myocardial LV surface is initially estimated as the locus of the tril inearly interpolated maxima for the count profiles originating from th e center of mass of the segmented LV. The final mid-myocardial surface is obtained by iteratively applying this process, incorporating addit ional constraints of shape and texture and using the nonsegmented, non thresholded transaxial image to obtain information on hypoperfused are as of the myocardium. it is then fitted to an ellipsoid, of which the major axis is assumed to represent the long axis of the LV, and the th ree-dimensional image volume is resliced perpendicularly to it. Result s: The algorithm was retrospectively applied to 400 dual-isotope studi es (200 rest Tl-201, 200 stress Tc-99m-sestamibi) from 200 consecutive patients. Segmentation was successful in 394/400 (98.5%) of the patie nts. The reproducibility of computer-based reorientation was perfect a nd significantly better than either intraobserver or interobserver rep roducibility. Conclusion: Automatic reorientation offers the potential for consistently faster and more accurate image processing and analys is and is an important step towards totally operator-less management o f myocardial perfusion SPECT data.