Automatic selection of transaxial axis for reorientation of myocardial SPECT tomograms

Reorientation of transaxial SPECT myocardial tomograms into short and vertical long axis tomograms currently requires manual selection of the transaxial reference plane and manual determination of the left ventricle's long axis orientation in that plane. To reduce the time required for this procedure and promote objectivity, an algorithm was developed to automatically determine these parameters, using an approach that models the transaxial section of the myocardium as an ellipse. Automatically determined values for the reference plane and the long axis orientation in 14 normal and 11 abnormal patients in dual isotope, Tl-201 rest and Tc-Sestamibi stress, were compared with those obtained manually, with good correlation (r=0.91, p<0.001 for the axis orientation). The algorithm may eventually allow completely automatic reorientation of myocardial SPECT studies, thereby reducing operator labor and subjectivity