Parametric image of myocardial blood flow generated from dynamic H215O PET using factor analysis and cluster analysis

Algorithm-based parametric imaging of myocardial blood flow (MBF), as measured by H215O PET, has been the goal of many research efforts. A method for generating parametric images of regional MBF by factor and cluster analysis on H215O dynamic myocardial PET was validated by its comparison with gold-standard MBF values determined invasively using radiolabelled microspheres. Right and left ventricular blood pool activities and their factor images were obtained by the application of factor analysis to dynamic frames. By subtraction of the factor images multiplied by their corresponding values on the factors from the original dynamic images for each frame, pure tissue dynamic images were obtained, from which arterial blood activities were excluded. Cluster analysis that averaged pixels having time-activity curves with the same shape was applied to pure tissue images to generate parametric MBF images. The usefulness of this method for quantifying regional MBF was evaluated using canine experiment data. H215O PET scans and microsphere studies were performed on seven dogs at rest and after pharmacological stress. The image qualities and the contrast of parametric images obtained using the proposed method were significantly improved over either the tissue factor images or the parametric images obtained using a conventional method. Regional MBFs obtained using the proposed method correlated well with those obtained by the region of interest method (r=0.94) and by the microsphere technique (r=0.90). A non-invasive method is presented for generating parametric images of MBF from H215O PET, using factor and cluster analysis.