Because the use of factor analysis has been proposed for extracting pure physiologic temporal or spatial information from dynamic nuclear medicine images, factor analysis should be capable of robustly estimating regional myocardial blood flow (rMBF) using H2(15)O PET without additional C15O PET, which is a cumbersome procedure for patients. Therefore, we measured rMBF using time-activity curves (TACs) obtained from factor analysis of dynamic myocardial H2(15)O PET images without the aid of C15O PET.
Methods: H2(15)O PET of six healthy dogs at rest and during stress was performed simultaneously with microsphere studies using 85Sr, 46Sc, and 113SN: We performed factor analysis in two steps after reorienting and masking the images to include only the cardiac region. The first step discriminated each factor in the spatial distribution and acquired the input functions, and the second step extracted regional-tissue TACS: Image-derived input functions obtained by factor analysis were compared with those obtained by the sampling method. rMBF calculated using a compartmental model with tissue TACs from the second step of the factor analysis was compared with rMBF measured by microsphere studies.
Results: Factor analysis was successful for all the dynamic H2(15)O PET images. The input functions obtained by factor analysis were nearly equal to those obtained by arterial blood sampling, except for the expected delay. The correlation between rMBF obtained by factor analysis and rMBF obtained by microsphere studies was good (r = 0.95). The correlation between rMBF obtained by the region-of-interest method and rMBF obtained by microsphere studies was also good (r = 0.93).
Conclusion: rMBF can be measured robustly by factor analysis using dynamic myocardial H2(15)O PET images without additional C15O blood-pool PET.