PET kinetic modeling without the need of input curve

In PET imaging, application of kinetic modeling always requires an input curve (IC) together with the PET data. The IC can be obtained by means of external blood sampling or, in the case of cardiac studies, by means of region-of-interest (ROI) drawn on the blood pool. It is, however, very unsuitable to withdraw and to analyse blood samples, and in small animals, this operation becomes impossible, while ICs determined from ROIs are generally contaminated by emissions from neighboring sites, or they are underestimated because of partial volume effect. In this work we report a new method to extract kinetic parameters from dynamic PET studies without a priori knowledge of the IC. The method is applied in FDG human-brain and in cardiac-rat perfusion studies with ¹³N-ammonia and ¹¹C-acetate. The tissue blood volume (TBV), usually fitted together with the rate constants, is extracted simultaneously with the tissue time activity curves for cardiac studies, while for brain gray matter TBV is known to be about 4% to 7%. The shape of IC is obtained by means of factor analysis from an ROI drawn around a cardiac tissue or a brain artery. The results show a good correlation (p<0.05) between cerebral metabolic rate of glucose, myocardial blood flow and oxygen consumption obtained with the new method in comparison to the usual method. In conclusion, it is possible to apply kinetic modeling without any blood sampling, which significantly simplifies PET acquisition and data analysis.