Circulation model for functional radionuclide diagnosis with organotropic radiopharmaceuticals

Theoretical analysis is given of the potentialities of employing the mathematical apparatus of circulation models widely used in radionuclide studies of hemodynamics for processing the results of dynamic scintigraphy with organotropic radiopharmaceuticals (RP) diffusing from the vascular bed. The circulation models of the convolution and Zirler integral level are considered. The correctness of their identification algorithms is analyzed with estimation (as a diagnostic parameter) of the mean time of RP transit through the examined organ. A new circulation model describing the process of RB retention in this organ is proposed. Direct use of the convolution and Zirler models for our purpose involves methodological and technological difficulties with are impossible to overcome in principle. The model of RP retention helps overcome these difficulties and permits a simple and rapid estimation of the mean time of RP retention from the first integral moments of the recorded clearance and organ gamma-chronograms for a hypothetical pulsed injection of RP directly at the entry of the organ. Using the first and second moments of the same gamma -chronograms it is possible to estimate the mean time of RP transit through the examined organ as well. 9 refs