Temporal behavior of peripheral organ distribution volume in mammillary systems. I. A new tool for in vivo tracer kinetic analysis.

In complex mammillary compartmental systems, the kinetic solutions for central and peripheral compartments are sums of too many exponentials to be accurately analyzed without very sophisticated mathematical tools. Our data show the peripheral organ distribution volume (PODV) kinetics to exhibit systematic time behavior depending on its mode of relation with plasma: linear increase for irreversible transfer, uniexponential function growing toward as asymptotic value for reversible transfer. Statistical analysis of our kinetic data shows that no other significant information can be extracted at least inside the time and statistical noise limits of our investigation. After intravenous injection of a diffusible tracer, the total activity in any region of interest (ROI) in the body is the sum of various components and, under certain conditions, PODV transformation easily allows their separation. Our simple non-compartmental model provides a useful tool for quantitative tracer analysis in nuclear medicine.