Modelling approach for separating blood time activity curves in positron emission tomographic studies

Abstract

A modelling approach is developed to generate the full time course of an injected radiotracer and its labelled metabolites in plasma blood, based on measurements of the total radioactivities in withdrawn plasma blood samples. A compartmental model is used to describe the conversion of an injected tracer to its metabolites in the body. The model equation is formulated with the total radioactivity concentration curve as the input function. The utility and characteristics of the approach in quantitative positron emission tomographic (PET) studies are shown with two examples. In the first example, using the tracer 6-(¹⁸F)fluoro-L-dopa (FDOPA), the approach is shown to derive the full time course of plasma FDOPA and its metabolites. In the second example of dynamic ¹⁵O oxygen PET, the approach is used to solve a deconvolution problem to give separated time-activity curves of ¹⁵O oxygen and ¹⁵O water in blood.