Kinetic analysis

With the aid of positron emission tomography the concentration of radioactively labeled ligands can be measured as a function of time in small parts of the human body in vivo. The use of short lived isotopes enables repeated studies to be performed on the same subject within reasonable time. A basic tool in the analysis of such data is a tracer kinetic model which relates the time course of the radioligand in plasma to the time course of the radioligand in the tissue. The model takes into account transport between the blood and the tissue, specific binding and release from the receptors, and non-specific binding. From a fit of the model to the measured time course of the radioligand, the receptor density, the association rate constant, and the dissociation rate can be determined in small volume elements of the tissue. (Author)