Modelling arterial input functions in positron emission tomography dynamic studies.

The quantification of dynamic positron emission tomography (PET) images often requires the invasive measures of the arterial plasma tracer concentration to be used as arterial input function (AIF). In several situations, a mathematical model is fit to the hematic data to obtain a continuous and noise-free description of the AIF. In common practice, the tri-exponential and Feng's models are generally adopted. Despite their general applicability, often these approximations of blood tracer activity do not properly describe the complex behavior of the AIF (e.g. different clearance rates of the tracers) as well as they do not account for the length of the radiotracer injection. Here we propose two models able to include the injection duration as additional information in the AIF modeling and we compare their performances in eight different datasets acquired from different PET facilities.