The use of gamma functions in the calculation of organ perfusion functions for non-diffusible radioactive tracers

This paper introduces a method for quantification of mean organ perfusion by the impulse response function using the experimental time-activity curves for the organ of interest and its supplying artery. These are approximated by gamma functions and a general expression for the impulse response function is then derived. In any particular case, the impulse response function can be calculated simply by insertion of the numerical parameters. The procedure combines speed with freedom from random measurement errors. As an example of a clinical application, the impulse response function of healthy brain tissue is calculated and some clinically important parameters are tabulated.