[Function scintigraphy: a uniform method for quantifying organ metabolism and function].

Abstract

Functional scintigraphy is a quantitative method with which metabolic parameters of an organ can be determined by measuring the time activity course of a radioactive tracer in tissue. Their quantitative value is, however, limited by inherent sources of error, e.g. the absorption of radiation in the organ or overlapping of fore- and background activities. Hitherto, existing procedures for calculation of metabolic parameters are based more on given technical possibilities than on common theoretical foundations. They are notable for their variety in methodical approach, frequently being of empirical character. Quantitative results from different institutes and hospitals can therefore rarely be compared. The present work describes a methodical approach to obtain comparable methods in nuclear medicine, by including the pharmacokinetics of a tracer in blood. This leads to the compartment analysis (deterministic) or to a stochastic (non-deterministic) description of the kinetics in an organ. The stochastic description requires the calculation of the linear response function from a convolution integral. By means of functional analytical methods a mathematical procedure has been developed which for the first time permits the calculation of the linear response function in each pixel and at any time of the study. Easily readable functional images show how relevant parameters can be calculated from the linear response function. Due to its independence on any model, the linear response function enables furthermore a regional investigation of existing or new compartment models of tracer kinetics in the organ concerned.