AUTOMATIC INPUT FUNCTION ESTIMATION FOR PHARMACOKINETIC MODELING

摘要

estimating parameters of a kinetic model from a series of tracer (radioactively labeled imaging agent) activity measurements (e.g. by positron emission tomography). Since the model describes a biological process its parameters have a direct functional interpretation (e.g. hypoxia for the tracer FMISO) that can be of diagonistic value. The measurements represent the activity distribution in time and space in the form of a 4D data set d(t, x,y,z), t=l,. . ,, T. The kinetic parameter estimation procedure (205) requires knowledge of the tracer input activity. This input activity can either be measured invasively or it can be estimated form the data in a preprocessing step. The estimation problem can be solved efficiently if the model and its input are described analytically. Typically parameterized functions (often sums of exponential terms) (204) are fitted to the averaged data over a region of interest (ROI) (e.g. an artery or the left ventricular blood pool) in order to obtain an analytical input representation. The input function representation (fimctional form) ( 204) and its initial parameter values (205) have to be selected / specified prior to the fitting procedure 206). The present invention thereby reduces the amount of manual interaction and operator dependence in the evaluation of dynamic procedures.