Graphical analysis of PET data applied to reversible and irreversible tracers

The differential equations of compartmental analysis form the basis of the models describing the uptake of tracers used in imaging studies. Graphical analyses convert the model equations into linear plots, the slopes of which represent measures of tracer binding, The graphical methods are not depend ent upon a particular model structure but the slopes can be related to comb inations of the model parameters if a model structure is assumed, The input required is uptake data from a region of interest vs time and an input fun ction that can either be plasma measurements or uptake data from a suitable reference region. Graphical methods can be applied to both reversible and irreversibly binding tracers. They provide considerable ease of computation compared to the optimization of individual model parameters in the solutio n of the differential equations generally used to describe the binding of t racers. Conditions under which the graphical techniques are applicable and st,me problems encountered in separating tracer delivery and binding are co nsidered. Also the effect of noise can introduce a bias in the distribution volume which is the slope of the graphical analysis of reversible tracers. Smoothing techniques may minimize this problem and retain the model indepe ndence. In any case graphical techniques can provide insight into the bindi ng kinetics of tracers in a visual way. NUCL MED BIOL 27;7:661-670, 2000. ( C) 2000 Elsevier Science Inc, All rights reserved.