Model-independent plot of dynamic PET data facilitates data interpretation and model selection

Abstract: When testing new PET radiotracers or new applications of existing tracers, the blood–tissue exchange and the metabolism need to be examined. However, conventional plots of measured time–activity curves from dynamic PET do not reveal the inherent kinetic information. A novel model-independent volume–influx plot (vi-plot) was developed and validated. The new vi-plot shows the time course of the instantaneous distribution volume and the instantaneous influx rate. The vi-plot visualises physiological information that facilitates model selection and it reveals when a quasi-steady state is reached, which is a prerequisite for the use of the graphical analyses by Logan and Gjedde–Patlak. Both axes of the vi-plot have direct physiological interpretation, and the plot shows kinetic parameter in close agreement with estimates obtained by non-linear kinetic modelling. The vi-plot is equally useful for analyses of PET data based on a plasma input function or a reference region input function. The vi-plot is a model-independent and informative plot for data exploration that facilitates the selection of an appropriate method for data analysis. [Copyright &y& Elsevier]