Is the Physical Decay Correction of the 18F-FDG Input Function in Dynamic PET Imaging Justified?

Abstract

In this theoretic note, the rationale for the physical decay correction of the (18)F-FDG input function in dynamic PET is investigated, using the Patlak equation as an example. The Patlak equation conventionally obtained when correcting the (18)F-FDG input function and correcting the tissue activity measurement for (18)F physical decay can also be derived from a 2-compartment analysis that does not conceptually involve any physical decay correction of the (18)F-FDG input function but accounts only for the physical decay of the trapped tracer. We demonstrate that exactly the same equation can be derived from the 2 conceptual approaches, and hence each approach yields the correct uptake rate of the tracer. No advantage in (18)F-FDG dynamic PET can be expected from using the concept of uncorrected data rather than that of decay-corrected data. Nevertheless, conceptually, we show that correcting the (18)F-FDG input function for radioactive decay cannot be justified and that this correction is not compatible with the calculation of patient radiation dose.