A general method to correct PET data for tissue metabolites using a dual-scan approach

This article presents and analyses a general method of correcting for the p resence of radiolabeled metabolites from a parent radiotracer in tissue dur ing PET scanning. The method is based on a dual-scan approach, i.e., parent scan together with an independent supplementary scan in which the radiolab eled metabolite of interest itself is administered. The method corrects for the presence of systemically derived radiolabeled metabolite delivered to the tissues of interest through the blood. Methods: Data from the supplemen tary scan are analyzed to obtain the tissue impulse response function for t he metabolite, The time course of the radiolabeled metabolite in plasma in the parent scan is convolved with its tissue impulse response function to d erive a correction term. This is not a simple subtraction technique but 1 t hat takes account of the different time-activity curves of the radiolabeled metabolite in the 2 scans. Results: The method, its implications, and its limitations are discussed with respect to [C-11]thymidine and its principal metabolite (CO2)-C-11. Conclusion: The general method, based on a dual-sca n approach, can be used to correct for radiolabeled metabolites in tissues of interest during PET scanning. The correction accounts for radiolabeled m etabolites that are derived systemically and delivered to the tissues of in terest through the blood.