AN ALTERNATIVE METHOD TO NORMALIZE CLINICAL FDG STUDIES

An alternative method of determining the integrated input function, ne cessary in the quantitative [F-18]fluorodeoxyglucose (FDG) autoradiogr aphic model, has been developed, Using erythrocytes as reference tissu e, researchers require only one blood sample after injection of FDG to obtain the integrated input function, Methods: The amount of FDG-6-PO 4 in the erythrocytes is proportional to their exposure to FDG, that i s, the integrated input function. Free FDG is removed by washing the e rythrocytes twice, Inter-and intraindividual differences of the metabo lic rate of erythrocytes are corrected for by an in vitro incubation w ith a known amount of FDG, Results: Validation of the proposed method was done by correlating the integrated input function, based on the gl ucose metabolism of the erythrocytes, to the integrated input function obtained by multiple venous blood samples, The new method provides th e integrated input function with an accuracy better than +/-8%. Conclu sion: By using erythrocytes as a reference tissue, researchers can det ermine the integrated input function in the quantitative FDG autoradio graphic model with an accuracy sufficient for clinical PET studies, Th e simplicity of the method also makes it suitable for FDG studies on s mall children. With two samples, the method can also be used for a sim plified graphical Patlak analysis.