Simplified calculation of MRglc using PET.

glucose (FDu) has diagnostic value in monitoring the effects of therapy, for example, in oncology (/ ) and in basic research on brain function (2-4). Some applications do not require absolute quantification since relative values of MRglc are sufficient. Quantification is essential, however, for comparisons between repeated measurements (5) or between results from different laboratories. The standard technique for quantifying MRglc, as described by Sokoloff et al. (6) and Huang et al. (7), requires many samples of arterial plasma. On the basis of plasma curves from 119 PET acquisitions in human subjects administered FDG. we showed high correlation between the concentration of radiotracer in arterial plasma at a fixed time and values of the plasma integrals C,(T) and C2(T), where T is the time of measurement of radioactivity in tissue, C, is the concentration of radioactivity in the compartment directly coupled to plasma and governed by facilitated transport of the radiotracer in tissue and C2 is the concentration in the compartment containing labeled phosphorylated metabolite (2-[18F]fluoro-