Use of I and C in a Double Radionudide Autoradiographic Technique for Simultaneous Measurement of LCBF and LCMRgl Theory and Method

We have developed an autoradiographic technique for tbe simultaneous measurement of local cerebral blood flow (LCBF) and local cerebral metabolic rate for glucose (LCMRgl) using '"Modoantipyrioe and "C-2-deoxyglucose respectively. By exploiting tbe different half-lives of "I and "C, 13.0 hours versus 5730 years, we produce 2 autoradiographic images. The first is predominantly a result of the "*I and the second is predominantly from the C. Because of the Impracticality of making m I standards, it was necessary to determine the constant which relates the ability of I, with respect to "C, to expose Kodak SB-54 fllm, so that tbe '"I exposure could be quantified using "C standards. Subtraction equations can then be used to solve for the local I and "C concentrations. The technique was validated in conditions simulating a 12-fold decoupling of flow and metabolism and the standard deviation of error in measuring tracer concentrations was less than 6%. It was then used to measure these parameters in the normal awake rats and values obtained agreed well with published values from single radionudide studies. The technique is expected to be useful in the simultaneous measurement of LCBF and LCMRgl in various physiologic or pathologic states, including those with significant decoupling of flow and metabolism. In addition, by using other tracers labelled with '"I and "C, other parameters can be measured concurrently. Stroke, Vol 12, No 5, 1981