A METHOD FOR ESTIMATING THE INTEGRAL OF THE INPUT FUNCTION FOR THE QUANTIFICATION OF CEREBRAL BLOOD-FLOW WITH I-123 IMP USING ONE-POINT ARTERIAL BLOOD-SAMPLING

We have developed a new method to replace the conventional method of q uantitatively measuring cerebral blood flow (CBF), in which octanol-ex tracted radioactivity counts are measured in continuous arterial blood samples. With the new method, the whole-brain time-activity curves ea rly after the intravenous injection of N-isopropyl-p-[I-123] iodoamphe tamine were first obtained by the least-squares curve-fitting method. The equation thus obtained was differentiated and the radioactivity co unts were corrected by the 5-min octanol-extracted radioactivity count s of the arterial blood sample obtained at a single time point. In the present study, the value obtained by integrating the equation from 0 to 5 min, which was obtained by curve-fitting, was compared with the o ctanol-extracted radioactivity counts obtained by 5-min continuous art erial blood sampling in 160 patients with cerebrovascular disorders. T he results showed good agreement between the values obtained by the tw o procedures (y = 1.049x - 1522.4; r = 0.987). Using the CBF obtained by the 5-min continuous arterial blood sampling as the standard, the e rrors using the present integral values of the input function were 7.1 +/- 4.9%. Measurements of the integral of the input function by the p resent one-point arterial blood sampling method has the potential for use in the routine measurement of CBF, because it is less invasive and more convenient than the conventional method, and it is unaffected by cardiopulmonary disease or smoking. ((C) 1998 Lippincott-Raven Publis hers).