[Noninvasive quantitative measurement of cerebral blood flow with 123I-IMP--a study concerning the input function]

For the noninvasive quantitative measurement of cerebral blood flow (CBF) using N-isopropyl-[123I]p-iodoamphetamine (IMP), we studied the usefulness of the lung clearance curve obtained by a single probe detector as the input function for brain as an alternative to arterial blood activity. In four patients, we compared the time-activity curve of the lung and serial arterial blood activity for approximately 20 minutes following an IV bolus injection of IMP. Significant positive correlations were observed between lung clearance and the integral of arterial blood activity of IMP. In addition, a study to identify the best region for monitoring lung activity with the probe detector was performed in six patients using a gamma camera and region of interest (ROI) management. The central region of the right lung was found to be the best position for monitoring lung radioactivity. This study suggests that the lung clearance curve of IMP can be used as the input function for brain in the quantitative assessment of CBF.