Regional quantitative noninvasive assessment of cerebral perfusion and function with N-isopropyl-[123I]p-iodoamphetamine.

Abstract

Although several reports on the clinical usefulness of N-isopropyl-[123]p-iodoamphetamine (IMP) in the diagnosis of cerebral disease have appeared in the literature, quantitative, noninvasive measurements of regional cerebral blood flow with this method pose difficulties because cerebral IMP uptake not only depends on cerebral perfusion but also on cerebral function. Rather than trying to develop a method to measure cerebral perfusion with IMP, we have chosen to test a method to quantitatively evaluate planar and emission computed tomographic (ECT) studies by comparing the data obtained in patients with established pathology (n = 51, number of scans = 54) with the data obtained in a group of normal individuals (n = 10, number of scans = 11). Using this method, absolute cerebral IMP uptake (counts/pixel/mCi/min) and planar anterior right-left ratios were obtained. Also measured were right-left ratios obtained from 12 paired regions in three ECT slices. In the control group, we found an IMP uptake of 35.6 +/- 4.3 cts/pixel/mCi/min and right-left ratios around 1.00 (s.d. less than 2%). The evaluation of the patients cerebral IMP uptake asymmetries relative to the normal standard values is a useful adjunct to qualitative image analysis in assessing the presence and severity of disease, as qualitative analysis is prone to false-positive and negative results. Cerebral IMP uptake as measured in cts/pixel/mCi/min is abnormal only in severe cerebral disease and therefore generally a less helpful parameter.