Local Cerebral Blood Flow Measurement by SPECT using <SUP>123</SUP>I-IMP in Patients with Occlusive Cerebrovascular Disease

Abstract

N-isopropyl-p-[123I] iodoamphetamine (123I-IMP) is a lipid-soluble radiopharmaceutical that penetrates the normal blood-brain barrier, and has a high first-pass extraction efficiency in the brain. When 123I-IMP is given intravenously, its activity in the brain is maintained for several hours and its distribution is postulated to be proportional to the local cerebral blood flow (ICBF). When combined with single photon emission computed tomography (SPECT), the regional activity of 123I-IMP can be quantified. Tomographic images of ICBF were obtained with both the 133Xe inhalation method and intravenous administration of 123I-IMP in patients with occlusive cerebrovascular diseases. Four patients with transient ischemic attacks showed normal X-ray CT but had decreased ICBF on SPECT in the areas corresponding to neurologic deficits. SPECT images showed low ICBF earlier and larger than X-ray CT abnormalities which appeared in patients with cerebral infarction. SPECT with the 133Xe inhalation method gives absolute ICBF values and has the advantage over 123I-IMP of short examination time. However, higher spatial resolution is obtained by 123I-IMP SPECT. X-ray CT will maintain a major role in the investigation of neurologic diseases when assessment of anatomic and morphologic changes is needed, and 1231-IMP SPECT perfusion images should have a complementary role in the menagement of neurologic diseases associated with alteration of ICBF.