Comparison of early and late images on 123I-iomazenil SPECT with cerebral blood flow and oxygen extraction fraction images on PET in the cerebral cortex of patients with chronic unilateral major cerebral artery occlusive disease

Abstract

The aim of the present study was to determine whether early and late/early images on 123I-iomazenil (IMZ) single-photon emission computed tomography (SPECT) correlate with cerebral blood flow (CBF) images and oxygen extraction fraction (OEF) images on PET, respectively, in the cerebral cortex of patients with chronic unilateral middle cerebral artery or internal carotid artery occlusive disease. In 20 normal individuals and in 68 patients, CBF and OEF were assessed using 15O-PET, and brain SPECT scans were initiated immediately after (early images) and 180 min after (late images) the administration of 123I-IMZ. A region of interest was automatically placed in the middle cerebral artery territory in both cerebral hemispheres using a three-dimensional stereotaxic region of interest template, and the ratio of the value in the affected side to that in the contralateral side was calculated in each image. Among patients, a significant positive correlation was observed between PET-CBF ratios and the SPECT-early IMZ ratios (r=0.797, P<0.0001) as well as between the PET-OEF ratios and the SPECT-late/early IMZ ratios (r=0.679, P<0.0001). When an abnormally elevated PET-OEF ratio was defined as a value greater than the mean+2 SD obtained in normal participants, the SPECT-late/early IMZ ratios yielded 100% sensitivity and 93% specificity, with 76% positive-predictive and 100% negative-predictive values for detecting abnormally elevated PET-OEF ratios. Early and late/early images on 123I-IMZ SPECT correlate with CBF images and OEF images on PET, respectively, in the cerebral cortex of patients with chronic unilateral major cerebral artery occlusive disease.