The discrepancy between Tc-99(m)-ECD dynamic and static SPET images in patients with ischaemic lesions corresponds to reduced vasoreactivity to acetazolamide

We evaluated Tc-99(m)-N,N'-(1,2-ethylenediyl)bis-L-cysteine diethyl ester ( Tc-99(m)-ECD) dynamic and static SPET (single photon emission tomographic) images to examine Tc-99(m)-ECD kinetics under ischaemic cerebrovascular con ditions. In 20 patients who showed arterial occlusion on magnetic resonance angiography, dynamic (0-10 min) and static (15-35 min) SPET images were ac quired after the intravenous administration of Tc-99(m)-ECD. Thirteen of th e patients had focal perfusion deficits that were more evident on the dynam ic than on the static images; the other seven showed no such discrepancy. I n those patients with a mismatch between the dynamic and static images, the extent corresponded to reduced vasoreactivity to acetazolamide. Based on q uantitative analysis of the ratio of tracer uptake in affected to that in u naffected areas, the patients with discrepant findings showed significantly different ratios on the dynamic and static images, whereas those with no s uch mismatch did not. Our results suggest that dynamic Tc-99(m)-ECD images provide circulatory information and that static images reflect a filling-in phenomenon of ECD metabolites in ischaemic lesions. Tc-99(m)-ECD dynamic a nd static SPET images offer an alternative method of detecting mild perfusi on deficits without the need for acetazolamide challenge. ((C) 1998 Lippinc ott Williams & Wilkins).