Normal patterns on 99mTc-ECD brain SPECT scans in adults

Normative ethyl cysteinate dimer (ECD) SPECT data must be available to successfully apply ECD SPECT to clinical studies. The purpose of this study was to determine ECD SPECT scan patterns of healthy adults.

Forty-eight healthy volunteers (22 men, 26 women; age range, 22-95 y; mean age, 47.6 +/- 19.2 y) underwent high-resolution ECD SPECT. For visual analysis of regional brain ECD uptake, we used a scale of +3 to -3, in which +3 and -3 indicated highest ECD uptake and deficit, respectively. For quantitative analysis, we measured the region-to-cerebellum ratio (R/CE) and the region-to-cerebral cortex ratio (R/CO) for 17 regions (13 cortical, 3 subcortical, and 1 cerebellar).

On visual analysis, no subject had a score of -3. All subjects had a score of -2 for the hippocampus and a score of +3 for the medial occipital cortex, except for 2 subjects who had a score of +3 for the striatum and thalamus. A frontal eye field and posterior parieto-occipital junction were identified in 60% of subjects with a score of +1 and 79% of subjects with a score of +2. On quantitative analysis, a significant regional variation (ANOVA, P < 0.0001) was seen in R/CE, ranging from 0.709 (hippocampus) to 1.26 (medial occipital cortex). However, regional right-to-left differences and intersubject variability of R/CE were small (asymmetry index, 3.6% +/- 0.8%; coefficient variation, 6.6% +/- 0.7%). R/CE declined significantly with age in 6 regions, including the anterior and posterior cingulate cortex, superior prefrontal and parietal cortex, striatum, and hippocampus (1.0%-2.0% per decade, P < 0.05), whereas R/CO in the cerebellum increased significantly with age (1.0% per decade, P < 0.05).

Although regional ECD brain perfusion patterns vary significantly, including variability caused by the age-related effect, intersubject variability is small. Recognition of these normal patterns is important for clinical interpretation of ECD SPECT studies.