Normal patterns on Tc-99m-ECD brain SPECT scans in adults

Normative ethyl cysteinate dimer (ECD) SPECT data must be available to succ essfully apply ECD SPECT to clinical studies. The purpose of this study was to determine ECD SPECT scan patterns of healthy adults. Methods: Forty-eig ht 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 re gional brain ECD uptake, we used a scale of +3 to -3, in which +3 and -3 in dicated highest ECD uptake and deficit, respectively. For quantitative anal ysis, we measured the region-to-cerebellum ratio (R/CE) and the region-to-c erebral cortex ratio (R/CO) for 17 regions (13 cortical, 3 subcortical, and 1 cerebellar). Results: 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 th e 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-occipi tal 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 reg ional Variation (ANOVA, P < 0.0001) was seen in RICE, ranging from 0.709 (h ippocampus) to 1.26 (medial occipital cortex). However, regional right-to-l eft differences and intersubject variability of R/CE were small (asymmetry index, 3.6% +/- 0.8%; coefficient variation. 6.6% +/- 0.7%). RICE declined significantly with age in 6 regions, including the anterior and posterior c ingulate cortex, superior prefrontal and parietal cortex, striatum, and hip pocampus (1.0%-2.0% per decade, P < 0.05), whereas R/CO in the cerebellum i ncreased significantly with age (1.0% per decade, P < 0.05). Conclusion: Al though regional ECD brain perfusion patterns vary significantly, including variability caused by the age-related effect, intersubject variability is s mall. Recognition of these normal patterns is important for clinical interp retation of ECD SPECT studies.