INTRAINDIVIDUAL DIFFERENCES BETWEEN TECHNETIUM-99M-HMPAO AND TECHNETIUM-99M-ECD IN THE NORMAL MEDIAL TEMPORAL-LOBE

Regional distributions of Tc-99m-hexamethyl propyleneamine oxime (Tc-9 9m-HMPAO) and Tc-99m-ethyl cysteinate dimer (Tc-99m-ECD) were compared in the normal brain. Methods: Six paid, healthy volunteers (mean age 26 yr) had high-resolution neuroperfusion SPECT using both Tc-99m-HMPA O and Tc-99m-ECD On Separate days. Results: Regional distribution of t he two tracers differed. Technetium-99m-HMPAO accumulated more in the thalamus, frontal lobe, temporal lobe and cerebellum than Tc-99m-ECD, Which accumulated more in the occipital and parietal lobes. There was a considerable difference in the accumulations of the two tracers in t he medial temporal lobe. The percent accumulations of Tc-99m-HMPAO and Tc-99m-ECD in the medial temporal lobe compared with the mean global cerebral cortical accumulation were 93.9% +/- 2.4% and 83.1% +/- 4.1% (mean +/- s.d.), respectively. Conclusion: The results suggest that Tc -99m-HMPAO and Tc-99m-ECD require specific and separate criteria for d iagnosing temporal lobe pathologies, such as dementia and temporal lob e epilepsy.