[Evaluation of regional cerebral blood flow in hippocampus by 99mTc-ECD SPECT: comparison with 123I-IMP SPECT].

We evaluated regional cerebral blood flow in the hippocampus in 21 patients with neurological disorders by 99mTc-ethyl cysteinate dimer (ECD) SPECT and compared the findings with those by 123I-N-isopropyl-p-iodoamphetamine (IMP) SPECT. In all subjects, SPECT was taken using ECD (740 MBq) and IMP (167 MBq) using high performance SPECT (3-head SPECT, Toshiba GCA-9300A/HG) within 3 weeks interval. Regional uptake in the hippocampus was examined in the coronal sections and images parallel to the longitudinal axis of hippocampus. ECD and IMP showed similar hippocampal uptake in 9 cases, but ECD showed less uptake than IMP in 12 cases (57%). Regional counts in the hippocampus were related to the counts in the lateral temporal cortices and the mean count ratio was lower in ECD by 8.8% than that in IMP (0.73 +/- 0.11 vs. 0.80 +/- 0.11, p < 0.001). In 6 patients suspected to have hippocampal lesion (4 cases of memory disturbance and 2 cases of epilepsy), all cases showed decreased uptake of ECD in hippocampus, but only 3 cases showed decreased uptake of IMP. This is suggestive to be relevant to the difference in the retention mechanism of ECD and IMP, but further investigation should be performed.