Technetium-99m-ECD brain SPECT in misery perfusion.

UNLABELLED

Discordant findings of 99mTc-methyl cysteinate dimer (99mTc-ECD) brain distribution have been reported when brain tissue is supplied by excess blood flow. We evaluated changes in 99mTc-ECD brain activity in the opposing pathological state, in which cerebral blood flow (CBF) is more profoundly impaired than metabolism, and analyzed the relationship of 99mTc-ECD activity with CBF and metabolism to investigate the dominant regulating factor on 99mTc-ECD distribution.

METHODS

Twelve patients with unilateral intracranial steno-occlusive diseases were evaluated using dynamic and static 99mTc-ECD SPECT. Relative 99mTc-ECD activities and the retention ratio of the affected and unaffected cortices were compared with CBF and oxygen metabolism obtained by PET. Change in the relationships until 1 hr after tracer injection were also analyzed.

RESULTS

Relative 99mTc-ECD activity was significantly correlated with CBF, and the highest correlation was obtained for the first minute of imaging (r = 0.674, p < 0.0010. Fifteen minutes after injection, the correlation coefficient with CBF decreased, whereas higher correlation was observed with the parameter of oxygen metabolism (r = 0.758-0.815, p < 0.001). Changes in the retention ratio were dependent on changes in oxygen metabolism, and the retention ratio for the high oxygen extraction fraction (OEF) area was the same as that for the normal OEF area.

CONCLUSION

In addition to CBF, brain distribution on 99mTc-ECD SPECT images is affected by brain metabolism, especially on delayed images after injection. The degree of discrepancy between CBF and metabolism should be considered when interpreting images of the misery perfusion state.