Brain single-photon emission CT studies using 99mTc-HMPAO and 99mTc-ECD early after recanalization by local intraarterial thrombolysis in patients with acute embolic middle cerebral artery occlusion

BACKGROUND AND PURPOSE: The brain distribution of Tc-99m-hexamethylpropyleneamine oxime (HMPAO) correlates with regional brain perfusion, whereas Tc-99m-ethyl cysteinate dimer (ECD) reflects not only perfusion but also the metabolic status of brain tissue. We compared Tc-99m-ECD single-photon emission CT (SPECT) with Tc-99m-HMPAO SPECT early after recanalization by local intraarterial thrombolysis (LIT) in patients with acute embolic middle cerebral artery occlusion, We also assessed the predictive value of Tc-99m-HMPAO and Tc-99m-ECD SPECT for the development of ischemic brain damage. METHODS: Tc-99m-HMPAO and consecutive Tc-99m-ECD SPECT studies were performed in 15 patients within 3 hours of LIT. The two SPECT studies were obtained independently using a subtraction technique. SPECT evaluation was performed using semiquantitative region-of-interest analysis. Noninfarction, infarction, and hemorrhage were identified by follow-up CT or MR imaging. RESULTS: Forty-five lesions were identified (21 noninfarctions, 19 infarctions, and five hemorrhages), Regardless of Tc-99m-HMPAO SPECT findings, lesions showing isoactivity (count rate densities of 0.9 to 1.1 as compared with the contralateral side) on Tc-99m-ECD SPECT were salvaged. Lesions with hypoactivity (values < 0.9) on Tc-99m-ECD SPECT developed irreversible brain damage. Hemorrhage appeared in lesions with both hyperactivity (values > 1.1) on Tc-99m-HMPAO SPECT and hypoactivity on Tc-99m-ECD SPECT. CONCLUSION: The brain distribution of Tc-99m-ECD in a reperfused area identified by Tc-99m-HMPAO SPECT early after recanalization of acute ischemic stroke is dependent on cerebral tissue viability. By combining Tc-99m-ECD and Tc-99m-HMPAO SPECT, performed within the first few hours of LIT, it is possible to identify patients at risk for hemorrhagic transformation reliably.