Correlation of 99mTc-DTPA SPECT of the blood-brain barrier with neurologic outcome after acute stroke

Abstract

We conducted a study on humans to determine whether quantitative evaluation of blood-brain barrier (BBB) breakdown using the (99m)Tc-diethylenetriaminepentaacetic acid ((99m)Tc-DTPA) SPECT technique at the peak time of stroke evolution can predict neurologic outcome.

Methods: Thirty consecutive patients with acute stroke of the middle cerebral artery occurring >24 h and <48 h before admission were included in the study. Each patient underwent a complete neurologic examination according to the Scandinavian stroke score at 72 h after the stroke (S1) and again at 30 d (S2). The difference between initial and late scores was calculated (Delta S) and used to evaluate the change in neurologic status. A CT scan was obtained on all patients to determine the volume of stroke. The integrity of the BBB was evaluated using (99m)Tc-DTPA brain SPECT. A quantitative index of BBB disruption was defined as the ratio of the mean counts/pixel in the infarcted region compared with the mean counts/pixel in the contralateral nonaffected hemisphere. SPECT perfusion imaging was also performed with (99m)Tc-hexamethylpropyleneamine oxime ((99m)Tc-HMPAO) at 24 h after the (99m)Tc-DTPA study. The relative perfusion in the infarct region was expressed as the percentage of contralateral perfusion.

Results: The mean (99m)Tc-DTPA disruption index was 6.8 +/- 6.9 (range, 1-26.2). Seven patients (23%) had no BBB disruption. Statistical analysis showed that the disruption index was negatively correlated with Delta S (r = -0.423, P < 0.02). A disruption index of <2.5 was associated with a significantly better neurologic outcome (mean Delta S, 17.5 +/- 9.5) compared with patients with an index of >2.5 (mean Delta S, -0.85 +/- 4.97, P < 0.0001) with a sensitivity of 95% and a specificity of 89%. S2 was significantly correlated with S1 (r = 0.738, P < 0.001) and with Delta S (r = 0.656, P < 0.001). Perfusion abnormalities on the (99m)Tc-HMPAO SPECT studies ranged between 12% and 90% (mean, 37.6% +/- 17.8%) compared with those on the contralateral nonaffected side. No correlation was found between (99m)Tc-HMPAO uptake and Delta S, infarct volume by CT, or disruption index. The CT volume measurements were negatively correlated with S2 (r = -0.560, P < 0.004) but not with Delta S.

Conclusion: (99m)Tc-DTPA SPECT of the BBB combined with quantitative analysis in patients with acute stroke is significantly related to clinical outcome, with a distinct prognostic cutoff threshold of 2.5. The use of this radionuclide brain SPECT technique represents a unique application of conventional nondiffusible brain agents.