Correlative assessment of hemodynamic parameters obtained with T2*-weighted perfusion MR imaging and SPECT in symptomatic carotid artery occlusion

BACKGROUND AND PURPOSE: Perfusion MR imaging and single-photon emission CT (SPECT) are commonly used to evaluate hemodynamic status in patients with s ymptomatic occlusive cerebrovascular disease. These techniques rely on diff erent underlying physiological mechanisms, and the data may not correspond. We studied the relationship between hemodynamic parameters obtained with t hese two methods. METHODS: We performed perfusion MR imaging and SPECT in 10 patients with sy mptomatic unilateral internal carotid artery occlusion, Relative cerebral b lood volume (rCBV) and uncorrected mean transit time (uMTT) were obtained w ith dynamic contrast-enhanced T2*-weighted MR imaging. Relative cerebral bl ood flow (rCBF) and vascular reserve capacity were measured with Tc-99m-HMP AO SPECT; vascular reserve capacity was calculated by the difference in CBF before and after acetazolamide challenge. Ratios of these hemodynamic para meters between the affected and contralateral vascular territories were cal culated and compared. RESULTS: Normal-to-increased CBV, prolonged uMTT, decreased CBF, and normal -to-diminished vascular reserve capacity were observed in the affected vasc ular territories, Reduction of vascular reserve capacity corresponded well with uMTT but not with CBF and CBV, CBF, CBV, and uMTT did not correspond t o one another. CONCLUSION: uMTT is more sensitive than the other parameters in estimating vascular reserve capacity. The relationship between parameters obtained wit h perfusion MR imaging and SPECT should be considered in assessing the hemo dynamic status of patients with symptomatic occlusive cerebrovascular disea se.