Differences in Hemodynamic Alteration between Atherosclerotic Occlusive Lesions and Moyamoya Disease: A Quantitative (15)O-PET Study

To clarify the differences in hemodynamic status between atherosclerotic steno-occlusive lesions (SOL) and moyamoaya disease (MMD), hemodynamic parameters were compared using (15)O-PET. Twenty-four patients with unilateral SOL (67 ± 11 y) and eighteen with MMD (33 ± 16 y) were assigned to this study. MMD patients were divided into twelve unilateral and six bilateral lesions. All patients underwent (15)O-PET to measure cerebral blood flow (CBF), blood volume (CBV), oxygen extraction fraction (OEF), and metabolic rate (CMRO(2)). Acetazolamide was administered after the baseline scan and the second (15)O-water PET was performed to evaluate cerebrovascular reactivity (CVR). For the CBF calculation in (15)O-water PET, the three-weighted integral method was applied based on a one-tissue compartment model with pixel-by-pixel delay correction to measure precise CBF and arterial-to-capillary blood volume (V(0)). Baseline hemodynamic parameters showed significantly lower CBF, V(0), and CMRO(2), but greater CBV, OEF, and delay (p < 0.01) in the affected hemispheres than in the unaffected hemispheres. After ACZ administration, both hemispheres showed a significant increase in CBF (p < 0.0001), but not in V(0). CVR differed significantly between the hemispheres. The arterial perfusion pressure of the functioning arterial part tended to be reduced after acetazolamide administration in patients with past neurologic events caused by hemodynamic impairment. MMD patients showed greater inactive vascular and venous volumes compared with common atherosclerotic SOL patients. The hemodynamic status of cerebral circulation may vary according to the chronic process of steno-occlusive change and the development of collateral circulation. In order to evaluate physiologic differences between the two diseases, (15)O-PET with an acetazolamide challenge test is useful.