EVALUATION OF CEREBRAL VASOREACTIVITY BY 3-DIMENSIONAL TIME-OF-FLIGHTMAGNETIC-RESONANCE ANGIOGRAPHY

Background and Purpose Cerebral vasoreactivity is an important indicat or of the reserve capacity of the cerebral circulation. To make a quan titative analysis of cerebral vasoreactivity in individual major arter ial territories, we evaluated the response to acetazolamide using thre e-dimensional time-of-flight magnetic resonance angiography. Methods W e examined 10 healthy volunteers and 6 patients with unilateral stenos is of the middle cerebral artery by a 1.5-T superconducting magnetic r esonance imaging system. After a baseline vascular image was obtained, each subject received 17 mg/kg IV of acetazolamide; a second scan was performed 20 minutes later. Using a generally available personal comp uter and image analysis software, we measured the areas of the individ ual major arteries on collapsed axial vascular images and then calcula ted the vasoreactivity. Results The average vasoreactivity of individu al major cerebral arterial territories in the healthy volunteers was a s follows: anterior cerebral artery complex, 33%; right middle cerebra l artery, 71%; left middle cerebral artery, 74%; right posterior cereb ral artery, 68%; and left posterior cerebral artery, 68%. In the patie nt group, the vasoreactivity of the stenotic middle cerebral arteries was significantly smaller than that of the nonstenotic arteries (P<.05 ). In addition, the nonstenotic middle cerebral arteries showed signif icantly less vasoreactivity than the right arteries of the healthy vol unteers (P<.01). Conclusions Three-dimensional time-of-flight magnetic resonance angiography can be used to quantitatively evaluate acetazol amide-induced vasoreactivity in individual major cerebral arterial ter ritories.