Noninvasive MR imaging of cerebral perfusion in patients with a carotid artery stenosis

Background: Arterial spin labeling (ASL) perfusion MRI with image acquisition at multiple delay times can be used to measure delays in the arrival of arterial blood to the brain. We assessed the effect of a symptomatic internal carotid artery (ICA) stenosis on ASL timing parameters, and evaluated the effect of collateral flow through the circle of Willis. Methods: Forty-four functionally independent patients (30 men, 69 ± 9 years) with a recently symptomatic ICA stenosis ≥50% and 34 sex-matched and age-matched healthy volunteers were investigated. Magnetic resonance angiography and 2-dimensional phase-contrast imaging were used to assess collateral flow in the circle of Willis. Results: In the hemisphere ipsilateral to the ICA stenosis, cerebral blood flow (CBF) was lower (p < 0.01) in the anterior frontal, posterior frontal, parieto-occipital, and occipital regions than in control subjects. The transit times were prolonged (p < 0.01) in the ipsilateral anterior frontal, posterior frontal, and frontoparietal regions when compared with the control subjects. The trailing edge time was prolonged (p < 0.01) in the ipsilateral frontoparietal region when compared to the control subjects. In the 27 patients without a contralateral stenosis, the trailing edge was longer (p < 0.01) in the ipsilateral posterior frontal, frontoparietal, and parieto-occipital regions than in the contralateral regions. Collateral flow via the circle of Willis did not affect CBF and transit or trailing edge times. Conclusion: Arterial spin labeling MRI is a noninvasive tool for imaging cerebral blood flow and delays in the arrival of arterial blood to the brain, and can potentially provide valuable information on the quality of perfusion to the brain in patients with cerebrovascular disease.