Intracranial Hemodynamics Is Altered by Carotid Artery Disease and After Endarterectomy

Abstract

Background and Purpose-Carotid endarterectomy (CEA) has become a routine procedure to treat symptomatic carotid artery disease and reduce the risk of recurrent cerebral ischemic events. The purpose of this study was to use an arterial spin labeling dynamic magnetic resonance angiography technique to characterize intracranial hemodynamics before and after CEA. Methods-Thirty-seven carotid artery disease patients participated in this study, of whom 24 underwent magnetic resonance imaging before and after CEA. Seventeen control subjects spanning 5 decades underwent magnetic resonance imaging to assess age-related changes. Hemodynamic metrics (that is, relative time to peak and amplitude) were calculated with a ␥-variate model. Linear regression was used to relate carotid artery disease burden to downstream hemodynamics in the circle of Willis. Results-Relative time to peak increased with age in controls (PϽ0.020). For patients, relative time to peak was positively correlated with percent stenosis (PϽ0.050), independent of age. At 1 day after CEA, the middle cerebral artery ipsilateral to the CEA showed significant dynamic magnetic resonance angiography changes: relative time to peak decreased (PϽ0.017) and the flow amplitude increased (PϽ0.009). No pre-versus post-CEA changes were significant in the contralateral middle cerebral artery or posterior segments. Conclusions-This noninvasive, arterial spin labeling-based method produced time-resolved images that were used to characterize intracranial arterial flow associated with aging, extracranial carotid artery disease, and CEA. Results demonstrate that the technique has the sensitivity to detect hemodynamic changes after CEA. (Stroke. 2011;42:979-984.)Key Words: endarterectomy Ⅲ carotid stenosis Ⅲ arterial spin labeling Ⅲ angiography Ⅲ dynamic Ⅲ blood flow Ⅲ aging A therosclerosis is a major risk factor for ischemic cerebrovascular events. Extracranial steno-occlusive disease influences hemodynamics and physiology in the brain. 1 Therefore, carotid endarterectomy (CEA) is a standard treatment for patients with symptomatic stenosis Ͼ70% because surgical therapy is associated with higher event-free survival compared with medical therapy. 2 However, CEA is not without risk; 1 study reported a 4.3% increase in the risk of stroke or death within 30 days of CEA. 2 Other studies report silent infarcts, evident postoperatively on diffusion-weighted images in 17% to 33% of CEA patients. 3,4 Therefore, there is merit in developing imaging techniques that can be used to assess the downstream impact of extracranial steno-occlusive disease. phase encoding, nor does it require that slices be perpendicular to the vessels of interest. The purpose of this study was to determine whether ASL-based DynAngio could be used to characterize circle of Willis hemodynamics, as it provides the primary means of collateral blood supply in the brain. We collected data from control subjects and patients with carotid artery disease to test the hypotheses that DynAngio hemodynamic measures are capab...

A kinetic model for vessel‐encoded dynamic angiography with arterial spin labeling

“…A larger study would be necessary to demonstrate whether these differences are significant, but similar changes in such parameters have been observed in other studies of patients with cerebrovascular disease. For example, the degree of carotid artery stenosis has been shown to be correlated with arrival time differences between hemispheres (30), and flow amplitude and time to peak, a parameter relating to bolus dispersion, in the ipsilateral MCA are altered following carotid endarterectomy (20). Although these studies and others (such as those by van Osch et al (31) and Okell et al (13)) have demonstrated maps relating to blood arrival time and/or dispersion, these used empirical approaches or less sophisticated models and most are not appropriate for the VEPCASL preparation used in this study where blood inflow is not observed in many voxels.…”

“…For this study, we choose a gamma variate function for the dispersion kernel (Fig. 1b), which has been used previously to model the inflow of an injected bolus of contrast agent (19) or pulsed ASL preparation (20). Here, we aim to model the bolus dispersion rather than the entire bolus time course, but this function has the desirable properties of being causal and the ability to model a long tail, suitable for describing blood flowing in a laminar fashion.…”

Evaluating quantitative approaches to dynamic susceptibility contrast MRI among carotid endarterectomy patients

“…We have previously used arterial spin labeling dynamic angiography to show that CEA alters large vessel hemodynamics in the ipsilateral MCA (31). Following CEA, relative TTP and amplitude in the ipsilateral MCA were more similar to their contralateral counterparts.…”

Modeling the residue function in DSC‐MRI simulations: Analytical approximation to in vivo data

“…[47–85 years. ], M:F = 5:3) with atherosclerotic disease under an Institutional Review Board approved protocol and as part of a larger neuroimaging study . MRI data were acquired on a Siemens 3 Tesla (T) Trio scanner with gradient‐echo echo planar imaging (EPI): repetition time/echo time (TR/TE) = 1.5 s/30 ms, 78 volumes, 128 × 128 × 22 matrix, 1.7 × 1.7 × 5 mm 3 voxels, and diffusion weighted imaging (DWI): TR/TE = 4.4 s/93 ms, b‐values = 0, 1000 s/mm 2 (3 orthogonal directions), 27 slices, 1.6 × 1.6 × 3 mm 3 voxels.…”