Assessment and Quantification of Collateral by ASL MRI
Assessment and Quantification of Collateral by ASL MRI
Collateral circulation supports brain tissues to maintain blood perfusion in cerebral
 ischemic stroke and are of great benefit for a better outcome. A non-invasive approach
 relative to currently widely used digital subtraction angiography (DSA) is needed. ASL
 (arterial spin labeling) is a novel perfusion method without contrast agent injection and
 features both temporal and cerebral blood flow(CBF) information. The investigators applied
 multiple post labeled delay(PLD) time to pseudo-continuous Arterial Spin Labeling (3D pCASL)
 MRI and subtraction images were obtained to evaluate the collateral robustness and
 quantitatively assess the collateral perfusion in patients with unilateral middle cerebral
 artery atherosclerotic stenosis and the ability to predict future stroke recurrence.
Patients with unilateral middle cerebral artery (MCA) moderate to severe stenosis were
 consecutively enrolled. MRI protocols including diffusion weighted image, magnetic resonance
 angiography , 3D pCASL with two PLD of 1.5s and 2.5s were performed.

 Cerebral blood flow(CBF) map of 3D pCASL with PLD 1.5s and 2.5s were postprocessed on
 workstation. Subtraction images were obtained by CBF 2.5s subtracted CBF 1.5s. Slices
 involving MCA downstream territory were equally separated as upper slices,middle slices and
 inferior slices corresponding to CIS system referring to previous study of Al-Ali F. Slices
 with residual signal areas more than 1/3 MCA territory involved would count 1, or would be 0.
 Total ASL collateral score(ASLCS) was calculated from 0-3. Then ,favorable collaterals were
 graded as total ASLCS 2-3 and poor collaterals were graded as total ASLCS 0-1.

 Early-arriving flow perfusion proportion was defined as [CBF 1.5s at lesion side/CBF 2.5s of
 the contralateral side]×100%. Late-arriving perfusion proportion was defined as [(CBF 2.5s
 minus CBF 1.5s) at lesion side minus (CBF 2.5s minus CBF 1.5s) at normal side]/CBF 2.5s at
 the contralateral side ×100%. Antegrade scales and collateral grades were evaluated in
 patients with conventional angiography. Spearman correlation was analyzed between
 early-arriving and late-arriving flow and angiographic antegrade and collateral scales.

 Baseline characteristics of patients were recorded including age, gender,
 hypertension,hypercholesterolemia,diabetes mellitus,smoking,obesity,qualifying stroke event,
 admission National Institute of Health stroke scale (NIHSS), diffusion-weighted
 image-ASPECTS.

 One year stroke event recurrence and three months modified Rankin Scale (mRS) were followed
 up by neurologist by phone call or face to face.

 Multi-variants Logistic Regression is performed to exam whether ASL collateral score and
 collateral perfusion quantification is significantly correlated with future ischemic event
 and functional outcome.
Inclusion Criteria:

 -  Ischemic stroke or TIA in anterior circulation within 90 days

 -  MCA atherosclerotic moderate to severe stenosis(50%-99%) confirmed by conventional
 angiography or magnetic resonance angiography

 -  Age >18

 -  2 or more atherosclerotic risk factors including hypertension, hypercholesterolemia,
 diabetes mellitus, cigarette smoking, and obesity

 -  Medical treatment

 -  Not receiving stent therapy

 -  Ability to comply with all studies

 Exclusion Criteria:

 -  Multiple intracranial arteries stenosis (> 50%) or occlusion

 -  Less than 2 atherosclerotic risk factors

 -  Pregnancy and other contraindication to MRI scan

 -  Informed consent not obtained