Measurement of collateral perfusion in acute stroke: a vessel-encoded arterial spin labeling study

Thomas W Okell,Peter Jezzard,James Kennedy,Michael A Chappell,George W J Harston,Fintan Sheerin

doi:10.1038/s41598-019-44417-7

Abstract

Collateral perfusion is important for sustaining tissue viability in acute ischemic stroke. Conventional techniques for its visualization are invasive, require contrast agents and demonstrate collateral vessels, rather than measuring perfusion directly. In this study we utilize a non-invasive, non-contrast magnetic resonance imaging (MRI)-based method to directly quantify collateral perfusion in acute stroke patients. Vessel-encoded multi-postlabeling delay arterial spin labeling (ASL) was used to separately quantify the blood flow and blood arrival time from four arteries supplying the brain in patients presenting within 18 hours of stroke onset. Twenty-nine acute ischemic stroke patients were scanned with a median time of onset to first MRI of 3 hours. Collateral perfusion at presentation was associated with tissue fate at 1-week. It sustained tissue prior to reperfusion, but was less effective than direct blood flow at maintaining tissue viability in patients who did not reperfuse. Delay in the blood arrival around the ischemic region was found at presentation and reduced over time but was not consistently associated with collateral perfusion. Vessel-encoded multi-postlabeling delay ASL provides a non-invasive tool for direct measurement of collateral perfusion and delayed blood arrival in acute stroke patients.

Highlights

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We present the use of multi-PLD Vessel-encoded pseudocontinuous ASL (VEPCASL) acquired serially in a cohort of patients with acute ischemic stroke
We demonstrate that VEPCASL can concurrently identify collateral perfusion patterns and delayed blood arrival serially in these patients, and assess whether collateral perfusion measured at presentation is associated with tissue fate at follow-up

Summary

Methods

Preliminary scans were as follows: 1) a rapid 3D time-of-flight (TOF) angiogram of the neck (voxel size 0.8 × 0.8 × 1.3 mm, acquisition time 47 s) to position the VEPCASL labeling plane and identify the location of the feeding arteries within this plane: the right and left internal carotid arteries (ICAs), and the right and left vertebral arteries (VAs), as described previously18; 2) Diffusion-weighted images (DWI, voxel size 1.8 × 1.8 × 2.0 mm, b = 0 and 1000 s/mm[2], acquisition time 3 min) to define the ischemic core; and 3) a T1-weighted structural image (voxel size 1.8 × 1.8 × 1.0 mm, acquisition time 4 min) to aid registration These were followed by ASL perfusion imaging, using a previously described protocol[14,18] which builds on the minimum standards outlined in a recent consensus paper[19]. Final infarction was defined preferentially on the 1-week FLAIR, or on the 24-hour trace DWI if the 1-week timepoint was not available[26] These masks enabled two specific ROIs to be generated which were not derived from a perfusion-based definition of tissue at risk: 1.

Peri-core

Results

Discussion

Conclusions