Comparison of CBF Measured with Combined Velocity-Selective Arterial Spin-Labeling and Pulsed Arterial Spin-Labeling to Blood Flow Patterns Assessed by Conventional Angiography in Pediatric Moyamoya

Abstract

Background and purpose: Imaging CBF is important for managing pediatric moyamoya. Traditional arterial spin-labeling MR imaging detects delayed transit thorough diseased arteries but is inaccurate for measuring perfusion because of these delays. Velocity-selective arterial spin-labeling is insensitive to transit delay and well-suited for imaging Moyamoya perfusion. This study assesses the accuracy of a combined velocity-selective arterial spin-labeling and traditional pulsed arterial spin-labeling CBF approach in pediatric moyamoya, with comparison to blood flow patterns on conventional angiography.

Materials and methods: Twenty-two neurologically stable pediatric patients with moyamoya and 5 asymptomatic siblings without frank moyamoya were imaged with velocity-selective arterial spin-labeling, pulsed arterial spin-labeling, and DSA (patients). Qualitative comparison was performed, followed by a systematic comparison using ASPECTS-based scoring. Quantitative pulsed arterial spin-labeling CBF and velocity-selective arterial spin-labeling CBF for the middle cerebral artery, anterior cerebral artery, and posterior cerebral artery territories were also compared.

Results: Qualitatively, velocity-selective arterial spin-labeling perfusion maps reflect the DSA parenchymal phase, regardless of postinjection timing. Conversely, pulsed arterial spin-labeling maps reflect the DSA appearance at postinjection times closer to the arterial spin-labeling postlabeling delay, regardless of vascular phase. ASPECTS comparison showed excellent agreement (88%, κ = 0.77, P < .001) between arterial spin-labeling and DSA, suggesting velocity-selective arterial spin-labeling and pulsed arterial spin-labeling capture key perfusion and transit delay information, respectively. CBF coefficient of variation, a marker of perfusion variability, was similar for velocity-selective arterial spin-labeling in patient regions of delayed-but-preserved perfusion compared to healthy asymptomatic sibling regions (coefficient of variation = 0.30 versus 0.26, respectively, Δcoefficient of variation = 0.04), but it was significantly different for pulsed arterial spin-labeling (coefficient of variation = 0.64 versus 0.34, Δcoefficient of variation = 0.30, P < .001).

Conclusions: Velocity-selective arterial spin-labeling offers a powerful approach to image perfusion in pediatric moyamoya due to transit delay insensitivity. Coupled with pulsed arterial spin-labeling for transit delay information, a volumetric MR imaging approach capturing key DSA information is introduced.

Fig 1.

Representative ASPECTS regions used for scoring of both DSA (A) and ASL data (B); specifically, 2 ACA regions, 6 MCA regions, and 2 posterior cerebral artery regions per side were evaluated.

Fig 2.

Representative DSA data (A), PASL CBF maps (B), and VSASL CBF maps (C) for a preoperative patient with left-sided moyamoya. A, Frontal DSA data from bilateral ICA injections at various postinjection times. The right side appears relatively normal, with early arterial filling and ACA/MCA parenchymal blush at 2.0 seconds. In contrast, the left side demonstrates delayed anterograde filling through a proximal M1 MCA stenosis (red arrowhead), retrograde filling via ACA-MCA collaterals, and delayed parenchymal perfusion of the MCA territory. Parenchymal perfusion of the left MCA territory is finally reached by 4.0 seconds. PASL maps (B) reflect the DSA appearance at 2.0 seconds bilaterally, including areas of curvilinear hyperintensity corresponding to macrovascular flow and perfusion deficit, while VSASL maps (C) reflect parenchymal DSA phases, despite these occurring at different times (2.0 seconds on the right, 4.0 seconds on the left). RICA indicates right ICA injection; LICA, left ICA injection.

Fig 3.

Average PASL and VSASL-CBF CV (a marker of perfusion variability) calculated for patient vascular territories demonstrating delayed-but-complete parenchymal perfusion by DSA, with normal sibling values provided for comparison. Patient VSASL values are similar to those of healthy siblings, consistent with the DSA appearance, but PASL values are markedly different. Error bars denote 95% CI.

Fig 4.

Standard ASL label propagation with patent proximal vessels (A) and steno-occlusive disease with secondary collateralization (B). A, The ASL label travels from the labeling band to the distant microvasculature during the standard PLD, resulting in symmetric, homogeneous gray matter perfusion (C). B, The label is delayed due to slow flow through the stenosis and circuitous collateral pathways. Consequently, the label does not fully reach the distal microvasculture during PLD and remains caught in the macrovasculature, resulting in areas of apparent perfusion deficit and hyperintense arterial transit artifacts (D).