03 Jun 21. Featured Paper

A comparison of CVR magnitude & delay assessed at 1.5 & 3T in patients with cerebral small vessel disease.

Link to paper on Frontiers in Physiology

Authors

Michael S. Stringer, Gordon W. Blair, Yulu Shi, Iona Hamilton, David A. Dickie, Fergus N. Doubal, Ian M. Marshall, Michael J. Thrippleton, & Joanna M. Wardlaw

Abstract

Background: Cerebrovascular reactivity (CVR) measures blood flow change in response to a vasoactive stimulus.

Impairment is associated with several neurological conditions & can be measured using blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI).

Field strength affects the BOLD signal, but the effect on CVR is unquantified in patient populations.

Methods: We recruited patients with minor ischemic stroke & assessed CVR magnitude & delay time at 3 & 1.5 Tesla using BOLD MRI during a hypercapnic challenge.

We assessed subcortical gray (GM) & white matter (WM) differences using Wilcoxon signed rank tests & scatterplots.

Additionally, we explored associations with demographic factors, WM hyperintensity burden, & small vessel disease score.

Results: Eighteen of twenty patients provided usable data.

At 3T vs. 1.5T: mean CVR magnitude showed less variance (WM 3T: 0.062 ± 0.018%/mmHg, range 0.035, 0.093; 1.5T: 0.057 ± 0.024%/mmHg, range 0.016, 0.094) but was not systematically higher (Wilcoxon signal rank tests, WM: r = −0.33, confidence interval (CI): −0.013, 0.003, p = 0.167); delay showed similar variance (WM 3T: 40 ± 12 s, range: 12, 56; 1.5T: 31 ± 13 s, range 6, 50) & was shorter in GM (r = 0.33, CI: −2, 9, p = 0.164) & longer in WM (r = −0.59, CI: −16, −2, p = 0.010).

Patients with higher disease severity tended to have lower CVR at 1.5 & 3T.

Conclusion: Mean CVR magnitude at 3T was similar to 1.5T but showed less variance.

GM/WM delay differences may be affected by low signal-to-noise ratio among other factors.

Although 3T may reduce variance in CVR magnitude, CVR is readily assessable at 1.5T & reveals comparable associations & trends with disease severity.

Keywords

• BOLD signal
• Cerebrovascular reactivity
• Magnetic resonance imaging
• Small vessel disease
• Stroke