A novel MRI analysis for assessment of microvascular vasomodulation in low-perfusion skeletal muscle

Abstract

Compromised microvascular reactivity underlies many conditions and injuries, but its assessment remains difficult, particularly in low perfusion tissues. In this paper, we develop a new mathematical model for the assessment of vasomodulation in low perfusion settings. A first-order model was developed to approximate changes in T 1 relaxation times as a result of vasomodulation. Healthy adult rats (N = 6) were imaged on a 3-Tesla clinical MRI scanner, and vasoactive response was probed on gadofosveset using hypercapnic gases at 20% and 5% CO 2 to induce vasoconstriction and vasodilation, respectively. MRI included dynamic 3D T 1 mapping and T 1-weighted images during gas challenge; heart rate was continuously monitored. Laser Doppler perfusion measurements were performed to corroborate MRI findings. The model was able to identify hypercapnia-mediated vasoconstriction and vasodilation through the partial derivative T t ∂ ∂ 1. MRI on animals revealed gradual vasoconstriction in the skeletal muscle bed in response to 20% CO 2 followed by gradual vasodilation on transitioning to 5% co 2. These trends were confirmed on laser Doppler perfusion measurements. Our new mathematical model has the potential for detecting microvascular dysfunction that manifests in the early stages across multiple metabolic and ischemic pathologies.

Human microvascular reactivity: a review of vasomodulating stimuli and non-invasive imaging assessment

“…Pairing this approach with gas challenge stimuli allows targeted visualization of vasoreactivity (figure 5) (Ganesh et al 2017). In low perfusion tissue such as skeletal muscle, signal can be augmented through mathematical post-processing (Zakher et al 2020). This emerging T 1 -BPA MRI strategy holds promise for highly specific assessment of MVR.…”