A non-invasive magnetic resonance imaging approach for assessment of real-time microcirculation dynamics

• Published in: Scientific reports Vol. 7; no. 1; pp. 7468 - 11
• Main Authors: Ganesh, Tameshwar, Estrada, Marvin, Yeger, Herman, Duffin, James, Cheng, Hai-Ling Margaret
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 07.08.2017; Nature Publishing Group; Nature Portfolio
• Subjects: 59/57; 631/1647/245/1628; 631/443/1338/1872; Animals; Blood; Blood Volume; Gadolinium - chemistry; Heart Rate; Humanities and Social Sciences; Hypercapnia; Hypoxia; Kidney Cortex - blood supply; Kidney Cortex - diagnostic imaging; Kidneys; Laser-Doppler Flowmetry; Liver; Liver - blood supply; Liver - diagnostic imaging; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Microcirculation; Microvasculature; multidisciplinary; Neuroimaging; NMR; Nuclear magnetic resonance; Organometallic Compounds - chemistry; Oxygen - metabolism; Paraspinal Muscles - blood supply; Paraspinal Muscles - diagnostic imaging; Perfusion; Rats; Renal cortex; Rodents; Science; Science (multidisciplinary); Vasoactive agents; Vasoconstriction; Vasodilation
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-06983-6

We present a novel, non-invasive magnetic resonance imaging (MRI) technique to assess real-time dynamic vasomodulation of the microvascular bed. Unlike existing perfusion imaging techniques, our method is sensitive only to blood volume and not flow velocity. Using graded gas challenges and a long-life, blood-pool T 1 -reducing agent gadofosveset, we can sensitively assess microvascular volume response in the liver, kidney cortex, and paraspinal muscle to vasoactive stimuli (i.e. hypercapnia, hypoxia, and hypercapnic hypoxia). Healthy adult rats were imaged on a 3 Tesla scanner and cycled through 10-minute gas intervals to elicit vasoconstriction followed by vasodilatation. Quantitative T 1 relaxation time mapping was performed dynamically; heart rate and blood oxygen saturation were continuously monitored. Laser Doppler perfusion measurements confirmed MRI findings: dynamic changes in T 1 corresponded with perfusion changes to graded gas challenges. Our new technique uncovered differential microvascular response to gas stimuli in different organs: for example, mild hypercapnia vasodilates the kidney cortex but constricts muscle vasculature. Finally, we present a gas challenge protocol that produces a consistent vasoactive response and can be used to assess vasomodulatory capacity. Our imaging approach to monitor real-time vasomodulation may be extended to other imaging modalities and is valuable for investigating diseases where microvascular health is compromised.