Approaches for hyperpolarized noble gas magnetic resonance imaging of rodent lungs

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Hyperpolarized Noble Gases (HNG), specifically helium-3 and xenon-129, have significantly expanded the capability of Magnetic Resonance (MR) imaging in recent years, most notably for visualizing human lung anatomy and function. HNG MR imaging offers several important advantages: (i) safety, (ii) high spatial and temporal resolution and (iii) functional information. A further novel feature of HNG is that the optimal image quality is achieved at magnetic field strengths substantially lower than most conventional MR imaging systems. Low field can reduce MR complexity and costs, allow new "open magnet" geometries for reduced claustrophobia and permit exploration of the effects of posture on lung physiology. Furthermore, the substantially increased transverse relaxation times available at low fields provides a unique opportunity to measure fundamental long-range gas diffusion and rapid oxygenation changes in the lung not possible at high fields. The objectives of the proposed research are: i) to optimize a low field MR imaging system; ii) to develop mathematical models of the relationships between measured low field HNG parameters and the anatomical and physiological properties of the lung (surface area, airway sizes, inflammation and oxygenation); iii) to develop and validate new low field HNG MR imaging methods sensitive to rodent models of lung disease. The proposed research will take place at the low field hyperpolarized MR imaging laboratory at the University of Western Ontario (Robarts Research Institute) established in part with previous NSERC Discovery funding. The research plan will bring together the expertise of the low field hyperpolarized MR imaging laboratory in the production and delivery of HNG in vivo, hardware and software development and mathematical modeling with the expertise of the Physics Department at UWO in pulsed-field MR hardware and the expertise of the UWO School of Medicine and Dentistry in the development of experimental models of lung disease in rodents. The significance of the proposed research is high as low field HNG MRI is entirely novel and therefore will provide significant opportunities for knowledge generation, both basic and applied.