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Abstract #1650

T1 & T2* Responses to Hypercapnic & Hyperoxic Gases in Normal Tissue Are Independent of the Order of Gas Delivery

Jeff D. Winter1,2, Marvin Estrada1, Hai-Ling Margaret Margaret Cheng1,3

1Physiology & Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada; 2Research & Development, IMRIS, Winnipeg, Manitoba, Canada; 3Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

Quantitative MRI measures of T1 and T2* offer noninvasive means to indirectly monitor tissue O2. This study characterized T1 and T2* responses to randomized hypercapnic and hyperoxic gas challenges in normal rabbit liver, kidney and paraspinal muscle in comparison with pilot invasive tissue O2 and perfusion changes. All between-gas ΔT1 and ΔT2* transitions exhibited expected trends, especially in liver and kidney. However, T1 changes were much less predictable. Invasive measures demonstrated consistent trends in tissue perfusion and oxygenation but considerable variability. In summary, we demonstrated independence of T1 and T2* transitions on gas order, and organ-specific pO2 and perfusion dynamics.