Albert P. Chen1, Ralph E. Hurd2, Marie A. Schroeder3,4, Angus Z. Lau4,5, Yi-Ping Gu4, Wilfred W. Lam4, Charles H. Cunningham4,5
1GE Healthcare, Toronto, ON, Canada; 2GE Healthcare, Menlo Park, CA, United States; 3Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, United Kingdom; 4Imaging Research, Sunnybrook Health Sciences Centre, Toronto, ON, Canada; 5Deptartment of Medical Biophysics, University of Toronto, Toronto, ON, Canada
To improve the robustness of pH measurement using hyperpolarized H13CO3- and 13CO2 signals in presence of carbonic anhydrase activity, the 13CO2 resonance was excited independently with a chemically selective RF pulse of larger tip-angle (to achieve higher SNR), while the other resonances of interest were acquired with a smaller tip angle. Accurate pH measurement could still be obtained even with repeated tipping (for temporally and/or spatially resolved data), since the ratio between the two pools was rapidly restored by the enzyme mediated exchange. This method was demonstrated in phantom and in vivo in pig heart.