Tao Xu1, Dirk Mayer2,3, Meng Gu2, Yi-Fen Yen4, Sonal Josan2,3, Edvin Johansson5, Jim Tropp6, Ralph Hurd4, Daniel Spielman, 12
1Department of Electrical Engineering, Stanford University, Stanford, CA, United States; 2Department of Radiology, Stanford University, Stanford, CA, United States; 3Neuroscience Program, SRI International, Menlo Park, CA, United States; 4Global Applied Sciences Laboratory, GE Healthcare, Menlo Park, CA, United States; 5Medical Diagnostics R&D, GE Healthcare, Oslo, Norway; 6Global Applied Sciences Laboratory, GE Healthcare, Fremont, CA, United States
Hyperpolarized MRSI of metabolically active substrates allows the study of both the injected substrate and downstream metabolic products in vivo. Although hyperpolarized 13C-pyruvate has been used to demonstrate metabolic activity, robust quantitation remains an important area of investigation. Most metrics proposed to date fail to capture enzyme saturation effects. In addition, the widely used small flip-angle excitation approach doesnt model the inflow of fresh spins correctly. We developed a quantitative 90-excitation dynamic spectroscopic imaging approach, and demonstrated that the in-vivo conversion of pyruvate is well approximated by Michaelis-Menten kinetics with resulting estimated parameters being unbiased with respect to experimental conditions.