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.