Lin Z. Li1, 2, Stephen Kadlececk1, Ben Pullinger1, He N. Xu1, Dania Daye3, 4, Lewis Chodosh3, Rahim Rizi1
1Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States; 2Britton Chance Lab of Redox Imaging, Johnson Research Foundation, University of Pennsylvania, Philadelphia, PA, United States; 3Department of Cancer Biology, University of Pennsylvania, Philadelphia, PA, United States; 4Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, United States
Various modeling methods have been used to analyze in vivo hyperpolarized 13C-NMR data from the lactate dehydrogenase (LDH) reaction, which converts pyruvate to lactate. However, these models make certain assumptions about transport in the blood, across cell membranes, and/or enzymatic kinetics, and require at least 3 modeling parameters. Here we present a new method which relaxes some of these assumptions and minimizes the modeling parameters. By fitting the lactate/pyruvate ratio in mouse tumor models we quantify both the forward and reverse exchange rate constants of the LDH reaction. First order temporal derivatives of the lactate/pyruvate ratio help to determine the proper time range for fitting.