Curve
Figure 4: Curve A is the observable signal and normalized concentration of hyperpolarized succinate over time. Curve B is the observable signal and normalized concentration of hyperpolarized metabolites over time. Each curve is the composite of T1 decay of hyperpolarization, metabolic transformation into hyperpolarized 13C products and losses as a result of radiofrequency pulses necessary for their in vivo detection. The ratio malate/succinate (M/S) or total metabolite/succinate when plotted against time (Curve C) provides an estimate of the minimum rate of accumulation of hyperpolarized 13C into metabolite(s) in the tumor. For details, see text. Partial Krebs cycle rate for RENCA (succinate to citrate/glutamate) was estimated at 5 μmoles/minute/gram (upper curves) and for lymphoma A20 (succinate to malate) at 0.7 μmoles/minute/gram (lower curves).