Metabolic imaging in the anesthetized rat brain using hyperpolarized [1-13C] pyruvate and [1-13C] ethyl pyruvate

Formulation, polarization, and dissolution conditions were developed to obtain a stablehyperpolarized solution of [1- 13 C]-ethyl pyruvate. A maximum tolerated concentration andinjection rate were determined, and 13 C spectroscopic imaging was used to compare the uptake ofhyperpolarized [1- 13 C]-ethyl pyruvate relative to hyperpolarized [1- 13 C]-pyruvate intoanesthetized rat brain. Hyperpolarized [1- 13 C]-ethyl pyruvate and [1- 13 C]-pyruvate metabolicimaging in normal brain is demonstrated and quantified in this feasibility and range-finding study. Keywords hyperpolarized; carbon-13; ethyl-pyruvate; brain; pyruvate; lactateMR metabolic imaging of hyperpolarized [1- 13 C]-pyruvate has proven to be useful,especially in oncology and cardiology (1,2). Dynamic and tissue level changes in [1- 13 C]-pyruvate and its metabolic products, [1- 13 C]-lactate, [1- 13 C]-alanine, and [ 13 C] bicarbonate,have been shown to correlate with metabolic states of interest, including disease progression(3,4) and response to therapy (5,6). However, for potential neurologic applications, theblood-brain transport of pyruvate may be a limiting factor. Age, anesthesia, and dietary statecan all impact transport rates (7–9), and under some conditions, the 1- to 2-min window ofuseful hyperpolarized [1