Hyperpolarized C-13 spectroscopic imaging of the TRAMP mouse at 3T-initial experience

The transgenic adenocarcinoma of mouse prostate (TRAMP) mouse is a well-studied murine model of prostate cancer with histopathology and disease progression that mimic the human disease. To investigate differences in cellular bioenergetics between normal prostate epithelial cells and prostate tumor cells, in vivo MR spectroscopic (MRS) studies with non-proton nuclei, such as (13)C, in the TRAMP model would be extremely useful. The recent development of a method for retaining dynamic nuclear polarization (DNP) in solution permits high signal-to-noise ratio (SNR) (13)C MRI or MRSI data to be obtained following injection of a hyperpolarized (13)C agent. In this transgenic mouse study, this method was applied using a double spin-echo (DSE) pulse sequence with a small-tip-angle excitation RF pulse, hyperbolic-secant refocusing pulses, and a flyback echo-planar readout trajectory for fast (10-14 s) MRSI of (13)C pyruvate (pyr) and its metabolic products at 0.135 cm(3) nominal spatial resolution. Elevated (13)C lactate (lac) was observed in both primary and metastatic tumors, demonstrating the feasibility of studying cellular bioenergetics in vivo with DNP hyperpolarized (13)C MRSI.