Creating a clinical platform for carbon-13 studies using the sodium-23 and proton resonances.

PURPOSE

Calibration of hyperpolarized C-MRI is limited by the low signal from endogenous carbon-containing molecules and consequently requires C-enriched external phantoms. This study investigated the feasibility of using either Na-MRI or H-MRI to calibrate the C excitation.

METHODS

Commercial C-coils were used to estimate the transmit gain and center frequency for C and Na resonances. Simulations of the transmit B profile of a Helmholtz loop were performed. Noise correlation was measured for both nuclei. A retrospective analysis of human data assessing the use of the H resonance to predict [1- C]pyruvate center frequency was also performed. In vivo experiments were undertaken in the lower limbs of 6 pigs following injection of hyperpolarized C-pyruvate.

RESULTS

The difference in center frequencies and transmit gain between tissue Na and [1- C]pyruvate was reproducible, with a mean scale factor of 1.05179 ± 0.00001 and 10.4 ± 0.2 dB, respectively. Utilizing the H water peak, it was possible to retrospectively predict the C-pyruvate center frequency with a standard deviation of only 11 Hz sufficient for spectral-spatial excitation-based studies.

CONCLUSION

We demonstrate the feasibility of using the Na and H resonances to calibrate the C transmit B using commercially available C-coils. The method provides a simple approach for in vivo calibration and could improve clinical workflow.