High resolution hyperpolarized C MRSI using SPICE at 9.4T.

PURPOSE

To test the feasibility of using the SPICE (SPectroscopic Imaging by exploiting spatiospectral CorrElation) technique, which uses the partial separability of spectroscopic data, for high resolution hyperpolarized (HP) C spectroscopic imaging.

METHODS

Numerical simulations were performed to investigate the impact of transient HP signals on SPICE reconstruction. Furthermore, spectroscopic imaging exams from SPICE and conventional EPSI (echo-planar spectroscopic imaging) were simulated for comparison. For in vivo experiments, HP C SPICE was performed in a mouse kidney by means of the injection of HP [1- C] pyruvate at 9.4T.

RESULTS

The variation of lactate/pyruvate from the simulated SPICE was less than 4% under various factors that affect the transient HP signal, suggesting that the impact is negligible. We found that while HP C EPSI was limited to the low signal-to-noise ratio (SNR) of lactate, these limitations were mitigated through HP C SPICE, facilitating the improved SNR of lactate and the distinction of tissues. Acquisition of a high resolution HP C spectroscopic image was possible for the in vivo experiments. With the fine structural information, the acquired image showed higher signal of pyruvate and lactate in the renal cortices than in the medullas, which is known to be attributed to higher activity of lactate dehydrogenase.

CONCLUSION

The feasibility of HP C SPICE was investigated. Simulation studies were conducted and in vivo experiments were performed in the mouse kidney at 9.4T. Results confirmed that a high resolution HP C spectroscopic image with adequate spectral resolution can be obtained. Magn Reson Med 80:703-710, 2018. © 2018 International Society for Magnetic Resonance in Medicine.