A ¹³C/³¹P surface coil to visualize metabolism and energetics in the rodent brain at 3 Tesla

We constructed a ¹³C/³¹P surface coil at 3 T for studying cancer metabolism and bioenergetics. In a single scan session, hyperpolarized ¹³C-pyruvate MRS and ³¹P MRS was carried out for a healthy rat brain.

All experiments were carried out at 3 Tesla. The multinuclear surface coil was designed as two coplanar loops each tuned to either the ¹³C or ³¹P operating frequency with an LCC trap on the ¹³C loop. A commercial volume proton coil was used for anatomical localization and B₀ shimming. Single tuned coils operating at either the ¹³C or ³¹P frequency were built to evaluate the relative performance of the multinuclear coil. Coil performance metrics consisted of measuring Q factor ratio, calculating system input power using a single-pulse acquisition, and acquiring SNR and flip angle maps using 2D CSI sequences. To observe in vivo spectra, a bolus of hyperpolarized [1-¹³C] pyruvate was administered via tail vein. In vivo¹³C and endogenous ³¹P spectra were obtained in a single scan session using 1D slice selective acquisitions.

When compared with single tuned surface coils, the multinuclear coil performance showed a decrease in Q factor ratio, SNR, and transmit efficiency. Flip angle maps showed adequate flip angles within the phantom when the transmit voltage was set using an external phantom. Results show good detection of ¹³C labeled lactate, alanine, and bicarbonate in addition to ATP from ³¹P MRS.

The coil enables obtaining complementary information within a scan session, thus reducing the number of trials and minimizing biological variability for studies of metabolism and bioenergetics.