Figure 7.

High resolution ¹³C-NMR spectra of hyperpolarized (black) thermally polarized (blue) 1-¹³C-PA (sample 5 in the table) measured at 1 T. The hyperpolarized signal was measured in a single scan (NS^DNP = 1) after approx. 17 s after dissolution ($\alpha$ = 5°, p_w = 3.05 µs, p_a = − 5.6 dB). The thermally polarized signal was acquired adding 4 vol% Gd contrast agent ($\alpha$ = 20°, p_w = 12.20 µs, p_a = − 5.6 dB, S^DNP = 39.5 a.u.). The resulting signal enhancement to S^DNP was 310 × 10⁶ (Eq. 8), and the polarization = 43% (Eqs. 9, 10). The thermal spectrum measured was multiplied by 50,000 to fit in the scale.