Fig. 1.

Dual-mode optical and ${}^{13}\mathrm{\text{C}}$ MR imaging. (A) Experiment schematic. Diamond particles with centers are imaged with fluorescence under green (520 nm) excitation by a complementary metal oxide semiconductor (CMOS) detector, as well as under ${}^{13}\mathrm{\text{C}}$ MRI through polarization transferred to lattice ${}^{13}\mathrm{\text{C}}$ nuclei from optically polarized electrons. (B) Hyperpolarization and detection protocol. The ${}^{13}\mathrm{\text{C}}$ DNP occurs at low field $\sim$38 mT under MW sweeps across the ESR spectrum. FLASH MR imaging is performed after sample shuttling to 9.4 T. Here echo time TE = 0.5 ms, repetition time TR = 6 ms, acquisition time ${\mathrm{T}}_{\mathrm{\text{acq}}}$ = 0.36 ms. (C) Typical hyperpolarization signal enhancement, showing signal gain $\approx 280\hspace{0.17em}\pm$ 5 against thermal signal at 7 T, corresponding to $\sim$5 orders of magnitude acceleration in MR imaging time. For a fair comparison, the noise in both datasets is normalized to 1 (dashed lines). (D) Ring-shaped phantom filled with 40 mg of 200-$\mathrm{\mu }$m diamond particles employed for dual-mode imaging. (E) Fluorescence image captured through a 630-nm long-pass filter. (F) A ${}^{13}\mathrm{\text{C}}$ MR FLASH image with 16 averages ($\approx$8 s total imaging time) and a square pixel length of 160 $\mathrm{\mu }$m and square FOV with a 6.4-mm edge.