Hyperpolarized Nanodiamond for Magnetic Resonance Imaging

This thesis describes a new MRI contrast agent based on hyperpolarized 13C in nanodiamond. Nanodiamonds are readily available, non-toxic, can be surface functionalized, and have long T1 relaxation times. Electronic defects in the nanodiamonds are used to hyperpolarize the 13C nuclear spins through dynamic nuclear polarization, building up large nuclear magnetic resonance signals that persist for a long time. Enhancements are comparable to those used in liquid state hyperpolarization experiments, and can be detected in an MRI scan with low background signal. This imaging modality encompasses no ionizing radiation, and long imaging windows stemming from the long T1 relaxation times of solids

Nanodiamond-enhanced MRI via in situ hyperpolarization

Nanodiamonds are of interest as nontoxic substrates for targeted drug delivery and as highly biostable fluorescent markers for cellular tracking. Beyond optical techniques, however, options for noninvasive imaging of nanodiamonds in vivo are severely limited. Here, we demonstrate that the Overhauser effect, a proton–electron polarization transfer technique, can enable high-contrast magnetic resonance imaging (MRI) of nanodiamonds in water at room temperature and ultra-low magnetic field. The technique transfers spin polarization from paramagnetic impurities at nanodiamond surfaces to 1H spins in the surrounding water solution, creating MRI contrast on-demand. We examine the conditions required for maximum enhancement as well as the ultimate sensitivity of the technique. The ability to perform continuous in situ hyperpolarization via the Overhauser mechanism, in combination with the excellent in vivo stability of nanodiamond, raises the possibility of performing noninvasive in vivo tracking of nanodiamond over indefinitely long periods of time