High contrast dual-mode optical and 13C magnetic resonance imaging in diamond particles

Abstract

Multichannel imaging -the ability to acquire images of an object through more than one imaging mode simultaneously -has opened exciting new avenues in several areas from astronomy to biomedicine. Visible optics and magnetic resonance imaging (MRI) offer complimentary advantages of resolution, speed and depth of penetration, and as such would be attractive in combination. In this paper, we take first steps towards marrying together optical and MR imaging in a class of biocompatible and deployable particulate materials constructed out of diamond. The particles are endowed with a high density of quantum defects (Nitrogen Vacancy centers) that under optical excitation fluoresce brightly in the visible, but also concurrently electron spin polarize, allowing the hyperpolarization of lattice 13 C nuclei to make the particles over three-orders of magnitude brighter than in conventional MRI. We highlight additional benefits in background-free imaging, demonstrating lock-in suppression by factors of 2 and 5 in optical and MR domains respectively, although ultimate limits are at least two orders of magnitude in each domain. Finally, leveraging the ability of optical and MR imaging to simultaneously probe Fourier-reciprocal domains (real and k-space), we elucidate the ability to employ hybrid sub-sampling in both conjugate spaces to vastly accelerate dual-image acquisition, by as much as two orders of magnitude in practically relevant sparse-imaging scenarios. Our work portends new avenues for quantum-enhanced dualmode imaging platforms and opens possibilities for new therapeutic avenues including in low-field MRI-guided endoscopy.

Rapidly enhanced spin polarization injection in an optically pumped spin ratchet

“…Finally, the rapidly injected spin polarization here projects onto applications that exploit hyperpolarized 13 C spins as quantum sensors [29], leveraging their long lifetimes in the laboratory [35,70] and rotating frames [42,43]. This includes magnetometers [29,51], gyroscopes [27,65,71], sensors for dark-matter searches [72,73], and as RF imaging agents [74].…”

High temperature annealing enhanced diamond 13C hyperpolarization at room temperature

“…1A demonstrates small 18µm microparticles having large nuclear polarization levels ≈0.23% in just under a minute of optical pumping. This corresponds to a gain of ∼230 over their Boltzmann polarization at high field (7T) (4×10 5 over a polarizing field of 38mT), and to a million-fold time acceleration of imaging these particles in MR imaging [19].…”

“…The optical pumping leads to an associated, simultaneous, bright fluorescence from the NVspins that is non-blinking and non-bleaching. Harnessing the dual-mode bright nature of these particles in both the optical as well as MR domains opens new avenues for them to serve as imaging agents in disease diagnosis and monitoring [19,20]. Moreover, nanodiamond particles inherently possess large surface areas (∼57m 2 /g for 100nm particles [21]), and along with the long lifetimes of the 13 C spins, allow hyperpolarized surface 13 C nuclei to serve as spin polarization relay channels to external nuclear spins.…”

“…Spectra recorded in the half-field (g = 4) region allow reliable quantification of NV -(W15) triplet centers, tracking EPR lines originating from forbidden (∆m s = 2) transitions between triplet state Zeeman levels. Fluence (e -/cm 2 ) (x10 19 ) 0. increasing electron fluence leads to the growth of g = 4.274(5) NVcenter signals; and while at low fluences (5×10 8 e/cm 2 ), the NVs dominate the spectrum, higher fluences are associated with the appearance and strengthening of additional signals, here attributable to W16-W18 and W33 triplet defect centers. We emphasize that for clarity, the spectra in Fig.…”

“…We target a HTA condition between 1700-1800 • C (dashed lines). (B) EPR spectra at high electron dose (D2= 5×10 19 e/cm 2 ), displaying NVcenters and spectrally closeby paramagnetic impurities (W33) centers (see also [29]). HTA (red) suppresses the W33 and W16-W18 centers in its conventionally annealed counterpart (black).…”