| Metadata | Details |
|---|
| Publication Date | 2022-04-11 |
| Journal | Berkeley Scientific Journal |
| Authors | Andrew Delaney, Lexie Ewer, Esther Lim |
| Institutions | Berkeley College, University of California, Berkeley |
| Analysis | Full AI Review Included |
- Core Value Proposition: Development of a âdual-mode imagingâ technique combining the high spatial resolution of optical imaging with the deep tissue penetration and high contrast of Magnetic Resonance Imaging (MRI).
- Methodology: Achieved hyperpolarizationâaligning nuclear spins without a strong magnetic fieldâby shining laser light onto Nitrogen Vacancy (NV) centers within 13C-enriched diamond microparticles.
- Signal Enhancement: Demonstrated a massive increase in MRI signal, achieving polarization levels approaching a million-fold greater than standard thermal polarization in conventional magnets.
- Engineering Impact: This technology allows for high-sensitivity MRI using low-field, low-cost magnets (e.g., ~40 mT), circumventing the need for expensive, large, high-Tesla superconducting magnets (1.5 T to 20 T).
- Resolution Improvement: The signal increase allows for a proportional increase in spatial resolution, pushing MRI capabilities from the current millimeter scale toward the molecular scale.
- Quantum Applications: The hyperpolarized nuclear spins in defective diamonds exhibit exceptional coherence (exceeding 1000 oscillations), making them valuable resources for quantum sensing and fundamental physics research.
- Medical Potential: Enables the use of hyperpolarized molecular markers (e.g., pyruvate) for highly selective imaging of metabolism, potentially allowing for early-stage cancer diagnosis.
| Parameter | Value | Unit | Context |
|---|
| Hyperpolarization Enhancement | ~1,000,000 | Factor | Relative increase in spin alignment compared to normal magnetic field polarization. |
| Hyperpolarization Field (Bpol) | ~40 | mT | Magnetic field used during laser-assisted hyperpolarization (Figure 1). |
| Clinical MRI Field Range | 1.5 to 3 | T | Standard magnetic fields used in current medical imaging. |
| High-End Research MRI Field | 7 | T | Magnet used for comparison in hyperpolarization experiments (Figure 1). |
| Maximum Theoretical MRI Field | 20 | T | Limit mentioned due to cost, size, and physiological effects on humans. |
| Current MRI Resolution | Millimeter to centimeter | Length scale | Standard spatial resolution for whole-body imaging. |
| Optical Imaging Resolution Limit | Half a micron (0.5 ”m) | Length scale | Resolution limit set by the wavelength of light (Rayleigh limit). |
| Nuclear Spin Coherence Lifetime | >90 | s | Achieved in related bulk hyperpolarized solid experiments (Ref 2). |
| Nuclear Spin Coherence | >1000 | Oscillations | Observed coherence of defective diamond nuclear spins. |
| Imaging Material | 13C Diamond | Microparticles | Material used as the fluorescent and hyperpolarized tag. |
- Material Synthesis and Selection: Utilizing diamond microparticles that are enriched with 13C nuclei and engineered to contain Nitrogen Vacancy (NV) centers. NV centers are point defects (a nitrogen atom adjacent to a lattice vacancy) that facilitate spin manipulation.
- Laser-Assisted Hyperpolarization: Applying laser light (e.g., green wavelength) to the NV centers in the diamond material. This optical excitation aligns the electron spins of the NV centers.
- Spin Alignment Transfer: Transferring the high degree of spin alignment from the NV electron spins to the neighboring 13C nuclear spins within the diamond lattice, achieving hyperpolarization.
- Dual-Mode Imaging Acquisition:
- Optical Imaging: Using the intrinsic red fluorescence emitted by the NV centers when excited by the laser to rapidly locate and image the particles in real space, providing high spatial resolution.
- MRI Acquisition: Utilizing the highly polarized 13C nuclear spins to generate a strong magnetic resonance signal. MRI data is acquired in k-space (Fourier reciprocal space).
- Image Reconstruction and Enhancement: Applying a Fourier transform to the k-space MRI data to reconstruct the final image in real space. The high polarization significantly boosts the signal-to-noise ratio (SNR).
- Background Suppression: Implementing background subtraction techniques (as demonstrated using Alexa dye and 13C Methanol phantoms) to isolate the signal originating exclusively from the hyperpolarized diamond particles, increasing image contrast.
- Analyte Polarization (Future Direction): Developing porous diamond scaffolds (sponges) to flow analytes (like water or CO2) through, transferring the hyperpolarization from the diamond to the analyte molecules for subsequent enhanced imaging.
- Advanced Medical Imaging:
- Early Cancer Detection: Using hyperpolarized molecular markers (e.g., pyruvate) to image cellular metabolism, allowing for the detection of cancer at earlier stages than current methods.
- Deep Tissue Diagnostics: Enabling high-resolution MRI deep within scattering media (bone, blood, fatty tissue) where optical imaging fails.
- Radiation-Free Screening: Leveraging MRIâs radiation-free nature combined with enhanced sensitivity for safer, more frequent diagnostic scans.
- Quantum Technology and Sensing:
- Quantum Simulation/Computing: Utilizing the highly coherent nuclear spins in defective diamonds as fundamental quantum mechanical objects for developing quantum information science resources.
- Chemical Sensing Probes: Creating nanoscale NMR spectroscopy probes that can be inserted into cells or tissues to provide chemically specific information (a âfingerprintâ) about the surrounding molecular environment.
- Pharmaceutical and Chemical Analysis:
- Enhanced NMR Spectroscopy: Using hyperpolarization to boost the signal of target molecules in chemical and biological samples, speeding up analysis and improving detection limits.
- Low-Field MRI Systems: Developing compact, low-cost MRI machines suitable for point-of-care diagnostics by eliminating the requirement for massive, high-Tesla superconducting magnets.
View Original Abstract
His research team focuses on utilizing physical chemistry to develop âquantum-enhancedâ NMR and MRI technologies, pushing past the current resolution and signal limitations.Beyond his research, Dr. Ajoy is very enthusiastic about his students and emphasizes the importance of the contributions made by his graduate and undergraduate researchers.Having become a professor during the SARS-CoV-2 pandemic, he is especially grateful for his students and expressed that the multiple papers published by his lab are due to the hard work of everyone on his team.Sophie Conti, one of Dr. Ajoyâs research assistants who works on the nitrogen vacancy center magnetometry in microfluidics project, said of the Ajoy lab, âIâve really loved working in the Ajoy lab thus far because of the supportive community and amazing opportunities for learning.I think our lab is really unique in that undergraduates are really encouraged and supported by the other lab members to further their own learning and research if it interests them.â In this interview, we explore how the use of diamond microparticles can enhance MRI and optical imaging, resulting in a form of dual imaging that has revolutionary impacts for the fields of medicine, biology, and the physical sciences.