Magnetic microstructures for magnetic resonance imaging
Inventors
Zabow, Gary • Dodd, Stephen • Koretsky, Alan • Moreland, John
Assignees
United States Department of Commerce • US Department of Health and Human Services
Publication Number
US-10188755-B2
Publication Date
2019-01-29
Expiration Date
2029-04-20
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Abstract
The present invention relates to a magnetic resonance structure with a cavity or a reserved space that provides contrast and the additional ability to frequency-shift the spectral signature of the NMR-susceptible nuclei such as water protons by a discrete and controllable characteristic frequency shift that is unique to each MRS design. The invention also relates to nearly uniform solid magnetic resonance T2* contrast agents that have a significantly higher magnetic moment compared to similarly-sized existing MRI contrast agents.
Core Innovation
The invention relates to magnetic resonance structures (MRS) that include a cavity or reserved space providing contrast and a discrete, controllable frequency shift of the spectral signature of NMR-susceptible nuclei such as water protons. This frequency shift is unique to each MRS design and is generated by an essentially uniform magnetic field within the reserved space. The MRS can be engineered using precise geometries to produce these frequency shifts used for both contrast and identification within magnetic resonance imaging (MRI).
The invention addresses the limitations of existing MRI contrast agents, such as superparamagnetic iron oxide nanoparticles (SPIO) and microparticles of iron oxide (MPIO), which produce continuous spatial decays in magnetic fields. These continuous fields result in broadened spectral lines that obscure distinctions between different types of magnetic particles, thus providing only monochrome contrast. Consequently, existing agents prevent routine in vivo tracking of single cells and lack multiplexing capabilities to distinguish different cell types at a single-cell level.
The invention introduces magnetic resonance structures with reserved spaces that generate substantially uniform magnetic fields significantly different from background fields, enabling discrete and controllable frequency shifts. The reserved space permits NMR-susceptible nuclei such as water protons to diffuse or flow through, amplifying the volume of frequency-shifted fluid and enhancing signal strength. This enables lower concentrations of contrast agents compared to prior art, improved ability to distinguish multiple MR structures simultaneously, and the potential for super-resolution tracking.
Claims Coverage
The patent includes one independent apparatus claim and one independent method claim, covering novel magnetic resonance contrast agents and their use in imaging.
Magnetic resonance contrast agent with hollow cylindrical magnetic structure
A contrast agent composed of one or more substantially cylindrical magnetic structures with length-to-diameter ratio between 0.8 and 1.6, each having a hollow region producing a spatially extended, substantially homogeneous magnetic field within a near-field region. This produces a characteristic Larmor frequency causing a characteristic magnetic resonance signal.
Method of magnetic resonance imaging using the cylindrical contrast agent
A method involving providing the disclosed magnetic resonance contrast agent dispersed in a medium, illuminating it with an excitatory electromagnetic pulse, and detecting emitted electromagnetic radiation with a detection system to produce magnetic resonance imaging data.
The claims together define a novel magnetic resonance agent with hollow cylindrical geometry generating substantially uniform magnetic fields in their reserved spaces, and methods for using them in MRI to produce characteristic spectral signals enabling enhanced contrast and identification.
Stated Advantages
The MRS provide frequency-shifted magnetic resonance contrast as well as conventional T2* contrast, with improved efficacy over existing agents.
The reserved space and uniform magnetic field allow distinct, controllable spectral signatures, enabling multiplexed MR imaging and enhanced informational content such as color mapping.
The diffusion of fluid in and out of the reserved space amplifies the volume of frequency-shifted nuclei, improving contrast signal strength and reducing required contrast agent concentrations.
Top-down fabrication methods produce MRS with high uniformity in size and composition, enabling super-resolution tracking and precise quantitative analysis.
High magnetic moment materials can be used to create contrast agents with stronger magnetic moments than existing agents, improving sensitivity and reducing required dose.
Documented Applications
Magnetic resonance frequency shifting of water protons and other NMR-susceptible nuclei for MRI calibration, testing, or fabrication.
Magnetic resonance spatial calibration markers to provide high-resolution spatial calibration in MRI.
Specific detection, labeling, and tracking of biological cells via functionalized MRS particles for multiplexed cell identification.
Distance, pressure, vibration, or torque sensors by exploiting geometry-dependent frequency shift changes of MRS.
Magnetic separation of materials using the magnetic properties of the MRS particles.
Magnetically driven rotary micropumps and micromixers using rotation of anisotropic MRS under rotating fields.
Localized RF magnetic heating elements for targeted thermal ablation of biological cells.
Flow cytometry and spin-tagging fluid flow and perfusion imaging using MRS arranged around or within vessels for noninvasive flow visualization and measurement.
Monitoring blood flow and condition of stent devices by incorporating MRS structures with reserved spaces in stents.
Magnetic field sensors and arrays for visual measurement of magnetic field gradients using MRS with different frequency shifts.
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