System and method of magnetic resonance imaging

#The present invention relates generally to the field of magnetic resonance imaging.

#Conventional magnetic resonance imaging has spatial imaging resolution of about 1 μm. Motivated by the potential of combining 3D imaging capability of conventional magnetic resonance and the atomic resolution of scanning probe techniques that utilize mechanical cantilevers, a new atomic resolution 3D magnetic resonance imaging technique was introduced. This method, magnetic resonance force microscopy (MRFM), uses a microscopic magnetic particle as a source of atomic scale imaging gradient fields and a mechanical resonator as a sensitive detector of magnetic resonance, as opposed to more conventional inductive techniques. Proof-of-concept demonstrations of MRFM were carried out for various magnetic resonance systems including electron spin resonance, nuclear magnetic resonance, and ferromagnetic resonance.

#However, while MRFM is rapidly progressing by the incorporation of smaller magnetic particles and more sensitive mechanical resonators, current MRFM imaging resolution of ˜1 μm remains at the level of conventional MRI inductive detection. A single nuclear or electron spin has not been successfully detected yet due to significant technical challenges.

#FIG. 1 is a schematic view of a model configuration for magnetic resonance imaging according to a preferred method of the present invention;

#FIG. 2A is a histogram of the number of resonant spin sites of a 3 Angstrom unit cell size simple cubic crystal in the presence of a 100 nm diameter Cobalt ferromagnetic sphere, with an inset showing a model configuration with enhanced contours of constant BZ;

#FIG. 2B is an enlarged view of a portion of the histogram of FIG. 2A;

#The present invention provides a novel method of magnetic resonance imaging. According to the present method of imaging a sample, a magnetic resonance absorption signal is detected using the field from a magnetic particle. The absorption signal has features that are the direct signature of the atomic structure of the sample. Because different sample crystal structures have different spectral features, the technique can be used to study the crystal structure, for example, and chemical environment of the sample by magnetic resonance at the atomic level. The technique can be used in imaging of, as non-limiting examples, large crystals, thin films, or small crystallites. Other, non-crystalline materials are contemplated for imaging, as well.

#The present invention provides a method of imaging using magnetic resonance for imaging a sample in close proximity of a magnetic particle, such as a sphere. A preferred embodiment of the invention includes positioning a small magnetic particle in close vicinity of a sample surface, and applying a large polarizing field and a small radio-frequency field in a specific configuration so that absorption spectra reveals the crystal structure of the sample of interest. More particularly, a magnetic resonance signal is produced due to the presence of the magnetic particle, having a spectrum (or spectra) with sharp spectral peaks dependent on specific magnetic particle and magnetic field configurations. The appearance of the peaks is a direct signature of discrete atomic sites in the crystal lattice. The detection of these peaks may be used for atomic scale magnetic resonance. The positions of the spectral peaks are sensitive to the unit cell size of the sample, thereby providing a method for determination of the basic parameters of the sample at the atomic scale. The magnetic resonance spectra are dependent on the particle size and the angle of the particle magnetization with respect to the sample surface.

#Although the method detects many nuclear or electronic spins at the same time, the present magnetic resonance technique allows sharp spectral features to appear that are a direct signature of the atomic structure. This is a significant distinction from other magnetic resonance techniques that seek to detect single spins, since one can determine the crystal structure even by detecting magnetic resonance from thousands of nuclear or electronic spins.