Resonant magnetic susceptibility imaging (ReMSI)

System for providing a multi-dimensional image representation of spatial variations of magnetic susceptibility of a body including a paramagnetic or a diamagnetic substance, comprising:

• a first generator for generating an excitation field in the body to polarize paramagnetic or diamagnetic substances within the body such that said polarization creates a local magnetic field in voxels of the body according to the magnetic susceptibility of each voxel,
• a second generator for generating a primary electromagnetic radiation field in the body to induce a secondary radiation field to emanate from the body, each voxel of the body contributing to said secondary radiation field at a frequency determined by the magnetic susceptibility of said voxel,
• a detector positioned to receive one of said fields for producing an output signal in response to said secondary radiation field, and
• a processor for receiving and processing the output signal of said detector to create the multi-dimensional image.

System for providing a multi-dimensional image representation of spatial variations of magnetic susceptibility of a body having at least one type of nuclei with non-zero spin, and a paramagnetic or a diamagnetic substance, comprising:

• a first generator for generating an excitation field in the body to polarize the paramagnetic or the diamagnetic substances such that said polarization creates a local excitation field in the body, said local excitation field generating a shift in the Larmor frequency of nuclei in the body,
• a second generator for generating a primary radio frequency field in the body to create a transverse magnetization of the nuclei,
• a detector for producing output signals in response to detecting a component of a secondary radio frequency field generated by the polarized nuclei, and
• a reconstruction processor for receiving the output signals of said detector to create the multi-dimensional image.

System for generating a three-dimensional magnetic susceptibility map of a body, comprising:

• means for producing a magnetic field for magnetizing the body;
• means for measuring the magnetic field in a volume to be occupied by the body;
• a radiation generator and a transmitter for producing a primary electromagnetic radiation field for causing the body to produce a secondary radiation field by excitation;
• a three-dimensional or planar array of detectors movable in a direction perpendicular to the plane of the detectors for producing output signals by spatially sampling a selected component of said secondary radiation field over a three-dimensional volume at least at the Nyquist rate;
• an analog to digital converter for digitizing said output signals;
• a Fourier transform stage for converting the output signals of the detectors acquired over a period of time into frequency spectra;
• and
• a processor for converting the frequency spectra into a map of magnetic moments in the volume and for converting the magnetic moment map into a three-dimensional magnetic susceptibility map.

A method for providing a multi-dimensional magnetic susceptibility image of a body, comprising the steps of

• measuring a magnetic field component in a volume to be occupied by the body,
• applying a first radiation field having the magnetic field component to the body to magnetize the body,
• applying an electromagnetic second radiation field to the body when disposed in the magnetic field to produce a third radiation field emanating from the body,
• detecting the third radiation field emanating from the body, and,
• producing the magnetic susceptibility image of the body from said detected third radiation field.

A method for providing a multi-dimensional image representation of the spatial variations of magnetic susceptibility of a body having a paramagnetic or a diamagnetic substance, comprising the steps of

• generating an excitation field in the body to polarize the paramagnetic or the diamagnetic substance to create local magnetic fields in voxels in the body according to the magnetic susceptibility of each voxel,
• generating an electromagnetic primary radiation field in the body to induce a secondary radiation field from the body, each voxel of the body contributing to said secondary radiation field at a frequency determined by the magnetic susceptibility of said voxel,
• generating an output signal in response to said secondary radiation field and indicative of said radiation field, and
• creating the multi-dimensional susceptibility image from said output signal.

A method for generating a three-dimensional magnetic susceptibility map of a body, comprising the steps of

• producing a magnetic field for magnetizing the body,
• measuring the magnetic field in a volume to be occupied by the body,
• producing an electromagnetic primary radiation field for causing the body to produce a secondary radiation field by excitation,
• disposing a three-dimensional or planar array of detectors external to said body, said three-dimensional or planar array of detectors being movable in a direction perpendicular to the plane of the detectors for producing output signals by spatially sampling a selected component of said secondary radiation field over a three-dimensional volume at least at a Nyquist frequency, and
• producing the magnetic susceptibility image of the body from said sampled selected component of said secondary radiation field.

A method for generating a three-dimensional magnetic susceptibility map of a body, comprising the steps of

• producing a magnetic field for magnetizing the body,
• measuring the magnetic field in a volume to be occupied by the body,
• producing an electromagnetic primary radiation field for causing the body to produce a secondary radiation field by excitation,
• disposing an array of detectors external to said body, said array of detectors being three-dimensional or movable in a direction perpendicular to the detectors for producing output signals by spatially sampling a selected component of said secondary radiation field over a three-dimensional volume at least at a Nyquist rate,
• digitizing said output signals,
• converting said output signals acquired over a period of time into frequency spectra,
• converting said frequency spectra into a map of magnetic moments in the volume and converting the magnetic moment map into a three-dimensional magnetic susceptibility map of the body.

A method for providing a multi-dimensional image representation of spatial variations of the magnetic susceptibility of a body, comprising the steps of:

• providing a primary magnetic field to magnetize said body,
• measuring said primary magnetic field in a volume to be occupied by said body,
• applying a primary radio frequency field to said body to rotate at least one type of magnetic moments in said body by 90 degrees such that said rotated moments point in a direction transverse to said primary magnetic field,
• detecting a secondary radio frequency field produced by a free induction decay of said rotated magnetic moments by a plurality of detectors arranged in a plane and movable in a direction perpendicular to said plane,
• obtaining Fourier transform of said secondary radio frequency to derive Larmor frequencies of said rotated magnetic moments,
• determining the magnetic moment corresponding to each Larmor frequency,
• determining maximum intensity of each Larmor frequency at positions of said detectors, and
• constructing the multi-dimensional susceptibility image according to said derived Larmor frequencies and according to spatial variations of said secondary radio frequency field.

A method for determining a correspondence between detected voltages in an array of detectors to a radiation distributed within a body, comprising the steps of:

• applying a magnetic field to the body,
• applying an electromagnetic first radiation field to the body to cause the body to cause a radiation distribution within the body,
• detecting the radiation distribution within the body with an array of detectors, and
• determining the correspondence between voltages of the array and the radiation distribution such a set of detected voltages corresponds to a unique radiation distribution within the body.