# US 11,304,653 B2 · Magnetic resonance imaging system with a rotatable magnet

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,304,653 B2
- Document ID: US11304653B2
- Status: Granted
- Kind: B2
- Application number: 17/101,539
- Filed: 2020-11-23
- Published: 2021-05-27
- Granted: 2022-04-19
- Earliest claimed: 2019-11-27
- Assignees: Siemens Healthcare GmbH
- Applicants: Siemens Healthcare GmbH
- Inventors: Andreas Greiser; Rene Kartmann; Stephan Biber
- Web page: https://patentgrep.com/patent/US11304653B2

## CPC

- A61B 5/4547: {Evaluating teeth}
- A61B 5/055: involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
- G01R 33/34084: {implantable coils or coils being geometrically adaptable to the sample, e.g. flexible coils or coils comprising mutually movable parts}
- G01R 33/3802: {Manufacture or installation of magnet assemblies; Additional hardware for transportation or installation of the magnet assembly or for providing mechanical support to components of the magnet assembly}
- G01R 33/3858: {Manufacture and installation of gradient coils, means for providing mechanical support to parts of the gradient-coil assembly (manufacture of inductances or coils in general H01F41/00)}
- G01R 33/3808: {Magnet assemblies for single-sided MR wherein the magnet assembly is located on one side of a subject only; Magnet assemblies for inside-out MR, e.g. for MR in a borehole or in a blood vessel, or magnet assemblies for fringe-field MR}
- G01R 33/445: {MR involving a non-standard magnetic field B0, e.g. of low magnitude as in the earth's magnetic field or in nanoTesla spectroscopy, comprising a polarizing magnetic field for pre-polarisation, B0 with a temporal variation of its magnitude or direction such as field cycling of B0 or rotation of the direction of B0, or spatially inhomogeneous B0 like in fringe-field MR or in stray-field imaging}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

A magnetic resonance imaging system can include a magnetic field generator, an image acquisition region and a radiofrequency system including at least one radiofrequency antenna. The radiofrequency system can emit a radiofrequency excitation pulse into the image acquisition region and receive magnetic resonance signals from the image acquisition region. The magnetic field generator can include at least one magnet to generate a magnetic field in the image acquisition region, a magnet holder to carry the at least one magnet and a rotation system to position the magnet holder along a rotation trajectory.

## Claims

### Claim 1

A magnetic resonance imaging (MRI) system comprising:
an image acquisition region;
a radiofrequency system including at least one radiofrequency antenna, the radiofrequency system being configured to emit a radiofrequency excitation pulse into the image acquisition region and receive magnetic resonance signals from the image acquisition region; and
a magnetic field generator that includes:
at least one magnet configured to generate a magnetic field in the image acquisition region;
a magnet holder configured to carry the at least one magnet; and
a rotation system configured to position the magnet holder along a rotation trajectory.

### Claim 2 (depends on 1)

The MRI system according to claim 1, wherein the at least one magnet is configured to generate an inhomogeneous magnetic field in the image acquisition region, the inhomogeneous magnetic field including a magnetic field gradient along a radial direction of the rotation trajectory.

### Claim 3 (depends on 2)

The MRI system according to claim 2, further comprising a controller configured to perform a spatial encoding of magnetic resonance signals acquired from the image acquisition region based on the magnetic field gradient along the radial direction of the rotation trajectory.

### Claim 4 (depends on 1)

The MRI system according to claim 1, wherein the rotation system comprises a mechanical guiding rail configured to guide the magnet holder along the rotation trajectory around a rotation center.

### Claim 5 (depends on 1)

The MRI system according to claim 1, wherein the rotation trajectory comprises a rotation angle in the range of 120° to 270°.

### Claim 6 (depends on 1)

The MRI system according to claim 1, wherein the magnetic field generator comprises:
a first magnet of the at least one magnet configured to generate a first magnetic field inside the image acquisition region; and
a second magnet of the at least one magnet configured to generate a second magnetic field inside the image acquisition region.

### Claim 7 (depends on 6)

The MRI system according to claim 6, wherein the rotation system is configured to:
move the first magnet from a first end position on the rotation trajectory to a predefined position on the rotation trajectory; and
move the second magnet from the predefined position to a second end position on the rotation trajectory.

### Claim 8 (depends on 1)

The MRI system according to claim 1, wherein the magnetic field generator comprises a magnetic field gradient system including at least one gradient coil configured to provide a magnetic gradient field in the image acquisition region, the at least one gradient coil being carried by the magnet holder.

### Claim 9 (depends on 4)

The MRI system according to claim 4, wherein:
the magnetic field generator comprises a magnetic field gradient system including at least one gradient coil configured to provide a magnetic gradient field in the image acquisition region; and
the rotation system comprises a gradient coil holder configured to carry the at least one gradient coil, the mechanical guiding rail being configured to guide the gradient coil holder along the rotation trajectory.

### Claim 10 (depends on 8)

The MRI system according to claim 8, wherein the magnetic gradient field generated by the at least one magnet is oriented at an angle of at least 50° to the magnetic gradient field generated by the at least one gradient coil.

### Claim 11 (depends on 8)

The MRI system according to claim 8, further comprising a controller configured to perform spatial encoding of magnetic resonance signals acquired from the image acquisition region based on a change of the magnetic field induced by the positioning of the at least one magnet along the rotation trajectory and the magnetic gradient field of the at least one gradient coil.

### Claim 12 (depends on 1)

The MRI system according to claim 1, wherein:
a contour of the rotation trajectory corresponds to a contour of a body region of a patient; and
the rotation system is configured to position the magnet holder along the contour of the body region of the patient.

### Claim 13 (depends on 12)

The MRI system according to claim 12, wherein the contour of the rotation trajectory corresponds to a contour of a jaw region of the patient, the magnetic resonance imaging system being configured to acquire magnetic resonance signals of a tooth and/or a jaw of the patient.

### Claim 14 (depends on 12)

The MRI system according to claim 12, wherein the magnetic field generator comprises an adjustment mechanism configured to adjust a position, a shape, and/or an orientation of the rotation system to accommodate for a geometry of the body region of the patient.

### Claim 15 (depends on 12)

The MRI system according to claim 12, wherein the magnetic field generator further comprises a distance adapter configured to adjust a spacing between the magnet holder and a surface of the patient.

### Claim 16 (depends on 15)

The MRI system according to claim 15, wherein the distance adapter comprises a sensor configured to determine a distance value between the magnet holder and the surface of the patient, the distance adapter being configured to adjust a spacing between the magnet holder and the surface of the patient based on the distance value.

### Claim 17 (depends on 15)

The MRI system according to claim 15, wherein:
the radiofrequency system is configured to acquire magnetic resonance navigator data from the image acquisition region;
the MRI system further comprises a controller configured to determine a distance value between the magnet holder and the surface of the patient based on the magnetic resonance navigator data; and
the distance adapter is configured to adjust a spacing between the magnet holder and the surface of the patient based on the distance value.

### Claim 18 (depends on 6)

The MRI system according to claim 6, wherein:
the first magnet is configured to generate a pulsed first magnetic field and the second magnet is configured to generate a homogenous second magnetic field, and
the magnetic resonance imaging system further comprises a controller configured to:
control the first magnet to generate the pulsed first magnetic field to pre-polarize nuclear spins inside an imaging volume and switch off the first magnet when the second magnet is switched on; and
control the second magnet to generate the homogeneous second magnetic field inside the imaging volume during a radiofrequency excitation of the pre-polarized spins and during an acquisition of magnetic resonance signals from the imaging volume.