Electromagnetic shielding for magnetic resonance imaging methods and apparatus
According to some aspects, a portable magnetic resonance imaging system is provided, comprising a B 0 magnet configured to produce a B 0 magnetic field for an imaging region of the magnetic resonance imaging system, a noise reduction system configured to detect and suppress at least some electromagnetic noise in an operating environment of the portable magnetic resonance imaging system, and electromagnetic shielding provided to attenuate at least some of the electromagnetic noise in the operating environment of the portable magnetic resonance imaging system, the electromagnetic shielding arranged to shield a fraction of the imaging region of the portable magnetic resonance imaging system. According to some aspects, the electromagnetic shield comprises at least one electromagnetic shield structure adjustably coupled to the housing to provide electromagnetic shielding for the imaging region in an amount that can be varied. According to some aspects, substantially no shielding of the imaging region is provided.
1 . A portable magnetic resonance imaging system, comprising:
at least one magnet configured to produce a magnetic field for an imaging region of the magnetic resonance imaging system, the magnet contained within a housing;
electromagnetic shielding for the imaging region of the magnetic resonance imaging system, the electromagnetic shielding comprising a frame fixedly attached to the housing, and a first shield member slidably coupled to the frame to allow the first shield member to be opened and closed to provide an amount of shielding of the imaging region of the magnetic resonance imaging system that is variable between at least a first amount of shielding and a second amount of shielding of the imaging region; and
an antenna capacitively coupled to a power line of the magnetic resonance imaging system, and configured to use measurements obtained by the antenna to suppress noise in an RF signal received by an RF coil of the magnetic resonance imaging system;
wherein the at least one magnet comprises a first permanent magnet and a second permanent magnet disposed opposite the first permanent magnet, with the imaging region between the first permanent magnet and the second permanent magnet.
2 . The magnetic resonance imaging system of claim 1 , wherein the magnetic resonance imaging system is a transportable magnetic resonance imaging system.
3 . The magnetic resonance imaging system of claim 1 , wherein the first shield member is slidable with respect to the frame between at least:
a first position, in which the first shield member provides the first amount of shielding; and
a second position, in which the first shield member provides the second amount of shielding.
4 . The magnetic resonance imaging system of claim 1 , further comprising a plurality of magnetics components including:
the at least one magnet;
a plurality of gradient coils; and
at least one radio frequency coil configured to provide radio frequency signals to the imaging region.
5 . The magnetic resonance imaging system of claim 1 , wherein the at least one magnet comprises at least one B 0 magnet configured to produce a B 0 field at a strength of less than or equal to approximately 0.1 T and greater than or equal to approximately 50 mT.
6 . The magnetic resonance imaging system of claim 1 , wherein the first shield member is configured to:
provide a first opening to accommodate at least a first portion of a patient in the first opening by the first shield member being opened and closed; and
close around the first portion of the patient to confine the first opening to a size of the first portion of the patient.
7 . The magnetic resonance imaging system of claim 1 , wherein:
the frame comprises a first track, and
the first shield member is slidably coupled to the first track to allow the first shield member to be opened and closed by sliding the first shield member along the first track.
8 . The magnetic resonance imaging system of claim 1 , wherein:
the first shield member is configured to provide a first opening on a first side of the imaging region; and
the electromagnetic shielding further comprises a second shield member slidably coupled to the frame to provide a second opening on a second side of the imaging region different from the first side and to vary a size of the second opening to accommodate at least a second portion of a patient in the second opening by the second shield member being opened and closed.
9 . The magnetic resonance imaging system of claim 1 , further comprising a noise reduction system including at least one radio frequency coil positioned outside of the imaging region, wherein the noise reduction system is configured to detect and suppress at least some electromagnetic noise in an operating environment of the portable magnetic resonance imaging system.
10 . The magnetic resonance imaging system of claim 1 , further comprising one or more electrical gaskets arranged to provide shielding along a periphery of the first shield member.
11 . The magnetic resonance imaging system of claim 1 , configured to detect and suppress noise in an RF signal obtained by an RF receive coil by generating RF signals that destructively interfere with environmental noise.
12 . The magnetic resonance imaging system of claim 1 , further comprising a noise suppression component adapted to suppress noise in a first signal detected by an RF coil based at least in part on a second signal detected by a sensor using a noise compensation transform.
13 . A portable magnetic resonance imaging system, comprising:
at least one permanent B 0 magnet comprising a plurality of concentric permanent magnet rings, the at least one permanent B 0 magnet configured to produce a B 0 field for an imaging region of the portable magnetic resonance imaging system;
electromagnetic shielding for the imaging region of the portable magnetic resonance imaging system, the electromagnetic shielding comprising a first shield member configured to provide a variable amount of shielding of the imaging region of the portable magnetic resonance imaging system; and
an antenna capacitively coupled to a power line of the magnetic resonance imaging system, and configured to use measurements obtained by the antenna to suppress noise in an RF signal received by an RF coil of the magnetic resonance imaging system;
wherein the at least one permanent B 0 magnet comprises a first permanent B 0 magnet and a second permanent B 0 magnet disposed opposite the first B 0 permanent magnet, with the imaging region between the first permanent B 0 magnet and the second permanent B 0 magnet.
14 . The portable magnetic resonance imaging system of claim 13 , wherein the electromagnetic shielding comprises a frame, and wherein the first shield member is slidably coupled to the frame to allow the first shield member to be opened and closed to provide the variable amount of shielding of the imaging region.
15 . The portable magnetic resonance imaging system of claim 13 , further comprising a first track, wherein:
the first shield member is slidably coupled to the first track to allow the first shield member to be opened and closed by sliding the first shield member along the first track.
16 . The portable magnetic resonance imaging system of claim 13 , wherein:
the first shield member is configured to provide a first opening on a first side of the imaging region; and
the electromagnetic shielding further comprises a second shield member configured to provide a second opening on a second side of the imaging region different from the first side and to vary a size of the second opening to accommodate at least a second portion of a patient in the second opening by the second shield member being opened and closed.
17 . The portable magnetic resonance imaging system of claim 13 , wherein the first shield member is configured to:
provide a first opening to accommodate at least a first portion of a patient in the first opening by the first shield member being opened and closed; and
close around the first portion of the patient to confine the first opening to a size of the first portion of the patient.
18 . The portable magnetic resonance imaging system of claim 13 , wherein the at least one permanent B 0 magnet is contained within a housing, wherein the electromagnetic shielding comprises a frame fixedly attached to the housing, and wherein the first shield member is slidably coupled to the frame.
19 . A portable low-field magnetic resonance imaging system, comprising:
at least one magnet configured to produce a magnetic field, at a strength of less than 0.2 T and greater than 50 mT, for an imaging region of the low-field magnetic resonance imaging system;
electromagnetic shielding for the imaging region of the portable low-field magnetic resonance imaging system, the electromagnetic shielding comprising a slidable first shield member configured to allow the first shield member to be opened and closed to provide an amount of shielding of the imaging region of the portable low-field magnetic resonance imaging system that is variable between at least a first amount of shielding and a second amount of shielding of the imaging region; and
an antenna capacitively coupled to a power line of the magnetic resonance imaging system, and configured to use measurements obtained by the antenna to suppress noise in an RF signal received by an RF coil of the magnetic resonance imaging system;
wherein the at least one magnet comprises a first permanent magnet and a second permanent magnet disposed opposite the first permanent magnet, with the imaging region between the first permanent magnet and the second permanent magnet.
20 . The portable low-field magnetic resonance imaging system of claim 19 , wherein the first shield member is configured to:
provide a first opening to accommodate at least a first portion of a patient in the first opening by the first shield member being opened and closed; and
close around the first portion of the patient to confine the first opening to a size of the first portion of the patient.
21 . The portable low-field magnetic resonance imaging system of claim 20 , wherein:
the first shield member is configured to provide the first opening on a first side of the imaging region; and
the electromagnetic shielding further comprises a second shield member configured to provide a second opening on a second side of the imaging region different from the first side and to vary a size of the second opening to accommodate at least a second portion of the patient in the second opening by the second shield member being opened and closed.
22 . The portable low-field magnetic resonance imaging system of claim 19 , wherein the first shield member is slidable between at least:
a first position, in which the first shield member provides the first amount of shielding; and
a second position, in which the first shield member provides the second amount of shielding.
23 . The portable low-field magnetic resonance imaging system of claim 19 , wherein the at least one magnet is contained within a housing, wherein the electromagnetic shielding comprises a frame fixedly attached to the housing, and wherein the slidable first shield member is coupled to the frame.