Magnetic resonance imaging method

Abstract

The invention relates to a method for imaging a part of a human or animal body by means of a magnetic resonance imaging device, the imaging method comprising the use of a belt which with one of its faces, referred to as the first face, surrounds a section of the trunk of the body, referred to as the contact section, the belt being electrically conductive and set at the same electrical potential as all of the electric and electronic elements constituting the magnetic resonance imaging device during acquisition of a magnetic resonance image of a part of the human body, such that a flow of electric charges is permitted.

Description

magnetic resonance imaging procedure FIELD OF THE INVENTION

[0001] The present invention relates to the field of magnetic resonance imaging. In particular, the present invention relates to a magnetic resonance imaging method. More particularly, the magnetic resonance imaging method according to the present invention implements means for limiting the effect of ambient noise and in particular the electronic noise captured by electronic control modules of said device for forming an MRI image of a body by means of an MRI device. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0002] Magnetic resonance imaging (MRI) is now widely used to non-invasively image the interior of bodies, particularly human bodies. In particular, magnetic resonance imaging can probe the hydrogen nuclei, and in particular their nuclear spin, of water molecules that form part of the body under examination.

[0003] In this regard, an MRI device is equipped with a magnet intended to impose a static magnetic field on the body (called the "main magnetic field"), under the effect of which, the nuclear spins associated with the hydrogen nuclei contained in the water molecules forming part of this body become polarized.

[0004] In particular, the magnetic moments associated with these spins preferentially align along an axis, called the z axis, determined by the orientation of the main magnetic field so as to create a magnetization of the body.

[0005] An MRI device also includes gradient coils configured to produce small-amplitude, spatially varying magnetic fields when a current is applied thereto. More specifically, the gradient coils are configured to produce a magnetic field component that is aligned parallel to the main magnetic field, and that varies linearly in magnitude with position along one of the x, y, or z axes (the x, y, and z axes being pairwise perpendicular).

[0006] Thus, the combined effects of the magnetic fields imposed by the gradient coils make it possible to spatially code each of the positions of the body to be probed.

[0007] An MRI device also comprises at least one radiofrequency (RF) coil intended to act as an RF transmitter / receiver. In particular, the at least one radiofrequency coil is configured to emit pulses of RF energy of a frequency equal to or close to the resonance frequency of the spins of the hydrogen nuclei and which is at least partly absorbed by these nuclei.

[0008] Once the RF emission is interrupted, the nuclear spins relax to return to their initial energy state and in turn emit an RF signal that can be collected by at least one RF coil. This RF signal is then processed using a computer and reconstruction algorithms to obtain an image of the body.

[0009] The main magnetic field, generally between 1.5 Tesla and 3 Tesla, makes it possible to achieve relatively reasonable signal-to-noise ratios and consequently to form images of the human body of sufficient quality over durations of the order of a minute or more.

[0010] However, there are circumstances in which it is not possible to implement a main magnetic field of such intensity. Portable MRI devices are one example. These typically include a permanent magnet or electromagnets of limited capacity, and cannot impose a main magnetic field of an intensity greater than 60 mT, or even greater than 200 mT, without penalizing the mass or size of the MRI device in question.

[0011] This limitation in terms of main magnetic field intensity directly affects the performance of the MRI device. In particular, the images obtained with such an MRI device are likely to have a quality significantly degraded by an unfavorable signal-to-noise ratio. This unfavorable signal-to-noise ratio is the consequence of the strong reduction in magnetization present in the tissues due to the consideration of a low amplitude main magnetic field.

[0012] An aim of the present invention is to propose a magnetic resonance imaging method making it possible to reduce noise when the main magnetic field is weak and in particular less than 100 mT.

[0013] Another aim of the present invention is to propose a magnetic resonance imaging method making it possible to reduce low-field noise and in accordance with electrical safety standards, in particular the IEC 60601-1 standards, provided that the main magnetic field is weak and in particular less than 100 mT. BRIEF DESCRIPTION OF THE INVENTION

[0014] In order to achieve this aim, the invention proposes a method for imaging a part of a human or animal body by means of a magnetic resonance imaging device, said imaging method comprising the implementation of a belt surrounding, by one of its faces called the first face, a section of the trunk of said body called the contact section, said belt being electrically conductive and placed at the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device during an acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges.

[0015] According to a particularly advantageous embodiment, it is possible to consider a belt connected to the earth potential. In other words, and according to this embodiment, it is a question of connecting to the earth potential all the electrical and electronic elements as well as the belt.

[0016] According to one implementation method, the electric potential is equal to the earth potential.

[0017] According to one embodiment, the belt comprises a matrix of electrically insulating material, advantageously a polyamide material.

[0018] According to one embodiment, the belt comprises, on its first face, metallic structures, all of the metallic structures being at the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges.

[0019] According to one embodiment, the metal structures comprise at least one of the elements chosen from: metal plates, for example plates, metal sheets, for example aluminum sheets, metal buttons.

[0020] According to one embodiment, the metal structures are electrically connected to each other, in particular by a bundle of electrically conductive connection wires, advantageously, the connection wires comprise at least one of the materials chosen from: silver, copper, tin.

[0021] Depending on the implementation method, the metal structures are clipped, glued, or sewn onto the matrix.

[0022] According to one method of implementation, the metal structures are rectangular or square in shape and are arranged in a checkerboard pattern, advantageously, all of the metal structures covering at least 85% of an area of ​​the first face intended to be in contact with the contact section.

[0023] According to one embodiment, the belt comprises a set of contact wires arranged in the matrix of contact wires being connected to the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges, advantageously, the contact wires comprise at least one of the materials chosen from: silver, copper, tin.

[0024] According to one embodiment, the imaging method uses an imaging device provided with a magnet defining a space inside which the part of the body is placed during the acquisition of the magnetic resonance image, the magnet imposing during said acquisition a magnetic field of less than 100 mT, even more advantageously of less than 50 mT.

[0025] According to one embodiment, the body part includes the head.

[0026] Depending on the method of implementation, the belt is between 18 cm and 30 cm wide.

[0027] According to one embodiment, the belt has a surface electrical resistance of less than 1 Ohm per square, advantageously less than 0.5 Ohm per square, even more advantageously less than 0.1 Ohm per square.

[0028] The invention also relates to a magnetic resonance imaging device provided with a belt intended to ensure electrical contact with a contact section of the trunk of a body, said belt, electrically conductive, being connected to the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges.

[0029] According to one embodiment, the belt comprises a matrix of electrically insulating material, advantageously a polyamide material.

[0030] According to one embodiment, the belt comprises, on its first face, metallic structures, all of the metallic structures being at the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges.

[0031] According to one embodiment, the metal structures comprise at least one of the elements chosen from: metal plates, for example plates, metal sheets, metal buttons.

[0032] According to one embodiment, the metal structures are electrically connected to each other, in particular by a bundle of electrically conductive connection wires, advantageously, the connection wires comprise at least one of the materials chosen from: silver, copper, tin.

[0033] According to one embodiment, the metal structures are clipped, glued, or sewn onto the matrix.

[0034] According to one embodiment, the metal structures are rectangular or square in shape and are arranged in a checkerboard pattern, advantageously, all of the metal structures covering at least 85% of an area of ​​the first face intended to be in contact with the contact section.

[0035] According to one embodiment, the belt comprises a set of contact wires arranged in the matrix of contact wires being connected to the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges, advantageously, the contact wires comprise at least one of the materials chosen from: silver, copper, tin.

[0036] According to one embodiment, the belt has a width of between 18 cm and 30 cm.

[0037] According to one embodiment, the belt has a surface electrical resistance of less than 1 Ohm per square, advantageously less than 0.5 Ohm per square, even more advantageously less than 0.1 Ohm per square.

[0038] The invention also relates to a belt intended to be used during the imaging of a part of a human body by means of a magnetic resonance imaging device, the belt comprising a face, called the first face, and intended to ensure electrical contact, by its first face, with a contact section of the trunk of a body, said belt being electrically conductive, and is configured to allow a flow of electrical charges when it is connected to the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device during an acquisition of a magnetic resonance image of a part of the human body.

[0039] According to one embodiment, the belt comprises a matrix of electrically insulating material, advantageously a polyamide material.

[0040] According to one embodiment, the belt comprises, on its first face, metallic structures, all of the metallic structures being at the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges.

[0041] According to one embodiment, the metal structures comprise at least one of the elements chosen from: metal plates, for example plates, metal sheets, metal buttons.

[0042] According to one embodiment, the metal structures are electrically connected to each other, in particular by a bundle of electrically conductive connection wires, advantageously, the connection wires comprise at least one of the materials chosen from: silver, copper, tin.

[0043] According to one embodiment, the metal structures are clipped, glued, or sewn onto the matrix.

[0044] According to one embodiment, the metal structures are rectangular or square in shape and are arranged in a checkerboard pattern, advantageously, all of the metal structures covering at least 85% of an area of ​​the first face intended to be in contact with the contact section.

[0045] According to one embodiment, the belt comprises a set of contact wires arranged in the matrix of contact wires being connected to the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges, advantageously, the contact wires comprise at least one of the materials chosen from: silver, copper, tin.

[0046] According to one embodiment, the belt has a width of between 18 cm and 30 cm.

[0047] According to one embodiment, the belt has a surface electrical resistance of less than 1 Ohm per square, advantageously less than 0.5 Ohm per square, even more advantageously less than 0.1 Ohm per square. BRIEF DESCRIPTION OF THE FIGURES

[0048] Other characteristics and advantages of the invention will emerge from the detailed description of the invention which follows with reference to the appended figures in which:

[0049] This is a schematic representation according to an exploded view of a magnetic resonance imaging device capable of being implemented within the framework of the present invention;

[0050] This is a photograph of a section of a human torso around which a belt is arranged in accordance with the principles set forth in the present invention;

[0051] This is a schematic representation of a belt capable of being implemented in the present invention according to a first embodiment;

[0052] This is a schematic representation of a belt capable of being implemented in the present invention according to a first variant of a second mode of implementation;

[0053] This is a schematic representation of a belt capable of being implemented in the present invention according to a second variant of a second mode of implementation;

[0054] This is a schematic representation of another example of a belt capable of being implemented in the present invention according to a second variant of a second embodiment;

[0055] This is a schematic representation of another example (third example) of a belt capable of being implemented in the present invention according to a second variant of a second mode of implementation;

[0056] This is a schematic representation of another example (fourth example) of a belt capable of being implemented in the present invention according to a second variant of a second mode of implementation;

[0057] This is a schematic representation of another example (last example) of a belt capable of being implemented in the present invention according to a second variant of a second mode of implementation. DETAILED DESCRIPTION OF THE INVENTION

[0058] The present invention relates to a method for imaging a part of a human or animal body. In particular, the imaging method uses a resonance imaging device, more particularly a so-called low-field resonance imaging device. By "low field" is meant a main magnetic field with an intensity of less than 200 mT, advantageously less than 100 mT, even more advantageously less than 50 mT.

[0059] Thus, this is a schematic representation of a magnetic resonance imaging device 1 capable of being implemented within the framework of the present invention.

[0060] The imaging device 1 comprises a magnet, and in particular a permanent magnet 2. The permanent magnet 2 can in particular extend along an elongation axis z.

[0061] More particularly, the permanent magnet 2 defines a housing 3 opening through a first opening 4 and a second opening 5 opposite one another along the elongation axis z.

[0062] In this regard, the permanent magnet 2 is arranged to allow the insertion of a body, and more particularly a human body, into the housing 3 through the first opening 4 along the elongation axis z.

[0063] The permanent magnet 2 is more particularly configured to impose a static magnetic field oriented along an axis perpendicular to the elongation axis z, in a zone, called the analysis zone, of the housing 3.

[0064] In this regard, the permanent magnet 2 may comprise an assembly of elementary magnets, and in particular arranged in series of Halbach rings. Document EP3368914B1 gives an example. However, the invention is not limited to the sole configuration described in this document.

[0065] For example, the permanent magnet 2 is configured to impose a static magnetic field with an amplitude of less than 100 mT, advantageously less than 65 mT, and even more advantageously less than or equal to 50 mT.

[0066] The imaging system 1 also includes a set of gradient coils 6. The gradient coils 6 are notably configured to produce small amplitude, spatially varying magnetic fields when a current is applied to them.

[0067] More particularly, the gradient coils 6 are designed to produce a magnetic field component that is aligned parallel to the static magnetic field, and that varies linearly in magnitude with position along one of the x, y, or z axes (the x, y, and z axes form an orthogonal coordinate system).

[0068] Thus, the combined effects of the magnetic fields imposed by the gradient coils 6 make it possible to spatially encode the signals originating from a body present in the housing 3 and intended to be probed. The spatial encoding is manifested in particular by a variation in the resonance energy of the nuclear spins of the hydrogen nuclei included in the body intended to be probed and present in the analysis zone. In other words, the nuclear spins of the hydrogen nuclei are subjected to a magnetic field which differs from one position to another.

[0069] The imaging system 1 further comprises a radiofrequency (RF) coil 7 intended to act as an RF transmitter / receiver. In particular, the at least one radiofrequency coil 7 is configured to emit RF energy pulses of a frequency equal to or close to the resonance frequency of the spins of the hydrogen nuclei and which is at least partly absorbed by these nuclei.

[0070] The radiofrequency coil 7 can be connected to pulse means 10 configured to impose the circulation of a current in said radiofrequency coil 7. More particularly, the pulse means 10 can be configured to allow the generation of current pulses in the radiofrequency coil 7. The pulse means are also advantageously implemented to power the gradient coils 6 in order to spatially code each of the positions of a body likely to be present in the housing 3.

[0071] The radiofrequency coil can also be connected to radiofrequency processing means 11 configured to process a radiofrequency signal capable of being received by the assembly formed by the radiofrequency coil 7.

[0072] The imaging system 1 may comprise a first interface 12 providing a link, on the one hand, between the pulse means 10 and the radiofrequency coil 7, and on the other hand, between the radiofrequency processing means 11 and the radiofrequency coil 7.

[0073] The imaging system 1 may, furthermore, comprise a second interface 13 providing a link between the pulse means 10 and the gradient coils 6.

[0074] The pulse means 10, the radiofrequency processing means 11, the first interface 12 and the second interface 13 can be controlled by a control unit 14, for example a computer 14.

[0075] Thus, in operation, the radiofrequency coil 7 is arranged in the housing 3, and the body intended to be imaged in the interior volume of said radiofrequency coil 7.

[0076] The present invention therefore comprises a method for imaging a part of a human or animal body by means of a magnetic resonance imaging device, and in particular the imaging device 1 as described previously.

[0077] The imaging method notably comprises the implementation of a belt 50 (illustrated in la and in la) surrounding a section of the trunk of said body 60 called contact section 51. In a particularly advantageous manner, the belt 50 surrounds the navel of the body 60. It is understood, without it being necessary to specify it, that the belt forms a loop around the trunk. Furthermore, the belt comprises two faces opposite each other called, respectively, first face 50a and second face 50b.

[0078] The belt 50 may comprise in particular a matrix of insulating material, and in particular a polyamide material.

[0079] According to a first advantageous embodiment, a set of electrically conductive wires, called contact wires, can be arranged (and / or embedded) in the matrix of insulating material. In particular, the contact wires are intended to ensure electrical contact with the contact section. The contact wires are connected to the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges.

[0080] As shown in the, the belt 50 also comprises an electrical connection means 52 intended to allow the connection of said belt 50 to the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device during an acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges.

[0081] The belt can be between 18 cm and 30 cm wide.

[0082] The matrix may comprise a polyamide material.

[0083] Advantageously, the contact wires may comprise at least one of the materials chosen from: silver, copper, nickel, tin.

[0084] The contact wires may be arranged within the matrix so that said belt has a surface electrical resistance of less than 1 Ohm per square, advantageously less than 0.5 Ohm per square, even more advantageously less than 0.3 Ohm per square, still more advantageously less than 0.1 Ohm per square.

[0085] Table 1 and Table 2 below give measurements of the noise level obtained for different configurations. In particular, this noise, given in microvolts, was measured during the implementation of an imaging method with a resonance imaging device having the following characteristics: The belt 50 is placed around the trunk of the body of an individual for imaging an arm of said individual (using a 27 cm scanner: see Table 1) or imaging the head of said individual (using the 32 cm scanner: see Table 2); The main magnetic field is less than 50 mT; Sequence used to measure the noise: measurement without radio-frequency emission with a reception bandwidth of 20 kHz (similar to the bandwidth used for a clinical sequence) Acquisition of a single dimension; Averaging of 4 acquisitions;

[0086] Measurement of the effective value in amplitude

[0087] In these tables, the "Phantom" line corresponds to the noise level obtained when measuring an image of a commercial phantom placed in the imaging device described above. This phantom has dielectric properties similar to human tissue. This measurement, used for reference purposes, does not implement the belt according to the terms of the present invention.

[0088] The lines "Volunteer 1" and "Volunteer 2" correspond to the noise level obtained during the measurement of a first individual ("First series") and a second individual ("Second series") placed in the imaging device described above. The measurements implement a belt 50 surrounding the trunk of the first and second individuals. The measurements implement a belt 22 cm wide. In both cases, the belt has a surface electrical resistance of less than 0.5 Ohm per square and is connected to the earth's electrical potential during the measurement. The second column of tables "Table 1" and "Table 2" presents the noise measured without a belt. The third column of tables "Table 1" and "Table 2" presents the noise measured with a belt. Finally, the fourth and last column of tables "Table 1" and "Table 2" presents the percentage reduction between the noise measured with and without a belt.The measurements are carried out according to the procedure described above.

[0089] Table 1: Use on 27 cm scanner, arm imagingCaseNoise measured without belt (micro-volt)Noise measured with belt (micro-volt)Percentage reductionPhantom0.06N.ANAVoluntary 12.050.0597.5%Voluntary 21.910.0696.8%

[0090] Table 2: Use on 32 cm scanner, head imagingCaseNoise measured without belt (micro-volt)Noise measured with belt (micro-volt)Percentage reductionPhantom0.27N.ANAVoluntary 115.640.2998.1%Voluntary 213.540.2298.4%

[0091] The “Voluntary 1” and “Voluntary 2” measurements, without a belt, have a noise level between 13 microvolts and 16 microvolts for use on a 32 cm scanner for head imaging, well above the reference measurements.

[0092] The implementation of the belt allows to substantially attenuate electronic noise and produce good quality images.

[0093] The inventors were thus able to establish that the positioning of the belt 50 around the trunk of the body allows a relatively efficient flow of electrical charges regardless of the part of the body to be imaged. The resulting reduction in electronic noise allows for better resolution of the images obtained and thus the consideration of weaker magnetic fields, for example less than 100 mT, or even less than 50 mT.

[0094] The inventors were also able to observe that the positioning, for example of a bracelet made of the same material as the belt and positioned on the ankle or wrist, did not make it possible to obtain a reduction of electronic noise as effective and universal as the belt as implemented within the framework of the present invention.

[0095] Illustrates a second embodiment of the belt 50 capable of being implemented within the framework of the present invention.

[0096] In particular, the belt according to this second embodiment can have all of the characteristics of the belt implemented in the context of the first embodiment.

[0097] According to this second embodiment, the belt 50 comprises, on its first face 50a, metal structures 53. In particular, these metal structures are configured to be at the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges.

[0098] The metal structures 53 may comprise at least one of the elements chosen from: metal plates, for example plates, metal sheets, for example aluminum sheets, metal buttons.

[0099] In the example shown in, the metal structures comprise rectangular plates.

[0100] Generally, metal structures can be clipped, glued, or sewn onto the matrix.

[0101] However, this latter aspect is not such as to limit the invention, so that the person skilled in the art, on the basis of his general knowledge, will be able to imagine other means of fixing for attaching the metal structures to the first face.

[0102] According to the variant, called the first variant, illustrated in the, the metal structures 53 are electrically connected to each other, in particular by a bundle of wires, called connection wires 54, electrically conductive, advantageously, the connection wires comprise at least one of the materials chosen from: silver, copper, tin.

[0103] Table 3 below gives measurements of the noise level obtained for different configurations. In particular, this noise, given in microvolts, was measured during the implementation of an imaging method with a resonance imaging device having the following characteristics: The belt 50 is placed around the trunk of the body of an individual for imaging the head of said individual (using a 32 cm scanner); The main magnetic field is less than 50 mT; Sequence used to measure the noise: measurement without radio-frequency emission with a reception bandwidth of 20 kHz (similar to the bandwidth used for a clinical sequence) Acquisition of a single dimension; Averaging of 4 acquisitions;

[0104] Measurement of the effective value in amplitude

[0105] In Table 3, the "Phantom" line corresponds to the noise level obtained when measuring an image of a commercial phantom placed in the imaging device described above. This phantom has dielectric properties similar to human tissue. This measurement, used for reference purposes, does not implement the belt according to the terms of the present invention.

[0106] The lines "Volunteer 1" and "Volunteer 2" correspond to the noise level obtained during the measurement of a first individual and a second individual placed in the imaging device described above. The measurements implement a belt 50 surrounding the trunk of the first and second individuals. The measurements implement a belt 22 cm wide. In either case, the belt has a surface electrical resistance of less than 0.5 Ohm per square and is connected to the earth's electrical potential during the measurement. The second column presents the noise measured without the belt. The third column of Table 3 presents the noise measured with the belt of the first embodiment. The fourth column of Table 3 presents the noise measured with the belt according to the first variant of the first embodiment.

[0107] Table 3: Use on 32 cm scanner, head imagingCaseNoise measured without belt (micro-volt)Noise measured with belt (micro-volt) of the first embodimentNoise measured with belt of the first variant of the second embodiment (micro-volt)Phantom0.06N.ANAVoluntary 14.740.150.13Voluntary 25.790.220.21

[0108] Laet illustrate, respectively, a first example and a second example of belt 50 according to a second variant of the second embodiment.

[0109] In particular, the belt according to this second variant, and for all the examples to follow, essentially takes up the characteristics of the first variant, but is devoid of the connecting wires. In particular, the metal structures of the first example comprise square plates held by screws on the matrix, while the metal structures of the second example comprise rectangular copper plates glued to the matrix.

[0110] According to the present invention, and in particular in relation to the second example, the metal structures are rectangular or square in shape and are arranged in a checkerboard pattern, advantageously, all of the metal structures 53 covering at least 85% of an area of ​​the first face intended to be in contact with the contact section. Furthermore, the matrix relating to this second example is devoid of contact wire.

[0111] Table 4 below gives measurements of the noise level obtained for different configurations. In particular, this noise, given in microvolts, was measured during the implementation of an imaging method with a resonance imaging device having the following characteristics: The belt 50 is placed around the trunk of the body of an individual for imaging the head of said individual (using a 32 cm scanner); The main magnetic field is less than 50 mT; Sequence used to measure the noise: measurement without radio-frequency emission with a reception bandwidth of 20 kHz (similar to the bandwidth used for a clinical sequence) Acquisition of a single dimension; Averaging of 4 acquisitions;

[0112] Measurement of the effective value in amplitude

[0113] In Table 4, the "Phantom" line corresponds to the noise level obtained when measuring an image of a commercial phantom placed in the imaging device described above. This phantom has dielectric properties similar to human tissue. This measurement, used for reference purposes, does not implement the belt according to the terms of the present invention.

[0114] The lines “Volunteer 1” and “Volunteer 2” correspond to the noise level obtained during the measurement of a first individual and a second individual placed in the imaging device described above. The measurements implement a belt 50 surrounding the trunk of the first and second individuals. The measurements implement a belt 22 cm wide according to the first and second examples of the second variant. In either case, the belt has a surface electrical resistance of less than 0.5 Ohm per square and is connected to the earth's electrical potential during the measurement. The second column presents the noise measured without the belt. The third column presents the noise measured with the belt of the first embodiment.The fourth column of Table 4 presents the noise measured with the first belt example of the second variant, while the fifth column of Table 4 presents the noise measured with the second belt example of the second variant.

[0115] Table 4: Use on 32 cm scanner, head imagingCaseNoise measured without belt (micro-volt)Noise measured with belt (micro-volt) of the first embodimentNoise measured with the first example of belt of the second variant of the second embodiment (micro-volt)Noise measured with the second example of belt of the second variant of the second embodiment (micro-volt)Phantom0.06N.ANANAVoluntary 14.740.150.170.43Voluntary 25.790.150.170.46

[0116] The second belt example (fourth column of table 4), without contact wires, seems to see its performance degraded compared to the other belts.

[0117] Laet illustrate, respectively, a third example and a fourth example of belt 50 according to a second variant of the second embodiment.

[0118] The metal structures of the third example include metal buttons held by screws on the matrix, while the metal structures of the second example include metal sheets, particularly aluminum, glued to the matrix.

[0119] According to the present invention, and in particular in relation to the fourth example, the matrix is ​​devoid of contact wire.

[0120] Table 5 below gives measurements of the noise level obtained for different configurations. In particular, this noise, given in microvolts, was measured during the implementation of an imaging method with a resonance imaging device having the following characteristics: The belt 50 is placed around the trunk of the body of an individual for imaging the head of said individual (using a 32 cm scanner); The main magnetic field is less than 50 mT; Sequence used to measure the noise: measurement without radio-frequency emission with a reception bandwidth of 20 kHz (similar to the bandwidth used for a clinical sequence) Acquisition of a single dimension; Averaging of 4 acquisitions;

[0121] Measurement of the effective value in amplitude

[0122] In Table 5, the “Phantom” line corresponds to the noise level obtained when measuring an image of a commercial phantom placed in the imaging device described above. This phantom has dielectric properties similar to human tissue. This measurement, used for reference purposes, does not implement the belt according to the terms of the present invention.

[0123] The lines “Volunteer 1”, “Volunteer 2”, and “Volunteer 3” correspond to the noise level obtained during the measurement of a first individual, a second individual, and a third individual placed in the imaging device described above. The measurements use a belt 50 surrounding the trunk of the first, second, and third individuals. The measurements use a 22 cm wide belt according to the third and fourth examples of the second variant. In either case, the belt has a surface electrical resistance of less than 0.5 Ohm per square and is connected to the earth's electrical potential during the measurement. The second column shows the noise measured without the belt. The third column shows the noise measured with the belt of the first embodiment.The fourth column of Table 4 presents the noise measured with the third belt example of the second variant, while the fifth column of Table 4 presents the noise measured with the fourth belt example of the second variant.

[0124] Table 4: Use on 32 cm scanner, head imagingCaseNoise measured without belt (micro-volt)Noise measured with belt (micro-volt) of the first embodimentNoise measured with the third example of belt of the second variant of the second embodiment (micro-volt)Noise measured with the fourth example of belt of the second variant of the second embodiment (micro-volt)Phantom0.07N.ANANAVoluntary 15.490.140.170.20Voluntary 23.090.100.150.09Voluntary 33.940.090.120.15

[0125] Both the third and fourth examples give acceptable performance.

[0126] Illustrates a final example according to the second variant which essentially takes up the characteristics of the fourth example. However, in this example, the metal sheets are replaced by metal plates with screws.

[0127] The noise measured on an individual under conditions equivalent to those listed in relation to the first, second, third and fourth examples is 0.20 microvolts.

[0128] Generally speaking, the implementation of the belt allows for a significant reduction of noise during head imaging. In particular, positioning the belt around the abdomen (or even the waist) remains the most effective configuration for noise reduction.

[0129] Surprisingly, positioning the belt (e.g. around the patient's neck if the head is to be imaged) as close as possible to the magnet is not necessarily the solution to effectively reduce noise.

[0130] Thus, the invention also relates to a magnetic resonance imaging device as described in connection with the invention which comprises a belt 50 according to the present invention.

[0131] The invention also relates to a belt which can have all of the characteristics described above.

Claims

Method for imaging a part of a human or animal body by means of a magnetic resonance imaging device (1), said imaging method comprising the implementation of a belt (50) surrounding, by one of its faces called the first face (50a), a section of the trunk of said body called the contact section (51), said belt (50) being electrically conductive and placed at the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device (1) during an acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges. Imaging method according to claim 1, wherein the belt (50) comprises a matrix of electrically insulating material, advantageously a polyamide material. Imaging method according to claim 2, in which the belt (50) comprises, on its first face (50a), metallic structures (53), all of the metallic structures (53) being at the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device (1) during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges. Imaging method according to claim 3, wherein the metal structures (53) comprise at least one of the elements chosen from: metal plates, for example plates, metal sheets, for example aluminum sheets, metal buttons. Imaging method according to claim 3 or 4, in which the metal structures (53) are electrically connected to each other, in particular by a bundle of electrically conductive connection wires (54), advantageously, the connection wires (54) comprise at least one of the materials chosen from: silver, copper, tin. Imaging method according to one of claims 3 to 5, in which the metal structures (53) are clipped, glued, or sewn onto the matrix. Imaging method according to one of claims 3 to 6, in which the metal structures (53) are rectangular or square in shape and are arranged in a checkerboard pattern, advantageously, all of the metal structures (53) covering at least 85% of an area of ​​the first face (50a) intended to be in contact with the contact section (51). Imaging method according to one of claims 3 to 6, in which the belt (50) comprises a set of contact wires arranged in the matrix of contact wires being connected to the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device (1) during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges, advantageously, the contact wires comprise at least one of the materials chosen from: silver, copper, tin. Imaging method according to one of claims 1 to 8, in which the imaging method implements the imaging device (1) provided with a magnet (2) defining a space inside which the part of the body is arranged during the acquisition of the magnetic resonance image, the magnet (2) imposing during said acquisition a magnetic field of less than 100 mT, even more advantageously of less than 50 mT. An imaging method according to one of claims 1 to 9, wherein the body part comprises the head. Imaging method according to one of claims 1 to 10, wherein the belt (50) has a width of between 18 cm and 30 cm. Imaging method according to one of claims 1 to 11, in which the belt (50) has a surface electrical resistance of less than 1 Ohm per square / m -2 , advantageously less than 0.5 Ohm per square / m -2, even more advantageously less than 0.1 Ohm per square / m -2 . Magnetic resonance imaging device (1) provided with a belt (50) intended to ensure electrical contact with a contact section (51) of the trunk of a body, said electrically conductive belt (50) being connected to the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device (1) during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges. Imaging device (1) according to claim 13, wherein the belt (50) comprises a matrix of electrically insulating material, advantageously a polyamide material. Imaging device (1) according to claim 13 or 14, in which the belt (50) comprises, on its first face (50a), metal structures (53), all of the metal structures (53) being at the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device (1) during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges. Imaging device (1) according to claim 15, wherein the metal structures (53) comprise at least one of the elements chosen from: metal plates, for example plates, metal sheets, metal buttons. Imaging device (1) according to claim 15 or 16, wherein the metal structures (53) are electrically connected to each other, in particular by a bundle of electrically conductive connection wires (54), advantageously, the connection wires (54) comprise at least one of the materials chosen from: silver, copper, tin. Imaging device (1) according to one of claims 14 to 17, in which the metal structures (53) are clipped, glued, or sewn onto the matrix. Imaging device (1) according to one of claims 14 to 18, in which the metal structures (53) are rectangular or square in shape and are arranged in a checkerboard pattern, advantageously, all of the metal structures (53) covering at least 85% of an area of ​​the first face (50a) intended to be in contact with the contact section (51). Imaging device (1) according to one of claims 14 to 19, in which the belt (50) comprises a set of contact wires arranged in the matrix of contact wires being connected to the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device (1) during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges, advantageously, the contact wires comprise at least one of the materials chosen from: silver, copper, tin. Imaging device (1) according to one of claims 13 to 20, wherein the belt (50) has a width of between 18 cm and 30 cm. Imaging device (1) according to one of claims 13 to 21, in which the belt (50) has a surface electrical resistance of less than 1 Ohm per square, advantageously less than 0.5 Ohm per square, even more advantageously less than 0.1 Ohm per square. Belt (50) intended to be used during the imaging of a part of a human body by means of a magnetic resonance imaging device (1), the belt (50) comprising a face, called the first face (50a), and intended to ensure electrical contact, by its first face (50a), with a contact section (51) of the trunk of a body, said belt (50) being electrically conductive, and is configured to allow a flow of electrical charges when it is connected to the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device (1) during an acquisition of a magnetic resonance image of a part of the human body. Belt (50) according to claim 23, wherein the belt (50) comprises a matrix of electrically insulating material, advantageously a polyamide material. Belt (50) according to claim 24, in which the belt (50) comprises, on its first face (50a), metallic structures (53), all of the metallic structures (53) being at the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device (1) during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges. Belt (50) according to claim 25, wherein the metal structures (53) comprise at least one of the elements chosen from: metal plates, for example plates, metal sheets, metal buttons. Belt (50) according to claim 25 or 26, in which the metal structures (53) are electrically connected to each other, in particular by a bundle of electrically conductive connection wires (54), advantageously, the connection wires (54) comprise at least one of the materials chosen from: silver, copper, tin. Belt (50) according to one of claims 25 to 27, in which the metal structures (53) are clipped, glued, or sewn onto the matrix. Belt (50) according to one of claims 25 to 28, in which the metal structures (53) are rectangular or square in shape and are arranged in a checkerboard pattern, advantageously, all of the metal structures (53) covering at least 85% of an area of ​​the first face (50a) intended to be in contact with the contact section (51). Belt (50) according to one of claims 25 to 29, in which the belt (50) comprises a set of contact wires arranged in the matrix of contact wires being connected to the same electrical potential as all of the electrical and electronic elements constituting the magnetic resonance imaging device (1) during acquisition of a magnetic resonance image of a part of the human body so as to allow a flow of electrical charges, advantageously, the contact wires comprise at least one of the materials chosen from: silver, copper, tin. Belt (50) according to one of claims 24 to 39, wherein the belt (50) has a width of between 18 cm and 30 cm. Belt (50) according to one of claims 24 to 31, in which the belt (50) has a surface electrical resistance of less than 1 Ohm per square, advantageously less than 0.5 Ohm per square, even more advantageously less than 0.1 Ohm per square.

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