Method and apparatus for interference suppression of a whole-body antenna of a magnetic resonance device

Abstract

The invention relates to a magnetic resonance tomography apparatus having a transmitter for generating an excitation signal and a body coil for emitting the excitation signal, and also to a method. The magnetic resonance tomography apparatus has a patient tunnel with the body coil. The magnetic resonance tomography apparatus has a first interference-suppressed transmit antenna which is arranged between the body coil and an opening of the patient tunnel. The first interference-suppressed transmit antenna is designed to provide a similar spatial transmit characteristic as the body coil.

Description

Technical Field

[0001] The present invention relates to a magnetic resonance imaging (MRI) device having a transmitter for generating an excitation signal and a body coil for transmitting the excitation signal in a patient channel having a body coil. Background Technology

[0002] Magnetic resonance imaging (MRI) is a device used for imaging. To image an object being examined, it uses a strong external magnetic field to orient the spins of the atomic nuclei within the object, and then uses an alternating magnetic field to excite the spins to move around this oriented state. When the spins enter or return to a lower energy state, they generate an alternating magnetic field in response, which is received by an antenna.

[0003] By using a gradient magnetic field to position-encode the signal, the received signal can then be assigned to corresponding volume elements. The received signal is then analyzed to provide a three-dimensional imaging view of the object being examined. For signal reception, a local receiving antenna, also known as a local coil, is preferably used. The local coil is positioned directly on the object being examined to achieve a better signal-to-noise ratio. The receiving antenna can also be mounted in the patient platform.

[0004] Magnetic resonance imaging (MRI) equipment requires high-frequency shielding in two aspects. Firstly, it generates high-frequency pulses in the kilowatt range to excite atomic nuclei spin; these pulses are only partially absorbed by the patient. Secondly, radio waves leaving the patient's passage are emitted into the room and therefore must be shielded to maintain radiation limits.

[0005] Conversely, the magnetic resonance signal to be received for imaging is extremely weak. To achieve a sufficient signal-to-noise ratio (SNR), external interference signals need to be shielded.

[0006] Therefore, in existing technologies, complex shielding chambers are installed around magnetic resonance tomography scanners to reduce radiation emissions and radiation contamination.

[0007] The magnetic resonance imaging equipment and operating method with active interference suppression emission device are known from document WO 2019 / 06867 A2.

[0008] The challenge in this type of equipment is achieving stable interference suppression under different interference conditions. Summary of the Invention

[0009] Therefore, the technical problem to be solved by the present invention is to improve interference suppression.

[0010] The technical problem described herein is solved by a magnetic resonance imaging (MRI) device having a transmitter for generating an excitation signal and a body coil for emitting the excitation signal, wherein the MRI device has a patient channel with the body coil, and wherein the MRI device has a first interference suppression transmitting antenna disposed between the body coil and an opening in the patient channel, wherein the first interference suppression transmitting antenna is designed to provide spatial transmission characteristics similar to those of the body coil.

[0011] The technical problem described above is also solved according to the present invention by a method for operating a magnetic resonance imaging (MRI) device, wherein the MRI device has a body coil in a patient channel and a first interference suppression transmitting antenna, wherein the first interference suppression transmitting antenna is arranged between the body coil and an opening in the patient channel, wherein the first interference suppression transmitting antenna is designed to provide transmission characteristics similar to those of the body coil, and wherein the method comprises the following steps: transmitting an excitation signal through the MRI device via the body coil; and simultaneously transmitting a first interference suppression signal via the first interference suppression transmitting antenna. Furthermore, the MRI device also includes an interference sensor, and the method further comprises the following steps: detecting an interference signal through the interference sensor; determining a modified first interference suppression signal generated by the MRI device based on the measured interference signal, wherein the modified interference suppression signal is designed to reduce the energy of the interference signal; and repeating the transmission excitation signal and the transmission interference suppression signal in the previous step with the modified first interference suppression signal.

[0012] The magnetic resonance imaging (MRI) apparatus according to the invention has a transmitter for generating an excitation signal and a body coil for transmitting the excitation signal. The MRI apparatus has a patient channel in which the body coil is arranged. Here, the conductive boundary surrounding the patient is considered the patient channel, which surrounds the patient during examination along at least two different spatial directions and also inhibits or restricts the transmission of excitation signals along these directions. The patient channel is typically a cylinder or prism extending horizontally along the Bz or B0 field direction of the field magnet of the MRI apparatus. However, it is also conceivable that the patient channel has openings on its sides for treatment, for example, in cases of radiotherapy, biopsy, etc. Vertical orientation of the field magnet is also conceivable, allowing access to the patient from one or more directions in the horizontal plane, and, for example, the poles of the field magnet at least partially form a patient tunnel as an upper and lower boundary.

[0013] An antenna that at least partially surrounds the body or a body part and is designed to excite atomic nuclei spin within the body or body part by means of an excitation signal is called a body coil. In many magnetic resonance imaging (MRI) devices, the patient channel is designed as a cylinder or prism located within a cavity of a superconducting magnet, for example, a so-called "birdcage" antenna with the body coil located within the cylinder or prism. Depending on the magnetic field strength and the resulting Larmor frequency and corresponding wavelength, other body coils may also be provided, for example, as a matrix of individual magnetic or electric antennas. The outer contour of the body coil is typically adapted to the contour of the patient channel, thereby providing the patient with as much free width as possible within the body coil.

[0014] Furthermore, the magnetic resonance imaging (MRI) device has a first interference-suppressing transmitting antenna. This antenna is considered here as an interference-suppressing transmitting antenna capable of emitting an interference-suppressing signal, thereby transmitting a high-frequency signal generated by the excitation signal and the interference-suppressing signal from the opening of the patient tunnel. This high-frequency signal has lower energy and field strength than when there is no interference-suppressing signal. This reduction is achieved through destructive interference between the two signals. The first interference-suppressing transmitting antenna is positioned between the body coil and the opening of the patient tunnel. The first interference-suppressing transmitting antenna is designed to provide spatial transmission characteristics similar to those of the body coil. Spatial transmission characteristics here refer to the spatial distribution of the electromagnetic field emitted by the antenna. Characteristics of spatial transmission characteristics can be, for example, symmetry, such as mirror symmetry about a plane, axis, or point, or rotational symmetry about an axis or point. A birdcage antenna, for example, has an axis of symmetry at the center of the cylinder formed by the birdcage antenna and is rotationally symmetric about this axis. A birdcage antenna with eight conductor rods is, for example, rotationally symmetric about a rotation of n*360 / 8 degrees, where n is a natural number. Spatial transmission characteristics may also include the polarization of the emitted electromagnetic field.

[0015] An interference-suppressing transmitting antenna with spatial transmission characteristics similar to a body coil can advantageously generate a field distribution through an interference-suppressing signal derived from an excitation signal. This field distribution eliminates the excitation signal to the greatest extent through destructive interference in a wide space in front of the opening, because the field radiated by the interference-suppressing transmitting antenna propagates into the surrounding space with substantially the same symmetry and reduced intensity.

[0016] In one feasible embodiment of the magnetic resonance imaging (MRI) apparatus according to the invention, the MRI apparatus has an additional second interference-suppressing transmitting antenna. Particularly when the patient channel has a second opening and the first and second interference-suppressing transmitting antennas are arranged symmetrically with respect to the body coil and the opening, the second interference-suppressing transmitting antenna preferably has spatial transmission characteristics similar to the first interference-suppressing transmitting antenna. The body coil is here arranged along the longitudinal axis of the patient channel between the first and second interference-suppressing transmitting antennas.

[0017] The second interference suppression transmitting antenna can advantageously reduce radiation emitted from the two openings in the patient passage.

[0018] In one feasible embodiment of the magnetic resonance imaging apparatus according to the invention, the first interference-suppressing transmitting antenna and the body coil are of the same type. This can be understood as the two antennas having similar geometries or symmetries and / or radiators based on the same operating principle. Both the body coil and the first interference-suppressing transmitting antenna can be, for example, birdcage antennas. Preferably, the interference-suppressing transmitting antenna and the body coil have the same number of radiator elements or rods. This also applies accordingly to body coils or interference-suppressing transmitting antennas with other construction methods.

[0019] By using the same type of interference suppression transmitting antenna, a similar distribution of the radiated field is ensured in a simple way.

[0020] In one feasible embodiment of the magnetic resonance imaging apparatus according to the invention, the first interference-suppressing transmitting antenna and the body coil have a common electrical conductor. In other words, the interference-suppressing transmitting antenna and the body coil are directly connected via one or more electrical conductors. The electrical conductor may also be a passive element, such as a capacitor and / or an inductor. It is also conceivable that these common conductors are radiators, i.e., elements that constitute a significant share of the antenna's radiation. In a preferred embodiment, the first interference-suppressing transmitting antenna and the body coil may be a birdcage antenna, wherein the common conductor element is the end loop of two birdcage antennas.

[0021] The interference suppression signal for the interference suppression transmitting antenna can be advantageously generated directly from the excitation signal via the common conductor element. For example, phase shifting can be achieved through the sizing design of the interference suppression transmitting antenna, thereby enabling the antenna to emit an interference suppression signal with opposite phases for destructive interference.

[0022] In one feasible embodiment of the magnetic resonance tomography apparatus according to the invention, the transmitter is designed to control a first transmit interference suppression transmit antenna via a first interference suppression signal at a first signal input terminal according to an excitation signal. The transmitter may, for example, have a separate output stage or a distribution network.

[0023] The transmitter's own signal output for the interference suppression signal advantageously allows the interference suppression signal to be changed in one or more parameters independently of the excitation signal.

[0024] In one feasible embodiment of the magnetic resonance tomography apparatus according to the present invention, the magnetic resonance tomography apparatus is designed to generate a first interference suppression signal having a predetermined attenuation and / or phase shift from an excitation signal.

[0025] For example, phase shifting and attenuation can be achieved through passive networks, such that the electromagnetic fields emitted by the body coil and the interference suppression transmitting antenna are maximally canceled outside the patient channel. However, it is also conceivable that the transmitter has one or more channels through which interference suppression signals are provided accordingly, for example, by generating phase shifts and attenuation through digital signal processing or synthesizing signals with the desired characteristics.

[0026] When the interference suppression signal is generated by the transmitter, the interference suppression signal can also be advantageously varied in multiple parameters between individual sequences, and each channel can be adapted independently to respond, for example, to changes in electromagnetic propagation characteristics caused by the patient.

[0027] In one feasible embodiment of the magnetic resonance imaging (MRI) apparatus according to the invention, the MRI apparatus includes an interference sensor. The interference sensor is a sensor or antenna designed to receive electromagnetic interference signals, particularly interference signals with the frequency of an excitation signal. This can be, for example, an inductive loop or an electric antenna, and includes a preamplifier, a filter, or an analog-to-digital converter. The interference sensor is positioned outside the patient access channel, or at least positioned such that it is closer to a first interference suppression transmitting antenna than to a body coil. The interference sensor is preferably signal-connected to a transmitter to transmit a detected interference suppression signal to the transmitter. The first interference suppression transmitting antenna has a second signal input. The MRI apparatus is designed to control the first interference suppression transmitting antenna via the second signal input with a second interference suppression signal, wherein the MRI apparatus is designed to generate the second interference suppression signal based on the signal from the interference sensor.

[0028] The transmitter or transmission interference suppression controller of a magnetic resonance imaging (MRI) device can, for example, generate an interference suppression signal from the received interference signal through filtering, amplification, and phase shifting. This interference suppression signal, when transmitted through a first and / or second interference suppression transmitting antenna, reduces interference radiation generated by the excitation signal through destructive interference. Alternatively, the intensity of the emitted excitation signal can be detected at the location of the interference sensor using the received interference signal, and the interference suppression signal can be modified so that the destructive interference between the interference suppression signal and the excitation signal minimizes the intensity of the interference signal at the interference sensor, for example, through linear optimization methods such as LSR.

[0029] Interference sensors are advantageously adaptable to changing conditions and thus capable of achieving optimal interference suppression in all situations.

[0030] In one feasible embodiment of the magnetic resonance imaging apparatus according to the invention, the apparatus has an additional third interference-suppressing transmitting antenna. This third interference-suppressing transmitting antenna has monopole characteristics. Monopole characteristics are similar to those of an electrical monopole or rod antenna, but unlike a bipole, it does not have two poles in opposite phase. The radiation characteristics are particularly similar to those of a patient's body, which receives excitation pulses within a patient channel, transmits the excitation pulses like an inner conductor in a waveguide, and emits the excitation pulses, for example, through feet located outside the patient channel. The third transmitting antenna is preferably an electrical or capacitive antenna, i.e., the third transmitting antenna preferably generates an alternating electric field in the near field to compensate for the electric field emitted by the patient's body as a conductor.

[0031] The third interference suppression transmitting antenna is preferably arranged in the patient passageway; however, it can also be arranged at an opening in front of the patient passageway, for example, in front of each opening. The foregoing description of the first interference suppression signal, especially whether it is generated by a passive network, actively generated, or optimized by an interference sensor, also applies accordingly to the generation of the interference signal.

[0032] The monopole characteristic of the third interference suppression transmitting antenna allows it to compensate for different radiations from the body in a more advantageous manner than the first and / or second interference suppression transmitting antennas. Attached Figure Description

[0033] The foregoing features, characteristics, and advantages of the present invention, as well as the ways and means of achieving said features, characteristics, and advantages, will become clearer in conjunction with the following description of the embodiments, which will be explained in detail with reference to the accompanying drawings.

[0034] In the attached diagram:

[0035] Figure 1A schematic diagram illustrating an embodiment of a magnetic resonance tomography apparatus with an interference-suppressing transmitting antenna according to the present invention is shown;

[0036] Figure 2 A schematic diagram showing the physical coil, the first interference suppression transmitting antenna, and the second interference suppression transmitting antenna according to a feasible embodiment of the present invention;

[0037] Figure 3 A schematic diagram showing the body coil, the first interference suppression transmitting antenna, and the second interference suppression transmitting antenna according to another feasible embodiment of the present invention;

[0038] Figure 4 A schematic diagram illustrating an embodiment of the interference suppression emission device according to the present invention is shown;

[0039] Figure 5 A schematic diagram showing another feasible embodiment of the body coil having a third interference suppression transmitting antenna according to the present invention is shown;

[0040] Figure 6 A schematic flowchart illustrating an embodiment of the method according to the present invention is shown. Detailed Implementation

[0041] Figure 1 A schematic diagram showing an embodiment of a magnetic resonance tomography apparatus 1 having an interference suppression transmitting antenna 60 according to the present invention is shown.

[0042] The magnet unit 10 has a field magnet 11 that generates a static magnetic field B0, which is used to orient the atomic spins of the sample or patient 100 in the containment region. The containment region is characterized by an extremely uniform static magnetic field B0, wherein uniformity refers particularly to the magnetic field strength or magnitude. The containment region is approximately spherical and is arranged in a patient channel 16 extending longitudinally 2 through the magnet unit 10. The patient platform 30 is movable within the patient channel 16 via a movement unit 36. The field magnet 11 is typically a superconducting magnet capable of providing magnetic fields with flux densities up to 3T and even higher in state-of-the-art devices. However, for lower field strengths, permanent magnets or electromagnets with normally conductive coils can also be used.

[0043] Furthermore, the magnet unit 10 has a gradient coil 12 designed to superimpose a variable magnetic field with the magnetic field B0 along three spatial directions to spatially distinguish imaging regions detected within the examination volume. The gradient coil 12 is typically a coil composed of normally conductive wire, capable of generating mutually orthogonal fields within the examination volume.

[0044] The magnet unit 10 also has a body coil 14, which is designed to radiate high-frequency signals input via signal lines into the examination volume and to receive and output resonant signals emitted by the patient 100 via signal lines. The term "transmitting antenna" refers to an antenna through which high-frequency signals for exciting atomic nuclei spin are transmitted. This can be the body coil 14, but it can also be a local coil 50 with transmitting capabilities.

[0045] The control unit 20 provides different signals to the magnet unit 10 for the gradient coil 12 and the body coil 14 and analyzes the received signals.

[0046] The control unit 20 has a gradient control device 21 designed to supply a variable current to the gradient coil 12 via an input line that provides the desired gradient field in the inspection volume in a time-coordinated manner.

[0047] Furthermore, the control unit 20 has a high-frequency unit 22 designed to generate high-frequency pulses with predetermined time variations, amplitudes, and spectral power distributions to excite the magnetic resonance of the atomic spins of the patient 100. Pulse power in the kilowatt range can be achieved here. The excitation signal can be radiated into the patient 100 via the body coil 14 or also via a local transmitting antenna.

[0048] The control device 23 communicates with the gradient control device 21 and the high-frequency unit 22 via the signal bus 25.

[0049] A local coil 50 is arranged on the patient 100 as a first receiving antenna, and the local coil is connected to the high-frequency unit 22 and its receiver via a connecting line 33. However, it is also conceivable that the body coil 14 is the first receiving antenna in the sense of this invention.

[0050] The magnetic resonance imaging (MRI) device 1 also has two interference-suppressing transmitting antennas 60 and 61 in the patient passage. These antennas are respectively positioned between the opening of the patient passage 16 and the body coil 14, such that the body coil 14 is located longitudinally 2 within the patient passage between the first interference-suppressing transmitting antenna 60 and the second interference-suppressing transmitting antenna 61. However, it is also possible that the opening of the patient passage 14 has a shielding grid or that the patient passage 14 has only one opening. In this case, only one interference-suppressing transmitting antenna 60 is arranged between the body coil 14 and the opening.

[0051] The first interference suppression transmitting antenna 60 and the second interference suppression transmitting antenna 61 preferably have similar transmission characteristics to the body coil 14. This should be understood as follows: when controlled by excitation and interference suppression signals, the electromagnetic waves radiated by the interference suppression transmitting antennas 60, 61 and the body coil 14 have substantially the same spatial distribution and preferably the same phase, such that the fields cancel each other out and substantially cancel each other out at a predetermined location after one or more cycles. This predetermined location is in the far field of the body coil 14.

[0052] In its simplest form, this can be achieved by having the interference suppression transmitting antennas 60 and 61 and the body coil 14 have the same construction type, for example, all being birdcage antennas. Other feasibility is illustrated in the following figures.

[0053] One or more interference sensors 71 are located outside the patient channel, preferably in the far field of the body coil, at a distance greater than half or the entire wavelength of the electromagnetic wave having the frequency of the excitation signal. The combined action of the interference sensors 71 with the one or more interference suppression transmitting antennas 60, 61, 62 is illustrated with reference to the following figures.

[0054] Figure 2 A schematic diagram of a feasible embodiment of the body coil 14, the first interference suppression transmitting antenna 60, and the second interference suppression transmitting antenna 61 according to the invention is shown. The patient channel 16 and other components of the magnetic resonance imaging apparatus 1 according to the invention are not shown for clarity of illustration.

[0055] The body coil 14 and the interference-suppressing transmitting antennas 60 and 61 are designed here as so-called birdcage antennas, wherein the two end loops are connected along the longitudinal direction 2 by conductor rods. Alternatively, the conductor rods may have breaks in the conductor rods, into which capacitors or inductors are added, to increase or decrease the electrical wavelength for high-frequency signals and / or generate a phase shift for high-frequency signals, for example.

[0056] HA and HB represent two signal input terminals, which provide a first interference suppression signal and a second interference suppression signal to the interference suppression transmitting antennas 60 and 61. Figure 2 In the illustrated embodiment, the feed point for providing the interference suppression signal is positioned at a position rotated 90 degrees around the longitudinal direction 2, thereby generating a circumferential polarized field by the interference suppression transmitting antennas 60 and 61 through a second interference suppression signal that is 90 degrees phase-shifted relative to the first interference suppression signal. This field corresponds to the circumferential polarized field generated by the body coil 14, and can reduce the electromagnetic field emitted by the body coil 14 along the longitudinal direction 2 outside the patient channel through destructive interference when the frequency is correspondingly the same, the phase position and amplitude are correspondingly appropriate.

[0057] The control of the body coil 14 via excitation signals is not shown. This control can be implemented by feeding two excitation signals with a 90-degree phase shift between them at two feed points relative to the feed points of the interference suppression transmitting antennas 60 and 61. However, it is also conceivable to feed a corresponding number of excitation signals to the body coil 14 through a greater number of mutually offset feed points.

[0058] Each individual interference suppression signal and excitation signal is preferably generated by its own high-frequency stage, which provides more degrees of freedom in excitation and interference suppression. However, it is also possible to derive the excitation signal and / or interference suppression signal from a single signal using passive devices, such as a distribution network.

[0059] Figure 3 A specific implementation method for passively generating excitation signals is shown.

[0060] exist Figure 3 In this configuration, the interference suppression transmitting antennas 60 and 61 and the body coil 14 are directly, electrically and mechanically coupled, because the end loop of the body coil 14 is also the end loop of the adjacent interference suppression transmitting antennas 60 and 61. The strength of the coupling, or the strength of the interference suppression transmitting antennas 60 and 61, can thus be adjusted, for example, by the magnitude of the impedance, which is represented by a cone arranged in the outer end loop of the interference suppression transmitting antenna 60 away from the body coil 14.

[0061] An alternative embodiment of the invention is that the interference suppression transmitting antennas 60 and 61 have a plurality of feed points for inputting interference suppression signals, and these feed points are generated partly passively and partly actively.

[0062] Figure 4 This illustrates the possibility of actively providing an interference suppression signal via a transmitter in one embodiment of the invention.

[0063] The transmitter or high-frequency unit 22 has an interference suppression transmission device 70. The transmission interference suppression controller 72 can be implemented as a functional unit of the transmitter, or it can be implemented in software, or it can be implemented as dedicated hardware. Analog or digital technologies can be used, such as digital signal processors (DSPs), FPGAs, or analog amplifiers, filters, or networks.

[0064] exist Figure 4In an exemplary embodiment, the transmit interference suppression controller 72 of the interference suppression transmitter 70 receives a signal from the directional coupler 75, the signal containing information about the excitation signal emitted by the body coil. In particular, when the amplification of the signal from the high-frequency amplifier 74 used to amplify the interference suppression transmitter antennas 60, 61, 62 is known, the transmit interference suppression controller 72, as the signal generator, already possesses information about the emitted interference suppression signal. However, it is also conceivable that the directional coupler or a simple inductive, capacitive, or resistive coupler would also receive the interference suppression signal for the transmit interference suppression controller 72 to account for deviations in the transmission path. The interference suppression transmitter antennas 61 and 62 are shown symbolically only for illustrative purposes.

[0065] One consideration is to initially transmit only the excitation signal or the interference suppression signal during the calibration phase, and have it received by the interference sensor 71, to determine the transfer function, so that the attenuation and phase shift between the interference sensor 71 and the body coil 14 or the interference suppression transmitting antennas 60, 61, 62 can then be determined using the transmit interference suppression controller 72. Figure 4 The diagram shows a digital interference sensor 71 that digitizes the received signal and digitally transmits the information to a transmit interference suppression controller 72. However, it is equally conceivable to perform the transmission analogically in an analog interference sensor 71.

[0066] In addition, the emission interference suppression controller 72 in Figure 4 Information about the excitation signal is received through a feed point arranged on the body coil 14 in order to detect the current flowing through the body coil 14 as accurately as possible and thereby detect the emitted alternating field. For example, it is also possible to output a portion of the coupling signal through a voltage divider or to directly extract a portion of the coupling signal from the information about the generation of the excitation signal.

[0067] By using the transfer function between the body coil 14 and the interference sensor 71, the interference suppression controller 72 can determine the expected interference signal for the excitation signal at the interference sensor 71, and also determine the inverse interference suppression signal to be transmitted by applying the inverse transfer function between the interference sensor 71 and the interference suppression transmitting antennas 60, 61, 62.

[0068] For multiple interference suppression transmitting antennas 60, 61, 62 and interference sensor 71, it is particularly conceivable to minimize the energy of the alternating field generated at interference sensor 71 by means of linear optimization when excitation signals and one or more interference suppression signals are emitted simultaneously. Variable parameters here can be the phase shift and attenuation or amplification of the excitation signal, thereby determining the corresponding interference suppression signal for interference suppression transmitting antennas 60, 61, 62. This can be achieved either during the calibration phase to determine initial values ​​for the parameters or during image acquisition to respond to propagation conditions altered by the patient.

[0069] Figure 5 A third interference suppression transmitting antenna 62 is shown, which is arranged here as a flat electrode in the patient tunnel within the body coil 14. The third interference suppression transmitting antenna 62 is also provided with an interference suppression signal by the interference suppression transmitting device 70. Due to the low conductivity of the patient 100 compared to the elements of the body coil, the induced current is low, but primarily an alternating electric field is established, which is also conducted along the body from the patient tunnel. When appropriately controlled by the transmitting interference suppression controller, the electrode can directly and without detour generate a counteracting alternating electric field through the induced magnetic field and input this alternating electric field into the patient 100. However, besides the electrode shown, the third interference suppression transmitting antenna could also be any other antenna type capable of generating a suitable alternating electric field.

[0070] Figure 6 A schematic flowchart illustrating an embodiment of the method according to the present invention is shown.

[0071] In step S10, the magnetic resonance imaging device 1 transmits an excitation signal from the high-frequency unit 22 via the body coil 14. The excitation signal is preferably an excitation pulse used to excite the spins of the atomic nuclei to be detected in an imaging sequence.

[0072] In step S20, the interference suppression transmitting device 70 simultaneously emits a first interference suppression signal via the first interference suppression transmitting antenna 60. Alternatively, interference suppression signals can be emitted simultaneously via the second interference suppression transmitting antennas 61 and / or 62. The interference suppression signal can be a preset signal or derived from the excitation signal according to a predetermined rule. The interference suppression signal is designed to reduce the excitation signal through destructive interference at at least one predetermined location outside the magnetic resonance computed tomography scanner 1 during simultaneous transmission.

[0073] In a preferred embodiment of the method according to the invention, the magnetic resonance imaging device 1 has an interference sensor 71. In another step S30, an interference signal is detected by the interference sensor 71. In another step S40, the interference suppression emission device 70 determines a modified first interference suppression signal generated by the magnetic resonance imaging device 1 based on the detected interference signal, wherein the modified interference suppression signal is designed to reduce the energy of the interference signal. This can be achieved, for example, by modeling the signal propagation or by applying a transfer function to the excitation signal and the received interference signal, as described.

[0074] Finally, in step S50, step S10 of emitting an excitation signal and step S20 of emitting an interference suppression signal are performed with the modified first interference suppression signal.

[0075] Another consideration is to repeat these steps multiple times, especially during the calibration phase prior to measurement, to improve interference suppression, in which, for example, transmission is performed without a patient 100, thus protecting the patient from SAR load. Alternatively, all signals can be scaled with a common factor to calibrate at low power, and then boosted with the same factor during image detection. This linearity preserves the attenuation of interference.

[0076] Although the invention has been described and illustrated in detail with reference to preferred embodiments, the invention is not limited to the disclosed examples, or other variations can be derived by those skilled in the art without departing from the scope of protection of the invention.

Claims

1. A magnetic resonance imaging (MRI) device, comprising a transmitter for generating an excitation signal and a body coil (14) for emitting the excitation signal, wherein, The magnetic resonance imaging device (1) has a patient channel (16) with the body coil, wherein the magnetic resonance imaging device (1) has a first interference suppression transmitting antenna (60) arranged between the body coil (14) and the opening of the patient channel (16), wherein, by means of the above-described arrangement of the first interference suppression transmitting antenna (60) and the body coil (14), the first interference suppression transmitting antenna (60) is designed to provide spatial transmission characteristics similar to those of the body coil (14), such that a high-frequency signal generated by the excitation signal and the first interference suppression signal transmitted through the first interference suppression transmitting antenna (60) is transmitted from the opening of the patient channel (16), the high-frequency signal having lower energy and field strength than when there is no first interference suppression signal.

2. The magnetic resonance tomography device according to claim 1, wherein, The magnetic resonance imaging device (1) has a second interference suppression transmitting antenna (61), and the body coil (14) is arranged along the longitudinal axis of the patient channel (16) between the first interference suppression transmitting antenna (60) and the second interference suppression transmitting antenna (61).

3. The magnetic resonance tomography device according to claim 1, wherein, The first interference suppression transmitting antenna (60) and the body coil (14) are of the same type.

4. The magnetic resonance tomography device according to claim 3, wherein, The first interference suppression transmitting antenna (60) and the body coil (14) have a common electrical conductor.

5. The magnetic resonance tomography apparatus according to any one of claims 1 to 4, wherein, The transmitter is designed to control a first transmission interference suppression transmitting antenna (60) via a first interference suppression signal through a first signal input terminal according to an excitation signal.

6. The magnetic resonance tomography device according to claim 5, wherein, The magnetic resonance tomography device (1) is designed to generate a first interference suppression signal with predetermined attenuation and / or phase shift from the excitation signal.

7. The magnetic resonance tomography device according to claim 5, wherein, The magnetic resonance imaging device (1) has an interference sensor (71), and the first interference suppression transmitting antenna (60) has a second signal input terminal. The magnetic resonance imaging device (1) is designed to control the first interference suppression transmitting antenna (60) with a second interference suppression signal via the second signal input terminal. The magnetic resonance imaging device (1) is designed to generate a second interference suppression signal based on the signal from the interference sensor (71).

8. The magnetic resonance tomography device according to claim 1, wherein, The magnetic resonance imaging device (1) has a third interference suppression transmitting antenna (62), which has a single-pole characteristic. The magnetic resonance imaging device (1) is designed to control the third interference suppression transmitting antenna (62) with a third interference suppression signal.

9. A method of operating a magnetic resonance tomography apparatus (1) according to any one of claims 1 to 8, wherein, The magnetic resonance imaging device (1) has a body coil (14) in a patient channel (16) and a first interference suppression transmitting antenna (60), wherein the first interference suppression transmitting antenna (60) is arranged between the body coil (14) and the opening of the patient channel (16), wherein the first interference suppression transmitting antenna (60) is designed to provide transmission characteristics similar to those of the body coil (14), wherein the method has the following steps: (S10) The magnetic resonance imaging device (1) transmits an excitation signal by means of the body coil (14); (S20) Simultaneously transmit the first interference suppression signal using the first interference suppression transmitting antenna (60).

10. The method according to claim 9, wherein, The magnetic resonance tomography device (1) also has an interference sensor (71), wherein the method further includes the following steps: (S30) The interference signal is detected by the interference sensor (71); (S40) Determine a modified first interference suppression signal generated by the magnetic resonance imaging device (1) based on the measured interference signal, wherein the modified first interference suppression signal is designed to reduce the energy of the interference signal; (S50) Repeat the transmit excitation signal in step (S10) and the transmit interference suppression signal in step (S20) with the changed first interference suppression signal.

Images