CN220711462U - Filter and magnetic resonance imaging system - Google Patents

Abstract

Embodiments of the present application provide a filter and a magnetic resonance imaging system, the filter including: a first input terminal and a second input terminal that receive an input signal; a first inductor comprising a first winding, a first end of the first winding being connected to the first input terminal; a series resonant circuit having one end connected to the second end of the first winding and the other end connected to the second input terminal; and a first output terminal and a second output terminal, which supply a driving signal to the gradient coil, the first output terminal being connected to one end of the series resonant circuit, and the second output terminal being connected to the other end of the series resonant circuit.

Description

Filter and magnetic resonance imaging system

Technical Field

The embodiment of the application relates to the technical field of medical equipment, in particular to a filter and a magnetic resonance imaging system.

Background

Magnetic Resonance Imaging (MRI) techniques have been widely used in the field of medical diagnostics. Magnetic resonance imaging provides detailed images of soft tissue, abnormal tissue (such as tumors) and other structures that cannot be easily imaged by other imaging modalities such as Computed Tomography (CT). Magnetic resonance imaging operates without exposing the patient to ionizing radiation experienced in, for example, CT and X-rays.

The magnetic resonance system generally comprises a main magnet, a gradient amplifier, a radio frequency amplifier, a gradient coil, a transmitting chain module, a transmitting/receiving coil, a receiving chain module and the like, wherein the transmitting chain module generates pulse signals and transmits the pulse signals to the transmitting/receiving coil, the transmitting/receiving coil generates radio frequency excitation signals to excite a scanning object to generate magnetic resonance signals, after excitation, the magnetic resonance signals are acquired by the transmitting/receiving coil through spatial coding, and medical images are reconstructed.

The quality of images produced by magnetic resonance imaging systems is often affected by their electronic components. For example, if there is ripple, oscillation, or the like in the drive signal input to the gradient coil by the gradient amplifier, the quality of the MRI image is significantly affected.

In current ripple or oscillation cancellation circuits, a transformer is typically provided that galvanically couples the primary coil to the secondary coil. The notch filter is connected with the secondary coil and used for filtering current ripples. However, the notch point of the notch filter cannot be accurately controlled at a preset frequency due to the influence of leakage inductance of the transformer.

Disclosure of Invention

The embodiment of the application provides a filter and a magnetic resonance imaging system.

According to an aspect of embodiments of the present application, there is provided a filter applied to a gradient amplifier, wherein the filter includes: a first input terminal and a second input terminal that receive an input signal; a first inductor comprising a first winding, a first end of the first winding being connected to the first input terminal; a series resonant circuit having one end connected to the second end of the first winding and the other end connected to the second input terminal; and a first output terminal and a second output terminal, which supply a driving signal to the gradient coil, the first output terminal being connected to one end of the series resonant circuit, and the second output terminal being connected to the other end of the series resonant circuit.

In some embodiments, the series resonant circuit includes a second inductor and a second capacitor connected in series, the resonant frequency of the series resonant circuit including the switching frequency of the input signal.

In some embodiments, the filter further comprises: a gain adjustment circuit comprising a resistor and a first capacitor connected in series is connected in parallel with the series resonant circuit.

In some embodiments, the first inductor further comprises a second winding, a first end of the second winding being connected to the second input terminal, a second end of the second winding being connected to the other end of the series resonant circuit.

In some embodiments, the core of the first inductor comprises an EI core, and the first winding and the second winding are located on either side of a center leg of the EI core, respectively.

In some embodiments, the EI core comprises: the first EI iron core comprises a first E iron core and a first I iron core, wherein the first E iron core comprises a first bottom plate, a first central column perpendicular to the first bottom plate and two first side columns positioned on two sides of the first central column; the second EI iron core comprises a second E iron core and a second I iron core, the second E iron core comprises a second bottom plate, a second center column perpendicular to the second bottom plate and two second side columns located on two sides of the second center column, and the first bottom plate is in butt joint with the second bottom plate.

In some embodiments, the first winding wraps around the first base plate and the second base plate via a first gap between the first center post and one of the first side posts, a second gap between a second center post and one of the second side posts; the second winding is wound around the first base plate and the second base plate via a third gap between the first center post and the other of the first side posts, and a fourth gap between the second center post and the other of the second side posts.

In some embodiments, a fifth gap is formed between the first center leg and the first I-core; and/or a sixth gap is formed between the second center post and the second I-core.

In some embodiments, two of the first jambs abut the first I-core; and/or the two second side posts are in butt joint with the second I iron core.

According to an aspect of embodiments of the present application, there is provided a magnetic resonance imaging system, the system comprising: a gradient coil; and a gradient amplifier outputting a driving signal to the gradient coil, the gradient amplifier including the aforementioned filter.

One of the beneficial effects of the embodiment of the application is that: in a filter of a gradient amplifier, a first end of a first winding of a first inductor is connected with a first input terminal, a second end of the first winding is connected with one end of a series resonant circuit, the other end of the series resonant circuit is connected with a second input terminal, and a first output terminal and a second output terminal are respectively connected with one end and the other end of the series resonant circuit, so that ripple current can be directly filtered through the first inductor and the series resonant circuit, higher ripple filtering efficiency is achieved, and reliability of ripple filtering can be improved.

Specific implementations of the embodiments of the present application are disclosed in detail with reference to the following description and drawings, indicating the manner in which the principles of the embodiments of the present application may be employed. It should be understood that the embodiments of the present application are not limited in scope thereby. The embodiments of the present application include many variations, modifications and equivalents within the spirit and scope of the appended claims.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. It is obvious that the drawings in the following description are only examples of the present application, and that other embodiments may be obtained from these drawings without inventive work for a person of ordinary skill in the art. In the drawings:

FIG. 1 is a magnetic resonance imaging system of some embodiments of the present application;

FIG. 2 is a schematic diagram of a gradient amplifier and gradient coil according to an embodiment of the present application;

FIG. 3 is a schematic diagram of a filter according to an embodiment of the present application;

FIG. 4 is a schematic diagram of the frequency response of a filter according to an embodiment of the present application;

FIG. 5 is another schematic diagram of a filter of an embodiment of the present application;

FIG. 6 is a schematic diagram of a first inductor according to an embodiment of the present application;

FIG. 7 is a schematic diagram of a lumped model of a filter and gradient coil in accordance with an embodiment of the present application;

fig. 8 is another schematic diagram of a filter and gradient coil lumped model in accordance with an embodiment of the present application.

Detailed Description

The foregoing and other features of embodiments of the present application will become apparent from the following description, taken in conjunction with the accompanying drawings. In the specification and drawings, there have been specifically disclosed specific embodiments of the present application which are indicative of some of the ways in which the principles of the embodiments of the present application may be employed, it being understood that the present application is not limited to the described embodiments, but, on the contrary, the embodiments of the present application include all modifications, variations and equivalents falling within the scope of the appended claims.

In the embodiments of the present application, the terms "first," "second," and the like are used to distinguish between different elements from each other by reference, but do not denote a spatial arrangement or a temporal order of the elements, and the elements should not be limited by the terms. The term "and/or" includes any and all combinations of one or more of the associated listed terms. The terms "comprises," "comprising," "including," "having," and the like, are intended to reference the presence of stated features, elements, components, or groups of components, but do not preclude the presence or addition of one or more other features, elements, components, or groups of components.

In the embodiments of the present application, the singular forms "a," an, "and" the "include plural referents and should be construed broadly to mean" one "or" one type "and not limited to" one "or" another; furthermore, the term "comprising" is to be interpreted as including both the singular and the plural, unless the context clearly dictates otherwise. Furthermore, the term "according to" should be understood as "at least partially according to … …", and the term "based on" should be understood as "based at least partially on … …", unless the context clearly indicates otherwise.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments in combination with or instead of the features of the other embodiments. The term "comprises/comprising" when used herein refers to the presence of a feature, integer, step or component, but does not exclude the presence or addition of one or more other features, integers, steps or components.

For ease of understanding, fig. 1 illustrates a Magnetic Resonance Imaging (MRI) system 100 of some embodiments of the present application.

The MRI system 100 comprises a scanning unit 111. The scanning unit 111 is adapted for magnetic resonance scanning of an object (e.g. a human body) 170 to generate image data of a region of interest of the object 170, which may be a predetermined anatomical site or tissue.

The operation of the MRI system 100 is controlled by an operator workstation 110, which operator workstation 110 includes an input device 114, a control panel 116, and a display 118. The input device 114 may be a joystick, keyboard, mouse, trackball, touch activated screen, voice control, or any similar or equivalent input device. The control panel 116 may include a keyboard, touch-activated screen, voice control, buttons, sliders, or any similar or equivalent control device. The operator workstation 110 is coupled to and communicates with a computer system 120 that enables an operator to control the generation and viewing of images on the display 118. Computer system 120 includes a plurality of components that communicate with each other via electrical and/or data connection modules 122. The connection module 122 may be a direct wired connection, a fiber optic connection, a wireless communication link, or the like. Computer system 120 may include a Central Processing Unit (CPU) 124, a memory 126, and an image processor 128. In some embodiments, the image processor 128 may be replaced by a medical imaging function implemented in the CPU 124. Computer system 120 may be connected to an archive media device, permanent or backup storage, or a network. The computer system 120 may be coupled to and in communication with a separate MRI system controller 130.

The MRI system controller 130 includes a set of components that communicate with each other via electrical and/or data connection modules 132. The connection module 132 may be a direct wired connection, a fiber optic connection, a wireless communication link, or the like. MRI system controller 130 may include a CPU131, a sequence pulse generator (or pulse generator) 133 in communication with operator workstation 110, a transceiver (or RF transceiver) 135, a memory 137, and an array processor 139. In some embodiments, the sequence pulse generator 133 may be integrated into the resonance component 140 of the scanning unit 111 of the MRI system 100. The MRI system controller 130 may receive commands from the operator workstation 110, coupled to the scanning unit 111, to indicate MRI scan sequences to be performed during an MRI scan, for controlling the scanning unit 111 to perform the procedure of the magnetic resonance scan described above. The MRI system controller 130 is also coupled to and in communication with a gradient driver system (or gradient driver) 150 that is coupled to a gradient coil assembly 142 to generate magnetic field gradients during MRI scanning.

The sequencer 133 may also receive data from a physiological acquisition controller 155 that receives signals from a plurality of different sensors, such as Electrocardiogram (ECG) signals from electrodes attached to a patient, which are connected to the patient or subject 170 undergoing an MRI scan. The sequencer 133 is coupled to and in communication with a scan room interface system 145 that receives signals from various sensors associated with the state of the resonant assembly 140. The scan room interface system 145 is also coupled to and in communication with a patient positioning system 147 that transmits and receives signals to control the movement of the patient table to a desired position for MRI scanning.

The MRI system controller 130 supplies gradient waveforms to a gradient driver system 150 including a Gx amplifier 151 in the x direction, a Gy amplifier 152 in the y direction, a Gz amplifier 153 in the z direction, and the like (the Gx amplifier, gy amplifier, and Gz amplifier may also be referred to as a Gx gradient amplifier, a Gy gradient amplifier, and a Gz gradient amplifier, respectively, or simply as a gradient amplifier). Each gradient amplifier 151, 152, 153 excites a corresponding gradient coil in the gradient coil assembly 142 to produce magnetic field gradients used for spatially encoding MR signals during an MRI scan. The gradient coil assembly 142 is disposed within the resonance assembly 140, which also includes a superconducting magnet having a superconducting coil 144 that, in operation, provides a static uniform longitudinal magnetic field b_0 throughout a cylindrical imaging volume 146. The resonant assembly 140 also includes an RF body coil 148 that, in operation, provides a transverse magnetic field b_1 that is substantially perpendicular to b_0 throughout the cylindrical imaging volume 146. The resonance assembly 140 may further include an RF surface coil 149 for imaging different anatomical structures of a patient undergoing an MRI scan. The RF body coil 148 and RF surface coil 149 may be configured to operate in transmit and receive modes, transmit mode, or receive mode.

The x-direction may also be referred to as the frequency encoding direction or the kx-direction in K-space, and the y-direction may be referred to as the phase encoding direction or the ky-direction in K-space. Gx may be used for frequency encoding or signal readout, commonly referred to as frequency encoding gradients or readout gradients. Gy may be used for phase encoding, commonly referred to as phase encoding gradients. Gz may be used for slice (layer) position selection to obtain K-space data. It should be noted that the layer selection direction, the phase encoding direction and the frequency encoding direction may be modified according to actual needs.

An MRI scanned object or patient 170 may be positioned within the cylindrical imaging volume 146 of the resonance assembly 140. The transceiver 135 in the MRI system controller 130 generates RF excitation pulses that are amplified by the RF amplifier 162 and provided to the RF body coil 148 through a transmit/receive switch (T/R switch) 164.

As described above, the RF body coil 148 and RF surface coil 149 may be used to transmit RF excitation pulses and/or to receive resulting MR signals from a patient undergoing an MRI scan. MR signals emitted by excited nuclei within the patient of an MRI scan may be sensed and received by the RF body coil 148 or the RF surface coil 149 and sent back to the preamplifier 166 through the T/R switch 164. The T/R switch 164 may be controlled by a signal from the sequence pulse generator 133 to electrically connect the RF amplifier 162 to the RF body coil 148 during a transmit mode and to connect the preamplifier 166 to the RF body coil 148 during a receive mode. The T/R switch 164 may also enable the RF surface coil 149 to be used in either a transmit mode or a receive mode.

In some embodiments, MR signals sensed and received by the RF body coil 148 or RF surface coil 149 and amplified by the pre-amplifier 166 are stored as an array of raw k-space data in the memory 137 for post-processing. A reconstructed magnetic resonance image can be acquired by transforming/processing the stored raw k-space data.

In some embodiments, the MR signals sensed and received by the RF body coil 148 or RF surface coil 149 and amplified by the pre-amplifier 166 are demodulated, filtered, and digitized in the receive portion of the transceiver 135 and transferred to the memory 137 in the MRI system controller 130. For each image to be reconstructed, the data is rearranged into separate k-space data arrays, and each of these separate k-space data arrays is input to an array processor 139 that is operative to fourier transform the data into an array of image data.

The array processor 139 uses a transformation method, most commonly a fourier transform, to create an image from the received MR signals. These images are transferred to computer system 120 and stored in memory 126. In response to commands received from the operator workstation 110, the image data may be stored in long term memory or may be further processed by the image processor 128 and transferred to the operator workstation 110 for presentation on the display 118.

In various embodiments, the components of the computer system 120 and the MRI system controller 130 may be implemented on the same computer system or multiple computer systems. It should be understood that the MRI system 100 shown in FIG. 1 is for illustration. Suitable MRI systems may include more, fewer, and/or different components.

The MRI system controller 130, the image processor 128 may include a computer processor and a storage medium on which a program of predetermined data processing to be executed by the computer processor is recorded, respectively or in common, for example, a program for performing a scanning process (e.g., a scanning procedure, an imaging sequence), image reconstruction, medical imaging, or the like may be stored, for example, a program for performing a magnetic resonance imaging method of an embodiment of the present utility model may be stored. The storage medium may include, for example, ROM, floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, or nonvolatile memory card.

Fig. 2 is a schematic diagram of a gradient amplifier 200 and a gradient coil 400 according to an embodiment of the present application, wherein the gradient amplifier 200 may be any one of the Gx amplifier 151, gy amplifier 152, and Gz amplifier 153 in fig. 1. As shown in fig. 2, the gradient amplifier 200 includes an H-bridge circuit 202, and the H-bridge circuit 202 may include a plurality of stacked H-bridges, which may include IGBTs that may be driven by a PWM (pulse width modulation) controller 205 in accordance with a pulse width modulation algorithm. Among them, the PWM controller 205 can generate a waveform having a switching frequency (Switching frequency) by controlling the H-bridge circuit 202. An output of the H-bridge circuit 202 is connected to an input of the filter 300, and the generated waveform is supplied as an input signal Vi to the filter 300. The filter 300 filters the received input signal Vi to generate an output signal Vo. The output signal Vo is supplied as a driving signal to the gradient coil 400. It is noted that fig. 2 exemplarily shows a gradient amplifier including an H-bridge circuit, to which the present application is not limited, and the gradient amplifier may be of other structures.

The inventors have found that in current ripple or oscillation cancelling circuits, a transformer is typically provided that galvanically couples the primary coil to the secondary coil. The filter is connected with the secondary coil and is used for filtering current ripple. However, due to the influence of leakage inductance of the transformer, the notch point of the filter is often not accurately controlled at a predetermined frequency, and thus the ripple cannot be reliably filtered.

In view of at least one of the above problems, embodiments of the present application provide a filter and a magnetic resonance imaging system, which are described below with reference to the embodiments.

The embodiment of the application provides a filter, which is applied to a gradient amplifier.

Fig. 3 is a schematic diagram of a filter according to an embodiment of the present application, and as shown in fig. 3, a filter 300 includes: a first input terminal 301, a second input terminal 302, a first inductor 307, a series resonant circuit 303, a first output terminal 304, and a second output terminal 305.

Wherein the first input terminal 301 and the second input terminal 302 receive an input signal Vi; the first inductor 307 includes a first winding, a first end of which is connected to the first input terminal 301; one end of the series resonant circuit 303 is connected to the second end of the first winding, and the other end of the series resonant circuit 303 is connected to the second input terminal 302; the first output terminal 304 and the second output terminal 305 supply the driving signal Vo to the gradient coil, the first output terminal 304 is connected to one end of the series resonant circuit 303, and the second output terminal 305 is connected to the other end of the series resonant circuit 303.

According to the above embodiment, in the filter of the gradient amplifier, the first end of the first winding of the first inductor is connected to the first input terminal, the second end of the first winding is connected to one end of the series resonant circuit, the other end of the series resonant circuit is connected to the second input terminal, and the first output terminal and the second output terminal are respectively connected to one end and the other end of the series resonant circuit, whereby the ripple current can be directly filtered out by the first inductor and the series resonant circuit, and the filter has higher ripple filtering efficiency than the filter provided in the secondary coil of the transformer, and the resonance frequency is not affected by the leakage of the inductance of the transformer, and the frequency notch point can be accurately controlled, thereby improving the reliability of ripple filtering.

In some embodiments, the series resonant circuit 303 comprises a second inductor Lrcf and a second capacitor Crcf connected in series, wherein the resonant frequency of the series resonant circuit 303 comprises the switching frequency of the input signal Vi. This can filter out the switching frequency component in the input signal Vi and eliminate the ripple current in the input signal Vi.

As shown in fig. 3, a part of the ripple component in the input signal Vi may be absorbed by the first inductor 307, and another part of the ripple component (e.g., a switching frequency component in the input signal Vi) may be filtered out by the series resonant circuit 303, so that the ripple current in the input signal Vi can be reliably eliminated.

For example, as shown in fig. 3, one end of the series resonant circuit 303 is connected to the second end of the first winding, and the other end is grounded. Thereby, the switching frequency component of the input signal Vi can be short-circuited.

In some embodiments, as shown in fig. 3, the filter 300 may also include a gain adjustment circuit 306. The gain adjustment circuit 306 includes a resistor R1 and a first capacitor C1 connected in series, and the gain adjustment circuit 306 is connected in parallel with the series resonant circuit 303. By providing this gain adjustment circuit 306, the gains of the output signal Vo and the input signal Vi can be adjusted with less loss. For example, by providing damping through the resistor R1 and the first capacitor C1, it is possible to avoid high gain at frequencies below the resonance frequency, and thus, it is possible to secure the use safety of the gradient coil.

Fig. 4 is a schematic diagram of the frequency response of the filter 300 of the embodiment of the present application, wherein the vertical axis represents the gain of the output signal Vo relative to the input signal Vi in dB; the horizontal axis represents frequency in KHz. As shown in fig. 4, the resonance frequency of the series resonant circuit 303 is set at the switching frequency 125KHz of the input signal Vi, and since the frequency component of 125KHz of the input signal Vi is short-circuited by the series resonant circuit 303, the gain of the output signal Vo at the switching frequency 125KHz is 0 or close to 0. Most of the high frequency component in the input signal Vi is absorbed by the first inductor 307, as shown in fig. 4, the output signal Vo has a lower gain at the high frequency component. For low frequency components of the input signal Vi that are lower than the switching frequency 125KHz, the damping provided by the resistor R1 and the first capacitor C1 can ensure that the peak gain of the output signal Vo at this low frequency component (e.g. 30 KHz) is less than 5dB.

Further, the filter 300 in the embodiment of the present application has a small loss on the resistor R1. For example, for the filter 300 of the present embodiment, the loss of resistor R1 is about 6W when the current of the gradient coil is 300A and the switching frequency is 125 KHz; the loss of resistor R1 is about 300W when the current of the gradient coil increases at a rate of 1A/us. In contrast, under the same conditions, the loss of the existing filter at the damping resistor is about 4 times the loss of the resistor R1.

In some embodiments, the first inductor 307 may be an inductor in various forms. For example, the first inductor 307 may include a core and a first winding wound on the core, i.e., the first inductor 307 may include one winding. The present application is not limited thereto and the first inductor 307 may also include other numbers of windings.

Fig. 5 is another schematic diagram of a filter 300 according to an embodiment of the present application. As shown in fig. 5, the first inductor 307 includes a first winding and a second winding. Wherein a first end a of the first winding is connected to the first input terminal 301 and a second end b of the first winding is connected to one end of the series resonant circuit 303; the first end c of the second winding is connected to the second input terminal 302, and the second end d of the second winding is connected to the other end of the series resonant circuit 303. Thus, common mode disturbances and differential mode disturbances can be filtered out to avoid common mode and/or differential mode disturbances entering the gradient coil, thereby affecting the quality of the medical image.

Fig. 6 is a schematic diagram of a first inductor 307 according to an embodiment of the present application. In some embodiments, as shown in fig. 6, the core of the first inductor 307 comprises an EI core 60. Wherein the first winding 61 and the second winding 62 are located at both sides of the center post of the EI core 60, respectively.

In some embodiments, as shown in fig. 6, the EI core 60 includes a first EI core 601 and a second EI core 602. The first EI core 601 includes a first E core E1 and a first I core I1, and the first E core E1 includes a first base plate E11, a first center post E12 perpendicular to the first base plate E11, and two first side posts E13, E14 located at both sides of the first center post E12.

The second EI core 602 includes a second E core E2 and a second I core I2, the second E core E2 includes a second bottom plate E21, a second center post E22 perpendicular to the second bottom plate E21, and two second side posts E23, E24 located on both sides of the second center post E22, and the first bottom plate E11 abuts against the second bottom plate E21.

In some embodiments, the first winding 61 is wound around the first bottom plate E11 and the second bottom plate E21 via a first gap between the first center post E12 and one first side post E13, a second gap between the second center post E22 and one second side post E23; the second winding 62 winds E11 and the second base plate E21 via a third gap between the first center post E12 and the other first side post E14, and a fourth gap between the second center post E22 and the other second side post E24. This can increase the magnetic flux area and reduce the magnetic resistance, thereby improving the filtering effect of the differential mode and the common mode. Further, since the magnetic flux area increases, the number of turns of the winding can be reduced, thereby reducing the cost and contributing to miniaturization, and also, problems such as heat generation due to an excessively small wire area of the winding can be avoided.

In some embodiments, as shown in fig. 6, when differential mode current flows in the first winding 61 and the second winding 62 (e.g., current flows in from the first end a of the first winding 61, flows out from the second end b of the first winding 61, and flows in from the second end d of the second winding 62, flows out from the first end c of the second winding 62), a differential mode magnetic flux path is formed in the EI core 60 as shown by the arrowed dash-dot line, which is formed in the I core, the center leg of the E core, the bottom plate of the E core, and the side legs of the E core; when a common mode current flows in the first winding 61 and the second winding 62 (for example, a current flows in from the first end a of the first winding 61 and flows out from the second end b of the first winding 61, and a current flows in from the first end c of the second winding 62 and flows out from the second end d of the second winding 62), a common mode magnetic flux path shown by an arrow dotted line is formed in the EI core 60, and the common mode magnetic flux path is formed in the I core, the two side legs of the E core, and the bottom plate of the E core.

In some embodiments, as shown in fig. 6, a fifth gap may be formed between the first center leg E12 and the first I-core I1, and a sixth gap may be formed between the second center leg E22 and the second I-core I2. Thereby, at least one of the fifth gap and the sixth gap is made to have an air gap on the path of the differential mode magnetic flux, so that the differential mode magnetic flux can be prevented from being saturated at a high current (e.g., 300A), and thus it can be ensured that the differential mode interference at the high current can be reliably filtered out.

In some embodiments, as shown in fig. 6, two first side legs E13 and E14 may abut the first I-core I1; the two second jambs E23 and E24 may abut the second I-core I2. Thus, the common mode magnetic flux has a reduced air gap or no air gap in the path, so that the common mode inductance is large, and the sensitivity to common mode interference can be improved, so that even if the common mode interference is small, the common mode interference can be accurately filtered.

The above description has been made taking the case where the EI core 60 includes two EI type planar cores as an example. The present application is not limited thereto, and the EI core 60 may also include one EI type planar core, in which case the first winding 61 and the second winding 62 may be wound on the bottom plates of both sides of the center leg of the one EI type planar core or on the side legs of both sides of the center leg, respectively. Alternatively, the core of the first inductor 307 may be another type of core, for example, a U-shaped core, or the like.

Fig. 7 and 8 are schematic diagrams of a filter and gradient coil lumped model (lumped model) of an embodiment of the present application. As shown in fig. 7 and 8, a gradient coil lumped model (lumped model) 400' simulates the frequency characteristics of the gradient coil, for example, the gradient coil lumped model 400' may include parasitic capacitances Cs, resistances Rdc, R11 and R12, and inductances Ldc, L11 and L12 of the gradient coil, and in addition, a parasitic resistance Rs exists between the filter 300 and the gradient coil lumped model 400' as shown in fig. 7.

Fig. 7 and 8 exemplarily show specific values of the components in the filter 300, for example, the first inductor 307 may be set to 20uH, the second inductor Lrcf may be set to 7.3uH, the second capacitor Crcf may be set to 0.22uF, the resistor R1 may be set to 6Ω, and the first capacitor C1 may be set to 1uF. The present application is not limited thereto, and the components in the filter 300 may be other values.

Further, fig. 7 exemplarily shows specific values of the parasitic resistance Rs, for example, the parasitic resistance Rs is 1uΩ, fig. 7 and 8 exemplarily show specific values of the respective components in the gradient coil lumped model 400', for example, the parasitic capacitance Cs may be set to 50nF, the resistances Rdc, R11 and R12 may be set to 0.23 Ω, 75 Ω, 900 Ω, the inductances Ldc, L11 and L12 may be set to 1.2mH, 1.25mH, 4.5mH, respectively. The present application is not limited thereto, and the components in the gradient coil lumped model 400' may be other values.

According to the above embodiment, in the filter of the gradient amplifier, the first end of the first winding of the first inductor is connected to the first input terminal, the second end of the first winding is connected to one end of the series resonant circuit, the other end of the series resonant circuit is connected to the second input terminal, and the first output terminal and the second output terminal are respectively connected to one end and the other end of the series resonant circuit, whereby the ripple current can be directly filtered out by the first inductor and the series resonant circuit, and the filter has higher ripple filtering efficiency than the filter provided in the secondary coil of the transformer, and the resonance frequency is not affected by the leakage of the inductance of the transformer, and the frequency notch point can be accurately controlled, thereby improving the reliability of ripple filtering.

The embodiment of the application also provides a magnetic resonance imaging system. The magnetic resonance imaging system may correspond to the system shown in fig. 1 of an embodiment of the present application. The magnetic resonance imaging system comprises a gradient coil and a gradient amplifier outputting a drive signal to the gradient coil. For example, the gradient coils may be gradient coils disposed in the gradient coil assembly 142, and the gradient amplifiers may be any one or more of a Gx amplifier 151, a Gy amplifier 152, and a Gz amplifier 153. The gradient amplifier includes a filter corresponding to the filter described in the foregoing embodiment, and the specific implementation thereof may refer to the foregoing embodiment, and the content thereof is not described in detail.

The apparatus and method of the present application may be implemented by hardware, or may be implemented by hardware in combination with software. The present application relates to a computer readable program which, when executed by a logic means, enables the logic means to carry out the apparatus or constituent means described above, or enables the logic means to carry out the various methods or steps described above. The present application also relates to a storage medium such as a hard disk, a magnetic disk, an optical disk, a DVD, a flash memory, or the like for storing the above program.

The methods/apparatus described in connection with the embodiments of the present application may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. For example, one or more of the functional blocks shown in the figures and/or one or more combinations of the functional blocks may correspond to individual software modules or individual hardware modules of the computer program flow. These software modules may correspond to the individual steps shown in the figures, respectively. These hardware modules may be implemented, for example, by solidifying the software modules using a Field Programmable Gate Array (FPGA).

A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. A storage medium may be coupled to the processor such that the processor can read information from, and write information to, the storage medium; or the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The software modules may be stored in the memory of the mobile terminal or in a memory card that is insertable into the mobile terminal. For example, if the apparatus (e.g., mobile terminal) employs a MEGA-SIM card of a relatively large capacity or a flash memory device of a large capacity, the software module may be stored in the MEGA-SIM card or the flash memory device of a large capacity.

One or more of the functional blocks described in the figures and/or one or more combinations of functional blocks may be implemented as a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any suitable combination thereof for use in performing the functions described herein. One or more of the functional blocks described with respect to the figures and/or one or more combinations of functional blocks may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP communication, or any other such configuration.

The present application has been described in connection with specific embodiments, but it should be apparent to those skilled in the art that these descriptions are intended to be illustrative and not limiting. Various modifications and adaptations of the disclosure may occur to those skilled in the art and are within the scope of the disclosure.

Claims (10)

1. A filter for use in a gradient amplifier, the filter comprising:

a first input terminal and a second input terminal that receive an input signal;

a first inductor comprising a first winding, a first end of the first winding being connected to the first input terminal;

a series resonant circuit having one end connected to the second end of the first winding and the other end connected to the second input terminal; and

a first output terminal and a second output terminal, which supply a driving signal to the gradient coil, the first output terminal being connected to one end of the series resonant circuit, and the second output terminal being connected to the other end of the series resonant circuit.

2. The filter of claim 1, wherein the filter is configured to filter the filter,

the series resonant circuit includes a second inductor and a second capacitor connected in series, and a resonant frequency of the series resonant circuit includes a switching frequency of the input signal.

3. The filter of claim 1, wherein the filter further comprises:

a gain adjustment circuit comprising a resistor and a first capacitor connected in series is connected in parallel with the series resonant circuit.

4. The filter of claim 1, wherein the filter is configured to filter the filter,

the first inductor further includes a second winding, a first end of the second winding is connected to the second input terminal, and a second end of the second winding is connected to the other end of the series resonant circuit.

5. The filter of claim 4, wherein the filter is configured to filter the filter,

the iron core of the first inductor comprises an EI iron core, and the first winding and the second winding are respectively positioned on two sides of a center column of the EI iron core.

6. The filter of claim 5, wherein the EI core comprises:

the first EI iron core comprises a first E iron core and a first I iron core, wherein the first E iron core comprises a first bottom plate, a first central column perpendicular to the first bottom plate and two first side columns positioned on two sides of the first central column;

the second EI iron core comprises a second E iron core and a second I iron core, the second E iron core comprises a second bottom plate, a second center column perpendicular to the second bottom plate and two second side columns located on two sides of the second center column, and the first bottom plate is in butt joint with the second bottom plate.

7. The filter of claim 6, wherein the filter is configured to filter the filter,

the first winding winds the first base plate and the second base plate via a first gap between the first center post and one of the first side posts, a second gap between the second center post and one of the second side posts;

the second winding is wound around the first base plate and the second base plate via a third gap between the first center post and the other of the first side posts, and a fourth gap between the second center post and the other of the second side posts.

8. The filter of claim 6, wherein the filter is configured to filter the filter,

a fifth gap is formed between the first center post and the first I iron core; and/or

And a sixth gap is formed between the second center post and the second I iron core.

9. The filter of claim 6, wherein the filter is configured to filter the filter,

the two first side posts are abutted with the first I iron core; and/or

And the two second side posts are abutted with the second I iron core.

10. A magnetic resonance imaging system, characterized in that the magnetic resonance imaging system comprises:

a gradient coil; and

a gradient amplifier outputting a drive signal to the gradient coil, the gradient amplifier comprising the filter of any one of claims 1-9.