CN106374867B - Trap and magnetic resonance imaging apparatus equipped with the same - Google Patents
Trap and magnetic resonance imaging apparatus equipped with the same Download PDFInfo
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- CN106374867B CN106374867B CN201510443621.1A CN201510443621A CN106374867B CN 106374867 B CN106374867 B CN 106374867B CN 201510443621 A CN201510443621 A CN 201510443621A CN 106374867 B CN106374867 B CN 106374867B
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Abstract
The invention provides a wave trap for magnetic resonance imaging equipment, which comprises a shell and a cavity which is positioned in the shell and used for accommodating a radio frequency cable, wherein an adjustable capacitor element and a conductive body are arranged on the shell, the adjustable capacitor element is connected with the conductive body to form a radio frequency resonance circuit, the adjustable capacitor element comprises a first electrode plate and a second electrode plate which are arranged on the shell and are oppositely arranged at intervals, and the second electrode plate can rotate or translate relative to the shell. The trap filter provided by the invention has the advantage that the trap filter can achieve a good inhibition effect at the working frequency point of nuclear magnetic work by using the adjustable capacitor element and the fixed capacitor element simultaneously. The adjustable capacitor element realizes the adjustment of the capacitance value by moving at least one of the first electrode plate and the second electrode plate, and has simple structure and convenient adjustment operation.
Description
Technical Field
The invention relates to the technical field of magnetic resonance imaging, in particular to a wave trap for a magnetic resonance imaging device.
Background
In magnetic resonance imaging apparatuses, in order to obtain the best possible signal-to-noise ratio, the local coil is usually positioned as close as possible to the body of the subject or patient. For further transmission of the magnetic resonance signals from the local coil to the signal processing system, shielded coaxial cables are usually employed. The local coil is connected to a first coaxial cable that is plugged into the examination table. A further coaxial cable is connected to the connector of the examination table, which leads the magnetic resonance signals out of the examination table and onward to a signal processing system.
Due to the electric field and the magnetic field formed at the transmission stage of the high-frequency pulse, a high-frequency current is induced on the wire cover (outer conductor) of the coaxial cable. Without appropriate suppression measures, image disturbances can result and in the worst case, risks to the patient.
In order to suppress the generation of high-frequency currents, wave traps integrated in the patient bed are used. The main functions of the wave trap are to suppress common-mode signals on the radio frequency cable and to suppress the burning of the patient caused by large current. The wave trap generates a suppression signal at the working frequency point of nuclear magnetic resonance according to the principle that resonance is generated by capacitance and inductance. In order to meet the working frequency point of nuclear magnetism work, corresponding inductance and capacitance values need to be calculated; the calculated capacitance or inductance values are difficult to match perfectly in practice. This requires that the capacitance or inductance be adjustable.
Disclosure of Invention
The invention aims to provide a wave trap convenient for adjusting capacitance value and a magnetic resonance imaging device with the wave trap.
According to the wave trap of the invention, the wave trap comprises a shell and a cavity which is positioned in the shell and is used for accommodating a radio frequency cable, an adjustable capacitance element and a conductive body are arranged on the shell, the adjustable capacitance element is connected with the conductive body to form a radio frequency resonance circuit, the adjustable capacitance element comprises a first electrode plate and a second electrode plate which are arranged on the shell and are oppositely arranged at intervals, and the second electrode plate can rotate or translate relative to the shell.
Further, the first electrode plate and the second electrode plate are metal plates or insulating matrix structures with metallization layers.
Further, the shape of the metal plate or the metallization layer is crescent, rectangular, triangular or trapezoidal.
Furthermore, a counter bore is formed in the shell, the counter bore is located below the first electrode plate, and the second electrode plate is arranged in the counter bore.
Furthermore, the first electrode plate is provided with an opening, and the second electrode plate is positioned below the opening.
Furthermore, a plurality of openings are formed in the first electrode plate, and each opening and one second electrode plate are arranged at intervals relatively.
Furthermore, an adjusting structure is arranged on the second electrode plate.
Further, the wave trap further comprises a fixed capacitive element connected in parallel with the adjustable capacitive element.
The invention also provides a magnetic resonance imaging device, which comprises a magnet, a radio frequency receiving coil, a radio frequency signal processing device and a radio frequency cable for connecting the radio frequency receiving coil and the radio frequency signal processing device, and is characterized in that at least one wave trap is configured in the extension direction of the radio frequency cable, the wave trap comprises a shell and a cavity positioned in the shell, the cable passes through the cavity of the shell, an adjustable capacitor element and a fixed capacitor element are arranged on the shell, the adjustable capacitor element and the fixed capacitor element are electrically connected to form a radio frequency resonance circuit, the adjustable capacitor element comprises a first electrode plate and a second electrode plate which are arranged on the shell and are arranged at intervals, and the second electrode plate can rotate or translate relative to the shell.
Further, the surface of the housing is a metallization layer structure, and the first electrode plate, the metallization layer structure and the fixed capacitor element are electrically connected.
The trap filter provided by the invention has the advantage that the trap filter can achieve a good inhibition effect at the working frequency point of nuclear magnetic work by using the adjustable capacitor element and the fixed capacitor element simultaneously. The adjustable capacitor element realizes the adjustment of the capacitance value by moving at least one of the first electrode plate and the second electrode plate, and has simple structure and convenient adjustment operation.
Drawings
Figure 1 is a diagram of a prior art parallel resonant circuit for a wave trap on a cable;
figure 2 is a schematic diagram of the structure of a wave trap according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a housing with a metallization layer according to an embodiment of the invention;
figure 4 is an exploded view of the wave trap shown in figure 2;
Detailed Description
The following detailed description of the embodiments of the present invention will be made with reference to the drawings and examples, but the scope of the present invention should not be limited thereto.
In order to suppress common-mode signals occurring on the radio-frequency cable and to suppress the generation of high currents, a wave trap integrated in the patient bed is used, which exhibits a high-ohmic impedance Z0 for high-frequency currents, which high-ohmic impedance Z0 can be realized, for example, by means of a parallel resonant circuit. A plurality of coaxial cables are wound into a coil and a conductor shield is connected at one end of the coil thus produced to a capacitor connected in parallel to the coil. Such a wave trap is necessary in all lines leading through the transmitting antenna. Fig. 1 shows a wave trap 100 in which a coaxial cable 200 having a wire jacket surrounding a plurality of inner conductors is wound into a coil, the coil 200 being connected at both ends thereof to terminals of a capacitor 300, the resonance of the parallel circuit thus formed being adjustable by means of the capacitor 300. The inner conductor is insulated from the wire cover in the usual manner.
Referring to fig. 2, the wave trap 100 includes a housing 101 and a cavity 102 in the housing 101 for accommodating a radio frequency cable 200. The housing 101 acts as a mechanical carrier for the electrical components arranged thereon or therein. The housing 101 is for example at least partly made of plastic, but the plastic has corresponding features that make it possible to use it in a magnetic field environment. In such a plastic-based housing 101, a metallization layer may be injected, for example, on or below its surface. If the outer surface of the metallization layer located thereunder is realized by plastic, it has an insulating and protective effect of the plastic in addition to a mechanical stabilizing effect.
The housing 101 is composed of two upper and lower housings 1011 and 1012 which can be separated from each other. The upper housing 1011 and the lower housing 1012 may be locked, for example, by screws or structural designs, and the cable 200 located in the cavity 102 is clamped and compressed. In another embodiment of the present invention, the housing 101 is a unitary structure, and the cable 200 is led into or out of the cavity 102 of the housing.
The inside of the housing 101 forms a spatially confined cavity 102, the cross-section or the shape of the cross-section and the inner diameter of the cavity 102 being set as desired. The cross-section or the shape of the cross-section of the cavity 102 may be arranged to be circular or nearly circular, whereby a higher trap quality is obtained, since the magnetic losses occurring in the magnetic circuit are relatively small in this shape, but also an elliptical or other shape may be used. The cavity 102, when sized to have a corresponding inner diameter, may accommodate only one cable or a plurality of cables. The cable 103 is, for example, a radio frequency assembly cable having an inner conductor composed of a radio frequency line for transmitting a magnetic resonance signal and a dc power line, and a wire cover having a shielding function for the inner conductor. The shielding effect is achieved by a wire mesh surrounding an inner conductor, which is insulated with respect to an outer conductor.
Referring to fig. 3, the housing 101 is further provided with a conductive body 103 on a surface thereof outside the cavity 102, and the conductive body 103 is, for example, a metallization layer (metal layer) which allows current to pass through. And the metallization layer is interrupted by at least one first gap, the first gap thus formed being bridged by at least one capacitive element 300, the metallization layers adjacent to the first gap being in contact with the contacts of the capacitive element 300, respectively. The formation of a parallel resonant circuit together with the capacitive element is achieved by means of a metallized surface of the housing 101 and the parallel resonator circuit is tuned to the desired resonance frequency. Tuning the parallel resonator circuit to a desired resonant frequency requires calculation of corresponding inductance and capacitance values, and the calculated capacitance or inductance values are difficult to match completely in practice, which requires that the capacitance or inductance values be variable.
Referring to fig. 4, the tunable capacitor element 303 is, for example, a plate capacitor, and is formed by a first electrode plate and a second electrode plate that are disposed at an interval, for example, a first circuit board 3031 and a second circuit board 3032 having a metalized layer, and the metalized layer on the first circuit board 3031 is disconnected by at least one second gap. The metal layer may be copper, silver, zinc or other metals. The metallization layers of the first and second circuit boards 3031 and 3032 are, for example, crescent-shaped, but may also take the form of rectangles, trapezoids, triangles, or other shapes. The opposing areas of the metallization layers on the first circuit board 3031 and the second circuit board 3032 form the electrode areas of the tunable capacitive element 303. In another embodiment of the present invention, the first electrode plate 3031 and the second electrode plate 3032 of the adjustable capacitive element 303 directly use metal plates.
According to the capacitance formula C ═ S/4 pi kd, C is a capacitance value and is a dielectric constant, k is an electrostatic force constant, S is an electrode area, and d is a distance between two plates, and under the condition that other parameters are not changed, the capacitance value can be changed by changing the opposite area of the two electrode plates of the capacitance element. According to this principle, the adjustable capacitive element 303 is configured to change the capacitance value of the adjustable capacitive element 303 by moving at least one of the first circuit board 3031 and the second circuit board 3032 to change the facing area of the two electrode plates of the adjustable capacitive element 303.
The variable capacitive element 303 is disposed on one side surface of the housing 101, and the first circuit board 3031 and the second circuit board 3032 of the variable capacitive element 303 are connected to the housing 101, respectively. The first circuit board 303 is fixedly connected to the housing 101, and two ends of the first circuit board 3031 are electrically connected to the metallization structure on the housing 101. The second circuit board 3032 is, for example, movably connected to the housing 101, and the second circuit board 3032 is not electrically connected to the metallization structure of the housing 101. The second circuit board 3032 may translate or rotate relative to the housing 101 and the first circuit board 3031. When the second circuit board 3032 translates or rotates relative to the first circuit board 3031, the relative area between the metalized layer on the first circuit board 3031 and the metalized layer on the second circuit board 3032 changes, thereby changing the capacitance value of the adjustable capacitive element 303.
In another embodiment of the present invention, the first circuit board 3031 is movably connected to the housing 101, and the second circuit board 3032 is fixedly connected to the housing 101, so that when the first circuit board 3031 translates or rotates relative to the second circuit board 3032, the capacitance of the adjustable capacitive element 303 changes.
The housing 101 has a counterbore 104 for accommodating the second circuit board 3032, for example, and the second circuit board 3032 in the counterbore 104 is movably connected with the housing 101. The cross-section or the shape of the cross-section of the counterbore 104 may be configured as desired, for example, may be configured to be the same as the shape of the second circuit board 3032, but may be configured in other shapes. The depth of the counterbore 104 may be set to be comparable to the second circuit board 3032, for example. The counterbore 104 is shaped and sized to permit translation or rotation of the second circuit board 3032 relative to the housing 101 and the first circuit board 3031 when the second circuit board 3032 is positioned within the counterbore 104.
The first circuit board 3032 has, for example, an opening 105, the opening 105 is disposed opposite to the second circuit board 3031, and the cross section or the cross-sectional shape of the opening 105 may be set as desired, for example, may be set to be circular or nearly circular, but may also be set to be rectangular, oval or other shapes. The opening 105 is shaped and sized to have an inner diameter such that the relative area of the metalized layer on the first circuit board 3031 and the metalized layer on the second circuit board 3032 changes as the second circuit board 3032 translates or rotates relative to the first circuit board 3031.
As shown in fig. 4, the tunable capacitance element 303 is formed of a first circuit board 3031 and a second circuit board 3032 which are arranged at an interval in opposition to each other. The first circuit board 3031 is rectangular in shape and is fixedly connected to the housing 101. A metallization layer is applied to a surface of the first circuit board 3031 opposite the second circuit board 3032, and both ends of the metallization layer are electrically connected to the metallization structure on the housing 101. And the metallization layer is interrupted by a second gap. The first circuit board 3031 is also provided with a circular opening 105.
The second circuit board 3032 is movably connected to the housing 101 below the opening 105 of the first circuit board 3031. The second circuit board 3032 is visible through the opening 105 and is translated or rotated with respect to the second circuit board 3032. The second circuit board 3032 is provided in a circular shape, and the diameter of the second circuit board 3032 is larger than the inner diameter of the opening 105; a crescent-shaped metallization layer is coated on one surface of the second circuit board 3032 opposite to the first circuit board 3031. By rotating the second circuit board 3032, the facing area of the metallization layer on the first circuit board 3031 and the crescent-shaped metallization layer on the second circuit board 3032 can be adjusted, so as to adjust the capacitance value of the adjustable capacitive element 303.
The surface of the housing 101 is also provided with a counterbore 104 for receiving the second circuit board 3032. The counterbore 104 is circular in cross section, has an inner diameter slightly larger than the diameter of the second circuit board 3032, and has a depth set to be equivalent to that of the second circuit board 3032. In order to facilitate adjustment of the second circuit board 3032, the second circuit board 3032 is further provided with an adjustment structure, which may be provided as an adjustment hole, for example, but may also be provided in other adjustment manners.
In other embodiments of the present invention, the tunable capacitive element 303 is formed by a first circuit board 3031 and a plurality of second circuit boards 3032 spaced apart from each other, the first circuit board 3031 being interrupted by a plurality of second gaps, and a second circuit board 3032 spaced apart from each other below each of the second gaps. The plurality of second circuit boards 3032 are movably connected with the housing 101, and the capacitance value of the adjustable capacitance element 303 is adjusted by translating or rotating at least one second circuit board 3032.
The wave trap 100 according to the invention can be completely or partially fixed on or in the patient bed in the magnetic resonance imaging system. For a radio frequency cable located in a bed, a plurality of wave traps 100 are arranged on the radio frequency cable. The cumulative length of the plurality of traps 100 is at least as long as the geometric length of the radio frequency cable. Thereby ensuring suppression of common mode signals generated on the radio frequency cable and suppression of burning of the patient by the generated large current.
In summary, according to the trap filter of the present invention, the adjustable capacitor and the fixed capacitor are used simultaneously, so that the trap filter achieves a good suppression effect at the working frequency point of nuclear magnetic work.
Although the present invention has been described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (7)
1. A wave trap for a magnetic resonance imaging device comprises a shell and a cavity which is positioned in the shell and used for accommodating a radio frequency cable, and is characterized in that an adjustable capacitance element and a conductive body are arranged on the shell, the adjustable capacitance element and the conductive body are connected to form a radio frequency resonance circuit, the adjustable capacitance element comprises a first electrode plate and a second electrode plate which are arranged on the shell and are arranged at intervals, and the second electrode plate can move horizontally relative to the shell;
the conductor is arranged on the side surface of the shell, and the first electrode plate and the second electrode plate are arranged on the top surface of the shell;
the first electrode plate is in a rectangular shape extending along the length direction of the radio frequency cable, the first electrode plate is fixedly connected with the shell, a metalized layer along the length direction of the radio frequency cable is arranged on the first electrode plate, and two ends of the metalized layer are electrically connected with the electric conductors on the shell;
the first electrode plate is provided with an opening at the discontinuous part of the metallization layer, and the second electrode plate is positioned below the opening.
2. The wave trap of claim 1, wherein the second electrode plate is a metal plate or an insulating matrix structure with a metalized layer.
3. The wave trap of claim 2, wherein the shape of the metal plate or the metallization layer on the second electrode plate is crescent, rectangular, triangular or trapezoidal.
4. The wave trap of claim 1, wherein the housing has a counterbore below the first electrode plate, and the second electrode plate is disposed in the counterbore.
5. The wave trap device of claim 1, wherein the second electrode plate is provided with an adjustment structure.
6. The wave trap of claim 1, further comprising a fixed capacitive element in parallel with the tunable capacitive element.
7. A magnetic resonance imaging device comprises a magnet, a radio frequency receiving coil, a radio frequency signal processing device and a radio frequency cable for connecting the radio frequency receiving coil and the radio frequency signal processing device, and is characterized in that at least one wave trap is configured in the extension direction of the radio frequency cable, the wave trap comprises a shell and a cavity positioned in the shell, the cable passes through the cavity of the shell, an adjustable capacitor element and a fixed capacitor element are arranged on the shell, the adjustable capacitor element and the fixed capacitor element are electrically connected to form a radio frequency resonance circuit, the adjustable capacitor element comprises a first electrode plate and a second electrode plate which are arranged on the shell and are arranged at intervals, and the second electrode plate can translate relative to the shell;
the side surface of the shell is provided with a conductor, and the first electrode plate and the second electrode plate are arranged on the top surface of the shell;
the first electrode plate is in a rectangular shape extending along the length direction of the radio frequency cable, the first electrode plate is fixedly connected with the shell, a metalized layer along the length direction of the radio frequency cable is arranged on the first electrode plate, and two ends of the metalized layer are electrically connected with the electric conductors on the shell;
and the first electrode plate is also provided with an opening at the discontinuous part of the metallization layer, and the second electrode plate is positioned below the opening.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510443621.1A CN106374867B (en) | 2015-07-24 | 2015-07-24 | Trap and magnetic resonance imaging apparatus equipped with the same |
| PCT/CN2015/094461 WO2016074636A1 (en) | 2014-11-12 | 2015-11-12 | Transport apparatus in medical system |
| US15/317,539 US10548532B2 (en) | 2014-11-12 | 2015-11-12 | Transport apparatus in medical system |
| US16/662,298 US11553882B2 (en) | 2014-11-12 | 2019-10-24 | Transport apparatus in medical system |
| US18/155,046 US20230172554A1 (en) | 2014-11-12 | 2023-01-16 | Transport apparatus in medical system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510443621.1A CN106374867B (en) | 2015-07-24 | 2015-07-24 | Trap and magnetic resonance imaging apparatus equipped with the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN106374867A CN106374867A (en) | 2017-02-01 |
| CN106374867B true CN106374867B (en) | 2020-12-01 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201510443621.1A Active CN106374867B (en) | 2014-11-12 | 2015-07-24 | Trap and magnetic resonance imaging apparatus equipped with the same |
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| Country | Link |
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| CN (1) | CN106374867B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109490803B (en) * | 2018-10-16 | 2020-06-05 | 清华大学 | Super-structure surface device, preparation method and nuclear magnetic resonance imaging system |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2185627A (en) * | 1986-01-16 | 1987-07-22 | Alps Electric Co Ltd | Miniature variable capacitor |
| US5602516A (en) * | 1995-10-16 | 1997-02-11 | Parfitt; Dale R. | Asymmetrical notch filter |
| CN102890253A (en) * | 2011-07-21 | 2013-01-23 | 西门子公司 | Standing wave trap integrated in local coil |
| CN101750594B (en) * | 2008-12-17 | 2015-07-01 | 西门子公司 | Standing wave barrier for a magnetic resonance tomography device |
-
2015
- 2015-07-24 CN CN201510443621.1A patent/CN106374867B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2185627A (en) * | 1986-01-16 | 1987-07-22 | Alps Electric Co Ltd | Miniature variable capacitor |
| US5602516A (en) * | 1995-10-16 | 1997-02-11 | Parfitt; Dale R. | Asymmetrical notch filter |
| CN101750594B (en) * | 2008-12-17 | 2015-07-01 | 西门子公司 | Standing wave barrier for a magnetic resonance tomography device |
| CN102890253A (en) * | 2011-07-21 | 2013-01-23 | 西门子公司 | Standing wave trap integrated in local coil |
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| CN106374867A (en) | 2017-02-01 |
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Address after: 201807 Shanghai city Jiading District Industrial Zone Jiading Road No. 2258 Applicant after: Shanghai Lianying Medical Technology Co., Ltd Address before: 201807 Shanghai city Jiading District Industrial Zone Jiading Road No. 2258 Applicant before: SHANGHAI UNITED IMAGING HEALTHCARE Co.,Ltd. |
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