JP2002085373A - Method for inhibiting electromagnetic coupling between coils, orthogonal coil, mri device and method of making orthogonal coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit electromagnetic coupling between coils by use of a simple arrangement. SOLUTION: Copper foil 2 for inhibiting the electromagnetic coupling between a first coil 110 and a second coil 120 arranged so that the times formed by the coils are orthogonal to each other is affixed near a portion where the conductors of the first coil 110 and the second coil 120 cross each other near the centers of the coil surfaces. Thus, SN ratios can be enhanced and reliability enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for suppressing electromagnetic coupling between coils, a quadrature coil, and an MRI (Magnetic Resonance I).
More specifically, the present invention relates to a method for suppressing electromagnetic coupling between coils that can suppress electromagnetic coupling between coils with a simple configuration, a quadrature coil, an MRI apparatus, and a method for manufacturing a quadrature coil.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a conventional orthogonal coil. The orthogonal coil 500 includes a first coil 110, a second coil 120, and a resonance circuit 53 for suppressing electromagnetic coupling between the coils. FIG.
Is drawn with the positions of the first coil 110 and the second coil 120 shifted for easier understanding.

[0003] As shown in FIG.
When power is supplied from the first coil conductor 111, a current flows in a figure eight shape. Thus, a magnetic field H1 parallel to the coil surface in a direction perpendicular to the current I1 traversing the center of the coil.
Is formed in a space slightly away from the center of the coil surface. The second coil 120 has the same structure as the first coil 110, but differs from the first coil 110 in a 90 ° direction.

[0004] The orthogonal coil 500 is referred to as an "orthogonal coil". When a magnetic field is formed in each of the first coil 110 and the second coil 120, a target area of the coil 500 (a certain object and the coil 500 are separated). This is because the magnetic fields respectively formed in the first coil 110 and the second coil 120 are orthogonal to each other in a space slightly away from the center of the coil surface, which is a region that is to act on each other electromagnetically.

A conventional technique of connecting a resonance circuit between coils to suppress electromagnetic coupling between the coils is disclosed in Japanese Patent Laid-Open No.
This is disclosed in JP-A-00-166894.

[0006]

A conventional orthogonal coil 50
At 0, the resonance circuit 53 is connected between the coils in order to suppress the electromagnetic coupling between the coils. However, since such a resonance circuit 53 is connected between portions where the potential difference between the coils is high, a circuit element having a large withstand voltage (such as a capacitor or an inductance) is required, or the circuit element is arranged in consideration of heat radiation. And the configuration becomes complicated. Therefore, an object of the present invention is to provide a method of suppressing electromagnetic coupling between coils, a quadrature coil, an MRI apparatus, and a method of manufacturing a quadrature coil that can suppress electromagnetic coupling between coils with a simple configuration.

[0007]

According to a first aspect of the present invention, a planar conductor is disposed near a plurality of coils arranged in close proximity to each other while being electrically insulated from the coils. Provided is a method of suppressing electromagnetic coupling between coils, characterized by suppressing electromagnetic coupling between coils. In the method for suppressing electromagnetic coupling between coils according to the first aspect, the magnetic flux for electromagnetically coupling the coils is suppressed by the induced current flowing through the planar conductor, so that the electromagnetic coupling between the coils is suppressed. And
Since there is no need to select a circuit element having a large withstand voltage (such as a capacitor or an inductance) or to dispose the circuit element in consideration of heat radiation, the configuration can be simplified. If the shapes and arrangement of the plurality of coils are determined, the shape and arrangement of the planar conductor that can sufficiently reduce the inter-coil interference can be determined by trial and error while measuring the inter-coil interference. If the shape and arrangement of the plurality of coils are the same, the shape and arrangement of the planar conductor may be the same.

[0008] In a second aspect, the present invention relates to a method of manufacturing a magnetic head, comprising: A method for suppressing electromagnetic coupling between coils, wherein a planar conductor is disposed in an insulated state to suppress electromagnetic coupling between coils. In the method for suppressing inter-coil electromagnetic coupling according to the second aspect, the planar conductor is disposed in the vicinity of the portion where the conductors of the plurality of coils intersect. Electromagnetic coupling between the coils can be suppressed.

[0009] In a third aspect, the present invention provides a plurality of coils arranged so that magnetic fields formed respectively are orthogonal to each other in a target area, and a plurality of coils arranged in the vicinity of the coils while being electrically insulated from the coils. And a planar conductor provided to suppress electromagnetic coupling between the coils. In the above configuration, the “magnetic field formed respectively” means a magnetic field formed by each coil in the case of a transmission coil, and a magnetic field formed by each coil when power is supplied to each coil in the case of a reception coil. means. Also,
The “target area” refers to a space area in which electromagnetic action is desired between a target and a coil in the area. In the orthogonal coil according to the third aspect, the magnetic flux for electromagnetically coupling the coils is suppressed by the induced current flowing through the planar conductor, so that the electromagnetic coupling between the coils is suppressed. And, the circuit element with large withstand voltage (capacitor,
It is not necessary to select an inductance or the like or to dispose circuit elements in consideration of heat radiation, so that the configuration can be simplified. If the shapes and arrangement of the plurality of coils are determined, the shape and arrangement of the planar conductor that can sufficiently reduce the inter-coil interference can be determined by trial and error while measuring the inter-coil interference. If the shape and arrangement of the plurality of coils are the same, the shape and arrangement of the planar conductor may be the same.

[0010] In a fourth aspect, the present invention provides an MRI apparatus comprising the quadrature coil configured as described above. In the MRI apparatus according to the fourth aspect, the second
, The electromagnetic coupling between the coils is suppressed, and the S / N ratio can be improved. Also, there is no need for a resonance circuit to suppress electromagnetic coupling between the coils,
Since the configuration can be simplified, and there is no failure or heat generation of the resonance circuit, reliability can be improved.

According to a fifth aspect, the present invention provides an M
In the RI apparatus, a planar conductor is provided near a portion where conductors of a plurality of coils intersect.
An I device is provided. In the MRI apparatus according to the fifth aspect, the planar conductor is disposed in the vicinity of the portion where the conductors of the plurality of coils intersect. Binding can be suppressed.

According to a sixth aspect of the present invention, a plurality of coils are arranged so that the magnetic fields formed respectively are orthogonal to each other in a target area, and the vicinity of a portion where conductors of the plurality of coils intersect is provided. And providing a planar conductor at a position where electromagnetic coupling between the coils can be suppressed and in a state electrically insulated from the coils. According to the method for manufacturing a quadrature coil according to the sixth aspect, the quadrature coil having the above configuration can be suitably manufactured.

According to a seventh aspect of the present invention, there is provided a method for manufacturing a quadrature coil having the above-described configuration, in which a planar conductor is arranged on a trial and error basis for an orthogonal coil having a structure in which the position at which the planar conductor is to be disposed is unknown. For the orthogonal coil of the same structure to be manufactured thereafter, the planar conductor is arranged at the position based on the determined position, and the planar conductor is added or removed by trial and error to reduce the variation in the structure. Provided is a method for manufacturing a quadrature coil, which performs a corresponding adjustment. According to the method of manufacturing the orthogonal coil according to the seventh aspect, the orthogonal coil having the above configuration can be efficiently manufactured.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited by this.

FIG. 1 shows an MRI according to an embodiment of the present invention.
It is a block diagram of an apparatus. In the MRI apparatus 1000, the magnet assembly 10 has a space (hole) for inserting a subject therein, and a static magnetic field for applying a constant static magnetic field to the subject so as to surround the space. A coil 10p, a gradient magnetic field coil 10g for generating a gradient magnetic field of a slice axis, a lead axis, and a phase axis, a transmission coil 100t for applying an RF pulse for exciting spins of nuclei in the subject, and And a receiving coil 100r for detecting the NMR signal of the above. The static magnetic field coil 10p is connected to a static magnetic field power supply 32. The gradient magnetic field coil 10g is connected to a gradient magnetic field drive circuit 23. The transmission coil 100t has an R
F power amplifier 24. The receiving coil 1
00r is connected to the preamplifier 25. Note that a permanent magnet may be used instead of the static magnetic field coil 10p.

The sequence storage circuit 26 operates the gradient magnetic field drive circuit 23 based on the stored pulse sequence in accordance with a command from the computer 27 to generate a gradient magnetic field from the gradient magnetic field coil 10 g of the magnet assembly 10. By operating the gate modulation circuit 28, the carrier wave output signal of the RF oscillation circuit 29 is modulated into a pulse signal having a predetermined timing and a predetermined envelope shape, and the resulting signal is applied to the RF power amplifier 24 as an RF pulse. After the power is amplified, it is applied to the transmission coil 100t of the magnet assembly 10 to selectively excite a desired slice area. The preamplifier 25 includes the magnet assembly 1
NM from the subject detected by the 0 receiving coil 100r
The R signal is amplified and input to the phase detector 30. The phase detector 30 uses the carrier output signal of the RF oscillation circuit 29 as a reference signal, performs phase detection of the NMR signal from the preamplifier 25, and provides the NMR signal to the A / D converter 31. The A / D converter 31
The analog signal after the phase detection is converted into a digital signal and input to the computer 27. The computer 27 reads data from the A / D converter 31 and performs an image reconstruction operation.
Generate an image of a desired slice area. This image is displayed on the display device 33. The computer 27
Is responsible for overall control such as receiving information input from the operation console 32. In addition, the MRI apparatus 1000 is an interventional (interventional)
It may be an open type MRI apparatus used for MRI.

FIG. 2 is a plan view of the orthogonal coil 100 used for at least one of the transmission coil 100t and the reception coil 100r.

Next, with reference to FIGS. 3 to 6, a procedure for forming the orthogonal coil 100 will be described. First, as shown in FIG. 3, a substrate 1 is prepared. This substrate 1 has, for example, a diameter of 8
0cm, 6mm thick fiber reinforced plastic (FRP)
It is made.

Next, as shown in FIG. 4, a copper foil tape having an adhesive material and a width of 1/2 inch and a thickness of 35 μm is attached to the substrate 1 with a predetermined pattern to form the first coil 110. A polyimide film is attached to the surface of the copper foil tape for insulation. Further, a circuit element E such as a capacitor is connected.

Next, as shown in FIG.
The second coil 120 having the same structure as that of the first coil 110 is formed on the substrate 1 in a direction different from the first coil 110 by 90 °. Also, the first coil conductor 111 and the second coil conductor 121 are connected.

Next, as shown in FIG. 6, a copper foil for suppressing electromagnetic coupling between the coils is provided near the center of the coil surface and near the intersection of the conductors of the first coil 110 and the second coil 120. 2 are attached with a space therebetween to form a quadrature coil 100 ′. Instead of copper foil 2, copper tape,
Aluminum tape or aluminum foil may be used.

The first coil 110 and the second coil 12
If the shape and arrangement of 0 are determined, the shape and arrangement of the copper foil 2 that can sufficiently reduce the interference between the coils can be determined by trial and error while measuring the interference between the coils. If the shape and arrangement of the first coil 110 and the second coil 120 are the same, the shape and arrangement of the planar conductor may be the same.

However, the first coil 110 and the second coil 12
The shape and arrangement of the copper foil 2 determined by trial and error are not always optimal because the shape and arrangement of 0 vary. Therefore, as shown in FIG. 2, fine adjustment is performed by adding a copper foil 2 ′ to a space between the copper foils 2 to obtain a final orthogonal coil 100.

[0024]

According to the method for suppressing the electromagnetic coupling between the coils, the orthogonal coil, the MRI apparatus and the method for manufacturing the orthogonal coil of the present invention, it is possible to suppress the electromagnetic coupling between the coils with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an MRI apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of a quadrature coil (after fine adjustment) according to an embodiment of the present invention.

FIG. 3 is a plan view of a substrate.

FIG. 4 is a plan view showing a state where a first coil is formed on a substrate.

FIG. 5 is a plan view showing a state where a first coil and a second coil are formed on a substrate.

FIG. 6 is a plan view of a quadrature coil (before fine adjustment) according to an embodiment of the present invention.

FIG. 7 is a plan view showing an example of a conventional orthogonal coil.

FIG. 8 is a plan view of a first coil.

[Explanation of symbols]

 Reference Signs List 1 substrate 2, 2 'copper foil 100 orthogonal coil (after fine adjustment) 100' orthogonal coil (before fine adjustment) 110 first coil 120 second coil 100t transmitting coil 100r receiving coil 1000 MRI apparatus

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takeshi Sato 4-7, Asahigaoka, Hino-shi, Tokyo 127 GE Yokogawa Medical Systems Co., Ltd. F-term (reference) 4C096 AA01 AB07 AB34 AD10 CC01 CC16 5E062 EE02 EE05

Claims (7)

[Claims] 1. A coil characterized in that a planar conductor is disposed in the vicinity of a plurality of coils disposed close to each other while being electrically insulated from the coils, thereby suppressing electromagnetic coupling between the coils. Method for suppressing electromagnetic coupling between the two. 2. A planar conductor near a portion where conductors of a plurality of coils arranged so that magnetic fields respectively formed are orthogonal to each other in a target region intersect with the coils and electrically insulated from the coils. And a method for suppressing electromagnetic coupling between coils, comprising: 3. A plurality of coils arranged so that magnetic fields formed respectively are orthogonal to each other in a target area, and electromagnetic coupling between the coils provided near the coils in a state of being electrically insulated from the coils. A quadrature coil, comprising: a planar conductor to be suppressed. 4. An MRI apparatus comprising the orthogonal coil according to claim 3. 5. The MRI apparatus according to claim 4, wherein
An MRI apparatus, wherein a planar conductor is provided near a portion where conductors of a plurality of coils intersect. 6. A plurality of coils are disposed so that magnetic fields formed respectively are orthogonal to each other in a target area, and electromagnetic coupling between the coils is provided near a portion where conductors of the plurality of coils intersect. A method for manufacturing a quadrature coil, comprising: disposing a planar conductor at a position where the coil can be suppressed while being electrically insulated from the coil. 7. The method for manufacturing a quadrature coil according to claim 6, wherein the position at which the planar conductor is to be disposed is determined by trial and error for the orthogonal coil having a structure where the position at which the planar conductor is disposed is unknown. Then, for a quadrature coil having the same structure to be manufactured thereafter, the planar conductor is arranged at a position based on the determined position, and the planar conductor is added or removed by trial and error to perform adjustment corresponding to the variation in the structure. A method for manufacturing a quadrature coil, characterized in that: