JP2004202047A - Receiving coil for mri, and mri system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To set a phase encoding direction in performing SENSE (Sensitivity Encoding) to both of an AP direction and an RL direction. <P>SOLUTION: Receiving coils 10 for MRI receive an MR signal from a subject present in a space with an magnetostatic field impressed in the y direction (vertical direction). When the body axial direction of the subject is defined as a z direction and a direction to be orthogonally crossed with the z and y directions is defined as an x direction, a first saddle coil 1, a second saddle coil 2, and a third saddle coil 4, which have a cylindrical surface E having a central axis Ax in the z direction, a curved side in the circumferential direction of a nearly cylindrical surface, and a straight side in the z direction, are arranged in the circumferential direction of the cylindrical surface E. Then a solenoid coil 5 consisting of a loop which goes once round the cylindrical surface E is disposed at the center position of the z direction concerning the saddle coils 1-4. Thus, the phase encoding direction can be selected to be the AP or RL direction, so that imaging by SENSE is performed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reception coil for MRI (Magnetic Resonance Imaging) and an MRI apparatus. The present invention relates to an MRI receiving coil that can also set the MRI and an MRI apparatus including the MRI receiving coil.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is known a technique of performing SENSE using a pair of solenoid coils opposed to an AP direction of a subject entering a static magnetic field space of an MRI apparatus (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-2002-177245 (FIG. 2)
[0004]
[Problems to be solved by the invention]
When SENSE is performed using a pair of solenoid coils opposed to each other in the AP direction, the phase encoding direction can be set only in the AP direction, and the phase encoding direction cannot be set in the RL direction or the SI direction (body axis direction).
If the pair of solenoid coils are opposed to each other in the RL direction, the phase encoding direction can be set in the RL direction, but the phase encoding direction cannot be set in the AP direction or the SI direction. If a pair of solenoid coils are opposed to each other in the SI direction, the phase encoding direction can be set in the SI direction, but the phase encoding direction cannot be set in the AP direction or the RL direction.
Therefore, an object of the present invention is to provide an MRI receiving coil capable of setting the phase encoding direction in both the AP direction and the RL direction, and an MRI apparatus including the MRI receiving coil.
[0005]
[Means for Solving the Problems]
In a first aspect, the present invention relates to an MRI receiving coil for receiving an MR signal from a subject entering a static magnetic field space of an MRI apparatus, wherein the receiving coil for the MRI apparatus is arranged in a body axis direction of the subject entering the static magnetic field space. Is the z-direction, the vertical direction is the y-direction, and the direction orthogonal to the z-direction and the y-direction is the x-direction. A circumferential curved side of a cylindrical surface or a substantially cylindrical surface having a central axis in the z-direction and the z-direction The first to fourth saddle coils having the following straight sides are arranged in the circumferential direction of the cylindrical surface or the substantially cylindrical surface. An MRI receiving coil provided at a center position in the z direction is provided.
In the MRI receiving coil according to the first aspect, since the first to fourth saddle coils are arranged in the circumferential direction of the cylinder surrounding the subject, these saddle coils are arranged in two adjacent directions, that is, the first and second saddle coils. In the adjacent direction of the saddle coil (= adjacent direction of the third and fourth saddle coils) and in the adjacent direction of the fourth and first saddle coils (= adjacent direction of the second and third saddle coils). The phase encoding direction can be set. Therefore, if the first and second saddle coils, the third saddle coil, and the fourth saddle coil are arranged symmetrically with respect to the yz plane or the xz plane, the phase encoding direction can be changed in both the AP direction and the RL direction. Can also be set.
Further, the sensitivity distribution of each saddle coil can be obtained by the solenoid coil.
[0006]
In a second aspect, the present invention provides the MRI receiving coil having the above-described configuration, in which the solenoid coil including a loop having one or more rounds of the cylindrical surface or the substantially cylindrical surface is provided separately from the solenoid coil. Provided is an MRI receiving coil, wherein the receiving coil is provided off the center position in the z direction.
In the MRI receiving coil according to the second aspect, since the plurality of solenoid coils face each other in the z direction, the phase encoding direction can be further set in the SI direction.
[0007]
In a third aspect, the present invention provides the MRI receiving coil having the above configuration, wherein the size of the curved side of each of the first to fourth saddle coils is 1/4 of the circumferential direction of the cylindrical surface or the substantially cylindrical surface, or Provided is a receiving coil for MRI, which is approximately 1/4.
In the MRI receiving coil according to the third aspect, the first to fourth saddle coils can substantially cover the circumferential direction of the cylindrical surface or the substantially cylindrical surface.
[0008]
According to a fourth aspect of the present invention, in the MRI receiving coil having the above-described configuration, the first saddle coil and the second saddle coil are partially overlapped so that mutual inductance is substantially zero, and The saddle coil and the fourth saddle coil are partially overlapped so that the mutual inductance becomes substantially zero, and the first saddle coil, the second saddle coil, the third saddle coil, and the fourth saddle coil are different from each other. Provided is a receiving coil for MRI, which has no overlap.
In the MRI receiving coil according to the fourth aspect, mutual interference between the first to fourth saddle coils can be suppressed.
[0009]
In a fifth aspect, the present invention provides the MRI receiving coil having the above-described configuration, wherein the first and second saddle coils, the third saddle coil, and the fourth saddle coil are arranged with respect to a yz plane or an xz plane. And a receiving coil for MRI characterized by being arranged symmetrically.
In the MRI receiving coil according to the fifth aspect, the phase encoding direction can be set in both the AP direction and the RL direction.
[0010]
In a sixth aspect, the present invention provides the MRI receiving coil having the above-described configuration, wherein the first end of the first saddle coil and the first end of the second saddle coil are grounded ends. A first end of the third saddle coil and a first end of the fourth saddle coil are a common grounded end, and a receiving coil for MRI is provided.
In the receiving coil for MRI according to the sixth aspect, by using a common grounding end, wiring can be easily routed and electrical stability can be improved.
[0011]
In a seventh aspect, the present invention provides an MRI receiving coil characterized by arranging a plurality of MRI receiving coils having the above configuration in the z direction.
With the MRI receiving coil according to the seventh aspect, the imaging region can be enlarged in the z direction. Further, the phase encoding direction can be set also in the SI direction.
[0012]
In an eighth aspect, the present invention is characterized in that a plurality of MRI receiving coils arranged in the z direction are partially overlapped so that mutual inductance of the MRI receiving coils arranged in the z direction becomes zero. An MRI receiving coil is provided.
In the MRI receiving coil according to the eighth aspect, mutual interference between a plurality of MRI receiving coils arranged in the z direction can be suppressed.
[0013]
In a ninth aspect, the present invention provides an MRI apparatus comprising the MRI receiving coil having the above-described configuration.
In the MRI apparatus according to the ninth aspect, imaging can be performed with the phase encoding direction set in both the AP direction and the RL direction.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
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.
[0015]
-1st Embodiment-
FIG. 1 is a perspective view showing an MRI receiving coil according to the first embodiment.
The MRI receiving coil 10 receives an MR signal from a subject entering a space to which a static magnetic field is applied in the y direction (vertical direction), and sets the body axis direction of the subject as the z direction. A first saddle having a curved side of a cylindrical surface E having a central axis Ax in the z direction and a curved side of a substantially cylindrical surface and a straight side in the z direction, where a direction orthogonal to the z direction and the y direction is an x direction. The coil 1, the second saddle coil 2, the third saddle coil 3, and the fourth saddle coil 4 are arranged in the circumferential direction of the cylindrical surface E or the substantially cylindrical surface, and at least one round of the cylindrical surface E or the substantially cylindrical surface. The configuration is such that the center position of the solenoid coil 5 composed of a loop is aligned with the center position of the saddle coils 1 to 4 in the z direction.
[0016]
The size of the curved sides of the saddle coils 1 to 4 is 1/4 or approximately 1/4 of the circumferential direction of the cylindrical surface E or the substantially cylindrical surface.
[0017]
The first saddle coil 1 and the second saddle coil 2 are partially overlapped so that mutual inductance becomes substantially zero.
The third saddle coil 3 and the fourth saddle coil 4 are partially overlapped so that the mutual inductance becomes substantially zero.
The first saddle coil 1 and the second saddle coil 2 do not overlap with the third saddle coil 3 and the fourth saddle coil 4.
[0018]
The first saddle coil 1 and the second saddle coil 2 and the third saddle coil 3 and the fourth saddle coil 4 receive MR signals from a subject lying inside the cylindrical surface E. Assuming, they are arranged symmetrically with respect to the yz plane. However, they may be arranged symmetrically with respect to the xz plane.
[0019]
FIG. 2 is an explanatory diagram showing an electric circuit at the ends of the first saddle coil 1 and the second saddle coil 2.
The first end of the first saddle coil 1 and the first end of the second saddle coil 2 are common grounding ends. The second end of the first saddle coil 1 is a terminal a1 connected to a preamplifier (not shown) via the resonance coil L1. The second end of the second saddle coil 2 is a terminal a2 connected to a preamplifier (not shown) via the resonance coil L2.
The resonance coil L1, the resonance capacitor C1, and the diode D1 constitute a blocking circuit for an RF pulse signal. The resonance coil L2, the resonance capacitor C2, and the diode D2 constitute a blocking circuit for the RF pulse signal.
[0020]
FIG. 3 is an explanatory diagram showing an electric circuit at the end of the third saddle coil 3 and the fourth saddle coil 4.
The first end of the third saddle coil 3 and the first end of the fourth saddle coil 4 are common grounding ends. The second end of the third saddle coil 3 is a terminal a3 connected to a preamplifier (not shown) via the resonance coil L3. A second end of the fourth saddle coil 4 is a terminal a4 connected to a preamplifier (not shown) via the resonance coil L4.
In addition, the resonance coil L3, the resonance capacitor C3, and the diode D3 constitute a blocking circuit for the RF pulse signal. The resonance coil L4, the resonance capacitor C4, and the diode D4 constitute a blocking circuit for the RF pulse signal.
[0021]
FIG. 4 is an explanatory diagram showing an electric circuit at the end of the solenoid coil 5.
The first end of the solenoid coil 5 is a ground end. The second end is a terminal a5 connected to a preamplifier (not shown) via the resonance coil L5.
The resonance coil L5, the resonance capacitor C5, and the diode D5 constitute a blocking circuit for the RF pulse signal.
[0022]
When performing imaging by SENSE using the saddle coils 1 to 4 of the MRI receiving coil 10, since the saddle coils 1 to 4 have different sensitivity distributions in the x direction and the y direction, the phase encoding direction is changed in the RL direction. It can also be set in the AP direction.
[0023]
The sensitivity distribution of the saddle coils 1 to 4 can be obtained by comparing each image captured by the saddle coils 1 to 4 with an image captured by the solenoid coil 5. That is, the pixel value of the j-th pixel of the image taken with the saddle coil i (= 1, 2, 3, 4) and a _i ^j, the pixel value of the j-th pixel of the image taken by the solenoid coil 5 a when the ₅ ^j, the sensitivity coefficients S _i ^j regarding the j-th pixel of the image taken with the saddle coil i,
^{_{S i j = a i j /}} a 5 j
Is required.
Since the mutual inductance between the saddle coils 1 to 4 and the solenoid coil 5 is 0, the SNR does not decrease due to noise correlation.
[0024]
An image can be taken using the saddle coils 1 to 4 and the solenoid coil 5 as a phased array coil.
In this case, first, obtaining the sensitivity correction image by using the image and the sensitivity coefficients S _i ^j obtained in the saddle coils 1-4. That is, when the pixel value of the j-th pixel of the sensitivity corrected image is P _j ^1-4 ,
^{_{P j 1-4 = i = 1 Σ}} 4 {(S i j) * × a i j / i = 1 Σ 4 {| S i j | 2}}
Here, _(S ^{i j) *} _is a complex conjugate of _S ^{i j.}
[0025]
Next, a final image is obtained by synthesizing the sensitivity-corrected image and the image captured by the solenoid coil 5 by a sum of squares method. That is, when the pixel value of the j-th pixel of the image captured by the solenoid coil 5 is P _j ⁵ and the pixel value of the j-th pixel of the final image is P _j ^final ,
^{_{P j final = √ {(P}} j 5) 2 + (P j 1-4) 2}
[0026]
-2nd Embodiment-
Like the MRI receiving coil 20 shown in FIG. 5, two or more solenoid coils 5 to 7 may be arranged in the z direction.
In the MRI receiving coil 20, by using two or more solenoid coils 5 to 7, SENSE in which the phase encoding direction is set to the SI direction is also possible.
[0027]
-Third embodiment-
Like the MRI receiving coil 30 shown in FIG. 6, two or more MRI receiving coils 10 shown in FIG. 1 may be arranged in the z direction. In this case, it is preferable to partially overlap the MRI receiving coils 10 arranged in the z direction so that the mutual inductance becomes zero.
In FIG. 6, the two MRI receiving coils 10_1 and 10_2 are arranged in the z direction. Then, for example, the first saddle coil 1-1 of the MRI receiving coil 10_1 and the first saddle coil 1-2 of the MRI receiving coil 10_2 are partially overlapped so that the mutual inductance becomes zero. I have.
In the MRI receiving coil 30, SENSE set in the SI direction can be performed by using the saddle coils 1_1 to 4_2.
[0028]
-Fourth embodiment-
FIG. 7 is a configuration diagram illustrating an MRI apparatus 100 according to the fourth embodiment.
In the MRI apparatus 100, the magnet assembly 10101 has a bore (space portion) for inserting a subject therein, and a gradient coil (a gradient coil is an X-axis) that forms a gradient magnetic field by surrounding the bore. , Y-axis, and Z-axis coils, and a slice axis, a warp axis, and a lead axis are determined by a combination of these coils. 101G, and transmission for applying an RF pulse for exciting spins of atomic nuclei in the subject. The apparatus includes a coil 101T, a receiving coil 101R for detecting an NMR signal from a subject, a static magnetic field power supply 102 for generating a static magnetic field, and a static magnetic field coil 101C.
Note that a permanent magnet may be used instead of the static magnetic field power supply 102 and the static magnetic field coil 101C (superconducting magnet).
[0029]
The receiving coil 101R is the MRI receiving coil 10 according to the first embodiment, the MRI receiving coil 20 according to the second embodiment, or the MRI receiving coil 30 according to the third embodiment.
[0030]
The gradient coil 101G is connected to the gradient coil driving circuit 103. Further, the transmission coil 101T is connected to the RF power amplifier 104. The receiving coil 101R is connected to the preamplifier 105.
[0031]
The sequence storage circuit 8 operates the gradient coil drive circuit 103 based on the stored pulse sequence in accordance with a command from the computer 107 to form a gradient magnetic field with the gradient coil 101G and operate the gate modulation circuit 9. , A high-frequency output signal from the RF oscillation circuit 15 is modulated into a pulse signal having a predetermined timing and a predetermined envelope, and the modulated pulse signal is applied to the RF power amplifier 104 as an excitation pulse. , And transmits an RF pulse.
[0032]
The preamplifier 105 amplifies the NMR signal from the subject detected by the receiving coil 101R of the magnet assembly 101 and inputs the amplified signal to the phase detector 12. The phase detector 12 uses the output of the RF oscillation circuit 15 as a reference signal, performs phase detection on the NMR signal from the preamplifier 105, and supplies the NMR signal to the A / D converter 11. The A / D converter 11 converts the analog signal after phase detection into MR data of a digital signal, and inputs the data to the computer 107.
[0033]
The computer 107 reads the MR data from the A / D converter 11 and performs an image reconstruction process to generate an MR image. The computer 107 is responsible for overall control such as receiving information input from the console 13.
The display device 106 displays the MR image.
[0034]
The above MRI apparatus 100 includes the MRI receiving coil 10 according to the first embodiment, the MRI receiving coil 20 according to the second embodiment, or the MRI receiving coil 30 according to the third embodiment. It is possible to set the phase encoding direction to the direction possible with the MRI receiving coils 10, 20, and 30 and perform imaging.
[0035]
-Other embodiments-
In the MRI receiving coils 10, 20, and 30 according to the first, second, and third embodiments, a part of the saddle coil is overlapped so that the mutual inductance becomes zero, but the g-factor is optimized. Therefore, a part of the saddle coil may be overlapped or the overlapped portion may be eliminated so that the mutual inductance does not become zero. In this case, the mutual inductance may be reduced to a negligible level by a preamplifier having a low input impedance. A known mutual inductance compensation circuit may be added to cancel the coupling between the coils.
[0036]
【The invention's effect】
According to the receiving coil for MRI and the MRI apparatus of the present invention, it is possible to perform SENSE imaging by selecting the AP direction and the RL direction in the phase encoding direction.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an MRI receiving coil according to a first embodiment.
FIG. 2 is an explanatory diagram showing a circuit at an end of a first saddle coil and a second saddle coil.
FIG. 3 is an explanatory diagram showing a circuit at an end of a third saddle coil and a fourth saddle coil.
FIG. 4 is an explanatory diagram showing a circuit at an end of a solenoid coil.
FIG. 5 is a perspective view showing an MRI receiving coil according to a second embodiment.
FIG. 6 is a perspective view showing an MRI receiving coil according to a third embodiment.
FIG. 7 is a configuration diagram illustrating an MRI apparatus according to a fourth embodiment.
[Explanation of symbols]
1,2,3,4 Saddle coil 1_1,2_1,3_1,4_1 Saddle coil 1_2,2_2,3_2,4_2 Saddle coil 5,6,7 Solenoid coil 5_1,5_2 Solenoid coil 10,20,30 MRI reception coil 10_1,1 10_2 MRI receiving coil 100 MRI apparatus

Claims (9)

An MRI receiving coil for receiving an MR signal from a subject entering a static magnetic field space of an MRI apparatus, wherein a body axis direction of the subject entering the static magnetic field space is defined as a z direction, and a vertical direction is defined as a y direction. When a direction orthogonal to the z direction and the y direction is an x direction, first to fourth having a curved side in the circumferential direction of a cylindrical surface or a substantially cylindrical surface having a central axis in the z direction and a straight side in the z direction. Are arranged in the circumferential direction of the cylindrical surface or the substantially cylindrical surface, and a solenoid coil including a loop that makes one or more rounds of the cylindrical surface or the substantially cylindrical surface is provided at the center position of the saddle coil in the z direction. Characteristic MRI receiver coil. 2. The MRI receiving coil according to claim 1, wherein, apart from the solenoid coil, a solenoid coil including a loop that makes one or more rounds of the cylindrical surface or the substantially cylindrical surface is removed from a center position of the saddle coil in the z direction. 3. A receiving coil for MRI, wherein the receiving coil is provided in the form of a coil. 3. The receiving coil for MRI according to claim 1, wherein a size of a curved side of each of the first to fourth saddle coils is 1/4 or 1/1 of a circumferential direction of the cylindrical surface or the substantially cylindrical surface. 4. An MRI receiving coil, comprising: The MRI receiving coil according to any one of claims 1 to 3, wherein the first saddle coil and the second saddle coil are partially overlapped so that mutual inductance is substantially zero, and The saddle coil and the fourth saddle coil are partially overlapped so that mutual inductance becomes substantially zero. An MRI receiving coil characterized by no overlap. 5. The MRI receiving coil according to claim 4, wherein the first and second saddle coils, the third saddle coil, and the fourth saddle coil are symmetrically arranged with respect to a yz plane or an xz plane. A receiving coil for MRI, characterized in that: 6. The MRI receiving coil according to claim 4, wherein the first end of the first saddle coil and the first end of the second saddle coil are a common grounded end, and An MRI receiving coil, wherein the first end of the third saddle coil and the first end of the fourth saddle coil are a common grounded end. 7. An MRI receiving coil, wherein a plurality of the MRI receiving coils according to claim 1 are arranged in the z direction. 8. The MRI receiving coil according to claim 7, wherein a plurality of MRI receiving coils arranged in the z direction are partially overlapped so that mutual inductance is zero. An MRI apparatus comprising the MRI receiving coil according to any one of claims 1 to 8.

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