JP2005296180A - Coil for mri - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coil for MRI capable of being bent corresponding to the posture of an examinee body and suppressing image quality deterioration. <P>SOLUTION: Three plate members 1 are arranged in one line with gaps, an RF coil 20 is piled up over the three plate members 1, a bend material 2 is piled up over the gaps of the three plate members 1, and the plate members 1, the RF coil 20 and the bend material 2 are clamped by stoppers 30 and 31 and integrated with machine screws 3 and nuts 4. For the coil of the MRI, since the RF coil 20 is bent at a connection part 5, the RF coil 20 is tightly adhered to the examinee body H. The bending angle of the RF coil 20 is limited by the stoppers 30 and 31 and the fluctuation range of the resonance frequency of the RF coil 20 is within the range allowable as a frequency deviation from the transition frequency. Thus, the image quality deterioration due to the deviation of the resonance frequency of the RF coil 20 from the transition frequency is suppressed as well. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an MRI (Magnetic Resonance Imaging) coil, and more particularly to an MRI coil that can be bent in accordance with the posture of a subject and can suppress deterioration in image quality.

2. Description of the Related Art Conventionally, a “perpendicular magnet type” including a subject support means that can deform or bend a support surface so as to match the bending of a bendable portion of the subject, and a plurality of RF coils arranged along the support surface An “MRI apparatus” has been proposed, and a “flexible multi-coil for MRI” including a foldable flexible pad and a plurality of RF coils arranged on the flexible pad has been proposed. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 2000-139872

In the above-mentioned conventional “vertical magnet type MRI apparatus” and “flexible multi-coil for MRI”, a plurality of RF coils are in close contact with the subject regardless of whether the subject is stretched or bent such as the waist. It was possible to prevent image quality deterioration due to the RF coil being separated from the subject.
However, the resonance frequency of the RF coil in a state in which the bendable portion is in close contact with the subject bent is higher than the resonance frequency of the RF coil in the state of being in close contact with the subject in which the bendable portion is extended. For this reason, there is a problem in that the image quality is deteriorated due to the resonance frequency of the RF coil deviating from the resonance frequency.
Accordingly, an object of the present invention is to provide an MRI coil that can be bent according to the posture of a subject and can suppress deterioration in image quality.

In a first aspect, the present invention provides a coil support plate in which two or more plate members are foldably connected at one or more connection portions, and is supported by the coil support plate across the two or more plate members and An RF coil that can be bent at the connection portion of the coil support plate, and a fluctuation range of the resonance frequency from the resonance frequency when the RF coil is not bent to the resonance frequency when the RF coil is bent to the maximum bending angle. Bending angle limiting means for limiting the bending angle of the coil support plate within the maximum bending angle so as to fall within a range allowed as a frequency deviation from the resonance frequency. Provide a coil.
In the above configuration, the “range that is allowed as a frequency deviation from the resonance frequency” refers to a frequency deviation that allows a reduction in image quality due to deviation of the resonance frequency of the RF coil from the resonance frequency. Or the range of the frequency shift which can be adjusted by automatic tuning.
In the MRI coil according to the first aspect, since the coil support plate that supports the bendable RF coil is bent, the RF coil is covered even when the subject is bent or bent. It is possible to prevent the image quality from being deteriorated due to the close contact with the specimen and the separation of the RF coil from the subject. On the other hand, the angle at which the coil support plate is bent is limited by the bending angle limiting means, and the resonance frequency from the resonance frequency when the RF coil is not bent to the resonance frequency when the RF coil is bent to the maximum bending angle. The fluctuation range falls within a range allowed as a frequency deviation from the resonance frequency. For this reason, it is possible to suppress deterioration in image quality due to the resonance frequency of the RF coil deviating from the resonance frequency.

In a second aspect, the present invention is characterized in that, in the MRI coil configured as described above, an allowable range as a frequency deviation from the resonance frequency is “resonance frequency−10 kHz” to “resonance frequency + 10 kHz”. An MRI coil is provided.
In the MRI coil according to the second aspect, the allowable range of the frequency deviation from the resonance frequency is set to “± 10 kHz”. You can do it.

In a third aspect, the present invention provides the MRI coil, wherein the maximum bending angle is 30 ° or less in the MRI coil having the above-described configuration.
In the MRI coil according to the third aspect, the angle at which the coil support plate bends is set to 30 ° or less. However, if this is the case, image quality deterioration can be suppressed within an allowable range, and retuning is not necessary.

In a fourth aspect, the present invention provides the MRI coil having the above-described configuration, wherein the coil support plate is formed by connecting three plate members arranged in a row so that they can be bent at two connection portions. A featured MRI coil is provided.
In the MRI coil according to the fourth aspect, the adhesiveness to the subject can be enhanced over a wider range than when two plate members are used. Further, the structure can be simplified as compared with the case where four or more plate members are used.

In a fifth aspect, the present invention provides an MRI coil, characterized in that, in the MRI coil configured as described above, the RF coil has a conductive pattern formed on a flexible substrate.
In the MRI coil according to the fifth aspect, a bendable RF coil can be easily configured by forming a conductor pattern on a flexible substrate.

In a sixth aspect, the present invention provides an MRI coil, wherein the RF coil includes a loop coil in the MRI coil configured as described above.
Since the MRI coil according to the sixth aspect uses a loop coil, a wide sensitivity range can be obtained with a simple structure.

In a seventh aspect, the present invention provides an MRI coil characterized in that, in the MRI coil configured as described above, the RF coil includes an 8-shaped coil.
In the MRI coil according to the seventh aspect, since an 8-shaped coil is used, a wide sensitivity range can be obtained and the sensitivity at the center of the coil can be increased.

In an eighth aspect, the present invention provides the MRI coil configured as described above, wherein the bending angle limiting means includes a bending angle that makes the first surface of the RF coil concave, and a first surface of the RF coil. Provided is an MRI coil characterized by limiting both the bending angles to be convex.
The MRI coil according to the eighth aspect can cope with both forward bending and backward bending of the subject.

In a ninth aspect, the present invention provides the MRI coil configured as described above, wherein the bending angle limiting means is a stopper provided on each of the plate members on both sides sandwiching the connecting portion, and these stoppers are maximally folded. Provided is an MRI coil characterized in that it is in contact with each other at a curved angle and limits further bending.
In the MRI coil according to the ninth aspect, the angle at which the coil support plate is bent can be limited with a simple structure.

In a tenth aspect, the present invention provides an MRI coil characterized in that in the MRI coil having the above-described configuration, a mounting means for mounting the coil support plate on a subject is provided.
In the MRI coil according to the tenth aspect, by attaching the coil support plate to the subject, the RF coil can be brought into close contact with the subject while suitably following the posture change of the subject.

  According to the MRI coil of the present invention, the RF coil is in close contact with the subject even when the subject is bent or bent, such as the waist, and the image quality deteriorates due to the RF coil being separated from the subject. Can be prevented. In addition, since the angle at which the coil support plate is bent is limited, it is possible to suppress deterioration in image quality due to deviation of the resonance frequency of the RF coil from the resonance frequency.

  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 thereby.

FIG. 1 is a perspective view illustrating the MRI coil 100 according to the first embodiment.
In this MRI coil 100, three plate members 1 are arranged in a row with a gap therebetween, and an RF coil 20 is stacked across the three plate members 1, and a bending material is straddled across the gap between the three plate members 1. 2, the plate member 1, the RF coil 20, and the bending material 2 are sandwiched between stoppers 30 and 31 and integrated with screws 3 and nuts 4.

  The three plate members 1 are integrally connected by the RF coil 20 and the bending material 2 to constitute the coil support plate 10.

The plate member 1 is made of hard plastic, for example. Each plate member 1 is provided with a belt hole 9.
The RF coil 20 is a flexible substrate and can be bent.
The bending material 2 is, for example, a rubber plate and can be bent.
Therefore, the coil support plate 10 can be bent at the connection portion 5 of the three plate members 1.

FIG. 2 is a plan view of the RF coil 20.
The RF coil 20 is obtained by forming a loop coil 22 and an 8-shaped coil 23 on a flexible substrate 21 with a conductor pattern. The loop coil 22 is connected to the power supply line F1, and the 8-shaped coil 23 is connected to the power supply line F2.
The flexible substrate 21 is formed with a screw hole 7 'and a belt hole 9'.

FIG. 3 is a cross-sectional view of the connecting portion 5.
The plate members 1 and 1 on both sides of the connecting portion 5 are connected by the RF coil 20 and the bending material 2 so as to be bendable.

  As shown in FIG. 4, when the surface on the stopper 30 side is bent so as to be concave, the stoppers 30, 30 come into contact with each other, and further bending is restricted. The angle at this time is the first maximum bending angle θfmax. The stoppers 30 and 30 constitute first bending angle limiting means. The maximum bending angle θfmax can be changed by adjusting the distance between the stoppers 30 and 30 and the height thereof.

  As shown in FIG. 5, when the surface on the stopper 30 side is bent so as to have a convex shape, the stoppers 31 and 31 come into contact with each other, so that further bending is restricted. The angle at this time is the second maximum bending angle θrmax. The stoppers 31 and 31 constitute second bending angle limiting means. The maximum bending angle θrmax can be changed by adjusting the distance between the stoppers 31 and 31 and the height thereof.

  Compared to the resonance frequency when the RF coil 20 is not bent as shown in FIG. 3, the resonance frequency when the RF coil 20 is bent as shown in FIGS. Therefore, the fluctuation range of the resonance frequency from the resonance frequency when the RF coil 20 is not bent to the resonance frequency when the RF coil 20 is bent to the maximum bending angles θfmax and θrmax is allowed as a frequency deviation from the resonance frequency. The interval and the height of the stoppers 30 and 31 are adjusted so as to fall within the range.

In general, if the resonance frequency is fo and the allowable range of frequency deviation from the resonance frequency is ± Δf, the resonance frequency without bending the RF coil 20 becomes “fo−Δf”, and the RF coil 20 The bending angles at which the resonance frequency in the state of bending is “fo + Δf” may be the maximum bending angles θfmax and θrmax.
For example, if the allowable range of the frequency deviation from the resonance frequency is ± 10 kHz, the loop coil 22 and the 8-shaped coil 23 are set so that the resonance frequency when the RF coil 20 is not bent is “fo−10 kHz”. adjust. Next, the interval and the height of the stoppers 30 and 31 may be adjusted so that the RF coil 20 is bent so that it does not bend beyond the bending angle at which the resonance frequency becomes “fo + 10 kHz”.

Conversely, the maximum bending angles θfmax and θrmax are determined in advance, the resonance frequency when the RF coil 20 is not bent is “fo−Δf”, and the RF coil 20 is bent to the maximum bending angles θfmax and θrmax. Alternatively, the loop coil 22 or the figure-shaped coil 23 may be designed so that the resonance frequency becomes “fo + Δf”.
For example, the interval and height of the stoppers 30 and 31 are adjusted so that the maximum bending angle θfmax = θrmax = 30 °, and if the allowable range of frequency deviation from the resonance frequency is ± 10 kHz, the RF coil 20 is The loop coil 22 and the 8-shaped coil 23 are designed so that the resonance frequency when not bent is “fo−10 kHz” and the resonance frequency when the RF coil 20 is bent to the maximum bending angle is “fo + 10 kHz”. That's fine.

6 and 7 are explanatory diagrams showing an example of using the MRI coil 100 when MR imaging of the lumbar spine of the subject H is performed.
The subject H is placed in a lateral position on the table of an MRI apparatus (not shown). Then, the MRI coil 100 is attached to the back surface of the subject H by the belt 8 so as to cover the lumbar spine.
As shown in FIG. 6, even if the subject H bends forward, the MRI coil 100 bends in accordance with the posture of the waist of the subject H and comes into close contact with the subject H. However, it does not bend beyond the maximum bending angle θfmax.
As shown in FIG. 7, even when the subject H is bent backward, the MRI coil 100 is bent according to the posture of the waist of the subject H and is in close contact with the subject H. However, it does not bend beyond the maximum bending angle θrmax.

  According to the MRI coil 100 of the first embodiment, since the RF coil 20 is bent at the connection portion 5, the RF coil 20 is in the subject regardless of whether the subject H is bent or bent. It is possible to prevent the image quality from being deteriorated due to the close contact with H and the RF coil 20 being separated from the subject H. On the other hand, the angle at which the RF coil 20 is bent is limited by the stoppers 30 and 31, and the resonance frequency from the resonance frequency when the RF coil 20 is not bent to the resonance frequency when the RF coil 20 is bent to the maximum bending angle. The fluctuation range is within a range allowed as a frequency deviation from the resonance frequency. For this reason, it is possible to suppress deterioration in image quality due to the resonance frequency of the RF coil 20 deviating from the resonance frequency.

  The coil for MRI of the present invention can be used for MR imaging of bent parts such as the waist, neck, and elbow. Further, it can be used for MR imaging of a person who is difficult to lie in the supine position or prone position, such as an elderly person whose spine is bent.

1 is a perspective view showing an MRI coil according to Example 1. FIG. 1 is a plan view showing a configuration of an RF coil according to Example 1. FIG. FIG. 3 is a cross-sectional view showing a connecting portion of an MRI coil according to Example 1; It is explanatory drawing which shows the largest bending angle at the time of bending the 1st surface of the coil for MRI concerning Example 1 in concave shape. It is explanatory drawing which shows the largest bending angle at the time of bending the 1st surface of the coil for MRI concerning Example 1 in convex shape. It is explanatory drawing which shows the usage example in the forward bending state of the subject of the coil for MRI concerning Example 1. FIG. FIG. 6 is an explanatory diagram illustrating an example of using the MRI coil according to the first embodiment in a back bending state of a subject.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plate member 2 Bending part 3 Screw 4 Nut 5 Connection part 7 Screw hole 8 Belt 9, 9 'Belt hole 10 Coil support plate 20 RF coil 21 Flexible substrate 22 Loop coil 23 8-shaped coil 30, 31 Stopper 100 For MRI Coil F1, F2 Feed line H Subject

Claims (10)

  A coil support plate in which two or more plate members are foldably connected at one or more connection portions, and supported by the coil support plate across the two or more plate members and bendable at the connection portions of the coil support plates. The fluctuation range of the resonance frequency from the resonance frequency when the RF coil and the RF coil are not bent to the resonance frequency when the RF coil is bent to the maximum bending angle is allowed as a frequency deviation from the resonance frequency. A coil for MRI, comprising bending angle limiting means for limiting a bending angle of the coil support plate to be within the maximum bending angle so as to fall within a range.   2. The MRI coil according to claim 1, wherein an allowable range as a frequency deviation from the resonance frequency is “resonance frequency−10 kHz” to “resonance frequency + 10 kHz”. 3.   3. The MRI coil according to claim 1, wherein the maximum bending angle is 30 ° or less. 4.   The MRI coil according to any one of claims 1 to 3, wherein the coil support plate is formed by connecting three plate members arranged in a row so that they can be bent at two connection portions. Characteristic MRI coil.   5. The MRI coil according to claim 1, wherein the RF coil is formed by forming a conductor pattern on a flexible substrate. 6.   The MRI coil according to any one of claims 1 to 5, wherein the RF coil includes a loop coil.   The MRI coil according to any one of claims 1 to 6, wherein the RF coil includes an 8-shaped coil.   The MRI coil according to any one of claims 1 to 7, wherein the bending angle limiting means includes a bending angle that makes the first surface of the RF coil concave, and a first surface of the RF coil. An MRI coil characterized by restricting both the bending angles to be convex.   9. The MRI coil according to claim 1, wherein the bending angle limiting means is a stopper provided on each of plate members on both sides sandwiching the connecting portion, and the stopper is a maximum folding. A coil for MRI, which is in contact with each other at a curved angle and limits further bending.   10. The MRI coil according to claim 1, further comprising mounting means for mounting the coil support plate on a subject.

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