JP2002052002A - Rf coil and magnetic resonance imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bird cage type RF coil, the size of which is controllable according to an object ands a magnetic resonance imaging apparatus having the RF coil. SOLUTION: This RF coil is provided with a pair of ring elements 802, a pair of support plate members 80 respectively supporting the paired ring elements 802, a mounting frame member 830 for removably mounting the paired support plate members, and plural linear elements 804 with a variable length for connecting the ring elements to each other to constitute the bird cage coil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an RF coil (ra
The present invention relates to a dio frequency coil and a magnetic resonance imaging apparatus, and particularly to a birdcage.
The present invention relates to a ge) type RF coil and a magnetic resonance imaging apparatus provided with such an RF coil.

[0002]

2. Description of the Related Art Magnetic resonance imaging (MRI: Magneti)
c Resonance Imaging) device
An imaging target (patient or the like) is placed in an internal space of a magnet system, that is, a space in which a static magnetic field is formed, and a gradient magnetic field and a high-frequency magnetic field are applied to generate a magnetic resonance signal in the target. A tomographic image is generated (reconstructed) based on the received signal.

A birdcage type R coil is used as an RF coil used for applying a high frequency magnetic field and receiving a magnetic resonance signal.
There is an F coil. This is also called a birdcage coil. The birdcage coil has a uniformity of the intensity distribution of the high-frequency magnetic field and an SNR (signal-to-n
It is used heavily because of its excellent oil ratio.

[0004]

The birdcage coil has a generally cylindrical shape and is used by housing the object to be photographed therein. The filling factor (filling factor) of the space must be appropriate, and the ratio between the diameter and the length of the birdcage coil must also be appropriate.

For this reason, a dedicated birdcage coil having a size suitable for the region to be photographed, such as the head, trunk, leg, or arm, is used. However, even a dedicated birdcage coil is used. However, an appropriate filling factor may not always be obtained due to individual differences in the physique of the target, and the desired performance may not be exhibited.

It is an object of the present invention to provide a birdcage-type RF coil whose size can be adjusted according to an object, and a magnetic resonance imaging apparatus having such an RF coil.

[0007]

Means for Solving the Problems (1) According to one aspect of the present invention, there is provided a pair of ring elements forming a part of a birdcage type coil, and the pair of ring elements. And a pair of support plate members each having a through hole corresponding to the pair of ring elements, and the pair of support plate members being detachably mounted with the through holes facing each other. A mounting frame member in which a distance between the pair of support plate members is variable;
A plurality of linear elements having a variable length that electrically connect the pair of ring elements to each other and form a birdcage coil together with the pair of ring elements. .

In the invention according to this aspect, since the support plate member for supporting the loop element is detachable from the mounting frame member, it is possible to replace the support plate member with a ring element corresponding to the target thickness. . In addition, since the distance between the pair of support plate members of the mounting frame member is variable, and the length of the linear element is variable, the length of the birdcage coil can be adjusted. Become. As a result, the filling factor and the ratio of diameter to length can be optimized, and the desired performance of the birdcage coil can be exhibited.

(2) According to another aspect of the present invention for solving the above-mentioned problems, the pair of support plate members may include a plurality of pairs of support plate members each supporting a ring element having a different diameter. The RF coil according to (1), which is a pair.

In the invention from this viewpoint, in addition to (1),
Since a plurality of types of support plate members are provided, each of which supports a ring element having a different diameter, it is possible to select a support plate member having a ring element suitable for the target thickness.

(3) According to another aspect of the invention for solving the above-mentioned problems, the support plate member has a plurality of grooves for guiding the ends of the plurality of linear elements to the surface of the ring element. An RF coil according to (1) or (2), characterized in that:

In the invention according to this aspect, in addition to (1) or (2), the support plate member is provided with a plurality of grooves for guiding the ends of the plurality of linear elements to the surface of the ring element. Can be used to position a plurality of linear elements with respect to the ring element.

(4) According to another aspect of the invention for solving the above problems, the support plate member and the mounting frame member are non-magnetic and non-conductive. (3) The RF coil according to any one of (3).

According to the invention from this viewpoint, in addition to any one of (1) to (3), since the supporting plate member and the mounting frame member are non-magnetic and non-conductive, the static magnetic resonance imaging method can be used. Does not affect magnetic and gradient fields.

(5) According to another aspect of the invention for solving the above problems, an image is formed based on a magnetic resonance signal generated inside a target using a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field. A magnetic resonance imaging apparatus, comprising: a pair of ring elements forming a part of a birdcage coil as an RF coil for performing at least one of the formation of the high-frequency magnetic field and the reception of the magnetic resonance signal. A pair of support plate members each supporting the pair of ring elements and having a through hole corresponding to the pair of ring elements, and a state in which the pair of support plate members face the through holes. The pair of ring elements are electrically connected to each other, and the pair of ring elements are detachably attached to each other and the distance between the pair of support plate members is variable. Length comprises an RF coil having a plurality of linear elements variable, the constituting a birdcage coil with the ring element, that is a magnetic resonance imaging apparatus according to claim.

In the invention according to this aspect, since the support plate member for supporting the loop element is detachable from the mounting frame member, it is possible to replace the support plate member with a ring element corresponding to the target thickness. . In addition, since the distance between the pair of support plate members of the mounting frame member is variable, and the length of the linear element is variable, the length of the birdcage coil can be adjusted. Become.

Thus, the filling factor and the ratio between the diameter and the length can be optimized, and the desired performance of the birdcage coil can be exhibited to perform the magnetic resonance imaging properly.

(6) According to another aspect of the present invention for solving the above-mentioned problems, the pair of support plate members may include a plurality of pairs of support plate members that respectively support ring elements having different diameters. (5) The magnetic resonance imaging apparatus according to (5), which is a pair.

In the invention from this viewpoint, in addition to (5),
Since a plurality of types of support plate members are provided, each of which supports a ring element having a different diameter, it is possible to select a support plate member having a ring element suitable for the target thickness.

(7) According to another aspect of the invention for solving the above-mentioned problem, the support plate member has a plurality of grooves for guiding the ends of the plurality of linear elements to the surface of the ring element. The magnetic resonance imaging apparatus according to (5) or (6), wherein

In the invention according to this aspect, in addition to (5) or (6), a plurality of grooves for guiding the ends of the plurality of linear elements to the surface of the ring element are provided on the support plate member. Can be used to position a plurality of linear elements with respect to the ring element.

(8) According to another aspect of the invention for solving the above-mentioned problem, the support plate member and the mounting frame member are non-magnetic and non-conductive. The magnetic resonance imaging apparatus according to any one of (7).

According to the invention from this viewpoint, in addition to any one of (5) to (7), since the support plate member and the mounting frame member are non-magnetic and non-conductive, static magnetic resonance imaging is possible. Does not affect magnetic and gradient fields.

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the magnetic resonance imaging apparatus. This device is an example of an embodiment of the present invention. The configuration of the present apparatus shows an example of an embodiment relating to the apparatus of the present invention.

As shown in FIG. 1, the present apparatus has a magnet system 100. The magnet system 100 includes a main magnetic field coil unit 102 and a gradient coil unit 1.
06. Each of these coil portions has a substantially cylindrical shape and is arranged coaxially with each other.

An object 300 to be photographed is mounted on a cradle 500 in a substantially cylindrical internal space (bore) of the magnet system 100, and is carried in and out by carrying means (not shown). The target 300 is, for example, a patient or the like. The subject 300 has the RF coil unit 1 on the arm.
08 is attached. The RF coil unit 108 has a substantially cylindrical shape. The subject 300 passes through one arm inside the cylinder.

The RF coil section 108 is an example of an embodiment of the RF coil of the present invention. The configuration of the present RF coil unit 108 shows an example of an embodiment relating to the RF coil of the present invention. The RF coil unit 108 will be described later.

The main magnetic field coil section 102 forms a static magnetic field in the internal space of the magnet system 100. The direction of the static magnetic field is substantially parallel to the direction of the body axis of the object 300. That is, a so-called horizontal magnetic field is formed. The main magnetic field coil unit 102 is configured using, for example, a superconducting coil. It is needless to say that not only the superconducting coil but also a normal conducting coil may be used.

The gradient coil section 106 generates a gradient magnetic field for giving a gradient to the static magnetic field strength. The generated gradient magnetic fields are a slice gradient magnetic field, a readout gradient magnetic field, and a phase encode gradient magnetic field. The gradient coil unit 1 corresponds to these three types of gradient magnetic fields.
Reference numeral 06 has three gradient coils (not shown).

The RF coil unit 108 forms a high-frequency magnetic field for exciting spins in the arm of the object 300 in its internal space. Hereinafter, forming a high-frequency magnetic field is also referred to as transmitting an RF excitation signal. The RF coil unit 108 also receives an electromagnetic wave generated by the excited spin, that is, a magnetic resonance signal.

The gradient coil unit 106 includes a gradient driving unit 130
Is connected. The gradient driving unit 130 is a gradient coil unit 1
A drive signal is given to 06 to generate a gradient magnetic field. The gradient drive unit 130 has three drive circuits (not shown) corresponding to the three gradient coils in the gradient coil unit 106.

The RF coil unit 108 includes an RF driving unit 140
Is connected. The RF driving unit 140 is the RF coil unit 1
08, a drive signal is given, an RF excitation signal is transmitted, and the target 3
Excite the spins in the body of 00.

The RF coil unit 108 includes a data collection unit 15
0 is connected. The data collection unit 150 captures a received signal received by the RF coil unit 108 and collects the received signal as view data.

A control unit 160 is connected to the gradient driving unit 130, the RF driving unit 140, and the data collection unit 150. The control unit 160 controls the gradient driving unit 130 to the data collection unit 150 to perform photographing.

The output side of the data collection unit 150 is connected to the data processing unit 170. The data processing unit 170 is configured using, for example, a computer. The data processing unit 170 includes a memory (me
(money). The memory stores a program for the data processing unit 170 and various data. The function of the present apparatus is realized by the data processing unit 170 executing a program stored in the memory.

The data processing unit 170 includes the data collection unit 15
The data taken from 0 is stored in the memory. A data space is formed in the memory. The data space is two-dimensional
It constitutes a Fourier space. The data processing unit 170 performs two-dimensional inverse Fourier transform on the data in the two-dimensional Fourier space to generate an image of the target 300 (reconstruction).
I do. Hereinafter, the two-dimensional Fourier space is referred to as a k-space (k-s
space).

The data processing section 170 is connected to the control section 160. The data processing unit 170 is at a higher level than the control unit 160 and controls it. The display section 180 and the operation section 190 are connected to the data processing section 170. The display unit 180 includes a graphic display (graphic).
display). The operation unit 190 is a pointing device.
e) is composed of a keyboard provided with e).

The display section 180 displays the reconstructed image output from the data processing section 170 and various information. The operation unit 190 is operated by an operator, and inputs various commands and information to the data processing unit 170. The operator operates the present apparatus interactively through the display unit 180 and the operation unit 190.

FIG. 2 shows an example of a pulse sequence used for magnetic resonance imaging. This pulse sequence is a pulse sequence based on a gradient echo (GRE) method.

That is, (1) is the RF in the GRE method.
A sequence of α ° pulses for excitation, (2)
(3), (4) and (5) are the sequences of the slice gradient Gs, readout gradient Gr, phase encode gradient Gp and gradient echo MR, respectively. The α ° pulse is represented by the center signal.
The pulse sequence proceeds from left to right along the time axis t.

As shown in the figure, α ° excitation of the spin is performed by the α ° pulse. Flip angle (flip
angle) α ° is 90 ° or less. At this time, a slice gradient Gs is applied, and selective excitation for a predetermined slice is performed. With the configuration of the RF coil unit 108 as described below, RF excitation is effectively performed.

After α ° excitation, the phase encode gradient Gp
Performs phase encoding of the spin. next,
The spin is first dephased by the readout gradient Gr, and then the spin is rephased (r
ephase) to generate a gradient echo MR. The signal strength of the gradient echo MR is α °
It becomes maximum at the time point after the echo time (echo time) TE from the excitation.

The gradient echo MR is received by the RF coil unit 108. With the configuration of the RF coil unit 108 as described later, the gradient echo MR is received with good SNR. This received signal is collected by the data collection unit 150 as view data. As a result, view data with a good SNR can be obtained.

Such a pulse sequence has a period TR
(Repetition time) is repeated 64 to 512 times. The phase encoding gradient Gp is changed for each repetition, and a different phase encoding is performed each time. As a result, view data of 64 to 512 views filling the k space is obtained.

FIG. 3 shows another example of the pulse sequence for magnetic resonance imaging. This pulse sequence is a pulse sequence of a spin echo (SE: Spin Echo) method.

That is, (1) is a sequence of 90 ° and 180 ° pulses for RF excitation in the SE method, and (2), (3), (4) and (5) are slice gradients, respectively. Gs, readout gradient G
r, phase encoding gradient Gp and spin echo M
This is a sequence of R. Note that a 90 ° pulse and 18
Each 0 ° pulse is represented by a center signal. The pulse sequence proceeds from left to right along the time axis t.

As shown in the figure, 90 ° excitation of spin is performed by a 90 ° pulse. At this time, the slice gradient G
s is applied to perform selective excitation for a predetermined slice. After a predetermined time from the 90 ° excitation, 180 ° excitation by a 180 ° pulse, that is, spin inversion is performed. Also at this time, the slice gradient Gs is applied, and selective inversion is performed for the same slice.

During the period between the 90 ° excitation and the spin inversion, the readout gradient Gr and the phase encode gradient Gp
Is applied. The spin dephase is performed by the readout gradient Gr. The phase encoding of the spin is performed by the phase encoding gradient Gp.

After the spin inversion, the spin is rephased with the readout gradient Gr to generate a spin echo MR.
The signal intensity of the spin echo MR becomes maximum at a point after TE from the 90 ° excitation. The spin echo MR is collected by the data collection unit 150 as view data. Such a pulse sequence is repeated 64 to 512 times in the period TR. Phase encoding gradient Gp for each iteration
And perform different phase encoding each time. As a result, view data of 64 to 512 views filling the k space is obtained.

The pulse sequence used for photographing is G
The method is not limited to the RE method or the SE method.
E (Fast Spin Echo) method, Fast Recovery FSE (Fast Recovery Fast)
Spin Echo method, Echo Planar Imaging (EPI: Echo Planar Imaging)
g) or any other suitable technique.

The data processing unit 170 reconstructs a tomographic image of the object 300 by performing two-dimensional inverse Fourier transform on the view data in the k space. Since the SNR of the view data is good, a high-quality tomographic image can be obtained. The reconstructed image is stored in the memory and displayed on the display unit 180.

FIG. 4 shows a schematic diagram of an electric circuit of the RF coil unit 108. As shown in FIG.
Is a pair of ring elements
t) 802 and a plurality of linear elements (linear)
element 804). Although the number of linear elements is set to four for convenience of illustration, the number is not limited to four and may be an appropriate number.

The ring element 802 is a circular or elliptical closed loop current path constituted by conductors. The linear element 804 is a linear current path formed by a conductor and a capacitor. The conductor and the capacitor are connected in series.

The pair of ring elements 802 are opposed to each other with a predetermined distance therebetween.
2 are interconnected by a plurality of linear elements 804. Thereby, a cage-type RF coil is constituted as a whole. This RF coil is called a birdcage coil due to its shape. The ring element 802 is an example of the embodiment of the ring element in the present invention.
The linear element 804 is an example of an embodiment of the linear element in the present invention.

FIG. 5 schematically shows another type of electric circuit of the RF coil unit 108. In this electric circuit, the ring element 802 is a closed loop current path composed of a series connection of a conductor and a capacitor, and the linear element 804 is a linear current path composed of a conductor.
A birdcage coil having such an electric circuit is called a high-pass type. On the other hand, a birdcage coil having the circuit shown in FIG. 4 is called a low-pass type.

FIG. 6 is an exploded view showing the structure of the main part of the RF coil unit 108. As shown in the figure, the RF coil unit 108 includes a pair of ring holders (ring hol).
der) 810. The pair of ring holders 810 respectively support the pair of ring elements 802. The ring holder 810 is an example of an embodiment of the support plate member in the present invention.

The ring holder 810 is made of a non-magnetic and non-conductive material. Such materials include, for example, plastics and ceramics (ce).
ramics) is used. Being non-magnetic does not affect the static magnetic field, and being non-conductive causes no eddy current to affect the gradient magnetic field.

The ring holder 810 is an annular structure having a through hole corresponding to the shape of the ring element 802, and has a cylindrical portion 812 and a flange portion 814. Tube part 812
A ring element 802 is coaxially supported therein.
The ring element 802 is, for example, a mold (mold).
Thus, it is integrated with the ring holder 810.

The electric circuit of the ring element 802 may be either the ring element of the low-pass type birdcage coil shown in FIG. 4 or the ring element of the high-pass type birdcage coil shown in FIG.

The cylindrical portion 812 is provided with a plurality of grooves 816 reaching the ring element 802 from the outer peripheral surface. The number of grooves 816 is equal to the number of linear elements 804. Here, an example is shown in which the number of grooves 816 and therefore the number of ring elements 804 is four, but the number is not limited thereto and may be an appropriate number. The groove 816 is used to connect the end of the linear element 804 to the ring element 802 as described later.
Used to attach to.

The RF coil unit 108 also has a pair of mounting rings 830. The pair of mounting rings 830 are connected by a pair of girders 832 and face each other at a predetermined distance. The attachment ring 830 and the spar 832 constitute a frame. The part consisting of the mounting ring 830 and the spar 832
It is an example of an embodiment of a mounting frame member in the present invention.

The mounting ring 830 and the spar 832 are made of a non-magnetic and non-conductive material. For example, plastics and ceramics are used as such materials. Being non-magnetic does not affect the static magnetic field, and being non-conductive causes no eddy current to affect the gradient magnetic field.

The spar 832 has an extendable structure.
Thereby, the distance between the mounting rings 830 is variable. The telescopic structure is the same as the telescopic mechanism of the telescope barrel, for example.
It is realized by a structure or the like.

A pair of ring holders 810 are mounted on the pair of mounting rings 830, respectively. The mounting ring 830 has a diameter of the cylindrical portion 812 of the ring holder 810.
And is smaller than the outer diameter of the flange portion 814.

In mounting, the ring holder 81
The flange portion 814 is brought into contact with the mounting ring 830 by passing the 0 cylindrical portion 812 from the side opposite to the spar 832 through the mounting ring 830, and the holes 818 and 838 provided in the flange portion 814 and the mounting ring 830 are used. , And fixed by screws. The screws used are also non-magnetic and non-conductive.

For fixing by screwing, since the ring element 802 can be removed from the mounting ring 830 by removing the screw, it is a detachable fixing means. Note that the ring holder 81 with respect to the mounting ring 830
The fixing of 0 is not limited to screwing, and any other appropriate detachable fixing means may be used.

After the attachment to the attachment ring 830, the linear element 804 is attached to the ring holder 810. The electric circuit of the linear element 804 may be either the linear element of the low-pass birdcage shown in FIG. 4 or the linear element of the high-pass birdcage coil shown in FIG. However, it is necessary to use a ring element 802 supported by the ring holder 810 that matches the type of the ring element 802.

In mounting the linear element 804, both ends are inserted into the grooves 816 of the pair of ring holders 810, and these are pushed in the radial direction as guides, and the ends of the linear element 804 are attached to the ring element 802. Contact the surface. As a result, the pair of ring elements 802 are
4 for electrical connection. The birdcage coil is completed by attaching all the linear elements 804 in the same manner.

FIG. 7 shows an example of the state of attachment of the linear element 804 to the ring element 802. FIG. 17A is a plan view of a part of the ring holder 810 viewed from the end face side of the cylindrical portion 812 of the ring holder 810, and FIG.

As shown in FIG.
Reference numeral 4 indicates that the side surface of the end portion is in contact with the surface of the ring element 802. A wedge 806 is attached to the end of the linear element 804 from the side opposite to the abutment with the ring element 802.
Is applied by using the linear element 804.
And the ring element 802 in a reliable manner.

The wedge 806 also serves as a stopper for the linear element 804 to ensure the structural integrity of the birdcage coil. By removing the wedge 806, the linear element 804 can be removed from the ring holder 810. That is, the linear element 8
04 is detachably fixed to the ring holder 810. Note that the fixing of the linear element 804 is not limited to the wedge, but may be based on other appropriate detachable fixing means.

The linear element 804 is connected to the ring holder 8
10 and a ring holder 81
Since 0 is detachable from the mounting ring 830, a plurality of types of ring holders 810 having ring elements 802 having different diameters can be prepared and appropriately replaced.

That is, (a), (b) and (c) of FIG.
As shown in the figure, three types of ring holders 81 each having a large, medium, and small ring element 802, for example, are shown.
0 is prepared, and an optimal one is selected and used according to the thickness of the arm to be photographed.

As a result, the filling factor of the birdcage coil can be optimized, and an efficient R
F excitation and signal reception with good SNR can be performed. Note that the types of the ring holders 810 are not limited to three types, and may be various types according to the diversification of the diameter of the ring element 802.

A common linear element 804 is used for a plurality of types of ring elements 802. Therefore, one type of linear element 804 may be used regardless of the diameter of the ring element 802.

For this reason, since only a plurality of types of bird cage coils need to be prepared, only the ring holder 810 supporting the ring element 802 is required. Can be greatly saved. This is particularly advantageous in an on-vehicle type magnetic resonance imaging apparatus having a particularly small space margin.

The length of the linear element 804 is variable. The variable length linear element 804 is realized by, for example, a telescopic structure. 9 and 10
FIG. 2 schematically shows the telescopic structure of the linear element 804. FIG. 9 shows a telescopic structure of a linear element 804 for a low-pass birdcage coil,
FIG. 10 shows a telescopic structure of a linear element 804 for a high-pass birdcage coil.

As shown in FIG. 9, the linear element 804 for a low-pass birdcage coil comprises a combination of two coaxial pipes 842 and 852 having different diameters. Both pipes are made of a conductor. For example, copper is used as the conductor, but the conductor is not limited to copper.
Further, their cross-sectional shape is, for example, circular, but is not limited thereto.

A part of the small diameter pipe 852 is nested with respect to the large diameter pipe 842, and the total length of the linear element 804 can be adjusted by changing the length of the nested part.

A spacer 844 is provided inside the edge of the large-diameter pipe 842, and the small-diameter pipe 8
A spacer 854 is provided outside the edge of 52.
By these spacers 844 and 854, the pipe 842 is formed.
And the outer surface of the pipe 852 face each other at a predetermined interval.

The two conductors facing each other at an interval form a capacitor. Since the facing area of both conductors changes due to the expansion and contraction of the linear element 804, the capacitance of the capacitor changes as the linear element 804 expands and contracts.

The capacitance decreases when the linear element 804 is extended, and increases when the linear element 804 is contracted. This is opposite to the increase and decrease of the inductance due to the expansion and contraction of the linear element 804, so that the product of the two is kept constant and the tuning frequency of the birdcage coil is kept constant.

As shown in FIG. 10, the linear element 804 for a high-pass type birdcage coil comprises a combination of two coaxial pipes 862 and 872 having different diameters. Both pipes are made of a conductor. For example, copper is used as the conductor, but the conductor is not limited to copper. Further, their cross-sectional shape is, for example, circular, but is not limited thereto.

A part of the small-diameter pipe 872 is nested with respect to the large-diameter pipe 862, and the entire length of the linear element 804 can be adjusted by changing the length of the nested part. Inner surface of pipe 862 and pipe 87
The outer surfaces of the two contact and form an electrical connection.

The length of the RF coil unit 108 can be adjusted by the expansion and contraction structure of the linear element 804 and the expansion and contraction structure of the spar 832. Thus, the length of the linear element 804 can be changed in accordance with the change in the diameter of the ring element 802, and the ratio between the diameter and the length of the birdcage coil can always be optimized. This makes it possible to optimize RF excitation and improve the SNR of the received signal.

In the above description, the RF coil is a birdcage coil for imaging an arm, but a birdcage for other parts such as a hand, a leg, a head, and a trunk is formed by a similar configuration. It goes without saying that a coil can be realized.

Further, the example in which the RF coil is used for transmitting the RF excitation signal and receiving the magnetic resonance signal has been described.
The F coil may perform only one of the transmission of the RF excitation signal and the reception of the magnetic resonance signal.

[0088]

As described above in detail, according to the present invention, a birdcage type RF coil whose size can be adjusted according to an object, and a magnetic resonance imaging apparatus provided with such an RF coil Can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a pulse sequence executed by the device shown in FIG.

FIG. 3 is a diagram illustrating an example of a pulse sequence executed by the device illustrated in FIG. 1;

FIG. 4 is a schematic diagram showing an electric circuit of a birdcage coil.

FIG. 5 is a schematic diagram showing an electric circuit of a birdcage coil.

FIG. 6 is an exploded view showing a configuration of a main part of the RF coil unit.

FIGS. 7A and 7B are a plan view and a cross-sectional view showing a part of the RF coil unit.

FIG. 8 is a sectional view of a ring holder.

FIG. 9 is a schematic diagram showing a telescopic mechanism of the linear element.

FIG. 10 is a schematic diagram showing a telescopic mechanism of a linear element.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 magnet system 102 main magnetic field coil unit 106 gradient coil unit 108 RF coil unit 130 gradient drive unit 140 RF drive unit 150 data collection unit 160 control unit 170 data processing unit 180 display unit 190 operation unit 300 object 500 cradle 802 ring element 804 linear Element 810 Ring holder 812 Tube section 814 Flange section 816 Groove 830 Mounting ring 832 Digit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Wiswanatan Seshan 127 Gee Yokogawa Medical System Co., Ltd., 4-7 Asahigaoka, Hino City, Tokyo 4C096 AB36 CC05 CC12

Claims (8)

[Claims] 1. A pair of ring elements forming a part of a birdcage type coil, and a pair of support plates respectively supporting the pair of ring elements and having through holes corresponding to the pair of ring elements. A mounting frame member in which the pair of support plate members are detachably mounted with the through holes facing each other and the distance between the pair of support plate members is variable; An RF coil, comprising: a plurality of linear elements of variable length that electrically connect ring elements to each other and form a birdcage coil together with the pair of ring elements. 2. The RF according to claim 1, wherein the pair of support plate members is one of a plurality of pairs of support plate members that respectively support ring elements having different diameters. coil. 3. The RF coil according to claim 1, wherein the support plate member has a plurality of grooves for guiding the ends of the plurality of linear elements to the surface of the ring element, respectively. . 4. The apparatus according to claim 1, wherein said support plate member and said mounting frame member are non-magnetic and non-conductive.
An RF coil according to any one of claims 3 to 4. 5. A magnetic resonance imaging apparatus configured to form an image based on a magnetic resonance signal generated inside a subject using a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field, wherein the forming of the high-frequency magnetic field and the magnetic resonance A pair of ring elements forming a part of a birdcage coil as an RF coil for performing at least one of signal reception; and the pair of ring elements respectively supporting the pair of ring elements. A pair of support plate members each having a through hole corresponding to the distance between the pair of support plate members, the pair of support plate members being detachably mounted with the through holes facing each other; A variable mounting frame member, and a birdcage coil with the pair of ring elements electrically connected to each other and with the pair of ring elements Comprising an RF coil having has a variable plurality of linear elements length constituting a magnetic resonance imaging apparatus characterized by. 6. The magnetic device according to claim 5, wherein the pair of support plate members is one of a plurality of pairs of support plate members that respectively support ring elements having different diameters. Resonance imaging device. 7. The magnetic resonance according to claim 5, wherein the support plate member has a plurality of grooves for respectively guiding ends of the plurality of linear elements to a surface of the ring element. Shooting equipment. 8. The apparatus according to claim 5, wherein said support plate member and said mounting frame member are non-magnetic and non-conductive.
A magnetic resonance imaging apparatus according to claim 1.