JP4180412B2 - Magnetic field forming apparatus and magnetic resonance imaging apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic field forming apparatus and a magnetic resonance imaging apparatus, and more particularly to a magnetic field forming apparatus having a structure in which a pair of magnets facing each other with a gap in the vertical direction are supported by a U-shaped magnet support member. The present invention also relates to a magnetic resonance imaging apparatus including such a magnetic field forming apparatus.
[0002]
[Prior art]
In a magnetic resonance imaging (MRI) apparatus, an object to be imaged is carried into an internal space of a magnet system (namely, an imaging space), and a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field are applied to the inside of the object. Spin is excited to generate a magnetic resonance signal, and an image is reconstructed based on the received signal.
[0003]
One type of magnet system is an open magnet system. The open-type magnet system has a structure in which a pair of magnets facing each other up and down across an imaging space are supported by a U-shaped magnet support member, that is, a yoke. In order to increase the mechanical rigidity of the yoke, a reinforcing member is attached to an inner corner of the U-shaped structure (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
JP 2000-139874 A (page 3-4, Fig. 1-3)
[0005]
[Problems to be solved by the invention]
In the magnet system as described above, since the reinforcing member is attached to the inside of the U-shaped structure, there is a large influence on the magnetic field of the magnet, and there is a spatial restriction, so that a sufficient effect cannot always be obtained.
[0006]
Therefore, an object of the present invention is to realize a magnetic field forming apparatus having excellent mechanical rigidity while using a U-shaped magnet support member, and a magnetic resonance imaging apparatus including such a magnetic field forming apparatus. It is.
[0007]
[Means for Solving the Problems]
(1) One aspect of the invention for solving the above-described problem is that a magnet support member having a vertical limb and a pair of horizontal limbs extending horizontally from both ends of the vertical limb, and the pair of horizontal limbs. A pair of magnets that are supported and opposed to each other with a gap in the vertical direction, and ribs that are provided on the magnet support member from the upper surface of the upper horizontal limb of the pair of horizontal limbs to the back surface of the vertical limbs A magnetic field forming apparatus comprising: a member;
[0008]
(2) In another aspect of the invention for solving the above problems, a magnetic field forming means for forming a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field in a space for receiving an object to be imaged, and the magnetic field forming means An image generation means for generating an image based on the magnetic resonance signals collected through the magnetic resonance imaging apparatus, wherein the magnetic field forming means includes a pair of vertical limbs and a pair of horizontal extensions extending from both ends of the vertical limbs. A magnet support member having a horizontal limb; a pair of magnets respectively supported by the pair of horizontal limbs and opposed to each other at an interval in the vertical direction; and the magnet support member on the upper side of the pair of horizontal limbs. And a rib member provided from the upper surface of the horizontal limb to the back surface of the vertical limb.
[0009]
In the inventions according to the above aspects, since the rib member is provided on the magnet support member from the upper surface of the upper horizontal limb of the pair of horizontal limbs to the back surface of the vertical limb, the U-shaped magnet support member is used. However, a magnetic field forming apparatus having excellent mechanical rigidity can be realized.
[0010]
It is preferable that a plurality of the rib members are provided in parallel in terms of easy rigidity improvement. It is preferable that two rib members are provided in parallel in order to achieve symmetry. It is preferable that the rib member is provided at a position on the inner side by a predetermined distance from the side surface of the magnet support member in terms of loosening the curve of the enclosure covering the outer side.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the magnetic resonance imaging apparatus. This apparatus is an example of an embodiment of the present invention. An example of an embodiment related to the magnetic resonance imaging apparatus of the present invention is shown by the configuration of the apparatus.
[0012]
As shown in the figure, the apparatus has a magnet system 100. The magnet system 100 includes a main magnetic field magnet unit 102, a gradient coil unit 106, and an RF coil unit 108. The main magnetic field magnet unit 102, the gradient coil unit 106, and the RF coil unit 108 are each composed of a pair facing each other across a space. Moreover, all have a substantially disk shape and are arranged sharing a central axis. The magnet system 100 will be described later.
[0013]
The object 1 is mounted on the table 500 and carried into and out of the internal space (bore) of the magnet system 100. The table 500 is driven by the table driving unit 120.
[0014]
The main magnetic field magnet unit 102 forms a static magnetic field in the internal space of the magnet system 100. The direction of the static magnetic field is substantially orthogonal to the body axis direction of the target 1. That is, a so-called vertical magnetic field is formed. The main magnetic field magnet unit 102 is configured using, for example, a permanent magnet. Of course, not only permanent magnets but also superconducting electromagnets or normal conducting electromagnets may be used.
[0015]
The gradient coil section 106 generates three gradient magnetic fields for giving gradients to the static magnetic field strength in the directions of three axes perpendicular to each other, that is, the slice axis, the phase axis, and the frequency axis.
[0016]
The gradient magnetic field in the slice axis direction is also called a slice gradient magnetic field. The gradient magnetic field in the phase axis direction is also called a phase encode gradient magnetic field. The gradient magnetic field in the frequency axis direction is also referred to as a read out gradient magnetic field. In order to make it possible to generate such a gradient magnetic field, the gradient coil unit 106 has three gradient coils (not shown). Hereinafter, the gradient magnetic field is also simply referred to as a gradient.
[0017]
The RF coil unit 108 transmits an RF pulse (radio frequency pulse) for exciting spins in the body of the subject 1 to the static magnetic field space. The RF coil unit 108 also receives a magnetic resonance signal in which excited spin occurs. The RF coil unit 108 may be either one that performs transmission and reception with the same coil or one that performs with separate coils.
[0018]
A gradient driving unit 130 is connected to the gradient coil unit 106. The gradient driving unit 130 gives a driving signal to the gradient coil unit 106 to generate a gradient magnetic field. The gradient drive unit 130 has three systems of drive circuits (not shown) corresponding to the three systems of gradient coils in the gradient coil unit 106.
[0019]
An RF drive unit 140 is connected to the RF coil unit 108. The RF drive unit 140 gives a drive signal to the RF coil unit 108 and transmits an RF pulse to excite spins in the body of the subject 1.
[0020]
A data collection unit 150 is connected to the RF coil unit 108. The data collecting unit 150 takes in the received signal received by the RF coil unit 108 by sampling and collects it as digital data.
[0021]
A control unit 160 is connected to the table driving unit 120, the gradient driving unit 130, the RF driving unit 140, and the data collection unit 150. The control unit 160 controls the table driving unit 120 or the data collection unit 150 to perform shooting.
[0022]
The control unit 160 is configured using, for example, a computer. The controller 160 has a memory (not shown). The memory stores a program for the control unit 160 and various data. The function of the control unit 160 is realized by the computer executing a program stored in the memory.
[0023]
The output side of the data collection unit 150 is connected to the data processing unit 170. Data collected by the data collection unit 150 is input to the data processing unit 170. The data processing unit 170 is configured using, for example, a computer. The data processing unit 170 has a memory (not shown). The memory stores a program for the data processing unit 170 and various data.
[0024]
The data processing unit 170 is connected to the control unit 160. The data processing unit 170 is above the control unit 160 and controls it. The function of this apparatus is realized by the data processing unit 170 executing a program stored in the memory.
[0025]
The data processing unit 170 stores the data collected by the data collection unit 150 in a memory. A data space is formed in the memory. This data space constitutes a two-dimensional Fourier space. Hereinafter, the Fourier space is also referred to as k-space. The data processing unit 170 reconstructs the image of the target 1 by performing two-dimensional inverse Fourier transform on the k-space data. The data processing unit 170 is an example of an embodiment of image generation means in the present invention.
[0026]
A display unit 180 and an operation unit 190 are connected to the data processing unit 170. The display unit 180 is configured by a graphic display or the like. The operation unit 190 includes a keyboard having a pointing device.
[0027]
The display unit 180 displays the reconstructed image and various information output from the data processing unit 170. The operation unit 190 is operated by the user and inputs various commands and information to the data processing unit 170. The user operates the apparatus interactively through the display unit 180 and the operation unit 190.
[0028]
The configuration of the magnet system 100 is shown in FIGS. 2 is a front view, and FIG. 3 is a right side view, both of which show the external appearance of an enclosure of the magnet system 100. 4 is a cross-sectional view taken along the line AA in FIG. Although not shown, the left side view corresponds to a mirror image of that shown in FIG. As shown in these drawings, the magnet system 100 has a base part 112, a support part 114, and a eaves part 116.
[0029]
The upper surface of the base part 112 is a horizontal surface. The support column 114 stands substantially vertically at the back of the base 112 when viewed from the front. The eaves part 116 extends substantially horizontally from the upper part of the column part 114 toward the front. The lower surface of the flange portion 116 faces the upper surface of the base portion 112 with a space therebetween. Such a magnet system has a magnet body inside. The magnet body will be described later.
[0030]
A table 500 on which a subject to be photographed is placed is mounted on the base portion 112 of the magnet system 100. The table 500 is mounted on the base 112 so as to be horizontally long when viewed from the front of the magnet system 100. The surface of the table 500 on which the object to be imaged is mounted is parallel to the upper surface of the base portion 112.
[0031]
The table 500 is mounted on the base 112 as viewed from the front of the magnet system 100. A pair of mounting mechanisms provided between the left and right ends of the base 112 and the lower surface of the table 500 corresponding thereto. 310. The mounting mechanism 310 forms part of the table driving unit 120.
[0032]
The configuration of the mounting mechanism 310 will be described with reference to FIG. As shown in the figure, the mounting mechanism 310 supports the table 500 from below with arms 314. The table 500 is kept slightly lifted from the upper surface of the base 112 as shown.
[0033]
The back part of the arm 314 as viewed from the front of the magnet system 100 is inserted into the cylinder 324 so that it can slide in the horizontal direction. The cylinder 324 is inserted into the cylinder 334 so that it can slide in the horizontal direction. The cylinder 324 is inserted into the cylinder 344 so that it can slide in the horizontal direction. The tube 344 is fixedly attached to the lateral end of the base portion 112 when viewed from the front of the magnet system 100. The figure shows a state in which the arm 314 and each of the tubes 324 and 334 are inserted deepest into the tubes that accommodate them.
[0034]
Inside the cylinders 324, 334, 344, there are provided mechanisms for pushing out and pulling back the inner arms or cylinders using, for example, hydraulic pressure. As a result, the portion composed of the arm 314 and the tubes 324, 334, and 344 becomes an arm that can expand and contract in the horizontal direction as a whole. Hereinafter, a portion composed of the arm 314 and the tubes 324, 334, 344 is also referred to as an extendable arm.
[0035]
FIG. 5 shows a state where the telescopic arm is most extended. As shown in the figure, in this state, the table 500 is completely removed from the space between the base portion 112 and the flange portion 116. That is, the table 500 comes off from the top of the base part 112 and protrudes toward the front from the front of the magnet system 100. For this reason, an object to be photographed can get on and off the table 500 without being obstructed by the flange 116 of the magnet system 100.
[0036]
The table 500 on which the object is placed in the state shown in FIG. 5 is pulled back into the space between the base portion 112 and the flange portion 116 by the shortening operation of the telescopic arm. In the state where the telescopic arm is shortened most, as shown in FIG. 3, the table 500 reaches a fixed position in the space between the base portion 112 and the flange portion 116.
[0037]
6, 7, 8 and 9 show the configuration of the magnet body 110. FIG. 6 is a front view, FIG. 7 is a right side view, FIG. 8 is a top view, and FIG. 9 is a rear view. Although illustration is omitted, the left side view corresponds to a mirror image of that shown in FIG. The magnet body 110 is an example of an embodiment of the magnetic field forming apparatus of the present invention. An example of an embodiment relating to the magnetic field forming apparatus of the present invention is shown by the configuration of the apparatus. The magnet body 110 is also an example of an embodiment of the magnetic field forming means in the present invention.
[0038]
As shown in these drawings, the magnet main body 110 includes an upper magnet portion 111, a lower magnet portion 113, and a yoke 115. The upper magnet part 111 and the lower magnet part 113 are an example of an embodiment of a magnet in the present invention. The yoke 115 is an example of an embodiment of a magnet support member in the present invention.
[0039]
The yoke 115 has a vertical limb 155 and a pair of horizontal limbs 151 and 153 extending horizontally from both ends of the vertical limb 155. That is, the yoke 115 has a substantially U-shape when viewed from the side. The U-shaped yoke 115 has three legs 157 on the lower surface of the lower horizontal limb 153.
[0040]
The upper magnet portion 111 and the lower magnet portion 113 are respectively attached to the lower surface of the upper horizontal limb 151 and the upper surface of the lower horizontal limb 153 of the U-shaped yoke 115 so as to face each other with a space therebetween. ing.
[0041]
Each of the upper magnet part 111 and the lower magnet part 113 has a substantially short cylindrical shape with two layers. Each of the upper magnet unit 111 and the lower magnet unit 113 includes the main magnetic field magnet unit 102, the gradient coil unit 106, and the RF coil unit 108 described above.
[0042]
The yoke 115 is provided with a rib 159 from the upper surface of the horizontal limb 151 to the rear surface of the vertical limb 155. As a material of the rib 159, for example, steel or the like is used. The rib 159 has a key shape that is bent at a right angle, and conforms to the shape of the corner of the U-shaped yoke 115. Such a rib 159 is integrated with the yoke 115 by screwing or the like, for example. The rib 159 is an example of an embodiment of a rib member in the present invention.
[0043]
Two ribs 159 are attached in parallel to each other. The two ribs 159 are attached so as to be located at a predetermined distance from both sides of the yoke 115. As a result, the pair of ribs 159 are symmetric with respect to the midline of the U-shaped yoke 115. Note that the number of ribs is not limited to two and may be more than that. Or it is good also as a single rib. In the case of a single rib, it is attached on the midline of the U-shaped yoke 115.
[0044]
The rib 159 serves as a reinforcing member for the U-shaped yoke 115. As a result, the U-shaped yoke 115 has high mechanical rigidity. Since the reinforcing member is provided outside the U-shaped yoke 115, the influence on the magnetic field formed inside the U-shaped yoke 115 is small. Further, compared with the conventional case where the U-shaped yoke 115 is provided inside, there are far fewer restrictions in terms of magnetic and spatial conditions. For this reason, the freedom degree of the rib design for implement | achieving desired rigidity is high.
[0045]
The horizontal limb 151 of the U-shaped yoke 115, the horizontal part of the rib 159, and the upper magnet part 111 are in the collar part 116 of the magnet system 100. The vertical portions of the U-shaped yoke's vertical limb 155 and rib 159 are in the column 114 of the magnet system 100. The U-shaped horizontal limb 153 of the yoke, the lower magnet part 113 and the leg part 157 are in the base part 112 of the magnet system 100. As a result, the space where the base portion 112 and the flange portion 116 face each other is a space where a magnetic field is formed by the main magnetic field magnet portion 102, the gradient coil portion 106, and the RF coil portion 108.
[0046]
As described above, when the magnet main body 110 is covered with the enclosure, the rib 159 can be used as an attachment portion of the enclosure, and a dedicated attachment portion can be eliminated. At that time, since the two ribs 159 are attached so as to be located at a predetermined distance from both sides of the yoke 115, as shown in FIG. 9, the curve of the corner of the enclosure can be made gentle. Can enhance the aesthetics of the enclosure.
[0047]
Further, the space between the two ribs 159 on the back surface of the yoke 115 can be used as a space for accommodating an electric circuit unit (unit) for the gradient coil unit 106 and the RF coil unit 108.
[0048]
Furthermore, the lower end of the rib 159 can be used as a force application point when the magnet body 110 is jacked up, and a dedicated adapter or the like that has been indispensable in the past is not necessary.
[0049]
FIG. 10 shows an example of a pulse sequence used for magnetic resonance imaging. This pulse sequence is a pulse sequence of a spin echo (SE: Spin Echo) method.
[0050]
That is, (1) is a sequence of 90 ° pulses and 180 ° pulses for RF excitation in the SE method, and (2), (3), (4) and (5) are respectively the slice gradient Gs and the lead. This is a sequence of an out gradient Gr, a phase encode gradient Gp, and a spin echo MR. The 90 ° pulse and the 180 ° pulse are represented by center signals. The pulse sequence proceeds from left to right along the time axis t.
[0051]
As shown in the figure, 90 ° excitation of spin is performed by a 90 ° pulse. At this time, the slice gradient Gs is applied, and selective excitation for a predetermined slice is performed. After a predetermined time from the 90 ° excitation, 180 ° excitation by a 180 ° pulse, that is, spin inversion is performed. At this time, the slice gradient Gs is applied, and selective inversion is performed for the same slice.
[0052]
In the period between 90 ° excitation and spin reversal, a readout gradient Gr and a phase encode gradient Gp are applied. Spin dephase is performed by the lead-out gradient Gr. Spin phase encoding is performed by the phase encoding gradient Gp.
[0053]
After the spin inversion, the spin is rephased at the readout gradient Gr to generate the spin echo MR. The spin echo MR is collected as view data by the data collecting unit 150. Such a pulse sequence is repeated 64 to 512 times with a period TR (repetition time). The phase encoding gradient Gp is changed every time it is repeated, and a different phase encoding is performed each time. Thereby, view data of 64 to 512 views is obtained.
[0054]
Another example of a magnetic resonance imaging pulse sequence is shown in FIG. This pulse sequence is a pulse sequence of a gradient echo (GRE) method.
[0055]
That is, (1) is a sequence of α ° pulses for RF excitation in the GRE method, and (2), (3), (4) and (5) are respectively slice gradient Gs, readout gradient Gr, It is a sequence of a phase encoding gradient Gp and a spin echo MR. The α ° pulse is represented by a center signal. The pulse sequence proceeds from left to right along the time axis t.
[0056]
As shown in the figure, the α ° excitation of the spin is performed by the α ° pulse. α is 90 or less. At this time, the slice gradient Gs is applied, and selective excitation for a predetermined slice is performed.
[0057]
After the α ° excitation, spin phase encoding is performed by the phase encoding gradient Gp. Next, the spin is first dephased by the readout gradient Gr, and then the spin is rephased to generate a gradient echo MR. The gradient echo MR is collected as view data by the data collection unit 150. Such a pulse sequence is repeated 64 to 512 times with a period TR. The phase encoding gradient Gp is changed every time it is repeated, and a different phase encoding is performed each time. Thereby, view data of 64 to 512 views is obtained.
[0058]
View data obtained by the pulse sequence of FIG. 10 or FIG. 11 is collected in the memory of the data processing unit 170. Note that the pulse sequence is not limited to the SE method or the GRE method, and may be of any other appropriate technique such as the Fast Spin Echo (FSE) method or Echo Planar Imaging (EPI). Needless to say. The data processing unit 170 reconstructs an image based on the view data collected in the memory.
[0059]
Since the mechanical rigidity of the magnet body 110 is large due to the reinforcement by the rib 159, the magnet body 110 does not resonate due to floor vibration or the like. For this reason, image quality deterioration due to magnetic field fluctuations due to vibration of the magnet body 110 does not occur.
[0060]
【The invention's effect】
As described above in detail, according to the present invention, a magnetic field forming device having excellent mechanical rigidity while using a U-shaped magnet support member, and a magnetic resonance apparatus including such a magnetic field forming device. An imaging device can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram of an exemplary apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a magnet system.
FIG. 3 is a diagram showing a configuration of a magnet system.
4 is a cross-sectional view taken along the line AA in FIG.
FIG. 5 is a diagram showing a table push-out state.
FIG. 6 is a diagram showing a configuration of a magnet body.
FIG. 7 is a diagram showing a configuration of a magnet body.
FIG. 8 is a diagram showing a configuration of a magnet body.
FIG. 9 is a diagram showing a configuration of a magnet body.
FIG. 10 is a diagram showing a pulse sequence of imaging.
FIG. 11 is a diagram showing a pulse sequence of imaging.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Target 100 Magnet system 102 Main magnetic field magnet part 106 Gradient coil part 108 RF coil part 120 Table drive part 130 Gradient drive part 140 RF drive part 150 Data collection part 160 Control part 170 Data processing part 180 Display part 190 Operation part 500 Table 112 Base part 114 Supporting part 116 Hook part 310 Mounting mechanism 110 Magnet body 115 Yoke 151, 153 Horizontal limb 155 Vertical limb 111 Upper magnet part 113 Lower magnet part 159 Rib

Claims (6)

A magnet support member having a vertical limb and a pair of horizontal limbs extending horizontally from both ends of the vertical limb;
A pair of magnets respectively supported by the pair of horizontal limbs and facing each other at an interval in the vertical direction;
The magnet support member, comprising an upper rib members kicked set over the back of the vertical limb the upper face of the horizontal limb of the horizontal limb of said pair,
The rib member is magnetic field generating apparatus according to claim Rukoto provided a plurality of parallel. Before SL rib members are provided in parallel two,
The magnetic field forming apparatus according to claim 1 . The rib member is provided at an inner position by a predetermined distance from the side surface of the magnet support member .
The magnetic field forming apparatus according to claim 1 or 2, wherein A magnetic field forming means for forming a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field in the space having a space for receiving an object to be imaged;
Image generating means for generating an image based on magnetic resonance signals collected through the magnetic field forming means, and a magnetic resonance imaging apparatus comprising:
The magnetic field forming means includes
A magnet support member having a vertical limb and a pair of horizontal limbs extending horizontally from both ends of the vertical limb;
A pair of magnets respectively supported by the pair of horizontal limbs and facing each other at an interval in the vertical direction;
The magnet support member includes a rib member provided from the upper surface of the upper horizontal limb of the pair of horizontal limbs to the back surface of the vertical limb,
A plurality of the rib members are provided in parallel ;
A magnetic resonance imaging apparatus. Two rib members are provided in parallel.
The magnetic resonance imaging apparatus according to claim 4 . The rib member is provided at a position inside by a predetermined distance from the side surface of the magnet support member .
6. The magnetic resonance imaging apparatus according to claim 4, wherein the magnetic resonance imaging apparatus is a magnetic resonance imaging apparatus.

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