JP4002805B2 - Coil assembly, magnetic field forming apparatus, and magnetic resonance imaging apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coil assembly, a magnetic field forming apparatus, and a magnetic resonance imaging apparatus, and in particular, a coil assembly provided between a pair of magnets facing each other, and a magnetic field forming apparatus including such a coil assembly. 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, and a spin field within the object is applied by applying a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field. An image is reconstructed based on the magnetic resonance signal that is excited and generates spin.
[0003]
One type of magnet system is a vertical magnetic field type magnet system. This type of magnet system has a pair of magnets facing each other up and down across an imaging space. Each of the pair of magnets has a gradient coil (coil) on each end face facing each other. These gradient coils are also opposed to each other up and down across the imaging space.
[0004]
The gradient coil imparts a gradient to the static magnetic field. The gradients are given in three directions perpendicular to each other. Three lines of coils are used to provide gradients in three directions. Each coil is composed of a conductor that draws a loop in a predetermined pattern. Each conductor draws a loop in the plane.
[0005]
The three loops are enclosed in layers in a plate-like structure made of an insulating material to form an integral coil assembly. Such a pair of coil assemblies is attached to the end faces of the pair of magnets.
[0006]
[Problems to be solved by the invention]
A current is supplied to the gradient coil to generate a gradient magnetic field. Since the gradient coil is in a static magnetic field, a force due to the interaction between current and magnetic flux is applied to the loop. This force is also referred to as Lorentz force. Since the current for generating the gradient magnetic field is supplied in a pulse manner, the Lorentz force also acts in a pulse manner. This force acts in opposite directions on the forward and return paths of the current in the loop. That is, it acts in a direction in which the outward path and the return path are brought closer to each other or away from each other.
[0007]
In the gradient coil having the above-described structure, the upper layer or the lower layer loop is offset upward or downward from the center surface of the thickness of the plate-like structure. Work to bend. For this reason, the plate-like structure vibrates in the thickness direction and generates sound.
[0008]
Accordingly, an object of the present invention is to provide a coil assembly that hardly generates sound even when a force due to an interaction between current and magnetic flux is applied, a magnetic field forming device including such a coil assembly, and such a magnetic field forming device. To achieve a magnetic resonance imaging apparatus.
[0009]
[Means for Solving the Problems]
(1) In one aspect of the invention for solving the above-described problem, a pair of flat first plates facing each other with a space therebetween, and a space between the pair of first plates facing each other A pair of flat second plates, a pair of flat third plates facing each other with a gap between the pair of second plates, and a second thickness of the pair of first plates A pair of flat first coils encapsulated in positions corresponding to the dividing plane, and a pair of flat pairs encapsulated in positions corresponding to the bisector of the thickness among the pair of second plates, respectively. A coil comprising: a second coil; and a pair of flat third coils each enclosed in a position corresponding to a bisector of thickness among the pair of third plates It is an aggregate.
[0010]
(2) In another aspect of the invention for solving the above-described problem, a pair of magnets facing each other with a gap therebetween and a pair of flat firsts facing each other with a gap between the pair of magnets. A pair of flat second plates facing each other with a gap between the pair of first plates, and a pair of flat thirds facing each other with a gap between the pair of second plates A pair of flat first coils enclosed in positions corresponding to a bisector of the thickness of the pair of first plates, and a thickness of the pair of second plates A pair of flat second coils respectively enclosed in a position corresponding to the bisector, and a flat enclosed in a position corresponding to the bisector of the thickness among the pair of third plates. A pair of third coils, and a magnetic field forming device characterized by comprising: That.
[0011]
(3) In another aspect of the invention for solving the above-described problem, a signal acquisition means for acquiring a magnetic resonance signal by applying a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field to a subject to be imaged, and the magnetic resonance signal An image generation unit configured to generate an image based on the magnetic resonance imaging apparatus, wherein the signal acquisition unit includes at least a pair of magnets facing each other with a gap therebetween, and a gap between the pair of magnets. A pair of flat first plates facing each other, a pair of flat second plates facing each other with a space between the pair of first plates, and a space between the pair of second plates. A pair of flat third plates opposed to each other, a pair of flat first coils enclosed in positions corresponding to a bisector of the thickness among the pair of first plates, Thickness in a pair of second plates A pair of flat second coils encapsulated in a position corresponding to a bisector, and a flat encapsulated in a position corresponding to a bisector of thickness in the pair of third plates, respectively. A magnetic resonance imaging apparatus comprising: a pair of third coils.
[0012]
In the invention according to each aspect described in (1) to (3), in each pair, a flat coil is enclosed in a position corresponding to a bisector of thickness in each pair of plates. Therefore, even if forces in opposite directions act on the forward and return paths of the coil loop, they work along the bisector of thickness. For this reason, a board is hard to bend and the sound by vibration is hard to generate | occur | produce.
[0013]
In the pair of first plates, the pair of second plates, and the pair of third plates, one plate and the other plate in the pair are laminated via a vibration absorbing member, respectively. It is preferable in that the sound is further hardly generated.
[0014]
The pair of first coils, the pair of second coils, and the pair of third coils form magnetic fields having gradients in three directions perpendicular to each other in a space between the pair of third plates; This is preferable in that the three-dimensional coordinates can be identified by the magnetic field strength.
[0015]
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 relating to the apparatus of the present invention is shown by the configuration of the apparatus.
[0016]
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 the central axis. The magnet system 100 will be described later.
[0017]
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.
[0018]
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. In addition, you may comprise using not only a permanent magnet but a superconductive electromagnet or a normal electromagnet.
[0019]
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.
[0020]
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 described later. Hereinafter, the gradient magnetic field is also simply referred to as a gradient.
[0021]
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.
[0022]
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.
[0023]
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.
[0024]
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.
[0025]
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. A portion including the magnet system 100, the table driving unit 120, the gradient driving unit 130, the RF driving unit 140, the data collecting unit 150, and the control unit 160 is an example of an embodiment of a signal acquisition unit in the present invention.
[0026]
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.
[0027]
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.
[0028]
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.
[0029]
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.
[0030]
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.
[0031]
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.
[0032]
FIG. 2 shows an example of a pulse sequence used for magnetic resonance imaging. This pulse sequence is a pulse sequence of the spin echo (SE: SpinEcho) method.
[0033]
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.
[0034]
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.
[0035]
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.
[0036]
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.
[0037]
Another example of a pulse sequence for magnetic resonance imaging is shown in FIG. This pulse sequence is a pulse sequence of a gradient echo (GRE) method.
[0038]
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.
[0039]
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.
[0040]
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.
[0041]
View data obtained by the pulse sequence of FIG. 2 or 3 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. For example, the pulse sequence may be one of other appropriate techniques such as a fast spin echo (FSE) method and an echo planar imaging (EPI). Needless to say, it is good. The data processing unit 170 reconstructs an image based on the view data collected in the memory.
[0042]
An example of the configuration of the magnet system 100 is schematically shown in FIGS. 4 is a front view, FIG. 5 is a right side view, and FIG. 6 is an AA cross section of FIG. Although not shown, the left side view corresponds to the mirror image 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.
[0043]
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 110 described later.
[0044]
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 portion 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.
[0045]
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.
[0046]
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.
[0047]
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.
[0048]
Inside the cylinders 324, 334, and 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.
[0049]
FIG. 7 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.
[0050]
The table 500 on which the object is placed in the state shown in FIG. 7 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 the most, as shown in FIG. 5, the table 500 reaches a fixed position in the space between the base portion 112 and the flange portion 116.
[0051]
8 and 9 schematically show the configuration of the magnet body 110. FIG. 8 is a front view, and FIG. 9 is a right side view. Although not shown, the left side view is a view corresponding to the mirror image shown in FIG. The magnet body 110 is an example of an embodiment of the present invention. An example of an embodiment relating to the apparatus of the present invention is shown by the configuration of the apparatus.
[0052]
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 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 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. The vertical limbs 155 may be a plurality of (for example, two) pillars parallel to each other.
[0053]
Both the upper magnet part 111 and the lower magnet part 113 have a substantially short cylindrical shape. 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. The relationship among the main magnetic field magnet unit 102, the gradient coil unit 106, and the RF coil unit 108 will be described later.
[0054]
The horizontal limb 151 of the U-shaped yoke and the upper magnet part 111 are in the collar part 116 of the magnet system 100. The U-shaped yoke vertical limb 155 is in the support column 114 of the magnet system 100. The U-shaped yoke horizontal limb 153 and the lower magnet part 113 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.
[0055]
When the three directions perpendicular to each other in the three-dimensional space are x, y, and z, the z direction is the direction of the magnetic field here. Further, the direction facing the front of the magnet system 100 is defined as the y direction. Therefore, the direction of the body axis of the target 1 placed on the table 500 is the x direction.
[0056]
FIG. 10 shows a BB cross section of FIG. This figure shows the relationship among the main magnetic field magnet unit 102, the gradient coil unit 106, and the RF coil unit 108. As shown in the figure, each of the upper magnet unit 111 and the lower magnet unit 113 includes a main magnetic field magnet unit 102, a gradient coil unit 106, and an RF coil unit 108.
[0057]
The main magnetic field magnet unit 102 includes a magnet 501. The magnet 501 has a pole piece 503 on the magnetic pole surface. The outer shape of the part composed of the magnet 501 and the pole piece 503 has a short cylindrical shape as a whole. The upper magnet part 111 and the lower magnet part 113 are in a relationship in which the pole pieces 503 face each other. A pair of magnets 501 facing each other is an example of an embodiment of a pair of magnets in the present invention.
[0058]
The peripheral edge of the pole piece 503 projects to the opposite side of the magnet 501. A gradient coil portion 106 and an RF coil portion 108 are provided in a space formed inside the protruding peripheral edge portion. Hereinafter, this space is also referred to as a recess.
[0059]
The gradient coil unit 106 and the RF coil unit 108 are disposed such that the gradient coil unit 106 is on the bottom side of the recess and the RF coil unit 108 is on the opening side of the recess. That is, the gradient coil unit 106 and the RF coil unit 108 are arranged in a static magnetic field generated by the magnet 501. The outer shape of each of the gradient coil unit 106 and the RF coil unit 108 is a disc shape.
[0060]
FIG. 11 schematically illustrates the configuration of the gradient coil unit 106. The gradient coil unit 106 is an example of an embodiment of a coil assembly of the present invention. An example of an embodiment relating to the apparatus of the present invention is shown by the configuration of the apparatus.
[0061]
As shown in the figure, the gradient coil unit 106 includes an X coil 601, a Y coil 603, and a Z coil 605. The X coil 601, the Y coil 603, and the Z coil 605 all have a disk-shaped outer shape.
[0062]
These coils are, for example, three-tiered with a Y coil 603 interposed therebetween. And regarding the recessed part of the pole piece 503, the X coil 601 is an opening side, and the Z coil 605 is a bottom side. Note that the order of overlapping of these three coils is not limited to the illustrated example, and may be appropriate. The three coils may be directly stacked, or may be stacked with an interval of, for example, several millimeters. The interval is maintained by an appropriate spacer.
[0063]
Each coil is composed of a disk-shaped plate and a coil pattern enclosed therein. The coil pattern is a flat pattern. The conductor constituting the flat pattern is enclosed at a position corresponding to the bisector of the disk-shaped plate. These positions are indicated by alternate long and short dash lines for each plate.
[0064]
FIG. 12 schematically shows the configuration of the X coil 601. (A) of the same figure is a top view, (b) is CC sectional drawing. As shown in the figure, the X coil 601 is composed of a plate 611 and a coil pattern 613 enclosed therein. The plate 611 is made of an insulating material. The coil pattern 613 is composed of a conductor. The center of the conductor constituting the coil pattern 613 is at a position corresponding to the bisector of the plate 611. The plate 611 is an example of an embodiment of the third plate in the present invention. The coil pattern 613 is an example of an embodiment of a third coil in the present invention.
[0065]
The coil pattern 613 is a pair of symmetrical patterns with respect to the center line of the plate 611 in the y direction. Each pattern consists of a plurality of half-moon loops. A current that circulates in the same direction flows in each loop. The current is supplied from the gradient driver 130. A straight line portion of the loop is a main path 615, and an arc portion is a return path 617. The current flowing through the main path 615 contributes to the generation of a gradient magnetic field in the x direction.
[0066]
In such a loop, a current flows with a polarity as shown in FIG. When such a current flows, Lorentz force acts on the coil pattern 613. The direction of force is indicated by an arrow. That is, a force that tries to bring them closer to each other acts on the main path 615 and the return path 617. This force is intended to compress the plate 611 in a direction parallel to the plate surface. If the polarity of the current is reversed, the direction of the force is reversed. In that case, a tensile force is generated.
[0067]
Since the conductor constituting the coil pattern 613 is located at the center corresponding to the bisector of the thickness of the plate 611, the force acts along the bisector of the thickness of the plate 611. For this reason, this force does not act to bend the plate 611. However, the condition is that the plate 611 can withstand this compressive force, but it is easy to satisfy such a condition. Since the Lorentz force does not act to bend the plate 611, the amount of generated sound is greatly reduced even when the force is applied in a pulsed manner.
[0068]
FIG. 13 schematically shows the configuration of the Y coil 603. (A) of the same figure is a top view, (b) is DD sectional drawing. As shown in the figure, the Y coil 603 includes a plate 631 and a coil pattern 633 encapsulated therein. The plate 631 is made of an insulating material. The coil pattern 633 is made of a conductor. The center of the conductor constituting the coil pattern 633 is at a position corresponding to the bisector of the plate 631. The plate 631 is an example of an embodiment of the second plate in the present invention. The coil pattern 633 is an example of an embodiment of the second coil in the present invention.
[0069]
The coil pattern 633 is a pair of patterns symmetrical about the center line of the plate 631 in the x direction. Each pattern consists of a plurality of half-moon shaped loops. A current that circulates in the same direction flows in each loop. The current is supplied from the gradient driver 130. The straight line portion of the loop is the main path 635, and the arc portion is the return path 637. The current flowing through the main path 635 contributes to the generation of a gradient magnetic field in the y direction.
[0070]
In such a loop, a current flows with a polarity as shown in FIG. When such a current flows, Lorentz force acts on the coil pattern 633. The direction of force is indicated by an arrow. That is, a force is applied to the main path 635 and the return path 637 so as to bring them closer to each other. This force is intended to compress the plate 631 in a direction parallel to the plate surface. If the polarity of the current is reversed, the direction of the force is reversed. In that case, a tensile force is generated.
[0071]
Since the center of the conductor constituting the coil pattern 633 is at a position corresponding to the bisector of the thickness of the plate 631, the force acts along the bisector of the thickness of the plate 631. For this reason, this force does not act to bend the plate 631. However, although it is a condition that the plate 631 can withstand this compressive force, it is easy to satisfy such a condition. Since the Lorentz force does not act to bend the plate 631, even if the force is applied in a pulse manner, the amount of generated sound is greatly reduced.
[0072]
FIG. 14 schematically shows the configuration of the Z coil 605. (A) of the same figure is a top view, (b) is EE sectional drawing. As shown in the figure, the Z coil 605 includes a plate 651 and a coil pattern 653 enclosed therein. The plate 651 is made of an insulating material. The coil pattern 653 is made of a conductor. The center of the conductor constituting the coil pattern 653 is at a position corresponding to the bisector of the plate 651. The plate 651 is an example of an embodiment of the first plate in the present invention. The coil pattern 653 is an example of an embodiment of the first coil in the present invention.
[0073]
The coil pattern 653 includes a plurality of concentric loops. The center of the concentric circle coincides with the center of the plate 651. A current that circulates in the same direction flows in each loop. The current is supplied from the gradient driver 130.
[0074]
In such a loop, a current flows with a polarity as shown in FIG. When such a current flows, Lorentz force acts on the coil pattern 653. The direction of force is indicated by an arrow. This force is intended to compress the plate 651 in a direction parallel to the plate surface. If the polarity of the current is reversed, the direction of the force is reversed. In that case, a tensile force is generated.
[0075]
Since the conductor of the coil pattern 653 has a center at a position corresponding to the bisector of the thickness of the plate 651, the force acts along the bisector of the thickness of the plate 651. For this reason, this force does not act to bend the plate 651. However, the condition is that the plate 651 can withstand this compressive force, but it is easy to satisfy such a condition. Since the Lorentz force does not act to bend the plate 651, the amount of sound generated is greatly reduced even when the force is applied in a pulsed manner.
[0076]
Thus, all of the Lorentz forces generated in the X coil 601, Y coil 603, and Z coil 605 constituting the gradient coil section 106 do not act to bend them. For this reason, the gradient coil unit 106 is less likely to generate sound when a gradient magnetic field is generated.
[0077]
For example, as shown in FIG. 15, the gradient coil unit 106 may be provided with a vibration absorbing member 701 between three stacked stages. The vibration absorbing member 701 is an example of an embodiment of the vibration absorbing member in the present invention. As the vibration absorbing member 701, for example, an appropriate material such as a foam material or rubber is used. By doing in this way, the vibration of the gradient coil part 106 can be suppressed and it can make it difficult to generate a sound.
[0078]
【The invention's effect】
As described above in detail, according to the present invention, a coil assembly that hardly generates sound even when a force due to an interaction between current and magnetic flux is applied, a magnetic field forming device including such a coil assembly, and A magnetic resonance imaging apparatus including such a magnetic field forming apparatus 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 pulse sequence of imaging.
FIG. 3 is a diagram showing a pulse sequence of imaging.
FIG. 4 is a diagram showing a configuration of a magnet system.
FIG. 5 is a diagram showing a configuration of a magnet system.
6 is a view showing an AA cross section in FIG. 4. FIG.
FIG. 7 is a diagram showing a table push-out state.
FIG. 8 is a diagram showing a configuration of a magnet body.
FIG. 9 is a diagram showing a configuration of a magnet body.
10 is a diagram showing a BB cross section of FIG. 9;
FIG. 11 is a diagram showing a configuration of a gradient coil section.
FIG. 12 is a diagram showing a configuration of an X coil.
FIG. 13 is a diagram showing a configuration of a Y coil.
FIG. 14 is a diagram showing a configuration of a Z coil.
FIG. 15 is a diagram showing a configuration of a gradient coil section.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 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 110 Magnet main body 111 Upper magnet part 113 Lower magnet part 115 Yoke 601 X coil 603 Y coil 605 Z coil 611, 631, 651 Plate 613, 633, 653 Coil pattern 615, 635 Main path 617, 637 Return path 701 Vibration absorbing member

Claims (9)

A pair of flat first plates facing each other at an interval;
A pair of flat second plates facing each other with a gap between the pair of first plates;
A pair of flat third plates facing each other with a gap between the pair of second plates;
A pair of flat first coils each enclosed in a position corresponding to a bisector of thickness among the pair of first plates;
A pair of flat second coils each enclosed in a position corresponding to a bisector of thickness among the pair of second plates;
A pair of flat third coils each enclosed in a position corresponding to a bisector of thickness among the pair of third plates;
A coil assembly comprising: In the pair of first plates, the pair of second plates, and the pair of third plates, one plate in the pair and the other plate are laminated via a vibration absorbing member, respectively.
The coil assembly according to claim 1. The pair of first coils, the pair of second coils, and the pair of third coils form magnetic fields having gradients in three directions perpendicular to each other in a space between the pair of third plates;
The coil assembly according to claim 1 or 2, characterized in that A pair of magnets facing each other at an interval;
A pair of flat first plates facing each other with a gap between the pair of magnets;
A pair of flat second plates facing each other with a gap between the pair of first plates;
A pair of flat third plates facing each other with a gap between the pair of second plates;
A pair of flat first coils each enclosed in a position corresponding to a bisector of thickness among the pair of first plates;
A pair of flat second coils each enclosed in a position corresponding to a bisector of thickness among the pair of second plates;
A pair of flat third coils each enclosed in a position corresponding to a bisector of thickness among the pair of third plates;
A magnetic field forming apparatus comprising: In the pair of first plates, the pair of second plates, and the pair of third plates, one plate in the pair and the other plate are laminated via a vibration absorbing member, respectively.
The magnetic field forming apparatus according to claim 4. The pair of first coils, the pair of second coils, and the pair of third coils form magnetic fields having gradients in three directions perpendicular to each other in a space between the pair of third plates;
6. The magnetic field forming apparatus according to claim 4 or 5, wherein A signal acquisition means for acquiring a magnetic resonance signal by applying a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field to an imaging target;
Image generating means for generating an image based on the magnetic resonance signal;
A magnetic resonance imaging apparatus comprising:
The signal acquisition means is at least:
A pair of magnets facing each other at an interval;
A pair of flat first plates facing each other with a gap between the pair of magnets;
A pair of flat second plates facing each other with a gap between the pair of first plates;
A pair of flat third plates facing each other with a gap between the pair of second plates;
A pair of flat first coils each enclosed in a position corresponding to a bisector of thickness among the pair of first plates;
A pair of flat second coils each enclosed in a position corresponding to a bisector of thickness among the pair of second plates;
A pair of flat third coils each enclosed in a position corresponding to a bisector of thickness among the pair of third plates;
A magnetic resonance imaging apparatus comprising: In the pair of first plates, the pair of second plates, and the pair of third plates, one plate in the pair and the other plate are laminated via a vibration absorbing member, respectively.
The magnetic resonance imaging apparatus according to claim 7. The pair of first coils, the pair of second coils, and the pair of third coils form magnetic fields having gradients in three directions perpendicular to each other in a space between the pair of third plates;
The magnetic resonance imaging apparatus according to claim 7 or 8, wherein

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