JP3273650B2 - Magnetic resonance imaging equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance imaging apparatus, and more particularly, to a magnetic resonance imaging apparatus having a cooling unit capable of cooling a gradient coil.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional magnetic resonance imaging apparatus. As shown in the figure, the magnetic resonance imaging apparatus includes a magnet 2 capable of applying a static magnetic field of a predetermined intensity to a subject 1 and a predetermined gradient magnetic field superimposed on the static magnetic field along the x, y, and z directions. The apparatus includes a gradient coil 3 that can be applied and an RF coil 4 that can transmit a high-frequency pulse to the subject 1 and receive an MR signal from inside the subject 1.

The gradient magnetic field coil 3 is arranged inside a cylindrical magnet 2 and has a cylindrical shape so that the RF coil 4 and the subject 1 can be arranged inside.

FIG. 7 is a sectional view showing a part of a longitudinal section of the gradient coil 3.

As can be seen from FIG.
Is laminated with an x-direction coil conductor 11, a y-direction coil conductor 12, and a z-direction coil conductor 13 that can apply a gradient magnetic field along the x, y, and z directions, respectively. The pulse current flows independently. These coil conductors 11, 12, 13 are formed integrally with each other using a predetermined resin 14, so that the coil conductors do not move due to electromagnetic force.

[0006] A cooling tube 15 is further embedded in the resin 14, and a predetermined refrigerant is passed through the cooling tube 15 to suppress heat generation of the coil conductors 11, 12, and 13.

[0007]

Here, in order to integrate the coil conductors 11, 12, and 13 with the cooling tube 15, it is necessary to spread the resin 14 over all gaps formed between the coil conductors and the like. There is. On the other hand, each of the coil conductors 11, 12, and 13 has a very complicated shape, and the path through which the resin 14 flows is complicated.

Therefore, as a resin for integration, it is necessary to use a resin 14 that is easily fluidized, that is, has low viscosity.

However, a resin having a low viscosity generally has low strength, and cracks may be generated by shrinkage immediately after molding or by the action of an electromagnetic force.

FIG. 8 shows a state in which a crack 21 has entered the resin 14 of the gradient coil 3.

Here, since the cooling tube 15 is usually formed of vinyl, Teflon, nylon or the like, if the crack reaches the cooling tube 15, the cooling tube 15 is also cracked and passes through the inside. There was a possibility that the refrigerant leaked out.

In addition, a resin having a low viscosity generally has a low thermal conductivity, so that the cooling efficiency is deteriorated, and it is necessary to arrange a cooling tube in a complicated manner, and the coolant supply device must be large.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to prevent refrigerant from flowing out due to cracks in a cooling tube of a gradient coil and to improve the cooling efficiency of the gradient coil. It is an object of the present invention to provide a magnetic resonance imaging apparatus capable of performing the above.

[0014]

According to one aspect of the present invention, there is provided a magnetic resonance imaging apparatus comprising: a magnet capable of applying a predetermined static magnetic field to a subject; And a gradient magnetic field coil capable of applying a predetermined gradient magnetic field over the magnetic field, wherein the gradient magnetic field coil includes a coil conductor capable of generating a gradient magnetic field, including a first resin. First
A coil portion embedded in the filler and a cooling tube for passing a cooling medium for cooling the coil conductor are formed in a second filler formed by including a second resin mixed with a predetermined mixing material. And a cooling section embedded in the base member. In this configuration, the mixed material is
It is desirable that the mixed material has a higher thermal conductivity than the second resin. Preferably, the first and second resins are both epoxy resins, and the mixed material is any one of silica powder, glass fiber, and aluminum oxide powder. More preferably, a crack blocking member for blocking the progress of cracks is interposed between the coil section and the cooling section. In this case, it is preferable that the crack blocking member is formed of glass fiber reinforced plastic. The cooling tube is formed in a spiral shape, for example. Further, according to another aspect of the magnetic resonance imaging apparatus of the present invention, in the above-described equivalent configuration, particularly, the gradient magnetic field coil includes a main coil conductor capable of generating a gradient magnetic field, including the first resin. A main coil portion embedded in the formed first filler, and a shield coil conductor capable of generating a shield magnetic field capable of canceling the gradient magnetic field in an external region of the gradient magnetic field coil, including the first resin. A shield coil portion embedded in a separate first filler material formed by the above, and a cooling tube for passing a coolant for cooling the coil conductor, including a second resin mixed with a predetermined mixing material. The cooling part embedded in the second filler formed by the above is fixedly formed to each other. Also in this case, it is desirable that the mixed material is a mixed material having a higher thermal conductivity than the second resin.

[0015]

According to the magnetic resonance imaging apparatus of the present invention, since no mixing material is mixed in the first filler,
In the state before curing, the viscosity is small and fluidization is easy. Therefore, when the first filler is poured into a predetermined molding die in which the coil conductor is arranged, the first filler enters all gaps in the die.

On the other hand, since the mixed material is mixed in the second filler, the strength is increased in the cured state. Therefore, even if cracks occur in the first filler having low strength after curing, almost no cracks occur in the second filler. Therefore, the cooling tube embedded in the second filler is not damaged. Even if a crack occurs in the first filler, the internal coil conductor is made of metal, so that the conductor itself does not crack and does not adversely affect the performance of the coil.

In the preferred embodiment of the present invention, the cracks are fixed between the coil portion and the cooling portion with the crack blocking layer interposed therebetween, so that the cracks generated in the first filler are stopped at the crack blocking layer and the second filler is stopped. Does not progress to the filler.

Further, since the second filler contains a mixed material having a high thermal conductivity, the thermal conductivity around the cooling tube is increased, and the cooling effect on the gradient coil is improved.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magnetic resonance imaging apparatus according to the present invention will be described below with reference to the accompanying drawings. In addition,
Components that are substantially the same as those in the related art are denoted by the same reference numerals, and description thereof is omitted.

FIG. 1 is a longitudinal sectional view showing a gradient magnetic field coil 31 provided in the magnetic resonance imaging apparatus of this embodiment.

The gradient magnetic field coil 31 includes a substantially cylindrical coil part 32 and a substantially cylindrical cooling part 33 disposed inside the coil part 32.

The coil portion 32 has the coil conductors 11, 12, and 13 in the x, y, and z directions embedded in a first filler 30 formed by including a first resin. As the first resin 34, for example, an epoxy resin is preferably used.

On the other hand, the cooling unit 33 includes the coil conductors 11,
Cooling tube 1 for passing refrigerant for cooling 12, 13
5 is buried in a second filler 29 formed by including a second resin 35 mixed with a predetermined mixing material 37.
As the second resin 35, for example, it is preferable to use an epoxy resin like the first resin.

As the mixed material 37, silica powder, glass fiber, aluminum oxide powder or the like is preferably used.

The cooling section 33 is formed by pouring the second filler 29 into a crack blocking member 36 capable of blocking cracks. The crack blocking member 36 is preferably formed of, for example, glass fiber reinforced plastic.

The cooling tube 15 is formed in a spiral shape as shown in FIG.

In order to manufacture the gradient coil provided in the magnetic resonance imaging apparatus of the present embodiment, first, a mold capable of molding the cylindrical cooling part 33 is prepared. Next, a crack blocking member 36 is attached inside the mold, and the cooling tube 15 is arranged at a predetermined position.

Next, in the state where the above-mentioned mold is set upright,
And after a lapse of a predetermined time, the molded cooling section 33 is taken out of the mold. Here, the second filler 2
Although the mixture 9 contains the mixed material 37 and has a slightly higher viscosity, the periphery of the cooling tube 15 has a much simpler structure than the periphery of the coil conductor.
Flows into the gap around the cooling tube 15.

Next, coil conductors 11, 12, and 13 are wound around the outer peripheral surface of the cooling section 33 taken out of the mold in a predetermined order, and the coil conductors are placed in a gradient magnetic field coil molding mold prepared separately. Deploy.

Next, the first filler 30 is poured into the above-mentioned mold, and the cooling section 33 and the coil section 32 are integrally fixed.

Here, the first filler 30 is made of the first resin 3
4 and contains no mixed material, and thus has a low viscosity in a state before hardening and is easily fluidized. Therefore, the first filler 30 enters all gaps in the mold.

On the other hand, since the strength of the first filler 30 after curing is low, there is a possibility that cracks may occur due to heat shrinkage or the like at the time of curing. However, the mixing material 37 is mixed into the second filler 29. Therefore, the strength after curing is high.

Therefore, as shown in FIG. 3, even if cracks 41 occur in the first filler 30, almost no cracks occur in the second filler 29. Therefore,
The cooling tube 15 embedded in the second filler 29 is not damaged. Further, since both are fixed with the crack blocking layer 36 interposed between the coil part 32 and the cooling part 33, the cracks 41 generated in the first filler 30 are removed by the crack blocking layer 36.
And does not proceed to the inside of the cooling unit 33.

Next, after a lapse of a predetermined time, the formed gradient magnetic field coil 31 is removed from the mold.

When the completed gradient magnetic field coil 31 is operated, a crack may be generated in the first filler 30 due to the electromagnetic force acting on the coil conductors 11, 12, and 13. For the same reason, cracks hardly occur in the second filler 29.

As described above, the gradient magnetic field coil provided in the magnetic resonance imaging apparatus of the present embodiment fills the periphery of the coil conductor with the first filler material containing no mixed material, while filling the first filler material containing the mixed material with the first filler material. Since the filler 2 is filled around the cooling tube, the first filler exhibits high fluidity before hardening, and flows into the gaps of the coil conductors arranged in a complicated manner. Thus, a good coil portion without a cavity is formed.

Further, since the second filler has a high strength after hardening due to the inclusion of the contaminant, the risk of cracks is extremely reduced, and the cracks generated in the first filler are reduced to the second filler. It hardly reaches the filler.

Therefore, there is no possibility that the refrigerant will flow out due to cracks in the cooling tube, and the reliability of the gradient magnetic field coil will be greatly improved.

Further, since the mixed material having a high thermal conductivity is mixed in the second filler, the thermal conductivity around the cooling tube is also increased, and the cooling efficiency of the gradient coil is improved.

For this reason, the arrangement of the cooling tubes is simplified, for example, it is only necessary to arrange them in a spiral shape. Further, the size of the refrigerant supply device can be reduced.

In the above embodiment, the arrangement of the cooling tubes is helical, but the arrangement is not limited to this arrangement, and other simple arrangements can be adopted.

Further, in the above-described embodiment, it has been described that silica powder, glass fiber, aluminum oxide powder and the like can be used as the mixing material. However, the present invention is not limited to such a material and has a high thermal conductivity. Various other materials can be used.

FIG. 4 shows a longitudinal section of a gradient magnetic field coil 51 according to a modification of the above-described embodiment. Note that the same reference numerals are given to components substantially the same as those of the prior art or the above-described embodiment, and description thereof will be omitted.

The gradient magnetic field coil 51 has a configuration in which a main coil portion 59 is disposed inside the cooling portion 33 having a cylindrical shape, and a shield coil portion 55 is disposed outside.

The main coil portion 59 and the shield coil portion 55 are configured such that a predetermined gradient magnetic field is formed at a predetermined position where the subject is to be arranged, and the gradient magnetic field is offset in an outer region. There are x, y,
The main coil conductors 56, 57, 58, x, y,
The z-direction shield coil conductors 52, 53, 54 are embedded in the first filler 30.

As in the gradient magnetic field coil of the above-described embodiment, the gradient filler coil of the present modification uses the first filler 30 containing no mixed material and the shield coil conductors 52, 53, 54 and the main coil conductors 56, 57, 57. While filling around 58,
The second filler 29 containing the mixed material 37 is supplied to the cooling tube 1
5, the first filler 30 is filled with
Before hardening, it exhibits high fluidity and flows all the way through the intricately arranged coil conductors,
A good coil part without a cavity is formed.

Further, since the second filler 29 has a high strength after hardening due to the inclusion of the mixed material 37, the risk of cracks is extremely reduced, and as shown in FIG. The crack 61 generated in the
Hardly reaches the filling material 29.

As a result, there is no possibility that the coolant will flow out due to cracks in the cooling tube, and the reliability of the gradient magnetic field coil will be greatly improved.

Further, since the mixed material having high thermal conductivity is mixed in the second filler, the thermal conductivity around the cooling tube is also increased, and the cooling efficiency of the gradient coil is improved.

Therefore, the arrangement of the cooling tubes is simplified, for example, it is only necessary to arrange them in a spiral shape.

The gradient magnetic field coil having the shield coil as shown in the present modification easily generates heat as compared with the gradient magnetic field coil having no shield coil, so that the present invention has a particularly remarkable effect. is there.

[0052]

As described above, according to the magnetic resonance imaging apparatus of the present invention, the first resin including the first resin is formed.
A coil portion in which a coil conductor is buried in a filler material and a second resin formed by including a second resin mixed with a predetermined mixing material.
Because a gradient magnetic field coil having a basic configuration formed by fixing a cooling portion in which a cooling tube is embedded in a filler material is employed, cracks occur in the cooling tube of the gradient magnetic field coil. The outflow of the refrigerant can be prevented. In particular, the cooling efficiency of the gradient magnetic field coil can be improved by making the thermal conductivity of the mixed material larger than that of the second resin.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a gradient coil provided in a magnetic resonance imaging apparatus of the present embodiment.

FIG. 2 is a perspective view showing a cooling unit of the gradient magnetic field coil according to the embodiment.

FIG. 3 is a diagram for explaining the operation of the gradient magnetic field coil according to the embodiment.

FIG. 4 is a longitudinal sectional view of a gradient coil according to a modification.

FIG. 5 is a diagram illustrating the operation of a gradient magnetic field coil according to a modification.

FIG. 6 is an overall view of a magnetic resonance imaging apparatus.

FIG. 7 is a longitudinal sectional view of a conventional gradient magnetic field coil.

FIG. 8 is a diagram showing cracks generated in a conventional gradient coil.

[Explanation of symbols]

 11,56 x direction coil conductor 12,57 y direction coil conductor 13,58 z direction coil conductor 15 cooling tube 29 second filling material 30 first filling material 31,51 gradient magnetic field coil 32 coil part 33 cooling part 34 first 1 resin 35 second resin 36 crack blocking member 37 mixed material 41, 61 crack 52 x-direction shield coil conductor 53 y-direction shield coil conductor 54 z-direction shield coil conductor 55 shield coil part 59 main coil part

Claims (7)

(57) [Claims] 1. A magnetic resonance imaging apparatus comprising: a magnet capable of applying a predetermined static magnetic field to a subject; and a gradient magnetic field coil capable of applying a predetermined gradient magnetic field superimposed on the static magnetic field. A coil conductor capable of generating a gradient magnetic field is formed by a first resin including a first resin.
A coil portion embedded in the filler and a cooling tube for passing a cooling medium for cooling the coil conductor are formed in a second filler formed by including a second resin mixed with a predetermined mixing material. A magnetic resonance imaging apparatus characterized in that a cooling unit embedded in a magnetic field is fixed to each other. 2. The magnetic resonance apparatus according to claim 1, wherein the first and second resins are both epoxy resins, and the mixed material is one of silica powder, glass fiber, and aluminum oxide powder. Imaging device. 3. The magnetic resonance imaging apparatus according to claim 1, wherein a crack blocking member for blocking the progress of the crack is sandwiched between the coil section and the cooling section. 4. The magnetic resonance imaging apparatus according to claim 3, wherein said crack blocking member is formed of glass fiber reinforced plastic. 5. The magnetic resonance imaging apparatus according to claim 1, wherein the cooling tube is formed in a spiral shape. 6. A magnetic resonance imaging apparatus comprising: a magnet capable of applying a predetermined static magnetic field to a subject; and a gradient coil capable of applying a predetermined gradient magnetic field superimposed on the static magnetic field. And a main coil portion in which a main coil conductor capable of generating a gradient magnetic field is buried in a first filler material containing a first resin, and the gradient magnetic field is offset by an external region of the gradient magnetic field coil. A shield coil conductor capable of generating a possible shield magnetic field is passed through a shield coil portion embedded in a separate first filler formed containing the first resin, and a coolant for cooling the coil conductor is passed. A cooling section embedded in a second filler material formed by including a second resin mixed with a predetermined mixing material and fixed to each other. Magnetic resonance Imaging device. 7. The magnetic resonance imaging apparatus according to claim 1, wherein the mixed material is a mixed material having a higher thermal conductivity than the second resin.