JP5992744B2 - Magnetic resonance imaging system - Google Patents

Description

  Embodiments described herein relate generally to a magnetic resonance imaging apparatus.

  Conventionally, as one of noise countermeasures at the time of imaging in a magnetic resonance imaging apparatus, by reducing the sound transmitted to the ear of the patient who is the subject by making the periphery of the gradient magnetic field coil, which is a sound generation source, in a vacuum state, the noise is reduced. Technology is known. As such a noise reduction technique, for example, there is a method in which a gradient magnetic field coil is arranged in a sealed container and the space in the sealed container is brought into a vacuum state.

JP-A-10-118043

  The problem to be solved by the present invention is to provide a magnetic resonance imaging apparatus capable of realizing the quietness of a gradient magnetic field coil by using a general-purpose seal member without using a sealed container for the gradient magnetic field coil. It is.

  A magnetic resonance imaging (MRI) apparatus according to an embodiment includes a substantially cylindrical static magnetic field magnet, a substantially cylindrical gradient magnetic field coil disposed on an inner peripheral side of the static magnetic field magnet, and the gradient magnetic field. A substantially cylindrical bore tube disposed on the inner peripheral side of the coil and a ring-shaped seal member are provided. The seal member is between the inner peripheral surface end of the static magnetic field magnet and the outer peripheral surface end of the gradient magnetic field coil, and between the inner peripheral surface end of the gradient magnetic field coil and the outer peripheral surface end of the bore tube. And sealed between at least one of the inner peripheral surface of the static magnetic field magnet and the outer peripheral surface of the gradient magnetic field coil and between the inner peripheral surface of the gradient magnetic field coil and the outer peripheral surface of the bore tube. Create a space. The seal member includes a first elastic member, a second elastic member, and a third elastic member. The first elastic member is formed in a ring shape having a width in the axial direction of the gradient magnetic field coil, becomes thicker toward an end portion on the sealed space side, and acts on an external force acting toward the sealed space side. The axial position is fixed. The second elastic member is formed in a ring shape having a width in the axial direction of the gradient magnetic field coil, is thinned toward an end portion on the sealed space side, and is applied by an external force acting toward the sealed space side. It moves to the said axial direction, contacting the inner peripheral side or outer peripheral side of 1 elastic member. The third elastic member is formed in a ring shape whose cross-sectional shape is a substantially C shape having a bent portion protruding toward the sealed space, and the first elastic member and the first elastic member are formed at both ends of the C-shaped cross section. The ends of the two elastic members on the sealed space side are closed.

FIG. 1 is a diagram showing the overall configuration of the MRI apparatus according to the present embodiment. FIG. 2 is a diagram showing an example of a noise reduction structure in a conventional MRI apparatus. FIG. 3 is a diagram showing another example of a noise reduction structure in a conventional MRI apparatus. FIG. 4 is a perspective view showing side end portions of the static magnetic field magnet, the gradient magnetic field coil, and the bore tube according to the first embodiment. FIG. 5 is a perspective view showing an appearance of the seal member according to the first embodiment. FIG. 6 is a cross-sectional view showing a cross-sectional shape of the seal member according to the first embodiment. FIG. 7 is a view for explaining a frictional force generated in the seal member according to the first embodiment. FIG. 8 is a cross-sectional view showing the shape of the seal member according to the second embodiment. FIG. 9 is a diagram illustrating a shape of the sealing member according to the second embodiment when used. FIG. 10 is an external view showing the shape of the seal member according to the third embodiment. FIG. 11 is an external view showing a ventilation portion according to the third embodiment. FIG. 12 is a diagram illustrating an example in which the second elastic member intermittently has cutout portions in the circumferential direction. FIG. 13 is a cross-sectional view showing the shape of the seal member according to the fourth embodiment. FIG. 14 is a cross-sectional view showing the shape of the seal member according to the fifth embodiment.

(First embodiment)
FIG. 1 is a diagram showing an overall configuration of an MRI apparatus 100 according to the first embodiment.

  The static magnetic field magnet 1 is formed in a substantially cylindrical shape, and generates a static magnetic field in an imaging space formed in the cylinder. For example, the static magnetic field magnet 1 has a substantially cylindrical vacuum vessel 1a and a superconducting coil 1b immersed in a cooling liquid in the vacuum vessel 1a.

  The gradient magnetic field coil 2 is formed in a substantially cylindrical shape and is disposed on the inner peripheral side of the static magnetic field magnet 1. The gradient magnetic field coil 2 applies a gradient magnetic field to the static magnetic field generated by the static magnetic field magnet 1 in the X-axis, Y-axis, and Z-axis directions by a current supplied from the gradient magnetic field power supply 7. For example, the gradient coil 2 is an ASGC (Active Shield Gradient Coil) having a main coil and a shield coil. In the ASGC coil, the main coil applies a gradient magnetic field in the X-axis, Y-axis, and Z-axis directions with respect to the static magnetic field, and the shield coil generates a magnetic field that cancels the leakage magnetic field from the main coil.

  The bore tube 3 is formed in a substantially cylindrical shape and is disposed on the inner peripheral side of the gradient magnetic field coil 2.

  The RF (Radio Frequency) coil 4 is formed in a substantially cylindrical shape and is disposed on the inner peripheral side of the bore tube 3. The RF coil 4 receives a high-frequency pulse from the transmitter 8 and applies a high-frequency magnetic field to the subject P arranged in the inner space. The RF coil 4 receives a magnetic resonance signal radiated from the subject P when the hydrogen nuclei are excited by the influence of the high-frequency magnetic field.

  The gradient coil support 5 supports the gradient coil 2 from below and fixes the position of the gradient coil 2. For example, the gradient coil support 5 is an arm-shaped member having one end fixed to the lower end of the static magnetic field magnet 1 and the other end fixed to the lower end of the gradient coil 2. The static magnetic field magnet 1 and the gradient magnetic field coil 2 are provided at both lower ends of each.

  The top plate 6 is provided on a bed (not shown) and is moved in the horizontal direction according to an instruction from the operator. At the time of imaging, the top plate 6 is moved into the imaging space with the subject P placed thereon.

  The gradient magnetic field power supply 7 supplies a current to the gradient magnetic field coil 2 under the control of the sequence control device 10.

  The transmission unit 8 supplies the RF coil 4 with a high-frequency pulse corresponding to a Larmor frequency under the control of the sequence control device 10.

  The receiving unit 9 detects the magnetic resonance signal received by the RF coil 4 under the control of the sequence control device 10, and transmits the magnetic resonance data obtained by digitizing the detected magnetic resonance signal to the sequence control device 10. To do.

  The sequence control device 10 controls the gradient magnetic field power supply 7, the transmission unit 8, and the reception unit 9 under the control of the computer system 11. Specifically, the sequence control device 10 generates a pulse sequence for collecting magnetic resonance data related to the subject P based on the imaging conditions transmitted from the computer system 11, and in accordance with the generated pulse sequence, The magnetic field power source 7, the transmission unit 8, and the reception unit 9 are controlled. Further, the sequence control unit 10 transfers the magnetic resonance data transmitted from the receiving unit 9 to the computer system 11.

  The computer system 11 controls the entire MRI apparatus 100 according to various operations received from the operator. For example, the computer system 11 receives an input of imaging conditions from the operator and transmits the received imaging conditions to the sequence control device 10. Further, for example, the computer system 11 reconstructs various images based on the magnetic resonance data transmitted from the sequence control device 10 and stores the reconstructed various images in the storage unit. Further, for example, the computer system 11 displays various images stored in the storage unit on the display unit in response to a request from the operator.

  Under such a configuration, the MRI apparatus 100 according to the first embodiment includes the seal members 12 and 13 in order to reduce noise caused by the vibration of the gradient magnetic field coil 2. The seal member 12 is inserted between the inner peripheral surface of the static magnetic field magnet 1 and the outer peripheral surface of the gradient magnetic field coil 2 at both axial ends of the static magnetic field magnet 1 and the gradient magnetic field coil 2. A sealed space is formed with the gradient coil 2. The seal member 13 is inserted between the inner peripheral surface of the gradient magnetic field coil 2 and the outer peripheral surface of the bore tube 3 at both axial ends of the gradient magnetic field coil 2 and the bore tube 3, A sealed space is formed between the bore tube 3. Each sealed space formed by the seal members 12 and 13 is kept in a vacuum state using a vacuum pump (not shown). The vacuum state here includes a low pressure state close to a vacuum.

  Here, conventionally, as one of noise countermeasures at the time of imaging in an MRI apparatus, the noise transmitted to the patient's ear, which is the subject, is reduced by making the periphery of the gradient magnetic field coil, which is a sound generation source, in a vacuum state. Technology is known. In such a silencing technique, for example, the following silencing structure is used, but each silencing structure has the following problems.

  FIG. 2 is a diagram showing an example of a noise reduction structure in a conventional MRI apparatus. As shown in FIG. 2, for example, a structure is known in which the gradient magnetic field coil 2 is disposed in a sealed container, and the sealed space in the sealed container is brought into a vacuum state. In the example shown in FIG. 2, the sealed container includes sealed covers 21 and 22 and a bore tube 3. In such a structure, since it is necessary to produce a sealed container in consideration of the support system of the gradient magnetic field coil 2 and the cables connected to the gradient magnetic field coil 2, the sealed container is large and expensive. In general, since the sealed container is divided into a plurality of parts, it is necessary to seal each connection part of each part with an O-ring or the like. Furthermore, when a cable connected to the gradient coil 2 or a water-cooled hose (see, for example, the cables 23 and 24 shown in FIG. 2) penetrates the sealed container, the penetrating portion is used with a special bush or the like. It needs to be sealed. That is, since many places are sealed, there is a high possibility that a vacuum leak will occur. Also, when a vacuum leak occurs, it is difficult to specify the leak location. Furthermore, the sealed container is generally heavy and requires a large number of workers for attaching and detaching operations. In addition, the time required for attaching and detaching becomes long, and workability at the time of attaching the sealed container and maintainability after attachment become worse.

  FIG. 3 is a diagram showing another example of a noise reduction structure in a conventional MRI apparatus. As shown in FIG. 3, for example, a gradient magnetic field is used in order to prevent a cable connected to the gradient coil 2, a water-cooled hose, etc. (see, for example, cables 23 and 24 shown in FIG. 3) from penetrating the sealed container. A structure in which the end face of the coil 2 is exposed to the atmosphere is also known. For example, the gap between the inner peripheral surface of the static magnetic field magnet 1 and the outer peripheral surface of the gradient magnetic field coil 2 is sealed by the seal member 32 at both axial ends of the static magnetic field magnet 1 and the gradient magnetic field coil 2. Further, the gap between the inner peripheral surface of the gradient magnetic field coil 2 and the outer peripheral surface of the bore tube 3 is sealed with a seal member 33 at both axial ends of the gradient magnetic field coil 2 and the bore tube 3. Thereby, a sealed space is formed between the static magnetic field magnet 1 and the gradient magnetic field coil 2 and between the gradient magnetic field coil 2 and the bore tube 3, and the sealed space is maintained in a vacuum state. In such a structure, when the size of the gap between the static magnetic field magnet 1 and the gradient magnetic field coil 2 or the size of the gap between the gradient magnetic field coil 2 and the bore tube 3 is changed, the seal is changed accordingly. The member 33 also needs to be changed. However, in general, in an MRI apparatus, the positional relationship among a static magnetic field magnet, a gradient magnetic field coil, and a bore tube changes depending on the configuration of the apparatus. Therefore, when such a structure is used, a seal member is generally used. I can't.

  In order to solve such a problem in the conventional noise reduction structure, the MRI apparatus 100 according to the first embodiment uses a general-purpose sealing member without using a hermetic container for a gradient magnetic field coil, and uses a gradient magnetic field coil. Realization of noise reduction.

  FIG. 4 is a perspective view showing side end portions of the static magnetic field magnet 1, the gradient magnetic field coil 2, and the bore tube 3 according to the first embodiment. As shown in FIG. 4, in this embodiment, the seal member 12 is inserted between the inner peripheral surface end of the static magnetic field magnet 1 and the outer peripheral surface end of the gradient magnetic field coil 2. Similarly, another seal member 12 is provided between the inner peripheral surface end of the static magnetic field magnet 1 and the outer peripheral surface end of the gradient magnetic field coil 2 at the opposite side end not shown in FIG. Is inserted. Thereby, the two sealing members 12 form a sealed space between the inner peripheral surface of the static magnetic field magnet 1 and the outer peripheral surface of the gradient magnetic field coil 2. In this embodiment, the seal member 13 is inserted between the inner peripheral surface end of the gradient magnetic field coil 2 and the outer peripheral surface end of the bore tube 3. Similarly, another seal member 13 is provided between the inner peripheral surface end of the gradient magnetic field coil 2 and the outer peripheral surface end of the bore tube 3 at the opposite side end not shown in FIG. Inserted. Thereby, the two sealing members 13 form a sealed space between the inner peripheral surface of the gradient coil 2 and the outer peripheral surface of the bore tube 3.

  FIG. 5 is a perspective view showing an appearance of the seal member 12 according to the first embodiment. As shown in FIG. 5, the seal member 12 is formed in a ring shape that is continuous in the circumferential direction. Alternatively, the seal member 12 may be formed in a ring shape in which at least a part in the circumferential direction is cut off. In other words, the seal member 12 does not necessarily have to be manufactured so as to be continuous in the circumferential direction, may be manufactured in a state where a part of the circumferential direction is cut off, or is manufactured by being divided into a plurality of arc-shaped parts. May be.

  FIG. 6 is a cross-sectional view showing a cross-sectional shape of the seal member 12 according to the first embodiment. FIG. 6 shows the state of the inner peripheral surface end of the static magnetic field magnet 1 and the outer peripheral surface end of the gradient magnetic field coil 2, and the outer peripheral surface end of the static magnetic field magnet 1 and the outer periphery of the gradient magnetic field coil 2. The state where the seal member 12 is inserted between the surface end portions is shown. As shown in FIG. 6, the seal member 12 includes a first elastic member 12a, a second elastic member 12b, and a third elastic member 12c. Each elastic member is made of a resin such as rubber, plastic, or PET (Polyethylene terephthalate).

  In the present embodiment, the case where the first elastic member 12a is disposed on the inner peripheral side and the third elastic member 12c is disposed on the outer peripheral side in the seal member 12 will be described. Not limited. For example, contrary to the present embodiment, the first elastic member 12a may be disposed on the outer peripheral side, and the third elastic member 12c may be disposed on the inner peripheral side.

  The first elastic member 12a is formed in a ring shape having a width in the axial direction of the gradient magnetic field coil 2, and is formed so as to become thicker toward the end portion on the sealed space S side. Here, the 1st elastic member 12a is arrange | positioned so that the position of the axial direction of the gradient magnetic field coil 2 may be fixed with respect to the external force which acts toward the sealed space S side.

  For example, the first elastic member 12a has an engaging portion 12d that protrudes in the radial direction of the seal member 12, as shown in FIG. The engaging portion 12d is formed so that the cross-sectional shape is L-shaped. In the first elastic member 12a, the engaging portion 12d engages with the end portion of the outer peripheral surface of the gradient magnetic field coil 2, so that the axial direction of the gradient magnetic field coil 2 with respect to an external force acting toward the sealed space S side. The position of is fixed. In addition, when the 1st elastic member 12a is arrange | positioned at an outer peripheral side and the 2nd elastic member 12b is arrange | positioned at an inner peripheral side, the engaging part 12d is the inner peripheral surface end of the static magnetic field magnet 1 Engage with the part.

  The second elastic member 12b is formed in a ring shape having a width in the axial direction of the gradient magnetic field coil 2, and is formed so as to become thinner toward the end portion on the sealed space S side. Here, the second elastic member 12b is arranged so as to move in the axial direction of the gradient magnetic field coil 2 while being in contact with the outer peripheral side of the first elastic member 12a by an external force acting toward the sealed space S side. Is done. In addition, when the 1st elastic member 12a is arrange | positioned at an outer inner peripheral side and the 2nd elastic member 12b is arrange | positioned at an inner peripheral side, the 2nd elastic member 12b is the 1st elastic member 12a. It arrange | positions so that it may move to the axial direction of the gradient magnetic field coil 2, contacting the inner peripheral side.

  The third elastic member 12c is formed in a ring shape having a substantially C-shaped cross section having a bent portion protruding toward the sealed space S side. Further, the third elastic member 12c is a first elastic member so as to close the end portions of the first elastic member 12a and the second elastic member 12b on the sealed space S side at both ends of the C-shaped cross section. 12a and the second elastic member 12b are formed integrally.

  As described above, in the present embodiment, the sealed space S formed between the static magnetic field magnet 1 and the gradient magnetic field coil 2 by the seal member 12 is kept in a vacuum state. Thus, the attraction | suction force which draws the sealing member 12 to the sealed space S side arises because sealed space becomes a vacuum state. In the present embodiment, this attractive force is converted into a friction force generated between the seal member 12 and the static magnetic field magnet 1 and a friction force generated between the seal member 12 and the gradient magnetic field coil 2.

  FIG. 7 is a diagram for explaining the frictional force generated in the seal member 12 according to the first embodiment. As shown in FIG. 7, in this embodiment, when the sealed space S formed between the static magnetic field magnet 1 and the gradient magnetic field coil 2 is in a vacuum state, the third elastic member 12c is sealed by vacuum. A suction force attracted toward the space S side works (see arrow A1 shown in FIG. 7). By this suction force, the third elastic member 12c moves to the sealed space S side. When the third elastic member 12c moves to the sealed space S side, the second elastic member 12b is also drawn toward the sealed space S side by the third elastic member 12c. At this time, the first elastic member 12a does not move to the sealed space S side because the axial position of the gradient magnetic field coil 2 is fixed with respect to the external force acting toward the sealed space S side. Here, the 1st elastic member 12a is formed so that it may become thick toward the edge part on the sealed space S side, and the 2nd elastic member 12b is toward the edge part on the sealed space S side. It is formed to be thin. Therefore, when only the second elastic member 12 b moves to the sealed space S side, the first elastic member 12 a and the second elastic member 12 b move so as to be relatively separated in the radial direction of the seal member 12. As a result, a force for pressing the first elastic member 12a to the gradient magnetic field coil 2 side and a force for pressing the second elastic member 12b to the static magnetic field magnet 1 side are generated (see the arrow A2 shown in FIG. 7). See), and a frictional force is generated between the seal member 12 and the static magnetic field magnet 1 and between the seal member 12 and the gradient magnetic field coil 2.

  Thus, in the present embodiment, when the sealed space S is in a vacuum state, the attractive force acting on the third elastic member 12c is a friction force generated between the seal member 12 and the static magnetic field magnet 1, and It is converted into a frictional force generated between the seal member 12 and the gradient coil 2. That is, the seal member 12 generates a larger frictional force as it is attracted to the sealed space S side. As a result, the seal member 12 can be prevented from being sucked into the sealed space S side, and the gap between the static magnetic field magnet 1 and the gradient magnetic field coil 2 can be sealed more firmly. Even when the positional relationship between the static magnetic field magnet 1 and the gradient magnetic field coil 2 changes depending on the configuration of the apparatus, the first elasticity is adjusted in accordance with the size of the gap between the static magnetic field magnet 1 and the gradient magnetic field coil 2. Since the member 12a and the second elastic member 12b move so as to be relatively separated from each other in the radial direction of the seal member 12, the gap between the static magnetic field magnet 1 and the gradient magnetic field coil 2 can be appropriately sealed.

  It is desirable that the hardness of the third elastic member 12c be formed so as to be lower than the hardness of the first elastic member 12a and the second elastic member 12b. For example, the third elastic member 12c is formed using chloroprene rubber having a hardness of about 30 ° and a thickness of about 2.5 mm. On the other hand, the first elastic member 12a and the second elastic member 12b are formed using, for example, chloroprene rubber having a hardness of about 80 °. Further, the first elastic member 12a and the second elastic member 12b are formed, for example, with a thickness gradient of 20 ° and a maximum thickness of about 3.0 mm, and are formed integrally with the third elastic member 12c. The

  The third elastic member 12 c is preferably arranged so that both ends of the C-shaped cross section of the seal member 12 are in close contact with the inner peripheral surface of the static magnetic field magnet 1 and the outer peripheral surface of the gradient magnetic field coil 2. In this way, the hardness of the third elastic member 12c is lowered and brought into close contact with the inner peripheral surface of the static magnetic field magnet 1 and the outer peripheral surface of the gradient magnetic field coil 2, so that the gap between the static magnetic field magnet 1 and the seal member 12 is increased. The friction force and the friction force between the gradient magnetic field coil 2 and the seal member 12 can be increased. Thereby, the gap | interval between the static magnetic field magnet 1 and the gradient magnetic field coil 2 can be sealed more reliably.

  Further, it is desirable that a lubricant such as grease is applied to the contact surface 12e between the first elastic member 12a and the second elastic member 12b. Thereby, the frictional force between the 1st elastic member 12a and the 2nd elastic member 12b reduces, and it becomes possible to move the 1st elastic member 12a more smoothly without trouble.

  The second elastic member 12b is desirably formed so that the axial width of the gradient magnetic field coil 2 is wider than that of the first elastic member 12a. Thereby, even when the gap between the static magnetic field magnet 1 and the gradient magnetic field coil 2 is large, the first elastic member 12a can be moved deeper to the sealed space S side, and the static magnetic field magnet 1 and the gradient magnetic field coil 2 can be moved. Can be more reliably sealed.

  In addition, the inclination angle that increases toward the end portion on the sealed space S side in the first elastic member 12a and the inclination angle that decreases toward the end portion on the sealed space S side in the second elastic member 12b are the same. It is desirable that As a result, the first elastic member 12a is kept in parallel with the close contact surface on the gradient magnetic field coil 2 side and the close contact surface on the static magnetic field magnet 1 side of the second elastic member 12b. 12 a can be moved in the axial direction of the gradient coil 2. For this reason, even when the first elastic member 12a is moved, the sealed state can be stably maintained.

  The third elastic member 12c is desirably mixed with carbon black. Thereby, since the intensity | strength of the 3rd elastic member 12c is raised, it can prevent that the 3rd elastic member 12c is torn by the attraction | suction force by a vacuum.

  Although the sealing member 12 has been described here, the sealing member 13 inserted between the inner peripheral surface of the gradient magnetic field coil 2 and the outer peripheral surface of the bore tube 3 is also formed in the same manner as the sealing member 12. That is, the sealing member 13 is not the gap between the inner peripheral surface of the static magnetic field magnet 1 and the outer peripheral surface of the gradient magnetic field coil 2, but the inner peripheral surface of the gradient magnetic field coil 2 and the outer periphery of the bore tube 3. Only the gap between the surfaces serves as the seal member 12.

  As described above, according to the first embodiment, since the seal member in which the first elastic member, the second elastic member, and the third elastic member are integrated is used, it is used for sealing. The number of parts to be produced can be minimized, and the seal location can also be minimized. Therefore, the possibility of a vacuum leak is reduced, and the leak location can be easily estimated even if a vacuum leak occurs. In addition, since the seal member generates a frictional force that is attracted to the sealed space side, the surrounding area of the gradient magnetic field coil can be evacuated without using a sealed container for the gradient magnetic field coil. The workability such as can be improved. Even when the positional relationship among the static magnetic field magnet, the gradient magnetic field coil, and the bore tube changes depending on the configuration of the apparatus, the size of the gap between the static magnetic field magnet and the gradient magnetic field coil, or the gradient magnetic field coil and the bore tube In accordance with the size of the gap between the first elastic member and the second elastic member, the first elastic member and the second elastic member move relatively away from each other in the radial direction of the seal member. it can. That is, even when the positional relationship between the static magnetic field magnet, the gradient magnetic field coil, and the bore tube is shifted, or when various static magnetic field magnets, the gradient magnetic field coil, and the bore tube are combined, the seal member can be used for general purposes. it can. In other words, according to the first embodiment, it is possible to achieve noise reduction of the gradient magnetic field coil by using a general-purpose seal member without using a sealed container for the gradient magnetic field coil.

  Hereinafter, various modifications will be described as other embodiments. Note that the overall configuration of the MRI apparatus according to each embodiment described below is basically the same as that shown in FIG. Moreover, in embodiment described below, about the component which has the same function as the component shown in FIGS. 1-8, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

(Second Embodiment)
First, the second embodiment will be described. In the first embodiment, an example in which the third elastic member included in the seal member is formed in advance so as to have a substantially C-shaped cross-sectional shape has been described, but in the second embodiment, the third elastic member An example in which the elastic member is formed in a ring shape having a predetermined width and is bent in the axial direction of the gradient coil 2 will be described.

  FIG. 8 is a cross-sectional view showing the shape of the seal member according to the second embodiment. As shown in FIG. 8, the seal member according to this embodiment includes a first elastic member 112a, a second elastic member 112b, and a third elastic member 112c. Here, the 1st elastic member 112a is formed so that it may have the same cross-sectional shape as the 1st elastic member 12a demonstrated in 1st Embodiment, and the 2nd elastic member 112b is 1st Embodiment. It is formed to have the same cross-sectional shape as the second elastic member 12b described.

  The third elastic member 112c is formed in a ring shape having a predetermined width, the first elastic member 112a is provided at one end in the width direction, and the second elastic member 112b is provided at the other end. Is provided. Here, the third elastic member 112c is formed integrally with the first elastic member 112a and the second elastic member 112b. When the seal member according to the present embodiment is used, the third elastic member 112c is arranged in the axial direction of the gradient magnetic field coil 2 so that the first elastic member 112a and the second elastic member 112b face each other. Used by being bent.

  FIG. 9 is a diagram illustrating a shape of the sealing member according to the second embodiment when used. For example, as shown in FIG. 9, the sealing member according to the second embodiment is configured such that the third elastic member 112c is 180 so that the second elastic member 112b is disposed on the outer peripheral side of the first elastic member 112a. ° Used by folding. Alternatively, the seal member according to the second embodiment may be used by folding the third elastic member 112c 180 ° so that the first elastic member 112a is disposed on the outer peripheral side of the second elastic member 112b. Good.

(Third embodiment)
Next, a third embodiment will be described. In 1st Embodiment and 2nd Embodiment, although the example in case a seal member was previously formed in ring shape was demonstrated, in 3rd Embodiment, about the example in case a seal member is formed in strip | belt shape. explain.

  FIG. 10 is an external view showing the shape of the seal member according to the third embodiment. As shown in FIG. 10, the seal member 212 according to the present embodiment is formed in a band shape and is used by being bent into a ring shape. Here, the third elastic member included in the seal member 212 may be formed to have a substantially C-shaped cross-sectional shape in advance, like the third elastic member 12c described in the first embodiment. Alternatively, like the third elastic member 112c described in the second embodiment, it may be formed in advance so as to have a predetermined width and be bent in the axial direction of the gradient coil 2.

  In the third embodiment, the MRI apparatus 100 includes a ventilation portion having a ventilation hole for drawing air out of the sealed space formed by the seal member 212. The vent hole penetrates the sealed space and the space outside thereof, and the sealed space formed by the seal member 212 is kept in a vacuum state by drawing air through the vent hole using a vacuum pump. Be drunk.

  FIG. 11 is an external view showing a ventilation portion according to the third embodiment. As shown in FIG. 11, the ventilation part 220 has a ventilation hole 221 and is provided in a circumferential notch in the seal member 212. The notch here is a gap portion formed at a location where both ends of the seal member 212 face each other when the seal member 212 formed in a band shape is bent into a ring shape.

  For example, the first elastic member 212a and the second elastic member 212b included in the seal member 212 may be formed to have different hardnesses. For example, as shown in FIG. 11, when the second elastic member 212b is disposed on the outer peripheral side of the first elastic member 212a, the second elastic member 212b is compared with the first elastic member 212a. It is formed to have a low hardness. Conversely, when the first elastic member 212a is disposed on the outer peripheral side of the second elastic member 212b, the first elastic member 212a has a lower hardness than the second elastic member 212b. It is formed. Thereby, the difference in the circumference of the 1st elastic member 212a and the 2nd elastic member 212b after bending in a ring shape can be absorbed.

  Alternatively, one of the first elastic member 212a and the second elastic member 212b may be formed so as to intermittently have a notch in the circumferential direction.

  FIG. 12 is a diagram illustrating an example in which the second elastic member intermittently has cutout portions in the circumferential direction. As shown in FIG. 12, when the second elastic member 312b is disposed on the outer peripheral side of the first elastic member 312a, the second elastic member 312b has intermittent notches 321f in the circumferential direction. Formed as follows. Conversely, when the first elastic member 312a is disposed on the outer peripheral side of the second elastic member 312b, the first elastic member 312a is formed to have intermittent cutout portions in the circumferential direction. . As a result, as in the case of varying the hardness, the circumferential lengths of the first elastic member 312a and the second elastic member 312b after being bent into a ring shape by a plurality of intermittently provided cutout portions. Can absorb the difference.

(Fourth embodiment)
Next, a fourth embodiment will be described. In the fourth embodiment, an example will be described in which the first elastic member and the second elastic member included in the seal member have at least one protrusion on the side opposite to the side in contact with each other.

  FIG. 13 is a cross-sectional view showing the shape of the seal member according to the fourth embodiment. FIG. 13 shows the state of the inner peripheral surface end of the static magnetic field magnet 1 and the outer peripheral surface end of the gradient magnetic field coil 2, and the outer peripheral surface end of the static magnetic field magnet 1 and the outer periphery of the gradient magnetic field coil 2. A state in which the seal member is inserted between the surface end portions is shown. As shown in FIG. 13, the seal member according to this embodiment includes a first elastic member 412a, a second elastic member 412b, and a third elastic member 412c. Here, the first elastic member 412a and the second elastic member 412b have at least one protrusion on the side opposite to the side in contact with each other.

  In the example shown in FIG. 13, for example, the first elastic member 412a has two protrusions 412g, and the second elastic member 412b has one protrusion 412h. As described above, the first magnetic member 412a and the second elastic member 412b are provided with a protrusion on the opposite side to the side in contact with each other, so that the static magnetic field magnet 1 is provided at the position where the protrusion is provided. In addition, the pressure acting on the gradient coil 2 is locally increased. Thereby, the frictional force generated between the seal member and the static magnetic field magnet 1 and the frictional force generated between the seal member and the gradient magnetic field coil 2 can be further increased. The seal member inserted between the inner peripheral surface end of the gradient magnetic field coil 2 and the outer peripheral surface end of the bore tube 3 can be formed in the same manner.

(Fifth embodiment)
Next, a fifth embodiment will be described. In the fifth embodiment, the seal member inserted between the inner peripheral surface end of the static magnetic field magnet 1 and the outer peripheral surface end of the gradient magnetic field coil 2, the inner peripheral surface end of the gradient magnetic field coil 2, and the bore An example in which a seal member inserted between the end portion of the outer peripheral surface of the tube 3 is integrally formed will be described.

  FIG. 14 is a cross-sectional view showing the shape of the seal member according to the fifth embodiment. As shown in FIG. 14, for example, two seal members 512 and 612 formed in a ring shape are integrally formed via a seal relay portion 712. The first seal member 512 is inserted between the inner peripheral surface end of the static magnetic field magnet 1 and the outer peripheral surface end of the gradient magnetic field coil 2, and the inner peripheral surface of the static magnetic field magnet 1 and the outer periphery of the gradient magnetic field coil 2. A sealed space S1 is formed between the surfaces. The second seal member 612 is inserted between the inner peripheral surface end of the gradient magnetic field coil 2 and the outer peripheral surface end of the bore tube 3, and the inner peripheral surface of the gradient magnetic field coil 2 and the outer peripheral surface of the bore tube 3 are A sealed space S2 is formed between the two. Then, as shown in FIG. 14, the first seal member 512 and the second seal member 612 are integrally formed in a state of being connected so as to cover the side end face of the gradient magnetic field coil 2.

  The first to fifth embodiments have been described above. Although the said embodiment demonstrated the example in case the sealed space formed with a sealing member was maintained in a vacuum state, embodiment is not restricted to this. For example, the sealed space formed by the seal member may be maintained in an atmospheric state. In that case, since the suction force that draws the seal member toward the sealed space S side by vacuum does not occur, for example, after the second elastic member included in the seal member is pushed into the sealed space side by human power, The position of the elastic member 2 is fixed. For example, in the example shown in FIGS. 6 and 7, the second elastic member 12 b is pushed into the sealed space S side by human power, so that the sealing member 12 and the static magnetic field magnet 1 are applied in the same manner as when an attractive force by vacuum is applied. And a frictional force is generated between the sealing member 12 and the gradient coil 2. Thereby, the gap between the seal member 12 and the static magnetic field magnet 1 and the gap between the seal member 12 and the gradient coil 2 can be reliably sealed.

  Moreover, in the said embodiment, between the inner peripheral surface edge part of the static magnetic field magnet 1 and the outer peripheral surface edge part of the gradient magnetic field coil 2, and the inner peripheral surface edge part of the gradient magnetic field coil 2, and the outer peripheral surface of the bore tube 3 Although an example in which a seal member is inserted between both ends has been described, the embodiment is not limited thereto. For example, between the inner peripheral surface end of the static magnetic field magnet 1 and the outer peripheral surface end of the gradient magnetic field coil 2, and between the inner peripheral surface end of the gradient magnetic field coil 2 and the outer peripheral surface end of the bore tube 3. One of these may be sealed by a method using a conventional sealed container.

  Moreover, in the said embodiment, the both ends of the axial direction of the static magnetic field magnet 1 and the gradient magnetic field coil 2, and the both ends of the axial direction of the gradient magnetic field coil 2 and the bore tube 3 are each sealed with a sealing member. Although the example has been described, the embodiment is not limited thereto. For example, any one end in the axial direction of the static magnetic field magnet 1 and the gradient magnetic field coil 2 may be sealed with a seal member, and the other end may be sealed with a method using a conventional hermetic cover. Similarly, either one end in the axial direction of the gradient magnetic field coil 2 or the bore tube 3 may be sealed with a sealing member, and the other end may be sealed by a method using a conventional sealing cover.

  According to at least one embodiment described above, it is possible to achieve noise reduction of the gradient magnetic field coil by using a general-purpose seal member without using a sealed container for the gradient magnetic field coil.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 100 MRI apparatus 1 Static magnetic field magnet 2 Gradient magnetic field coil 3 Bore tube 12, 13 Seal member 12a 1st elastic member 12b 2nd elastic member 12c 3rd elastic member

Claims (15)

A substantially cylindrical static magnetic field magnet;
A substantially cylindrical gradient coil disposed on the inner circumference side of the static magnetic field magnet;
A substantially cylindrical bore tube disposed on the inner peripheral side of the gradient magnetic field coil;
At least one between the inner peripheral surface end of the static magnetic field magnet and the outer peripheral surface end of the gradient magnetic field coil and between the inner peripheral surface end of the gradient magnetic field coil and the outer peripheral surface end of the bore tube. Inserted to form a sealed space between at least one of the inner peripheral surface of the static magnetic field magnet and the outer peripheral surface of the gradient magnetic field coil and between the inner peripheral surface of the gradient magnetic field coil and the outer peripheral surface of the bore tube. A ring-shaped sealing member,
The sealing member is
It is formed in a ring shape having a width in the axial direction of the gradient magnetic field coil, becomes thicker toward the end portion on the sealed space side, and the position in the axial direction is fixed with respect to an external force acting toward the sealed space side. A first elastic member,
An inner circumference of the first elastic member is formed by a ring shape having a width in the axial direction of the gradient magnetic field coil, becomes thinner toward the end portion on the sealed space side, and acts on the sealed space side. A second elastic member that moves in the axial direction while contacting the side or the outer peripheral side;
A cross-sectional shape is formed in a ring shape that is a substantially C-shape having a bent portion protruding toward the sealed space, and the first elastic member and the second elastic member respectively at both ends of the C-shaped cross section. A magnetic resonance imaging apparatus comprising: a third elastic member that closes an end portion on a sealed space side.   2. The magnetic resonance imaging apparatus according to claim 1, wherein the hardness of the third elastic member is lower than the hardness of the first elastic member and the second elastic member. The first elastic member is
An engaging portion protruding in a radial direction of the seal member;
In a state of being inserted between an outer peripheral surface end portion of said seal member inner peripheral surface end portion and the gradient magnetic field coils of the field magnet, said engaging portion is engaged with the end portion of either in the position of the axis direction Ru is fixed with respect to the external force acting toward the sealed space side, or,
By the sealing member is to be engaged at one end in the inserted state, the engaging portion either between the inner peripheral surface end portion and the outer peripheral surface end of the bore tube of the gradient coil The magnetic resonance imaging apparatus according to claim 1, wherein the axial position is fixed with respect to an external force acting toward the sealed space side.   4. The magnetic resonance imaging apparatus according to claim 1, wherein the second elastic member is wider in the axial direction of the gradient magnetic field coil than the first elastic member. 5.   In the first elastic member, the inclination angle that increases toward the end portion on the sealed space side and the inclination angle that decreases in the second elastic member toward the end portion on the sealed space side are the same. The magnetic resonance imaging apparatus according to claim 1, wherein the magnetic resonance imaging apparatus is a magnetic resonance imaging apparatus. The sealing member is
Inserted between the inner peripheral surface end of the static magnetic field magnet and the outer peripheral surface end of the gradient magnetic field coil, and a sealed space is formed between the inner peripheral surface of the static magnetic field magnet and the outer peripheral surface of the gradient magnetic field coil. A ring-shaped first seal member to be formed;
It is inserted between the inner peripheral surface end of the gradient magnetic field coil and the outer peripheral surface end of the bore tube, and forms a sealed space between the inner peripheral surface of the gradient magnetic field coil and the outer peripheral surface of the bore tube. and a ring-shaped second sealing member,
The first seal member and the second seal member have the first elastic member, the second elastic member, and the third elastic member, respectively, and cover side end surfaces of the gradient coil. The magnetic resonance imaging apparatus according to claim 1, wherein the magnetic resonance imaging apparatus is integrally formed in a state where the magnetic resonance imaging apparatus is connected to the magnetic resonance imaging apparatus. Wherein the contact surface between the first elastic member and the second elastic member, a magnetic resonance imaging apparatus according to any one of claims 1 to 6 lubricant, characterized in Tei Rukoto applied. The third elastic member is
In a state of being inserted between an outer peripheral surface end portion of said seal member inner peripheral surface end portion and the gradient magnetic field coils of the field magnet, both end portions of the C-shaped cross-section, the inner periphery of the static magnetic field magnet In close contact with the outer surface of the surface and the gradient coil , or
In a state of being inserted between an outer peripheral surface end portion of said sealing member and the inner circumferential surface end of the gradient coil bore tube, both ends of the C-shaped cross-section, the inner peripheral surface of the gradient coil The magnetic resonance imaging apparatus according to claim 2, wherein the magnetic resonance imaging apparatus is in close contact with an outer peripheral surface of the bore tube. The magnetic resonance imaging apparatus according to claim 1, wherein the seal member has a ring shape that is continuous in a circumferential direction. The sealing member is a magnetic resonance imaging apparatus according to any one of claims 1 to 8 strip member, characterized in bending was shaped der Rukoto in a ring shape. Further comprising a vent having a vent for drawing air out of the sealed space;
The seal member has a notch in at least a part of the circumferential direction,
The vent, a magnetic resonance imaging apparatus according to any one of claims 1 to 8, characterized in that provided in the notch in the seal member.   The magnetic resonance imaging apparatus according to claim 10, wherein the first elastic member and the second elastic member are formed to have different hardnesses.   12. The magnetic resonance imaging according to claim 10, wherein one of the first elastic member and the second elastic member is formed so as to intermittently have a cutout portion in a circumferential direction. apparatus.   The magnetic resonance imaging apparatus according to claim 1, wherein the third elastic member is blended with carbon black. It said first elastic member and the second elastic member, the side opposite to the side in contact with each other, according to any one of claims 1 to 1 4, characterized in that it comprises at least one protrusion Magnetic resonance imaging equipment.

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