JP2005074066A - Magnetic resonance imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MRI apparatus capable of performing stable operation even with electromagnetic interference and the increase of a heating value associated with the improvement of capacity. <P>SOLUTION: Out of apparatus installed outside a shield room 109, an inclined magnetic field power source 111, a high frequency power amplifier 112, a receiver 113, a sequencer 106 and a computer 107 in which electromagnetic interference and heating are problems, are collectively installed in a shielding-radiating casing 200, and electromagnetic shielding and heat radiation of the individual devices are performed by this one casing 200. That is, satisfactory electromagnetic shielding and heat radiation heretofore difficult to attain by simply putting some devices together in one casing, can be carried out by using the shielding-radiating casing 200 exclusively used for electromagnetic shielding and heat radiation. This results in achieving the MRI apparatus capable of performing stable operation even with the electromagnetic interference and the increase of the heating value associated with the improvement of capacity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic resonance imaging apparatus (MRI apparatus), and more particularly to electromagnetic shielding and heat radiation processing for an MRI apparatus.

  MRI imaging methods that obtain tomographic images of human bodies and animals using the nuclear magnetic resonance (NMR) phenomenon and obtain internal information are widely used in the medical field and research field. An MRI apparatus that executes this MRI imaging method handles a high voltage and large current as a magnet that generates a uniform magnetic field strength in a space in which a subject is placed and a gradient magnetic field for obtaining position information. Further, in order to obtain an NMR signal obtained from the subject, a low voltage weak signal is handled in the receiving unit.

  If these electrical signals affect each other or the MRI apparatus is affected by unnecessary electromagnetic waves from the outside, artifacts will occur in the captured image. For this reason, the housing of each electronic device having a plurality of units that handle electrical signals is electromagnetically shielded using iron, aluminum, or the like. Then, the frame of the casing is regarded as the same potential at all locations, and a method such as connecting the ground wire from the individual units inside the casing to the frame portion at the shortest is used.

  Further, with the use of electric power in the electronic device or power supply device case, the amount of heat increases, and the temperature of each unit rises. Since this temperature rise may affect the characteristics of individual units, consider the layout inside the chassis so that each unit can be cooled efficiently by installing a cooling fan inside it. ing.

  Here, although not particularly related to the MRI apparatus, Patent Document 1 describes a technique for improving the heat dissipation of an electronic device using a semiconductor element.

  In Patent Document 1, an air flow path is formed inside a housing of an electronic device, and an air flow is formed in the air flow path by a fan. And the heat_generation | fever from a heat-emitting component is transmitted to the wall member of an air flow path through a heat transfer member, and the transmitted heat is discharge | released outside the housing | casing by the air flow in an air flow path.

Japanese Patent Laid-Open No. 11-87961

  Incidentally, the MRI apparatus is always required to shorten the imaging time. For this reason, a strong high-frequency magnetic field that realizes high-speed imaging, a gradient magnetic field that can be controlled at high speed, and a computer that can perform high-speed computation are required. The enhancement and speeding up of the apparatus capability for shortening the imaging time has a problem that it is necessary to further strengthen the prevention of electromagnetic interference from the outside with respect to the equipment constituting the MRI apparatus. There is also a problem that the amount of heat generation increases and the operation of the apparatus becomes unstable.

  In the prior art, for the problem of electromagnetic shielding, interference occurs by increasing the grounding wire attached to the casing or strengthening the electromagnetic shielding of the casing for each device constituting the MRI apparatus. It was a difficult structure.

  Also, with respect to the problem of an increase in the amount of heat generation, the number of fans is increased for each device, and a design that can obtain more cooling efficiency has been performed.

  However, considering the demand for further shortening of imaging time in the future, not only electromagnetic interference from the outside of the MRI apparatus, but also the mutual electromagneticity between each device (sequencer, computer, receiver, etc.) constituting the MRI apparatus. Although measures to effectively prevent interference are considered necessary, due to the resistance value of the casing of each device, there is a limit in effectively preventing electromagnetic interference with the conventional technology.

  As for the problem of heat generation, in the conventional technology, there is a limit to the number and location of fans installed for each device, so it is difficult to effectively prevent an increase in the amount of heat generation. it is conceivable that.

  The present invention was created to solve the above-described problems, and is to realize an MRI apparatus capable of stable operation even with respect to electromagnetic interference and increased heat generation accompanying the improvement in capability.

In order to achieve the above object, the present invention is configured as follows.
(1) Magnetic resonance having a static magnetic field generating means, a gradient magnetic field coil, a high frequency coil, a nuclear magnetic resonance signal detection coil, a device for receiving power supply or detection signal to these coils, and an operation control device In an imaging apparatus, it can be grounded and contains equipment (gradient magnetic field power supply, high-frequency power amplifier, receiver) that receives power supply to the coil or receives a detection signal and operation control equipment (sequencer, computer). A housing having a tubular member through which a medium can flow is provided.

  (2) Preferably, in the above (1), the casing includes a grounding material connected to a grounding wire outside the apparatus.

  (3) Preferably, in the above (1), the casing includes an electromagnetic shielding plate that electromagnetically shields each device.

  (4) Preferably, in the above (1), the tubular member also serves as a grounding material, and the casing is cooled by circulating a cooling medium in the tubular member.

  (5) Preferably, in the above (1), the tubular member also serves as a grounding material, and the tubular member is formed with a hole, and cooling gas is discharged from the hole into the casing to be cooled.

  In the magnetic resonance imaging apparatus of the present invention, among devices installed outside the shield room, a plurality of devices having problems of electromagnetic interference and heat generation are collectively installed in a single housing, and the single housing is used to individually The equipment is electromagnetically shielded and dissipated. In other words, it is possible to execute good electromagnetic shielding and heat dissipation, which has been difficult when several devices are simply combined into one housing, by using a housing dedicated to the electromagnetic shielding and heat dissipation.

  According to the present invention, it is possible to realize an MRI apparatus capable of stable operation even with respect to electromagnetic interference and an increase in the amount of heat generated due to an improvement in capability.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram of an MRI apparatus to which the present invention is applied.

  In FIG. 1, the MRI apparatus includes a static magnetic field generating magnet 102 disposed so as to sandwich a space in which a subject 101 is disposed, and a subject on the inner side (subject placement space side) of the static magnetic field generating magnet 102. A gradient magnetic field coil 103 disposed above and below, a high-frequency coil 104 disposed above and below the inside, and a detection coil 105 that detects an NMR signal generated from the subject 101 are provided. .

  The gradient magnetic field coil 103 and the high frequency coil 104 have a pair of upper and lower plate-like structures so as not to disturb the overall shape of the open type MRI apparatus. Further, the MRI apparatus includes a sequencer 106 that controls the operation timing of each of the coils 103 and 104, a computer 107 that controls the MRI apparatus and processes an NMR signal and performs imaging, and a subject 101 that generates a static magnetic field generating magnet 102. And a transport table 108 which is transported and arranged in the central space.

  The static magnetic field generating magnet 102, the gradient magnetic field coil 103, the high frequency coil 104, the detection coil 104, and the transfer table 108 are installed in a shield room 109 that is shielded from electromagnetic waves.

  The shielding of the electromagnetic wave by the shield room 109 is for the purpose of preventing the detection coil 105 from detecting the electromagnetic wave from the outside, and the resonance frequency (static magnetic field generating magnet 102) of the nucleus used for the inspection (usually a hydrogen nucleus is used). (Corresponding to the magnetic field strength of) of about 70 decibels.

  Connections between the various coils in the shield room 109, the static magnetic field generating magnet 102, the transfer table 108, and the power supply and control equipment outside the shield room 109 are grounded to the shield room 109 so as not to draw external noise into the shield room 109. Are connected via a filter circuit 110. Alternatively, the inside of the shield room 109 and the outside are connected by a coaxial cable whose outside is covered with a shield layer (FIG. 1 is an example using the filter circuit 110).

  The gradient magnetic field coil 103 is composed of three sets of coils wound so as to change the magnetic flux density in three axial directions (x, y, z) orthogonal to each other, and each coil is connected to the gradient magnetic field power supply 111, A gradient magnetic field generating means is configured.

  The gradient magnetic field power supply 111 is driven in accordance with a control signal from the sequencer 106 to be described later to change the value of the current flowing in the gradient magnetic field coil 103, whereby the gradient magnetic field (Gx, Gy, Gz) having three axes is arranged in the arrangement space of the subject 101. Is superimposed on the static magnetic field. This gradient magnetic field is used to identify the spatial distribution of NMR signals obtained from the imaging region of the subject 101.

  The high-frequency coil 104 is connected to a high-frequency power amplifier 112 for flowing a high-frequency current through a filter circuit 110, and generates a high-frequency magnetic field for resonantly exciting hydrogen nuclei in the imaging region of the subject 101. The high frequency power amplifier 112 is controlled in accordance with a control signal from the sequencer 106.

  The detection coil 104 is connected to the receiver 113 via the filter circuit 110 and constitutes a means for detecting the NMR signal. The receiver 113 amplifies and detects the NMR signal detected by the detection coil 104 and converts it into a digital signal that can be processed by the computer 107. The operation timing of the receiver 113 is controlled by the sequencer 106.

  The computer 107 performs operations such as image reconstruction and spectrum calculation using the NMR signals converted into digital quantities, and controls the operation of each unit of the MRI apparatus via the sequencer 106 at a predetermined timing.

  The display device 114 displays processed data and the like. The display device 114, the console 115, and the computer 107 constitute an arithmetic processing system. The gradient magnetic field power supply 111 is connected to the gradient magnetic field coil 103 via the filter circuit 110.

  The gradient magnetic field power supply 111, the high frequency power amplifier 112, the receiver 113, the sequencer 106, the computer 107, the console 115, and the display device 114 are installed outside the shield room 109.

  Here, among these devices installed outside the shield room 109, a gradient magnetic field power source 111, a high frequency power amplifier 112, a receiver 113, a sequencer 106, and a computer 107, which are problematic in terms of electromagnetic interference and heat generation. As described above, when electromagnetic shielding means and heat dissipation means are individually installed, it is difficult to perform effective electromagnetic shielding and heat dissipation.

  Therefore, these devices (gradient magnetic field power supply 111, high-frequency power amplifier 112, receiver 113, sequencer 106, computer 107) are collectively installed in one housing, and this single housing is used as an electromagnetic shielding means and a heat dissipation device. It is the shielding heat dissipation housing | casing 200 provided with a means.

  FIG. 2 is a schematic side view of the shield heat radiating housing 200, and FIG. 3 is a schematic perspective view of the shield heat radiating housing 200. In the illustrated example, a power source 121 that supplies power to each unit is disposed at the bottom.

  2 and 3, the housing 200 has a vertically long rectangular parallelepiped shape, and includes a plurality of shelf-like device installation portions on which the devices are arranged. A computer 107, a sequencer 106, a receiver 113, a high-frequency power amplifier 112, a gradient magnetic field power supply 111, and a power supply 121 are arranged in this equipment installation section in order from the top.

  The housing 200 includes a housing frame 201 using stainless steel, and the housing frame 201 includes a top plate portion, a shelf plate portion, and four pillar portions. And in order to make the electric potential of the whole housing | casing 200 correspond, the pipe-shaped grounding material 202 of diameter 15mm and thickness 2mm is installed along the flame | frame 201. FIG. That is, the pipe-shaped grounding material (tubular member) 202 is installed in the front left-right direction (each shelf board portion) and the right vertical surface (side surface) portion of the housing 200.

  Stainless steel used for the housing frame 201 has low electrical conductivity. When this frame 201 is used as a ground terminal, a difference occurs in the ground potential depending on the connection position. Therefore, the grounding material 202 is installed along the frame.

  Moreover, the electromagnetic shielding board 203 is attached to the housing 200 for each shelf part. Further, as shown in FIG. 3, the cooling medium is supplied and circulated in the pipe-shaped grounding material 202 by a heat exchanger built-in pump 206 and a cooling medium tank 207.

  As described above, according to one embodiment of the present invention, among the devices installed outside the shield room 109, the gradient magnetic field power supply 111, the high frequency power amplifier 112, and the reception that are problematic in electromagnetic interference and heat generation are received. The machine 113, the sequencer 106, and the computer 107 are collectively installed in one shield heat radiating housing 200, and electromagnetic shielding and heat radiation of individual devices are performed by this one housing 200. In other words, it is possible to execute good electromagnetic shielding and heat dissipation, which was difficult if several devices were simply combined into one housing, by using the shielding heat dissipation housing 200 dedicated to electromagnetic shielding and heat dissipation. It becomes.

  Therefore, it is possible to realize an MRI apparatus capable of stable operation even with respect to electromagnetic interference and increased heat generation accompanying the improvement in capability.

  In the above-described example, the refrigerant is circulated through the pipe-shaped grounding material 202. However, instead of circulating the refrigerant, a hole 204 is formed in the pipe-shaped grounding material 202 as shown in FIG. It is also possible to cool the housing 200 by discharging the cooling gas 205 from the holes 204. By discharging the cooling gas using the perforated pipe-shaped grounding material 202, it is possible to create a flow of cooling air that is difficult to obtain by cooling with only the fan, and to obtain a cooling effect.

  In the example of cooling by discharging the cooling gas, the heat exchanger built-in pump 206 shown in FIG. 3 is used as a blower fan, or a fan is attached to a hole for discharging the cooling gas. Alternatively, the heat exchanger built-in pump 206 can be used as a blower fan, and the fan can be attached to a hole for discharging a cooling gas.

  In the example of cooling by releasing the cooling gas, the cooling medium tank 207 shown in FIG. 3 is unnecessary.

  In the illustrated example, the copper grounding material 202 is arranged in the front left / right direction and the right side vertical direction, but the present invention is not limited to this, and there are various types depending on the shape of the case 200 and the shape of the case frame 201. The shape and use part can be considered.

  Further, the material of the grounding material 202 is not limited to copper depending on the place to be grounded, and a material according to the application can be considered.

It is a figure which shows the whole structure of the MRI apparatus with which this invention is applied. It is a schematic side view of the shielding heat dissipation housing in one embodiment of the present invention. It is a schematic perspective view of the shielding heat dissipation housing in one embodiment of the present invention. It is explanatory drawing of the example in the case of discharge | releasing the gas for cooling in the shielding heat dissipation housing of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Subject 102 Static magnetic field generating magnet 103 Gradient magnetic field coil 104 High frequency coil 105 Detection coil 106 Sequencer which controls the operation timing of each coil 107 Control of apparatus, computer which processes and signals NMR signal 108 Object transport table 109 Shield room DESCRIPTION OF SYMBOLS 110 Filter circuit 111 Gradient magnetic field power supply 112 High frequency power amplifier 113 Receiver 114 Display apparatus 115 Console 121 Power supply 200 Shielding heat dissipation housing 201 Housing frame 202 Grounding material 203 Shielding plate 204 Hole 205 Cooling gas 206 Heat exchanger built-in pump 207 Cooling Medium tank

Claims (5)

Static magnetic field generating means, gradient magnetic field coil, high frequency coil, nuclear magnetic resonance signal detection coil, power supply to these coils or a device for receiving detection signals, operation control device, and power supply to the coil Alternatively, in a magnetic resonance imaging apparatus having a housing that houses a device that receives a detection signal and an operation control device,
The case includes a tubular member that can be grounded and can flow a cooling medium.   2. The magnetic resonance imaging apparatus according to claim 1, wherein the housing includes a grounding material connected to a grounding wire outside the apparatus.   2. The magnetic resonance imaging apparatus according to claim 1, wherein the housing includes an electromagnetic shielding plate that electromagnetically shields each device.   2. The magnetic resonance imaging apparatus according to claim 1, wherein the tubular member also serves as a grounding material, and the casing is cooled by circulating a cooling medium in the tubular member. 2. The magnetic resonance imaging apparatus according to claim 1, wherein the tubular member also serves as a grounding material, and the tubular member is formed with a hole, and cooling gas is discharged from the hole into the casing to be cooled. Magnetic resonance imaging device.

Images