JP5298364B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention relates to a magnetic resonance imaging (hereinafter referred to as MRI) apparatus using a superconducting magnet, and more particularly to a magnetic resonance imaging apparatus provided with an apparatus for collecting information such as a refrigerant state of a superconducting magnet.

  A superconducting magnet used as a static magnetic field generation source of an MRI apparatus is used by energizing a permanent current by immersing a superconducting coil in liquid helium and maintaining the temperature below the liquid helium temperature. In order to maintain the characteristics as a superconducting magnet, it is important to keep the amount of liquid helium above a predetermined level. The internal pressure of the helium container of the superconducting magnet shows a change depending on the state of the superconducting magnet, such as the evaporation amount of liquid helium, the leak amount of the container, or the vacuum degree of the vacuum container for heat insulation. Therefore, in order to operate the superconducting magnet safely, it is necessary to collect and monitor the above-described magnet information such as the liquid helium amount (liquid level), the pressure inside the magnet, and the temperature.

  Patent Document 1 discloses an MRI apparatus equipped with a device for collecting and monitoring magnet information of superconducting magnets. In the MRI apparatus of Patent Document 1, a liquid helium level sensor or a temperature sensor is attached to a superconducting magnet disposed in a radiographing room, and an output signal line of the sensor is drawn into a machine room adjacent to the radiographing room and input to an environmental monitoring apparatus. Yes. The environmental monitoring device issues a warning when the amount of liquid helium and the temperature are outside the allowable ranges. In the machine room, in addition to the environmental monitoring device, a power source for supplying power to the gradient magnetic field coil, a computer for performing image reconstruction processing, and the like are arranged. A low-pass filter is arranged at the wall surface position where the sensor output signal line is drawn from the imaging room to the machine room.

  Patent Document 2 discloses an MRI apparatus in which a liquid level sensor is attached to a superconducting magnet, and a measuring device obtains a liquid helium amount and a decrease amount from its output and issues a warning.

On the other hand, in Patent Document 3, a superconducting magnet is disposed in a shield room in order to prevent high-frequency noise generated by a gradient magnetic field power source or the like from being mixed into a signal line of a magnetic resonance signal, and an electromagnetic shielding conductor in the shield room. An MRI apparatus is disclosed in which a gradient magnetic field power supply and the like and a noise removing means are integrally stored in a mechanically and electrically connected casing.
Japanese Patent Laid-Open No. 9-224919 JP 2002-336216 A JP 2000-83920 A

  A device that collects information on a liquid helium level sensor or a temperature sensor, such as the environmental monitoring device described in Patent Document 1, automatically and actively transmits an electrical signal to the sensor to acquire an output, thereby obtaining high frequency noise Is generated. In the machine room, in addition to the environmental monitoring device, a gradient magnetic field power source and a computer for image reconstruction are arranged, so the high frequency noise generated by the environmental monitoring device is inclined from the gradient magnetic field power source as line noise and radiation noise. It mixes with the power supply line to the magnetic field coil, generates a distortion in the gradient magnetic field, and generates a distortion in the nuclear magnetic resonance (NMR) signal generated from the subject. Further, the high frequency noise of the environment monitoring apparatus is mixed in a signal line for drawing the NMR signal into the image reconstruction computer. When such noise is mixed, artifacts due to high frequency noise occur in the image obtained by reconstructing the NMR signal.

  In order to prevent high-frequency noise from affecting the NMR signal, it may be possible to stop the operation of the environment monitoring device during shooting. However, it is necessary to switch the environment monitoring device to non-operating / operating every time imaging is performed. Is complicated.

  In addition, when installing the superconducting magnet, an environmental monitoring device is used to check whether the superconducting magnet is sound by transportation, to check the amount of liquid helium, and to check the cooling status to determine whether excitation is possible. Output information is required. For that purpose, it is necessary to connect the environmental monitoring device to the superconducting magnet immediately after installation, but the superconducting magnet of the MRI device is very large, so it cannot be carried into the radiographing room from a normal door. Usually, the wall surface is removed, a large opening is provided, and then the wall surface is recreated. In the configuration described in Patent Document 1, a superconducting magnet is disposed in the photographing room, an environment monitoring device is disposed in the machine room, and a low-pass filter needs to be disposed at the wall surface position of the boundary between the two rooms. The environmental monitoring device cannot be connected to the superconducting magnet until the installation work is completed. For this reason, even after the superconducting magnet is carried in, the soundness of the superconducting magnet cannot be confirmed until the wall surface construction is completed, and the total number of days for the installation work of the MRI apparatus becomes longer.

  In the MRI apparatus described in Patent Document 2, a measuring apparatus is disposed in a radiographing room (electromagnetic shield room) together with a superconducting magnet. For this reason, when the measuring device actively performs arithmetic processing, high-frequency noise is generated. This is mixed into the signal line in the shielded room as radiation noise or line noise, and causes artifacts due to high frequency noise in the image obtained by reconstructing the NMR signal.

  On the other hand, the MRI apparatus described in Patent Document 3 does not have a function of monitoring the liquid helium amount of the superconducting magnet, and cannot grasp the state of the superconducting magnet.

  An object of the present invention is to provide an MRI apparatus capable of grasping the state of a superconducting magnet and preventing artifacts in a reconstructed image.

  In order to achieve the above object, according to the present invention, the following MRI apparatus is provided. That is, the MRI apparatus of the present invention includes a superconducting magnet, an electromagnetic wave shield covering a radiographing room in which the superconducting magnet is disposed, a detection unit disposed in the superconducting magnet to obtain information on the superconducting magnet, and a detection unit. And an information collecting device for collecting the information. The information collection device includes a processing unit that performs an operation of collecting information from the detection unit, a line noise removal unit that is disposed in the middle of a signal line that connects the processing unit and the detection unit, a processing unit, and a line noise removal unit And a housing for housing the housing. This housing is physically and electrically detachably connected to and fixed to the outer surface of the imaging chamber of the electromagnetic wave shield. Thus, by arranging the information collecting device outside the imaging chamber and fixing the housing to the outer surface of the electromagnetic wave shield, it becomes possible to ground the line noise with low impedance via the electromagnetic wave shield. As a result, line noise can be caused to flow to the ground via the electromagnetic wave shield, and entry into the photographing room can be prevented. In addition, radiation noise from the processing unit and wiring of the information collecting apparatus can be shielded by the housing.

  For example, the electromagnetic wave shield is grounded, and the ground potential portion of the line noise removing unit is electrically connected to the electromagnetic wave shield and grounded via the electromagnetic wave shield. Specifically, for example, the ground potential part of the line noise removing unit and the electromagnetic wave shield part are connected directly or by a ground line having the shortest length. As a result, the ground potential portion of the line noise removal unit is grounded at the shortest distance via the electromagnetic wave shield, so that this route has the lowest impedance, and the line noise flows to the ground through this route. At this time, it is desirable that the signal line connecting the processing unit and the line noise removing unit is arranged to have the shortest length.

  It is preferable that the housing has a shape that is self-supporting on the floor surface without being attached to the electromagnetic wave shield. For example, the casing is configured to have leg portions that are used independently on the floor surface. Thereby, even if the electromagnetic wave shield is not attached, the magnet information collecting device can be operated independently. Therefore, before the electromagnetic wave shield is completed at the time of installation of the MRI apparatus, information on the superconducting magnet can be collected, the superconducting magnet can be started up, and the installation period can be shortened.

  In addition, the MRI apparatus connects the gradient magnetic field coil disposed in the imaging room to apply the gradient magnetic field to the subject, the gradient magnetic field power source disposed outside the imaging room, and the gradient magnetic field coil and the gradient magnetic field power source. A gradient magnetic field line, a gradient magnetic field line noise removal unit disposed in the middle of the signal line, and a line noise removal unit housing for accommodating the gradient magnetic field line noise removal unit When the noise removal unit casing is physically and electrically connected and fixed to the outer surface of the imaging chamber of the electromagnetic wave shield, and the line noise removal unit is disposed in the line noise removal unit, The casing is preferably a separate member from the line noise removing section casing. Thereby, it is possible to prevent the line noise of the information collecting apparatus from being mixed into the signal line of the gradient magnetic field power source. At the same time, when the MRI apparatus is installed, the magnet information collecting apparatus can be operated independently of the gradient magnetic field line noise removing unit, so that the installation period can be shortened.

  As the detection unit, for example, a sensor that directly or indirectly detects the temperature of the superconducting coil of the superconducting magnet, a sensor that detects the amount of the cryogen in the cryogen container of the superconducting magnet, and a pressure in the cryogen container are detected. The configuration includes at least one of the sensors.

  As a first effect of the present invention, in an MRI apparatus using a superconducting magnet, information on the superconducting magnet can be collected and monitored constantly and automatically. In addition, since it is possible to prevent noise generated due to magnet information collection from being mixed into the NMR signal line or the like, a good MRI image can be acquired.

  As a second effect, by installing the magnet information collecting device for the superconducting magnet on the surface of the electromagnetic wave shield, the area occupied by the MRI device can be reduced, and a compact device can be provided.

  Furthermore, as a third effect, when the magnet information collecting apparatus is configured to be able to stand on the floor surface, the magnet startup workability can be improved, and the startup period of the MRI apparatus can be shortened. Work man-hours can be reduced.

  Hereinafter, an MRI apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the overall configuration and arrangement of the MRI apparatus of this embodiment. The MRI apparatus includes a superconducting magnet 1 that generates a static magnetic field in a predetermined imaging region, an MR module 22 for imaging a subject placed in the imaging region, and a subject mounted on the imaging region. A patient table 18, a main MR system unit 6, a host computer 7, and a console 17 are provided.

  The MR module 22 receives a gradient magnetic field coil that generates a gradient magnetic field in a triaxial direction orthogonal to the imaging region, an irradiation coil that irradiates a subject in the imaging region with a high-frequency magnetic field, and an NMR signal generated from the subject. Including a receiving coil. The MR module 22 is disposed in the vicinity of the imaging area.

  The main MR system unit 6 includes a power supply for the gradient magnetic field coil, a control device for controlling the patient table 18 and its operation panel, and a transmission / reception control device. The transmission / reception control device controls the RF module built in the noise filter box 4. The RF module includes a transmission circuit that supplies a high-frequency current to the irradiation coil and a reception circuit that amplifies the NMR signal detected by the reception coil.

  The host computer 7 reconstructs the subject image from the NMR signal amplified by the main MR system unit 6. The host computer 7 controls the operation of the main MR system unit 6 to apply a gradient magnetic field to the subject at a predetermined timing, irradiate a high-frequency magnetic field, and receive an NMR signal at a predetermined timing. The imaging pulse sequence is executed.

  The console 17 receives imaging pulse sequence condition settings from the operator and passes them to the host computer 7. Further, the console 17 is provided with an image display device, and a reconstructed image is displayed.

As shown in FIG. 2, superconducting magnet 1 includes a helium vessel 301 storing liquid helium and a superconducting coil 302 disposed therein. Although the helium container 301 is drawn in a cubic shape in FIG. 2 for the sake of illustration, in reality, the helium container 301 is actually composed of an upper container and a lower container that are vertically opposed to each other with an imaging region interposed therebetween, and a connecting container that connects them. Become. With such a configuration, the periphery of the imaging region is greatly open. Superconducting coils 302 are respectively disposed in the upper container and the lower container, and form a static magnetic field in the imaging region. The outer side of the helium vessel 301 is covered with a vacuum vessel 303 having a shape along the outer shape of the helium vessel 301. In the decompression space between the vacuum vessel 303 and the helium vessel 301, a radiation shield 304 that prevents heat from entering from the outside is disposed.

  As shown in FIG. 2, the helium vessel 301 is provided with a discharge pipe 305 for discharging the internal helium gas. A pressure sensor 306 is installed inside the discharge pipe 305 to measure the internal pressure of the helium vessel 301. The helium vessel 301 is provided with a heater 307 that heats and vaporizes liquid helium in order to raise the internal pressure of the helium vessel 301 below a predetermined value. Further, a liquid level sensor 308 is disposed in the helium container 301 to measure the amount of liquid helium.

  In the space between the vacuum vessel 303 and the helium vessel 301, a shield temperature sensor 309 for measuring the temperature of the radiation shield 304 is disposed, and the temperature of the superconducting coil 302 is indirectly measured.

  The power supply line to the heater 307, the output signal line of the liquid level sensor 308, the output signal line of the shield temperature sensor 309, and the output signal line of the pressure sensor 306 are the connectors 2 (see FIG. 1)).

  The superconducting magnet 1 and the MR module 22 are arranged in a shield room (photographing room) as shown in FIG. The wall surface, floor and ceiling of the photographing room are covered with a high frequency electromagnetic wave shield (RF shield) 5. The RF shield 5 is made of an electrical conductor such as copper foil, and is connected to the system ground 19. On the other hand, the main MR system unit 6 and the host computer 7 are disposed in the machine room 15. The console 17 is disposed in the operation room 16.

  A magnet information collecting device 12 and a noise filter box 4 are attached to the wall surface of the RF shield 5 on the machine room 15 side as shown in the perspective view of FIG.

  The magnet information collecting device 12 has a configuration block diagram in FIG. 4, a circuit diagram in FIG. 5, a perspective view in FIG. 6, and a magnet information collecting unit 3a, a line noise filter unit 11, and a housing. 12a. In FIG. 6, the housing 12a is illustrated in a state where one front panel is opened, but is used with the panel closed during imaging.

  The housing 12a is made of an electrical conductor such as aluminum, and has a plurality of screw fixing holes 62 on its side surface as shown in FIG. The housing 12a is physically connected to the wall surface of the RF shield 5 so as to be detachable as shown in FIG. The housing 12a is provided with a self-supporting leg 61 as shown in FIG. The magnet information collecting device 12 has a width and height of the casing 12a of about 50 cm, respectively. However, since the magnet information collecting device 12 is provided with the self-supporting legs 61, it can be fixed to the RF shield 5 even in a state where it cannot be fixed. Can be used independently. Therefore, the magnet information collecting device 12 can be used even before the wall surface of the RF shield 5 is completed.

  The line noise filter unit 11 includes four low band pass noise filters 11a to 11d as shown in FIG. The ground potential portions (for example, noise filter housings) of the noise filters 11 a to 11 d are directly and physically fixed to the RF shield 5. When the housing of the noise filters 11a to 11d is not a ground potential portion, the ground wire of the noise filter is connected to the RF shield 5 with the shortest distance. Thereby, the ground potential portions of the noise filters 11a to 11d are grounded with the shortest path, that is, with the minimum impedance.

  The power supply line 51 to the heater 307 of the superconducting magnet 1, the output signal line 52 of the liquid level sensor 308, the output signal line 53 of the shield temperature sensor 309, and the output signal line 54 of the pressure sensor 306 are respectively noise filters 11a to 11a. 11d is connected to the magnet information collecting unit 3a. The four signal lines 51 to 54 are arranged with the magnet information collecting unit 3a and the noise filters 11a to 11d and the signal line 51 so as to connect the noise filters 11a to 11d and the magnet information unit 3a with the shortest distance. -54 routing has been determined.

  The magnet information collecting unit 3a includes a central processing unit (CPU) 55 such as a programmable sequencer, for example, and transmits an electrical signal to each sensor 306, 308, 309 at a predetermined timing, and automatically and actively each sensor 306. , 308, and 309, and information on the pressure in the helium vessel 301, the liquid level of the liquid helium 308, and the temperature of the shield 304 is obtained. For example, when a cryosensor is used as the liquid level sensor 308, the liquid level is measured by supplying a current to the cryosensor and measuring its resistance value. The magnet information collecting unit 3a is connected to a power source 57 through a power supply line 56, and obtains power for driving itself, power for electric signals supplied to the sensors 306, 308, and 309, and power supplied to the heater 307. ing.

  Further, the CPU 55 performs control of the superconducting magnet 1 and control of alarm notification by reading and executing a program stored in advance in a built-in memory unit using the collected information.

  For example, when the output of the pressure sensor 306 is compared with a predetermined pressure and it is detected that the pressure in the helium vessel 301 is lower than the predetermined pressure, a predetermined current is supplied from the power source 57 to the heater 307. Control to supply As a result, the heater 307 vaporizes part of the liquid helium and maintains the pressure in the helium vessel 301 at a predetermined pressure. If the pressure in the helium vessel 301 cannot be maintained at a predetermined pressure even if such control is performed, the pressure cannot be maintained, and a signal instructing to notify the alarm to that effect is output to the host computer 1. . The host computer 1 notifies the alarm of pressure abnormality by displaying the fact on the display device of the console 17.

  Similarly, the CPU 55 estimates whether or not the liquid level of liquid helium is within a predetermined range, the temperature of the superconducting coil 302 from the temperature of the shield 304 by a predetermined calculation, and whether or not it is within the predetermined temperature range. , And the determination result is transferred to the host computer 7. The host computer issues a notification by displaying the determination result and, if necessary, an alarm on the display device of the console 17.

  On the other hand, the noise filter box 4 fixed to the wall surface on the machine room 15 side of the RF shield 5 along with the magnet information collecting device 12 as shown in FIG. A module 71, line noise filter units 72 and 73, and a housing 74 are provided. In FIG. 7, the front panel of the housing 74 is shown in a removed state, but the image is used in a closed state as shown in FIG. 3 during imaging.

  The RF module 71 includes a transmission circuit that supplies a high-frequency current to the irradiation coil, a reception circuit that amplifies the NMR signal detected by the reception coil, and two noise filters. Signal lines that connect the transmission circuit and the reception circuit to the transmission coil and the reception coil, respectively, are connected to the two noise filters. The line noise filter unit 72 includes two or more noise filters, and connects a control device that controls the patient table 18 of the main MR system unit 6 and its operation panel to the drive unit and operation panel of the patient table 18. Are connected to each other. The line noise filter unit 73 includes three noise filters, to which signal lines that connect the gradient magnetic field power supplies in the three axial directions to the gradient magnetic field coils are respectively connected. The ground line of each line noise filter is connected to the RF shield 5.

  The housing 74 is made of an electrical conductor, and a plurality of screw fixing holes 75 are provided on its side surface. Since the size of the casing 74 is as large as about 120 cm in width and about 150 cm in height, the casing 74 is physically fixed to the wall surface of the RF shield 5 as shown in FIG. Used in. Moreover, the housing 74 is also electrically connected to the RF shield 5 by this screwing.

  In the MRI apparatus having such a configuration, an operation for preventing high frequency noise during operation will be described.

  The magnet information collecting device 12 collects information from the pressure sensor 306, the liquid level sensor 308, and the shield temperature sensor 309 attached to the superconducting magnet 1, and performs energization control to the heater 307 as required by arithmetic processing. While adjusting the pressure, it is determined whether or not the superconducting magnet can be operated. At this time, the collection unit 3a of the magnet information collection device 12 performs communication and calculation processing with a sensor for collecting information, and thus generates line noise and radiation noise.

  Line noise is mixed in the signal lines 51 to 54. In the present embodiment, since the collection unit 3a and the noise filters 11a to 11d are connected by the signal lines 51 to 54 at the shortest distance, the noise mixed in the signal lines 51 to 54 as shown in FIG. The signal passes through the lines 51 to 54, passes through the casing having the ground potential of the noise filters 11 a to 11 d, and further flows to the system ground 19 through the RF shield 5. The noise flows in this way because the impedance of this path is minimum. Therefore, the noise mixed in each of the signal lines 51 to 54 does not pass through the noise filters 11a to 11d and does not enter the inside of the shield room (photographing room) covered with the RF shield 5. Thereby, the line noise of the magnet information collecting device 12 is mixed in the signal line of the supply current to the gradient magnetic field coil and the signal line of the supply current to the irradiation coil, and mixed into the output signal line of the receiving coil. Can be prevented.

  On the other hand, radiation noise generated by the signal lines 51 to 54 in the collection unit 3 a and the apparatus 12 is shielded by the housing 12 a and the RF shield 5. Thereby, radiation noise does not enter the shield room (photographing room), and the radiation noise does not affect other devices in the machine room 15.

  At the time of imaging, line noise is generated from the gradient magnetic field power source by executing the imaging pulse sequence. This line noise flows through the RF shield 5 from the ground potential portion or the ground line of the noise filter of the line noise filter unit 73 and is grounded. It flows to 19. Therefore, it cannot pass through the noise filter, and does not reach the gradient coil in the imaging room covered with the RF shield 5. Similarly, line noise generated by the RF module 71 flows from the noise filter in the RF module 71 to the ground 19 through the RF shield 5. The line noise mixed in the signal line of the control signal from the control device in the main MR system unit 6 to the patient table 18 and its operation panel is grounded from the noise filter in the line noise filter unit 73 through the RF shield 5 to the ground 19. Flowing.

  The housing 74 of the noise filter box 4 blocks radiation noise of other devices in the machine room 15 from reaching the signal line and the RF module 71 in the filter box 4. At the same time, the radiation noise generated by the RF module 71 is blocked from reaching other devices such as the magnet information collecting device 12 in the machine room 15.

  Thus, the MRI apparatus of the present invention has a structure that prevents line noise and radiation noise emitted from the magnet information collecting apparatus 12 from entering the shield room (photographing room). Further, it is not radiated into the machine room. Thereby, it is possible to prevent artifacts due to the high frequency noise of the magnet information collecting device 12 from occurring in the image obtained by reconstructing the NMR signal, and it is possible to provide a good MRI image.

  Further, since the magnet information collecting device 12 can be operated even during photographing, the superconducting magnet 1 can be used in a stable state.

  Furthermore, by installing the magnet information acquisition / collection device 12 on the wall surface of the RF shield 5, it is possible to increase the usable floor area of the machine room 15 and the shield room (photographing room).

  Next, procedures for carrying in and installing the MRI apparatus of the present invention will be described with reference to FIGS. 8 (a), (b), FIG. 9 and FIG.

  The superconducting magnet 1 of the MRI apparatus is large and heavy, and needs to be carried in so as not to give an impact. Therefore, first, as shown in the work process chart of FIG. 8A, a carry-in path for carrying the superconducting magnet 1 from the outside into the installation position (photographing room) is secured (step 801). Since the superconducting magnet 1 cannot be passed with a normal door size, an opening 26 is provided by breaking a part of the wall surface of the photographing room surrounded by the RF shield 5 as shown in FIG. . The process 801 for securing the carry-in route usually takes about 2 days.

  Next, the superconducting magnet 1 is carried into the photographing room through the opening 26 (step 802). This process takes about one day.

  After the carry-in, the magnet information collecting device 12 is arranged in the photographing room as shown in FIG. 9, and the pressure sensor 306, the liquid level sensor 308 and the shield temperature sensor 309 of the superconducting magnet 1 are output, and the heater 307 and magnet information are collected. Connect the device 12. At this point, the magnet information collecting device 12 can collect magnet information (step 803).

  As described with reference to FIG. 6, the magnet information collecting device 12 includes the independent casing 12 a and the casing 12 a includes the self-supporting legs 61, and thus the wall surface of the RF shield 5 as illustrated in FIG. 3. Even if it is not attached to the camera, only the magnet information collecting device 12 can be used independently in the photographing room. If necessary, as shown in FIG. 6, it is possible to facilitate connection with the output lines of the sensors 306, 308, and 309 by removing a part of the panel of the housing 12a.

  Next, as shown in FIG. 9, a liquid helium container (dewar) 23 is carried into the photographing room through the opening 26. The liquid helium container 23 is connected to the superconducting magnet 1 by a transfer tube (transfer tube) 24, and liquid helium or the like is injected into the helium container 301 of the superconducting magnet 1 (step 804). Since the magnet information collecting device 12 is already connected, the liquid level of the injected liquid helium is measured by the liquid level sensor 308 and acquired by the magnet information collecting device 12. Further, the magnet information collecting device 12 acquires the shield temperature from the output of the shield temperature sensor 309, and estimates the temperature of the superconducting coil 302 by calculation. Thereby, it is possible to determine whether or not the superconducting coil 302 is cooled to a predetermined temperature at which the superconducting coil is brought into a superconducting state. Further, the magnet information collecting device 12 obtains the pressure inside the helium vessel 301 from the output of the pressure sensor 306, and controls the heater 307 to maintain the pressure within a predetermined range.

  The liquid helium container 23 includes a transfer flow rate adjustment mechanism 25 that can control the helium gas pressure in the container 23, and uses information from the magnet information collection device 12 to adjust the helium transfer flow rate to the superconducting magnet 1. Also good. As a configuration that enables control of the helium gas pressure in the container 23, for example, a solenoid valve provided in the container 23, a combination of a heater provided in the container 23 and a circuit for controlling the amount of current supplied to the heater, etc. Can be used. The container 23 may be disposed in the machine room 15 for work.

  When the superconducting coil 302 is cooled to a predetermined temperature and reaches a superconducting state, the excitation power source 20 disposed in the machine room 15 is connected via the service port 21 as shown in FIG. Thereby, an excitation current is supplied from the excitation power supply 20 to the superconducting coil 302. Thereafter, by removing the exciting power supply 20 from the service port 21, a permanent current flows through the superconducting coil 302, and the superconducting magnet 1 generates a static magnetic field. If necessary, shim iron pieces, shim coils, and the like are attached to the superconducting magnet 1 to adjust the static magnetic field uniformity. The number of days required from the start of cooling in step 804 to the adjustment of the static magnetic field is usually about 4 days.

  It should be noted that the superconducting magnet can be excited or demagnetized automatically. In this case, the magnet information obtained by the magnet information collecting device 12 is transmitted to the excitation power source 20, and automatic operation is controlled on the excitation power source 20 side. Alternatively, the magnet information collection device 12 is configured to control the automatic operation when the magnet information collection device 12 receives information on the power supply state such as power ON / OFF and normal / abnormal operation from the excitation power source 20.

  In parallel with the above-described step 803, the wall surface and the RF shield 5 are repaired at the position of the opening 26 shown in FIGS. 9 and 10 (step 805). This step 805 takes about 2 days. When the wall surface and the RF shield 5 are repaired, the noise filter box 4 is screwed to the wall surface on the machine room 15 side and fixed as shown in FIG. 3 (step 806).

  In Step 804, when the excitation of the superconducting coil 302 is completed, the magnet information collecting device 12 is once detached from the superconducting magnet 1 and moved from the door of the photographing room to the machine room 15. The size of the magnet information collecting device 12 is about 50 cm in width and height as shown in FIG. 6, so that it can be easily carried out from the door of a normal photographing room even after repairing the opening 26 on the wall surface. be able to. The magnet information collecting apparatus 12 carried out is fixed by screwing to the wall surface on the machine room 15 side as shown in FIG.

  When the adjustment of the static magnetic field uniformity of the superconducting magnet 1 is completed in step 804, an MR system adjustment step 807 is performed. Specifically, the MR module 22 is arranged near the imaging space. A patient table 18 is arranged in the imaging room. A main MR system unit 6 and a host computer 7 are arranged in the machine room 15. An operation console 17 is arranged in the operation room 16. The information collecting device 12 is connected to the sensors 306, 308, and 309 of the superconducting magnet 1 and the heater 307 as shown in FIGS. The main MR system unit 6 is connected to the MR module 22 and the patient table 18 via the line noise filter unit 4 using signal lines. The host computer 7 is connected to the main MR system unit 6, the information collecting device 12, and the console 17 using signal lines.

  In this embodiment, since the steps 803 and 804 can be performed in parallel with the steps 805 and 806 as described above, the number of days required for the entire installation work can be shortened. That is, by making the magnet information collecting device 12 an independent device as shown in FIG. 6, it becomes possible to separate the wall surface restoration and installation work of the noise filter box 4 from the work of starting up the magnet 1 in parallel. Work period can be shortened.

  As a comparative example, when the magnet information collection device 12 does not include the housing 12a or is integrated with the noise filter box 4, the configuration can be used only when the magnet information collection device 12 is fixed to the wall surface of the RF shield 5. FIG. 8 (b) shows the work process for. In this case, information on the superconducting magnet 1 can be collected only after the wall surface repairing step 805 is completed and the step 806 for fixing the noise filter box 4 (and / or the magnet information collecting device 12) to the wall surface is completed (step 803). . For this reason, the magnet startup step 804, which requires the liquid helium level and temperature information, is further performed thereafter. Therefore, as is clear when comparing the installation process of the present embodiment in FIG. 8A and the installation process of the comparative example in FIG. 8B, the direction of the present embodiment is about 3.5 days. However, the construction period can be shortened.

  In addition, the magnet information collecting apparatus 12 of the present embodiment can be operated alone while being placed on the floor, which not only has an effect of shortening the work period when the MRI apparatus is installed, but also is used for a certain period of time for the magnet 1. This is also effective when the magnet 1 is temporarily installed in a warehouse or the like because there is no plan, or when preliminary cooling is performed in another place before carrying in. For example, when the magnet 1 is temporarily installed in a warehouse or when pre-cooling is performed at another location, the host computer 7 of the MRI apparatus is in an unusable state, but the magnet information collecting apparatus 12 capable of independent operation is superconducting. By connecting to the magnet 1, information on the magnet 1 can be collected, and function confirmation and preliminary cooling can be performed.

  As described above, according to the present invention, as a first effect, in an MRI apparatus using a superconducting magnet, the amount of liquid helium (level) necessary for safely operating the superconducting magnet, the pressure inside the magnet, Magnet information such as temperature can be collected and monitored constantly and automatically. In addition, since it is possible to prevent noise generated due to magnet information collection from being mixed into the NMR signal line or the like, a good MRI image can be acquired.

  As a second effect, the area occupied by the MRI system unit can be reduced by installing the magnet information collecting device 12 that acquires magnet information essential for maintenance and safety of the superconducting magnet on the wall surface of the RF shield 5. Device can be provided.

  Furthermore, as a third effect, the magnet information collecting device 12 that can be operated independently can increase the efficiency of magnet startup work, shorten the MRI system startup period, and reduce the number of work steps. Is possible. It is also possible to confirm the function of the magnet 1 and to perform preliminary cooling in a place where the host computer 7 cannot be used.

  In the present embodiment, the opening 26 incorporates the magnet information collecting device 12 and forms a part of the wall surface of the RF shield 5 after the magnetic field is raised. An opening for the filter box 4 may be provided.

  In the present embodiment, liquid helium is used as the cryogen for the superconducting magnet 1, but other cryogens may be used.

1 is a block diagram showing the configuration and arrangement of an MRI apparatus according to the present embodiment. The block diagram which shows the schematic structure of the superconducting magnet 1 of FIG. 1, and arrangement | positioning of a sensor. The perspective view which shows the positional relationship of the noise filter box 4 attached to the machine room side wall surface of the RF shield 5, and the magnet information collection apparatus 12 in the MRI apparatus of this Embodiment. 1 is a block diagram showing a configuration of an MRI apparatus according to an embodiment. The block diagram which shows the circuit structure of the magnet information collection apparatus 12 in the MRI apparatus of FIG. The perspective view of the magnet information collection apparatus 12 of the MRI apparatus of FIG. The perspective view of the noise filter box 4 of the MRI apparatus of FIG. (A) The process table | surface at the time of installation of the MRI apparatus in this Embodiment, (b) The process table | surface at the time of installation of the MRI apparatus of a comparative example. FIG. 9 is an explanatory diagram showing a state in which a liquid helium container (dewar) 23 is connected to the superconducting magnet 1 in step 804 of FIG. FIG. 9 is an explanatory diagram showing a state in which the excitation power source 20 is connected to the superconducting magnet 1 in step 804 of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Superconducting magnet, 2 ... Magnet side connector, 3a ... Magnet information collection unit, 4 ... Noise filter box, 5 ... RF shield, 6 ... Main MR system unit, G, 7 ... Host computer, 11 ... Noise filter box, 11a, 11b, 11c, 11d ... noise filter, 12a ... housing, 12 ... magnet information collecting device, 15 ... machine room, 16 ... operation room, 17 ... console, 18 ... patient table, 19 ... system ground, 20 ... Excitation power source, 21 ... service port, 22 ... MR module, 23 ... liquid helium container (dewar), 24 ... transfer tube (transfer tube), 25 ... transfer flow rate adjusting mechanism, 26 ... opening, 51, 52, 53, 54 ... Signal line, 55 ... CPU, 57 ... Power supply, 71 ... RF module, 72, 73 ... Line noise filter unit , 74 ... housing, 301 ... helium vessel, 302 ... superconducting coil, 303 ... vacuum vessel, 303 ... radiation heat shield, 305 ... gas discharge pipe, 306 ... pressure sensor, 307 ... heater, 308 ... liquid level sensor, 309 ... Shield temperature sensor.

Claims (8)

A superconducting magnet that generates a static magnetic field in the imaging region, a detection unit disposed in the superconducting magnet to acquire information on the superconducting magnet, and a first signal line connected to the detection unit, from the detection unit An information collecting apparatus that collects information of the MR module, an MR module including at least a receiving coil that receives a nuclear magnetic resonance signal of a subject arranged in the imaging region, and noise connected to the MR module by a second signal line A filter box, and an electromagnetic wave shield covering a radiographing room in which the superconducting magnet and the MR module are disposed ,
The information collection device is connected to the detection unit by the first signal line, and performs processing for collecting information from the detection unit, and line noise removal arranged in the middle of the first signal line. And a first housing that accommodates the processing unit and the line noise removing unit,
The noise filter box includes a noise filter connected to the receiving coil by the second signal line, and a second housing that houses the noise filter,
The first and second housings are separate bodies;
The first housing is detachably physically and electrically connected and fixed to an outer surface of the imaging chamber of the electromagnetic wave shield,
The second casing is physically and electrically connected and fixed to an outer surface of the imaging chamber of the electromagnetic wave shield at a position away from the first casing. Magnetic resonance imaging apparatus.   The magnetic resonance imaging apparatus according to claim 1, wherein the electromagnetic wave shield is grounded, and a ground potential part of the line noise removing unit is electrically connected to the electromagnetic wave shield and grounded via the electromagnetic wave shield. A magnetic resonance imaging apparatus.   3. The magnetic resonance imaging apparatus according to claim 2, wherein the ground potential portion of the line noise removing unit and the electromagnetic wave shielding unit are electrically connected directly or by a ground wire having a shortest length. Magnetic resonance imaging device. 4. The magnetic resonance imaging apparatus according to claim 3, wherein the first signal line connecting the processing unit and the line noise removing unit is arranged to have the shortest length. Resonance imaging device. The magnetic resonance imaging apparatus according to claim 1, wherein the first housing has a shape that is self-supporting on a floor surface without being attached to the electromagnetic wave shield. 2. The magnetic resonance imaging apparatus according to claim 1, wherein the MR module further includes a gradient magnetic field coil disposed in the imaging room for applying a gradient magnetic field to a subject .
A magnetic resonance imaging apparatus, further comprising a gradient magnetic field noise filter connected to the gradient magnetic field coil by a third signal line in the second casing of the noise filter box . The magnetic resonance imaging apparatus according to claim 1, wherein the superconducting magnet has a superconducting coil and a cryogen container in which the superconducting coil is disposed,
The detection unit is at least one of a sensor that directly or indirectly detects the temperature of the superconducting coil, a sensor that detects the amount of the cryogen in the cryogen container, and a sensor that detects the pressure in the cryogen container. A magnetic resonance imaging apparatus.   Collecting information from a superconducting magnet, an electromagnetic wave shield covering a radiographing room in which the superconducting magnet is disposed, a detection unit disposed in the superconducting magnet to obtain information on the superconducting magnet, and the detection unit An information collecting device,
  The information collection device includes a processing unit that performs an operation of collecting information from the detection unit, a line noise removal unit that is disposed in the middle of a signal line that connects the processing unit and the detection unit, and the processing unit. And a housing that houses the line noise removal unit,
  The housing is physically and electrically detachably connected and fixed to the outer surface of the imaging chamber of the electromagnetic wave shield,
  The shape of the housing is a shape that is self-supporting on the floor surface in a state where it is not attached to the electromagnetic wave shield, and is a shape having legs for use by being self-supporting on the floor surface. Magnetic resonance imaging device.

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