Superconducting coil device, magnetic resonance imaging apparatus equipped therewith, and method for controlling the temperature of the superconducting coil device

Abstract

To estimate whether the refrigerator has sufficient cooling performance to re-excite based on its normal cooling performance, thereby improving the speed and reliability of preventing quenching, and to prevent quenching even when the cooling performance of the refrigerator in an MRI device has deteriorated, thereby shortening the time until restart and re-imaging. [Solution] The superconducting coil device comprises a superconducting coil housed in a container, at least one refrigerator thermally connected to the superconducting coil for cooling, and a processor that receives temperature information of the superconducting coil detected by a temperature sensor installed in the container and issues a notification to the user. The processor maintains a temperature below the excitation temperature at which the superconducting coil can be excited as an excitation warning temperature, and issues notification information such as refrigerator replacement information when the temperature of the superconducting coil detected by the temperature sensor exceeds the excitation warning temperature for a predetermined time or longer.

Description

Technical Field

[0001] The present invention relates to a superconducting coil apparatus, and more particularly, to a helium-saving superconducting coil apparatus that cools a superconducting coil without filling a container housing the superconducting coil with helium, and a temperature management method thereof. The present invention further relates to a magnetic resonance imaging (hereinafter referred to as MRI) apparatus provided with the superconducting coil apparatus.

Background Art

[0002] Superconducting coil apparatuses are widely used as static magnetic field generators for MRI apparatuses and the like. Depending on the cooling method, superconducting coil apparatuses include a type in which a container housing the superconducting coil is filled with liquid helium to maintain the superconducting state of the coil, and a type in which the use of helium is reduced to zero or a low level (helium-saving apparatus). The latter further includes different types of apparatuses, such as a type (helium-free) in which a refrigerator is connected to the superconducting coil via a heat transfer member, and the coil is maintained at a low temperature at which the coil enters a superconducting state by wiring from the refrigerator, a type that uses gaseous helium and performs cooling by heat conduction from piping, and a type that performs cooling by heat conduction from piping for liquid or gaseous helium.

[0003] All superconducting coil apparatuses use a refrigerator to maintain the temperature inside the container or the temperature of the superconducting coil, but the performance of the refrigerator degrades over time. Therefore, the temperature inside the container is managed to monitor the performance of the refrigerator and manage the replacement timing of the refrigerator (Patent Document 1, Patent Document 2, etc.). For example, Patent Document 1 proposes a system for monitoring the temperature and pressure of a system that cools a superconducting coil used as a static magnetic field generating coil of an MRI apparatus using liquid helium.

[0004] In helium-saving superconducting coils, which do not fill the container with liquid helium, there is no helium heat capacity, so a decrease in the cooling performance of the refrigerator immediately leads to a temperature rise, requiring stricter control compared to devices that fill the container with helium for cooling. In contrast, Patent Document 2 proposes a technique for a superconducting coil device in an MRI system that does not use liquid helium, in which multiple refrigerators are installed, their temperatures are monitored, and if the cooling performance of one refrigerator deteriorates, another refrigerator is used to maintain the temperature inside the container. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2015-061993 [Patent Document 2] Japanese Patent Publication No. 2013-144099 [Overview of the project] [Problems that the invention aims to solve]

[0006] Conventional technology prevents superconducting coil quenching by monitoring the coil temperature and the cooling performance of the refrigerator, thus preventing the coil from reaching its critical temperature. However, in helium-free superconducting coil systems, the tolerance for temperature changes is significantly lower than in helium-based systems, making it insufficient to simply manage whether superconductivity can be maintained.

[0007] Superconducting coil systems are maintained periodically or when the performance of the refrigerator deteriorates. During maintenance, the superconducting coils are demagnetized, and re-energized after the refrigerator is replaced. To avoid forced quenching and to restart the system quickly after maintenance, it is crucial to prevent the superconducting coils from quenching during maintenance. However, conventional technology does not manage the superconducting coils considering the temperature changes that occur during maintenance. Therefore, it is impossible to respond to sudden situations such as power outages.

[0008] The present invention aims to improve the speed and reliability of preventing quenching in a superconducting coil device that uses less helium and has a low tolerance for temperature changes in the superconducting coil, by estimating whether or not it has sufficient cooling performance to re-excite based on the cooling performance of the refrigerator under normal conditions, and in imaging devices such as MRI devices equipped with a superconducting coil device, by predicting the possibility of imaging even when the cooling performance of the refrigerator has deteriorated, thereby preventing quenching and shortening the time until restart and re-imaging. [Means for solving the problem]

[0009] To solve the above problems, the present invention sets one or more warning temperatures lower than the critical temperature as temperatures for managing the temperature of a superconducting coil. It provides a means for the user to reliably prevent quenching by issuing notification information such as warnings and messages according to the warning temperature, such as replacing the cooler or continuing / stopping operation. In other words, the superconducting coil device of the present invention is a helium-saving superconducting coil device comprising a superconducting coil housed in a container and at least one refrigerator thermally connected to the superconducting coil for cooling the superconducting coil, further comprising a processor that receives temperature information of the superconducting coil detected by a temperature sensor installed in the container and issues a notification to the user. The processor maintains a temperature below the excitation temperature at which the superconducting coil can be excited as an excitation warning temperature, and issues a first notification when the temperature of the superconducting coil detected by the temperature sensor exceeds the excitation warning temperature for a predetermined time or longer.

[0010] Furthermore, the MRI apparatus of the present invention is a magnetic resonance imaging apparatus comprising a static magnetic field generating magnet and an imaging unit that acquires an NMR signal by generating nuclear magnetic resonance in atomic nuclei contained in a subject placed in the static magnetic field space generated by the static magnetic field generating magnet, wherein the superconducting coil apparatus of the present invention is used as the static magnetic field generating magnet.

[0011] Furthermore, the present invention provides a temperature management method for a superconducting coil device, which manages the temperature of a helium-free superconducting coil device and issues notification information according to the temperature. The method is characterized in that, as the temperature for managing the superconducting coil, an excitation warning temperature is set based on the critical temperature of the superconducting coil and the temperature rise due to heat generation during excitation, and when the temperature of the superconducting coil detected by the temperature sensor exceeds the excitation warning temperature, information regarding the timing of replacement of the refrigerator that cools the superconducting coil is issued.

[0012] In this specification, "critical temperature" refers to the temperature at which a superconducting coil quenches. This temperature varies depending on the materials of the superconducting coil and the environment, such as the magnetic field generated by the superconducting coil and the current flowing through it, but is typically 8-10K. "Excitable temperature" refers to the temperature at which excitation does not reach the critical temperature, i.e., the upper limit temperature at which excitation can be performed. "Excitation warning temperature" refers to a temperature above the set cooling temperature of the superconducting coil and below the excited temperature. [Effects of the Invention]

[0013] According to the present invention, it becomes possible to set an excitation warning temperature and, based on that excitation warning temperature, provide information about the need to replace the refrigerator or control the excitation operation. This enables the replacement of the refrigerator at the appropriate time and the reliable excitation and imaging operations that prevent quenching. Furthermore, according to the present invention, by setting a higher warning temperature in addition to the excitation warning temperature as a warning temperature to be managed, risks such as quenching can be managed in multiple stages. In particular, when applied to an MRI system, it becomes possible to manage the coil temperature while taking into account the temperature rise that occurs during imaging. [Brief explanation of the drawing]

[0014] [Figure 1] A diagram showing an overall overview of a superconducting coil device to which the present invention is applied. [Figure 2] Diagram showing the flow of coil temperature control and alarm activation process. [Figure 3] Flowchart of temperature control and alarm activation for the superconducting coil device in Embodiment 1 [Figure 4]Diagram showing the relationship of warning temperatures stored in the processor of Embodiment 2 [Figure 5] Diagram showing an example of notification information of Embodiment 2 [Figure 6] Diagram showing the processing flow of an application example [Figure 7] Diagram showing an example of notification information of the application example [Figure 8] Diagram showing the overall outline of an MRI apparatus to which the present invention is applied [Figure 9] Functional block diagram of the processor of the MRI apparatus of the present embodiment [Figure 10] Diagram showing another example of the functional block diagram of the processor [Figure 11] Diagram for explaining the relationship of warning temperatures set in the processor of Embodiment 3 and an example thereof [Figure 12] Diagram showing the processing flow of Embodiment 3 [Figure 13] Diagram showing the processing flow of Embodiment 4 [Figure 14] Functional block diagram of the processor and the storage unit of Embodiment 4 [Figure 15] Diagram showing an example of notification information of Embodiment 4 [Figure 16] Diagram showing the processing flow of Embodiment 5 [Modes for Carrying Out the Invention]

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0016] [Embodiment of Superconducting Coil Apparatus] As shown in Figure 1, the superconducting coil device 10 of this embodiment comprises, as its main elements, a superconducting coil 101 placed inside a vacuum vessel 102, a heat transfer member 103 surrounding the superconducting coil 101, a refrigerator 104 for cooling the superconducting coil 101, and a power supply circuit for demagnetizing and exciting the superconducting coil 101. In the figure, only the excitation power supply 105 is shown as part of the power supply circuit. Hereinafter, the superconducting coil 101, vacuum vessel 102, and heat transfer member 103 are collectively referred to as the coil unit 100. The individual elements constituting the coil unit 100 are the same as those of known superconducting coils, and a detailed explanation is omitted here, with only a brief description provided.

[0017] In the case of a superconducting coil 101 that generates a horizontal magnetic field, for example, a wire made of a superconducting material is wound around a cylindrical bobbin and housed in a cylindrical vacuum container 102. However, depending on the application in which the superconducting coil device 10 is used, the direction of the generated magnetic field is not limited to the horizontal direction, and the present invention is also applicable to superconducting coil devices that generate a vertical magnetic field.

[0018] The vacuum vessel 102, although not shown in the diagram, is equipped with a two- or three-layer thermal shield to maintain a low temperature below the critical temperature of the superconducting material. One or more temperature sensors (not shown) are provided inside the vacuum vessel 102 to detect the temperature. The temperature information detected by the temperature sensors is sent to a processor, which will be described later, to control the device.

[0019] Although only one refrigerator 104 is shown in the diagram, there may be multiple refrigerators. The refrigerator 104 comprises a cold head and a compressor (compressor unit) fixed to the vacuum vessel 102. The compressed refrigerant gas supplied from the compressor to the cold head undergoes adiabatic expansion inside the cold head, producing a cooling effect. The tip of the cold head is inserted into the vessel, thereby cooling the inside of the vessel to a predetermined temperature and cooling the superconducting coil 101 via the heat transfer member 103. The refrigerator 104 is also controlled by a processor to have a cooling capacity that cools the amount of heat that enters the vacuum vessel 102 without excess or deficiency. As a result, the superconducting coil 101 maintains a state of thermal equilibrium, realizing a closed-type superconducting magnet.

[0020] The excitation power supply 105 and the demagnetizing power supply (not shown) are electrically disconnected from the superconducting coil 101 while a permanent circuit is formed in the superconducting coil 101. However, when forming the permanent circuit, during maintenance, or in the event of a power outage, they are connected to the superconducting coil 101 to perform excitation, demagnetization, and re-excitation.

[0021] The superconducting coil device 10 is further equipped with a processor 200 that controls the excitation and demagnetization of the superconducting coil 101, and controls the refrigerator. The main functions of the processor 200 are the control of the power supply circuit and the control of the refrigerator (magnet control). However, the processor in this embodiment is characterized by having a function (coil temperature management and alarm function) that manages the temperature taking into account the temperature rise associated with predetermined processes performed by operators and maintenance workers (hereinafter collectively referred to as users) and warns the users.

[0022] In other words, the processor 200 receives temperature information (measured value and elapsed time) of the superconducting coil detected by a temperature sensor installed inside the container and notifies the user. Therefore, the processor 200 maintains information on a temperature at which a predetermined warning should be issued in relation to a predetermined process or operation (referred to as the warning temperature), compares the warning temperature with the temperature detected by the temperature sensor, and issues the necessary notification. The predetermined process or operation is a process or operation that causes a temperature rise inside the coil unit, and includes, for example, re-excitation of the superconducting coil and operation of an imaging device using the superconducting coil. The warning temperature is, for example, the critical temperature of the superconducting material and the excitation warning temperature. The critical temperature is the highest temperature required for the superconducting material to maintain its superconducting state, and varies depending on the type of superconducting material and the environment in which the superconducting coil is placed, such as the magnetic field and current, but is, for example, 8 to 10 K (Kelvin). The excitation warning temperature is a temperature that provides a margin of safety (excitation warning temperature = excitation temperature - margin) relative to the excitation temperature, which is the temperature at which the coil is estimated to reach a temperature close to the critical temperature when excited under the set excitation conditions. In addition, if the superconducting coil device is incorporated into an imaging device such as an MRI machine, a warning temperature (imaging warning temperature) is set to warn of the possibility of quenching due to temperature rise caused by the operation of the imaging device.

[0023] The notifications issued by the processor 200 may include various warnings, such as a warning that the refrigerator is nearing the end of its replacement period, a warning to immediately replace the refrigerator, and a notification indicating whether or not excitation is possible. The form of the notification will be described in detail in the embodiments described later. Such notifications are displayed on the display device 300 if the superconducting coil device 10 or the processor 200 is equipped with a display device 300 as an accessory device. They may also be displayed on the display device of the remote system 400 that performs maintenance, or on individual service personnel 500 who belong to the remote system 400 but are outside of the remote system 400. The form of the notification is not particularly limited, but in addition to being displayed as a message on the display device, it may also be accompanied by the generation of voice or warning sounds. Notifications to service personnel 500 can be made, for example, via portable devices carried by the service personnel 500.

[0024] Such processing by a processor can be performed on any computer. Any computer may perform these processes using a processor as hardware, a program as software, or a combination thereof. In this case, the processor is configured to work in cooperation with the program to perform the various processes in this embodiment, and can function as a unit or means in this embodiment. Furthermore, the execution order of the processor's processes is not limited to the order described and may be changed as appropriate. Any computer may be a general-purpose computer, a computer designed for a specific purpose, a workstation, or any other system capable of performing the processes.

[0025] A processor may consist of one or more hardware components, and the type of hardware is not limited. For example, a processor may consist of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a programmable logic device such as an FPGA (Field Programmable Gate Array), a dedicated circuit for executing a specific process such as an ASIC (Application Specific Integrated Circuit), a GPU (Graphic Processing Unit), or an NPU (Neural Processing Unit). Furthermore, the type of hardware may be a combination of different types of hardware. When multiple hardware components are configured to execute one or more processes of a processor, these components may reside in physically separate devices or in the same device. Also, in any embodiment, the order of each process performed by the processor is not limited to the order described above and may be changed as appropriate. Hardware is composed of electrical circuits (circuitry) that combine circuit elements such as semiconductor elements.

[0026] Furthermore, the program may be firmware or software such as microcode. Alternatively, the program may be, for example, a set of program modules, each function of which may be implemented by a processor configured to perform its respective function. The program may be program code or multiple code segments stored on one or more non-temporary computer-readable media (e.g., storage media or other storage). The program may be divided and stored on multiple non-temporary computer-readable media located on physically separate devices. Program code or code segments may represent any combination of procedures, functions, subprograms, routines, subroutines, modules, software packages, classes, or instructions, data structures, or program statements. Program code or code segments may be connected to other code segments or hardware circuits by sending and receiving information, data, arguments, parameters, or memory contents.

[0027] The following describes the temperature control and process performed by the processor 200 of the superconducting coil device 10 in this embodiment. Figure 2 shows an example of the processing performed by the processor 200.

[0028] In this embodiment, if the superconducting coil temperature is detected to be higher than the excitation warning temperature for an entire day while the superconducting coil device 10 is in operation, the processor 200 provides information about replacing the refrigerator.

[0029] The reason for setting the excitation warning temperature as the temperature to be monitored is to maintain a temperature below the critical temperature (below the excitation temperature) even if re-excitation becomes necessary due to a power outage or other reasons. In other words, during excitation, the temperature of the superconducting coil rises in order to allow current to flow, but if the temperature rise due to excitation makes it impossible to maintain a temperature below the excitation temperature, the excitation will cause the temperature to exceed the critical temperature and quench, making excitation impossible.

[0030] Therefore, the excitation warning temperature T1 is set to a temperature higher than the cooling temperature set for the superconducting coil 101, and to be approximately the same as the temperature obtained by subtracting the temperature rise due to excitation (referred to as the excitable temperature) T3 from the critical temperature T0, or to a temperature obtained by subtracting a predetermined margin from the excitable temperature T3. Since the temperature of the superconducting coil may differ depending on the temperature sensor, the excitation warning temperature may be set differently for each sensor. The margin is a temperature range set to ensure that the critical temperature is not reached even when excited, for example, it is set so that the excitation warning temperature T1 is about 1K lower than the excitable temperature T3.

[0031] When the excitation warning temperature described above is set (S1), the processor 200 (temperature management / alert unit 220) acquires temperature values ​​from each temperature sensor in the magnet (S2) and determines whether or not the excitation warning temperature has been exceeded (S3). If the refrigerator 104 maintains a constant performance, even if the excitation warning temperature is momentarily exceeded, the refrigerator 104 will keep the temperature inside the vacuum container 102 almost constant. If the performance of the refrigerator 104 deteriorates, the number of times the excitation warning temperature is exceeded will increase, and the temperature inside the vacuum container 102 will gradually tend to rise.

[0032] If the temperature values ​​from each temperature sensor exceed the excitation warning temperature for a predetermined period of time, a refrigerator replacement information message is issued (S4). Since the temperature inside the container fluctuates with small variations even when it is kept at a constant temperature, the predetermined period for determining whether or not the excitation warning temperature has been exceeded does not have to be a continuous period of time, but can be a cumulative period of time. For example, it may be determined that the temperature has been exceeded when the cumulative time above the excitation warning temperature reaches a predetermined period of time. This eliminates fluctuations between "yes" and "no" due to variations in temperature.

[0033] Furthermore, if there are multiple sensors, a warning may be issued when all of the temperature values ​​exceed the excitation warning temperature. Alternatively, the warning may be issued when, for example, the temperature value from a sensor at a predetermined location exceeds the excitation warning temperature, or when a predetermined percentage or more of the multiple sensors exceed the excitation warning temperature.

[0034] According to the superconducting coil device 10 of this embodiment, the processor 200 maintains a warning temperature related to a predetermined process that affects the temperature management of the superconducting coil device 10, specifically the excitation operation, and can provide appropriate warnings, such as refrigerator replacement information, based on the detected temperature of the superconducting coil. Furthermore, according to this embodiment, by setting a temperature lower than the excitation temperature (excitation warning temperature) as the warning temperature to be monitored, it is possible to maintain a state that allows for immediate response to temporary demagnetization and excitation, which may be necessary in response to power outages, for example.

[0035] The following describes a specific embodiment of the temperature control method using the superconducting coil device 10 of this embodiment. In the following description, Figures 1 and 2 will be referred to again as needed.

[0036] <Embodiment 1> In this embodiment, setting an excitation warning temperature in the processor 200 (S1) and determining whether the temperature value from each temperature sensor in the magnet exceeds the excitation warning temperature based on the excitation warning temperature (S2, S3) is the same as the processor processing described in the above embodiment (Figure 2).

[0037] In this embodiment, as shown in Figure 3, in S3, in order to determine the deterioration of the performance of the refrigerator 104, the processor 200 periodically acquires the temperature from the temperature sensor, for example, at a frequency of once per minute. A count value is assigned to each temperature, and the count is increased if it exceeds the excitation warning temperature, and decreased if it falls below the excitation warning temperature (S31, S32). The count value is stored in the processor 200. When the stored count reaches 24 hours' worth (count 1440) (S33), the processor 200 provides refrigerator replacement information (S4).

[0038] For example, when a predetermined number is reached, the processor 200 outputs a warning message such as "The time for refrigerator replacement is approaching" to the user control panel (display device 300) for operating the superconducting coil device 10, and also notifies the remote system 400 that a warning has been issued. The remote system 400 then notifies the service personnel 500 of the warning via email. Upon receiving this notification, the service personnel view the detailed status of the magnets, and if they confirm that the magnet temperature is continuously exceeding the excitation warning temperature, they take appropriate action, such as planning for refrigerator replacement.

[0039] According to this embodiment, by managing the exceedance of the excitation warning temperature using a count, it is possible to reliably determine when the excitation warning temperature has been exceeded while tolerating minute fluctuations in the temperature inside the container, and to provide information on the need to replace the refrigerator at an appropriate time.

[0040] <Embodiment 2> In this embodiment as well, as shown in the flow chart in Figure 3, monitoring the temperature from the temperature sensor (S1), counting up or down depending on whether the excitation warning temperature is exceeded (S2-S3), and providing refrigerator information when the count exceeds a predetermined number (S4) are the same as in Embodiment 1.

[0041] In this embodiment, in addition to or instead of refrigerator information, the excitation conditions are changed in advance if the excitation warning temperature is exceeded (S5). The excitation conditions to be changed are conditions that can suppress heat generation due to excitation, for example, the time from the start of excitation to the completion of excitation (excitation time). The excitation time can be changed by adjusting the amount of current flowing through the superconducting coil.

[0042] Excitation is performed by passing a predetermined current through the superconducting coil, which generates a small amount of heat. The amount of heat generated from the start to the completion of excitation is constant regardless of the excitation time. However, by increasing the excitation time, the temperature rise due to the generated heat is offset by the cooling effect that occurs during the extended time. As shown in the graph in Figure 4, with a standard excitation time, the temperature of the superconducting coil changes as shown by the dotted line, approaching the critical temperature T0 with excitation. However, by extending the excitation time, as shown by the solid line, the temperature rise is suppressed, and the temperature can be kept below the critical temperature T0. In other words, the peak of the temperature rise is lower than before the excitation time was not extended, so the temperature rise can be suppressed. (Change shown by the dotted line in Figure 4)

[0043] The processor 200 may automatically change the excitation time when the excitation warning temperature is exceeded, or it may change it when it approaches the excitation-ready temperature. An indicator of approaching the excitation-ready temperature could be, for example, when the sensor temperature reaches "(excitation-ready temperature × 9 + excitation warning temperature × 1) ÷ 10". Furthermore, the processor 200 may display a GUI on a display device, as shown in Figure 5, allowing the user to extend the excitation time or specify the extension period, and the excitation time may be changed according to the user's specification. Note that Figure 5 shows examples of UIs that allow the user to select whether to set the excitation time to standard or extended, and an example of a UI for specifying the excitation extension period, but a UI for selecting to stop excitation may also be displayed.

[0044] According to this embodiment, by changing the excitation conditions when the sensor temperature exceeds the excitation warning temperature or approaches the excitation-ready temperature, it is possible to suppress the temperature rise caused by the excitation of the superconducting coil device and reduce the risk of quenching, even when the refrigerator cannot be replaced immediately. Furthermore, with this embodiment, the excitation conditions can be changed not only when actually starting the excitation operation but also under normal conditions, which increases the user's sense of security when performing the excitation operation.

[0045] In addition, as a modification of this embodiment, it is also possible to omit the refrigerator information and only change the excitation time, and such modifications are also included in this embodiment.

[0046] <Application examples of Embodiments 1 and 2> In embodiments 1 and 2 described above, periodic temperature management based on the excitation warning temperature and changes to the refrigerator information and excitation conditions were explained. However, in this application example, in addition to those functions, when excitation starts, it is determined whether the superconducting coil temperature (sensor temperature) exceeds the excitation warning temperature, and if it does, a warning message is issued again.

[0047] In other words, in this application example, as shown in Figure 6, when the excitation start button is pressed while counting is being performed or after the refrigerator information is displayed (S5), if the sensor temperature exceeds the excitation warning temperature, or if the number of counts held in the processor 200 exceeds a predetermined number, similar to Embodiment 1, a second warning message is displayed to the user again (S6). The warning message is, for example, as shown in Figure 7, a message that confirms that the sensor temperature is approaching the upper limit of the excitation temperature and whether it is OK to perform excitation. The warning message is displayed on the control panel where the excitation start button is located, for example, in the form of a pop-up. At that time, it may be accompanied by a warning sound or voice.

[0048] Furthermore, a GUI displaying a message such as "Do you really want to energize?" along with "Yes" and "No" buttons is shown. If "Yes" is selected, energization begins; if "No" is selected, energization is not performed. If "Yes" is selected, a message prompting a change in the energization conditions (Figure 5) may be displayed as an alarm, similar to Embodiment 2 (S7).

[0049] According to this application example, by providing a warning message immediately before excitation indicating whether excitation can be continued under the set conditions, the user can be notified that performing excitation while the chiller is degraded carries a high risk of quenching. This allows the user to refrain from unnecessary excitation, thereby reliably avoiding quenching.

[0050] The superconducting coil device and its temperature control and alarm embodiments of the present invention have been described above. However, the superconducting coil device of the present invention can be applied to imaging devices such as MRI machines and nuclear magnetic resonance analyzers. Below, an embodiment of an MRI machine equipped with the superconducting coil device of the present invention will be described.

[0051] [Embodiment of an MRI device] First, let's describe the overview of the MRI device. The MRI device 20 is broadly composed of an imaging unit that performs imaging and a processor 200A that performs calculations such as device control and image generation. The main configuration of the imaging unit is the same as that of a known MRI device, and as shown in Figure 8, it is equipped with a static magnetic field generator that generates a uniform static magnetic field in the imaging space where the subject 50 is placed, a shim coil 111 that generates a magnetic field to correct the non-uniformity of the static magnetic field, a gradient magnetic field coil 112 that gives a magnetic field gradient to the static magnetic field, an RF transmitting coil 115 that applies a high-frequency magnetic field to the subject at a frequency (nuclear magnetic resonance frequency) determined by the strength of the static magnetic field, and an RF receiving coil 117 that detects the nuclear magnetic resonance signal generated from the subject by the application of the high-frequency magnetic field.

[0052] The shim coil 111 and the gradient coil 112 are connected to the shim power supply 114 and the gradient power amplifier (gradient power supply) 113, respectively. The RF transmit coil 115 is connected to an RF transmit section equipped with a high-frequency amplification circuit 116, etc., and the RF receive coil 117 is connected to an RF receive section equipped with a high-frequency power amplifier 118 and an A / D converter, etc.

[0053] The operation of the shim power supply 114, gradient magnetic field power supply, RF transmitter, and RF receiver is controlled by the processor 200A via a sequencer (not shown). Of the control performed by the processor 200A, the control of imaging via the sequencer and calculations such as image reconstruction using the nuclear magnetic resonance signal received by the RF receiver are realized by a computer functioning as the processor 200A in the illustrated embodiment.

[0054] The MRI apparatus of this embodiment uses the superconducting coil apparatus 10 described above as a static magnetic field generator. As shown in Figure 1, the superconducting coil apparatus 10 includes a coil unit 100 containing a superconducting coil 101 housed in a vacuum vessel 102, and a refrigerator 104 for cooling the superconducting coil 101. In Figure 8, the elements of the refrigerator 104 are shown as a cold head 1041 and a compressor unit 1042. The individual elements constituting the superconducting coil apparatus 10 are as described in the embodiment of the superconducting coil apparatus 10, and redundant explanations will be omitted.

[0055] The vacuum vessel 102 is equipped with a sensor connection terminal 109 to which a temperature sensor installed in the coil unit 100 is connected. The sensor connection terminal 109 is connected to the processor 200A (magnet control unit 230). The magnet control unit 230 receives the temperature detected by the temperature sensor, monitors the operating status of the superconducting coil 101, and controls the refrigerator 104 to manage the temperature.

[0056] In addition to controlling the imaging of the MRI device 20 and performing calculations using nuclear magnetic resonance signals, the processor 200A also has the function of controlling the static magnetic field generator (superconducting coil 101) and the function of providing necessary warnings to the user using temperature information from a temperature sensor.

[0057] Figure 9 shows a functional block diagram of the processor 200A that implements these functions. As shown in the figure, the processor 200A includes an imaging control unit 210 that controls imaging of the MRI device 20, a calculation unit 250 that performs various calculations such as image reconstruction, a display control unit 240 that generates and controls the display of display images shown on the display 30, a magnet control unit 230, and a temperature management / alarm unit 220. In Figure 8, the magnet control unit 230 and the temperature management / alarm unit 220 are shown as separate units for clarity, but they may be a single unit. The same applies to the other control units.

[0058] Furthermore, the processor 200A is equipped with a memory unit 260 that stores multiple temperatures (warning temperatures) necessary for managing the magnet temperature. The memory unit 260 may be the computer's internal memory, an external storage device, or composed of multiple memory units.

[0059] Since the imaging operation in the MRI apparatus 20 with the above configuration is the same as that of a known MRI apparatus, the explanation will be omitted here, and the following will mainly describe the functions of the temperature control and alarm unit 220 of the processor 200A.

[0060] The functions of the temperature management and notification unit 220 of the processor 200A of the present embodiment are the same as the temperature management functions of the processor 200A of the superconducting coil device 10 described above. That is, the functions described in Embodiments 1, 2 and their modifications are incorporated. Specifically, as shown in FIG. 2, the processor 200A of the MRI apparatus 20 of the present embodiment stores an excitation warning temperature, receives the temperature from a sensor installed in the vacuum vessel of the static magnetic field generator (superconducting coil device) based on the excitation warning temperature, and determines whether the sensor temperature has exceeded the excitation warning temperature for a certain period. When the excitation warning temperature is exceeded, refrigerator information is issued to notify that the refrigerator replacement time is approaching. In addition, the excitation conditions may be changed automatically or based on user specification. Further, when it is determined that the excitation warning temperature is exceeded during excitation, a warning may be issued again regarding whether to proceed with the excitation operation, and the excitation conditions may be changed at the same time.

[0061] In addition to the functions described above, the temperature management and notification unit 220 of the present embodiment can include control related to imaging operations that affect the temperature of the superconducting coil.

[0062] Once the superconducting coil 101 is excited, even if the temperature slightly exceeds the excitable temperature due to performance degradation of the refrigerator or the like (since the temperature is lower than the critical temperature), quenching does not occur and imaging can be performed. However, if the degradation continues, the temperature will exceed the imageable temperature, and there is a risk that the temperature will rise beyond the critical temperature due to various influences such as induced current from the gradient magnetic field during the imaging operation. In the present embodiment, by setting an imaging warning temperature as a second warning temperature in addition to the excitation warning temperature, reliable avoidance of quenching and maintenance of the imageable state are achieved.

[0063] Hereinafter, an embodiment of the operation of the processor 200A will be described, focusing on the control function related to the imaging operation of the temperature management and notification unit 220.

[0064] <Embodiment of Temperature Management in MRI Apparatus> <Embodiment 3> This embodiment is characterized by monitoring the imaging warning temperature, which is set to be below the imaging temperature, in order to maintain the state in which the MRI device 20 can take images, and issuing an alarm when it exceeds this temperature. The imaging warning temperature is maintained together with the excitation warning temperature of the superconducting coil device 10, and an alarm (first notification information) is issued based on the excitation warning temperature and an alarm (second notification information alarm) is issued based on the imaging warning temperature.

[0065] The imaging-capable temperature is the critical temperature minus the temperature change due to imaging, and the imaging warning temperature is the imaging-capable temperature minus a predetermined margin. Figure 11 shows the relationship between the imaging-capable temperature T4, the imaging warning temperature T2, and the excitation warning temperature T1. An example of the critical temperature, excitation warning temperature, and imaging warning temperature is shown at the bottom of Figure 11. However, this is a reference example and does not limit the present invention. The imaging-capable temperature may be stored in the memory unit as the critical temperature minus the maximum value of the "temperature change due to imaging." Alternatively, since the "temperature change due to imaging" differs depending on the imaging conditions, i.e., the pulse sequence used for imaging (sequence type, 2D sequence or 3D sequence, etc.), imaging parameters (TE, TR, FOV, number of slices, double speed), and the time required for imaging, a temperature rise estimation unit 223 is provided as shown in Figure 10, and the processor 200A (temperature rise estimation unit 223) estimates and stores the temperature change in various imaging scenarios in advance. The method for estimating the temperature change will be described later.

[0066] Furthermore, the temperature change due to imaging is generally smaller than the temperature change caused by excitation, which involves passing a large current through a superconducting coil. Therefore, the imaging temperature is higher than the excitation temperature. In other words, the imaging warning temperature is set higher than the excitation warning temperature. Consequently, since imaging immediately becomes impossible when the imaging temperature is exceeded, this warning is distinguished from the warning when the excitation warning temperature is exceeded and is considered a more urgent warning.

[0067] The operation of processor 200A will be explained below with reference to Figure 12.

[0068] When imaging conditions are determined, the processor 200A calculates the imaging-enabled temperature based on the temperature rise estimated from the imaging conditions and sets the imaging warning temperature in the memory unit 260 (S11). At the same time, it sets the excitation warning temperature. The excitation warning temperature may be retained by default.

[0069] Next, the temperature control and alarm unit 220 (coil temperature detection unit 221) monitors the sensor temperature of the superconducting coil 101 (S12). If the sensor temperature exceeds a predetermined period, a predetermined number of counts, or the excitation warning temperature, the alarm information generation unit 222 sends a refrigerator replacement information (first notification information: alarm 1) to the department (remote system 400) responsible for maintaining the superconducting coil 101 (S13, S14). This may also be done on the display 30 of the MRI device 20 during imaging.

[0070] The temperature management and alarm unit 220 continues to monitor the superconducting coil temperature by acquiring temperature information from the sensor even after alarm 1 is issued (S14). In this case as well, similar to embodiment 1, for example, the sensor temperature is acquired at a predetermined frequency, the counter is increased when it exceeds the imaging warning temperature, and the counter is decreased when it falls below the imaging warning temperature. When the counter reaches a predetermined number, it is determined that the imaging warning temperature has been exceeded for a predetermined time (S15). If it is determined that the sensor temperature of the superconducting coil 101 has exceeded the imaging warning temperature, the temperature management and alarm unit 220 issues a second notification (alarm 2) (S16). Alarm 2 may have the same content as alarm 1, but since the urgency of replacing the refrigerator is higher at the time alarm 2 is issued than at the time alarm 1 is issued, it is preferable to change the alarm to indicate this, for example, by changing the color of the message frame to a more attention-grabbing color than alarm 1, or by changing the content of the message to something that indicates a higher urgency than alarm 1, such as "The time for replacing the refrigerator is approaching." Alarm 2 is issued to the department (remote system 400) responsible for maintaining the superconducting coil 101. Similar to Alarm 1, the remote system notifies service personnel via email that an alert has occurred. Service personnel can then view the detailed status of the superconducting coil 101 and, if they confirm that the coil temperature is continuously exceeding the imaging warning temperature, they can plan for replacement of the refrigerator, among other actions. After taking action, the system returns to the original monitoring step (S17).

[0071] According to this embodiment, by setting and maintaining multiple temperatures as warning temperatures for managing the temperature of the superconducting coil 101, appropriate alarms can be issued according to each temperature. In particular, in cases of high urgency, maintenance can be carried out according to the urgency, such as refraining from imaging by the imaging device and immediately arranging for replacement of the refrigerator. This ensures the safe continuation of imaging operations.

[0072] In this embodiment, we have described a case in which both "refrigeration unit replacement information" (alarm 1) based on the excitation warning temperature and "refrigeration unit replacement information" (alarm 2) based on the imaging warning temperature are performed. However, the present invention also includes modifications in which the former is omitted and only the latter is performed.

[0073] <Embodiment 4> Embodiment 3 was configured such that the temperature management and alarm unit 220 would issue a warning, for example, a "refrigeration unit replacement information," if the imaging warning temperature was exceeded. However, this embodiment is characterized by issuing a message suggesting the imaging sequence and imaging conditions if the imaging warning temperature is exceeded at the start of imaging.

[0074] The following describes the processing of the temperature control and alarm unit 220 in this embodiment with reference to the flowchart in Figure 13. In this embodiment as well, the normal operation is the same as in Embodiment 3, setting the excitation warning temperature and the imaging warning temperature (S11), monitoring the sensor temperature (S12), and if the excitation warning temperature is exceeded for a predetermined time, a "refrigeration unit replacement information" is generated and the time or count of exceeding the imaging warning temperature is determined (S13, S15). If either warning temperature is exceeded, alarm 1 and alarm 2 regarding refrigeration unit replacement are issued (S14, S16).

[0075] In this embodiment, when imaging conditions are set in the imaging control unit 210 for imaging, the temperature management and alarm unit 220 first receives the set imaging conditions from the imaging control unit 210 and predicts the temperature rise of the superconducting coil 101 expected to occur as a result of the planned imaging. As described above, the temperature rise is determined by the imaging sequence, imaging parameters, etc. (collectively referred to as imaging conditions). As shown in Figure 14, the processor 200A has previously obtained predicted values ​​of the temperature rise (temperature rise data 263) for various imaging conditions using methods such as methods using measured values ​​or statistical values, simulation, or AI-based prediction based on empirical values, and stores these predicted values ​​in the storage unit 260 in association with the imaging conditions (imaging condition data 262). Measured values ​​can be stored in the recording unit, for example, by saving the temperature rise monitored by the temperature sensor when imaging is performed under various imaging conditions, and pre-recording them in association with each imaging condition.

[0076] The temperature management and alarm unit 220 estimates the imaging temperature using predicted temperature rise values ​​for each imaging condition and sets the imaging warning temperature based on that (S12). It also reads the temperature rise value associated with the planned imaging condition from the storage unit 260 and sets it as the predicted temperature rise value (S21). If the temperature rise data 263 for each imaging condition is not stored in advance, the predicted value is set to 0 (zero) or a fixed value such as the "maximum temperature change due to imaging" stored in the storage unit.

[0077] The temperature management and alarm unit 220 continuously acquires coil temperature information from the temperature sensor even before the imaging start button is pressed. After determining that the coil temperature has exceeded the imaging warning temperature (S15), when the operator (user) of the MRI device 20 presses the imaging start button (S22), the unit displays a message on the control console (display 30) of the MRI device 20 via the display control unit 240, such as confirmation of the imaging measurement or a change in imaging conditions (S23). If a predicted value for temperature rise is set, the unit can also suggest imaging conditions based on this predicted value or issue a pre-imaging warning.

[0078] Figure 15 shows an example of a message to be displayed on the control panel (display 30) of the MRI device 20. The upper part of Figure 15 shows a message to confirm whether to continue imaging. If "Yes" is selected from the GUI ("Yes" or "No") displayed with the message, imaging will continue; if "No" is selected, imaging will be stopped.

[0079] The message shown at the bottom of Figure 15 is a message to change the imaging conditions (FOV in the illustrated example), suggesting that the temperature rise be suppressed by changing the imaging conditions to increase the FOV. In this case, for example, if the user selects "Increase FOV by 10%", the FOV will be changed automatically and imaging will start. If "FOV" is selected as "Do not change FOV", imaging will start with the initially set settings. The changes to the imaging conditions are not limited to "FOV"; any condition that contributes to the temperature rise may be changed, such as the number of slices or slice thickness, or in the case of a series of imaging including multiple images, it may be changed to omit one of the multiple images, or a combination of these.

[0080] Note that the warning indicating that the temperature is approaching the upper limit for imaging (e.g., the upper part of Figure 15) and the warning regarding changes to imaging conditions (e.g., the lower part of Figure 15) may be displayed individually, but if "Continue imaging" ("Yes") is selected on the message screen shown in Figure 15, an additional message regarding changes to imaging conditions may be displayed.

[0081] According to this embodiment, even in the event of an operation that causes a temperature rise in the superconducting coil 101 during the operation of the imaging device equipped with the superconducting coil, an appropriate warning can be issued, ensuring the safe continuation of imaging operations. In particular, by presenting messages regarding imaging conditions, the user can be prompted to decide whether to continue imaging or to change the settings of the imaging conditions. For example, the user can reduce the gradient magnetic field strength that contributes to heat generation and suppress the temperature rise by increasing the FOV, which is an imaging condition.

[0082] In this embodiment, we have described a case in which monitoring based on the excitation warning temperature and refrigerator replacement information are performed together with monitoring based on the imaging warning temperature and warnings regarding the continuation of imaging. However, the present invention also includes modified cases in which the former (i.e., monitoring based on the excitation warning temperature and refrigerator replacement information) is omitted and only the latter is performed.

[0083] <Embodiment 5> Embodiment 4 was configured to suggest imaging sequences and imaging conditions when the imaging warning temperature was exceeded, but this embodiment is characterized by issuing only a "temperature rise warning".

[0084] The processing of the temperature control and alarm unit 220 in this embodiment will be explained below with reference to the flow chart in Figure 16. In this embodiment as well, the normal operation is the same as in Embodiment 3, setting the excitation warning temperature and the imaging warning temperature (S11), monitoring the sensor temperature (S12), and if the excitation warning temperature is exceeded for a predetermined time, a "refrigeration unit replacement information" is generated and the time or count of exceeding the imaging warning temperature is determined (S13, S15). If either warning temperature is exceeded, alarm 1 and alarm 2 regarding refrigeration unit replacement are issued (S14, S16).

[0085] The temperature management and alarm unit 220 continues to acquire coil temperature information from the temperature sensor even before the imaging start button is pressed. After determining that the coil temperature has exceeded the imaging warning temperature (S15), when the operator (user) of the MRI device 20 presses the imaging start button (S22), the unit displays a warning message indicating that the temperature is rising on the control console (display 30) of the MRI device 20 via the display control unit 240 (S23B).

[0086] The message displayed on the control panel (display 30) of the MRI device 20 will be, for example, a message like the one shown in Figure 15 (Display Example 1). If "Yes" is selected from the GUI ("Yes" or "No") displayed with the message, imaging will continue; if "No" is selected, imaging will be stopped.

[0087] <Application Examples> In the embodiment shown in Figure 13, a warning was given when the imaging start button is pressed while the coil temperature of the superconducting coil 101 exceeds the imaging warning temperature. However, if a predicted temperature rise value is set in advance for the imaging conditions, as shown by the dotted lines in Figures 13 and 16, even if the imaging warning temperature is not exceeded, when the imaging start button is pressed, the coil temperature to be reached during imaging is estimated from the coil temperature at that time and the set predicted temperature rise value. If the estimated temperature reaches the imaging warning temperature, a warning as shown in Figure 15 may be issued.

[0088] This application example allows for the identification of the magnitude of the quench risk when performing imaging with a degraded refrigeration unit. Specifically, before the second alarm 2, "Refrigeration Unit Replacement Information," is issued, the user can be informed at the time of pressing the imaging start button that the imaging warning temperature is approaching and that imaging may cause the temperature to reach the imaging warning temperature, thus allowing them to avoid imaging that would cause a large temperature rise.

[0089] Although embodiments of the superconducting coil device and MRI device of the present invention have been described above, the present invention is not limited to these embodiments. For example, elements and procedures included in each embodiment can be combined or rearranged as long as they do not conflict technically, and such embodiments are also included in the present invention. Furthermore, the configurations shown in the above embodiments and drawings, especially the numerical values, do not limit the present invention, and configurations with added or omitted known elements are also included in the present invention. [Explanation of Symbols]

[0090] 10: Superconducting coil device, 20: MRI device, 30: Display, 100: Coil unit, 101: Superconducting coil, 102: Vacuum vessel, 104: Refrigerator, 105: Excitation power supply, 200, 200A: Processor, 210: Imaging control unit, 220: Temperature control / alert unit, 230: Magnet control unit, 260: Memory unit, 400: Remote system

Claims

1. A helium-saving superconducting coil device comprising a superconducting coil housed in a container and at least one refrigerator thermally connected to the superconducting coil for cooling the superconducting coil, further comprising a processor that receives temperature information of the superconducting coil detected by a temperature sensor installed in the container and issues a notification to the user, The superconducting coil device is characterized in that the processor maintains a temperature below the excitation temperature at which the superconducting coil can be excited as an excitation warning temperature, and issues a first notification when the temperature of the superconducting coil detected by the temperature sensor exceeds the excitation warning temperature for a predetermined period of time or longer.

2. A superconducting coil device according to claim 1, The superconducting coil device is characterized in that the excitation temperature is the critical temperature of the superconducting coil minus the temperature rise due to heat generation during excitation of the superconducting coil, and the processor maintains an excitation warning temperature lower than the excitation temperature.

3. A superconducting coil device according to claim 1, The first notification information issued by the processor is information indicating a decrease in the cooling performance of the refrigerator, which is a superconducting coil device.

4. A superconducting coil device according to claim 1, The processor has a second warning temperature that is different from the excitation warning temperature, A superconducting coil device characterized in that, when the temperature of the superconducting coil detected by the temperature sensor exceeds the second warning temperature for a predetermined period of time or longer, it issues a second notification information different from the first notification information.

5. A superconducting coil device according to claim 4, The second warning temperature possessed by the aforementioned processor is a temperature higher than the excitation warning temperature. The superconducting coil device is characterized in that the processor issues information indicating the urgency of replacing the refrigerator as the second notification information.

6. A superconducting coil device according to claim 4, The superconducting coil is a static magnetic field generating coil for a magnetic resonance imaging apparatus. The second warning temperature possessed by the processor is an imaging warning temperature that is higher than the excitation warning temperature. The superconducting coil device is characterized in that the processor issues information relating to the continuation or modification of imaging by the magnetic resonance imaging device as the second notification information.

7. A superconducting coil device according to claim 6, The superconducting coil device is characterized in that the processor issues a proposal to change the imaging parameters of the imaging performed by the magnetic resonance imaging device as the second notification information.

8. A superconducting coil device according to claim 6, The superconducting coil device is characterized in that the processor issues a second notification, before the start of imaging by the magnetic resonance imaging device, that the temperature of the superconducting coil is at the imaging warning temperature.

9. A superconducting coil device according to claim 6, The superconducting coil device is characterized in that the processor estimates the temperature rise of the superconducting coil caused by imaging performed by the magnetic resonance imaging device before the magnetic resonance imaging device starts imaging, and issues a warning based on the estimated temperature information as the second notification information.

10. A superconducting coil device according to claim 1, The superconducting coil device is characterized in that the processor controls the operation of the excitation power supply when the temperature of the superconducting coil exceeds the excitation warning temperature for a predetermined period of time or longer.

11. A superconducting coil device according to claim 1, The superconducting coil device is characterized in that the processor issues the first notification information before the superconducting coil is excited when the temperature of the superconducting coil exceeds the excitation warning temperature.

12. A magnetic resonance imaging apparatus comprising a static magnetic field generating magnet and an imaging unit that generates nuclear magnetic resonance in atomic nuclei contained in a subject placed in the static magnetic field space generated by the magnet, thereby acquiring an NMR signal, The magnetic resonance imaging apparatus is a superconducting coil device as described in claim 1, wherein the static magnetic field generating magnet is a superconducting coil device.

13. A magnetic resonance imaging apparatus according to claim 12, The magnetic resonance imaging apparatus is characterized in that, when the temperature of the superconducting coil detected by the temperature sensor is at a predetermined temperature higher than the excitation warning temperature, the processor issues information relating to whether or not the imaging conditions performed by the imaging unit can be continued or changed.

14. A method for managing the temperature of a helium-saving superconducting coil device and issuing notification information according to the temperature, As a temperature for managing the superconducting coil, an excitation warning temperature is set based on the critical temperature of the superconducting coil and the temperature rise due to heat generation during excitation. A method characterized by issuing notification information regarding the replacement time of the refrigerator that cools the superconducting coil when the temperature of the superconducting coil detected by a temperature sensor exceeds the excitation warning temperature.

15. The method according to claim 14, As the temperature for managing the superconducting coil, a plurality of warning temperatures are set, including a first warning temperature and a second warning temperature higher than the first warning temperature, as the excitation warning temperature. A method characterized by issuing different alarms when the temperature of a superconducting coil detected by a temperature sensor exceeds a first warning temperature and when it exceeds a second warning temperature.

Images