Magnetic Resonance Imaging System

Abstract

To cool the gradient magnetic field coil unit more effectively. [Solution] The magnetic resonance imaging apparatus of the embodiment comprises a static magnetic field magnet, a gradient magnetic field coil unit, a cooling system, and a supply unit. The static magnetic field magnet stores a refrigerant. The gradient magnetic field coil unit is provided inside the static magnetic field magnet. The cooling system cools the gradient magnetic field coil unit. The supply unit supplies the refrigerant gas discharged from the static magnetic field magnet as the refrigerant vaporizes to the cooling system.

Description

Technical Field

[0001] The embodiments disclosed in this specification and the drawings relate to a magnetic resonance imaging apparatus.

Background Art

[0002] An actively shielded gradient coil unit (ASGC) included in a magnetic resonance imaging (MRI) apparatus is used for scanning a subject. When the temperature of the gradient coil rises due to the current supplied to the gradient coil unit, it may exceed the usable limit or the image quality may deteriorate due to the rise in the temperature of the iron shim provided in the gradient coil unit.

[0003] Conventionally, in order to reduce the temperature rise of the gradient coil unit, for example, measures such as providing a hollow conductor in the gradient coil unit are taken to improve the cooling efficiency.

[0004] However, measures such as providing a hollow conductor may increase management such as water quality maintenance and lead to cost increases.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem that the embodiments disclosed herein and in the drawings aim to solve is to cool the gradient coil unit more effectively. However, the problems that the embodiments disclosed herein and in the drawings aim to solve are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described later can also be positioned as other problems. [Means for solving the problem]

[0007] The magnetic resonance imaging apparatus of this embodiment comprises a container, a gradient magnetic field coil unit, and a supply unit. The container houses a static magnetic field magnet that generates a static magnetic field. The container stores a refrigerant for cooling the static magnetic field magnet. The gradient magnetic field coil unit generates a gradient magnetic field. The cooling system cools the gradient magnetic field coil unit. The supply unit supplies the refrigerant vaporized in the container to the gradient magnetic field unit. [Brief explanation of the drawing]

[0008] [Figure 1] A diagram showing an example configuration of MRI device 1. [Figure 2] A perspective view showing an example configuration of the gradient magnetic field coil unit 108. [Figure 3] A diagram showing an example configuration of the shim tray 106. [Figure 4] A diagram showing an example of helium gas flow. [Figure 5] A cross-sectional view showing an example configuration of the gradient magnetic field coil unit 108. [Figure 6] A flowchart showing an example of the processing performed by MRI device 1. [Modes for carrying out the invention]

[0009] The magnetic resonance imaging apparatus of this embodiment will be described below with reference to the drawings.

[0010] Figure 1 shows an example of the configuration of an MRI device 1. In Figure 1, the MRI device (magnetic resonance imaging device) 1 comprises a magnet stand 101 and a patient bed 116. In this embodiment, the longitudinal direction of the top plate 117 of the patient bed 116 is the Z-axis direction, the axis direction perpendicular to the Z-axis direction and horizontal to the floor is the X-axis direction, and the axis direction perpendicular to the Z-axis direction and perpendicular to the floor is the Y-axis direction. The magnet stand 101 comprises a static magnetic field magnet 102, a gradient magnetic field coil unit 108, and an RF coil 115. The internal configuration of the magnet stand 101 is shown in a longitudinal cross-sectional view. The static magnetic field magnet 102 is housed in a container, and the container is provided with a storage tank containing liquid helium, which is a refrigerant for cooling the static magnetic field magnet 102.

[0011] The gradient magnetic field coil unit 108 is installed inside the magnet mount 101. The gradient magnetic field coil unit 108 includes a main coil 103 and a shield coil 104, and generates a gradient magnetic field. Between the main coil 103 and the shield coil 104 are a shim tray 106 and a shim member 107. Figure 1 shows the state of the gradient magnetic field coil unit 108 before it is sealed. Passive shimming is performed with the gradient magnetic field coil unit 108 not sealed and the shim tray 106 removable.

[0012] The MRI apparatus 1 comprises a gradient power supply 122, a transmitting circuit 123, a receiving circuit 124, a patient control circuit 125, a sequence control circuit 126, and a computer 131. The MRI apparatus 1 does not include a subject P (e.g., a human body such as a patient). The components within the sequence control circuit 126 and the computer 131 may be integrated or separated as appropriate.

[0013] The static magnetic field magnet 102 has a generally cylindrical shape. The static magnetic field magnet 102 generates a static magnetic field in a bore (the space inside the cylinder of the static magnetic field magnet 102) that includes the imaging area of ​​the subject P. The static magnetic field magnet 102 may be a superconducting magnet or a permanent magnet. The static magnetic field magnet 102 is provided with a storage tank containing liquid helium, which is a coolant used to cool the static magnetic field magnet 102.

[0014] The storage tank is connected to the exhaust port 160 (Figure 4) via piping. The static magnetic field magnet 102 receives a large amount of energy when scanning the subject P, but is kept below a certain temperature by being cooled by the liquid helium stored in the storage tank. Some of the liquid helium that has cooled the static magnetic field magnet 102 boils off and becomes helium gas. The boiled-off helium gas is supplied to the exhaust port 160 through the quench piping and discharged to the outside of the magnet stand 101. The destination of the helium gas discharged from the storage tank can be switched from the exhaust port 160 to the gradient magnetic field coil unit 108 via the helium gas circulation unit 150 (Figure 4). Helium is an example of a refrigerant, and helium gas is an example of a refrigerant gas.

[0015] The gradient magnetic field coil unit 108 also has a roughly cylindrical shape and is held inside the static magnetic field magnet 102 by a support structure such as vibration-damping rubber. The gradient magnetic field coil unit 108 has a main coil 103 that applies (generates) gradient magnetic fields in the mutually orthogonal X, Y, and Z directions by current supplied from the gradient magnetic field power supply 122, and a shield coil 104 that cancels the leakage magnetic field of the main coil 103.

[0016] The main coil 103 is sometimes called the inner coil. The shield coil 104 is sometimes called the outer coil. The main coil 103 and the shield coil 104 are formed, for example, by forming a coil pattern on a generally cylindrical non-conductive, non-magnetic material and then molding it with resin or the like. A shim tray 106 is inserted between the main coil 103 and the shield coil 104. The shim tray 106 houses shim members (also called iron shims, metal shims, etc.) 107 for correcting magnetic field non-uniformity within the bore. Further details of the gradient magnetic field coil unit 108 will be explained later.

[0017] The bed 116 includes a top plate 117 on which the subject P is placed. Under the control of the bed control circuit 125, the top plate 117 is inserted into the cavity (imaging aperture) of the gradient magnetic field coil unit 108 with the subject P placed thereon. Usually, the bed 116 is installed such that its longitudinal direction is parallel to the central axis of the static magnetic field magnet 102. The bed control circuit 125 drives the bed 116 to move the top plate 117 in the longitudinal direction and the vertical direction under the control of the computer 131.

[0018] The RF coil 115 is arranged inside the gradient magnetic field coil unit 108, receives the supply of RF pulses (RF pulses corresponding to the Larmor frequency determined by the type of the target atom and the magnetic field strength) from the transmission circuit 123 to generate a high-frequency magnetic field, receives the nuclear magnetic resonance signal emitted from the subject P due to the influence of the high-frequency magnetic field, and outputs the received nuclear magnetic resonance signal to the reception circuit 124. The RF coil 115 may be configured to be divided into a transmission coil and a reception coil.

[0019] The reception circuit 124 detects the nuclear magnetic resonance signal output from the RF coil 115 and generates nuclear magnetic resonance data based on the detected nuclear magnetic resonance signal. Specifically, the reception circuit 124 generates nuclear magnetic resonance data by digitally converting the nuclear magnetic resonance signal received by the RF coil 115. The reception circuit 124 transmits the generated nuclear magnetic resonance data to the sequence control circuit 126. The reception circuit 124 may be provided on the side of the magnet gantry 101.

[0020] The sequence control circuit 126 performs imaging of the subject P by driving the gradient magnetic field power supply 122, the transmission circuit 123, and the reception circuit 124 based on the sequence information transmitted from the computer 131. The sequence information is information that defines the procedure for performing imaging. The sequence information defines the strength of the current supplied by the gradient magnetic field power supply 122 to the main coil 103, the timing of supplying the current, the strength of the RF pulse supplied by the transmission circuit 123 to the RF coil 115, the timing of applying the RF pulse, the timing at which the reception circuit 124 detects the magnetic resonance signal, and the like. For example, the sequence control circuit 126 is realized by a processor.

[0021] As a result of driving the gradient magnetic field power supply 122, the transmission circuit 123, and the reception circuit 124 to image the subject P, the sequence control circuit 126 receives magnetic resonance data from the reception circuit 124. The sequence control circuit 126 transfers the received magnetic resonance data to the computer 131.

[0022] The computer 131 performs overall control of the MRI apparatus 1, generation of images, and the like. The computer 131 includes, for example, a memory 132, an input device 133, a display 134, a processing circuit 135, and a flow path switching unit 140. The processing circuit 135 includes, for example, an interface function 136, a control function 137, an image generation function 138, and a flow path control function 139.

[0023] Each processing function performed by the above interface function 136, control function 137, image generation function 138, and flow path control function 139 is stored in the memory 132 in the form of a program executable on the computer 131. The processing circuit 135 is a processor that reads out and executes the program to realize the functions corresponding to the respective programs. In other words, the processing circuit 135 in the state of having read out each program has each function shown in the processing circuit 135 of FIG. 1.

[0024] The processing circuit 135 realizes these functions, for example, by having the hardware processor execute a program stored in memory (storage circuit) 132. A hardware processor refers to circuits such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), Application Specific Integrated Circuit (ASIC), or programmable logic device (e.g., Simple Programmable Logic Device (SPLD) or Complex Programmable Logic Device (CPLD), or Field Programmable Gate Array (FPGA)). Instead of storing the program in memory 132, the hardware processor may be configured to directly incorporate the program into its circuitry. In this case, the hardware processor realizes the functions by reading and executing the program incorporated into the circuitry. The hardware processor is not limited to being a single circuit; it may be composed of multiple independent circuits combined to form a single hardware processor, each realizing a different function. Alternatively, multiple components may be integrated into a single hardware processor to realize each function.

[0025] The transmitting circuit 123, receiving circuit 124, and bed control circuit 125, etc., are similarly composed of electronic circuits such as the hardware processor described above.

[0026] The processing circuit 135 transmits sequence information to the sequence control circuit 126 via the interface function 136 and receives magnetic resonance data from the sequence control circuit 126. Upon receiving the magnetic resonance data, the processing circuit 135, which has the interface function 136, stores the received magnetic resonance data in the memory 132. The magnetic resonance data stored in the memory 132 is then placed in k-space by the control function 137. As a result, the memory 132 stores k-space data.

[0027] Memory 132 stores magnetic resonance data received by processing circuit 135 having interface function 136, k-space data arranged in k-space by processing circuit 135 having control function 137, and image data generated by processing circuit 135 having image generation function 138. For example, memory 132 can be a semiconductor memory element such as RAM (Random Access Memory) or flash memory, a hard disk, or an optical disk.

[0028] The input device 133 receives various instructions and information inputs from the operator. The input device 133 is, for example, a pointing device such as a mouse or trackball, a selection device such as a mode switch, or an input device such as a keyboard. The input device 133 is an interface that receives input. The display 134 displays a GUI (Graphical User Interface) for receiving input of imaging conditions for imaging the subject P, or images generated by the processing circuit 135 which has an image generation function 138, under the control of the processing circuit 135 which has a control function 137. The display 134 is, for example, a display device such as a liquid crystal display.

[0029] The processing circuit 135, through its control function 137, performs overall control of the MRI device 1, controlling imaging, image generation, image display, etc. For example, the processing circuit 135, which has the control function 137, receives input of imaging conditions (imaging parameters, etc.) via the GUI and generates sequence information according to the received imaging conditions. The processing circuit 135, which has the control function 137, also transmits the generated sequence information to the sequence control circuit 126.

[0030] The processing circuit 135 reads k-space data from memory 132 using the image generation function 138, and generates an image by applying reconstruction processing such as Fourier transform to the read k-space data. The processing circuit 135 controls the flow path switching unit 140 using the flow path control function 139. The flow path control function 139 is an example of a flow path control unit. The control of the flow path switching unit 140 by the flow path control function 139 will be explained further later.

[0031] Figure 2 is a perspective view showing an example configuration of a gradient magnetic field coil unit 108. In Figure 2, multiple slots 105a are provided between the main coil 103 and the shield coil 104 of the gradient magnetic field coil unit 108 at approximately equal intervals in the circumferential direction. The slots 105a are formed, for example, by the inner wall of a tubular shim tray guide 105 (Figure 4) with a rectangular cross-section. The number of slots 105a is not limited to those shown.

[0032] Slots 105a are through-holes formed with openings toward both end faces of the gradient coil unit 108, extending almost the entire length of the gradient coil unit 108 in the longitudinal direction (long axis direction). A shim tray 106 is inserted into each slot 105a, and each shim tray 106 is fixed to approximately the center of the gradient coil unit 108. The shim trays 106 are made of a resin, which is a non-magnetic and non-conductive material, and are generally rod-shaped.

[0033] Figure 3 shows an example of the configuration of the shim tray 106. In Figure 3, a plurality of pockets 106a are formed continuously along the longitudinal direction of the shim tray 106. The number of pockets 106a is not limited to that shown. Each pocket 106a houses the necessary number of shim members 107 at the necessary locations for the purpose of homogenizing the static magnetic field in the imaging space within the bore. The shim members 107 are thin metal plates (typically silicon steel plates) about the size of a business card.

[0034] Figure 4 shows an example of helium gas flow. The static magnetic field magnet 102 is equipped with a storage tank in which liquid helium is stored. The liquid helium is boiled off into helium gas by induction heating (Gradient Coil Induced Heating, hereafter GCIH) by the gradient magnetic field coil unit 108 during scanning. The helium gas is discharged from the magnet base 101 and supplied to the flow path switching section 140.

[0035] The flow path switching unit 140 is connected to the helium gas circulation unit 150 and the exhaust port 160 via quench piping, and the boiled-off helium gas is supplied to either the helium gas circulation unit 150 or the exhaust port 160 through the flow path switching unit 140. The flow path switching unit 140 is controlled by the flow path control function 139, which switches the supply destination of the helium gas between the helium gas circulation unit 150 (cooling system) and the exhaust port 160 (exhaust system). The flow path switching unit 140 is an example of a supply unit.

[0036] The helium gas circulation unit 150 supplies helium gas supplied by the flow path switching unit 140 to the gradient magnetic field coil unit 108. The helium gas supplied to the gradient magnetic field coil unit 108 flows through the piping inside the gradient magnetic field coil unit 108 and is discharged to the helium gas circulation unit 150. The helium gas circulation unit 150 supplies the helium gas discharged by the gradient magnetic field coil unit 108 to the exhaust port 160. The helium gas circulation unit 150 may also supply a portion of the helium gas discharged by the gradient magnetic field coil unit 108 to the flow path switching unit 140.

[0037] Figure 5 is a cross-sectional view showing an example configuration of the gradient magnetic field coil unit 108. In Figure 4, the Z-axis (axial) ends of the main coil 103 and the shield coil 104 are sealed, for example, by the side plate 109. The main coil 103 and the shield coil 104 are appropriately supported and fixed at various points so that a space is formed between them.

[0038] Coil conductors are embedded inside the main coil 103 and the shield coil 104, respectively. A tubular shim tray guide 105, for example with a rectangular cross-section, which houses a shim tray 106 inside, is supported in the space sandwiched between the main coil 103 and the shield coil 104. When a non-magnetic and non-conductive refrigerant is supplied to and fills this space, the refrigerant can flow in from both ends of the shim tray guide 105 in the Z-axis direction, and the outer and inner walls of the shim tray guide 105 are in direct contact with the refrigerant. The shim tray guide 105 may have holes or slits penetrating its inner and outer walls to facilitate the entry of the refrigerant into the interior, or it may be formed only of a frame that guides the four corners of the shim tray 106.

[0039] A refrigerant circulation unit 111 and a helium gas circulation unit 150 are provided near the gradient magnetic field coil unit 108. The refrigerant circulation unit 111 circulates a non-magnetic and non-conductive refrigerant within the gradient magnetic field coil unit 108. The helium gas circulation unit 150 circulates helium gas supplied by the flow path switching unit 140 within the gradient magnetic field coil unit 108.

[0040] The gradient magnetic field coil unit 108 is provided with a first refrigerant pipe 111a, a second refrigerant pipe 111b, a third refrigerant pipe 111c, a first quench pipe 151, a second quench pipe 152, and a third quench pipe 153. One end of the first refrigerant pipe 111a and one end of the third refrigerant pipe 111c are connected to the refrigerant circulation section 111.

[0041] The other end of the first refrigerant pipe 111a is connected to the approximate center in the Z-axis direction of the space in which the shim tray 106 is housed (hereinafter referred to as the housing space). The other end of the third refrigerant pipe 111c is connected to one end of the housing space, and one end of the second refrigerant pipe 111b is connected to the other end of the housing space. The other end of the second refrigerant pipe 111b is connected to the approximate center in the Z-axis direction of the third refrigerant pipe 111c. The approximate center in the Z-axis direction of the housing space corresponds to the magnetic field center of the space within the gradient magnetic field coil unit 108. The refrigerant supplied by the refrigerant circulation unit 111 is introduced into the housing space from the first refrigerant pipe 111a and returns to the refrigerant circulation unit 111 via the second refrigerant pipe 111b and the third refrigerant pipe 111c.

[0042] One end of the first quench pipe 151 and one end of the third quench pipe 153 are connected to the helium gas circulation section 150. The other ends of the first quench pipe 151 and the third quench pipe 153 are connected to the coil cooling circuit provided in the gradient magnetic field coil unit 108 and the iron shim cooling circuit (hereinafter referred to as the cooling circuit) provided in the space where the shim tray 106 is housed.

[0043] The quench piping connecting the static magnetic field magnet 102, the gradient magnetic field coil unit 108, and the exhaust port 160, as well as the first quench piping 151 to the third quench piping 153 provided on the gradient magnetic field coil unit 108, include a cooling system and an exhaust system. The exhaust system is a system for exhausting the closed gas, which is the vaporized helium that has cooled the static magnetic field magnet 102. The cooling system is a system through which helium gas that cools the gradient magnetic field coil unit 108 flows. The exhaust system is composed of quench piping connecting the flow path switching section 140 and the exhaust port 160. The cooling system is composed of the first quench piping 151 to the third quench piping 153 and a cooling circuit.

[0044] One end of the second quench pipe 152 is connected to the cooling circuit. The other end of the second quench pipe 152 is connected to the third quench pipe 153. Helium gas supplied by the helium gas circulation unit 150 is introduced into the cooling circuit from the first quench pipe 151 and returns to the helium gas circulation unit 150 via the second quench pipe 152 and the third quench pipe 153.

[0045] The first refrigerant pipe 111a, the second refrigerant pipe 111b, and the third refrigerant pipe 111c are connected by penetrating the walls of the main coil 103 and the side plate 109 while maintaining the airtightness of the space between the main coil 103 and the shield coil 104. The same applies to the first quench pipe 151, the second quench pipe 152, and the third quench pipe 153. The refrigerant circulation unit 111 and the helium gas circulation unit 150 circulate the refrigerant and helium gas while cooling the refrigerant so that they maintain predetermined temperatures.

[0046] In Figure 4, the refrigerant supply and discharge ports are located at the bottom of the gradient coil unit 108, and the helium gas supply and discharge ports are located at the top of the gradient coil unit 108. However, these supply and discharge ports may be located at any appropriate position on the gradient coil unit 108. The number of these supply and discharge ports can also be increased. Some or all of the cooling piping may be located in the housing space or at other locations on the gradient coil unit 108. By supplying helium gas to the cooling circuit, the cooling efficiency of the gradient coil unit 108 can be increased compared to cooling with refrigerant alone.

[0047] Next, the processing of the MRI apparatus 1 of the embodiment will be described. Figure 6 is a flowchart of an example of the processing of the MRI apparatus 1. In Figure 6, the process of imaging a subject P by the MRI apparatus 1 is described. First, the MRI apparatus 1 inserts the bed 116 on which the subject P is placed into the magnet stand 101, and the scanning of the subject P begins (step S101).

[0048] While the subject P is being scanned, the static magnetic field magnet 102 is cooled by liquid helium stored in the reservoir. As the static magnetic field magnet 102 cools, some of the helium boils off and becomes helium gas. The helium gas is supplied from the static magnetic field magnet 102 to the flow path switching unit 140.

[0049] Immediately after the scan begins, the temperature of the gradient coil unit 108 is not high, so the flow path control function 139 sets the destination of the helium gas supply by the flow path switching unit 140 to the exhaust port 160 (step S103). Subsequently, the flow path control function 139 in the processing circuit 135 of the MRI device 1 determines whether or not the ASGC cooling conditions for cooling the gradient coil unit 108 have been met (step S105).

[0050] As the scan of subject P progresses, the gradient coil unit 108 becomes hot. To cool the hot gradient coil unit 108, helium gas is supplied to the gradient coil unit 108 when the ASGC cooling conditions are met. The ASGC cooling conditions are determined, for example, based on the imaging conditions when imaging the subject.

[0051] The imaging conditions include, for example, at least one of the sequence frequency, duty cycle, or current peak value. For example, GCIH tends to increase near the resonant frequency generated in the MRI apparatus 1, such as the thermal shield provided on the gradient coil unit 108 or the magnet staircase 101, or the staircase support system supporting the magnet staircase 101.

[0052] The SGC cooling condition is met, for example, when the sequence frequency is near the resonant frequency. The SGC cooling condition is met, for example, when the current peak value is such that the rate of increase in the internal pressure of the magnet exceeds a predetermined pressure. The flow path control function 139 determines, for example, whether the difference between the sequence frequency and the resonant frequency is within a predetermined first threshold, and whether the current peak value exceeds a preset second threshold. The flow path control function 139 determines that the SGC cooling condition is met if the difference between the sequence frequency and the resonant frequency is within the first threshold, or if the current peak value exceeds the second threshold.

[0053] If the flow path control function 139 determines that the ASGC cooling conditions have been met, it controls the flow path switching unit 140 so that the helium gas is supplied to the gradient magnetic field coil unit 108 (step S107). If the flow path control function 139 determines that the ASGC cooling conditions have not been met, it skips step S107 and does not control the flow path switching unit 140, maintaining the helium gas supply to the exhaust port 160.

[0054] Next, the flow path control function 139 determines whether the scan of subject P is complete (step S109). If the flow path control function 139 determines that the scan of subject P is complete, the MRI device 1 terminates the process shown in Figure 6. If it determines that the scan is not complete, the flow path control function 139 determines whether the ASGC cooling termination condition has been met (step S111). The ASGC cooling termination condition is an example of a termination condition.

[0055] The ASGC cooling termination conditions are those that may cause a malfunction in the gradient magnetic field coil unit 108. For example, the ASGC cooling termination conditions include the amount of heat supplied to the gradient magnetic field coil unit 108 by helium gas exceeding a predetermined amount, or the helium gas flow rate exceeding a predetermined amount.

[0056] To increase the helium gas flow rate, for example, the first quench pipes 151 to the third quench pipes 153 need to be thick enough to withstand the pressure during quenching. Also, condensation is more likely to occur in the first quench pipes 151 to the third quench pipes 153 and the gradient magnetic field coil unit 108.

[0057] Alternatively, low-temperature embrittlement can damage the metals in the first quench pipes 151 to the third quench pipes 153 and the gradient magnetic field coil unit 108. Furthermore, even after the internal pressure of the first quench pipes 151 to the third quench pipes 153 increases due to GCIH, and the load is sequentially reduced, helium gas may continue to flow through the first quench pipes 151 to the third quench pipes 153, causing noise.

[0058] To avoid these problems, the flow path control function 139, when it determines that the ASGC cooling stop condition has been met, sets the helium gas supply destination to the exhaust system (exhaust port 160) and prevents helium gas from being supplied to the gradient coil unit 108 (step S113). When the flow path control function 139 determines that the ASGC cooling stop condition has not been met, it skips the process in step S113 and maintains the state in which helium gas is supplied to the gradient coil unit 108.

[0059] Next, the flow path control function 139 determines whether the scan of subject P is complete (step S115). If it determines that the scan is not complete, the flow path control function 139 returns to step S105. If the flow path control function 139 determines that the scan of subject P is complete, the MRI device 1 terminates the process shown in Figure 6.

[0060] In this embodiment, the MRI apparatus 1 supplies helium gas, which is boiled off by the cooling of the static magnetic field magnet 102, to the gradient magnetic field coil unit 108 and uses it to cool the gradient magnetic field coil unit 108. Therefore, the gradient magnetic field coil unit 108 can be cooled more effectively.

[0061] In this embodiment, the MRI apparatus 1 supplies helium gas to the gradient coil unit 108 when the ASGC cooling conditions based on sequence conditions are met. Therefore, helium gas can be appropriately supplied when cooling of the gradient coil unit 108 is required. In this embodiment, the MRI apparatus 1 stops supplying helium gas to the gradient coil unit 108 when the ASGC cooling stop conditions are met. Therefore, malfunctions caused by overcooling of the gradient coil unit 108 can be suppressed.

[0062] In the above embodiment, the flow path control function 139 causes the flow path switching unit 140 to switch the helium gas supply destination between the gradient coil unit 108 and the exhaust port 160. Alternatively, the MRI device may adjust the amount of helium gas supplied to the gradient coil unit 108 and the exhaust port 160, respectively.

[0063] In this case, the flow path control function 139 may cause the flow path switching unit 140 to adjust the amount of helium gas supplied to the gradient coil unit 108 and the exhaust port 160, respectively, based on, for example, the imaging conditions of the subject P or the sequence conditions for the generation of refrigerant gas. In the above embodiment, the flow path switching unit 140 switches the destination of the helium gas supply between the gradient coil unit 108 and the exhaust port 160, but it may also be a supply unit that supplies helium gas to the gradient coil unit 108 without having a switching function.

[0064] According to at least one embodiment described above, the gradient coil unit can be cooled more effectively by having a static magnetic field magnet in which a refrigerant is stored, a gradient magnetic field coil unit provided within the static magnetic field magnet, a cooling system through which the refrigerant gas that cools the gradient magnetic field coil unit flows, and a supply unit that supplies the refrigerant gas discharged from the static magnetic field magnet as the refrigerant vaporizes to the cooling system.

[0065] While several embodiments have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0066] 1 MRI machine 101 Magnetic Stand 102 Static magnetic field magnet 103 Main coil 104 Shielded Coil 105 Sim Tray Guide 105a slot 106 sim tray 106a Pocket 107 Shim member 108 Gradient Magnetic Field Coil Unit 109 Side panel 111 Refrigerant circulation section 111a First refrigerant piping 111b 2nd refrigerant pipe 111c Third Refrigerant Piping 115 RF coils 116 berths 117 Top plate 122 Gradient magnetic field power supply 123 Transmitter Circuit 124 Receiving Circuit 125 Bed control circuit 126 Sequence control circuit 131 Computer 132 memory 133 Input device 134 displays 135 Processing Circuit 136 Interface Functions 137 Control Functions 138 Image generation function 139 Flow path control function 140 Flow path switching section 150 Helium gas circulation section 151 First Quench Piping 152 Second Quench Piping 153 Third Quench Piping 160 exhaust port P Subject

Claims

1. A container housing a static magnetic field magnet that generates a static magnetic field, and a container storing a refrigerant for cooling the static magnetic field magnet, A gradient magnetic field coil unit that generates a gradient magnetic field, The system includes a supply unit that supplies the refrigerant vaporized in the container to the gradient magnetic field coil unit. Magnetic resonance imaging device.

2. The supply unit supplies the refrigerant to at least one of the following: a coil cooling circuit that cools the coils included in the gradient magnetic field coil unit, or an iron shim cooling circuit that cools the iron shims included in the gradient magnetic field coil unit. The magnetic resonance imaging apparatus according to claim 1.

3. The magnetic resonance imaging apparatus is equipped with an exhaust system that exhausts the refrigerant vaporized in the container to the outside of the magnetic resonance imaging apparatus. The supply unit includes a flow path switching unit that switches the destination of the refrigerant vaporized in the container between the gradient magnetic field coil unit and the exhaust system. The magnetic resonance imaging apparatus according to claim 1.

4. The flow path switching unit switches the flow path switching unit based on the imaging conditions for imaging the subject. The magnetic resonance imaging apparatus according to claim 3.

5. The imaging conditions include at least one of the sequence frequency or current peak value. The flow path switching unit switches the supply destination to the exhaust system when the difference between the sequence frequency and the resonance frequency generated in the magnetic resonance imaging apparatus is within a predetermined threshold, or when the current peak value exceeds a second threshold. The magnetic resonance imaging apparatus according to claim 4.

6. The flow path switching unit switches the supply destination of the refrigerant to the exhaust system when a shutdown condition is met that could cause a malfunction in the gradient magnetic field coil unit. The magnetic resonance imaging apparatus according to claim 3.

7. The aforementioned refrigerant contains helium. The magnetic resonance imaging apparatus according to claim 1.

Images