Magnetic resonance imaging device and method for operating magnetic resonance imaging device

Abstract

The invention provides a magnetic resonance imaging apparatus and a method of operating the same. The subject of the invention is to detect a magnetic body existing in an imaging space and a periphery thereof with a simple structure and high precision. A magnetic resonance imaging device according to one embodiment of the present invention captures a magnetic resonance image of a subject, and is provided with: a high-frequency coil; a gradient magnetic field generating coil; a static magnetic field generating coil that is a superconducting coil and has an inductance greater than the inductance of the high-frequency coil and the inductance of the gradient magnetic field generating coil; an energization control unit that energizes the static magnetic field generating coil; a voltage measurement unit that measures a voltage between the current lead terminals of the static magnetic field generation coil; and a magnetic substance detection unit that detects a magnetic substance present in an imaging space of the magnetic resonance imaging apparatus and a magnetic substance present in the vicinity of the imaging space on the basis of a first voltage, which is a voltage measured in a state in which a first current smaller than a rated current at the time of imaging is applied to the static magnetic field generation coil.

Description

Technical Field

[0001] The present invention relates to a magnetic resonance imaging device and an operating method of the magnetic resonance imaging device, and more particularly to a technology for detecting magnetic bodies existing in an imaging space of a magnetic resonance imaging device and its surroundings. Background Art

[0002] Magnetic resonance imaging devices (MRI devices, MRI: Magnetic Resonance Imaging) have the property of image disturbance due to the presence of magnetic bodies. Therefore, a technology for detecting or inspecting magnetic bodies present near the MRI device is used. For example, Patent Document 1 describes detecting metal by detecting changes in electrical data of a gradient magnetic field coil provided in an MRI device, and Patent Document 2 describes detecting metal by using a radio frequency antenna device (high frequency coil) provided in an MRI device. Furthermore, Patent Document 3 describes determining whether a magnetic body is approaching by generating a magnetic field in a magnetic body detection coil provided separately from the MRI device.

[0003] Patent Document 1: Japanese Patent Application No. 2017-536864

[0004] Patent Document 2: Japanese Patent No. 6684832

[0005] Patent Document 3: Japanese Patent Application Publication No. 2007-289670

[0006] When detecting a magnetic body by a change in the electrical data (e.g., voltage) of a coil, the voltage change of the coil is proportional to the inductance. However, since the inductance of the gradient magnetic field coil or high-frequency coil of the MRI device is small, the voltage change based on the magnetic body is small, and therefore the magnetic body cannot be detected with high accuracy in the technologies of Patent Documents 1 and 2. Furthermore, if a magnetic body detection device is provided separately from the MRI device as in Patent Document 3, the system structure becomes complicated or large-scale.

[0007] As described above, the conventional technology cannot detect a magnetic body existing in the imaging space of an MRI apparatus and its vicinity with high accuracy using a simple configuration. Summary of the invention

[0008] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a magnetic resonance imaging apparatus and a method for operating the magnetic resonance imaging apparatus which can detect a magnetic body existing in an imaging space and its vicinity with high accuracy with a simple structure.

[0009] In order to achieve the above-mentioned purpose, the first mode of the present invention involves a magnetic resonance imaging device, which captures a magnetic resonance image of a subject, and the magnetic resonance imaging device comprises: a high-frequency coil; a gradient magnetic field generating coil; a static magnetic field generating coil, which has an inductance greater than the inductance of the high-frequency coil and the inductance of the gradient magnetic field generating coil and is a superconducting coil; an energization control unit, which energizes the static magnetic field generating coil; a voltage measuring unit, which measures the voltage between the current lead terminals of the static magnetic field generating coil; and a magnetic body detection unit, which detects a magnetic body existing in an imaging space of the magnetic resonance imaging device and a magnetic body existing near the imaging space based on a first voltage measured in a state where a first current smaller than a rated current during imaging is passed through the static magnetic field generating coil.

[0010] According to the first mode, since a static magnetic field generating coil having an inductance greater than that of the high frequency coil and the inductance of the gradient magnetic field generating coil and being a superconducting coil is used, the voltage change caused by the presence of the magnetic body is large even when the first current less than the rated current is passed, and the magnetic body existing in the imaging space and the magnetic body existing near the imaging space can be detected with high accuracy. In addition, the superconducting coil is also called a superconducting coil. In addition, since the static magnetic field generating coil provided by the magnetic resonance imaging device is used, it is not necessary to set a device different from the imaging device for detecting the magnetic body, and the structure of the device can be simplified. In addition, the "presence" of the magnetic body includes the case where the magnetic body or the subject having the magnetic body moves and enters the imaging space or its periphery (the same in the following modes). In addition, the "imaging space" is the space where the subject is located when the magnetic resonance image is captured, for example, in the case of a tunnel hole type device, it is the inside of the tunnel. In addition, in the first mode, "energizing" means to give energy by connecting electromagnetic induction or a power supply from the outside to the superconducting coil in a cooling state (superconducting state). Furthermore, a high frequency coil is also referred to as an RF coil (RF: radio frequency).

[0011] In the first and subsequent methods, for example, instruments or machines used in the vicinity of a magnetic resonance imaging device, items worn by a subject or a user (including a pacemaker or artificial joint in the subject or user) can be magnetic bodies to be detected.

[0012] The magnetic resonance imaging apparatus according to the second embodiment is configured such that, in the first embodiment, the magnetic body detection unit determines that a magnetic body is detected when at least one of the first voltage is greater than a threshold value and the time rate of change of the first voltage is greater than a reference value is satisfied. In the second embodiment, it is determined that "a magnetic body that affects imaging exists" under a prescribed condition.

[0013] The magnetic resonance imaging apparatus according to the third aspect is such that, in the second aspect, the energization control unit supplies a rated current to the static magnetic field generating coil when the first voltage does not satisfy the threshold value and the time change rate of the first voltage does not satisfy the reference value. In the third aspect, when the first voltage does not satisfy the threshold value and the time change rate of the first voltage does not satisfy the reference value, it can be determined that "the magnetic body that affects imaging does not exist in the imaging space and its periphery", and the energization control unit supplies a rated current to the static magnetic field generating coil so that the magnetic resonance image can be captured.

[0014] The magnetic resonance imaging device according to the fourth embodiment, in any one of the first to third embodiments, performs one or more of stopping the energization of the static magnetic field generating coil, stopping the movement of the subject to the imaging space, and notifying the detection of the magnetic body when the magnetic body detection unit detects the magnetic body. In the fourth embodiment, the response to the situation where it is judged that "a magnetic body that affects the imaging exists" is specified, and these responses can prevent the image from becoming disordered due to the influence of the magnetic body. In addition, the notification can be made by displaying on the display device, emitting voice, etc.

[0015] The magnetic resonance imaging apparatus according to a fifth aspect is any one of the first to fourth aspects, wherein the current supply control unit starts supplying the first current before the subject is moved to the imaging space. According to the fifth aspect, the magnetic substance can be detected before the subject is moved to the imaging space.

[0016] The magnetic resonance imaging device involved in the sixth mode, in any one of the first to fifth modes, further comprises: an information output unit, which outputs information indicating whether a magnetic body exists. The information output unit can directly output "whether a magnetic body exists" in characters or voice, or can output information (current passing through or voltage measured) that indirectly indicates "whether a magnetic body exists" in characters, numbers, charts, etc.

[0017] A magnetic resonance imaging apparatus according to a seventh aspect is a magnetic resonance imaging apparatus according to any one of the first to sixth aspects, further comprising an operation unit that receives an operation of instructing the energization control unit to energize the first current.

[0018] A magnetic resonance imaging apparatus according to an eighth aspect is a magnetic resonance imaging apparatus according to any one of the first to seventh aspects, wherein the magnetic body is a metal.

[0019] In order to achieve the above-mentioned object, in the working method of the magnetic resonance imaging device involved in the 9th mode of the present invention, the magnetic resonance imaging device comprises: a high-frequency coil; a gradient magnetic field generating coil; a static magnetic field generating coil, which has an inductance greater than the inductance of the high-frequency coil and the inductance of the gradient magnetic field generating coil and is a superconducting coil; and a processor, the magnetic resonance imaging device captures the magnetic resonance image of the subject, and the processor performs the following processing: energizing the static magnetic field generating coil; measuring the voltage between the current lead terminals of the static magnetic field generating coil; and based on the voltage measured in the state where the static magnetic field generating coil is passed through the first current smaller than the rated current when the imaging is performed, i.e., the first voltage, the magnetic body existing in the imaging space of the magnetic resonance imaging device and the magnetic body existing near the imaging space. According to the 10th mode, as in the 1st mode, the magnetic body existing in the imaging space and its surroundings can be detected with high precision with a simple structure. In addition, the working method involved in the 9th mode can also have a structure corresponding to the 2nd to 8th modes.

[0020] Effects of the Invention

[0021] As described above, according to the magnetic resonance imaging apparatus and the operating method of the magnetic resonance imaging apparatus of the present invention, it is possible to detect a magnetic body existing in an imaging space and its vicinity with high accuracy with a simple configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a diagram showing the configuration of a magnetic resonance imaging system.

[0023] Figure 2 It is a diagram showing the structure of a magnetic resonance imaging apparatus.

[0024] Figure 3 It is a diagram showing the structure of a static magnetic field generation source.

[0025] Figure 4 It is a diagram showing the functional structure of a processor.

[0026] Figure 5 It is a schematic diagram showing the detection status of magnetic body.

[0027] Figure 6 This is a diagram showing the current and voltage of the static magnetic field generating coil (when there is no magnetic body).

[0028] Figure 7 This is a diagram showing the current and voltage of the static magnetic field generating coil (when a magnetic body is present).

[0029] Explanation of symbols

[0030] A1-1st current, A2-rated current, V0-threshold. DETAILED DESCRIPTION

[0031] Hereinafter, the preferred embodiments of the magnetic resonance imaging device and the working method of the magnetic resonance imaging device according to the present invention will be described with reference to the accompanying drawings. In addition, in the accompanying drawings, for the convenience of description, the illustration of some components is sometimes omitted. Furthermore, the accompanying drawings do not represent the exact shape or size of the magnetic resonance imaging device.

[0032] [First embodiment]

[0033] [Structure of Magnetic Resonance Imaging Apparatus]

[0034] First, the structure of the magnetic resonance imaging device is described. Figure 1 As shown in FIG. 1 , the magnetic resonance imaging apparatus 100 according to the first embodiment includes an apparatus main body 101 and a bed device 300 .

[0035] The magnetic resonance imaging apparatus 100 is a device for obtaining a subject 110 (reference Figure 2 ) is a device for obtaining tomographic images. In this embodiment, it is an MRI device (MRI: Magnetic Resonance Imaging) that utilizes the nuclear magnetic resonance (NMR: Nuclear Magnetic Resonance) phenomenon. Figure 1 In the figure, as an example of a magnetic resonance imaging device 100 and a device body 101, a tunnel-type MRI device with a cylindrical gantry is shown. The device body 101 has a cylindrical tunnel 102 with its axial direction horizontal, and a static magnetic field is generated in the tunnel 102 to form an imaging space. The device body 101 is arranged in an electromagnetically shielded room, and a gradient magnetic field power supply 132, a sequencer 140, a high-frequency oscillator 151, a modulator 152, a high-frequency amplifier 153, a signal amplifier 162, an orthogonal phase detector 163, an A / D converter 164, and a control unit 170 are provided (see FIG. 1 ). Figure 2 ) is arranged outside the electromagnetically shielded room and is electrically connected to the device body 101 via a cable.

[0036] [Structure of Magnetic Resonance Imaging Apparatus]

[0037] Figure 2 1 is a diagram showing the structure of the magnetic resonance imaging apparatus 100. Figure 2 As shown, the magnetic resonance imaging apparatus 100 includes a static magnetic field generation source 120 , a gradient magnetic field generation unit 130 , a sequencer 140 , a high-frequency irradiation unit 150 , a signal detection unit 160 , and a control unit 170 .

[0038] like Figure 3As shown, the static magnetic field generating source 120 includes a power source 122 and a superconducting coil 124 (a coil for generating a static magnetic field). In the static magnetic field space containing the subject 110, if it is a vertical magnetic field mode, a uniform static magnetic field is generated in a direction orthogonal to the body axis of the subject 110, and if it is a horizontal magnetic field mode, a uniform static magnetic field is generated in the body axis direction of the subject 110. The static magnetic field generating source 120 is arranged around the subject 110. The current and voltage of the superconducting coil 124 are measured by an ammeter 126 and a voltmeter 128, and input to a processor 171 (control unit 170). In addition, the coil for generating a static magnetic field may be a normal conductive coil instead of a superconducting coil.

[0039] If you return to Figure 2 , the gradient magnetic field generating unit 130 includes a gradient magnetic field coil 131 (gradient magnetic field generating coil) which is superimposed on the static magnetic field space and generates a gradient magnetic field in the three-axis directions of X, Y, and Z in the coordinate system (stationary coordinate system) of the magnetic resonance imaging device 100, and a gradient magnetic field power supply 132 which drives each gradient magnetic field coil 131. The gradient magnetic field power supply 132 of each coil is driven according to the command, i.e., control, from the sequencer 140 described later, so that the gradient magnetic fields Gx, Gy, and Gz are generated in the three-axis directions of X, Y, and Z. During imaging, a slice direction gradient magnetic field pulse (Gs) is applied in a direction orthogonal to the slice plane (imaging section) to set the slice plane for the subject 110, and a phase encoding direction gradient magnetic field pulse (Gp) and a frequency encoding direction gradient magnetic field pulse (Gf) are applied in the remaining two directions orthogonal to the slice plane and orthogonal to each other, so as to encode the position information in each direction in the echo signal.

[0040] The sequencer 140 repeatedly applies high frequency magnetic field pulses (RF pulses) and gradient magnetic field pulses in a predetermined pulse sequence. The sequencer 140 operates under the control of the processor 171 and sends various commands, i.e., controls, required for data collection of tomographic images of the subject 110 to the gradient magnetic field generator 130, the high frequency irradiator 150, and the signal detector 160.

[0041] The high-frequency irradiation unit 150 irradiates the subject 110 with RF pulses so that the nuclear spins of the atoms constituting the living tissue of the subject 110 cause nuclear magnetic resonance. The high-frequency irradiation unit 150 includes a high-frequency oscillator 151, a modulator 152, a high-frequency amplifier 153, and an irradiation coil 154 (high-frequency coil) as a transmitting-side high-frequency coil. At the timing based on the instruction from the sequencer 140, the modulator 152 modulates the amplitude of the RF pulse output from the high-frequency oscillator 151, and the high-frequency amplifier 153 amplifies the amplitude-modulated RF pulse and supplies it to the irradiation coil 154 arranged close to the subject 110, thereby irradiating the subject 110 with electromagnetic waves.

[0042] The signal detection unit 160 detects an NMR signal, i.e., an echo signal, which is released by the nuclear magnetic resonance of the nuclear spins of the living tissue constituting the subject 110. The signal detection unit 160 includes a receiving coil 161 (high frequency coil), which is a receiving side high frequency coil, a signal amplifier 162, an orthogonal phase detector 163, and an A / D converter 164 (analog / digital converter). The response NMR signal induced in the subject 110 by the electromagnetic wave irradiated from the irradiation coil 154 is detected by the receiving coil 161 arranged close to the subject 110, and after being amplified by the signal amplifier 162, it is divided into two orthogonal system signals by the orthogonal phase detector 1.63 at the timing based on the instruction from the sequencer 140, and each is converted into a digital quantity by the A / D converter 1.64 and sent to the control unit 170.

[0043] The control unit 170 (processor) performs various data processing, displays and saves processing results, etc. The control unit 170 includes a processor 171 (processor), storage devices such as RAM 172A (RAM: random access memory) and ROM 172B (ROM: read only memory), an external storage device 180 such as an optical disk 181 or a magnetic disk 182, and an input / output unit 190. When the signal detection unit 160 receives a signal or data, the processor 171 uses the RAM 172A as a work area to perform processing such as signal processing and image reconstruction, and displays the result, i.e., a tomographic image of the subject 110, on the output device 200 and records it in the external storage device 180. When the processor 171 performs these processes, it can refer to the program or data recorded in the ROM 172B.

[0044] Furthermore, the control unit 170 can energize the superconducting coil 124 (static magnetic field generating coil) from the power supply 122 under the control of the processor 171, and measure the current passing therethrough and the voltage between the current lead terminals of the superconducting coil 124 using the ammeter 126 and the voltmeter 128. Furthermore, the control unit 170 (processor 171) detects the magnetic body based on these measurement results and outputs the results.

[0045] In this way, the processor 171 operates as the imaging control unit 171A, the power supply control unit 171B (power supply control unit), the voltage measurement unit 171C (voltage measurement unit), the magnetic body detection unit 171D (magnetic body detection unit), and the information output unit 171E (information output unit) (refer to Figure 4 ). The detection of magnetic bodies based on these parts will be described in detail later.

[0046] The input / output unit 190 inputs and outputs various control information of the magnetic resonance imaging apparatus 100 or control information of the processing performed by the control unit 170, and specifically, receives and displays the input of imaging parameters of the pulse sequence, etc. In addition, the input / output unit 190 receives an operation of instructing to energize the static magnetic field generating coil (first current, etc.), and outputs information indicating the energization state or the measured voltage, etc. The input / output unit 190 is composed of an input device 210 (operating unit) including a pointing device 211 such as a trackball, a mouse, a touch pad, a touch panel, and a keyboard 212, and an output device 200 (information output unit) including a display 201 such as a cathode ray tube (CRT) or a liquid crystal display (LCD) and a printer 202. The input device 210 and the output device 200 can be arranged close to each other, for example, the operator can interactively control the magnetic resonance imaging apparatus 100 by instructing the execution of various processing, etc., through the pointing device 211, while looking at the display 201. Furthermore, a touch panel that operates as the input device 210 may be arranged on the display surface of the display 201 , and input operations may be performed by selecting or operating the display content of the display 201 .

[0047] Furthermore, the input / output unit 190 may include devices for voice input / output, such as a microphone and a speaker, and the operator may operate these devices by voice via the microphone, or may provide information indicating the power-on state or the measured voltage, or notification of the detection of a magnetic body (for example, notification of terminating the power supply to the coil for generating a static magnetic field, terminating the movement of the subject into the imaging space, and detecting one or more magnetic bodies) by voice.

[0048] The subject 110 is placed on the top plate 310 of the bed device 300 and is moved by the bed moving device 220 (see Figure 2 ) is contained in a static magnetic field space serving as an imaging space. The transmitting side irradiation coil 154 and the gradient magnetic field coil 131 are disposed in a static magnetic field space accommodating the subject 110, in a manner opposing the subject 110 if a vertical magnetic field method is used, and in a manner surrounding the subject 110 if a horizontal magnetic field method is used. Furthermore, the receiving side receiving coil 161 is disposed in a manner opposing the imaging part of the subject 110, or surrounding the imaging part.

[0049] In addition, the nuclei that are imaged by current MRI apparatuses are widely used in clinical practice as hydrogen nuclei (protons), which are the main constituents of the subject 110. By imaging information related to the spatial distribution of proton density or the spatial distribution of relaxation time of an excited state, the morphology or function of the human head, abdomen, limbs, etc. can be imaged two-dimensionally or three-dimensionally.

[0050] [Example of coil inductance and generated voltage]

[0051] As described above, the magnetic resonance imaging device 100 includes the irradiation coil 154 and the receiving coil 161 (high frequency coil), the gradient magnetic field coil 131 (gradient magnetic field generating coil), and the superconducting coil 124 (static magnetic field generating coil). If an example of the inductance of these coils and the voltage generated in the coil when the magnetic body moves is shown, the inductance of the high frequency coil, the gradient magnetic field generating coil, and the static magnetic field generating coil are 1μH (H: Henry), 1mH, and 30H, respectively, and the generated voltages (relative values) are 0.001, 1, and 30000, respectively. In the case where the static magnetic field generating coil is a superconducting coil, the superconducting coil is, for example, wound with a superconducting wire for several thousand turns, so the inductance is large. In this way, the inductance of the static magnetic field generating coil is large, so the voltage generated by the magnetic body is also high, and it is suitable for detecting the magnetic body.

[0052] [Structure of the bed device]

[0053] The bed device 300 includes a top plate 310, a top plate holding portion 311, and a main body 340 for placing the subject 110. In the first embodiment, the bed device 300 is fixed to the main body 101, but the bed device 300 and the magnetic resonance imaging device 100 may be configured separately so as to be connectable to and detachable from the main body 101. The top plate 31.0 is held by the top plate holding portion 31.1 and is moved by the bed moving device 220 (see FIG. 21 ) in the magnetic resonance imaging device 100. Figure 2 ) can slide in or outside the imaging space. In addition, the bed device 300 has a top plate locking mechanism (not shown) that can lock the top plate 310 so that it cannot slide, or unlock the top plate 310 so that it can slide. In addition, the bed device 300 has a top plate lifting mechanism (not shown) (for example, it can be composed of a hydraulic jack, a universal arm, etc.) that can lift the top plate 310 and the top plate holding portion 311.

[0054] [Detection of magnetic substances]

[0055] Next, the detection of magnetic substances in the imaging space and its vicinity by the magnetic resonance imaging apparatus 100 will be described. Figure 5 This is a schematic diagram showing the state of detecting a magnetic body (only some components are shown). Figure 6 1 is a diagram showing the current and voltage of the superconducting coil 124 (static magnetic field generating coil) when there is no magnetic body in the imaging space and its vicinity. Figure 7 is a diagram showing the current and voltage of the superconducting coil 124 when a magnetic body exists in the imaging space or its vicinity. Figure 6 , Figure 7 The graph shown, the values ​​of current and voltage, whether or not a magnetic body is present, and the like are displayed on the display 201 .

[0056] First, a case where there is no magnetic substance in the imaging space or its vicinity will be described. Figure 5 Part (a) of FIG. 1 shows a state in which the subject 110 enters a space (examination room, etc.) in which the magnetic resonance imaging apparatus 100 is installed. The power supply control unit 171B (processor 171; power supply control unit) starts supplying a first current ( t = t0 ) smaller than the rated current during imaging to the superconducting coil 124 at this time (t = t0). Figure 6 The current A1 in part (a) of the test object 110 may not be entered into the room and the power-on may not be started at the same time. The voltmeter 176 (voltmeter measuring unit) measures the voltage V, and the information output unit 171E outputs information indicating the measured voltage to the display 201 (output device) or the like. These measurements and outputs continue until the end of the imaging. In addition, the first current can be set to less than half of the rated current, for example, but can also be set to different values ​​according to other conditions such as the detection accuracy of the magnetic body. Furthermore, the magnitude of the first current can also be set to be variable, and the power-on control unit 171B can pass the first current of a value corresponding to the user's operation.

[0057] Figure 5 Part (b) of FIG. 1 shows a state where the subject 110 is close to the magnetic resonance imaging apparatus 100 (time t=t1 to t2). Figure 5 Part (c) shows a state where the subject 110 lies on the top plate 310 and can be moved to the imaging space (time t= t2 ). Figure 6 This is an example of a case where there is no magnetic body in the imaging space and its vicinity. Therefore, even if the first current is passed, the voltage V of the superconducting coil 124 does not rise (refer to Figure 6 Part (b); the period from time t1 to t2).

[0058] In a state where the subject 110 can be moved to the imaging space ( Figure 5 (a); at time t = t2), the voltage V (first voltage) is less than the threshold value, and the time rate of change of the voltage V does not satisfy the reference value, so the power control unit 171B increases the current (during time t = t2 to t3) and passes the rated current ( Figure 6 The bed moving device 220 slides the top plate 310 to move the subject 110 to the imaging space ( Figure 5The state shown in part (d) of FIG. 1 ). Thus, a magnetic resonance image of the subject 110 can be captured. In addition, the information output unit 171E preferably outputs information indicating that a magnetic body does not exist or is not detected (a form of information indicating whether a magnetic body exists) to the display 201, etc. before the rated current is passed through the superconducting coil 124.

[0059] Next, the case where a magnetic body exists in the imaging space or its vicinity (for example, in an examination room where the apparatus main body 101 is installed or near the bed device 300) is described. The magnetic body here refers to an object possessed by the subject 110 (for example, a pacemaker, an artificial joint, etc.), but it may also be an item such as a machine or an instrument used near the magnetic resonance imaging apparatus 100. Furthermore, the magnetic body is, for example, a metal such as iron, but magnetic bodies other than metals also become detection targets. When such a magnetic body exists in the imaging space or its vicinity, if the first current is passed through the superconducting coil 124 (coil for generating a static magnetic field) (time t=t0~t1; Figure 7 (a) of the embodiment of the present invention), a voltage (first voltage) corresponding to the inductance is generated between the current lead terminals of the superconducting coil 124. Furthermore, the first voltage increases as the subject 110 approaches the magnetic resonance imaging apparatus 100 (that is, as the magnetic body approaches the magnetic resonance imaging apparatus 100) (time t1 to t4; Figure 5 Part (a) to (c) and Figure 7 (b) of the Figure 7 In the example shown, the first voltage becomes greater than the threshold value V0 at time t=t4, so the magnetic body detection unit 171D can determine that "a magnetic body that affects the image capture (causes an obstacle) exists in the image capture space or in the vicinity thereof." In this case, the information output unit 171E preferably outputs information indicating the presence of the magnetic body (a form of information indicating whether the magnetic body exists) to the display 201 or the like.

[0060] The magnetic substance detection unit 171D can be configured to detect the magnetic substance when the first voltage is greater than or equal to the threshold value and the time change rate of the first voltage is satisfied. Figure 7 In the example, when the change in the first voltage during the time t=t1-t4) is at least one of the values ​​above the reference value, it is determined that "a magnetic body is detected". The magnetic body detection unit 171D (processor 171) can, based on the determination (detection of a magnetic body), perform at least one of terminating the power supply to the superconducting coil 124 (coil for generating a static magnetic field), terminating the movement of the subject 110 to the imaging space, and notifying the detection of the magnetic body, thereby preventing imaging disturbances due to the presence of the magnetic body. The magnetic body detection unit 171D (processor 171, control unit 170) can perform more than one of the above-mentioned responses, or can perform all of the responses. Figure 7 In the example, at time t=t4, the first voltage becomes greater than or equal to the threshold value V0 ( Figure 7 (b) of FIG. 1 ), and accordingly, the control unit 170 (power-on control unit) stops powering the superconducting coil 124 (the current is zero at time t=L5; Figure 7 (a) of the Regulations).

[0061] As described above, in the magnetic resonance imaging apparatus 100 , it is preferable to start energizing the superconducting coil 124 (energizing the first current) before moving the subject 110 to the imaging space, so that prompt action can be taken when a magnetic body is detected.

[0062] In addition, when the conditions on the magnitude or time change rate of the first voltage are not met (when the first voltage does not meet the threshold value and the time change rate of the first voltage does not meet the reference value), the processor 171 (control unit 170) can judge that "there is no magnetic body" or "there is a magnetic body, but it will not affect the camera (cause an obstacle)" to pass the rated current through the superconducting coil 124 and transfer to the camera.

[0063] As described above, according to the magnetic resonance imaging apparatus 100 , a magnetic substance existing in the imaging space and a magnetic substance existing in the vicinity of the imaging space can be detected with high accuracy using a simple configuration.

[0064] [other]

[0065] In the magnetic resonance imaging apparatus 100 of the present embodiment, the processor 171 may include various processors (processors) as shown below in terms of hardware. The “various processors” include general-purpose processors that execute software (programs) and function as various processing units, i.e., CPUs (Central Processing Units), processors whose circuit structures can be changed after manufacturing, such as FPGAs (Field Programmable Gate Arrays), programmable logic devices (PLDs), and processors with circuit structures specially designed to execute specific processing, such as ASICs (Application Specific Integrated Circuits), i.e., dedicated circuits.

[0066] The processor 171 may be composed of one of these various processors, or may be composed of two or more processors of the same or different types (for example, multiple FPGAs, or a combination of a CPU and an FPGA). Furthermore, multiple processing units may be composed of one processor. As an example of a plurality of processing units composed of one processor, first, as represented by computers such as clients and servers, there is a method in which a processor is composed of a combination of one or more CPUs and software, and the processor functions as multiple processing units. Second, as represented by a system on chip (SoC), there is a method in which a processor is used that implements the functions of the entire system including multiple processing units using one IC (Integrated Circuit) chip. In this way, various processing units can be composed of one or more of the above-mentioned various processors as a hardware structure.

[0067] In addition, more specifically, the hardware structure of these various processors is a circuit (circuitry) composed of circuit elements such as semiconductor elements. In addition, when various processors operate, they can refer to programs or data recorded in non-temporary and tangible recording media such as ROM172B, and can use recording media such as RAM172A as a temporary work area during operation.

[0068] Furthermore, it is needless to say that the present invention is not limited to the above-described embodiment, and various modifications are possible.

Claims

1. A magnetic resonance imaging device for capturing a magnetic resonance image of a subject, the magnetic resonance imaging device comprising: High frequency coil; Coils for generating inclined magnetic fields; a static magnetic field generating coil having an inductance greater than that of the high frequency coil and the gradient magnetic field generating coil and being a superconducting coil; an energizing control unit for energizing the static magnetic field generating coil; a voltage measuring unit for measuring a voltage between current lead terminals of the static magnetic field generating coil; and The magnetic body detection unit detects a magnetic body existing in an imaging space of the magnetic resonance imaging apparatus and a magnetic body existing near the imaging space based on a first voltage which is measured when a first current smaller than a rated current during imaging is passed through a coil for generating a static magnetic field.

2. The magnetic resonance imaging apparatus according to claim 1, wherein: The magnetic substance detection unit determines that the magnetic substance is detected when at least one of the first voltage is equal to or greater than a threshold value and the time change rate of the first voltage is equal to or greater than a reference value is satisfied.

3. The magnetic resonance imaging apparatus according to claim 2, wherein: The current supply control unit supplies the rated current to the static magnetic field generating coil when the first voltage does not satisfy the threshold value and the time change rate of the first voltage does not satisfy the reference value.

4. The magnetic resonance imaging apparatus according to any one of claims 1 to 3, wherein: When the magnetic substance detection unit detects the magnetic substance, at least one of stopping the energization of the static magnetic field generating coil, stopping the movement of the subject to the imaging space, and notifying that the magnetic substance has been detected is performed.

5. The magnetic resonance imaging apparatus according to any one of claims 1 to 3, wherein: The current supply control unit starts supplying the first current before moving the subject to the imaging space. 6 . The magnetic resonance imaging apparatus according to claim 1 , further comprising an information output unit that outputs information indicating whether the magnetic substance exists. 7 . The magnetic resonance imaging apparatus according to claim 1 , further comprising an operation unit for receiving an operation of instructing the energization control unit to energize the first current.

8. The magnetic resonance imaging apparatus according to any one of claims 1 to 3, wherein: The magnetic body is metal.

9. A method for operating a magnetic resonance imaging device, the magnetic resonance imaging device comprising: a high frequency coil; a gradient magnetic field generating coil; a static magnetic field generating coil having an inductance greater than that of the high frequency coil and the gradient magnetic field generating coil and being a superconducting coil; and a processor, wherein the magnetic resonance imaging device captures a magnetic resonance image of a subject, The processor performs the following processing: energizing the static magnetic field generating coil; measuring the voltage between the current lead terminals of the static magnetic field generating coil; and Based on a first voltage measured when a first current smaller than a rated current during imaging is passed through the static magnetic field generating coil, magnetic bodies existing in an imaging space of the magnetic resonance imaging device and magnetic bodies existing near the imaging space are detected.

Images