Magnetic resonance imaging apparatus

Abstract

To execute an imaging sequence on an optimized condition while driving a gradient magnetic field generation system safely.SOLUTION: A magnetic resonance imaging apparatus includes a sequence adjusting unit and a sequence control unit. The sequence adjusting unit predicts magnet inner pressure or magnet temperature when executing an imaging sequence on the basis of the imaging sequence of magnetic resonance imaging, and relationships between drive frequency of a gradient magnetic field coil and the magnet inner pressure or magnet temperature of a static magnetic field magnet, and adjusts the imaging sequence on the basis of the prediction result. The sequence control unit executes the imaging sequence adjusted by the sequence adjusting unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] A magnetic resonance imaging (MRI) device magnetically excites the nuclear spins of a subject with a radio frequency (RF) signal at the Larmor frequency, and reconstructs an image from the nuclear magnetic resonance (NMR) signal generated by this excitation. The MRI device is equipped with a gradient coil that applies a gradient magnetic field to the imaging space in which the subject is placed, thereby adding spatial position information to the MR signal. This gradient coil vibrates due to the Lorentz force when a pulse current is repeatedly supplied during imaging. The gradient coil also creates a leakage magnetic field to the outside. When the vibration of the gradient coil propagates into the magnet, or when vibrations due to eddy currents caused by the leakage magnetic field occur inside the magnet, the magnet generates heat, and the liquid helium evaporates, causing the internal pressure of the superconducting magnet to rise and the heat to be transmitted to the superconducting wire, which may cause the superconducting magnet to quench. This phenomenon is called gradient coil induced heating (GCIH).

[0003] On the other hand, it is difficult to accurately predict quenching due to GCIH depending on the imaging sequence. Therefore, to prevent GCIH, the risk of the internal pressure rise rate of the superconducting magnet is suppressed by using a sequence that is off the vibration resonance point of the gradient coil, or the specifications of the sequence at the vibration resonance point are lowered to safely operate the gradient magnetic field generation system of the MRI device. As described above, in the MRI apparatus, the imaging sequence is executed under non-optimized conditions in order to safely drive the gradient magnetic field generating system. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-76263 A Summary of the Invention [Problem to be solved by the invention]

[0005] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to execute an imaging sequence under optimized conditions while safely driving a gradient magnetic field generating system. However, the problems to be solved by the embodiments disclosed in this specification and the drawings 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]

[0006] A magnetic resonance imaging apparatus according to an embodiment includes a sequence adjustment unit and a sequence control unit. The sequence adjustment unit predicts a magnet internal pressure or magnet temperature during execution of an imaging sequence of magnetic resonance imaging based on a relationship between a driving frequency of a gradient coil and a magnet internal pressure or magnet temperature of a static magnetic field magnet, and adjusts the imaging sequence based on the prediction result. The sequence control unit executes the imaging sequence adjusted by the sequence adjustment unit. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a magnetic resonance imaging apparatus according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of the structure of the magnetic resonance imaging apparatus according to the embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of the relationship between frequency and magnet internal pressure in the magnetic resonance imaging apparatus according to the embodiment. [Figure 4] FIG. 4 is a flowchart illustrating a processing procedure of the sequence adjustment processing by the magnetic resonance imaging apparatus according to the embodiment. [Diagram 5] FIG. 5 is a diagram showing an example of an equivalent circuit used in the sequence adjustment process by the magnetic resonance imaging apparatus according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of a magnetic resonance imaging (MRI) apparatus will be described in detail with reference to the drawings. In the following description, components having substantially the same functions and configurations are denoted by the same reference numerals, and repeated description will be given only when necessary.

[0009] (Embodiment) Fig. 1 is a diagram showing a control configuration of a magnetic resonance imaging apparatus 1 of this embodiment. As shown in Fig. 1, the magnetic resonance imaging apparatus 1 has a gantry 11, a bed 13, a gradient magnetic field power supply 21, a transmission circuit 23, a reception circuit 25, a bed driving device 27, a sequence control circuit 29, and a host computer 50. The host computer is an example of a data processing device.

[0010] 1, the gantry 11 has a static magnetic field magnet 41 and a gradient magnetic field coil 43. The static magnetic field magnet 41 and the gradient magnetic field coil 43 are housed in a housing 111 of the gantry 11. A bore 112 having a hollow shape is formed in the housing 111 of the gantry 11. A transmitting coil 45 and a receiving coil 47 are arranged in the bore 112 of the gantry 11. The gantry 11 may be called a "gantry."

[0011] The static magnetic field magnet 41 has a hollow, approximately cylindrical shape, and generates a static magnetic field inside the approximately cylinder. For example, a permanent magnet, a superconducting magnet, or a normal conducting magnet is used as the static magnetic field magnet 41. Here, the central axis of the static magnetic field magnet 41 is defined as the Z axis, the axis perpendicular to the Z axis is defined as the Y axis, and the axis horizontally perpendicular to the Z axis is defined as the X axis. The X axis, the Y axis, and the Z axis form an orthogonal three-dimensional coordinate system.

[0012] The gradient coil 43 is a coil unit attached to the inside of the static magnetic field magnet 41 and formed in a hollow, approximately cylindrical shape. For example, an ASGC (Active Shield Gradient Coil) is used as the gradient coil 43. The gradient coil 43 generates a gradient magnetic field by receiving a current from the gradient magnetic field power supply 21. More specifically, the gradient coil 43 has three coils corresponding to the X-axis, Y-axis, and Z-axis that are orthogonal to each other. The three coils form a gradient magnetic field whose magnetic field strength changes along each of the X-axis, Y-axis, and Z-axis. The gradient magnetic fields along each of the X-axis, Y-axis, and Z-axis are synthesized to form a slice selection gradient magnetic field Gs, a phase encoding gradient magnetic field Gp, and a frequency encoding gradient magnetic field Gr that are orthogonal to each other in a desired direction. The slice selection gradient magnetic field Gs is used to arbitrarily determine an imaging section (slice). The phase encoding gradient magnetic field Gp is ​​used to change the phase of a magnetic resonance signal (hereinafter referred to as an MR signal) according to a spatial position. The frequency encoding gradient magnetic field Gr is used to change the frequency of the MR signal depending on the spatial position. In the following description, the gradient direction of the slice selection gradient magnetic field Gs is the Z axis, the gradient direction of the phase encoding gradient magnetic field Gp is ​​the Y axis, and the gradient direction of the frequency encoding gradient magnetic field Gr is the X axis.

[0013] The gradient magnetic field power supply 21 supplies a current to the gradient magnetic field coil 43 in accordance with a sequence control signal from the sequence control circuit 29. The gradient magnetic field power supply 21 supplies a current to the gradient magnetic field coil 43, thereby causing the gradient magnetic field coil 43 to generate gradient magnetic fields along the X-axis, Y-axis, and Z-axis. The gradient magnetic field is superimposed on the static magnetic field formed by the static magnetic field magnet 41 and applied to the subject P.

[0014] The transmission coil 45 is disposed, for example, inside the gradient magnetic field coil 43, and receives RF pulses from the transmission circuit 23 to generate a high-frequency magnetic field.

[0015] The transmission circuit 23 supplies an RF pulse to the transmission coil 45 in order to apply the RF pulse to the subject P via the transmission coil 45 in order to excite the target protons present in the subject P. The RF pulse corresponds to a Larmor frequency determined by the type of the target atomic nucleus and the strength of the magnetic field. The RF pulse vibrates at a resonance frequency specific to the target protons, exciting the target protons. An MR signal is generated from the excited target protons and detected by the reception coil 47.

[0016] The receiving coil 47 is fixed inside the bore 112. The receiving coil 47 receives an MR signal emitted from the target protons present inside the imaging region under the action of an RF pulse. The received MR signal is supplied to the receiving circuit 25 via a wired or wireless connection.

[0017] The receiving circuitry 25 receives MR signals generated from excited target protons via the receiving coil 47. The receiving circuitry 25 processes the received MR signals to generate digital MR signals. The digital MR signals can be expressed in k-space defined by spatial frequencies. Therefore, hereinafter, the digital MR signals will be referred to as k-space data. The k-space data is a type of raw data used for image reconstruction. The k-space data is supplied to a host computer 50 via a wired or wireless connection.

[0018] The bed 13 is installed adjacent to the gantry 11. The bed 13 has a top plate 131 and a base 133. The subject P is placed on the top plate 131. The base 133 supports the top plate 131 so that it can move along the Z-axis direction. The base 133 also supports the top plate 131 so that it can slide along each of the X-axis, Y-axis, and Z-axis. A bed driving device 27 is housed in the base 133. The bed driving device 27 moves the top plate 131 under the control of a sequence control circuit 29. The bed driving device 27 may include any motor, such as a servo motor or a stepping motor.

[0019] The sequence control circuit 29 has, as hardware resources, a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) and memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The sequence control circuit 29 synchronously controls the gradient magnetic field power supply 21, the transmission circuit 23, and the reception circuit 25 based on an imaging protocol determined by an imaging protocol setting function 511 of the processing circuit 51, performs magnetic resonance imaging on the subject P according to a pulse sequence corresponding to the imaging protocol, and collects k-space data regarding the subject P.

[0020] As shown in FIG. 1, the host computer 50 is a computer having a processing circuit 51 , a memory 52 , a display 53 , an input interface 54 and a communication interface 55 .

[0021] The processing circuitry 51 has a processor such as a CPU as a hardware resource. The processing circuitry 51 functions as the core of the magnetic resonance imaging apparatus 1. For example, the processing circuitry 51 executes various programs to have an imaging protocol setting function 511, a data acquisition function 512, an image generation function 513, an image processing function 514, a display control function 515, a sequence adjustment function 516, and a sequence control function 517.

[0022] 1, the imaging protocol setting function 511, the data acquisition function 512, the image generation function 513, the image processing function 514, the display control function 515, the sequence adjustment function 516, and the sequence control function 517 are realized by a single processing circuit 51. However, a processing circuit may be configured by combining a plurality of independent processors, and each processor may execute a program to realize each function. Also, the imaging protocol setting function 511, the data acquisition function 512, the image generation function 513, the image processing function 514, the display control function 515, the sequence adjustment function 516, and the sequence control function 517 may be called an imaging protocol setting circuit, a data acquisition circuit, an image generation circuit, an image processing circuit, a display control circuit, a sequence adjustment circuit, and a sequence control circuit, respectively, and may be implemented as individual hardware circuits. The above description of each function executed by the processing circuit 51 is the same in each of the following embodiments and modified examples.

[0023] The term "processor" used in the above description means a circuit such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or an ASIC, a programmable logic device (e.g., a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), and a Field Programmable Gate Array (FPGA)). When the processor is, for example, a CPU, the processor realizes a function by reading and executing a program stored in a memory. On the other hand, when the processor is an ASIC, instead of storing a program in a memory, the function is directly incorporated as a logic circuit in the circuit of the processor. Note that each processor in this embodiment is not limited to being configured as a single circuit for each processor, and may be configured as a single processor by combining multiple independent circuits to realize the function. Furthermore, the multiple components in FIG. 1 may be integrated into a single processor to realize the function. The above description of the "processor" is also applicable to the following embodiments and modified examples.

[0024] The memory 52 is a storage device such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or an integrated circuit storage device that stores various information. The memory 52 may also be a drive device that reads and writes various information from and to a portable storage medium such as a CD-ROM drive, a DVD drive, or a flash memory. For example, the memory 52 stores a trained model, k-space data, MR image data, a control program, and the like.

[0025] The display 53 displays various information using a display control function 515. For example, the display 53 displays an MR image generated by an image generation function 513, an MR image generated by an image processing function 514, an imaging protocol setting screen, etc. As the display 53, for example, a CRT display, a liquid crystal display, an organic EL display, an LED display, a plasma display, or any other display known in the art can be appropriately used.

[0026] The input interface 54 includes an input device that accepts various commands from a user. Examples of the input device that can be used include a keyboard, a mouse, various switches, a touch screen, a touch pad, and the like. Note that the input device is not limited to devices that have physical operation parts such as a mouse and a keyboard. For example, an example of the input interface 54 also includes an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the magnetic resonance imaging apparatus 1 and outputs the received electrical signal to various circuits.

[0027] The communication interface 55 is an interface that connects the magnetic resonance imaging apparatus 1 to a workstation, a PACS (Picture Archiving and Communication System), a HIS (Hospital Information System), a RIS (Radiology Information System), etc. via a LAN (Local Area Network) etc. The communication interface 55 transmits and receives various information to and from the connected workstation, PACS, HIS, and RIS.

[0028] Next, each function executed by the processing circuit 51 will be described in detail. The processing circuitry 51 sets an imaging protocol for magnetic resonance imaging by an imaging protocol setting function 511 in response to a user instruction via the input interface 54 or automatically. The imaging protocol is a set of various imaging parameters for one magnetic resonance imaging. As the imaging parameters, various parameters that are set directly or indirectly to perform magnetic resonance imaging, such as the type of pulse sequence, the type of k-space filling method, the imaging time, the repetition time (TR), and the echo time (TE), can be applied. As the pulse sequence, for example, EPI (echo planar imaging) is used.

[0029] The processing circuitry 51 acquires MR data related to a processing target such as a subject P by using a data acquisition function 512. MR data is a general term for k-space data, MR image data, and hybrid data. The k-space data may be original k-space data, or may be data obtained by performing any data processing such as data compression processing, resolution decomposition processing, data interpolation processing, and resolution synthesis processing on the original k-space data. The hybrid data is data obtained by performing a Fourier transform or an inverse Fourier transform along at least one axis of the k-space data.

[0030] The processing circuitry 51 reconstructs an MR image of the subject P based on the MR data acquired from the receiving circuitry 25 by using the image generating function 513. The processing circuitry 51 performs, for example, a Fourier transform on the MR data arranged in the k-space or the frequency space to generate an MR image defined in real space. Instead of or in combination with the Fourier transform, an iterative reconstruction method or a reconstruction method using a machine learning model may be performed. The processing circuitry 51 that realizes the image generating function 513 is an example of a reconstruction unit.

[0031] The processing circuitry 51 performs various image processing on the MR image using the image processing function 514. For example, the processing circuitry 51 performs image processing such as volume rendering, surface rendering, pixel value projection processing, MPR (Multi-Planer Reconstruction) processing, and CPR (Curved MPR) processing.

[0032] The processing circuitry 51 displays various information on the display 53 using the display control function 515. For example, the processing circuitry 51 displays on the display 53 an MR image generated by the image generation function 513, an MR image generated by the image processing function 514, an imaging protocol setting screen, and the like.

[0033] The processing circuit 51 estimates the energy that causes the magnet internal pressure rise of the static magnetic field magnet 41 that occurs during the execution of the imaging sequence using a circuit model that takes into account GCIH (Gradient Coil Induced Heating) by using a sequence adjustment function 516, and adjusts the imaging sequence before the execution of the imaging sequence based on the estimation result. The processing circuit 51 that realizes the sequence adjustment function 516 is an example of a sequence adjustment unit. GCIH is a phenomenon in which a pulse current is repeatedly supplied to the gradient magnetic field coil 43 during imaging, causing the gradient magnetic field coil 43 to vibrate due to the Lorentz force, and the helium container 63 generates heat due to the vibration, causing the liquid helium to heat up and vaporize, thereby increasing the magnet internal pressure. If the heat generation continues, there is a risk of causing a quench in which the superconducting coil 65 exceeds the critical temperature and becomes a normal conductive state. In recent years, the frequency used and the magnetic field applied have become stronger, and the influence of GCIH cannot be ignored.

[0034] Next, the principle by which GCIH occurs will be explained in detail. Fig. 2 is a diagram showing the internal configuration of the static magnetic field magnet 41. Fig. 2 shows the area surrounded by the dashed line in Fig. 1. Fig. 2 is a cross-sectional view showing a cross section from the center line of the bore 112 toward the radially outward direction. The R direction in Fig. 2 indicates a direction from the center line of the bore 112 toward any direction included in the XY plane. In other words, the structure is the same whether the R direction in Fig. 2 coincides with the X axis in Fig. 1 or the R direction in Fig. 2 coincides with the Y axis in Fig. 1.

[0035] As shown in FIG. 2, the static magnetic field magnet 41 includes a vacuum vessel 61 , a radiation shield 62 , a helium vessel 63 , a support structure 64 , and a superconducting coil 65 .

[0036] The vacuum vessel 61 is a housing that forms the exterior of the static magnetic field magnet 41. The helium vessel 63 is provided inside the vacuum vessel 61. The radiation shield 62 is attached between the vacuum vessel 61 and the helium vessel 63. It provides thermal insulation between the vacuum vessel 61 and the helium vessel 63. The support structure 64 and the superconducting coil 65 are provided inside the helium vessel 63. The support structure 64 is fixed to the helium vessel 63 and supports the superconducting coil 65. The inside of the helium vessel 63 is filled with liquid helium to keep the superconducting coil 65 in a superconducting state.

[0037] During imaging, when a pulse current is repeatedly supplied to the gradient coil 43, Lorentz force is generated, causing mechanical vibration of the gradient coil 43. When the gradient coil 43 vibrates, the vibration of the gradient coil 43 is transmitted to the radiation shield 62, causing the radiation shield 62 to vibrate. In the radiation shield 62, eddy currents are generated as the radiation shield 62 vibrates in a static magnetic field, and a magnetic field is generated by the eddy currents. When a magnetic field is generated by the eddy currents in the radiation shield 62, the magnetic field interlinks with the support structure 64 inside the helium container 63, generating heat inside the helium container 63. The generated heat is then transmitted to the liquid helium, causing the liquid helium to evaporate, and the internal pressure of the helium container 63 increases. In addition, a magnetic field is generated by the eddy currents generated in the support structure 64, and the generated magnetic field interlinks with the radiation shield 62, causing a new eddy current to be generated in the radiation shield 62. During imaging, such heat generation and internal pressure rise occur repeatedly in the helium container 63 until the driving of the gradient magnetic field coil 43 is completed. Then, when the amount of heat generated in the helium container 63 becomes large, the temperature of the superconducting coil 65 exceeds the critical temperature and the coil can no longer maintain superconductivity, and the coil is quenched, releasing the evaporated helium to the outside.

[0038] Furthermore, during imaging, when a leakage magnetic field of the gradient magnetic field generated by the gradient magnetic field coil 43 occurs in the radiation shield 62, an eddy current flows in the radiation shield 62, and the eddy current causes the radiation shield 62 to vibrate. The vibration of the radiation shield 62 in the static magnetic field generates an eddy current, which repeatedly generates heat and increases in internal pressure in the helium container 63, as described above. The increase in the magnet internal pressure of the static magnetic field magnet 41 is considered to be proportional to the heat input (heat generation) into the magnet due to scanning. For this reason, when the rate of increase in the magnet internal pressure per unit time reaches a certain value, if scanning is continued as is, the temperature of the superconducting wire will rise to a level that causes a quench. Therefore, the rate of increase in the internal pressure per unit time is a measure of the possibility of a quench occurring.

[0039] In this way, the mechanical vibration of the gradient coil 43 is physically transmitted to the radiation shield 62, and the radiation shield 62 vibrates due to the leakage magnetic field, causing a phenomenon in which the rate of increase in the magnet internal pressure rises to a certain value. In other words, it is believed that GCIH occurs due to two factors: the mechanical vibration is transmitted to the radiation shield 62, and the radiation shield 62 vibrates due to the influence of the leakage magnetic field.

[0040] Next, the frequency characteristics of the rate of increase in the internal pressure of the magnet due to GCIH will be described. FIG. 3 is a diagram showing the relationship between the frequency of the current (also called the drive frequency) supplied from the gradient magnetic field power supply 21 to the gradient magnetic field coil 43 and the rate of increase of the magnet internal pressure. The horizontal axis of FIG. 3 is the drive frequency of the gradient magnetic field coil 43. The vertical axis of FIG. 3 shows the rate of increase of the magnet internal pressure when the frequency on the horizontal axis is used at a constant current for a certain time (for example, 10 minutes). P1 in FIG. 3 shows the value of the rate of increase of the magnet internal pressure caused by the leakage magnetic field when there is no resonance. The rate of increase is the ratio of the increase value to the value before the change. P2 in FIG. 3 shows the rate of increase of the magnet internal pressure actually observed. This shows the total value of the value of the rate of increase of the magnet internal pressure caused by the leakage magnetic field and the value of the rate of increase of the magnet internal pressure caused by the resonance of the mechanical vibration of the gradient magnetic field coil 43, etc. As described above, mechanical vibrations and leakage magnetic fields are transmitted to the radiation shield 62, and the leakage magnetic field causes the radiation shield 62 to vibrate. This results in an internal pressure rise rate of P1, shown by the dotted line, and further, due to the inherent frequency of the mechanical vibrations, a peak in the internal pressure rise rate, as shown in P2, is actually observed.

[0041] The magnitude of vibration of the radiation shield 62 varies depending on the frequency of the gradient magnetic field. For example, the magnitude of vibration of the gradient magnetic field coil 43 caused by the leakage magnetic field increases as the frequency of the gradient magnetic field increases. Therefore, as shown by P1 in FIG. 3, the higher the frequency of the gradient magnetic field, the higher the value of the rate of increase of the magnet internal pressure caused by the leakage magnetic field.

[0042] In addition, structures such as the gradient coil 43 and the heat shield inside the magnet have resonance points. That is, the magnitude of mechanical vibration of structures such as the gradient coil 43 and the heat shield inside the magnet increases as the frequency of the gradient magnetic field approaches the resonance point. Therefore, as shown in P2 of Fig. 3, the value of the rate of increase of the magnet internal pressure of the static magnetic field magnet 41 caused by the mechanical vibration of the gradient coil 43 increases at the resonance points F1 and F2. The size and number of the resonance points change depending on the structure, material, characteristics, etc. of the static magnetic field magnet 41 and the gradient coil 43.

[0043] As described above, since the rate of increase of the internal pressure of the static magnetic field magnet 41 has a frequency characteristic as shown in FIG. 3, it is necessary to adjust the imaging sequence taking such a frequency characteristic into consideration. Therefore, in the sequence adjustment function 516, the processing circuit 51 predicts the magnet internal pressure or magnet temperature when the imaging sequence is executed based on the imaging sequence of the magnetic resonance imaging and the relationship between the driving frequency of the gradient magnetic field coil 43 and the magnet internal pressure or magnet temperature of the static magnetic field magnet 41, and adjusts the imaging sequence based on the prediction result. In this embodiment, the energy that causes an increase in the magnet internal pressure when the imaging sequence is executed is estimated using a circuit model that takes into account the frequency characteristic P1 of the rate of increase of the actual magnet internal pressure, and the imaging sequence is adjusted before the imaging sequence is executed based on the estimation result. Specifically, the processing circuit 51 uses an equivalent circuit for the magnet internal pressure of the static magnetic field magnet as a circuit model, calculates the current value flowing in the equivalent circuit based on the imaging sequence, and adjusts the imaging sequence based on the calculated current value. More specifically, the processing circuit 51 calculates the energy consumed by the equivalent circuit based on the value of the current flowing through the equivalent circuit, predicts the rate of increase of the magnet internal pressure based on the calculated energy, and adjusts the imaging sequence based on the rate of increase. At this time, the processing circuit 51 estimates the amount of heat input into the magnet based on the rate of increase of the magnet internal pressure, and adjusts the imaging sequence so that the amount of heat input does not exceed a threshold value related to quenching.

[0044] The equivalent circuit includes a first circuit connected to a power supply equivalent to the gradient magnetic field power supply 21 and having self-inductance, and a second circuit having mutual inductance between the first circuit. The second circuit has a closed circuit that resonates between the capacitance component of the circuit and a second inductor that is coupled to the first circuit by mutual inductance. The resonance characteristics of the second circuit are set based on the relationship between the driving frequency of the gradient magnetic field coil 43 and the magnet internal pressure. When there are not only one frequency but many frequencies as the resonance characteristics, the equivalent circuit includes the same number of second circuits as the number of resonance frequencies. The second circuit calculates the rate of increase of the magnet internal pressure caused by the mechanical vibration of the gradient magnetic field coil 43. The equivalent circuit also includes a third circuit consisting of a third inductor and a resistor that are coupled to the inductor of the first circuit by mutual induction in order to calculate the portion of the rate of increase P1 of the magnet internal pressure caused by the leakage magnetic field in FIG. 3. The second circuit and the third circuit calculate the portion of P1 in FIG. 3. If the curve P1 in Fig. 3 cannot be expressed by one third circuit, a necessary number of circuits consisting of third inductances and resistors with different constants may be provided. Then, the part P2 in Fig. 3, which indicates the total value of the rate of increase of the magnet internal pressure caused by the leakage magnetic field and the rate of increase of the magnet internal pressure caused by the mechanical vibration of the gradient magnetic field coil 43, is calculated by the second circuit and the third circuit.

[0045] For example, the equivalent circuit includes a primary circuit representing a current that matches the gradient magnetic field waveform, and one or more secondary circuits through which induced current flows, and the secondary circuits are composed of a circuit representing the frequency characteristics of the vibration of the gradient magnetic field coil 43 and a circuit representing the offset of the internal pressure rise rate due to the leakage magnetic field.

[0046] 1, the processing circuitry 51 generates information on an imaging sequence based on imaging conditions input by an operator using a sequence control function 517, and controls imaging by transmitting the generated information on the imaging sequence to the sequence control circuit 29. At this time, the processing circuitry 51 executes an imaging sequence adjusted by processing in the sequence adjustment function 516. In addition, in the sequence control function 517, the processing circuitry 51 receives MR data from the sequence control circuit 29, and stores the received MR data in the memory 52. ​​The processing circuitry 51 that realizes the sequence control function 517 is an example of a sequence control unit.

[0047] Next, the operation of the sequence adjustment process executed by the processing circuit 51 in the sequence adjustment function 516 will be described. The sequence adjustment process is a process for adjusting the sequence before execution of the sequence, taking into account the frequency characteristics of the magnet pressure rise rate, so that a quench does not occur due to GCHI. ​​FIG. 4 is a flowchart showing an example of the sequence adjustment process procedure. Note that the processing procedures in each process described below are merely examples, and each process can be appropriately changed as much as possible. Also, for the processing procedures described below, steps can be omitted, replaced, and added as appropriate depending on the embodiment.

[0048] (Sequence adjustment process) (Step S101) In the sequence adjustment function 516, the processing circuitry 51 first selects an imaging sequence to be adjusted. The imaging sequence to be adjusted may be selected by a user's input, or all registered imaging sequences may be selected one by one in order.

[0049] (Step S102) Next, the processing circuit 51 acquires an upper limit value of the heat input amount into the static magnetic field magnet 41. The upper limit value of the heat input amount is stored in advance in, for example, the memory 52. ​​The upper limit value of the heat input amount is set to, for example, a value smaller than the threshold value at which a quench is caused. For example, the upper limit value of the heat input amount is set to a value 0.9 times the threshold value at which a quench occurs.

[0050] (Step S103) Next, the processing circuit 51 calculates the magnet internal pressure and the amount of heat input into the magnet when the selected sequence is executed, using an equivalent circuit that takes into account GCIH (Gradient Coil Induced Heating).

[0051] Here, the equivalent circuit used as the circuit model in the sequence adjustment process will be described in detail. FIG. 5 is a diagram showing an example of an equivalent circuit. As shown in FIG. 5, the equivalent circuit has a circuit 81 connected to the gradient magnetic field power supply 21 and four closed circuits 82-85. The circuit 81 is a primary side circuit and is an example of a first circuit. The closed circuits 82-85 are secondary side circuits. The closed circuits 84-85 are an example of a second circuit. The closed circuits 82-83 are an example of a third circuit.

[0052] The circuit 81 is a circuit in which a power supply 81E corresponding to the gradient magnetic field power supply 21, a resistor 81R, and a coil 81L are connected in series. The power supply 81E corresponds to the X-axis gradient magnetic field power supply or the Y-axis gradient magnetic field power supply that the gradient magnetic field power supply 21 has.

[0053] The closed circuit 82 is a closed circuit in which a resistor 82R and a coil 82L are connected in series. The closed circuit 83 is a circuit in which a resistor 83R and a coil 83L are connected in series. The closed circuit 84 is a resonant circuit in which a resistor 84R, a coil 84L, and a capacitor 84C are connected in series. The closed circuit 85 is a resonant circuit in which a resistor 85R, a coil 85L, and a capacitor 85C are connected in series. Each of the coils 82L-85L is electromagnetically coupled to the coil 81L of the circuit 81, which is the primary side circuit.

[0054] Here, the resistance values ​​of resistors 81R, 82R, 83R, 84R, and 85R are R1, R2, R3, R4, and R5, respectively. The self-inductance values ​​of coils 81L, 82L, 83L, 84L, and 85L are L1, L2, L3, L4, and L5, respectively. The capacitances of capacitors 84C and 85C are C4 and C5, respectively. The mutual inductance value between coils 81L and 82L is M12, the mutual inductance value between coils 81L and 83L is M13, the mutual inductance value between coils 81L and 84L is M14, and the mutual inductance value between coils 81L and 85L is M15.

[0055] The current values ​​flowing through circuits 81, 82, 83, 84, and 85 are I1(t), I2(t), I3(t), I4(t), and I5(t), respectively. The current values ​​I1(t)-I5(t) are functions of time t. Circuit equations hold for the circuit 81 and the closed circuit 82, and for the circuit 81 and the closed circuit 83. The current value I1(t) corresponds to the frequency of the pulse sequence of the gradient magnetic field. In other words, the change over time of the current value I1(t) corresponds to the change in the waveform of the frequency of the pulse sequence.

[0056] The resistance values ​​(R1-R5) of the resistors (81R-85R), the self-inductance values ​​(L1-L5) of the coils (81L-85L), the capacitances (C4-C5) of the capacitors (84C-85C), and the mutual inductance values ​​(M12-M15) are preset so that the total value E of the energy (E2-E5) consumed in the secondary circuit (closed circuit 82-85) matches the frequency characteristics of the rate of increase of the magnet internal pressure shown in Figure 3. These parameters may be determined experimentally or theoretically. For example, when each parameter is experimentally determined, first, with the gradient magnetic field power supply output of the actual device held at a constant sine wave value, the frequency is changed while measuring the rate of increase in the magnet internal pressure, thereby obtaining the rate of increase in the magnet internal pressure shown in P2 of Fig. 3. Next, with the current value of 81E in Fig. 5 held constant, the frequency is changed, and the values ​​of L2, L3, L4, L5, R2, R3, R4, R5, C4, and C5 are adjusted so that the sum of the power consumption of R2, R3, R4, and R5 draws a curve similar to P2 in Fig. 3.

[0057] The energy consumed in the closed circuits 82 and 83 corresponds to the rate of increase of the magnet internal pressure caused by the leakage magnetic field. The parameters of each component of the closed circuits 82 and 83 are set to match the frequency characteristics of the rate of increase of the magnet internal pressure caused by the leakage magnetic field as shown in P1 of FIG. 3. In FIG. 5, two closed circuits corresponding to the frequency characteristics of the rate of increase of the magnet internal pressure caused by the leakage magnetic field are provided, but the number of closed circuits corresponding to the leakage magnetic field provided in the equivalent circuit may be one or three or more. The more closed circuits corresponding to the leakage magnetic field, the more accurate the prediction of the frequency characteristics of the rate of increase of the magnet internal pressure caused by the leakage magnetic field can be. Note that, when the rate of increase of the magnet internal pressure caused by the leakage magnetic field is small, it is not necessary to provide a closed circuit corresponding to the frequency characteristics of the rate of increase of the magnet internal pressure caused by the leakage magnetic field.

[0058] The energy consumed in the closed circuits 84 and 85, which are resonant circuits, corresponds to the rate of increase of the magnet internal pressure caused by the mechanical vibration of the gradient coil 43. Therefore, the parameters of each component of the closed circuits 84 and 85 are set to match the frequency characteristics of the rate of increase of the magnet internal pressure caused by the mechanical vibration of the gradient coil 43. In addition, the circuits 84 and 85 correspond to one of the resonance points F1 and F2, respectively. Each of the closed circuits 84 and 85 is set so that the consumed energy corresponds to the rate of increase of the magnet internal pressure near the corresponding resonance point. The resonance circuits corresponding to the mechanical vibration of the gradient coil 43 are provided in the same number as the number of resonance points included in the frequency band used in the sequence, for example.

[0059] Returning to FIG. 4, in the process of step S103, when calculating the predicted value of the maximum value of the magnet internal pressure during the sequence execution, the processing circuit 51 first calculates the current values ​​I2(t)-I5(t) flowing through the closed circuits 82-85. At this time, the processing circuit 51 calculates the current values ​​I2(t)-I5(t) flowing through the closed circuits 82-85 at each time by solving the differential equation of the circuit equation in the equivalent circuit at each time based on the imaging sequence executed by the magnetic resonance imaging. As a method for calculating the current values ​​I2(t)-I5(t), a known method using Laplace transform for the differential equation of the circuit equation in the equivalent circuit can be used. Alternatively, the general solution of the differential equation may be solved by the variable separation method, and then the specific solution may be solved by the constant variation method.

[0060] Next, the processing circuit 51 calculates the consumed energy E2-E5 consumed at each time by the resistors 82R-85R of the closed circuits 82-85 using the calculation results of the current values ​​I2(t)-I5(t). The consumed energy E2-E5 can be calculated, for example, using the following formula (1). Z4 and Z5 in formula (1) are impedances in the closed circuits 84 and 85, respectively. The impedances Z4 and Z5 can be calculated, for example, using the following formula (2).

[0061]

number

[0062]

number

[0063] Next, the processing circuit 51 calculates the energy consumption in the equivalent circuit in the imaging sequence by adding up the total value E of the energy consumption E2-E5 at each time until the selected imaging sequence is completed.

[0064] Next, the processing circuit 51 estimates the amount of heat input into the magnet by using the energy consumption on the equivalent circuit in the imaging sequence as the rate of increase of the magnet internal pressure. At this time, the energy consumption on the equivalent circuit per unit time is used as the amount of heat input into the magnet.

[0065] In this way, the processing circuit 51 estimates the amount of heat input into the magnet after the sequence is executed, based on the current values ​​I2(t)-I5(t) flowing through the closed circuits 82-85 of the equivalent circuit.

[0066] (Step S104) Next, the processing circuit 51 compares the predicted value of the amount of heat input into the magnet with the upper limit value to determine whether execution of the selected sequence will cause the amount of heat input to exceed the upper limit value.

[0067] If the predicted value of the heat input is equal to or less than the upper limit value, i.e., if the predicted value of the heat input does not exceed the upper limit value (step S104-No), the processing circuit 51 determines that adjustment of the selected sequence is not necessary and terminates the sequence adjustment process for the selected sequence.

[0068] (Step S105) When the heat input is greater than the upper limit, that is, when the predicted value of the heat input exceeds the upper limit (step S104-No), the processing circuit 51 determines that the selected sequence needs to be adjusted, and adjusts the imaging conditions of the selected sequence so that the predicted value of the heat input after the sequence is executed is equal to or less than the upper limit. For example, the FOV (Field Of View) in the imaging is enlarged. This reduces the current value output from the gradient magnetic field power supply 21, reduces the heat input by the GCIH, and reduces the rise rate value of the magnet internal pressure. Alternatively, instead of enlarging the FOV, the TR (Repetition Time) in the imaging may be enlarged. Alternatively, the ETS (Echo Train Space) in the EPI sequence may be changed to avoid the resonant frequency of the gradient magnetic field coil 43. In this case, the heat input by the GCIH is also reduced, and the rise rate value of the magnet internal pressure is reduced.

[0069] When the sequence adjustment is completed, the processing circuitry 51 updates the sequence information recorded in the memory 52 or the like based on the adjusted sequence, and ends the sequence adjustment process. Note that it is preferable to repeatedly adjust the imaging conditions of the sequence until optimal imaging conditions are set by executing the processes of steps S101-S104 again using the adjusted sequence.

[0070] The effects of the magnetic resonance imaging apparatus 1 according to this embodiment will be described below.

[0071] The magnetic resonance imaging apparatus 1 according to the present embodiment can predict the magnet internal pressure or magnet temperature when the imaging sequence is executed based on the imaging sequence of the magnetic resonance imaging and the relationship between the driving frequency of the gradient magnetic field coil 43 and the magnet internal pressure or magnet temperature of the static magnetic field magnet 41, adjust the imaging sequence based on the prediction result, and execute the adjusted imaging sequence. Specifically, the magnetic resonance imaging apparatus 1 can calculate the current value flowing through the equivalent circuit when executing the imaging sequence using an equivalent circuit for the internal pressure of the static magnetic field magnet 41, adjust the imaging sequence based on the total value of the current value, and execute the adjusted imaging sequence. The equivalent circuit includes a circuit 81 connected to a power source 81E and having a self-inductance L1, and closed circuits 84 and 85 having mutual inductances M14 and M15 with the circuit 81 and resonating with the circuit 81. The resonance characteristics of the closed circuits 84 and 85 are set based on the relationship between the driving frequency of the gradient magnetic field coil 43 and the internal pressure of the static magnetic field magnet 41. The circuit 81 corresponds to a first circuit, and the closed circuits 84 and 85 correspond to a second circuit.

[0072] For example, the magnetic resonance imaging apparatus 1 calculates the energy consumed in the equivalent circuit based on the current value (I4(t)-I5(t)) flowing through the equivalent circuit, predicts the rate of rise of the magnet internal pressure based on the calculated consumed energy, predicts the amount of heat input into the magnet based on the rate of rise of the magnet internal pressure, and adjusts the imaging sequence based on the amount of heat input. At this time, for example, the imaging sequence is adjusted so that the amount of heat input does not exceed a threshold related to quenching. Instead of performing threshold determination using the amount of heat input into the magnet, threshold determination may be performed using the rate of rise of the magnet internal pressure, and the imaging sequence may be adjusted so that the rate of rise of the magnet internal pressure does not exceed a threshold related to quenching.

[0073] The equivalent circuit also has second circuits (84, 85) in the same number as the resonance points of the gradient magnetic field coil 43. The energies E4, E5 consumed in the closed circuits 84, 85 correspond to the energy that GCHI caused by the mechanical vibration of the gradient magnetic field coil 43 causes an increase in the magnet internal pressure. Therefore, the energies E4, E5 consumed in the closed circuits 84, 85 correspond to the rate of increase in the magnet internal pressure, and the power consumption (energy consumption E4, E5 per unit time) corresponds to the amount of heat input into the static magnetic field magnet 41. In other words, the equivalent circuit is designed in consideration of the frequency characteristics of GCHI caused by the mechanical vibration of the gradient magnetic field coil 43.

[0074] With the above configuration, the magnetic resonance imaging apparatus 1 of this embodiment calculates the current value by focusing on the current value flowing through the equivalent circuit, calculates the energy consumption of the equivalent circuit from the calculated current value, and calculates the rate of increase of the magnet internal pressure and the heat input based on the calculated energy consumption. This makes it possible to predict the energy that causes the magnet internal pressure to increase, and further to predict the heat input due to the GCIH. Then, by adjusting the sequence so that the heat input is smaller than the limit value at which quenching occurs, it is possible to suppress the risk of quenching due to the GCIH occurring without restricting the sequence specifications more than necessary. This makes it possible to execute the imaging sequence under optimized conditions that bring out the performance of the gradient magnetic field generating system.

[0075] The equivalent circuit further includes closed circuits 82 and 83 having mutual inductance (M12, M13) between the circuit 81 and the closed circuits 82 and 83. The energies E2 and E3 consumed in the closed circuits 82 and 83 correspond to the rate of increase in the magnet internal pressure caused by the leakage magnetic field, and the power consumption (energy consumption E2 and E3 per unit time) corresponds to the amount of heat input into the static magnetic field magnet 41. The closed circuits 82 and 83 correspond to a third circuit. That is, the equivalent circuit is designed in consideration of the rate of increase in the magnet internal pressure and the amount of heat input caused by both the mechanical vibration of the gradient magnetic field coil 43 and the leakage magnetic field. By using this equivalent circuit, it is possible to more accurately predict the energy that causes the magnet internal pressure increase and the heat input into the magnet. Then, by adjusting the sequence based on the prediction result, it is possible to execute the imaging sequence under more optimized conditions.

[0076] (Modification) Instead of the magnet internal pressure, the magnet temperature of the static magnetic field magnet 41 may be used. In this case, an equivalent circuit for the magnet temperature is used, and the resonance characteristics of the closed circuits 84, 85 are set based on the relationship between the drive frequency of the gradient magnetic field coil 43 and the magnet temperature. In this case, the energies E4, E5 consumed in the closed circuits 84, 85 correspond to the rate of rise of the magnet temperature due to GCHI caused by the mechanical vibration of the gradient magnetic field coil 43. Then, the rate of rise of the magnet temperature is predicted based on the consumed energies E4, E5, and the imaging sequence is adjusted so that the rate of rise of the magnet temperature does not exceed the heat threshold value related to quenching.

[0077] Also, both the magnet internal pressure and magnet temperature of the static magnetic field magnet 41 may be used. In this case, an equivalent circuit for the magnet temperature is used in addition to an equivalent circuit for the magnet internal pressure, and both the rate of increase of the magnet internal pressure and the rate of increase of the magnet temperature are predicted based on the energy consumption of these equivalent circuits. Then, the imaging sequence is adjusted so that the rate of increase of the magnet internal pressure does not exceed the heat quantity threshold for quenching, and so that the rate of increase of the magnet temperature does not exceed the heat quantity threshold for quenching.

[0078] In addition, the above-mentioned circuit configuration of the equivalent circuit is merely an example, and the embodiment is not limited to the above-mentioned example. For example, the number of resonant circuits (84, 85) is not limited to two, and may be, for example, one or three or more. In addition, the number of closed circuits (82, 83) is not limited to two, and may be, for example, one or three or more. In addition, when the effect of the leakage magnetic field on GCHI is small, the closed circuits (82, 83) may be omitted.

[0079] In addition, in the present embodiment, an example has been described in which an equivalent circuit having two resonant circuits 84 and 85 is used in consideration of the frequency characteristics of a frequency band in which two resonant points exist, but the present invention is not limited to this. The equivalent circuit may also take into consideration the frequency characteristics of a frequency band that includes frequencies higher than the frequency band mainly used in the sequence. When three or more resonant points exist in this frequency band, three resonant circuits are provided in the equivalent circuit.

[0080] Furthermore, although a configuration in which the sequence is adjusted in advance has been described, the sequence may be adjusted by predicting the magnet internal pressure and magnet temperature during execution of the sequence and changing the imaging conditions, etc.

[0081] In the above embodiment, a method for preventing quenching due to GCIH by predicting the rate of increase of the magnet internal pressure based on the response when a sequence waveform during execution of an imaging sequence is input to an equivalent circuit, which is an electric circuit model, has been described. Since the sequence waveform is known as a waveform that drives a gradient magnetic field from this, it is possible to use this sequence waveform as a gradient magnetic field strength waveform on the frequency axis by performing a fast Fourier transform (FFT). That is, instead of an equivalent circuit, the rate of increase of the magnet internal pressure can be predicted using frequency components generated by FFT. For example, FIG. 3 is equivalent to a graph of the rate of increase of the magnet internal pressure obtained when the gradient magnetic field coil 43 is driven with a constant input current and a constant frequency, measured while changing the frequency little by little. Therefore, the rate of increase of the magnet internal pressure can be predicted by weighting the frequency components obtained by performing an FFT on the sequence waveform with the value obtained at P2 in FIG. 3. For example, if the result of performing FFT on the sequence waveform shows that the component corresponding to frequency F1 in Fig. 3 is sufficiently small among the frequency components obtained by FFT, even if that component is weighted by P2 in Fig. 3, the predicted value of the rate of increase of the magnet internal pressure will not have a peak at frequency F1 like P2 in Fig. 3. Therefore, it can be confirmed that the possibility of a quench is low when the imaging sequence is executed, and it is possible to carry out the inspection without making any modifications to the imaging sequence.

[0082] On the other hand, if the result of performing FFT on the sequence waveform and weighting it with the value obtained at P2 in Figure 3 shows that the predicted value of the rate of rise of the magnet internal pressure has a peak at frequency F1 and is greater than the reference value, it is possible to suggest to the operator that the risk of quenching be reduced by lowering the peak of the predicted value of the rate of rise of the magnet internal pressure at frequency F1 by extending the repetition interval (TR) or lowering the resolution, etc. This suggestion can be made, for example, by a method of displaying an operation panel-like pop-up on the display.

[0083] According to at least one of the embodiments described above, it is possible to execute an imaging sequence under optimized conditions while safely driving the gradient magnetic field generating system.

[0084] Although some embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0085] 1...Magnetic resonance imaging device 11... Stand 111…Housing 112…Boa 13. Bed 131…Tabletop 133…Foundation 21...Gradient magnetic field power supply 23...Transmitting circuit 25…Receiver circuit 27...Bed drive unit 29...Sequence control circuit 41...Static magnetic field magnet 43...Gradient magnetic field coil 45…Transmitting coil 47…Receiver coil 50...Host computer 51... Processing circuit 511... Imaging protocol setting function 512…Data acquisition function 513…Image generation function 514…Image processing function 515…Display control function 516…Sequence adjustment function 517...Sequence control function 52…Memory 53…Display 54...Input interface 55...Communication interface 61...Vacuum container 62…Radiation shield 63…Helium container 64...Support structure 65…Superconducting coil 81, 82, 83, 84, 85…circuit 81E…Power supply 81L, 82L, 83L, 84L, 85L... Coil 81R, 82R, 83R, 84R, 85R...Resistor 84C, 85C… Capacitor F1, F2…resonance point

Claims

1. a sequence adjustment unit that predicts the magnet internal pressure or magnet temperature when the imaging sequence is executed based on an imaging sequence of magnetic resonance imaging and the relationship between the driving frequency of the gradient magnetic field coil and the magnet internal pressure or magnet temperature of the static magnetic field magnet, and adjusts the imaging sequence based on the prediction result; a sequence control unit that executes the imaging sequence adjusted by the sequence adjustment unit; Equipped with the sequence adjustment unit uses an equivalent circuit for the magnet internal pressure or the magnet temperature, calculates a current value flowing in the equivalent circuit based on the imaging sequence, and predicts the magnet internal pressure or the magnet temperature when the imaging sequence is executed based on the current value; the equivalent circuit is generated based on the relationship, and includes a first circuit connected to a power supply equivalent to a gradient magnetic field power supply and having self-inductance, and a second circuit having mutual inductance with the first circuit and resonating with the first circuit, the resonance characteristics of the second circuit are set based on the relationship. Magnetic resonance imaging device.

2. the sequence adjustment unit calculates the energy consumed by the second circuit based on the current value, predicts the rate of increase of the magnet internal pressure, the rate of increase of the magnet temperature, or the amount of heat input to the static magnetic field magnet based on the energy, and adjusts the imaging sequence based on the rate of increase or the amount of heat input.

2. The magnetic resonance imaging apparatus according to claim 1.

3. the sequence adjustment unit adjusts the imaging sequence so that the rate of rise or the amount of heat input does not exceed a threshold value related to quenching.

3. The magnetic resonance imaging apparatus according to claim 2.

4. The energy consumed by the second circuit corresponds to the rate of increase of the internal pressure of the magnet caused by mechanical vibration of the gradient coil, the rate of increase of the magnet temperature, or the amount of heat input to the static magnetic field magnet.

2. The magnetic resonance imaging apparatus according to claim 1.

5. The magnetic resonance imaging apparatus according to claim 1 , wherein the equivalent circuit includes the second circuits in the same number as the number of resonance points of the gradient magnetic field coil.

6. the equivalent circuit further includes a third circuit having mutual inductance with the first circuit, The energy consumed by the third circuit corresponds to the rate of increase of the internal pressure of the magnet due to the leakage magnetic field of the gradient magnetic field, the rate of increase of the magnet temperature, or the amount of heat input to the static magnetic field magnet.

2. The magnetic resonance imaging apparatus according to claim 1.

7. the sequence adjustment unit predicts a heat input amount to the static magnetic field magnet during execution of an imaging sequence based on the prediction result of the magnet internal pressure, and adjusts the imaging sequence based on the prediction result of the heat input amount.

2. The magnetic resonance imaging apparatus according to claim 1.

8. A sequence adjustment unit that predicts the magnet internal pressure or magnet temperature when the imaging sequence is executed based on the imaging sequence of magnetic resonance imaging and the relationship between the driving frequency of the gradient magnetic field coil and the magnet internal pressure or magnet temperature of the static magnetic field magnet, and adjusts the imaging sequence based on the prediction result; a sequence control unit that executes the imaging sequence adjusted by the sequence adjustment unit; Equipped with the sequence adjustment unit predicts the magnet internal pressure or the magnet temperature during execution of the imaging sequence based on frequency components generated by Fourier transforming the waveform of the imaging sequence and the relationship; Magnetic resonance imaging device.

Images