Magnetic resonance imaging apparatus and imaging management method

Abstract

To support efficient inspection while securing quality.SOLUTION: A magnetic resonance imaging apparatus according to this embodiment comprises a calculation part and a determination part. The calculation part calculates an acceptable amount of a heat input to a superconducting magnet to be assigned to each of a plurality of imagings scheduled in an object period. The determination part determines an imaging condition on the basis of the acceptable amount, in each imaging.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Superconducting magnetic resonance imaging devices (superconducting MRI devices) use helium, for example, as a refrigerant for the superconducting coil. However, the recent rise in the price of helium has put pressure on the lifetime cost of MRI devices. Therefore, it is desirable to adopt a low-volume refrigerant that uses as little helium as possible. With the recent focus on low-capacity refrigerants, it is necessary to consider the phenomenon of gradient coil induced heating (GCIH), in which the application of a gradient magnetic field during imaging generates induced currents in the superconducting coils of a superconducting magnet, causing a rise in temperature within the superconducting magnet. In other words, in MRI systems with a large helium capacity and sufficient refrigerant, even if the temperature of the superconducting coil rises, the heat is likely to be absorbed by evaporation of the refrigerant. However, when the amount of refrigerant is small, such as with low-capacity refrigerants, the sudden increase in GCIH due to imaging cannot be accommodated, increasing the possibility of quenching due to the intrusion of heat from the outside.

[0003] Therefore, a conventional method is to predict the behavior of the magnet regarding quenching for each imaging session when it is performed, and if the risk of quenching is high, to stop the imaging before it is actually performed. However, because the risk of quenching is determined for each imaging session, the first imaging session can be performed under favorable conditions, but if the first imaging session is performed under favorable conditions, the imaging conditions for subsequent imaging sessions become more severe, and the required quality of imaging cannot be obtained. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 8,058,873 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 support efficient inspection while ensuring quality. 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 below can also be positioned as other problems. [Means for solving the problem]

[0006] The magnetic resonance imaging apparatus according to the present embodiment includes a calculation unit and a determination unit. The calculation unit calculates an allowable amount of heat input to a superconducting magnet, which is allocated for each of a plurality of imaging operations scheduled for a target period. The determination unit determines imaging conditions for each imaging operation based on the allowable amount. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a conceptual diagram showing an MRI apparatus according to this embodiment. [Figure 2] FIG. 2 is a flowchart showing the imaging management process of the MRI apparatus according to this embodiment. [Figure 3] FIG. 3 is a flowchart showing details of the allowable amount calculation process according to this embodiment. [Figure 4] FIG. 4 is a flowchart showing an imaging management process of an MRI apparatus according to a modified example of this embodiment. [Figure 5] FIG. 5 is a flowchart showing details of the process of estimating the marginal imaging condition according to this embodiment. [Figure 6] FIG. 6 is a conceptual diagram showing an example of calculation of the calorific value required to generate the calorific value database according to this embodiment. [Figure 7] FIG. 7 is a diagram showing an example of a transfer function according to this embodiment. [Figure 8]FIG. 8 is a diagram showing an example of information presented to the operator according to this embodiment. [Figure 9A] FIG. 9A is a diagram showing a first example of a simulation result by an MRI apparatus that performs imaging management according to this embodiment. [Figure 9B] FIG. 9B is a diagram showing a second example of a simulation result by the MRI apparatus that performs imaging management according to this embodiment. [Figure 10A] FIG. 10A is a diagram showing a first example of a simulation result using a conventional MRI apparatus as a comparative example. [Figure 10B] FIG. 10B is a diagram showing a second example of a simulation result using a conventional MRI apparatus as a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a magnetic resonance imaging apparatus (MRI apparatus) and an imaging management method according to the present embodiment will be described with reference to the drawings. In the following embodiments, parts with the same reference numerals perform similar operations, and redundant explanations will be omitted as appropriate.

[0009] FIG. 1 is a conceptual diagram showing an MRI apparatus according to this embodiment. 1, the MRI apparatus 1 includes a static magnetic field magnet 101, a magnet management unit 2, a gradient magnetic field coil 103, a gradient magnetic field power supply 105, a bed 107, a bed control circuit 109, a transmission circuit 113, a transmission coil 115, a reception coil 117, a reception circuit 119, a sequence control circuit 121, a bus 123, an interface 125, a display 127, a storage device 129, and a processing circuit 131. The MRI apparatus 1 may include a hollow cylindrical shim coil between the static magnetic field magnet 101 and the gradient magnetic field coil 103.

[0010] The static magnetic field magnet 101 is a magnet formed in a hollow, approximately cylindrical shape. The static magnetic field magnet 101 is not limited to an approximately cylindrical shape, and may be configured in an open shape. The static magnetic field magnet 101 generates a uniform static magnetic field in the internal space. In this embodiment, the static magnetic field magnet 101 is assumed to be a superconducting magnet using a superconducting coil.

[0011] The gradient magnetic field coil 103 is a coil formed in a hollow cylindrical shape. The gradient magnetic field coil 103 is placed inside the static magnetic field magnet 101. The gradient magnetic field coil 103 is formed by combining three coils corresponding to the X, Y, and Z axes that are orthogonal to each other. The Z-axis direction is the same as the direction of the static magnetic field. The Y-axis direction is the vertical direction, and the X-axis direction is the direction perpendicular to the Z and Y axes. The three coils in the gradient magnetic field coil 103 are individually supplied with current from a gradient magnetic field power supply 105, and generate gradient magnetic fields whose magnetic field strength changes along each of the X, Y, and Z axes.

[0012] The gradient magnetic fields of the X, Y, and Z axes generated by the gradient coil 103 form, for example, a frequency encoding gradient magnetic field (also called a readout gradient magnetic field), a phase encoding gradient magnetic field, and a slice selection gradient magnetic field. The frequency encoding gradient magnetic field is used to change the frequency of the MR signal depending on the spatial position. The phase encoding gradient magnetic field is used to change the phase of the MR signal depending on the spatial position. The slice selection gradient magnetic field is used to determine the imaging cross section.

[0013] The gradient magnetic field power supply 105 is a power supply device that supplies current to the gradient magnetic field coil 103 under the control of the sequence control circuit 121 .

[0014] The bed 107 is a device equipped with a tabletop 1071 on which the subject P is placed. The bed 107 inserts the tabletop 1071 on which the subject P is placed into a bore 111 under the control of a bed control circuit 109. The bed 107 is installed in an examination room in which the MRI apparatus 1 is installed, for example, so that the longitudinal direction is parallel to the central axis of the static magnetic field magnet 101.

[0015] The bed control circuit 109 is a circuit that controls the bed 107, and drives the bed 107 in response to an instruction from the operator via the interface 125, thereby moving the tabletop 1071 in the longitudinal direction and the up-down direction.

[0016] The transmitting coil 115 is an RF coil arranged inside the gradient magnetic field coil 103. The transmitting coil 115 receives RF (Radio Frequency) pulses from the transmitting circuit 113 and generates a transmitting RF wave corresponding to a high frequency magnetic field. The transmitting coil 115 is, for example, a whole-body coil. The whole-body coil may be used as a transmitting / receiving coil. A cylindrical RF shield is installed between the whole-body coil and the gradient magnetic field coil 103 to magnetically separate these coils.

[0017] The transmission circuit 113 supplies an RF pulse corresponding to the Larmor frequency or the like to the transmission coil 115 under the control of the sequence control circuit 121 .

[0018] The receiving coil 117 is an RF coil arranged inside the gradient magnetic field coil 103. The receiving coil 117 receives MR signals emitted from the subject P by a high frequency magnetic field. The receiving coil 117 outputs the received MR signals to a receiving circuit 119. The receiving coil 117 is, for example, a coil array having one or more, typically a plurality of coil elements. The receiving coil 117 is, for example, a phased array coil.

[0019] The receiving circuit 119 generates a digital MR signal, which is digitized complex data, based on the MR signal output from the receiving coil 117 under the control of the sequence control circuit 121. Specifically, the receiving circuit 119 performs various signal processing on the MR signal output from the receiving coil 117, and then performs analog-to-digital (A / D) conversion on the data that has been subjected to various signal processing. The receiving circuit 119 samples the A / D converted data. As a result, the receiving circuit 119 generates a digital MR signal (hereinafter referred to as MR data). The receiving circuit 119 outputs the generated MR data to the sequence control circuit 121.

[0020] The sequence control circuit 121 controls the gradient magnetic field power supply 105, the transmission circuitry 113, the reception circuitry 119, etc. in accordance with the examination protocol output from the processing circuitry 131, and performs imaging of the subject P. The examination protocol has various pulse sequences (also called imaging sequences) according to the examination. The examination protocol defines the magnitude of the current supplied to the gradient magnetic field coil 103 by the gradient magnetic field power supply 105, the timing at which the gradient magnetic field power supply 105 supplies the current to the gradient magnetic field coil 103, the magnitude of the RF pulse supplied to the transmission coil 115 by the transmission circuitry 113, the timing at which the RF pulse is supplied to the transmission coil 115 by the transmission circuitry 113, the timing at which the MR signal is received by the reception coil 117, etc.

[0021] The bus 123 is a transmission path for transmitting data among the interface 125, the display 127, the storage device 129, and the processing circuit 131. Various biosignal measuring devices, external storage devices, various modalities, etc. may be appropriately connected to the bus 123 via a network, etc. For example, an electrocardiograph (not shown) is connected to the bus as a biosignal measuring device.

[0022] The interface 125 has circuits for receiving various instructions and information input from an operator. The interface 125 has circuits related to input devices such as a pointing device such as a mouse or a keyboard. Note that the circuits included in the interface 125 are not limited to circuits related to physical operating components such as a mouse and a keyboard. For example, the interface 125 may have an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the MRI apparatus 1 and outputs the received electrical signal to various circuits.

[0023] The display 127 displays various magnetic resonance images (MR images) generated by the image generation function 1313, various information related to imaging and image processing, and the like, under the control of the system control function 1311 in the processing circuitry 131. The display 127 is, for example, a CRT display, a liquid crystal display, an organic EL display, an LED display, a plasma display, or any other display or monitor known in the art.

[0024] The storage device 129 stores MR data filled in the k-space via the image generation function 1313, image data generated by the image generation function 1313, etc. The storage device 129 stores various examination protocols, imaging conditions including a plurality of imaging parameters defining the examination protocols, etc. The storage device 129 stores programs corresponding to various functions executed by the processing circuitry 131. The storage device 129 is, for example, a random access memory (RAM), a semiconductor memory element such as a flash memory, a hard disk drive, a solid state drive, an optical disk, etc. The storage device 129 may also be a drive or the like 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.

[0025] The magnet management unit 2 includes a temperature measurement circuit 20 . The temperature measurement circuit 20 measures the temperature of one or more superconducting coils that form the static magnetic field magnet 101 that generates a static magnetic field using a temperature sensor.

[0026] The processing circuitry 131 has a processor, memories such as a ROM (Read-Only Memory) and a RAM, etc., which are not shown as hardware resources, and comprehensively controls the MRI apparatus 1. The processing circuitry 131 includes a system control function 1311, an image generation function 1313, a calculation function 1315, a selection function 1317, a reception function 1319, an estimation function 1321, a determination function 1323, an imaging condition determination function 1325, an input restriction function 1327, and a presentation function 1329.

[0027] The various functions of the processing circuitry 131 are stored in the storage device 129 in the form of programs executable by a computer. The processing circuitry 131 is a processor that realizes the functions corresponding to these various functions by reading and executing the programs corresponding to these various functions from the storage device 129. In other words, the processing circuitry 131 in a state in which each program has been read out has the multiple functions shown in the processing circuitry 131 in FIG. 1.

[0028] 1, it has been explained that these various functions are realized by a single processing circuit 131, but it is also possible to configure the processing circuit 131 by combining multiple independent processors, and have each processor execute a program to realize the function. In other words, it is possible that each of the above-mentioned functions is configured as a program and one processing circuit executes each program, or that a specific function is implemented in a dedicated, independent program execution circuit.

[0029] The term "processor" used in the above description refers to circuits such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an Application Specific Integrated Circuit (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)).

[0030] The processor realizes various functions by reading and executing programs stored in the storage device 129. Note that instead of storing the programs in the storage device 129, the programs may be configured to be directly embedded in the processor circuitry. In this case, the processor realizes its functions by reading and executing the programs embedded in the circuitry. Note that the bed control circuitry 109, transmission circuitry 113, reception circuitry 119, sequence control circuitry 121, etc. are also similarly configured by electronic circuits such as the processor.

[0031] The processing circuitry 131 controls the MRI apparatus 1 using a system control function 1311. Specifically, the processing circuitry 131 reads out a system control program stored in the storage device 129, loads it on the memory, and controls each circuit of the MRI apparatus 1 in accordance with the loaded system control program. For example, the processing circuitry 131 reads out an examination protocol from the storage device 129 using the system control function 1311 based on imaging conditions input by the operator via the interface 125. The processing circuitry 131 may also generate the examination protocol based on the imaging conditions. The processing circuitry 131 transmits the examination protocol to the sequence control circuit 121 and controls imaging of the subject P.

[0032] The processing circuitry 131 applies excitation pulses and applies gradient magnetic fields in accordance with an excitation pulse sequence using a system control function 1311. After executing the excitation pulse sequence using the system control function 1311, the processing circuitry 131 collects MR signals from the subject P in accordance with a data collection sequence, which is a pulse sequence for collecting various types of data, and generates MR data.

[0033] The processing circuitry 131 fills the MR data along the readout direction of the k-space according to the strength of the readout gradient magnetic field using the image generation function 1313. The processing circuitry 131 generates an MR image by performing a Fourier transform on the MR data filled in the k-space. For example, the processing circuitry 131 can generate an absolute magnitude image from complex MR data. The processing circuitry 131 can also generate a phase image using real and imaginary part data of the complex MR data. The processing circuitry 131 outputs MR images such as the absolute magnitude image and the phase image to the display 127 or the storage device 129.

[0034] The processing circuitry 131 uses the calculation function 1315 to calculate the allowable amount of heat input to the superconducting magnet that is allocated for each of the multiple imaging sessions scheduled for the target period. The processing circuitry 131 uses a selection function 1317 to select an imaging sequence. The processing circuitry 131 receives, via the reception function 1319, desired imaging conditions that are imaging conditions desired by the operator of the MRI apparatus 1. The processing circuitry 131 estimates a feature amount relating to heat input to the superconducting magnet when imaging is performed under desired imaging conditions using the estimation function 1321. The estimation function 1321 also estimates limit imaging conditions, which are the limits of the imaging conditions. The processing circuit 131 uses the determination function 1323 to determine whether or not to perform imaging, whether imaging for the target period has ended, and so on. The processing circuit 131 determines the imaging conditions for each image capture based on the allowable amount using the imaging condition determination function 1325. The processing circuitry 131 uses the input restriction function 1327 to restrict input values ​​of imaging parameters related to desired imaging conditions from the operator. The processing circuitry 131 transmits the information to the operator by displaying the allowable amount on the display 127 or the like using the display function 1329.

[0035] Next, an example of imaging management processing of the MRI apparatus 1 according to this embodiment will be described with reference to the flowchart of Fig. 2. It is assumed that the imaging management processing shown in the flowchart of Fig. 2 is executed in units of imaging for one day or one week, for example.

[0036] In step S201, the processing circuitry 131 determines the allocation of the allowable amount for each imaging in the target period using the calculation function 1315. The method for determining the allocation of the allowable amount will be described later with reference to FIG. In step S202, the processing circuitry 131 selects an imaging sequence using the selection function 1317. The imaging sequence may be selected, for example, by an instruction from an operator, or the imaging sequence may be automatically selected by the processing circuitry 131 from a preset imaging schedule.

[0037] In step S203, the processing circuitry 131 accepts the desired imaging conditions input by the user using the reception function 1317. Note that in step S203, the processing circuitry 131 may set a limit on the input values ​​of imaging parameters related to the desired imaging conditions from the operator based on the allowable amount using the input limiting function 1327. This eliminates the need to redo or reset the imaging, allowing for more efficient examination. In step S204, the processing circuitry 131 estimates feature quantities expected when imaging is performed under the desired imaging conditions acquired in step S203 using the estimation function 1321. The feature quantities include the superconducting coil, the amount of heat generated and the amount of temperature change in the superconducting coil, and the amount of heat input to the superconducting coil when imaging the subject P.

[0038] In step S205, the processing circuit 131 determines whether the feature amount estimated in step S204 is equal to or less than the allowable amount assigned in step S201 using the imaging condition determination function 1325. If the estimated feature amount is greater than the allowable amount, the process proceeds to step S206, and if the estimated feature amount is equal to or less than the allowable amount, the process proceeds to step S208. In step S206, the processing circuitry 131 determines whether or not to perform imaging using the determination function 1323. For example, if there is an input from the operator regarding resetting of the desired imaging conditions, it is determined that there is a change in the conditions, and the process proceeds to step S207. On the other hand, if an instruction to cancel imaging is acquired from the operator, it is determined that imaging related to the imaging sequence acquired in step S202 will not be performed, and the process proceeds to step S210.

[0039] In step S207, the processing circuitry 131 changes the desired imaging conditions using the imaging condition determination function 1325. The desired imaging conditions may be changed by receiving an instruction to change the imaging conditions from the operator and automatically setting alternative imaging conditions using the imaging condition determination function 1325, or by using the desired imaging conditions changed by the operator, for example, imaging parameters input by the operator, as the changed desired imaging conditions. After that, the process returns to step S204 and repeats the same processing. In step S208, the processing circuit 131, using the imaging condition determination function 1325, determines that the desired imaging conditions acquired in step S203 or the desired imaging conditions changed in step S207 are below the allocated tolerance and, for example, are considered to have a low risk of quenching, and therefore determine the desired imaging conditions as the imaging conditions to be used for actual imaging. In step S209, imaging is performed by the MRI apparatus 1 based on the determined imaging conditions.

[0040] In step S210, the processing circuit 131 determines whether all imaging has been processed, in other words, whether imaging has been completed for all of the imaging sequences used to determine the allocation of allowable amounts in step S201, using the determination function 1323. If all imaging has been completed, the processing ends, and if not all imaging has been processed, the processing proceeds to step S211. In step S211, the processing circuit 131 selects an imaging sequence for the next image capture using the selection function 1317, and the process returns to step S203 to repeat the same processing.

[0041] 2, after the execution of imaging in step S208, subsequent imaging can be planned even during imaging, so that each imaging plan may be executed before the current imaging is completed. Also, since an allowable amount is assigned to each imaging in step S201, imaging conditions may be determined in advance for multiple imaging in the target period, and then multiple imaging may be executed consecutively under the determined imaging conditions.

[0042] Next, the details of the calculation process of the allowable amount in step S201 will be described with reference to the flowchart of FIG. In step S301, the processing circuitry 131 acquires imaging information, magnet information, and a target period using the calculation function 1315. The imaging information includes, for example, the type of imaging (imaging sequence), the number of times, and the pattern of the imaging sequence, including rest times. The magnet information includes, for example, the current temperature of the static magnetic field magnet, the temperature in thermal equilibrium of the structure supporting the superconducting coil, the critical temperature of the static magnetic field magnet at which quenching occurs, the thermal characteristics of the static magnetic field magnet, such as the heat capacity of the coil, and the cooling capacity of the refrigerator.

[0043] Note that values ​​that change over time, such as the cooling capacity of a refrigerator, may be updated based on long-term changes in the temperature in a thermal equilibrium state while the device is not imaging. Furthermore, the critical temperature of the static magnetic field magnet varies depending on the magnetic field strength of the environment in which the static magnetic field magnet is placed, so it may be determined based on the position of the temperature sensor that measures the temperature of the static magnetic field magnet and the results of actual measurements by the temperature sensor. Furthermore, if a refrigerant such as liquid helium is used to cool the static magnetic field magnet, the pressure of the space filled with the refrigerant also affects the cooling capacity, so information such as the pressure of the refrigerant may be included in the magnet information.

[0044] The target period is the period for which the allowable capacity is allocated, in other words, the unit period for which the allowable capacity is calculated. The target period should preferably include a downtime period during which the temperature of the superconducting coil and the structure supporting the superconducting coil returns to the steady state when no imaging is being performed, such as the examination time for one patient, one day, or one week.

[0045] The processing circuitry 131 may acquire the imaging information, magnet information, and information regarding the target period input by the user before executing the allowable amount allocation process, or may automatically acquire the imaging information and target period included in the scheduled examination order stored in a RIS (Radiology Information System) or the like.

[0046] In step S302, the processing circuitry 131 calculates the amount of heat that can be cooled based on the imaging information, magnet information, and target period using the calculation function 1315. For example, the processing circuitry 131 calculates the amount of heat that can be cooled at the limit where quenching does not occur, based on the amount of heat generated when multiple imaging sessions set during the target period are performed.

[0047] In step S303, the processing circuitry 131 uses the calculation function 1315 to calculate the allowable heat input to the superconducting magnet for each of the multiple imaging sequences, i.e., for each imaging, based on the amount of heat that can be cooled. Specifically, for example, the allowable amount can be allocated to each imaging by dividing the amount of heat that can be cooled by the number of imaging. The multiple imaging sequences assumed here may have the same imaging conditions or different imaging conditions. If the multiple imaging sequences are of the same imaging sequence type and have the same imaging conditions, the allowable heat amount can be set equal for each imaging.

[0048] Note that the amount of heat generated often varies significantly depending on the type of imaging sequence. Therefore, a weighted value corresponding to the amount of heat generated by imaging may be assigned to each imaging sequence as an allowable amount depending on the type of imaging sequence. Specifically, for example, Echo Planar Imaging (EPI), which rapidly reverses the positive and negative polarities of a readout gradient magnetic field to collect multiple echo signals, generates a large amount of heat. Therefore, a larger weight may be assigned to a diffusion-weighted imaging sequence using EPI or imaging using the Blood Oxygenation Level Dependent (BOLD) method of functional MRI (fMRI). Furthermore, for examinations that generate a large amount of heat, such as EPI, a maximum number of times the procedure can be performed within a target period may be set. This is effective in preventing operator confusion and a decrease in examination efficiency.

[0049] Furthermore, the processing circuit 131 may calculate the maximum number of imaging attempts during the target period based on the amount of heat that can be cooled calculated in step S302 using the calculation function 1315. For example, if the allowable amount of each imaging sequence that has been averaged and assigned by the calculation function 1315 is equal to or less than a threshold, there is a possibility that imaging cannot be performed while maintaining quality. Therefore, by calculating the maximum number of imaging attempts that can maintain quality and presenting it to the operator, the operator can be prompted to reduce the number of imaging attempts during the target period.

[0050] Next, a modified example of the operation of the MRI apparatus 1 according to this embodiment will be described with reference to the flowchart of FIG. The flowchart shown in FIG. 4 is the same as FIG. 2 except for steps S401 and S402, and therefore the description thereof will be omitted here.

[0051] In step S401, the processing circuitry 131 calculates the current value of the tolerance using the calculation function 1315. This is because, in the case of a feature quantity that changes over time, such as the current temperature of a static magnetic field magnet, the temperature may have changed since the tolerance allocation process was performed in step S201. Therefore, by calculating the current value of the tolerance, it is possible to more accurately determine, for example, the risk of a quench occurring due to heat input to a superconducting coil. In step S402, the processing circuitry 131 uses the estimation function 1321 to estimate the limit imaging conditions, which are the limit imaging conditions under which imaging can be performed in the imaging sequence acquired in step S202, based on the current value of the allowable amount.

[0052] By estimating the limit imaging conditions within a range that does not exceed the allowable amount, the imaging conditions that can be input by the operator can be limited to those within a range that does not exceed the allowable amount. Note that the processes from step S204 to step S208 may be executed or omitted. That is, since the imaging conditions acquired in step S203 are imaging conditions within a range that does not exceed the allowable amount, imaging in step S209 may be executed after the process of step S203.

[0053] In step S203, the processing circuitry 131 may use the input restriction function 1327 to set restrictions on the input values ​​of imaging parameters related to the desired imaging conditions from the operator based on the marginal imaging conditions.

[0054] Next, details of the process of estimating the limit imaging condition in step S402 will be described with reference to the flowchart of FIG. In step S501, the processing circuitry 131, using the estimation function 1321, obtains the allowable amount allocated to the target imaging sequence. In step S502, the processing circuitry 131 calculates limit values ​​of imaging conditions, i.e., limit imaging conditions, based on the heat generation amount database using the estimation function 1321. The heat generation amount database is a database that stores the correspondence between imaging conditions and heat generation amounts, and is stored in, for example, the storage device 129 or an external storage device. Specifically, the processing circuitry 131 calculates limit values ​​of imaging conditions related to heat generation, such as TR (Repetition time), slice thickness, and spatial resolution, as limit imaging conditions based on the heat generation amount database, the allowable amount acquired in step S301, and information including the imaging type and cross-sectional direction using the estimation function 1321.

[0055] Next, an example of calculating the calorific value required to generate the calorific value database will be described with reference to FIG. Imaging using the MRI apparatus 1 involves various imaging conditions, such as the type of imaging (imaging sequence), cross-sectional direction, TR, and slice thickness, and various imaging conditions are possible depending on the imaging purpose. However, since it takes a very long time to actually measure the heat generation amount, it is not realistic to actually measure the heat generation amount under all possible imaging conditions.

[0056] Therefore, in step S601 shown in FIG. 6, three gradient magnetic field waveforms for the Gx, Gy, and Gz directions are generated based on imaging conditions such as the type of imaging method, cross-sectional direction in imaging, TR, and slice thickness. In step S602, time-series data of three gradient magnetic field waveforms when imaging is performed according to the imaging sequence is acquired.

[0057] In step S603, each of the time series data of the gradient magnetic field waveform is Fourier transformed to calculate frequency component data of each of the gradient magnetic field waveforms. In step S604, the heat generation amount per unit time is estimated from the frequency component data of the gradient magnetic field waveform calculated in step S603 using the transfer function related to heat generation for the gradient magnetic field waveforms of Gx, Gy, and Gz actually measured in advance and the information on the imaging time, and the heat generation amount for the entire imaging sequence is estimated from the information on the imaging time. By saving the above results in a heat generation amount database, a heat generation amount database can be generated and the heat generation amount according to the imaging conditions can be calculated.

[0058] Next, an example of the transfer function used to calculate the heat generation amount in step S604 will be described with reference to FIG. 7 is a graph showing the heat generation amount versus frequency component for each of the three gradient magnetic fields Gx, Gy, and Gz. The vertical axis represents the heat generation amount, and the horizontal axis represents the frequency component. The solid line represents the heat generation amount for the gradient magnetic field Gx, the dashed line represents the heat generation amount for the gradient magnetic field Gy, and the solid line represents the heat generation amount for the gradient magnetic field Gz.

[0059] The transfer function is measured in the form of a transfer function for each of three gradient magnetic fields, which represents the relationship between the frequency components and the amount of heat that heats the superconducting coil and the supporting structure for the superconducting coil when a gradient magnetic field is applied in advance, for example, when the MRI apparatus 1 is installed or shipped. To calculate the transfer function, it is sufficient to calculate in advance the amount of heat generated for the imaging conditions assumed in actual imaging.

[0060] If the type of imaging sequence is the same, there is a simple correlation between the amount of heat generated and typical imaging conditions such as TR, number of slices, spatial resolution, etc. Therefore, by determining standard imaging conditions for each imaging sequence and measuring the amount of heat generated when imaging is performed under those imaging conditions, it is possible to determine the limiting imaging conditions under which imaging can be performed without the risk of quenching by comparing with the standard imaging conditions.

[0061] The processing circuitry 131 may use the presentation function 1329 to present to the operator the information calculated according to the flowcharts shown in FIGS. An example of presenting information to the operator will be described with reference to FIG. 8 shows an example of information displayed on the display 127 of the MRI apparatus 1, the operator's operation terminal, and an external device, and may be displayed together with, for example, a setting screen for imaging parameters. It shows the imaging capacity, feature values ​​estimated based on desired imaging conditions, and the fulfillment rate of the feature values ​​relative to the capacity. In the example of FIG. 8, the fulfillment rate is 60%, so by understanding this information, the operator can recognize that there is still some margin up to the capacity and that better desired imaging conditions can be set.

[0062] The imaging management process according to this embodiment may be set as a default in the MRI apparatus 1, or the operator may be able to switch between the normal mode and the imaging management mode according to this embodiment. For example, when an imaging order is made for a serious emergency patient and the operator wants to perform high-quality imaging of the patient under good imaging conditions without considering subsequent imaging, the operator can switch to the normal mode to perform imaging without any restrictions on the amount of heat generated during the imaging. For example, a button for switching between the normal mode and the imaging management mode according to this embodiment may be provided on the imaging condition setting screen, and the operator may change from the imaging management mode to the normal mode by touching or clicking the button. When changing from the imaging management mode to the normal mode, a confirmation screen including a message such as "This may make it impossible to take images in the future or may worsen the imaging conditions. Are you sure?" may be displayed to prompt the operator for confirmation.

[0063] Next, a simulation result using an MRI apparatus that performs imaging management according to this embodiment will be described with reference to FIGS. 9A and 9B. Figures 9A and 9B show examples of heat input and temperature changes for each imaging sequence when 16 cases are examined in one day, based on a simulation performed using an MRI device that assumes a conduction-cooled superconducting magnet.

[0064] Specifically, the target period is assumed to be one day (24 hours), with 16 people being examined, with one 25-minute scan per person during the day and a 5-minute break. The imaging schedule also assumes no imaging for 16 hours at night. The thermal equilibrium temperature is assumed to be 5.35 [K], and the critical temperature at which the risk of quenching increases is assumed to be 6 [K]. The upper part of Figure 9A shows the amount of heat [W] per unit time, and the lower part of Figure 9A shows the temperature changes in the superconducting coil and the structure supporting the superconducting coil.

[0065] As shown in Figure 9A, in the imaging management of the MRI apparatus 1 according to this embodiment, imaging conditions can be set to evenly allocate the heat generated in 16 examinations in one day, so that imaging conditions can be set to a heat amount of 1.4 [W] x 25 [min] = 2.1 [kJ] per examination from the first scan.

[0066] Figure 9B shows the results of a simulation using an MRI system that, like Figure 9A, assumes a static magnetic field magnet with conduction cooling. Figure 9B shows an example of the heat input and temperature change for each scan when five relatively high-intensity (high-heat-generating) scans are performed per day with a gap between scans. Specifically, the assumed period is one day (24 hours), with one scan per patient per day, followed by a 35-minute break, for five scans, and no scans for 16 hours overnight. As with Figure 9A, the thermal equilibrium temperature is assumed to be 5.35 [K], and the critical temperature at which the risk of quenching increases is assumed to be 6 [K].

[0067] As shown in Figure 9B, in the imaging management of the MRI apparatus 1 according to this embodiment, imaging conditions can be set so that the heat generated in five examinations in one day is evenly distributed, so that imaging conditions can be set to a heat amount of 3.0 [W] x 25 [min] = 4.5 [kJ] per examination from the first scan.

[0068] Next, as a comparative example, simulation results using a conventional method without image capture management are shown in FIGS. 10A and 10B. The simulation conditions for Figures 10A and 10B are the same as those for Figures 9A and 9B, respectively. As shown in Figure 10A, with the conventional method, in the first imaging session, a single 25-minute session is sufficient to reach the critical temperature of 6 K, requiring imaging up to a heat energy of 9.0 W x 25 min = 13.5 kJ. If imaging is performed under these conditions that reach the maximum heat energy limit, the internal temperature will approach 6 K in the first imaging session. Therefore, in subsequent imaging sessions, only a heat energy of 1.287 W x 25 min = 1.93 kJ can be generated to avoid the risk of quenching.

[0069] In Figure 10B, the first imaging can capture up to 13.5 kJ of heat, but if imaging is performed under these conditions, the internal temperature will approach 6 K in the first imaging, and in subsequent imaging tests, only 2.385 W x 25 minutes = 3.58 kJ of heat can be generated to avoid the risk of quenching.

[0070] According to the present embodiment described above, the allowable heat amount for multiple scans during a target period is calculated, and scans are prompted to be performed under scan conditions that result in a heat amount less than the allowable amount for each scan. This allows for the pacing of multiple scans to be considered, allowing for high-quality scans on average, improving the overall quality of scans during the target period. Furthermore, this reduces the risk of quenching, and allows for efficient scans without unnecessary rework, such as resetting scan conditions. Furthermore, according to a modified example of this embodiment, the operator can be prompted to input imaging conditions within the allowable range for each imaging session, thereby eliminating or reducing the need to retake images or reset conditions, allowing for more efficient examinations.

[0071] Furthermore, by displaying information that serves as a guide for determining the imaging conditions when inputting the imaging conditions, the operator can quickly determine the imaging conditions without worrying about quenching caused by heat generation. Furthermore, by limiting the input so that an upper limit is set on the total number of imaging sessions during the target period and no more imaging sessions than the cooling capacity is accepted, the number of examinations possible per target period can be recognized at an early stage, allowing for efficient examination planning. In other words, according to this embodiment, work can be efficiently carried out, such as reasonably arranging examination appointments, at clinical testing sites.

[0072] According to at least one of the embodiments described above, it is possible to support efficient inspections while ensuring quality.

[0073] In addition, each function according to the embodiments can be realized by installing a program for executing the corresponding process on a computer such as a workstation and expanding the program in memory. In this case, the program for causing a computer to execute the corresponding method can be stored and distributed on a storage medium such as a magnetic disk (such as a hard disk), an optical disk (such as a CD-ROM, DVD, or Blu-ray (registered trademark) disk), or a semiconductor memory.

[0074] Although several 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 within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0075] 1 MRI machine 2 Magnet Management Unit 20 Temperature measurement circuit 101 Static Magnetic Field Magnet 103 Gradient magnetic field coil 105 Gradient magnetic field power supply 107 Sleeper 109 Bed control circuit 111 Bore 113 Transmitting circuit 115 Transmitting Coil 117 Receiving Coil 119 Receiving circuit 121 Sequence control circuit 123 Bus 125 Interface 127 Display 129 Storage device 131 Processing circuit 1311 System Control Functions 1313 Image generation function 1315 Calculation Function 1317 Selection Function 1319 Reception Function 1321 Estimation Function 1323 Judgment Function 1325 Imaging condition determination function 1327 Input restriction function 1329 Presentation function

Claims

1. a calculation unit that calculates an allowable amount of heat input to a superconducting magnet to prevent a quench from occurring, the allowable amount being assigned to each of a plurality of imaging operations scheduled for a target period; A determination unit that determines imaging conditions based on the allowable amount in each imaging operation; Equipped with The calculation unit calculates the allowable amount to be allocated to each of the imaging operations based on an amount of heat that can be cooled during the target period; A magnetic resonance imaging apparatus, wherein the allowable amount is an average value obtained by dividing the amount of heat that can be cooled by the number of images.

2. A calculation unit that calculates an allowable amount of heat input to a superconducting magnet to prevent quenching, which is assigned to each of a plurality of imaging operations scheduled during a target period; A determination unit that determines imaging conditions based on the allowable amount in each imaging operation; Equipped with The calculation unit calculates a maximum number of imaging operations based on an amount of heat that can be cooled during the target period.

3. a reception unit for receiving a desired imaging condition desired by an operator; and an estimation unit that estimates a feature amount related to heat input to the superconducting magnet when imaging is performed under the desired imaging conditions, 3. The magnetic resonance imaging apparatus according to claim 1, wherein the determination unit determines the desired imaging condition as the imaging condition when the feature amount is equal to or smaller than the allowable amount.

4. 4. The magnetic resonance imaging apparatus according to claim 3, further comprising an input limiting unit that limits an input value of an imaging parameter related to the desired imaging condition from the operator based on the allowable amount.

5. 5. The magnetic resonance imaging apparatus according to claim 3, further comprising a display unit that displays the allowable amount to the operator.

6. The magnetic resonance imaging apparatus according to claim 5 , wherein the presentation unit further presents the feature amount and a fulfillment rate of the feature amount with respect to the allowable amount.

7. The magnetic resonance imaging apparatus according to claim 1 , wherein the calculation unit calculates the allowable amount to be allocated to each of the imaging operations based on an amount of heat that can be cooled during the target period.

8. 8. The magnetic resonance imaging apparatus according to claim 7, wherein the allowable amount is an average value obtained by dividing the amount of heat that can be cooled by the number of images.

9. A calculation unit that calculates an allowable amount of heat input to a superconducting magnet to prevent quenching, which is assigned to each of a plurality of imaging operations scheduled during a target period; A determination unit that determines imaging conditions based on the allowable amount in each imaging operation; Equipped with A magnetic resonance imaging apparatus in which a value weighted according to a heat generation amount based on a type of imaging sequence of each imaging is assigned to each imaging as the allowable amount.

10. The magnetic resonance imaging apparatus according to claim 1 , wherein the calculation unit calculates a maximum number of imaging operations based on an amount of heat that can be cooled during the target period.

11. Calculating the allowable amount of heat input to the superconducting magnet to prevent quenching, which is allocated for each of the multiple imaging operations scheduled during the target period; determining imaging conditions based on the allowable amount in each imaging; Equipped with calculating the allowable amount includes calculating the allowable amount to be allocated to each of the imaging operations based on an amount of heat that can be cooled during the target period; The imaging management method, wherein the allowable amount is an average value obtained by dividing the amount of heat that can be cooled by the number of images captured.

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