JP2015150181A - Magnetic resonance imaging apparatus and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging apparatus capable of suppressing the deterioration of image quality due to speeding-up or maintaining/improving the image quality.SOLUTION: The magnetic resonance imaging apparatus comprises: a static magnetic field generation unit for generating a static magnetic field in a measurement space which receives a subject; a gradient magnetic field generation unit including a gradient magnetic field coil which generates a gradient magnetic field in the measurement space and a gradient magnetic field power source 32 which supplies a current to the gradient magnetic field coil; an irradiation coil for generating a high-frequency magnetic field which is applied to the subject; a receiving coil for detecting nuclear magnetic resonance signals generated by the subject; a display unit for displaying an image generated based on the received nuclear magnetic resonance signals; and a gain determination unit for determining the gain of the gradient magnetic field power source 32 to output gain information. In the configuration, the gain information output by the gain determination unit is input to the gradient magnetic field power source 32, and the gradient magnetic field power source 32 uses the determined gain to generate a current to be supplied to the gradient magnetic field coil.

Description

  The present invention relates to a magnetic resonance imaging apparatus.

  A magnetic resonance imaging (hereinafter referred to as MRI) apparatus measures a nuclear magnetic resonance (hereinafter referred to as NMR) signal generated by a nuclear spin that constitutes a subject, in particular, a tissue of a human body. It is an apparatus that images the form and function of the head, abdomen, limbs, etc. two-dimensionally or three-dimensionally. In imaging for the above-described imaging by the MRI apparatus, the NMR signal is given a phase encoding that differs depending on the gradient magnetic field, is frequency-encoded, and is measured as time-series data. The measured NMR signal is subjected to two-dimensional or three-dimensional Fourier transform to generate an MRI image. If the time required for scheduled MRI imaging can be shortened, the burden on the subject can be reduced, and further the efficiency of the operator's work can be improved. Japanese Patent Application Laid-Open No. 2004-133867 describes a technique related to speeding up of the gradient magnetic field generator accompanying speeding up of the imaging sequence of the MRI apparatus.

JP 2001-137214 A

  In recent years, there has been a great demand for speeding up the imaging operation of an MRI apparatus, and a proposal for realizing speeding up has been made, for example, as described in Patent Document 1. Patent Document 1 discloses a technique for improving the response of the gradient magnetic field intensity by compensating for the time delay of the control system. Although this technique is very effective, there is a demand for further improvement, and it is very important to solve the problems associated with increasing the speed of the MRI apparatus and answer market needs.

  In general, in an MRI apparatus, there is a fear that the quality of an obtained MRI image may be lowered if an attempt is made to enhance the imaging operation. In the MRI apparatus, it is desirable not only to speed up the photographing operation, but also to improve the quality of the photographed image while suppressing deterioration in the quality of the photographed image, or preferably in addition to increasing the speed.

  An object of the present invention is to provide an MRI apparatus capable of suppressing deterioration in image quality due to high-speed imaging operations, or maintaining or improving image quality, or a control method thereof.

  In order to solve the above problems, a magnetic resonance imaging apparatus to which the present invention is applied includes a static magnetic field generation unit that generates a static magnetic field in a measurement space that houses a subject, and a gradient magnetic field that generates a gradient magnetic field in the measurement space. A gradient magnetic field generator having a gradient magnetic field power source for supplying current to the coil and the gradient magnetic field coil, an irradiation coil for generating a high frequency magnetic field to be irradiated to the subject, and the subject generated based on the irradiation of the high frequency magnetic field A receiving coil for receiving the nuclear magnetic resonance signal, a display for displaying an image generated based on the received nuclear magnetic resonance signal, a gain determining unit for determining gain of the gradient magnetic field power source and outputting gain information The gain information output from the gain determination unit is input to the gradient magnetic field power supply, and the gradient magnetic field power supply operates with the determined gain and the gradient Generating a current supplied to the field coil, characterized in that.

  It is possible to obtain an MRI apparatus or a control method thereof that can suppress the deterioration of the image quality accompanying the increase in the speed of the photographing operation or can maintain or improve the image quality.

1 is a block diagram showing an overall configuration of an MRI apparatus that is an embodiment of the present invention. It is explanatory drawing explaining an example of the magnetic field coordinate system of the MRI apparatus described in FIG. It is a block diagram which shows an example of the gradient magnetic field power supply described in FIG. It is a block diagram which shows an example of a structure of the X-axis gradient magnetic field power supply as a typical example of the gradient magnetic field power supply of FIG. It is explanatory drawing for demonstrating the database regarding the gain of the current control circuit in normal imaging conditions. It is explanatory drawing for demonstrating the database regarding the gain of the current control circuit in case imaging conditions are high-speed imaging. It is explanatory drawing for demonstrating the database regarding the gain of the current control circuit in case the current pattern of the electric current for slice selection is special. It is explanatory drawing for demonstrating an example of the electric current pattern of the electric current supplied to each gradient magnetic field coil described in FIG. It is explanatory drawing for demonstrating an example of the electric current pattern in the special case described in FIG. 5 is a flowchart illustrating an example of an operation of a gain determination unit described in FIG. 4. FIG. 11 is a flowchart showing another operation example of the flowchart shown in FIG. 10. FIG. 12 is a flowchart illustrating still another operation example of the flowchart illustrated in FIG. 11.

  Hereinafter, an embodiment (hereinafter referred to as an example) of an MRI apparatus to which the present invention is applied will be described with reference to the accompanying drawings. In the embodiments described below, components having substantially the same function, substantially the same configuration, and substantially the same action are denoted by the same reference numerals, and repeated description thereof may be omitted. In addition, the embodiments described below perform various functions, solve various problems, and have various effects. Problems to be solved by the following embodiments are not limited to the contents described in the column of problems to be solved by the above-described invention, and various problems can be solved. Therefore, in the following embodiments, the present invention also describes solutions for problems other than those described in the column of problems to be solved by the invention. In addition, the embodiments described below can also exhibit effects other than the contents described in the column of the effects of the invention described above. In addition to the contents described in the “Effects of the Invention” section, the effects of the following embodiments will be described in the following embodiments.

  FIG. 1 is a block diagram showing the overall configuration of an embodiment of an MRI apparatus to which the present invention is applied. The MRI apparatus 100 is an apparatus for obtaining various two-dimensional and three-dimensional images including tomographic images and stereoscopic images of the subject 11 using the NMR phenomenon, and generates a measurement space for the subject 11. For this purpose, a magnetic field generator 20 is provided. The magnetic field generation unit 20 includes a static magnetic field generation unit 22 and a gradient magnetic field generation unit 30. The gradient magnetic field generation unit 30 is based on a gradient magnetic field power source 32 that supplies a current for generating a gradient magnetic field and a supplied current. A gradient magnetic field coil 34 for generating a gradient magnetic field. The gradient magnetic field coil 34 further has an X-axis gradient magnetic field coil 342, a Y-axis gradient magnetic field coil 344, and a Z-axis gradient magnetic field coil 346. And a Y-axis gradient magnetic field power source 324 and a Z-axis gradient magnetic field power source 326.

  The MRI apparatus 100 further includes a sequencer 12 that performs control for generating an NMR phenomenon, such as an imaging operation, and control for detecting an NMR signal generated based on the NMR phenomenon, and a high-frequency pulse ( A radio frequency pulse (hereinafter referred to as an RF pulse) generating unit 40, a receiver 50 for receiving an NMR signal, and a central processing unit (hereinafter referred to as a CPU) 14 are generated to generate an MRI image. And a processing unit 60 that performs various controls in the MRI apparatus 100. The MRI apparatus 100 is further provided with a bed 80 provided with a top plate 82 for placing the subject 11 and moving the subject 11 in a predetermined positional relationship with respect to the measurement space.

  The magnetic field generator 20 is provided with the static magnetic field generator 22 and the gradient magnetic field generator 30 as described above, and includes a vertical magnetic field method and a horizontal magnetic field method. In the case of the vertical magnetic field method, the static magnetic field generation unit 22 generates a uniform static magnetic field in a direction perpendicular to the body axis in the space around the subject 11. On the other hand, in the horizontal magnetic field method, the static magnetic field generator 22 generates a uniform static magnetic field in the body axis direction. In both of the above methods, as the static magnetic field generation unit 22, a permanent magnet type, normal conduction type, or superconducting type static magnetic field generation source is disposed around the subject 11. The present invention can be applied to various systems including these systems.

  The gradient magnetic field generating unit 30 drives a gradient magnetic field coil 34 that applies a gradient magnetic field in three coordinate directions of the coordinate system of the MRI apparatus 100, for example, the X axis, the Y axis, and the Z axis, which are stationary coordinate systems. A gradient magnetic field power source 32 is provided. The relationship between an example of the coordinate system and the subject 11 is shown in FIG. In the example shown in FIG. 2, the body axis direction of the subject 11, which is the movement axis in the longitudinal direction of the top plate 82 of the bed 80 on which the subject 11 is placed, is the Z-axis direction, and the gravity direction of the subject 11 is the Y-axis. The direction and the left-right direction of the subject 11 are the X-axis direction. The application of the present invention is not limited to the coordinate system and can be applied to various coordinate systems. The coordinate system shown in FIG. 2 will be described below as a representative example.

  The gradient magnetic field generation unit 30 generates a gradient magnetic field in three axes directions of the X axis, the Y axis, and the Z axis, as the gradient magnetic field coil 34, an X axis gradient magnetic field coil 342, a Y axis gradient magnetic field coil 344, and a Z axis gradient. A magnetic field coil 346 is provided. The gradient magnetic field generating unit 30 also includes an X-axis gradient magnetic field power source 322 for driving the X-axis gradient magnetic field coil 342 and a Y-axis gradient magnetic field power source 324 for driving the Y-axis gradient magnetic field coil 344 as the gradient magnetic field power source 32. A Z-axis gradient magnetic field power source 326 for driving the Z-axis gradient magnetic field coil 346 is provided. With the respective gradient magnetic fields generated by the X-axis gradient magnetic field coil 342, the Y-axis gradient magnetic field coil 344, and the Z-axis gradient magnetic field coil 346, MRI imaging of a predetermined imaging section can be performed. The slice plane that is the imaging section can be set for any of the X-axis, Y-axis, and Z-axis. For example, if the plane perpendicular to the X-axis is the slice plane, the slice plane is the Y-axis or Z-axis direction. Is the phase encoding direction or the frequency encoding direction. For example, when a plane perpendicular to the Z axis is a slice plane, the X axis or the Y axis is the phase encoding direction or the frequency encoding direction.

  A target current value command for generating a gradient magnetic field pulse, which is the gradient magnetic field described above, is sent from the sequencer 12 to the X-axis gradient magnetic field power source 322, the Y-axis gradient magnetic field power source 324, and the Z-axis gradient magnetic field power source 326 of the gradient magnetic field power source 32. Each is sent. Accordingly, the X-axis gradient magnetic field coil 342, the Y-axis gradient magnetic field coil 344, and the Z-axis gradient magnetic field coil 346 each generate a gradient magnetic field pulse. A slice direction gradient magnetic field pulse Gs is generated in a direction orthogonal to the imaging section to set a slice plane for the subject 11, and the phase encoding direction gradient magnetic field pulse is set in the remaining two directions orthogonal to the slice plane and orthogonal to each other. Gp and frequency encoding direction gradient magnetic field pulse Gf are generated. As a result, position information in each direction can be encoded into the NMR signal generated by the subject 11 based on the RF pulse generated by the irradiation coil 48, and MRI can be performed from the received NMR signal based on the encoded position information. An image can be generated.

  The sequencer 12 repeatedly controls the gradient magnetic field power supply 32 and the transmission unit 40 according to a sequence determined by the set imaging conditions, and an RF pulse and a gradient magnetic field pulse, which are high-frequency magnetic field pulses, are repeatedly generated according to the sequence and applied to the subject 11. Is done. Further, the sequencer 12 also sends various commands necessary for collecting tomographic image data of the subject 11 to the receiving unit 50. The receiving unit 50 receives and processes the NMR signals generated by the subject 11, and performs image processing. The data is transmitted to the processing unit 60 as digital data for generation or the like. Note that the entire MRI apparatus 100 operates according to the control of the processing unit 60 including the CPU 14, and the sequencer 12 operates according to a command from the processing unit 60.

  The transmission unit 40 irradiates the subject 11 with an RF pulse according to the sequencer 12 in order to cause nuclear magnetic resonance to occur in the nuclear spins of the atoms constituting the biological tissue of the subject 11. The transmitter 40 includes a high frequency oscillator 42, a modulator 44, a high frequency amplifier 46, and an irradiation coil 48. The RF pulse output from the high-frequency oscillator 44 is amplitude-modulated by the modulator 44 at a timing according to a command from the sequencer 12, and the amplitude-modulated RF pulse is amplified by the high-frequency amplifier 46 and placed close to the subject 11. By supplying to the irradiation coil 48, the RF coil is irradiated from the irradiation coil 48 to the measurement space where the subject 11 is located. Atoms constituting the living tissue of the subject 11 generate NMR signals in accordance with the irradiation of the RF pulse.

  The receiving unit 50 includes a receiving coil 52 for receiving NMR signals, a signal amplifier 54 for amplifying the received high frequency signal, a quadrature phase detector 56, and an A / D converter 58. An NMR signal generated by the subject 11 due to the electromagnetic wave irradiated from the irradiation coil 48 of the transmission unit 40 is detected by the reception coil 52 arranged close to the subject 11 and amplified by the signal amplifier 54. The amplified NMR signal is divided into two orthogonal signals by the quadrature phase detector 56 at the timing according to the command from the sequencer 12, and each is converted from analog to digital quantity by the A / D converter 58 to generate an image. It is sent to the processing unit 60 having a function.

  As an example, in FIG. 1, the irradiation coil 48 and the gradient magnetic field coil 34 on the transmission side are within the static magnetic field space of the static magnetic field generating unit 22 into which the subject 11 is inserted, and the subject is in the vertical magnetic field system. In the case of a horizontal magnetic field system, the object 11 is installed so as to surround the object 11. The receiving coil 52 on the receiving side is disposed so as to face or surround the subject 11.

  The processing unit 60 controls the entire MRI apparatus 100, processes various data including image generation based on imaging, displays processing results, stores various data including images, processes related to various inputs, and other systems. Send and receive information. The processing unit 60 includes various devices, but a typical configuration includes an external storage device 61 including an optical disk 62 and a magnetic disk 64, an internal memory 66, a liquid crystal, a CRT (CRT), and the like. An output device 96 having a display 98 and a printer 99, a pointing device 92, a keyboard 94, an input device 91 having a touch panel provided on the display 98 (not shown), a CPU 14 for controlling and calculating, and the like. The input device 91 and the output device 96 constitute an input / output device 90.

  For example, when a control signal is sent from the sequencer 12 to the gradient magnetic field power source 32 or the modulator 44 in accordance with the imaging conditions input from the input / output device 90 and an NMR signal is output from the subject 11 in accordance with the RF pulse emitted from the irradiation coil 48. The receiving coil 52 receives the NMR signal, and the data related to the image is input from the receiving unit 50 to the CPU 8 by the operation of the signal amplifier 54, the quadrature phase detector 56, and the A / D converter 58. The CPU 14 performs processing such as signal processing of data relating to the input image and generation of an image, and processing for displaying an image such as a tomographic image of the subject 11 on the display 98 as a result. If necessary, necessary data is recorded on the optical disk 62 or the magnetic disk 64 of the external storage device 61 according to the setting or according to the instruction of the operator.

  Regarding the imaging of the image of the subject 11, imaging conditions, data processing conditions, and imaging operations are performed by operating an input device 91 including a touch panel (not shown) provided on the display 98. In these operations, the operator can interactively control various processes of the MRI apparatus while viewing the display contents on the display 98. Further, information that assists the operation is displayed on the display 98 according to the state, and the operation is performed by inputting an instruction based on the content displayed on the display 98. As described above, display according to the operation state is performed, and input according to the display is performed, so that it is easy to reduce erroneous operations and detect erroneous operations.

  A radionuclide to be imaged of a commonly used MRI apparatus including the MRI apparatus 100 to which the present invention is applied is a hydrogen nucleus (proton) that is a main constituent material of a subject as widely used in clinical practice. By imaging information about the spatial distribution of proton density and the spatial distribution of the relaxation time of excited states, the form or function of measurement positions such as the human head, abdomen, and extremities can be imaged two-dimensionally or three-dimensionally. can do.

  3 is a block diagram showing an example of the gradient magnetic field power supply 32 shown in FIG. 1. The gradient magnetic field power supply 32 includes an X-axis gradient magnetic field power supply 322 that supplies a supply current 3234 to the X-axis gradient magnetic field coil 342, and a Y-axis. A Y-axis gradient magnetic field power source 324 that supplies a supply current 3254 to the gradient magnetic field coil 344 and a Z-axis gradient magnetic field power source 326 that supplies a supply current 3274 to the Z-axis gradient magnetic field coil 346 are provided. As shown in FIG. 3 as an example, each gradient magnetic field power supply has the same circuit configuration. The X-axis gradient magnetic field power supply 322 includes a gain determination unit 3222, a delay circuit 3226, a current control circuit 3228, and a current. An amplifier 3232 and a current detector 3236 are included. The Y-axis gradient magnetic field power supply 324 includes a gain determination unit 3242, a delay circuit 3246, a current control circuit 3248, a current amplifier 3252, and a current detector 3256. Further, the Z-axis gradient magnetic field power supply 326 includes a gain determination unit 3262, a delay circuit 3266, a current control circuit 3268, a current amplifier 3272, and a current detector 3276.

  Note that each of the current control circuit 3228, the current control circuit 3248, and the current control circuit 3268 has a PID (proportional / integral / differential) control circuit, which is a kind of feedback control, as described below as an example. The gain information indicating the gain determined by the gain determination unit 3222, the gain determination unit 3242, and the gain determination unit 3262 included in each gradient magnetic field power supply is used as a gain command 3224, a gain command 3244, and a gain command 3264, respectively. The PID control circuit included in the circuit 3228, the current control circuit 3248, and the current control circuit 3268 is input and set. With these setting operations relating to the gain, the gains of the PID control circuits included in the current control circuit 3228, the current control circuit 3248, and the current control circuit 3268 are respectively determined, and each PID control circuit operates according to the set gain.

  When a control command for performing imaging from the CPU 14 according to the imaging conditions of the MRI apparatus 100 is sent to the sequencer 12, the sequencer 12 sends the X-axis gradient magnetic field power source 322, the Y-axis gradient magnetic field power source 324, and the Z-axis gradient magnetic field power source 326, respectively. A target current command is generated to generate a gradient magnetic field in the axis. The role of the gradient magnetic field in the three directions of the X, Y, and Z axes is determined according to the role of slice selection gradient magnetic field, phase encoding gradient magnetic field, or frequency encoding gradient magnetic field, and the target current value command corresponding to the role. Is generated in the sequencer 12 and sent to the X-axis gradient magnetic field power source 322, the Y-axis gradient magnetic field power source 324, and the Z-axis gradient magnetic field power source 326 as the target current value command 3202, the target current value command 3204, and the target current value command 3206.

  The X-axis gradient magnetic field, the Y-axis gradient magnetic field, and the Z-axis gradient magnetic field play a role of the slice selection gradient magnetic field, phase encode gradient magnetic field, or frequency encode gradient magnetic field. It is decided according to. A control command is sent from the CPU 14 to the sequencer 12 in order to perform an operation for performing imaging based on the above-mentioned role determined based on the MRI imaging conditions, and the gradient magnetic field power source corresponding to the above-described role from the sequencer 12 The target current command is sent to. The target current command 3202 is sent from the sequencer 12 according to the above-mentioned role assigned to the X-axis gradient magnetic field power source 322, and the target current command 3204 is sent from the sequencer 12 to the Y-axis gradient magnetic field power source 324 according to the above-mentioned assigned role. The target current command 3206 is sent from the sequencer 12 to the Z-axis gradient magnetic field power supply 326 according to the above-mentioned role assigned.

  Each gradient magnetic field power supply has a current control circuit 3228 or current control included in each gradient magnetic field power supply in order to improve the responsiveness or accuracy of the supply current 3234, supply current 3254, and supply current 3274 supplied to the respective gradient magnetic field coils. The gain of at least one of the circuit 3248 and the current control circuit 3268, or the gains of all the current control circuits, is controlled according to the imaging conditions or the state of the supply current supplied to each gradient coil. As an example of controlling the gains of the current control circuit 3228, the current control circuit 3248, and the current control circuit 3268 in accordance with the supply current supplied to each gradient coil, the rate of change of the supply current supplied to each gradient coil or the target current value is Can be mentioned. The gain determination unit 3222, the gain determination unit 3242, and the gain determination unit 3262 may receive information on the rate of change of the supply current or the target current value from the sequencer 12 or the CPU 14, respectively, or the gain determination unit 3222, the gain determination unit 3242, The gain determination unit 3262 receives the target current value command 3202, the target current value command 3204, and the target current value command 3206 from the sequencer 12, respectively, and changes in the supply current supplied to the gradient coil based on the received target current value command The rate or target current value may be calculated, and each gain determination unit may determine the gain based on the calculation result.

  In the MRI apparatus 100, the target current value supplied to the X-axis gradient magnetic field coil 342, the Y-axis gradient magnetic field coil 344, and the Z-axis gradient magnetic field coil 346 differs depending on the region of the subject 11 to be imaged or depending on the imaging conditions. For example, when the slice width is set to be small, the target current value supplied to the gradient magnetic field coil that plays the role of slice selection is increased, and control is performed to raise a large current at a high speed and supply it to the gradient magnetic field coil. On the other hand, a state where a small current is raised with high accuracy may occur depending on photographing conditions and the like. The accuracy of the target current value affects the accuracy of the shooting position and the image quality. Therefore, the MRI apparatus 100 is required to control the current value supplied to each gradient coil in a wide range from a minute current to a large current with high accuracy. In the apparatus to which the present invention is applied, an effect capable of sufficiently satisfying such a demand is obtained.

  In the present embodiment, the X-axis gradient magnetic field power source 322, the Y-axis gradient magnetic field power source 324, and the Z-axis gradient magnetic field power source 326 have substantially the same configuration and operate in the same manner. The operation of not only the X-axis gradient magnetic field power source 322 but also the Y-axis gradient magnetic field power source 324 and the Z-axis gradient magnetic field power source 326 will be described. A target current value command 3202, target current value command 3204, and target current value command 3206 for supplying a supply current 3234, a supply current 3254, and a supply current 3274 to each gradient magnetic field coil are supplied from the sequencer 12 to each gradient magnetic field power source. Then, the gain determination unit of each gradient magnetic field power supply detects the amount of change in current.

  FIG. 4 is a block diagram showing a specific example of the X-axis gradient magnetic field power source 322 for supplying the supply current 3234 for driving the X-axis gradient coil 342, and the Y-axis gradient for driving the Y-axis gradient magnetic field coil 344. The Z-axis gradient magnetic field power source 326 that drives the magnetic field power source 324 and the Z-axis gradient magnetic field coil 346 also operates in the same manner. Therefore, the X-axis gradient magnetic field power supply 322 will be described as a representative example. The gain determination unit 3222 includes a calculation unit 3302 that performs processing including calculation processing and search processing, and a data storage unit 3304 that stores data in the form of a database, for example.

  Similarly, the gain determination unit 3242 of the Y-axis gradient magnetic field power supply 324 and the gain determination unit 3262 of the Z-axis gradient magnetic field power supply 326 each include a calculation unit 3302 and a data storage unit 3304. In each gradient magnetic field power supply, for example, an X-axis gradient magnetic field power supply 322 as a representative example, the gain determination unit 3222 detects the magnitude of the target current value based on the target current value command 3202 from the sequencer 12. In the detection of the magnitude of the target current value, the maximum value of the target current value itself may be detected. Instead, the change in the current pattern of the target current value command 3202 supplied from the sequencer 12 to the X-axis gradient magnetic field power supply 322 is detected. The amount may be detected. A target current value command 3202 which is a command from the sequencer 12 has a waveform representing a current pattern to be supplied to the X-axis gradient magnetic field coil 342, such as a current pattern A and a current pattern B shown in FIG. The amount of change in current is larger in the current pattern A in which the target current value is I1 than the current pattern B in which the target current value is I2. The amount of change in current corresponds to the target current value of the current pattern, and the target current value that corresponds to the amount of change in current by detecting the amount of change in current rather than detecting the maximum value of the target current value itself. The calculation unit 3302 can quickly detect the maximum value of the target current value when the maximum value of I1 or the target current value I2 is obtained. This configuration, operation, and effect are the same for the gain determination unit 3222 of the X-axis gradient magnetic field power source 322, the gain determination unit 3242 of the Y-axis gradient magnetic field power source 324, and the gain determination unit 3262 of the Z-axis gradient magnetic field power source 326. The method of obtaining the target current value from the inclination of the target current value command 3204 and the target current value command 3206 from 12 can quickly detect the target current value, and can quickly determine the gain corresponding to the target current value. it can.

  Examples of databases stored in the data storage unit 3304 are described in FIG. 5, FIG. 6, and FIG. Each gradient magnetic field generated by the X-axis gradient magnetic field coil 342, the Y-axis gradient magnetic field coil 344, and the Z-axis gradient magnetic field coil 346 is converted into a gradient magnetic field for slice selection, a gradient magnetic field for phase encoding, and a gradient magnetic field for frequency encoding. Each is assigned by the CPU 14 based on the photographing conditions. The database described in FIGS. 5 to 7 includes, as search items 3306, slice selection current (hereinafter referred to as slice axis), phase encoding current (hereinafter referred to as phase axis), frequency encoding current (hereinafter referred to as frequency). Each item). Depending on which of the gradient magnetic field generated by each gradient coil is assigned to the gradient magnetic field for slice selection, the gradient magnetic field for phase encoding, and the gradient magnetic field for frequency encoding, the slice axis and phase as items of the search item 3306 are assigned. The corresponding item in the axis or frequency axis is selected as a search parameter.

  The current control circuit 3228 includes a PID control circuit as an example, and each PID control circuit includes a proportional circuit 3312, an integration circuit 3314, and a differentiation circuit 3316. When the slice axis, phase axis, or frequency axis, which is the item of the search item 3306, is selected, the stored data relating to the gain is searched according to the item 3308 of the proportional circuit 3312, the integration circuit 3314, and the differentiation circuit 3316 in the selected item. The

  The gain of the current control circuit 3228, for example, the gain for operating the PID control circuit included in the current control circuit 3228 is further selected according to the photographing conditions. For example, in the case of general shooting conditions, the database shown in FIG. 5 is selected, and the gain is determined by searching. When shooting at a higher speed than the general shooting conditions related to FIG. 5, the database shown in FIG. 6 is selected and the gain is searched. If the shooting sequence controlled by the sequencer 12 based on the shooting conditions is faster than a predetermined threshold, it is determined as a high-speed shooting sequence, and the database shown in FIG. 6 is selected. On the other hand, when the shooting sequence is slower than the predetermined threshold, it is determined that the shooting sequence is a general shooting sequence, and the low-speed shooting sequence database shown in FIG. 5 is selected. The databases shown in FIGS. 5 and 6 target the current pattern shown in FIG. 8, and the target value of the current supplied to the gradient coil, that is, the maximum current value of the current pattern is substantially constant. On the other hand, when the target value of the current supplied to the gradient coil does not show a substantially constant state as in the current pattern shown in FIG. 9, but the target value of the current changes as in the pattern shown in FIG. Are classified into special sequences, and the database shown in FIG. 7 is selected and used.

  After one of the databases shown in FIG. 5 to FIG. 7 is selected according to the shooting conditions as described above, the current target value (which may be referred to as the target current value in this specification) further depends on the magnitude of the current. It is detected whether it is a level, and a gain value to be used is searched according to the current level 3310 of the target current value. In order to determine the current level 3310, a plurality of current values or a plurality of changes are classified into a large level, a middle level, and a small level of the current level 3310. For example, two thresholds are provided, with the maximum level being a large level, the lowest level being a low level, and the level between being a medium level. By searching for a gain from the database using the current level 3310 related to the current target value as a search item, each gain corresponding to the item 3308 such as a proportional component, an integral component, or a differential component is retrieved.

  As described above, when the gain database shown in FIGS. 5 to 7 is selected according to the inspection conditions and the Z-axis gradient magnetic field power source 326 is assigned for slice selection, for example, the search item 3306 is used to select the slice axis item. Is further searched using the current level 3310 as a search parameter, and the respective gains of the proportional component, integral component, and differential component are retrieved and determined. The determined proportionality, integral, and differential gains are sent from the gain determination unit 3262 of the Z-axis gradient magnetic field power supply 326 to the current control circuit 3268, and the proportional circuit 3312 and the integration circuit 3314 included in the current control circuit 3268, The gain of the differentiation circuit 3316 is set.

  Such an operation is the same in the gain determining unit 3242 of the Y-axis gradient magnetic field power source 324 and the gain determining unit 3222 of the X-axis gradient magnetic field power source 322, and the corresponding item on the phase axis or frequency axis and the current level 3310. According to, the gains of the proportional component, integral component, and derivative component are retrieved and determined. The determined proportional, integral and differential gains are set in the corresponding current control circuit 3228 or current amplifier 3252, respectively.

  Here, the current control circuit 3228, the current control circuit 3248, and the current control circuit 3268 each have substantially the same configuration and operate in substantially the same manner. An example of a specific configuration of the PID control circuit 3228 as a representative example is shown in FIG. The PID control circuit 3228 includes a proportional circuit 3312, an integration circuit 3314, and a differentiation circuit 3316, and the current of the total value of these outputs is supplied to the current amplifier 3232. The supply current 3234 supplied from the supply current 3234 is measured by the current detector 3236, and the measurement result is added to the addition point 3318. At the addition point 3318, the difference between the output of the current amplifier 3232 and the command value from the target current value command 3202 is calculated, and the difference is controlled to be zero.

  The above has been described with reference to the X-axis gradient magnetic field power supply 322, but the configuration and operation of the current control circuit 3248 of the Y-axis gradient magnetic field power supply 324 and the current control circuit 3268 of the Z-axis gradient magnetic field power supply 326 are substantially the same. The proportional gain KP, integral gain KI, and differential gain KD obtained by the search in FIG. 4 are sent to the proportional circuit 3312, the integral circuit 3314, and the differential circuit 3316 of the current control circuit 3228, respectively. As a result, the gains of the proportional circuit 3312, the integrating circuit 3314, and the differentiating circuit 3316 are determined, and the proportional circuit 3312, the integrating circuit 3314, and the differentiating circuit 3316 operate based on the determined gains, and the target current value command 3202 is faithfully reproduced. The represented current is supplied to the X-axis gradient coil 342.

  In this way, in the circuit shown in FIG. 3, current control is performed by the gain determination unit 3222, the gain determination unit 3242, and the gain determination unit 3262 based on the target current value command 3202, the target current value command 3204, and the target current value command 3206. The gains of the circuit 3228, the current control circuit 3248, and the current control circuit 3268 are set to appropriate values according to the target current value. Note that the delay circuit 3226, the delay circuit 3246, and the delay circuit 3266 are provided to ensure that the gains of the current control circuit 3228, the current control circuit 3248, and the current control circuit 3268 are set. When the operations of the determination unit 3222, the gain determination unit 3242, and the gain determination unit 3262 are performed quickly, there is no need to provide them.

  In the above-described example, the search parameter is calculated based on the target current value command 3202, the target current value command 3204, and the target current value command 3206 by the gain determination unit 3222, the gain determination unit 3242, and the gain determination unit 3262, and the data is stored. Although the database held in the unit 3304 is searched, the search item 3306, the item 3308, and the current level 3310, which are the search parameters calculated by the calculation unit 3302 of FIG. The database shown in FIGS. 5 to 7 stored in the data storage unit 3304 may be searched. Further, the database confidence shown in FIGS. 5 to 7 is provided in the processing unit 60 and the sequencer 12, and the processing unit 60 and the sequencer 12 retrieve the appropriate gain by the method described above, and the obtained gain is obtained from the CPU 14 and the sequencer 12 as a current. They may be directly input to the control circuit 3228, the current control circuit 3248, and the current control circuit 3268, respectively.

  The databases described in FIGS. 5, 6, and 7 are examples of data held in the data storage unit 3304 illustrated in FIG. 4, and FIG. 5 illustrates a database of gains of the current control circuit regarding normal imaging conditions. It is explanatory drawing demonstrated. Data is stored in which the gain of proportional gain KP, integral gain KI, and differential gain KD increases as the target current value from sequencer 12 increases.

  FIG. 6 is a database that stores the gains of the current control circuit 3228, the current control circuit 3248, and the current control circuit 3268 when the shooting condition is high-speed shooting, and the calculation unit 3302 exceeds the threshold for determining whether to perform high-speed shooting. The database shown in FIG. 6 is a search target. On the other hand, below the threshold value, the database shown in FIG. 5 is searched. In the database shown in FIG. 6, as the current value and current change amount of the target current value command from the sequencer 12 increase, the proportional gain KP, the integral gain KI, and the differential gain KD tend to increase. Further, for example, the proportional gain KP or the differential gain KD of the frequency axis is larger than the gain of the slice axis or the phase axis. Thus, by increasing the gain KP of the frequency axis, for example, or the gain KD of the differential, a more preferable control of the supply current is possible.

  FIG. 7 is a database showing the gain of the current control circuit when the current for generating the slice selection gradient magnetic field, which is the slice axis, shows the special current pattern shown in FIG. In this database, as the current value and current change amount of the target current value command from the sequencer 12 increase, the proportional gain KP, the integral gain KI, and the differential gain KD tend to increase. For example, the integral gain KI of the current control circuit that generates a current for selecting a slice is the gain of the current control circuit that generates the phase encoding current that is the phase axis or the frequency encoding current that is the frequency axis. Has a large value. This is more preferable control.

  FIG. 9 shows a special example of a current pattern supplied to a gradient magnetic field coil that generates a slice selection gradient magnetic field for slice selection. In this example, the target current of the current pattern supplied to the gradient magnetic field coil that generates the slice selection gradient magnetic field is not constant. For example, the target current is slightly smaller in the central time zone. In such a case, the steady-state deviation between the target current value of the target current value command, which is the current pattern, and the supply current supplied to the gradient magnetic field coil is less for the slice axis than for the phase axis current and the frequency axis current. In other words, it is desirable to achieve higher accuracy. For this reason, it is desirable to increase the gain KI corresponding to the integral of the slice axis. As a method different from this method, for example, if the value of the proportional gain KP is increased to improve the accuracy of the slice axis, the possibility of an oscillation phenomenon increases. As shown in FIG. 9, when the target current value of the current for slice selection is not constant and changes, it is desirable to increase the gain corresponding to the integral of the slice axis as shown in FIG. .

  Operations of the gain determination unit 3222, the gain determination unit 3242, and the gain determination unit 3262 illustrated in FIG. 3 will be described with reference to the flowchart illustrated in FIG. The operations of the gain determination unit 3222, the gain determination unit 3242, and the gain determination unit 3262 are substantially the same, and the gain determination unit 3222 will be described as a representative. In step S102, the target current value command 3202 from the sequencer 12 is received. In step S <b> 104, the gain determination unit 3222 uses the calculation unit 3302 to analyze the received target current value command 3202. For example, the change amount or the target current value of the target current value command 3202 is obtained by calculation by the calculation unit 3302.

  In step S106, the gain is calculated according to the calculated change amount or the target current value. Specifically, the gain is retrieved from the data storage unit 3304 as described above. The gain obtained in step S108 is input to the current control circuit 3228 and set. Although the X-axis gradient magnetic field power source 322 has been described, the same applies to the Y-axis gradient magnetic field power source 324 and the Z-axis gradient magnetic field power source 326. Steps S106 and S108 perform the same operation as the gain determination unit 3222, the gain determination unit 3242, and the gain determination unit 3262, and determine a gain suitable for each supply current to be supplied to the gradient coil to generate a gradient magnetic field. The gain determining unit operates to set the determined gains in the current control circuit.

  In the flowchart illustrated in FIG. 10, the target current value command 3202 received from the sequencer 12 is analyzed to determine the change amount or the target current value of the target current value command 3202. However, the change amount of the target current value command 3202 or the target current value may be transmitted as data from the sequencer 12 to the gain determination unit 3222. Thus, another embodiment of FIG. 10 is shown in FIG. In step S202 of FIG. 11, the sequencer 12 obtains a change amount or a target current value of the target current value command 3202 sent to the X-axis gradient magnetic field power source 322 based on the imaging conditions, and describes the obtained change amount or target current value in FIG. To the calculation unit 3302. The computing unit 3302 searches the data storage unit 3304 using the received change amount or target current value as a parameter, and sends the gain obtained by the search to the PID control circuit 3228 for setting. After the gain is set in the current control circuit 3228, a current pattern that is the target current value command 3202 is applied to the current control circuit 3228. In this case, since the target current value command 3202 is applied to the current control circuit 3228 after the gain setting is completed, the delay circuit 3226 is unnecessary.

  In this method, the operation delay by the gain determination unit 3222 can be reduced, and the gain determination time of the current control circuit 3228 can be shortened. Steps S206 and S208 operate as the gain determination unit 3222, the gain determination unit 3242, and the gain determination unit 3262, and determine and determine a gain suitable for each supply current supplied to the gradient coil to generate a gradient magnetic field. The gain determination unit operates to set the obtained gain in the current control circuit.

  FIG. 12 shows still another embodiment of the processing method described in FIG. 10 or FIG. 11, and is the method indicated by the broken line in FIG. Steps S302 and 304 are processes performed by the sequencer 12 or the CPU 14. In step S302, a current pattern supplied to the gradient coil is obtained by calculation based on the imaging conditions. Here, the concept of calculation includes not only four arithmetic operations but also processing for obtaining necessary data by searching a database. In step 304, a gain corresponding to the current pattern is obtained by calculation. The obtained gain may be transmitted and set from the sequencer 12 or the CPU 14 to the corresponding current control circuit as described in step S308.

  As yet another embodiment, even if the X-axis gradient magnetic field coil 342, the Y-axis gradient magnetic field coil 344, and the Z-axis gradient magnetic field coil 346 are mass-produced, each gradient magnetic field coil is the same X-axis gradient magnetic field coil 342. Even if it exists, a characteristic may differ a little or may change with time. In such a case, data for finely adjusting the gain may be held in the data storage unit 3304 illustrated in FIG. When fine adjustment data is held in this way, fine adjustment is performed in step S306, and the finely adjusted gain in step S308 is input to the corresponding current control circuit and set. The fine adjustment database used in step S306 may be stored anywhere, but may be stored in, for example, the gain determination unit of each gradient magnetic field power supply. By doing so, it becomes possible to set the gain with higher accuracy.

  In the embodiment shown in FIG. 12, the gain of the PID control circuit 3228 is determined in steps S304 and S306. The determined gain is input and set to the PID control circuit 3228 in step S308. Steps S304, S306, and S308 perform the same operations as the gain determination unit 3222, the gain determination unit 3242, and the gain determination unit 3262, and operate as a gain determination unit.

  The operations of the blocks shown in FIGS. 3 and 4 and the operations of the flowcharts shown in FIGS. 10 to 12 have been described specifically for the X-axis gradient magnetic field power supply 322, but the Y-axis gradient magnetic field power supply 324 and the Z-axis gradient magnetic field power supply are described. The same applies to 326. A gradient magnetic field coil for generating a slice selection gradient magnetic field, a phase encoding gradient magnetic field, and a frequency encoding gradient magnetic field is processed by the CPU 14 based on the imaging conditions, respectively, based on the imaging conditions. 344 and Z-axis gradient magnetic field coil 346. In a state where the allocation information is included in the imaging condition information, the current pattern information supplied from the CPU 14 to the sequencer 12 and supplied to each gradient magnetic field coil based on the imaging condition information is the target current value command 3202 or the target The current value command 3204 and the target current value command 3206 are sent from the sequencer 12 to the X-axis gradient magnetic field power supply 322 frequency encoding gradient magnetic field, current control circuit 3248, and current control circuit 3268.

  In this case, the current pattern as the target current value command for generating the slice selection gradient magnetic field, the phase encoding gradient magnetic field, and the frequency encoding gradient magnetic field sent from the sequencer 12 is the slice selection gradient magnetic field and the phase encoding respectively. In accordance with the above assignment of the gradient magnetic field and the frequency encoding gradient magnetic field, the corresponding X-axis gradient magnetic field coil 342, Y-axis gradient magnetic field coil 344, and Z-axis gradient magnetic field coil 346 are sent to the corresponding gradient magnetic field power supplies. Further, the gain determining unit for determining the gain for the current control circuit of each gradient magnetic field power source and the operations illustrated in FIGS. 10 to 12 include the slice axis, phase axis, and frequency axis of the items illustrated in FIGS. The axis current according to the above assignment among the parameters is selected as a parameter for searching the database.

  In each of the above-described embodiments, the gain of the current control circuit included in the gradient magnetic field power source that generates the supply current to be supplied to each gradient coil can be set with a value corresponding to the magnitude of the target value of the supply current. The supply current can be controlled with high accuracy. Furthermore, since the responsiveness of the current control circuit can be improved, it is possible to cope with high-speed shooting.

  Furthermore, since the database relating to gain shown in FIGS. 5, 6, and 7 is provided corresponding to the case of general shooting conditions, high-speed shooting, or special shooting, the characteristics of the current control circuit are used as shooting conditions. It is possible to achieve an adapted characteristic, and a high-quality image can be obtained.

  A gain database can be created and stored corresponding to each device, and the gain is adapted to the X-axis gradient magnetic field coil 342, Y-axis gradient magnetic field coil 344, and Z-axis gradient magnetic field coil 346 of each device. The control circuit 3228, the current control circuit 3248, and the current control circuit 3268 can be operated. As a result, the accuracy of the current supplied to the gradient coil can be further improved. It is possible to provide a fine adjustment database for adjustment of each device and change with time and finely adjust the gain based on the fine adjustment database as in step S306 described in FIG. As a result, the accuracy of the current supplied to the gradient coil can be further improved.

  11: subject, 12: sequencer, 14: CPU, 20: magnetic field generator, 22: static magnetic field generator, 30: gradient magnetic field generator, 32: gradient magnetic field power supply, 34: gradient magnetic field coil, 40: transmitter 42: high-frequency oscillator, 44: modulator, 46: high-frequency amplifier, 48: irradiation coil, 50: receiver, 52: receiver coil, 54: signal amplifier, 56: quadrature phase detector, 58: A / D converter, 60: processing unit, 61: external storage device, 62: optical disk, 64: magnetic disk, 66: internal memory, 80: bed, 90: input / output device, 91: input device, 92: pointing device, 94: keyboard, 96 : Output device, 98: display, 99: printer, 100: MRI device, 322: X axis gradient magnetic field power source, 324: Y axis gradient magnetic field power source, 326: Z axis gradient magnetic field power source, 342: X-axis gradient magnetic field coil, 344: Y-axis gradient magnetic field coil, 346: Z-axis gradient magnetic field coil, 3202: Target current value command, 3204: Target current value command, 3206: Target current value command, 3222: Gain determination unit, 3226 : Delay circuit, 3228: current control circuit, 3232: current amplifier, 3234: supply current, 3236: current detector, 3242: gain determination unit, 3246: delay circuit, 3248: current control circuit, 3252: current amplifier, 3254: Supply current, 3256: Current detector, 3262: Gain determination unit, 3266: Delay circuit, 3268: Current control circuit, 3272: Current amplifier, 3274: Supply current, 3276: Current detector, 3224: Gain command, 3244: Gain Command, 3264: gain command, 3302: calculation unit, 3304: data storage unit, 3306: command Search item, 3318: addition point, 3312: proportional circuit, 3314: integration circuit, 3316: differentiation circuit, 3308: item, 3310: current level.

Claims (10)

A static magnetic field generator that generates a static magnetic field in a measurement space that houses the subject;
A gradient magnetic field generator having a gradient magnetic field coil for generating a gradient magnetic field in the measurement space, and a gradient magnetic field power source for supplying a current to the gradient magnetic field coil;
An irradiation coil for generating a high-frequency magnetic field for irradiating the subject;
A receiving coil for receiving a nuclear magnetic resonance signal generated by the subject based on irradiation of the high-frequency magnetic field;
A display for displaying an image generated based on the received nuclear magnetic resonance signal;
A gain determining unit that determines gain of the gradient magnetic field power source and outputs gain information;
Have
Gain information output by the gain determination unit is input to the gradient magnetic field power supply, and the gradient magnetic field power supply operates with the determined gain to generate a current to be supplied to the gradient magnetic field coil.
A magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 1.
A storage device for storing a database relating to gain information using information relating to a supply current supplied to the gradient coil as a search parameter;
The database stored in the storage device is searched according to information on a supply current supplied to the gradient coil, and the gradient power supply generates a current to be supplied to the gradient coil according to gain information obtained by the search.
A magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 2.
The gradient magnetic field generation unit has an X-axis gradient magnetic field coil, a Y-axis gradient magnetic field coil, and a Z-axis gradient magnetic field coil as the gradient magnetic field coil,
The gradient magnetic field generator further includes, as the gradient magnetic field power supply, an X-axis gradient magnetic field power supply for supplying current to the X-axis gradient magnetic field coil, a Y-axis gradient magnetic field power supply for supplying current to the Y-axis gradient magnetic field coil, A Z-axis gradient magnetic field power source for supplying a current to the Z-axis gradient coil,
The database has, as search parameters, a slice axis item, a phase encode axis item, and a frequency encode axis item,
Gain to the gradient magnetic field power source allocated for slice selection among the X-axis gradient magnetic field power source, the Y-axis gradient magnetic field power source, or the Z-axis gradient magnetic field power source in accordance with the gain information retrieved based on the slice axis item Is set,
In accordance with the gain information retrieved based on the phase encoding axis item, the gradient magnetic field power source allocated for phase encoding among the X axis gradient magnetic field power source, the Y axis gradient magnetic field power source, and the Z axis gradient magnetic field power source. Gain is set,
In accordance with the gain information searched based on the frequency encode axis item, the gradient magnetic field power source allocated for frequency encoding among the X axis gradient magnetic field power source, the Y axis gradient magnetic field power source, or the Z axis gradient magnetic field power source. Gain is set,
A magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 3.
Each of the X-axis gradient magnetic field power source, the Y-axis gradient magnetic field power source, and the Z-axis gradient magnetic field power source includes a PID control circuit, and by searching the database, the proportional component, the integral component, and the gain of the derivative component are respectively retrieved The retrieved proportional, integral and differential gains are respectively input and set in the respective PID control circuits of the X-axis gradient magnetic field power source, the Y-axis gradient magnetic field power source and the Z-axis gradient magnetic field power source. ,
A magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 3.
The database for storing information related to the gain includes the amount of change in the target current value command supplied from the sequencer to each gradient magnetic field power supply in addition to the slice axis item, the phase encode axis item, and the frequency encode axis item, or The first change amount of the target current value command is searched for based on the magnitude of the target current value and the first change amount of the target current value command or the first gain searched according to the first target current value. Alternatively, the second gain that is searched according to the second change amount or the second target current value that is larger than the first target current value has a larger value.
A magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 3.
Control of the imaging sequence and the gradient magnetic field power source allocated for the slice selection according to the imaging sequence, the gradient magnetic field power source allocated for the phase encoding, and the gradient magnetic field power source allocated for the frequency encoding A sequencer that supplies each target current command is further provided.
In the first case in which the sequencer supplies a target current value command to the gradient magnetic field power source assigned for frequency encoding in the first imaging sequence, the sequencer performs a second imaging sequence that is faster than the first imaging sequence. In the second case where a target current value command is supplied to the gradient magnetic field power source allocated for frequency encoding in the above, the gradient magnetic field power source allocated for frequency encoding is compared with the first case. The gain of the derivative with a large value is set.
A magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 3.
Control of the imaging sequence and the gradient magnetic field power source allocated for the slice selection according to the imaging sequence, the gradient magnetic field power source allocated for the phase encoding, and the gradient magnetic field power source allocated for the frequency encoding A sequencer that supplies each target current command is further provided.
In the first case in which the sequencer supplies a target current value command to the gradient magnetic field power source assigned for frequency encoding in the first imaging sequence, the sequencer performs a second imaging sequence that is faster than the first imaging sequence. In the second case where a target current value command is supplied to the gradient magnetic field power source allocated for frequency encoding in the above, the gradient magnetic field power source allocated for frequency encoding is compared with the first case. A large proportional gain is set,
A magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 3.
Control of the imaging sequence and the gradient magnetic field power source allocated for the slice selection according to the imaging sequence, the gradient magnetic field power source allocated for the phase encoding, and the gradient magnetic field power source allocated for the frequency encoding A sequencer that supplies each target current command is further provided.
In the first case where the sequencer supplies a target current value command having a substantially constant maximum current value in the current pattern to the gradient magnetic field power supply allocated for the frequency encoding, the sequencer determines the maximum current in the current pattern. A target current value command is supplied to the gradient magnetic field power source allocated for the slice selection in a second imaging sequence in which a target current value command whose value changes is supplied to the gradient magnetic field power source allocated for the slice selection. In the second case, a gain corresponding to an integral value larger than that in the first case is set for the gradient magnetic field power source allocated for the slice selection.
A magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to any one of claims 1 to 8,
Each of the gradient magnetic field power supplies has a gain determination unit that determines the gain according to a current change amount or a target current value.
A magnetic resonance imaging apparatus. A static magnetic field generator that generates a static magnetic field in a measurement space that houses the subject;
A gradient magnetic field generator having a gradient coil and a gradient magnetic field power supply for generating a gradient magnetic field in the measurement space;
An irradiation coil for generating a high-frequency magnetic field for irradiating the subject;
A receiving coil for detecting a nuclear magnetic resonance signal generated by the subject based on irradiation of the high-frequency magnetic field;
A display for displaying an image generated based on the received nuclear magnetic resonance signal;
A gain determination unit;
In a method for controlling a magnetic resonance imaging apparatus having:
A gain determining step for determining a gain of the gradient magnetic field power source based on set imaging conditions;
A gain setting step for setting the gain determined in the gain determination step in the gradient magnetic field power supply;
The gradient magnetic field generated in the measurement space is superimposed on the static magnetic field by supplying a current based on the set imaging condition from the gradient magnetic field power source set by the gain setting step to the gradient magnetic field coil. Irradiating a high-frequency magnetic field from the irradiation coil to perform imaging;
A method for controlling a magnetic resonance imaging apparatus, comprising:

Images