WO2016186011A1 - Magnetic resonance imaging device - Google Patents

Abstract

A noise transfer function with respect to a current applied to a gradient magnetic field coil 3 is acquired in advance, and by utilizing said transfer function to adjust the current applied to the gradient magnetic field coil 3, the noise emitted by the MRI device 1 according to the present invention during measurement is suppressed, thereby alleviating the load on a subject.

Description

Magnetic resonance imaging system

The present invention relates to a magnetic resonance imaging apparatus using nuclear magnetic resonance.

A magnetic resonance imaging apparatus (hereinafter referred to as an MRI (Magnetic Resonance Imaging) apparatus) uses a nuclear magnetic resonance phenomenon of a nucleus to generate a magnetic resonance image representing the physical properties of an object placed in an imaging space. It is a device to obtain. In general, an MRI apparatus includes a static magnetic field generating means for generating a uniform static magnetic field in an imaging space, an irradiation coil for irradiating a high-frequency electromagnetic wave for generating nuclear magnetic resonance in a nucleus of a living tissue of a subject, A receiving coil for receiving a nuclear magnetic resonance signal and a gradient magnetic field coil for generating a linear gradient magnetic field superimposed on a static magnetic field in order to give position information to the nuclear magnetic resonance signal are provided.

At the time of imaging, a linear gradient magnetic field is superimposed on the subject placed in a uniform static magnetic field in the x, y, and z axis directions according to a desired pulse sequence, and the atomic spin of the subject is magnetized at a resonance frequency called Larmor frequency. Excited. With this excitation, a nuclear magnetic resonance signal is detected, and a magnetic resonance image (for example, a two-dimensional tomographic image) of the subject is taken.

Thus, at the time of photographing, in order to create a linear gradient magnetic field, a pulsed current is passed through the gradient coil disposed in the static magnetic field. At this time, the Lorentz force acts on the gradient magnetic field coil by the static magnetic field and the current flowing through the gradient magnetic field coil, and the gradient magnetic field coil vibrates. Due to the vibration of the gradient magnetic field coil, the air around the gradient magnetic field coil vibrates and generates noise. Further, the vibration of the gradient magnetic field coil propagates to the static magnetic field generating means via the support member, the static magnetic field generating means vibrates, the air around the static magnetic field generating means vibrates, and noise is generated.

As described above, the noise of the MRI apparatus is a sound radiated due to the vibration generated by the current applied to the gradient coil. Patent Document 1 is disclosed as a technique for reducing noise with respect to the current applied to the gradient coil.

Patent Document 1 (Japanese Patent Laid-Open No. 2006-334050) discloses a magnetic resonance imaging apparatus comprising means for reducing noise by lowering the peak of the waveform of the current applied to the gradient coil. Yes.

JP 2006-334050 A

However, the noise of the MRI apparatus may change the characteristics of the current applied to the gradient magnetic field coil due to the change of the imaging parameters performed to obtain a desired image. At this time, since the Lorentz force generated in the gradient magnetic field coil changes, the magnitude and frequency characteristics of the noise generated by soot may change. For example, when the noise increases, the physical and mental burden on the subject increases. Accordingly, an object of the present invention is to provide a magnetic resonance imaging apparatus (MRI apparatus) that suppresses an increase in noise due to a change in imaging parameters.

In order to solve such a problem, a magnetic resonance imaging apparatus according to the present invention includes a static magnetic field generation means, a gradient magnetic field generation means, a nuclear magnetic resonance signal acquisition means,
A noise transfer function is obtained by applying a single frequency current or a frequency swept current to the gradient magnetic field generating means, and the noise transfer function is applied to the gradient magnetic field generating means. It is used for adjusting the applied current.

According to the present invention, it is possible to provide a magnetic resonance imaging apparatus (MRI apparatus) that can suppress an increase in noise due to a change in imaging parameters.

It is a schematic block diagram which shows the whole structure of the MRI apparatus which concerns on 1st Embodiment. It is a processing flow of the MRI apparatus which concerns on 1st Embodiment. It is a schematic block diagram for acquiring the noise transfer function of the MRI apparatus according to the present invention. It is the schematic of the noise transfer function of the MRI apparatus which concerns on this invention. It is the schematic of the frequency characteristic of the electric current applied to the gradient magnetic field coil of the MRI apparatus which concerns on this invention. It is the figure which showed the value of the noise transfer function in the frequency when the electric current applied to a gradient magnetic field coil becomes the maximum in the MRI apparatus which concerns on this invention. It is the figure which showed on the noise transfer function the range which can take the frequency when the electric current applied to the gradient magnetic field coil of the MRI apparatus which concerns on 1st Embodiment becomes the maximum. It is a processing flow of the MRI apparatus which concerns on 2nd Embodiment. FIG. 8A is a diagram showing a range of possible frequency when the current applied to the gradient coil of the MRI apparatus according to the second embodiment is maximized on a noise transfer function. FIG. The frequency range that satisfies (2), (b) is the frequency range that satisfies Equation (3), and (c) is the frequency range that satisfies both Equation (2) and Equation (3). It is a processing flow of the MRI apparatus which concerns on 3rd Embodiment. The figure which showed on the noise transfer function the range which can take the frequency when the electric current applied to the gradient magnetic field coil of the MRI apparatus which concerns on 3rd Embodiment becomes the maximum, (a) is the value Ln of a transfer function. A frequency range that satisfies (2), (b) is a frequency range that satisfies Equation (4), and (c) is a frequency range that satisfies both Equation (2) and Equation (4). It is a processing flow of the MRI apparatus which concerns on 4th Embodiment. The figure which showed on the noise transfer function the range which can take the frequency when the electric current applied to the gradient magnetic field coil of the MRI apparatus concerning 4th Embodiment becomes the maximum, (a) is a value Ln of a transfer function. The frequency range that satisfies (5), (b) is the frequency range that satisfies Equation (3), and (c) is the frequency range that satisfies both Equation (5) and Equation (3). It is a processing flow of the MRI apparatus which concerns on 5th Embodiment. FIG. 9A is a diagram showing a range that can be taken by a frequency when the current applied to the gradient magnetic field coil of the MRI apparatus according to the fifth embodiment is maximum on the noise transfer function, and FIG. The frequency range that satisfies (5), (b) is the frequency range that satisfies Equation (4), and (c) is the frequency range that satisfies both Equation (5) and Equation (4). It is a schematic block diagram which shows the whole structure of an MRI apparatus. It is a processing flow of the MRI apparatus which concerns on 6th Embodiment. It is the schematic of the frequency characteristic of the electric current applied to the gradient magnetic field coil of the MRI apparatus which concerns on 6th Embodiment. It is the figure which showed on the noise transfer function the range which can take the frequency when the electric current applied to the gradient magnetic field coil of the MRI apparatus which concerns on 6th Embodiment becomes the maximum. It is a processing flow of the MRI apparatus which concerns on 7th Embodiment. It is a schematic block diagram of the control apparatus with which the MRI apparatus of a present Example is provided.

(First embodiment)
Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

First, an overall outline of the MRI apparatus according to the first embodiment will be described with reference to FIG. FIG. 16 is a schematic block diagram showing the overall configuration of the MRI apparatus. The MRI apparatus can obtain a magnetic resonance image (for example, a two-dimensional tomographic image) of a subject using a nuclear magnetic resonance phenomenon.

As shown in FIG. 16, the MRI apparatus 1 includes a static magnetic field generating means 2 (magnet 2) that generates a uniform static magnetic field in the imaging space 100, and a static magnetic field superimposed on the magnetic magnetic resonance signal to give positional information. A gradient magnetic field coil 3 for generating a linear gradient magnetic field, an irradiation coil 4 for irradiating high-frequency electromagnetic waves for generating nuclear magnetic resonance in the nucleus of the living tissue of the subject 200, and a computer 10 for controlling the entire MRI apparatus 1 (Control device 10), a sequencer 11 for receiving an imaging signal from the computer 10, a gradient magnetic field power source 12 for applying a current to the gradient magnetic field coil 3, and a nuclear magnetic resonance signal transmitted from the subject 200 Receiving coil 7, signal processing unit 13, and image reconstruction apparatus (computer 10) that obtains a magnetic resonance image from information subjected to signal processing based on the nuclear magnetic resonance signal It is configured to include a and. In FIG. 16, a processing system for sending a predetermined signal to the irradiation coil 4 is omitted.

Further, the static magnetic field generating means 2, the gradient magnetic field coil 3, and the irradiation coil 4 are covered with a cover 5 from the viewpoint of design and safety. Furthermore, the MRI apparatus 1 is often disposed in the shield room 300 in order to block high-frequency noise generated by the external environment and the apparatus itself. This room may be a room that does not have any problem in normal operation of the MRI apparatus 1, but here is a shield room 300 as an example.

The static magnetic field generating means 2 generates a uniform static magnetic field in the direction perpendicular to the body axis in the space around the subject 200 if the vertical magnetic field method is used. On the other hand, in the horizontal magnetic field method, a uniform static magnetic field is generated in the body axis direction. As the static magnetic field generation means 2, a permanent magnet type, a normal conducting magnet type, or a superconducting magnet type static magnetic field generating source can be adopted.

Next, the flow of imaging a tomographic image (magnetic resonance image) of the subject 200 by the MRI apparatus 1 will be described. First, a uniform static magnetic field is generated in the imaging space 100 by the static magnetic field generating means 2, and the subject 200 placed on the bed 6 is inserted into the imaging space 100.

The user (not shown) uses the trackball or mouse (not shown), the touch panel or keyboard (not shown), the display (not shown), and the like provided in the computer 10 to the subject 200. Manipulates the commands necessary to acquire the tomographic image. The command operated here is sent to the sequencer 11, and the sequencer 11 sends a signal for driving the gradient magnetic field power source 12 to the gradient magnetic field power source 12 in accordance with various commands necessary for collecting tomographic image data of the subject 200.

The gradient magnetic field power supply 12 applies a current to the gradient magnetic field coil 3 and superimposes a linear gradient magnetic field in the x, y, and z axis directions on the subject 200 placed in a uniform static magnetic field. Further, a high frequency signal is irradiated from the irradiation coil 4 to the subject 200, and the atomic spin of the subject 200 is magnetically excited at a resonance frequency called Larmor frequency.

Along with this excitation, a nuclear magnetic resonance signal generated is detected by the receiving coil 7, processed by the signal processing unit 13, and then the image is reconstructed by the computer 10 which is an image reconstructing device, thereby allowing an object in an arbitrary cross section to be analyzed. 200 tomographic images (magnetic resonance images) can be obtained. Further, the computer 10 includes a magnetic disk (not shown) of an external recording device, and can record a tomographic image of the subject 200 obtained by the above processing.

Next, details of the MRI apparatus according to the first embodiment will be described with reference to FIG. FIG. 1 is a schematic block diagram showing the overall configuration of the MRI apparatus according to the first embodiment including the characteristic configuration of the present embodiment. As shown in FIG. 1, in the MRI apparatus 1 of this embodiment, a control device 40 is interposed between a computer 10 and a sequencer 11. For the sake of explanation, the control device 40 is shown separately from the computer 10 in FIG. 1, but the functions of the control device 40 may be incorporated in the computer 10 or realized by another server connected by a network. May be.

The MRI apparatus 1 is installed in the shield room 300. After installation, before the MRI apparatus 1 is operated, an installation period is provided to adjust the apparatus and adjust the magnetic field. Within this installation period, the noise transfer function 90 for the applied current to the gradient coil 3 is acquired. FIG. 2 is a processing flow of the MRI apparatus according to the first embodiment including acquisition of the noise transfer function 90, which is executed in the control apparatus 40. In addition, about each function which the control apparatus 40 has, it has shown as a functional block diagram in FIG.

Hereinafter, each process executed by the control device 40 will be sequentially described.

<Acquisition of noise transfer function (S001)>
First, acquisition of the noise transfer function 90 (S001) will be described with reference to FIG. FIG. 3 is a schematic block diagram for obtaining the noise transfer function 90 of the MRI apparatus 1 according to the present embodiment. As shown in FIG. 3, regarding the acquisition of the noise transfer function, it may be acquired in advance using another computer or the like without being executed by the control device 40, or the control described above for the analyzer 53 may be performed. It may be incorporated in the device 40.

The noise transfer function 90 applies a single-frequency current or a frequency-swept current to the gradient coil 3 using the voltage / current generator 51 in the shield room 300 where the MRI apparatus 1 is installed. To do. The noise generated at this time is acquired by the microphone 50 installed at a predetermined position, and the acquired signal is amplified by the amplifier 52 and analyzed by the analyzer 53. The analyzer 53 receives and analyzes the signal from the voltage / current generator 51 and the signal from the amplifier 52, and calculates the noise transfer function 90 by the equation (1).
H = A ÷ I (1)
here,
H: Noise transfer function 90
A: Sound pressure acquired by the microphone 50 I: current applied to the gradient magnetic field coil 3. FIG. 4 is an example of the calculated noise transfer function 90.

Since the current applied to the gradient coil 3 has three axes, x, y, and z, there are three noise transfer functions 90 calculated by equation (1). These are denoted as Hx, Hy, Hz.

The position of the microphone 50 for acquiring the noise transfer function 90 will be described. The position of the microphone 50 is the center of the imaging space 100 in which the subject 200 that receives noise is inserted or the periphery thereof. The peripheral here refers to a position where the noise of the MRI apparatus 1 is larger than that of the imaging space 100 and other positions, for example. In order to determine the position where the noise is high, it is necessary to measure the noise in advance or to know it empirically. In addition, you may install in a suitable position as needed.

The noise measured by the microphone 50 is affected by the shield room 300. Specific parts of the shield room 300 that affect noise include wall surface materials (including floor surfaces), finishing materials, room volume, room temperature, and the like. In addition, it is influenced by the installation method of the MRI apparatus 1. These are unknown elements at the time of manufacturing the MRI apparatus 1 (at the time of shipment from the manufacturing factory), and noise is somewhat different depending on the installation location even in the same apparatus. Therefore, the acquisition of the noise transfer function 90 is performed at an installation site such as the shield room 300 where the MRI apparatus 1 is installed. Alternatively, the noise transfer function 90 may be acquired when the MRI apparatus 1 is manufactured (at the time of shipment from a manufacturing factory). The noise transfer function 90 acquired at this time can be used for inspection at the time of shipment from a manufacturing factory. In addition, the noise transfer function 90 acquired at the time of shipment from the manufacturing factory is less accurate than the noise transfer function 90 acquired at the installation site because the room environment (wall material, room volume, etc.) is different. It can also be used on site. However, in order to use the highly accurate noise transfer function 90, it is necessary to obtain the noise transfer function 90 at the installation site.

The acquired noise transfer function 90 is recorded in the determination unit 33.

Note that the noise transfer function 90 is not necessarily acquired only during the installation period of the MRI apparatus 1, but may be acquired during maintenance of the MRI apparatus 1. The acquisition method is the same as described above. Further, the noise transfer function 90 used so far can be updated with the noise transfer function 90 acquired during the maintenance. By this update, it is possible to calibrate the noise transfer function 90 that changes with the aging or maintenance of the MRI apparatus 1 or the shield room 300.

<Imaging Parameter Control Unit 30>
Next, the imaging parameter control unit 30 will be described. The imaging parameter control unit 30 controls parameters set by the user using an input device connected to or integrally provided with the computer 10 (S002). There are about 100 types of parameters set by the user, such as an imaging field of view, slice thickness, number of integrations, number of slice encodes, number of frequency encodes, number of phase encodes, and the like. Some parameters are dependent on each other and their settings are limited.

For this reason, complicated processing is required to set parameters. In a general MRI apparatus, parameters are set in advance, and the user uses the preset parameters as they are or changes some parameters in order to obtain a desired image.

When changing the parameters, the imaging parameter control unit 30 determines whether or not imaging is possible with the set parameters. If it is determined that the imaging is not possible, the imaging parameter control unit 30 notifies that fact, or changes the upper limit or lower limit of a predetermined parameter. Present the value or automatically calculate the optimal parameter and present it to the user. These are presented on a display or the like through the computer 10.

<Current waveform calculation unit 31>
Next, the process of the current waveform calculation unit 31 will be described. The current waveform calculation unit 31 calculates a current waveform to be applied to the gradient magnetic field coil 3 based on the parameters specified by the imaging parameter control unit 30 (S003). The calculated current waveform is a current waveform applied to three axes of the gradient magnetic field coil 3 including the x, y, and z axes. The calculated current waveform is transmitted to the frequency analysis unit 32.

<Frequency analysis unit 32>
Next, processing of the frequency analysis unit 32 will be described. The frequency analysis unit 32 performs frequency characteristic analysis of the current waveform received from the current waveform calculation unit 31. Further, the frequency Fn having the largest current value is calculated from the frequency characteristics of the analyzed current waveform (in other words, the frequency Fn having the largest current value among a plurality of frequency components constituting the current waveform is calculated). (S004).

FIG. 5 is an example of the frequency characteristics of the current waveform analyzed by the frequency analysis unit 32 and the frequency Fn. As described above, since there are three current waveforms on the x, y, and z axes, three frequency characteristics of the current are also analyzed. Therefore, three frequencies Fn are also calculated. These are frequencies Fnx, Fny, and Fnz. These three frequencies are transmitted to the determination unit 33.

<Determining unit 33>
Next, the determination unit 33 will be described. The determination unit 33 performs a predetermined determination using the three frequencies Fnx, Fny, and Fnz received from the frequency analysis unit 32 and the noise transfer function 90 recorded in advance.

First, the frequency characteristics of the current waveform based on the preset imaging parameters and the frequencies F0x, F0y, and F0z having the largest current values from the frequency characteristics are recorded in the determination unit 33 as data in advance. Further, values L0x, L0y, and L0z of the noise transfer function 90 (Hx, Hy, Hz) corresponding to the frequencies F0x, F0y, and F0z are calculated.

This preset imaging parameter (first imaging parameter), current waveform corresponding thereto, frequency F0x, F0y, F0z obtained by the frequency analysis, and noise transfer function 90 corresponding to the frequencies F0x, F0y, F0z ( A data set including values L0x, L0y, L0z, etc. of Hx, Hy, Hz) is referred to as a first data set. The first data set may be imaging parameters frequently used by an operator, imaging parameters recommended by clinical guidelines, and the like. In addition, the user may newly acquire and register imaging parameters suitable for his / her operation status.

Next, values Lnx, Lny, Lnz of the noise transfer function 90 (Hx, Hy, Hz) corresponding to the frequencies Fnx, Fny, Fnz are calculated (S005). An imaging parameter (second imaging parameter) input to the imaging parameter control unit 30, a current waveform corresponding to the imaging parameter, a noise transfer function 90 (Hx, Hy corresponding to the frequencies Fnx, Fny, and Fnz obtained by the frequency analysis) , Hz) data set including values Lnx, Lny, Lnz, etc. is called a second data set.

Then, the determination unit 33 compares the first data set and the second data set. Specifically, the calculated values L0x and Lnx, L0y and Lny, and L0z and Lnz are compared and determined (S006). Hereinafter, in order to simplify the notation, the subscripts x, y, and z are omitted. The determination is whether or not the value Ln satisfies Expression (2).
Ln ≦ L0 (2)
FIG. 7 is a diagram showing a range that can be taken by the frequency Fn of the value Ln that satisfies Expression (2). FIG. 7 shows the intersection between the noise transfer function 90 and L0 as fi (i = 1, 2,...) (Excluding the intersection with the frequency F0). When the value Ln satisfies Expression (2), that is, when the frequency Fn is within the range indicated by the arrow in FIG. 7, the value in the gradient magnetic field coil 3 is smaller than that before the parameter change in the imaging parameter control unit 30. Since the noise transfer function 90 for the applied current to the same axis as the axis is the same or smaller, the noise magnitude is the same or smaller.

When the value Ln satisfies the expression (2), that is, when the first data set is used as a reference and the second data set is appropriate, the information on the imaging parameter is sent to the sequencer 11. The sequencer 11 sends a signal for driving the gradient magnetic field power source 12 to the gradient magnetic field power source 12 in accordance with various commands necessary for collecting data of tomographic images of the subject 200, and takes a tomographic image of the subject 200 (S008). .

On the other hand, when the value Ln does not satisfy Expression (2), that is, when the first data set is used as a reference and the second data set is inappropriate, for example, the frequency Fn is as shown in FIG. If it exists outside the range indicated by the arrow, the information is transmitted to the imageable condition calculation unit 34.

It should be noted that there are three judgment targets of Expression (2): L0x and Lnx, L0y and Lny, and L0z and Lnz. The determination criterion satisfying the expression (2) may be any one of these three, or two, or all three. Alternatively, the determination may be made by comparing the combined value of Lnx, Lny, and Lnz with the combined value of L0x, L0y, and L0z. The user can select which condition is used for determination.

<Imagable condition calculation unit 34>
When the image capturing condition calculation unit 34 determines that the second data set is inappropriate when the first data set in the determination unit 33 is used as a reference, the imaging parameter condition set by the user, that is, the second data set is determined. Imaging parameters that are similar to the data set and satisfy Expression (2) are calculated, and the information is transmitted to the imaging parameter control unit 30 and presented to the user (S007). When the second data set is inappropriate, the newly calculated imaging parameter (third imaging parameter) and information including the current waveform and frequency component corresponding to the imaging parameter are referred to as a third data set. The user selects a parameter that satisfies Equation (2) based on the presented information. Since the selected parameter satisfies Expression (2), imaging is possible (S008).

It should be noted that the value Fn is a frequency having the maximum current value among the frequency components constituting the current in the current applied from the gradient magnetic field power supply 12 to the gradient coil 3.

Therefore, the MRI apparatus 1 of the present embodiment has a noise transfer function 90 indicating the relationship between the current applied to the gradient coil 3 and the noise generated by the Lorentz force generated between the current and the static magnetic field generating means 2. Based on the above, the validity of the value Fn included in the second data set is verified, and if it is not valid, a new Fn included in the third data set is searched and set for the gradient power supply 12 In other words, it can be said that the current applied by the gradient magnetic field power supply 12 (more specifically, the frequency component and consequently the current waveform) is applied after being adjusted based on the noise transfer function 90.

Note that the functional blocks described above are for convenience of explanation and may be realized as a single functional block.

In the above example, when the second data set is appropriate, no new imaging parameter is calculated, and information on this imaging parameter is sent to the sequencer 11 and a tomographic image of the subject 200 is captured. However, for example, a “silent mode” or the like is provided, and when this mode is executed, the second data set is quieter regardless of whether the second data set is appropriate, and A third data set similar to the content for which the imaging parameter is designated may be retrieved and presented.

Further, the third data set described in the above example may be stored and recorded each time it is newly acquired. By doing this, it is possible to obtain the third data set immediately by searching the history of imaging parameters input in the past, and the convenience of the operator can be improved.

Further, a plurality of the first data sets described in the above example may be acquired in advance. By acquiring the first data set relating to some typical imaging parameters, the imaging condition calculation unit 34 acquires the third data set even when the imaging parameters are greatly different. The possibility of being able to be improved and convenience can be improved.

<Action and effect>
The MRI apparatus 1 or the MRI imaging system described in the present embodiment controls the imaging parameters based on the noise transfer function 90 acquired in the shield room 300 where the MRI apparatus 1 is installed and the imaging parameters specified by the user. Present new information to the user.

The presented imaging parameter is an imaging parameter that satisfies an imaging condition capable of maintaining or reducing the magnitude of noise, and the magnitude of noise received by the subject 200 is maintained or captured by imaging using this imaging parameter. The burden on the subject 200 can be reduced.

Note that the user can set the imaging parameters not only from the viewpoint of noise but also from the viewpoint of images. The computer 10 displays the S / N, contrast, and the like of the image when the image is captured using the imaging parameters received from the image capturing condition calculation unit 34. The user can use this image information as one of the imaging parameter setting support for obtaining a desired image.

(Second Embodiment)
In the present embodiment, description of portions common to the first embodiment described above is omitted. A specific difference is the content of the determination formula calculated by the determination unit 33, in other words, the content compared between the first data set and the second data set. The determination formula will be described below. FIG. 8 is a processing flow of the MRI apparatus 1 according to the second embodiment including acquisition of the noise transfer function 90.

In the present embodiment, the determination unit 33 calculates a value Ln of the noise transfer function 90 corresponding to the frequency Fn and a value L0 of the noise transfer function 90 corresponding to the frequency F0. These values Ln and L0 are compared to determine whether or not the value Ln satisfies Expression (2) (S006).
Ln ≦ L0 (2)
FIG. 9A is a diagram illustrating a range that can be taken by the frequency Fn of the value Ln satisfying the expression (2). If the value Ln satisfies Expression (2), is the noise transfer function 90 for the applied current to the same axis as the axis in the gradient magnetic field coil 3 the same as before the imaging parameter change in the imaging parameter control unit 30? Since it is smaller, the noise is the same or less. When the value Ln satisfies Expression (2), the following determination is performed.

In the next determination, the frequency Fn is compared with the frequency F0, and it is determined whether the frequency Fn satisfies the expression (3) (S101).
Fn ≧ F0 (3)
FIG. 9B is a diagram showing a possible range of the frequency Fn that satisfies the expression (3). When the frequency Fn satisfies Expression (3), the strength of the gradient magnetic field is improved, so that the S / N, contrast, and the like of the image are improved, and the user can easily obtain a desired image.

FIG. 9C is a diagram showing a possible range of the frequency Fn that satisfies both the expressions (2) and (3). When the frequency Fn satisfies both the expressions (2) and (3), it is determined that imaging can be performed with the imaging parameter (second imaging parameter) set by the imaging parameter control unit 30. When it is determined that imaging is possible, information on the imaging parameters is sent to the sequencer 11, and the sequencer 11 generates various commands necessary for data acquisition of tomographic images of the subject 200 and drives the gradient magnetic field power supply 12. Is sent to the gradient magnetic field power supply 12 to capture a tomographic image of the subject 200.

On the other hand, when the value Ln does not satisfy Expression (2), or when Expression (2) is satisfied but Expression (3) is not satisfied, the information is transmitted to the image pickup condition calculation unit 34.

The imaging condition calculation unit 34 calculates an imaging parameter (third parameter) that is close to the parameter setting specified by the user with the imaging parameter control unit 30 and satisfies the equation (2), or the equation (2) and the equation Imaging parameters satisfying both (3) are calculated, and the information is transmitted to the imaging parameter control unit 30 and presented to the user. Based on the presented information, the user selects an imaging parameter that satisfies Expression (2) or satisfies both Expression (2) and Expression (3). Since the selected imaging parameter satisfies both Expression (2) and Expression (3), imaging is possible.

By controlling the imaging parameters in this way, the magnitude of the noise that changes with the change of the imaging parameters is maintained or reduced, and the burden on the subject 200 can be reduced. Further, the image desired by the user can be acquired by maintaining or improving the image quality.

(Third embodiment)
In the present embodiment, description of portions common to the first embodiment described above is omitted. The difference is a determination formula calculated by the determination unit 33. The determination formula will be described below. FIG. 10 is a process flow of the MRI apparatus according to the third embodiment including acquisition of the noise transfer function 90.

In the present embodiment, the determination unit 33 calculates a value Ln of the noise transfer function 90 corresponding to the frequency Fn and a value L0 of the noise transfer function 90 corresponding to the frequency F0. These values Ln and L0 are compared to determine whether or not the value Ln satisfies Expression (2) (S006).
Ln ≦ L0 (2)
FIG. 11A is a diagram illustrating a range that can be taken by the frequency Fn of the value Ln satisfying the expression (2). When the value Ln satisfies the formula (2), the noise transfer function 90 for the applied current to the same axis as the axis in the gradient magnetic field coil 3 is the same as that before the parameter change in the imaging parameter control unit 30 or not. Because it is smaller, the noise level is the same or smaller. When the value Ln satisfies Expression (2), the following determination is performed.

In the next determination, the frequency Fn is compared with the frequency F0, and it is determined whether the frequency Fn satisfies Expression (4) (S201).
Fn ≧ F0−ΔF (4)
Here, ΔF> 0. This ΔF is one of parameters that can be set in the computer 10. FIG.11 (b) is the figure which showed the range which the frequency Fn which satisfy | fills Formula (4) can take. Equation (4) means that it can take a value smaller by ΔF than Equation (2). This is because the value Ln of the noise transfer function 90 is larger than L0 when the frequency Fn satisfies Expression (2), but the value Ln is compared with L0 when the frequency Fn satisfies Expression (4). In order to apply a case where there is a condition for decreasing, the possible range of the frequency Fn is expanded.

That is, it becomes easier to acquire a desired image by expanding the settable range of the imaging parameter. When the frequency Fn is smaller than the frequency F0 (Fn <F0), the strength of the gradient magnetic field is lowered, so that the S / N and contrast of the captured image are lowered, and the image quality is lowered. Therefore, it is desirable that ΔF be as small as possible (a value close to 0). That is, the determination of Expression (4) is a determination expression that places importance on the maintenance or reduction of the noise level.

FIG. 11C is a diagram showing a possible range of the frequency Fn that satisfies both the expressions (2) and (4). When the frequency Fn satisfies both the expressions (2) and (4), it is determined that imaging can be performed with the imaging parameter (second imaging parameter) set by the imaging parameter control unit 30. When it is determined that imaging is possible, information on the imaging parameters is sent to the sequencer 11, and the sequencer 11 generates various commands necessary for data acquisition of tomographic images of the subject 200 and drives the gradient magnetic field power supply 12. Is sent to the gradient magnetic field power supply 12 to capture a tomographic image of the subject 200.

On the other hand, when the value Ln does not satisfy Expression (2), or when Expression (2) is satisfied but Expression (4) is not satisfied, the information is transmitted to the image capturing condition calculation unit 34.

The imaging possible condition calculation unit 34 calculates an imaging parameter (third imaging parameter) that is close to the imaging parameter condition specified by the user with the imaging parameter control unit 30 and satisfies Expression (2), or Expression (2). And the imaging parameter satisfying both of the expressions (4) are calculated, and the information is transmitted to the imaging parameter control unit 30 and presented to the user. Based on the presented information, the user selects an imaging parameter that satisfies Expression (2) or that satisfies both Expression (2) and Expression (4). Since the selected imaging parameter satisfies both Equation (2) and Equation (4), imaging is possible.

By controlling the imaging parameters in this way, the magnitude of the noise that changes with the change of the imaging parameters is maintained or reduced, and the burden on the subject 200 can be reduced. Further, by maintaining or improving the image quality as much as possible, an image desired by the user can be acquired.

(Fourth embodiment)
In the present embodiment, description of portions common to the first embodiment described above is omitted. A specific difference is a determination formula calculated by the determination unit 33. The details of this determination will be described below. FIG. 12 is a processing flow of the MRI apparatus according to the fourth embodiment including acquisition of the noise transfer function 90.

In the present embodiment, the determination unit 33 calculates a value Ln of the noise transfer function 90 corresponding to the frequency Fn and a value L0 of the noise transfer function 90 corresponding to the frequency F0. These values Ln and L0 are compared to determine whether or not the value Ln satisfies Expression (5) (S301).
Ln ≦ L0 + ΔL (5)
Here, ΔL> 0.

This ΔL is one of imaging parameters that can be set in the computer 10. FIG. 13A is a diagram showing a possible range of the frequency Fn of the value Ln satisfying the equation (5). Equation (5) means that it can take a value larger by ΔL than Equation (2). This is because the value Ln of the noise transfer function 90 is smaller than L0 in the case of the frequency Fn that takes the value Ln that satisfies the equation (2), but the frequency Fn is the frequency in the case of the frequency Fn that satisfies the equation (5). In order to apply a case where there is a condition that becomes larger than F0, the range that the frequency Fn can take is expanded. That is, it becomes easier to acquire a desired image by expanding the settable range of the imaging parameter.

When the value Ln becomes larger than the value L0 (Ln> L0), the noise increases. Therefore, it is desirable that ΔL be as small as possible (a value close to 0). That is, the determination of Expression (5) is a determination expression that places importance on maintaining or improving image quality.
When the value Ln satisfies Expression (5), the following determination is performed.

In the next determination, the frequency Fn is compared with the frequency F0, and it is determined whether the frequency Fn satisfies the expression (3) (S101).
Fn ≧ F0 (3)
FIG. 13B is a diagram showing a possible range of the frequency Fn satisfying the expression (3). When the frequency Fn satisfies Expression (3), the strength of the gradient magnetic field increases, so that the S / N, contrast, and the like of the image are improved, and the user can easily obtain a desired image.

FIG. 13 (c) is a diagram showing a possible range of the frequency Fn that satisfies both the expressions (5) and (3). When the frequency Fn satisfies both the expressions (5) and (3), it is determined that the imaging can be performed with the imaging parameter (second imaging parameter) set by the imaging parameter control unit 30. When it is determined that imaging is possible, information on the imaging parameters is sent to the sequencer 11, and the sequencer 11 generates various commands necessary for data acquisition of tomographic images of the subject 200 and drives the gradient magnetic field power supply 12. Is sent to the gradient magnetic field power supply 12 to capture a tomographic image of the subject 200.

On the other hand, when the value Ln does not satisfy Expression (5), or when Expression (5) is satisfied but Expression (3) is not satisfied, the information is transmitted to the image pickup condition calculation unit 34.

The imaging possible condition calculation unit 34 calculates an imaging parameter (third imaging parameter) that is close to the imaging parameter condition specified by the user with the imaging parameter control unit 30 and satisfies Expression (5), or Expression (5). The parameters satisfying both of the above and expression (3) are calculated, and the information is transmitted to the imaging parameter control unit 30 and presented to the user. Based on the presented information, the user selects an imaging parameter that satisfies Expression (5) or satisfies both Expression (5) and Expression (3). Since the selected parameter satisfies both Expression (5) and Expression (3), imaging is possible.

By controlling the imaging parameters in this way, the magnitude of the noise that changes as the imaging parameters are changed is maintained or reduced as much as possible, and the increase in the burden on the subject 200 can be suppressed or reduced. Further, by maintaining or improving the image quality, it is possible to perform imaging desired by the user.

(Fifth embodiment)
In the present embodiment, description of portions common to the first embodiment described above is omitted. A specific difference is a determination formula calculated by the determination unit 33. The details of this determination will be described below. FIG. 14 is a process flow of the MRI apparatus according to the fifth embodiment including acquisition of the noise transfer function 90.

In the present embodiment, the determination unit 33 calculates the value Ln of the noise transfer function 90 corresponding to the frequency Fn and the value L0 of the noise transfer function 90 corresponding to the frequency F0 (S005). These values Ln and L0 are compared to determine whether or not the value Ln satisfies Expression (5) (S301).
Ln ≦ L0 + ΔL (5)
Here, ΔL> 0.

This ΔL is one of the parameters that can be set in the computer 10. FIG. 15A is a diagram showing a possible range of the frequency Fn of the value Ln that satisfies the equation (5). Equation (5) means that it can take a value larger by ΔL than Equation (2). This is because the value Ln of the noise transfer function 90 is smaller than L0 in the case of the frequency Fn that takes the value Ln that satisfies the equation (2), but the frequency Fn is the frequency in the case of the frequency Fn that satisfies the equation (5). In order to apply a case where there is a condition that becomes larger than F0, the range that the frequency Fn can take is expanded.

In other words, it becomes easier to acquire a desired image by expanding the parameter setting range. When the value Ln becomes larger than the value L0 (Ln> L0), the noise increases. Therefore, it is desirable that ΔL be as small as possible (a value close to 0). That is, the determination of Expression (5) is a determination expression that places importance on maintaining or improving image quality.

In the next determination, the frequency Fn is compared with the frequency F0, and it is determined whether the frequency Fn satisfies Expression (4) (S201).
Fn ≧ F0−ΔF (4)
Here, ΔF> 0. This ΔF is one of parameters that can be set in the computer 10. FIG. 15B is a diagram showing a possible range of the frequency Fn that satisfies the equation (4). Equation (4) means that it can take a value smaller by ΔF than Equation (2). This is because the value Ln of the noise transfer function 90 is larger than L0 when the frequency Fn satisfies Expression (2), but the value Ln is compared with L0 when the frequency Fn satisfies Expression (4). In order to apply a case where there is a condition for decreasing, the possible range of the frequency Fn is expanded. That is, it becomes easy to acquire a desired image by expanding the parameter setting range. When the frequency Fn is smaller than the frequency F0 (Fn <F0), the strength of the gradient magnetic field is lowered, so that the S / N and contrast of the captured image are lowered, and the image quality is lowered. Therefore, it is desirable that ΔF be as small as possible (a value close to 0). That is, the determination of Expression (4) is a determination expression that places importance on the maintenance or reduction of the noise level.

FIG. 15C is a diagram showing a possible range of the frequency Fn satisfying both the expressions (5) and (4). When the frequency Fn satisfies both the expressions (5) and (4), it is determined that imaging can be performed with the imaging parameter (second imaging parameter) set by the imaging parameter control unit 30. When it is determined that imaging is possible, information on the imaging parameters is sent to the sequencer 11, and the sequencer 11 generates various commands necessary for data acquisition of tomographic images of the subject 200 and drives the gradient magnetic field power supply 12. Is sent to the gradient magnetic field power supply 12 to capture a tomographic image of the subject 200.

On the other hand, when the value Ln does not satisfy Expression (5), or when Expression (5) is satisfied but Expression (4) is not satisfied, the information is transmitted to the image pickup condition calculation unit 34.

The imaging condition calculation unit 34 calculates a parameter (third imaging parameter) that is close to the parameter condition specified by the user with the imaging parameter control unit 30 and satisfies the equation (5), or the equation (5) and the equation The parameters satisfying both (4) are calculated, and the information is transmitted to the imaging parameter control unit 30 and presented to the user. Based on the presented information, the user selects an imaging parameter that satisfies Expression (5) or satisfies both Expression (5) and Expression (4). Since the selected parameter satisfies both Expression (5) and Expression (4), imaging is possible.

By controlling the imaging parameters in this way, the magnitude of the noise that changes as the imaging parameters are changed is maintained or reduced as much as possible, and the burden on the subject 200 can be maintained or reduced as much as possible. Further, by maintaining or improving the image quality as much as possible, an image desired by the user can be acquired.

(Sixth embodiment)
In the present embodiment, description of portions common to the first embodiment described above is omitted. A specific difference is a frequency analyzed by the frequency analysis unit 32 and a determination formula calculated by the determination unit 33. FIG. 17 is a processing flow of the MRI apparatus according to the sixth embodiment including acquisition of the noise transfer function 90.

First, the frequency analysis unit 32 in the present embodiment will be described. The frequency analysis unit 32 performs frequency analysis of the current waveform received from the current waveform calculation unit 31. Further, a frequency Fnt (t = 1, 2, 3,...) That takes a current value within Δi% from the maximum current value among the frequency characteristics of the analyzed current waveform is calculated (S401). Δi and the interval Δf between adjacent Fnts are set by the computer 10.

FIG. 18 is an example of the frequency characteristics of the current analyzed by the frequency analysis unit 32 and the calculated frequency Fnt. As described above, since there are three current waveforms on the x, y, and z axes, three frequency characteristics of the current are also analyzed. Therefore, the frequency Fnt is calculated for each axis. These are frequencies Fntx, Fnty, and Fntz. These frequencies are transmitted to the determination unit 33.

Next, the determination unit 33 will be described. The determination unit 33 performs a predetermined determination using the frequencies Fntx, Fnty, and Fntz received from the frequency analysis unit 32 and the noise transfer function 90 recorded in advance.

First, a frequency characteristic of a current waveform based on a preset imaging parameter (first imaging parameter), and frequencies F0tx, F0ty, F0tz (which take a current value within Δi% from the maximum current value among the frequency characteristics) (t = 1, 2, 3,...) are calculated and recorded in advance in the determination unit 33 as data. An interval Δf between adjacent F0t is set by the computer 10. Also, values B0tx, B0ty, B0tz of the noise transfer function 90 (Hx, Hy, Hz) corresponding to the frequencies F0tx, F0ty, F0tz are calculated.

This preset imaging parameter, current waveform corresponding to this, frequency characteristic, and frequencies F0tx, F0ty, F0tz (t = 1, 2, taking current values within Δi% from the maximum current value among the frequency characteristics) 3,...), The information including information such as values B0tx, B0ty, B0tz of the noise transfer function 90 (Hx, Hy, Hz) corresponding to the frequencies F0tx, F0ty, F0tz is the first data set.

Next, values Bntx, Bnty, Bntz of the noise transfer function 90 (Hx, Hy, Hz) corresponding to the frequencies Fntx, Fnty, Fntz are calculated (S402). An imaging parameter (second imaging parameter) set by the imaging parameter control unit 30, a current waveform corresponding to the imaging parameter, a frequency characteristic, and a frequency Fnt that takes a current value within Δi% from the maximum current value among the frequency characteristics. Data including information such as (t = 1, 2, 3,...) Is the second data set.

Then, the sound pressure at the microphone 50 at each frequency is calculated using Equation (6) (S403).
P = B × I (6)
here,
P: Sound pressure at microphone 50 B: Value of noise transfer function 90 I: Current applied to gradient coil 3.

The noise value P calculated from Equation (6) includes P0tx, P0ty, P0tz calculated from preset imaging parameters, and Pntx, Pnty, Pntz calculated under conditions when the imaging parameters are changed. .

Next, composite values Q0 and Qn are calculated for each of the calculated P0tx, P0ty, P0tz, and Pntx, Pnty, Pntz using equation (7) (S404).
q0x = 10 × log10 (Σt (10 ^ (P0tx ÷ 10))
q0y = 10 × log10 (Σt (10 ^ (P0ty ÷ 10))
q0z = 10 × log10 (Σt (10 ^ (P0tz ÷ 10))
Q0 = 10 × log10 (10 ^ (q0x ÷ 10) +
10 ^ (q0y ÷ 10) + 10 ^ (q0z ÷ 10))
qnx = 10 × log10 (Σt (10 ^ (Pntx ÷ 10))
qny = 10 × log10 (Σt (10 ^ (Pnty ÷ 10))
qnz = 10 × log10 (Σt (10 ^ (Pntz ÷ 10))
Qn = 10 × log10 (10 ^ (qnx ÷ 10) +
10 ^ (qny ÷ 10) + 10 ^ (qnz ÷ 10)) (7)
Then, the calculated composite values Q0 and Qn are compared and determined (S405). The determination is whether or not the composite value Qn satisfies the equation (8).
Qn ≦ Q0 (8)
FIG. 19 is a schematic diagram until the composite value Qn (and Q0) is calculated. In FIG. 19, the subscripts x, y, and z indicating values on each axis are omitted. When the combined value Qn satisfies Expression (8), the noise is the same or smaller than before the parameter change in the imaging parameter control unit 30. In this case, it is determined that imaging can be performed using the parameters set by the imaging parameter control unit 30. When it is determined that imaging is possible, information on this parameter (second imaging parameter) is sent to the sequencer 11, and the sequencer 11 creates various commands necessary for collecting tomographic image data of the subject 200, and creates a gradient magnetic field. A signal for driving the power supply 12 is sent to the gradient magnetic field power supply 12 to capture a tomographic image of the subject 200.

On the other hand, when the composite value Qn does not satisfy the formula (8), the information is transmitted to the image capturing condition calculation unit 34.

The imaging possible condition calculation unit 34 calculates a parameter (third imaging parameter) that is close to the parameter setting specified by the user using the imaging parameter control unit 30 and satisfies the equation (8), and uses the information as the imaging parameter control unit. 30 to send to the user. The user selects an imaging parameter that satisfies Expression (8) based on the presented information.

In this way, by controlling the imaging parameters using the noise transfer function 90, the magnitude of the noise that changes as the imaging parameters are changed is maintained or reduced, and the burden on the subject 200 can be reduced.

Note that the user can set parameters not only from the viewpoint of noise but also from the viewpoint of images. The computer 10 displays the S / N, contrast, and the like of the image when the image is captured using the imaging parameters received from the image capturing condition calculation unit 34. The user can use this image information as one of the imaging parameter setting support for obtaining a desired image.

(Seventh embodiment)
In the present embodiment, description of portions common to the above-described sixth embodiment is omitted. A specific difference is a determination formula calculated by the determination unit 33. The details of this determination will be described below. FIG. 20 is a processing flow of the MRI apparatus according to the seventh embodiment including acquisition of the noise transfer function 90.

In the present embodiment, the determination unit 33 compares the combined values Q0 and Qn, and determines whether or not the combined value Qn satisfies Expression (9) (S406).
Qn ≦ Q0 + ΔQ (9)
Here, ΔQ ≧ 0.

This ΔQ is one of the parameters that can be set in the computer 10. Equation (9) means that it can take a value larger by ΔQ than Equation (8). This enlarges the parameter setting range and makes it easier to obtain a desired image. When the value Qn becomes larger than the value Q0 (Qn> Q0), noise increases. Therefore, it is desirable that ΔQ be as small as possible (a value close to 0). That is, the determination of Expression (9) is a determination expression that places importance on maintaining or improving image quality.

As described above, the embodiments of the present invention have been described with reference to the first to seventh embodiments. However, the embodiments of the present invention are not limited thereto, and can be appropriately changed without departing from the gist of the invention.

Also, the embodiments are not contradictory to each other. For example, a mode switching function or the like is incorporated, and the most suitable form can be used according to the operation situation or operation environment of the operator.

1 MRI system (magnetic resonance imaging system)
2 Static magnetic field generation means (magnet)
3 Gradient magnetic field coil 4 Irradiation coil 5 Cover 6 Bed 7 Reception coil 10 Computer (control device)
11 Sequencer 12 Gradient magnetic field power supply (Power supply)
13 Signal Processing Unit 30 Imaging Parameter Control Unit 31 Current Waveform Calculation Unit 32 Frequency Analysis Unit 33 Determination Unit 34 Imaging Possible Condition Calculation Unit 40 Control Device 50 Microphone 51 Voltage Current Generator 52 Amplifier 53 Analyzer 90 Noise Transfer Function (Transfer Function)
100 Imaging space 200 Subject 300 Shield room

Claims (15)

A magnet that generates a static magnetic field;
A gradient coil for generating a gradient magnetic field to be superimposed on the static magnetic field;
A power source for applying a current to the gradient coil;
With
The power source is configured to adjust a current waveform of a current applied to the gradient magnetic field coil based on a transfer function representing a relationship between a current applied to the gradient magnetic field coil and generated noise. Magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 1,
A single frequency current or a swept frequency current is applied to the gradient magnetic field coil in advance, noise is acquired by a microphone installed in the center of the imaging space or in the vicinity thereof, and the transfer function is calculated from the noise and the current. Calculate magnetic resonance imaging equipment. The magnetic resonance imaging apparatus according to claim 1,
A storage device in which the transfer function is stored;
An input device for inputting imaging parameters;
A control device that sets a current waveform of a current applied to the gradient magnetic field in the power supply, the control device comprising:
An imaging parameter control unit having information of a current waveform corresponding to the imaging parameter;
A frequency analysis unit for frequency analysis of the current waveform;
Based on the result of the frequency analysis and the transfer function, a determination unit that determines the suitability of the imaging parameter input from the input device;
When the determination is appropriate, the input imaging parameter is maintained, and when the determination is negative, an imaging possible condition calculation unit that presents a new imaging parameter;
A magnetic resonance imaging apparatus comprising: The magnetic resonance imaging apparatus according to claim 3,
The controller is
Of the frequency characteristics of the current waveform corresponding to the first imaging parameter set in advance, the frequency F0 for obtaining the maximum current value and the frequency of the current waveform corresponding to the second imaging parameter input from the input device Among the characteristics, the frequency Fn for obtaining the maximum current value and the numerical values L0 and Ln of the transfer function corresponding to the frequency F0 and the frequency Fn are obtained, respectively.
When the numerical value Ln satisfies the numerical value L0 or less, a current waveform corresponding to the second imaging parameter is set in the power source,
When the numerical value Ln does not satisfy the numerical value L0 or less, the current corresponds to the third imaging parameter that approximates the second imaging parameter and has a new frequency Fn that satisfies the numerical value Ln or less. A magnetic resonance imaging apparatus for setting a waveform to the power source. The magnetic resonance imaging apparatus according to claim 3,
The controller is
Of the frequency characteristics of the current waveform corresponding to the first imaging parameter set in advance, the frequency F0 for obtaining the maximum current value and the frequency of the current waveform corresponding to the second imaging parameter input from the input device Among the characteristics, the frequency Fn for obtaining the maximum current value and the numerical values L0 and Ln of the transfer function corresponding to the frequency F0 and the frequency Fn are obtained, respectively.
When the numerical value Ln satisfies the numerical value L0 + ΔL (ΔL> 0) or less, a current waveform corresponding to the second imaging parameter is set in the power source,
If the numerical value Ln does not satisfy the numerical value L0 + ΔL or less, the current corresponds to the third imaging parameter having a new frequency Fn that approximates the second imaging parameter and that satisfies the numerical value L0 + ΔL or less. A magnetic resonance imaging apparatus for setting a waveform to the power source. The magnetic resonance imaging apparatus according to claim 4,
The controller is
When the Fn satisfies the F0 or more, the current waveform corresponding to the second imaging parameter is set in the power supply,
When the Fn does not satisfy the F0 or more, the current waveform corresponding to the third imaging parameter having a new frequency Fn that approximates the second imaging parameter and that satisfies the Fn or more is F0. Set to magnetic resonance imaging equipment. The magnetic resonance imaging apparatus according to claim 4,
The controller is
When the Fn satisfies F0−ΔF (ΔF> 0) or more, a current waveform corresponding to the second imaging parameter is set in the power source,
When the Fn does not satisfy the F0−ΔF or more, the current corresponds to the third imaging parameter having a new frequency Fn that approximates the second imaging parameter and the Fn satisfies the F0−ΔF or more. A magnetic resonance imaging apparatus for setting a waveform to the power source. The magnetic resonance imaging apparatus according to claim 3,
Among the frequency characteristics of the current waveform corresponding to the first imaging parameter set in advance, a plurality of frequencies F0 for obtaining a current value within Δi% from the maximum current value, and a second frequency input from the input device Among the frequency characteristics of the current waveform corresponding to the imaging parameter, the plurality of frequencies Fn for obtaining a current value within Δi% from the maximum current value, and the plurality of frequencies F0 and the plurality of frequencies Fn respectively. Obtain the transfer function values B0 and Bn,
The product value P0 of the current value I0 corresponding to the F0 and the numerical value B0 is obtained for each of the plurality of F0s, and the resultant value Q0, the current value In corresponding to the frequency Fn, and the numerical value Bn And a combined value Qn obtained by obtaining and adding each product Pn for each of the plurality of Fn,
When the composite value Qn satisfies the composite value Q0 or less, the second imaging parameter is set to the power source,
If the composite value Qn does not satisfy the composite value Q0 or less, a current waveform corresponding to a third imaging parameter having a plurality of new Fn satisfying the composite value Q0 or less is set in the power supply. Magnetic resonance imaging device. The magnetic resonance imaging apparatus according to claim 3,
Among the frequency characteristics of the current waveform corresponding to the first imaging parameter set in advance, a plurality of frequencies F0 for obtaining a current value within Δi% from the maximum current value, and a second frequency input from the input device Among the frequency characteristics of the current waveform corresponding to the imaging parameter, the plurality of frequencies Fn for obtaining a current value within Δi% from the maximum current value, and the plurality of frequencies F0 and the plurality of frequencies Fn respectively. Obtain the transfer function values B0 and Bn,
The product value P0 of the current value I0 corresponding to the F0 and the numerical value B0 is obtained for each of the plurality of F0s, and the resultant value Q0, the current value In corresponding to the frequency Fn, and the numerical value Bn And a combined value Qn obtained by obtaining and adding each product Pn for each of the plurality of Fn,
When the composite value Qn satisfies the composite value Q0 + ΔQ (ΔQ> 0) or less, the second imaging parameter is set to the power source,
When the composite value Qn does not satisfy the composite value Q0 + ΔQ or less, a current waveform corresponding to a third imaging parameter having a plurality of new Fn that satisfies the composite value Q0 + ΔQ or less is set in the power source. A magnetic resonance imaging device. The magnetic resonance imaging apparatus according to claim 3,
The control device presents the third imaging parameter to an operator before setting a current waveform corresponding to the third imaging parameter in the power supply. Magnetic resonance imaging device. The magnetic resonance imaging apparatus according to claim 5,
The controller is
When the Fn satisfies the F0 or more, the current waveform corresponding to the second imaging parameter is set in the power supply,
When the Fn does not satisfy the F0 or more, the current waveform corresponding to the third imaging parameter having a new frequency Fn that approximates the second imaging parameter and that satisfies the Fn or more is F0. Set to magnetic resonance imaging equipment. The magnetic resonance imaging apparatus according to claim 5,
The controller is
When the Fn satisfies F0−ΔF (ΔF> 0) or more, a current waveform corresponding to the second imaging parameter is set in the power source,
When the Fn does not satisfy the F0−ΔF or more, the current corresponds to the third imaging parameter having a new frequency Fn that approximates the second imaging parameter and the Fn satisfies the F0−ΔF or more. A magnetic resonance imaging apparatus for setting a waveform to the power source. An acoustic control method for a magnetic resonance imaging apparatus, comprising: a magnet that generates a static magnetic field; a gradient magnetic field coil that generates a gradient magnetic field superimposed on the static magnetic field; and a power source that applies a current to the gradient magnetic field coil. And
The power supply is
Based on the transfer function representing the relationship between the current applied to the gradient coil and the generated noise, adjust and output the current waveform of the current applied to the gradient coil,
The acoustic control method in the magnetic resonance imaging apparatus, wherein the gradient coil generates the gradient magnetic field based on the adjusted current waveform and superimposes the gradient magnetic field on the static magnetic field. An acoustic control method for a magnetic resonance imaging apparatus according to claim 13,
A control device for controlling a current waveform of a current output from the power source;
The control device calculates the transfer function based on noise acquired at or around the center of the imaging space when a single-frequency current or a frequency-swept current is applied in advance to the gradient coil. An acoustic control method for a magnetic resonance imaging apparatus. An acoustic control method for a magnetic resonance imaging apparatus according to claim 14,
The controller is
The frequency information of the current waveform information corresponding to the imaging parameter is analyzed, the suitability of the imaging parameter is determined based on the result of the frequency analysis and the transfer function, and if the determination is appropriate, the input imaging parameter is An acoustic control method in a magnetic resonance imaging apparatus, which is maintained and presents a new imaging parameter when the determination is negative.

Images