JPH0471535A - magnetic resonance imaging device - Google Patents

Abstract

PURPOSE:To continuously obtain the image of a person under test at an optional cross section and region by continuously rewriting the gradient magnetic field control sequence in response to the input for the proper gradient magnetic field control in a real-time magnetic resonance diagnostic device utilizing the echo planar method or high-speed Fourier method. CONSTITUTION:The echo signals from a probe 6 are amplified and detected by a reception section 8, they are collected by a data collection section 10 under the control of a system controller 9, and they are sent to a data processing unit 11 after A/D conversion. The data processing unit 11 applies the image reconfiguration process by Fourier transformation to the input echo signals under the control of an electronic computer 12 to obtain image data. The electronic computer 12 controls the system controller 9 and displays the above image data on an image display 14. Actions of the electronic computer 12 and the image display 14 are controlled via a console 13, and the console 13 has an input means for determining the slice face and region to be imaged. The gradient magnetic field control sequence is continuously rewritten, and the image of a person under test at an optional cross section and region can be continuously obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a magnetic resonance imaging apparatus, and particularly to a magnetic resonance imaging apparatus that selectively images an arbitrary cross section or region of a subject in real time. The present invention relates to a magnetic resonance imaging apparatus that can continuously control the strength of a gradient magnetic field and the frequency of a high-frequency magnetic field through interactive operations.

(Prior art) As is well known, magnetic resonance imaging is a method that uses a high-frequency rotating magnetic field of a specific frequency when a group of atomic nuclei with a unique magnetic moment is placed in a uniform static magnetic field. This is a method of visualizing the chemical and physical microscopic information of a substance by using the phenomenon of absorbing energy resonantly, that is, the phenomenon of magnetic resonance. Magnetic resonance imaging systems that use this magnetic resonance imaging method require more data to form images than other medical image diagnostic equipment such as ultrasound diagnostic equipment or XAICT (computed tomography) equipment. It takes a long time to collect data. Therefore, there are problems in that artifacts occur due to body movements such as respiration of the subject, and it is difficult to image the moving heart and vascular system. In addition, since the time spent being restrained for imaging is long, the pain inflicted on the subject is considerable. ``Therefore, in magnetic resonance imaging, the echo planar method by Mansfield is used as a method for rapidly reconstructing images.
The ultrafast Fourier method by Hutchison et al. has been proposed.

FIG. 7 shows a pulse sequence for acquiring image data using the ultrafast Fourier method (also referred to as the multiple echo Fourier method). While applying the slicing gradient magnetic field Gs, a 90° selective excitation high frequency pulse is applied as the high frequency magnetic field RF to selectively excite the magnetization within the slice (slice region), and then further 180°
After applying a high frequency pulse, a gradient magnetic field Gr for reading in a direction parallel to the slice plane is applied by switching between positive and negative at high speed, and at the same time, a gradient magnetic field Ge for phase encoding in a direction perpendicular to the gradient magnetic field Gs and Gr is applied. It is applied in a pulsed manner at each reversal switching of the read gradient magnetic field Gr. By applying such a pulse sequence,
Since there is a time when the phase of magnetization within a slice is aligned for each switching of the read magnetic field, many signal trains of echo signals are observed. These signal trains can be collected as image generation data within the time that the magnetization within the slice relaxes due to the relaxation phenomenon of transverse magnetization, so it is possible to perform high-speed imaging using the sequence shown in Figure 7. be.

In principle, real-time imaging can be realized by repeating the sequence for performing imaging at high speed as described above. however,
Mere repetition can be achieved using a conventionally used sequence controller, but it cannot be applied to applications where the sequence is continuously changed in order to make more effective use of the characteristics of real-time imaging. x, y corresponding to each gradient direction of the gradient magnetic fields Gx, Gy and Gz (usually used for reading, phase encoding and slicing, respectively) from
In order to select an arbitrary slice plane in a direction that does not correspond to each direction of the Z-axis, at least two of the gradient magnetic fields Gx, Gy, and Gz are simultaneously applied with the magnetic field strength adjusted appropriately, and the magnetic field strength is adjusted as appropriate to select an arbitrary slice plane. A method (oblique scan) is used in which the gradient magnetic field Gr, the phase encoding gradient magnetic field Ge, and the slicing gradient magnetic field Gs are vectorially synthesized. However, in order to execute arbitrary angle changes in real time, continuous changes in the sequence are required. When performing ultrafast imaging methods such as the ultrafast Fourier method, highly accurate sequence adjustment is required.
When reading a timetable stored in a memory to control a sequence, a large-capacity timetable is required.

As the capacity of a time table increases, it becomes more difficult to rewrite the time table at high speed by selecting an arbitrary cross section or area.

(Problems to be Solved by the Invention) As described above, when attempting to perform real-time imaging, which is made possible by continuously applying an ultra-high-speed imaging method, the sequence controller of the conventional magnetic resonance imaging apparatus mainly Due to sequence controllers, it has been difficult to take advantage of the inherent advantages of real-time imaging. That is, there is a problem with the input environment for specifying arbitrary cross sections and regions of the object continuously and in real time. Furthermore, it has not been possible to change the sequence in real time to achieve imaging of specified cross sections and regions.

The present invention solves such problems and provides an input means and method for selecting an arbitrary cross section and region of a subject in real time, and a gradient input means and method for imaging the selected arbitrary cross section and region. The object of the present invention is to present a method for changing the magnetic field strength or the frequency of a high-frequency magnetic field and a method for imaging the same, and to provide a magnetic resonance imaging apparatus using the method.

[Structure of the Invention] (Means for Solving the Problems) A magnetic resonance imaging apparatus according to the present invention applies a high-frequency magnetic field and a gradient magnetic field to a subject placed in a uniform static magnetic field according to a predetermined pulse sequence. In a magnetic resonance imaging device that detects and visualizes nuclear magnetic resonance signals from inside a subject, all the data necessary for image reconstruction of the slice excited by the above-mentioned high-frequency magnetic field can be collected using a read gradient magnetic field at high speed. A series of cycles are continuously repeated in which data is collected within the time period during which the magnetization in the slice is relaxed by the relaxation phenomenon of transverse magnetization by switching and applying a phase encoding field during the switching of the read gradient magnetic field. , a sequence control means for controlling a magnetic field application sequence so as to collect data for reconstructing an image in real time; a data collection means for collecting data synchronously with the control of the gradient magnetic field; a data processing means that processes the data collected by the data collection means to continuously reconstruct images in real time in synchronization with the data collection; and a display that continuously displays the reconstructed image data. means and
input means for selecting an arbitrary cross section or region of the object; and rapidly changing at least one of the gradient magnetic field strength and the frequency of the high-frequency magnetic field in order to visualize the cross section and region selected by the input means. By providing a magnetic field control means for controlling the magnetic field, arbitrary cross sections and regions can be visualized continuously.

(Function) In the present invention, in a real-time magnetic resonance diagnostic apparatus using the echo planar method, fast Fourier method, etc., the gradient magnetic field control sequence is continuously rewritten in accordance with input for appropriate gradient magnetic field control. Continuously visualize arbitrary cross sections and regions of the specimen.

(Embodiment) FIG. 1 shows the configuration of a magnetic resonance imaging apparatus according to an embodiment of the present invention.

In FIG. 1, a static magnetic field magnet 1 and a gradient magnetic field coil 3
are respectively driven by an excitation power source 2 and a drive circuit 4 controlled by a system controller 9, and apply a uniform static magnetic field and a gradient magnetic field to a subject 5 (for example, a human body). The gradient magnetic field is a magnetic field whose magnetic field strength gradually changes spatially in two orthogonal directions r and e within a desired cross section (slice plane) of interest, and in the normal direction S of the slice plane. In this embodiment, hereinafter, the gradient magnetic field applied in the normal direction of the slice plane will be referred to as the slicing gradient magnetic field Gs, the gradient magnetic field applied in an appropriate direction within the slice plane will be referred to as the read gradient magnetic field Gr, and these gradient magnetic fields for slicing Gs. A gradient magnetic field applied in a direction perpendicular to both the read gradient magnetic field Gr and the read gradient magnetic field Gr will be described as a phase encode gradient magnetic field Ge.

A high-frequency magnetic field generated from the probe 6 is further applied to the subject 5 under the control of the system controller 9 in response to a high-frequency signal output from the transmitter 7. In this embodiment, the probe 6 is The probe 6 is commonly used as a transmitter coil for high-frequency transmission and a receiver coil that receives magnetic resonance signals related to various atomic nuclei in the subject 5. In this case, the probe 6 is commonly used as a transmitter coil and a receiver coil. However, the transmitting coil and receiving coil may be provided separately.

A magnetic resonance signal, such as a magnetic resonance echo signal, received by the probe 6 is amplified and detected by a receiving section 8 and then sent to a data acquisition section 10 under the control of a system controller 9. The data acquisition section 10 collects the magnetic resonance echo signals taken out via the reception section 8 under the control of the system controller 9, converts them into A/D (analog-digital), and then sends them to the data processing section 11. send.

The data processing unit 11 is controlled by an electronic computer 12,
The magnetic resonance echo signals provided from the data acquisition unit 10 are subjected to image reconstruction processing using Fourier transformation to obtain image data. The electronic computer 12 also controls the system controller 9. Image data obtained by the data processing section 11 is supplied to the image display 14 and displayed as an image. Electronic computer 12 and image display 1
4 is controlled by operation of the console 13.

The console 13 also has input means for determining the slice plane and region to be visualized.

Here, we will consider the degree of freedom required to determine the slice plane and region.

First, a method for expressing angles will be explained.

In the xyz orthogonal coordinate system as shown in FIG. 3, if the given spatial angle is θ from the Z axis as shown, and the angle between the projection onto the xy plane and the X axis is φ, then
A unit vector in any direction can be expressed as +cosθ −cosφ °ey using unit vectors ex, ey, and ez in the xyz coordinate system. Here, the angle defined by θ and φ is referred to as a polar space angle.

That is, to determine the slice plane and region,
The degree of freedom for determining the three-dimensional polar space angle of the normal vector of the slice plane that defines the slice plane is 2, the degree of freedom for rotation of the image within the set slice plane is 1, and the degree of freedom for the rotation of the image within the set slice plane is 1. There are 3 degrees of freedom for positioning in xyz coordinates, and 1 degree of freedom for enlarging/reducing the image within the determined slice plane.
A total of 7 degrees of freedom can be considered.

In order to set the degree of freedom of the polar space angle of the slice plane, use the existing gradient magnetic fields Gx, Gy, and Gz to generate gradient magnetic fields with appropriately set amplitudes at the same timing, and calculate the vector of these gradient magnetic fields. This technique itself has already been used in oblique scans, as it is only necessary to make the direction of the resultant vector coincide with a desired polar space angle.

To set the degree of freedom of position, in addition to moving the bed in the direction of the gradient magnetic field Gz force, it is also used to move back and forth in the slice axis direction (normal direction of the slice plane) and to realize multi-slices. There is a method of changing the center frequency of the high-frequency magnetic field.

Various proposals have already been made regarding sequences for moving the center position of an image.

In addition, the degree of freedom for image enlargement/reduction can be set using the gradient magnetic field G.
In order to enlarge one image, which can be achieved by changing the intensity of the gradient magnetic fields Gr and Ge, it is necessary to limit the area if aliasing occurs due to the enlargement of the 0 image by increasing the intensity of the gradient magnetic fields Gr and Ge. There is. The region in the read direction can be limited by using a filter to remove high frequency components of the original waveform before Fourier transform.

Regarding the encoding direction, since the filter operation as in the read direction cannot be performed, it is necessary to selectively saturate the portion in the encoding direction in advance.

As shown in FIG. 6(b), in order to selectively excite and saturate two regions sandwiching a desired region in the encoding direction, a selective saturation pulse in the encoding direction is applied at the beginning of the sequence. That is, before the sequence of FIG. 7 for imaging, two 90
° Apply selective excitation high-frequency pulses and gradient magnetic fields with different polarities in each lead direction. In this case, a first 90° selective excitation high frequency pulse is applied while applying a gradient magnetic field of a first polarity in the encoding direction, and
while applying a gradient magnetic field of a second polarity opposite to the second 90
°Apply selective excitation high-frequency pulses. In Figure 6, the selectively excited parts are symmetrical, but the gradient magnetic field strength and f
By changing c, any region can be selectively excited. By the time a true 90° pulse for imaging is applied afterwards (before longitudinal relaxation has substantially progressed), the excited part is already saturated and is not excited. By applying selective excitation high-frequency pulses containing frequency components corresponding to the two selective excitation regions while applying a gradient magnetic field, it is also possible to selectively excite the two regions at the same time.

When aliasing occurs in the encoding direction, it is necessary to use a sequence that can prevent aliasing as described above.

The input of each degree of freedom for position and angle is as shown in Figure 2.
Trackballs 21 and 22 attached to the console 13
, using a pointing device such as a slider 23, 24, or 25. In this case, separate input means may be provided for each of the seven degrees of freedom, or a parallel translation/rotation switch shown in Fig. 2 may be used. By providing appropriate switching function means as in 26, it is possible to set multiple degrees of freedom using one input means.The operator attempts to visualize the subject by operating these input means. It is possible to set the slice plane and region.

In addition, an image showing the polar space angle with respect to the xyz coordinates of the slice plane and region to be imaged of the set object to be imaged, for example, a line drawing of the imaging region of the object, a magnetic resonance imaging apparatus (MRI), a computer tomography system, etc. Equipment (C
By providing a display device that continuously displays images superimposed on images obtained by a T device or the like, it becomes easy for the operator to continuously and interactively select arbitrary slice planes and regions.

In this apparatus, a sequence as shown in FIG. 7, for example, is used as a pulse sequence for collecting image data of a slice plane within the subject 5. This pulse sequence is controlled by the system controller 9. Basically, by using this sequence, it is possible to collect data for visualization.

That is, first, in order to selectively excite the magnetization in the slice of interest in the subject 5, a slicing gradient magnetic field Gs is applied to the subject, and a high frequency magnetic field RF 9 is applied to the subject.
A specific slice within the subject 5 is selectively excited by applying a 0° selective excitation high frequency pulse (a high frequency pulse for rotating only the magnetization of a predetermined slice region by 90'').

The slicing gradient magnetic field Gs is 90" after the application of the high-frequency pulse for selective excitation, and is inverted in order to align the phase of magnetization. In order to cancel the influence of spatial inhomogeneity of the static magnetic field, the slicing gradient magnetic field Gs is 180". Apply high frequency pulses. At this time, no gradient magnetic field is applied.

Furthermore, as shown in FIG. 7, the reading gradient magnetic field Gr is switched so as to alternately reverse the polarity in one direction, for example, the With repeated application,
A phase encoding gradient magnetic field Ge is applied in the other direction of the xy plane, for example in the y direction, in a pulsed manner synchronously during the reversal switching period. As a result, a magnetic resonance signal, that is, a magnetic resonance echo signal S i g, is obtained from within the subject 5 every time the reverse switching is performed. The image data of the slice is generated by collecting a train of these echo signals as magnetic resonance data and performing Fourier transformation to reconstruct the image.

Setting of an arbitrary cross section is performed as follows.

First, in order to realize the setting of the translation position (translation position), the following four adjustment items need to be adjusted.

(1) Continuously change the application frequency of the high-frequency pulse in the slice axis direction. This can be achieved by fine-tuning the center frequency of the high-frequency signal source.

(This method is also used for multi-slice imaging.

Slice thickness can be kept constant. ) (2) In order to realize area expansion, gradient magnetic fields Gr, G
Increase the strength of e.

(3) In order to prevent aliasing due to area expansion in the read direction, high frequency components of the received magnetic resonance signal are removed by a filter.

(4) In order to prevent aliasing due to area expansion in the encoding direction, it is necessary to perform selective saturation using bripulse.

Of these four adjustment items, (1) and (3) can be easily achieved using conventional equipment without changing the pulse sequence. That is,
Regarding (2), there is no need to rewrite the sequence table when a predetermined pulse sequence is executed by sequentially reading out a sequence table in which pulse peak values are stored in advance in a storage means in relation to elapsed time. ,
It is necessary to rewrite the table values of the gradient magnetic fields Gr and Ge in the sequence table, that is, the pulse height values, according to the control input according to the enlargement ratio. Regarding (4), it is also necessary to simultaneously change the table value of the gradient magnetic field Ge in the sequence table and the value of the center frequency fc of the high-frequency pulse. The value of the gradient magnetic field Ge in this case is (2)
independent of control over the selection site.

For setting the polar space angle, use the gradient magnetic fields Gx, Gy, Gz
A gradient magnetic field in a desired direction may be created by vector composition of .

In order to visualize an arbitrary cross section at high speed, the sequence controller has an RF frequency, that is, the center frequency fc of the high-frequency pulse, and gradient magnetic fields Gr, Ge, and Gs, in order to realize the coordinate conditions arbitrarily specified by the operation input. A function to output each gradient strength at high speed is required.

(a) Changing the RF frequency to change the slice plane position on the slice axis is realized in multi-slice imaging even with current devices.

(b) The read gradient magnetic field Gr needs to have an intensity proportional to the expansion rate in order to expand the area. Also, in this case,
To prevent aliasing, it is also necessary to remove high frequencies using a filter. Regarding the gradient magnetic field Gr set in this way, in order to further realize the gradient magnetic field Gr with the gradient coils of the gradient magnetic fields Gx, Gy, and Gz, vector decomposition as shown in FIG. 3 is performed, that is, the polar space angle θ , in order to generate the read gradient magnetic field Gr in the direction expressed by φ, Gx=Gr−sinθ・cosφ−(1)Gy=G
r-s inθ・sinφ ・(2) Gz=Gr-c
Gradient magnetic field Gx so that osθ ・(3)
, Gy, Gz, which is expressed in the form of a multiplication (product) for the gradient magnetic field Gr. For example, the polar space angle θ,
If the setting pitch of φ is about 1°, the multiplication value can be formed as a small table, and by using such a table, the above multiplication result can be easily obtained.

(C) Regarding the encoding gradient magnetic field Ge, for region expansion and direction setting, read gradient magnetic field G in (b)
As for folding, which is done in exactly the same way as in the case of r, as mentioned above, it cannot be removed with a filter, so it is necessary to selectively saturate unnecessary areas using Bripulse. The strength of the encoding gradient magnetic field Ge is changed according to the .

(d) Regarding the gradient magnetic field Gs for slicing, there is no need to change the strength except when changing the slice thickness.The setting of the gradient direction of the gradient magnetic field Gs for slicing is as shown in (b)
This is realized by vector composition as in case (C).

For imaging, a timetable for setting the gradient magnetic field strength corresponding to each axis direction of the coordinate system is required. This timetable is a sequence as shown in Fig. 7, and waveform data of 30 to 50 m5 minutes is 0. 5～
Since it is held at time intervals of 5 μs, a large capacity storage device is required.

In order to perform real-time imaging with a magnetic resonance imaging system, it is necessary to perform imaging every 30 to 50 m5, and to do so, it is necessary to rewrite the above table every time imaging is performed, so the coordinate system conversion requires Requires ingenuity.

A first example of a sequence controller that realizes such coordinate transformation is shown in FIG.

First, data is read out from the storage devices 31, 32, 33 for the timetables of the gradient magnetic fields Gr, Ge, and Gs, and constant multiplication and coordinates for area expansion, etc. are read out from the storage devices 31, 32. Above (1) for conversion
) to (3), external operation inputs (for example, inputs from trackballs, sliders, etc., multiplexed with a multiplexer) are taken in at regular intervals and multiplied by the above constant. and used for coordinate transformation.

In order to execute the sequence continuously, a plurality of sequence output buffers 36 to 41 are prepared and the switch 5
Settings are made so that W1-8W3 and switches SW4-SW6 can be switched exclusively. In this case, writing to the output buffers 36 to 41 and outputting to the D/A converters 42 to 44 are performed alternately. If the calculation/writing time is insufficient, increase the number of output buffers and However, in this case,
A time difference occurs between the input sequence and the sequence being executed.

A second example of a sequence controller that realizes the coordinate transformation described above is shown in FIG. 5. In FIG. 5, parts that are substantially the same as those in FIG. 4, such as a time table, are designated by the same reference numerals. .

A combination of nine multipliers 51 to 59 and three adders 60 to 62 as shown in the figure is used to convert the coordinate system immediately before performing D/A conversion. In this case, the arithmetic processing unit ff16
3 is used to set the spatial angle based on external operation input such as a trackball or slider. The operator operates each operating means with approximately two degrees of freedom. For example, taking the gradient magnetic field Gs as an example, (1) to (
3) Multiply the gradient magnetic fields Gx, Gy, G as shown in the formula.
Find the contribution to z. In addition, regarding the gradient magnetic fields Gr and Ge, after performing the scaling factor operation, the gradient magnetic field G
The gradient magnetic field Gx is obtained by adding the contributions from the gradient magnetic fields Gr, Ge, and Gs, which are decomposed in the same way as s.
, Gy, and Gz are determined. With this configuration, it is possible to execute a sequence that reflects the input state with almost no time delay.

The configuration shown in FIG. 4 or 5 is provided in relation to the system controller 9, computer 12, and console 13 shown in FIG.

In addition, although the case where the ultrafast Fourier method was used as a basic ultrafast imaging sequence was described above, it can be implemented in substantially the same way as described above even if the echo planar method is used.

In addition, pointing devices used as input means for selecting at least one of an arbitrary slice and region are not limited to trackballs and sliders, but also include mice, joysticks, digitizers, etc.
They may be used singly or in combination.

In addition, the present invention can be implemented with various modifications without changing the gist thereof.

[Effects of the Invention] According to the present invention, in a real-time magnetic resonance diagnostic apparatus using an echo planar method, a fast Fourier method, etc., a gradient magnetic field control sequence can be continuously rewritten in response to an input for appropriate gradient magnetic field control. It is possible to provide a magnetic resonance imaging apparatus that can continuously image arbitrary cross sections and regions of a subject.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a magnetic resonance imaging apparatus according to an embodiment of the present invention, FIG. 2 is a diagram schematically showing the console and display in the same embodiment, and FIG. 3 is an x, y , a diagram showing vector decomposition from Gs to Ox, Gy, and Gz having spatial angles θ and φ with respect to the z-axis, and FIGS. 4 and 5 show different examples of the means for setting the spatial angle in the same embodiment. FIG. 6 is a diagram for explaining selective excitation such as slicing, and FIG. 7 is a diagram showing a pulse sequence of the fast Fourier method. DESCRIPTION OF SYMBOLS 1...Static magnetic field magnet, 2...Power source for excitation, 3...Gradient coil, 4...Power source for gradient coil, 6...Probe, 7...Transmitter, 8...Receiver part, 9... system controller, 10... data collection part,
11...Data processing section. 12...Electronic computer, 13...Console, 1
4... Image display. No. 2￥A No. 1 illustration No. 1 [Maki no.

Claims (6)

[Claims] (1) Applying a high-frequency magnetic field and a gradient magnetic field to a subject placed in a uniform static magnetic field according to a predetermined pulse sequence,
In a magnetic resonance imaging apparatus that detects and images nuclear magnetic resonance signals from within a subject, an input means for an operator to interactively select at least one of an arbitrary cross section and region of the subject, and the input means gradient magnetic field control for appropriately changing gradient magnetic field intensities applied in mutually orthogonal x-, y-, and z-axis directions in order to select and image at least one of an arbitrary cross section and region of the subject selected by a high-frequency magnetic field control means for appropriately changing the frequency of the applied high-frequency magnetic field; and a high-frequency magnetic field control means for appropriately changing the frequency of the applied high-frequency magnetic field; and display means for continuously displaying whether the area is a region or not in response to an input. (2) The magnetic resonance diagnostic device described above uses high-speed switching of the gradient magnetic field for leads to rapidly collect and visualize all the data necessary for image reconstruction within the time that the transverse magnetization in the excitation slice plane relaxes. A magnetic resonance diagnostic device,
data collection processing means that performs data collection and data processing continuously and in real time; image reconstruction and visualization means that performs image reconstruction and visualization continuously and in real time; an input means for interactively selecting a cross section and region of the object while observing an image of at least one of the arbitrary cross section and region of the object to be temporally reconstructed and visualized; a magnetic field determination means for determining in real time and continuously the gradient magnetic field strength and the frequency of the high-frequency magnetic field necessary for imaging a region; magnetic field control means that continuously and in real time changes the gradient magnetic field strength applied in the x, y, and z-axis directions and the application frequency of the high-frequency magnetic field in accordance with the determined values so that the magnetic field can be selected. The magnetic resonance diagnostic apparatus according to claim 1. (3) The input means for selecting at least one of the arbitrary cross section and region includes one or more indicating means for indicating a point or region on the image, and the input means for selecting the cross section and region. Means for dynamically or statically allocating each degree of freedom, and gradients required to visualize an appropriate cross section and area from the indicated values of the above indicating means each time a gradient magnetic field sequence is applied continuously and in real time. 2. The method according to claim 1, further comprising means for calculating desired values of the magnetic field strength and the frequency of the high-frequency magnetic field, and means for sequentially displaying the cross sections and regions set by the means in parallel with imaging of the subject. 2 magnetic resonance imaging device. (4) In order to control the gradient magnetic field strength in real time, the sequence controller has a three-channel video timetable of gradient magnetic field strength for reading, gradient magnetic field strength for phase encoding, and gradient magnetic field strength for slicing; The gradient magnetic field strength of the above three video channels is calculated using x, y installed in the device.
, and means for converting into gradient magnetic field intensities of three channels corresponding to the z direction.
The magnetic resonance imaging apparatus according to any one of items 2 and 3. (5) The sequence controller includes means for storing a video timetable, a plurality of output buffers, and a plurality of calculation means, and the gradient magnetic field actually applied to the x, y, and z axes from the video timetable. 5. The magnetic resonance imaging apparatus according to claim 1, wherein the conversion to intensity is performed continuously by alternately using buffers. (6) The above sequence controller includes three multipliers for each timetable to obtain control signal outputs from the video timetable to the gradient magnetic field coils, and three multipliers for each timetable to associate them with each gradient magnetic field coil. 5. The magnetic resonance imaging apparatus according to claim 1, further comprising an addition means and a digital/analog conversion means, and performs conversion at high speed.