JPH0430830A - Magnetic resonance imaging apparatus - Google Patents

Abstract

PURPOSE:To remove artifact by setting a frequency encoding direction to a way in which a cyclic motion exists in a specific section of an object to be inspected to actuate a means for judging a range of the motion by a one- dimensional Fourier transform of a magnetic resonance signal to be obtained and a presaturation means which is adapted to keep the magnetic resonance signal from being taken out within a range of the motion sequentially. CONSTITUTION:A frequency encoding direction is set to a way in which a cyclic motion exists in a specified section and a magnetic resonance signal to be obtained undergoes a one-dimensional Fourier transform to judge a range of the motion. After the end of the judgement. a are-saturation means keeps the magnetic resonance signal from being taken out within the range of the motion. After the operation. information on a tomographic image in a section specified automatically is allowed to be taken out as magnetic resonance signal. The tomographic image to be obtained from the signal provides an image from which image information is not taken out by the pre-saturation means within the range judged. This enables the obtaining of a tomographic image cleared of artifact with a simple and short-time operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic resonance imaging apparatus that utilizes magnetic resonance phenomena to obtain a tomographic image of a desired region of a subject.

[Prior art]

Conventionally, in this type of magnetic resonance imaging device,
Artifacts on the screen caused by the movement of the subject have been a problem as they impede diagnosis.

For example, as shown in FIG. 2, when capturing a sagittal image of the abdomen of a subject 30 placed in the y-axis direction, the abdominal wall 31 moves in the Z-axis direction with the respiratory cycle due to the breathing movement of the subject. It reciprocates as shown by arrow 32. As a result, as shown in FIG. 3, an artifact 33 is generated in the Z-axis direction, that is, in the phase encoding direction. In FIGS. 2 and 3, reference numeral 40 indicates the subject's vertebrae, and reference numeral 37 indicates the fat region.

Here, the cause of this artifact will be explained by taking as an example the case of a spin echo method (hereinafter referred to as SE method) sequence, as shown in FIG.

FIG. 4(a) shows the application timing of the high-frequency magnetic field, which tilts the macroscopic magnetization caused by the static magnetic field applied to the subject at an arbitrary angle with respect to the direction of the static magnetic field. In addition, the high-frequency magnetic field that tilts the macroscopic magnetization by 90° is pulsed at 90°, and
The high-frequency magnetic field that tilts the magnetic field is called a 1806 pulse.

FIG. 5B shows the application timing of slice direction gradient magnetic fields 21 and 22 that determine the position of the tomographic plane to be imaged.

FIG. 2C shows that measurement is performed by changing the application timing and amplitude of the phase encoding direction gradient magnetic field 23 that determines the position in one direction within the tomographic plane.

The figure (d) shows a gradient magnetic field 24 in the frequency encoding direction that determines the position in the tomographic plane in the direction orthogonal to the phase encoding direction.
．． 25 shows the application timing.

FIG. 2(e) shows the magnetic resonance signal 26 to be measured.

FIG. 6(f) shows the behavior of individual nuclear spins (hereinafter simply referred to as spins) and macroscopic magnetization when viewed as a set of these spins due to the application of each of the high-frequency magnetic fields and gradient magnetic fields. In FIG. 2(f), a thick arrow 27 indicates macroscopic magnetization as a set of magnetic moments of spins, and a thin arrow 28 indicates the magnetic moment of spins.

In such a pulse sequence diagram, first.

After applying a 90° pulse, when a 180″ pulse is applied at a time point of T e /2, where the echo time is Te, the spins will change with respect to the direction of the static magnetic field, as shown in Figure (f). In this state, it precesses with the direction of the static magnetic field as its axis. Because each spin precesses at its own unique speed, a phase difference occurs between the spins over time. When a 180° pulse is applied here, the spins are symmetrically reversed around the X axis as shown in Figure (f), and since they continue to rotate at the same speed, the spins converge again at the echo time Te. A magnetic resonance signal 26 is generated as shown in FIG. 2(e).

Although the magnetic resonance signal 26 is obtained in this manner, it is necessary to determine the spatial (three-dimensional) distribution of the signal in order to construct a tomographic image.

To do this, first, a tomographic plane to be imaged is selected to determine the position in one direction. For this purpose, linear gradient magnetic fields 21 and 22 are applied in the slice selection direction shown in FIG. 4(b).

In this case, a spatially linear magnetic field gradient can be created by superimposing a linear gradient magnetic field on a uniform static magnetic field. According to the principle of magnetic resonance phenomena, the rotational frequency of the precession of spins, that is, the resonance frequency in magnetic resonance phenomena, is proportional to the strength of the received magnetic field. Therefore, when a gradient magnetic field is applied, the resonance frequency of spins differs spatially, and 1 along the direction of slope
change next. Therefore, by applying a high-frequency magnetic field with a frequency corresponding to the position of the tomographic plane to be imaged, it is possible to selectively excite only the spins of the desired tomographic plane.

In the second and third directions, it is sufficient to determine two-dimensional positions within the identified tomographic plane.

To determine the position in the second direction, a linear phase encode direction gradient magnetic field 23 is applied before the magnetic resonance signal measurement, as shown in FIG. 4(c). During the application of this gradient magnetic field, the spins receive a magnetic field with an intensity according to their position, but according to the principle of magnetic resonance, the rotational frequency of the spins is proportional to the strength of the magnetic field it receives, so after the application of the gradient magnetic field, the phase of the spins is It changes linearly according to its position. The magnetic resonance signal 2
By examining this phase information after the measurement in step 6, it becomes possible to determine the spatial position in one of the two dimensions within the tomographic plane.

Next, to determine the position in the third direction, a linear frequency encode direction gradient 24.25 is applied during magnetic resonance signal measurement as shown in FIG. 4(d). The direction of the gradient of the magnetic field strength is perpendicular to the direction of the gradient of the phase encode gradient magnetic field. At this time, according to the principle of the magnetic resonance phenomenon, the rotational frequency of the precession of spins is proportional to the strength of the magnetic field received, so if the magnetic resonance signal is measured while this gradient magnetic field is applied, the frequency of the magnetic resonance signal emitted by the spins will be the same. It changes linearly according to the position. By examining the frequency of the magnetic resonance signal after measuring it, it becomes possible to determine the spatial position in the remaining one dimension of the two dimensions within the tomographic plane.

In this way, the spatial position of the spins in the tomographic plane in the phase encoding direction is determined by Fourier transformation according to the amount of phase rotation caused by the gradient magnetic field that the spins receive before magnetic resonance signal measurement.

However, as shown in FIG. 2, when the abdominal wall 31 is moving, it receives a magnetic field with a different intensity depending on time, which causes an error in the amount of phase rotation it would have when it was stationary. Therefore, the spin is determined to exist in a position different from the original position, and is displayed on the image.

This image is reconstructed as an image at a position in the phase encoding direction according to the amount of error by Fourier transformation, resulting in an artifact 33.

As a method for reducing this artifact 33,
It is known that a presaturation method is used to reduce artifacts by saturating the phase of spins that exist outside the region of interest prior to the imaging sequence, thereby reducing signals from moving parts (patent application). Showa 62
-231644, see patent application No. 64-20436).

An outline of the case where this presaturation method is applied to an SE method sequence will be explained with reference to FIG. Figure 5 (,
) indicates the timing of application of a high-frequency magnetic field that tilts the macroscopic magnetization caused by the static magnetic field applied to the subject at a predetermined angle with respect to the direction of the static magnetic field. FIG. 5(b) shows the behavior of individual spins and macroscopic magnetization in a region to which the presaturation method is not applied. FIG. 5(c) shows the behavior of macroscopic magnetization in the region to which the presaturation method is applied.

In the figure, by applying a high-frequency magnetic field 34 that selectively tilts only the macroscopic magnetization within the presaturation application area by α°, the macroscopic magnetization that was previously oriented in the direction of the static magnetic field (two axes) is now oriented in the same direction. As shown in Figure (c), α0 is selectively inverted.

Here, the setting range of α° to be set will be explained.

When the high-frequency magnetic field is applied, the macroscopic magnetization will be tilted at an angle corresponding to its strength, but after that,
It is known that there is a tendency to return to the original state at a slow speed. Therefore, α° is set to 90@+β0 in anticipation of the return angle β° during the time T from applying the high-frequency magnetic field to applying the 90° pulse 35. From this, the α° is set based on the relationship with the time T.

After applying the high frequency magnetic field 34 in this way, T.
After a period of time, when the 90 m pulse 35 is applied, the longitudinal magnetization (Z-axis direction) component becomes zero, and only the transverse magnetization (in the Xy plane) component can be present. The application pattern of the high frequency pulse and the gradient magnetic field after the application of the 90' pulse 35 is the same as the SE method sequence described above. With this setting, after the 90' pulse 35 is applied, the macroscopic magnetization of the presaturation application area has only a longitudinal magnetization component, as shown in FIG. 2(c). Since only the transverse magnetization component generates a magnetic resonance signal, the macroscopic magnetization in the region that does not undergo presaturation generates a signal, but the macroscopic magnetization in the region that undergoes presaturation does not produce a signal. This means that it will not occur. If it is desired to reduce signals at multiple locations on the subject, the operation of the P unit shown in FIG. 5(C) is repeated a desired number of times for each region. In the gradient field echo method, etc., the transverse magnetization generation pulse corresponding to 9o° pulse 35 of the SE method sequence is 90°.
Although not limited to pulses, it is sufficient to set the angle α and time interval TP according to each pulse.

By applying the presaturation method, which can reduce signals in an arbitrarily set area, to areas with movement such as respiratory movements, the above-mentioned artifacts can be significantly reduced.

[Problem to be solved by the invention]

However, in this presaturation method, the operation for setting the region in which the signal is to be reduced is complicated as described below.

That is, (1) an image of the same cross-section as a desired tomographic image is captured in advance, and the operator has to confirm the captured image screen;

■An operator had to confirm motion artifacts and the moving parts that caused the artifacts.

- The operator had to judge from the screen the area to which the presaturation method was applied.

■The operator had to input the area to which the presaturation method was applied.

This required a procedure.

This series of operations requires effort and time on the part of the operator.
The present invention was made to solve these problems, and its purpose is to eliminate artifacts by extremely simple and short-time operations. An object of the present invention is to provide a magnetic resonance imaging apparatus that can obtain a tomographic image excluding .

[Means to solve the problem]

In order to achieve such an objective, the present invention basically sets a frequency encoding direction in a direction of periodic movement in a specified cross section of a subject, and thereby generates a magnetic resonance signal. a motion range determining means for determining the range of motion by one-dimensional Fourier transform; a presaturation means for preventing magnetic resonance signals from being extracted within the range of motion; The present invention is characterized by comprising means for sequentially operating the tuning means before obtaining tomographic images of the specified cross sections.

[Effect]

In the magnetic resonance imaging apparatus configured in this way, the following operations are automatically performed before obtaining a tomographic image of a specified cross section of the subject.

First, the motion range determining means sets a frequency encoding direction in the direction of periodic motion in the specified cross section, and performs one-dimensional Fourier transform on the magnetic resonance signal obtained thereby to determine the range of motion. be able to. In this case, since the frequency encoding direction is set in the direction of periodic movement, the resulting magnetic resonance signal represents one of the processes of the movement. Therefore, by extracting the magnetic resonance signal a plurality of times, for example, about 10 times, the range of movement can be determined.

Next, after the above-mentioned determination is completed, a pre-saturation means can be used to make it impossible to extract a magnetic resonance signal within the range of the above-mentioned movement.

Furthermore, after such presaturation is completed, tomographic image information on the specified cross section is automatically extracted as a magnetic resonance signal. The tomographic image obtained from this magnetic resonance signal is an image in which image information is not extracted by the presaturation means within the range determined by the motion range determination means.

For this reason, it becomes possible to obtain a tomographic image free of artifacts by an extremely simple and short-time operation.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be specifically described using the drawings.

FIG. 1 is a block diagram showing the overall configuration of a magnetic resonance imaging apparatus according to the present invention. This magnetic resonance imaging apparatus obtains a tomographic image of a subject using magnetic resonance phenomena, and as shown in FIG. , a receiving system 5, a signal processing system 6, a sequencer 7, and a central processing unit (CPU)
8.

The static magnetic field generating magnet 2 generates a uniform static magnetic field around the subject 1 in a direction perpendicular to the body axis of the subject 1. Magnetic field generating means of a normal conductivity type or a superconductivity type is arranged.

The magnetic field gradient generation system 3 consists of gradient magnetic field coils 9 wound in the triaxial directions of X+y*Z, and a gradient magnetic field power supply 10 that drives each gradient magnetic field coil, and a sequencer 7 described later.
Gradient field power source 1 for each coil according to instructions from
By driving 0, gradient magnetic fields Gx, Gy in the three axes of X, y, and z are generated.

Gz is applied to the subject 1. As described in the prior art section, the tomographic plane for the subject 1 can be set by applying this gradient magnetic field. The sequencer 7 repeatedly applies a high-frequency magnetic field pulse in a predetermined pulse sequence to cause magnetic resonance in the nuclei of atoms constituting the tissue of the subject 1, and operates under the control of the CPU 8, Various commands necessary for image data collection are sent to the transmission system 4, magnetic field gradient generation system 3, and reception system 5. Transmission system 4.

This device irradiates high-frequency magnetic field pulses sent from the sequencer 7 to cause magnetic resonance in the atomic nuclei constituting the tissue of the subject 1, and includes a high-frequency oscillator 11, a modulator 12, a high-frequency amplifier 13, and a transmitting side. and a high frequency coil 14a, the high frequency oscillator 1
A modulator 12 modulates the amplitude of the high frequency pulse outputted from the sequencer 1 according to a command from the sequencer 7, and the amplitude modulated high frequency pulse is amplified by a high frequency amplifier 13, and then the high frequency coil 14a is placed close to the subject 1. By supplying the electromagnetic waves to the subject 1, the electromagnetic waves are irradiated onto the subject 1. The receiving system 5 detects echo signals emitted by magnetic resonance of atomic nuclei in the tissue of the subject 1, and includes a receiving side high-frequency coil 14b, an amplifier 15, a quadrature phase detector 16, and an A/D converter 17. The electromagnetic wave of the response of the subject 1 due to the electromagnetic wave irradiated from the transmitting side high frequency coil 14a is detected by the high frequency coil 14b arranged close to the subject 1, and is detected by the amplifier 15 and the quadrature phase detector 16. The signal is input to the A/D converter 17 via the A/D converter 17 and converted into a digital quantity, and is further sampled by the quadrature phase detector 16 at the timing according to the command from the sequencer 7, resulting in two series of collected data, and the signal is subjected to signal processing. It is now sent to system 6. This signal processing system 6
is a CPU 8, a magnetic disk 18, and a magnetic tape 19.
It consists of a recording device such as, and a display 20 such as a CRT, and the CPU performs processing such as Fourier transform, correction coefficient calculation, and image reconstruction, and performs appropriate calculations on the signal intensity distribution of an arbitrary cross section or on multiple signals. The distribution obtained is converted into an image and displayed on the display 20 as a tomographic image.

In addition, in FIG. 1, the high frequency coil 14a on the transmitting side,
14b and the gradient magnetic field coil 9 are installed in the magnetic field space of the static magnetic field generating magnet 2 placed in the space around the subject 1.

The configuration shown in FIG. 1 operates as the CPU 8 performs a series of operations in accordance with a program, and its operations are similar to the block diagram shown in FIG. 6.

In FIG. 6, there is a device main body 61. This device body 6
1 is a static magnetic field generating magnet 2, a magnetic field gradient generating system 3, shown in FIG.
It consists of a transmitting system 4 and a receiving system 5. Furthermore, a sequence 71 for obtaining magnetic resonance signals, which are information on the tomographic plane, is provided. Data for specifying a cross section and output from an input means 62 for inputting a 90° pulse are input to the apparatus main body 61 as described above. Further, there is an input means 63 for inputting data for setting the frequency encoding direction in the y-axis direction and the phase encoding direction in the Z-axis direction, and the output from this input means 63 is sent to the encoding direction conversion section 64. It has been entered. The output of the encoding direction converter 64 is input to a sequence setting circuit 65, and the sequence setting circuit 65 sets the sequence shown in FIG. 10(A).

The output from the sequence setting circuit 65 is input to the main body 61 of the apparatus, and the main body 61 operates based on the sequence along with the input of the 90° pulse.

Now, to explain the sequence, FIG. 10(A) shows a sequence for measuring the movement of the subject 3o. As mentioned above, normally the phase encoding direction is set on the Z-axis, which is the direction of movement, and the frequency encoding direction is set on the y-axis, but here, the frequency encoding direction is set on the Z-axis.

The phase encoding direction is set on the y-axis. Then, the input means 62 applies a 90' pulse 41 and a slice selection gradient magnetic field 42 in the X-axis direction so as to select the same cross section as the set cross section. Next, a slice direction gradient magnetic field 43 for correcting the amount of phase rotation caused by the slice selection gradient magnetic field 42 and returning it to zero, and a frequency encoding gradient magnetic field 4 applied in two axial directions during signal measurement.
A frequency encode gradient magnetic field 44 is applied to correct the amount of phase rotation caused by 5 and return it to zero. Correcting the amount of phase rotation in this way means that the macroscopic magnetization is
'After the point of tilting, spin diffusion occurs, and the absolute value of the projection value of the macroscopic magnetization on the xy plane becomes smaller,
This is done to restore the absolute value to its original value since it becomes impossible to obtain a strong magnetic resonance signal. Further, at this time, in order to maximize the signal strength, no phase encoding gradient magnetic field is applied in the y-axis direction. Thereafter, by applying a frequency encoding gradient magnetic field 45, a magnetic resonance signal 46 is obtained.

Such operations are repeated multiple times at relatively short time intervals within one respiratory cycle or more of the subject 3o, and a corresponding number of magnetic resonance signals 46 are generated. It is now possible to obtain it. It is considered that the number of times the operation is performed is, for example, about 10 times.

In addition, on the other hand, the phase encoding direction is set to the Z axis, and the y
Assuming that the frequency encoding direction is set on the axis, since the movement of the subject is orthogonal to the frequency encoding direction, it will be necessary to operate an extremely large number of times to determine the range of the movement. It is something.

The magnetic resonance signals obtained in this manner are sequentially input to the one-dimensional Fourier transform processing section 66 for each magnetic resonance signal. Then, each output subjected to Fourier transform by this one-dimensional Fourier transform processing section 66 is sequentially
The information is input to the profile processing section 67. The profile processing unit 67 obtains data as shown in FIG. 7 for each magnetic resonance signal, of which data corresponds to maximum inspiration as shown in FIG. The data corresponding to the maximum exhalation time is selected as shown in FIG. In the same figure, abdominal wall 3
It can be seen that a relatively high signal is detected from the fat portion 37 attached to the body.

For this reason, by setting the z-axis in the frequency encoding direction, it becomes possible to obtain the movement of the abdominal wall 31 in an extremely short time. In addition, subject 1
Since the dorsal side of the subject is usually fixed with a bed,
And the absolute position of the abdominal wall 31 can be known. Furthermore, since only the abdominal wall 31 moves during breathing, this measurement allows the motion range 29 of the abdominal wall in two axial directions to be obtained.

Furthermore, a signal corresponding to the data shown in FIG.
The range of movement of 1 is now required. Further, the signal corresponding to the abdominal wall 31 is inputted to a presaturation position determination circuit 69, and the determination circuit 69 determines the presaturation position based on the range of movement of the abdominal wall 31 as shown in FIG. Presaturation method application area 38
is now set.

The output corresponding to the presaturation method application area 38 is input to the presaturation sequence setting circuit 70. In this presaturation sequence setting circuit 70, as shown in FIG.
The sequence shown is now created.

To explain this sequence, an α0 pulse 47 that selectively tilts the spins in the application region 38 shown in FIG. 9 by a predetermined angle α0 and a slice selection gradient magnetic field 48 in the Z-axis direction are applied. As described above, the angle α° is determined to be tilted by 90° when the 90° pulse is applied in anticipation of the angle at which the macroscopic magnetization gradually returns during the time from the application of the α° pulse to the next application of the 90° pulse. This is the angle. Further, the slice selection gradient magnetic field 48 is configured to excite spins having a width corresponding to the application region 38 shown in FIG. 9 by setting its slope.

After the macroscopic magnetization in the presaturation method application area 38 is tilted away from the direction of the static magnetic field in this manner, relatively strong gradient magnetic fields 49, 50, and 51 are applied. The reason for applying such gradient magnetic fields 49, 50, and 51 is as follows.
This is to sufficiently diffuse the spin phase so that information within the application area 38 cannot be extracted. As a result, the macroscopic magnetization within the region 38 not only has a longitudinal magnetization component of zero when the 90'' pulse 52 is applied, but also a phase that is sufficiently diffused so that the transverse magnetization component also becomes zero.

In this state, the main body 61 of the apparatus next operates based on the sequence 71.

This sequence 71 is a conventionally used sequence for forming a tomographic image. Although any measurement sequence can be used in the present invention, a spin echo method sequence is shown in this example. In FIG. 4(C), a 90° pulse 52 and a slice selection gradient magnetic field 53 in the X-axis direction are applied so as to select the same cross section as that selected in FIG. 4(A). As a result, the macroscopic magnetization is tilted by 90 degrees with respect to the direction of the static magnetic field, resulting in transverse magnetization, and a state is reached in which a magnetic resonance signal can be emitted. At this time, the macroscopic magnetization of the region subjected to presaturation as described above does not produce transverse magnetization. Following this, a phase encode gradient magnetic field 54 is applied in the y-axis direction. At the same time, a frequency encode gradient magnetic field 55 is applied to correct the amount of phase rotation caused by the frequency encode gradient magnetic field 58 applied in two axial directions during signal measurement and return it to zero. Next, the 90" pulse 52 is used to invert the phase of the spins in the same cross section as the selected tomographic plane by 180 degrees, thereby obtaining an echo signal.
A slice selection gradient magnetic field 57 is applied. At this time, the slice selection gradient magnetic field 57 also has the effect of correcting the amount of phase rotation caused by the slice selection gradient magnetic field 53 and returning it to zero. By applying a frequency encoding gradient magnetic field 58 in the Z-axis direction following these pulses, a magnetic resonance signal 59 for obtaining a desired tomographic image can be obtained.

This magnetic resonance signal 59 is processed by the two-dimensional Fourier transform processing section 7
2 is set to be input. The two-dimensional Fourier transform processing section 72 creates two-dimensional information on the specified cross section, and this two-dimensional information is input to the image processing section 73. The image processing section 73 performs appropriate image processing on the two-dimensional information and inputs the processed information to the 'CRT 74.

As described above, according to the magnetic resonance imaging apparatus according to the embodiment described above, the following operation is automatically performed before obtaining a tomographic image of a specified cross section of the subject.

First, the motion range determining means sets a frequency encoding direction in the direction of periodic motion in the specified cross section, and performs one-dimensional Fourier transform on the magnetic resonance signal obtained thereby to determine the range of motion. be able to. In this case, since the frequency encoding direction is set in the direction of periodic movement, the resulting magnetic resonance signal represents one of the processes of the movement. For this purpose, a plurality of magnetic resonance signals, for example, one
The range of the movement can be determined by taking out the image about 0 times.

Next, after the above-mentioned determination is completed, the magnetic resonance signal can be prevented from being distorted within the range of the above-mentioned movement by a pre-saturation means.

Furthermore, after such presaturation is completed, tomographic image information on the specified cross section is automatically extracted as a magnetic resonance signal. The tomographic image obtained from this magnetic resonance signal is an image in which image information is not extracted by the presaturation means within the range determined by the motion range determination means.

For this reason, it becomes possible to obtain a tomographic image free of artifacts by an extremely simple and short-time operation.

In the embodiment described above, in order to diffuse the phase and obtain a strong magnetic resonance signal, gradient magnetic fields 49, 50, and 51 are applied in the x, y, and z axis directions, respectively, in FIG. 10(B). However, it is not limited to this, and it goes without saying that the voltage may be applied only in one direction or in two directions, if necessary.

Furthermore, in the above embodiment, as shown in FIG. 10(C), a so-called SE method sequence is used to obtain a magnetic resonance signal of a tomographic image of a specified cross section. Needless to say, it may be a sequence of .

〔Effect of the invention〕

As is clear from the above description, according to the magnetic resonance imaging apparatus according to the present invention, it is possible to obtain a tomographic image free of artifacts by an extremely simple and short-time operation.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram for explaining one embodiment of a magnetic resonance imaging apparatus according to the present invention, and FIGS.
The figure is an explanatory diagram for explaining the problems in conventional magnetic resonance imaging equipment. Figure 4 is an explanatory diagram showing the so-called SE method that has been conventionally performed. Figure 5 is an explanatory diagram that shows the conventionally practiced so-called SE method. An explanatory diagram showing the so-called presaturation method, FIG. 6 is a block diagram for more specifically explaining one embodiment of the magnetic resonance imaging apparatus according to the present invention, and FIG. 7 is an illustration showing the movement of a subject. Fig. 8 is an explanatory diagram of the data for determining the range. Fig. 8 is an explanatory diagram showing the setting directions of the frequency encoding direction and the phase encoding direction in the past. An explanatory diagram showing the range in which the Shun method is performed, Figure 10, is
FIG. 2 is an explanatory diagram showing a sequence of a magnetic resonance imaging apparatus according to the present invention. 64... Encoding direction conversion unit, 65... Sequence setting circuit, 66...-dimensional Fourier transform processing unit, 6
7... Profile processing unit, 68... Difference calculation processing unit, 69... Pre-saturation position determination circuit,
7o... Presaturation sequence setting circuit,
72... Two-dimensional Fourier transform processing unit, 73... Image processing unit. 74...Monitor.

Claims (1)

[Claims] (1) Motion range determination in which the frequency encoding direction is set in the direction of periodic motion in a specified cross section of the subject, and the resulting magnetic resonance signal is one-dimensional Fourier transformed to determine the range of the motion. a presaturation means configured to prevent magnetic resonance signals from being extracted within the range of movement; and a presaturation means for determining the movement range and the presaturation means, respectively, in a step before obtaining a tomographic image of the specified cross section. A magnetic resonance imaging apparatus comprising: means for sequentially operating the apparatus.