JP2000005142A - Method and device for magnetic resonance imaging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of a diagnosis by preventing the concentration resolution of an inspection subject portion from being limited by the high signal generated by fat tissues or an artificial object buried in a body. SOLUTION: The inspection portion of a subject is arranged in a uniform static magnetic field space, and the high-frequency magnetic field 51 saturating the hydrogen atomic nucleus of fat tissues within the nuclear spin of the inspection portion is applied. The second high-frequency magnetic field 52 saturating the hydrogen atomic nucleus contained in the artificial object of the inspection portion, e.g. a silicone insertion object, is applied. The respective hydrogen atomic nuclei are effectively saturated. The photographing sequence adapted to the inspection purpose is continued, and the aimed portion is drawn with high concentration resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to nuclear magnetic resonance (hereinafter, referred to as "nuclear magnetic resonance").
Magnetic resonance imaging (hereinafter referred to as M) for non-invasively measuring the inside of a human body using the phenomenon of NMR for medical diagnosis.
In particular, the present invention relates to an MRI method and an apparatus thereof for suppressing signal intensity that interferes with diagnosis such as fat.

[0002]

2. Description of the Related Art An MRI apparatus is an apparatus that obtains an anatomical tomographic image of a living body such as a human body using NMR, and obtains useful medical diagnostic information different from conventional examinations using X-rays or ultrasonic waves. Has been widely used in medical facilities.

[0003] In general, MRI measures an NMR signal from a proton of a hydrogen atom contained in a human body. That is, a high-frequency magnetic field of a predetermined frequency band is applied to hydrogen nuclear spins (hereinafter, simply referred to as spins) constituting a subject tissue placed in a static magnetic field to excite the spins and recover the longitudinal magnetization of the spins. The magnetic field generated when
Measure as a signal. At this time, a gradient magnetic field is applied to give positional information to the NMR signal. In MRI, the number of signals required for image reconstruction is measured by repeating such a high-frequency magnetic field application and NMR signal measurement for a predetermined repetition time (TR) while changing the gradient magnetic field strength.

[0004] Here, even if the spins of the same hydrogen nucleus are included, spins contained in adipose tissue and spins in other tissues have different recovery times (relaxation times) of longitudinal magnetization. Generally, hydrogen nuclei contained in adipose tissue have a relaxation time (typically, T
1 and T2) are shorter than other tissues,
The nuclear spin state almost recovers to the initial state within the R time.
As a result, adipose tissue always generates high NMR signal intensity during the repetition of measuring a series of matrix data.
Since the dynamic range of the signal processing system and the image display system of the MRI apparatus is constant, it is impossible to image a site to be diagnosed or a lesion site with high density resolution in an examination site including a tissue that generates a high signal intensity.

In order to avoid this phenomenon, the relaxation time of hydrogen nuclei in adipose tissue is short, and therefore, 18 hours before imaging.
An inversion recovery method is used in which all nuclear spins are inverted by a high-frequency pulse of 0 ° and a fat signal is suppressed by utilizing a difference in recovery characteristics.

Alternatively, utilizing the fact that the hydrogen nucleus of adipose tissue has a slightly different resonance frequency from the hydrogen nucleus of another tissue (the hydrogen nucleus of adipose tissue and the hydrogen nucleus of water have a chemical shift of about 4 ppm). Before imaging, a method is used in which a high-frequency pulse having a band of hydrogen nuclei of adipose tissue is applied in advance to saturate only the hydrogen nuclei of adipose tissue (magazine "Video Information" Vol. 28, No. 10, 613).
Pp. 619).

[0007]

In the above prior art, the diagnostic site can be drawn with high concentration resolution by suppressing the signal of hydrogen nucleus in adipose tissue, and the diagnostic capability of MRI has been dramatically improved. On the other hand, in subjects who have inserted artificial compounds (silicone) in the examination of female breasts, hydrogen nuclei contained in the silicone insert exhibit a high signal intensity similar to hydrogen nuclei contained in adipose tissue. There is a problem. However, since the relaxation time and resonance frequency of the hydrogen nuclei contained in the silicone insert are different from the relaxation time and resonance frequency of the hydrogen nuclei contained in the adipose tissue, the conventional method cannot cope with the problem, and the diagnosis site cannot be treated. Cannot draw with high concentration resolution.

SUMMARY OF THE INVENTION An object of the present invention is to provide an MRI method and apparatus which, when there are a plurality of types of signals which hinder diagnosis, suppress these signals in advance and render a diagnostic image with high density resolution. It is in. It is an object of the present invention to provide an MRI method and apparatus which suppresses signals from adipose tissue and silicone in advance in mammography (breast examination) and renders a diagnostic image with high density resolution.

[0009]

In order to achieve the above object, an MRI method according to the present invention is a magnetic resonance imaging method for producing a tomographic image of an examination site by causing a nuclear magnetic resonance phenomenon in the examination site of a subject. A) arranging the inspection site in the static magnetic field space; b) applying a first high-frequency magnetic field having a frequency ω1 to the inspection site; c) applying a frequency ω2 (ω2 ≠ ω1, hereinafter the same) to the inspection site. Applying a second high-frequency magnetic field having a frequency band including the frequency ω1 and the frequency ω2 to the inspection site.

In this MRI method, by applying a first high-frequency magnetic field, only the first nuclear nucleus that interferes with the diagnosis, for example, only the hydrogen nucleus of adipose tissue, out of the nuclear spins of the examination site, is saturated. Next, by applying a second high-frequency magnetic field, only the second nuclei that interfere with the diagnosis, for example, the hydrogen nuclei contained in the silicone insert at the inspection site, are saturated. In a state where the hydrogen nuclei of these fatty tissues and silicone are saturated, using a third high-frequency magnetic field,
By executing an imaging sequence suitable for the purpose of the examination, it is possible to obtain an image in which signals from atomic nuclei that hinder diagnosis, that is, signals from fat tissue or silicone, are suppressed.

Further, the MRI method of the present invention is a magnetic resonance imaging method for obtaining a tomographic image of the inspection site by causing a nuclear magnetic resonance phenomenon in the inspection site of the subject, wherein a) disposing the inspection site in a static magnetic field space. B) at least two different resonance frequencies ω1, of the nuclear spins of the examination site;
applying a high frequency magnetic field that substantially simultaneously saturates the nuclear spins of the tissue having ω2, and c) nuclear magnetic field from the test site using a third high frequency magnetic field having a frequency band including frequencies ω1 and ω2 at the test site Driving a pulse sequence that measures the resonance signal.

Also in this case, by applying a high-frequency magnetic field for substantially simultaneously saturating the nuclear spins of the tissues having the resonance frequencies ω 1 and ω 2, the hydrogen nuclei of the fat tissue and silicone are saturated, and the signals from these are converted. Can be suppressed.

In the MRI method of the present invention, after the step a) of arranging the inspection site in the static magnetic field space, 1) the step of applying a high-frequency magnetic field for exciting a predetermined nuclear spin of the inspection site, 2) the nuclear spin Measuring a nuclear magnetic resonance signal from the nuclear magnetic resonance signal; and 3) obtaining a frequency spectrum from the nuclear magnetic resonance signal to determine at least two different resonance frequencies ω1, ω2.
Perform the step of finding Thereafter, the steps after step b) described above are executed. These 1) ~
By performing the step 3), the resonance frequencies ω1 and ω2 of the nuclear spins of the tissue to be signal-suppressed can be accurately obtained for the subject to be examined, whereby the signals from fatty tissue and silicone can be reliably obtained. Can be suppressed.

An MRI apparatus according to the present invention is configured to execute the above MRI method. That is, a static magnetic field generating means for generating a uniform static magnetic field in the space in which the subject is disposed, a gradient magnetic field generating means for generating a magnetic field having a different magnetic field strength according to the position in the space, and a resonance of the nuclear spin of the subject. A means for generating a high-frequency magnetic field to be excited; a means for detecting a nuclear magnetic resonance signal of nuclear spin; and a means for performing arithmetic processing on the detected signal and displaying a result thereof. Means for generating a plurality of high-frequency magnetic fields to selectively excite nuclear spins of at least two specific tissues of the specimen. Specifically, the means for generating the high-frequency magnetic field includes a first high-frequency magnetic field having the frequency ω1, a second high-frequency magnetic field having the frequency ω2, and a frequency band including the frequency ω1 and the frequency ω2 under the control of the arithmetic processing means. Means for generating a third high-frequency magnetic field.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of an MRI apparatus to which the present invention is applied. This MRI apparatus mainly includes a gantry section and a control section. The gantry section incorporates a magnet device 2 for generating a uniform magnetic field in a space where an examination site of the subject 1 is provided. Three axes (x, y, z) orthogonal to each other in the static magnetic field space to be formed
And a high-frequency coil 4 for generating a high-frequency magnetic field for exciting a nuclear spin at the inspection site, and a high-frequency coil 5 for detecting an NMR signal from the nuclear spin after the excitation. I have.

The gantry section is combined with a patient table 6 having a movable top board. By moving the movable top board, the examination site of the subject 1 lying on the patient table 6 can be checked. It can be located at the center of the magnet 2. The high-frequency coil 5 can be mounted on the subject 5 in advance, as well as a high-frequency coil (not shown) having an appropriate shape according to the purpose of examination such as mammography, in addition to the high-frequency coil 5 previously incorporated in the apparatus.

On the other hand, the control unit includes gradient magnetic field power supplies 7, 8, and 9 for driving the respective gradient magnetic field coils 3, a high frequency circuit 10 for driving the high frequency coil 4, and an amplifying NMR signal detected by the high frequency coil 5. It comprises a receiving circuit 11 for processing and a computer 12 for controlling these circuit units and for performing arithmetic processing on NMR signals. The computer 12 is connected with a monitor 13 for displaying the calculation result and a console 14 for making necessary inputs to the computer.

Further, the high-frequency circuit 10 is, for example, shown in FIG.
As shown in the figure, a frequency generator 21 for generating a signal of a reference frequency ω0, and a predetermined frequency (ω
1-ω0) or a local generator 22 for transmitting a signal of a frequency (ω2-ω0), a gate circuit (low-pass filter) 23 for passing a signal of a predetermined frequency band, and a signal from the gate circuit as a sinc function And a high-frequency power amplifier 25 for modulating with a signal of a predetermined waveform such as The local generator 22 includes a waveform table 26, a D / A converter 27, and a low-pass filter 28 as shown in FIG. 2B, and reads out data at a predetermined timing from the sine wave data table 26, for example. This is D / A converted, and high-frequency components are removed by the low-pass filter 28, whereby a signal of a predetermined frequency can be generated. The timing at which this data is read can be controlled by the computer 12, and a signal of a desired frequency can be generated by changing this timing.

The signal of the reference frequency ω0 generated by the frequency generator 21 is directly input to the frequency modulator 24 via the gate circuit 23 when the signal from the local generator 22 is not input. Here, for example, the signal is modulated by a signal having a predetermined waveform of a sinc function, amplified by the power amplifier 25, and applied to the high frequency coil 4. As a result, a high-frequency magnetic field having a center frequency ω0 and a bandwidth (± ω) is applied to the subject 1.

Further, the frequency (ω 1 −ω
When the signal of (0) is added, a signal having a frequency ω1 is obtained by passing the signal through the gate circuit 23, and a high-frequency magnetic field having this frequency as a center frequency is applied to the subject 1. Similarly, when a signal of frequency (ω2−ω0) is added from the local generator 22, a signal of frequency ω2 is obtained.

FIG. 3 is a diagram showing another embodiment of the high-frequency circuit. This high-frequency circuit 10 'includes a first frequency generator 31 for generating a signal having a frequency ω1, and a first frequency generator 31 for generating a signal having a frequency ω1. A first modulator 33 that modulates the signal with a predetermined waveform, for example, a signal of a sinc function, a second frequency generator 32 that generates a signal of frequency ω2, and a signal from the second frequency generator 32 To a predetermined waveform, for example, sinc
A second modulator 34 for modulating the signal with the function, a synthesizer 35 for synthesizing the modulated signal, and a high-frequency power amplifier 36
It is composed of These modulators can employ amplitude modulation, frequency phase modulation, or pulse modulation of a signal.

In the high frequency circuit 10 ′, a signal obtained by combining the signal of the frequency ω 1 and the signal of the frequency ω 2 is amplified by the high frequency power amplifier 36 and applied to the high frequency coil 4. Thus, a high-frequency magnetic field having two frequency components ω1 and ω2 as a carrier can be applied to the subject 1. Also, only the signal from one modulator (33 or 34) is
To the signal of the frequency ω1 or the frequency ω
2 can be applied to the high-frequency coil 4.

Such a high-frequency circuit 10 'may be provided separately from the high-frequency circuit 10 for generating a high-frequency magnetic field whose center frequency is the reference frequency ω0, or may be provided at the reference frequency ω0.
It is also possible to adopt a configuration in which one of the modulated signal having the above and the signal from the combiner 35 is switched and input to the high frequency power amplifier 36.

Next, an embodiment in which the MRI method according to the present invention using such an MRI apparatus is applied to the examination of mammography of the subject 1 will be described.

First, the subject 1 is placed on the patient table,
The moving top is moved so that the breast portion of the subject 1 is brought into the center of the magnet 2. In this case, the subject 1 may be wearing a high-frequency coil dedicated to the breast in a prone state. Here, a pulse sequence based on a normal spin echo method is executed to photograph a cross section orthogonal to the body axis of the subject 1. As shown in FIG. 4A, the resulting image 41 has a high brightness of the fat tissue 42 and the silicone insert 43. This image 41 is displayed on the monitor 13.

Next, the resonance frequency ω1 of the NMR signal obtained from fat and the N obtained from the silicone compound (insert)
The resonance frequency ω2 of the MR signal is obtained. Therefore, a high-frequency pulse train of 90 ° -τ-180 ° is applied in a state where a gradient magnetic field (z-axis) for selecting the same cross section as above is applied,
Excitation of all hydrogen nuclear spins in the cross section. NMR as spin echo τ hours after 180 ° high frequency pulse
A signal appears. This NMR signal is converted into a gradient magnetic field (x-axis and y-axis).
(Axis) is not applied, and this is Fourier-transformed by the computer 12, thereby obtaining the NMR spectrum of the cross section.

As shown in FIG. 4B, the spectrum 44 has a relatively broad peak 45 indicating a signal from a proton of tissue water and peaks 46 and 47 indicating a signal from a fat and a signal from a silicone compound. have. By calculating the deviation (kHz) of each of the peaks 46 and 47 from the peak 45, each resonance frequency ω1, ω2
Can be requested. In the illustrated MRI apparatus, NM
The R spectrum 44 is displayed on the monitor 13, and a calculation program is incorporated in the calculator 12 so that a cursor 48 is positioned on one peak to calculate a resonance frequency of the peak. Here, the resonance frequency ω1 (deviation 220) of the NMR signal obtained from fat and the NM obtained from the silicone compound which is an insert at the inspection site are shown.
The resonance frequency ω2 (deviation 320) of the R signal is read.

Next, using the frequencies ω1 and ω2 obtained in this manner, an imaging sequence incorporating a preparation pulse for suppressing signals from fat and silicone is started. Therefore, the operator inputs the frequencies of ω1 and ω2 from the console 14 and sets the sequence.

FIG. 5 shows an example of this sequence. FIG.
In the period A, a high-frequency pulse 51 having a frequency ω1 is generated. The high-frequency pulse 51 is modulated into a Gaussian waveform with an application time of 5 milliseconds in order to uniformly excite fat tissue relatively broadly distributed. As a result, only the hydrogen nuclear spins of the fat tissue at the examination site are selectively excited, and the longitudinal magnetization disappears. In the next period B, the frequency ω2
Of the high frequency pulse 52 is generated. The high-frequency pulse 52 is modulated into a Gaussian waveform with an application time of 10 milliseconds to saturate a relatively sharp peak of the silicone compound. As a result, only the hydrogen nuclear spins of the silicone compound embedded in the inspection site are selectively excited, and the longitudinal magnetization disappears.

After a waiting time (period C) of 3 milliseconds, a normal photographing sequence is executed. The imaging sequence includes spin echo, gradient echo, EPI
A known sequence such as a method can be performed, but in the illustrated example, a sequence of the spin echo method follows. That is, in the period D, the state where the first gradient magnetic field 53 is applied becomes 9
A high-frequency pulse 54 of 0 ° is applied. In this step, the nuclear spin on the specific slice plane of the inspection site falls by 90 °.
In the next period E, the second gradient magnetic field 55 is applied in a pulse shape. Thereby, the precession of the nuclear spins excited in the period D changes its phase along the axis of the second gradient magnetic field. In the next period F, a high-frequency pulse 57 of 180 ° is applied with the first gradient magnetic field 56 applied. As a result, the nuclear spin precession is inverted and becomes a spin echo signal again.

The high-frequency pulses 54 and 57 applied in this imaging sequence are high-frequency magnetic fields in a frequency band including the frequency component ω1 and the frequency component ω2. Since the longitudinal magnetization is in an extinguished state, in the obtained spin echo signal, the signal from these hydrogen nuclear spins is greatly suppressed, and the signal from the tissue water becomes dominant.

Such an echo signal 59 is detected during a period G while applying the third gradient magnetic field 58. Detection is 2
56 points or 512 points of discrete data are sampled and written to the memory of the computer 12. After the waiting time of the period H, the steps from the period A to the period G are repeated again. At this time, the amplitude of the second gradient magnetic field 55 applied in the period E is changed. This change usually has 256 steps, and is changed by 25 steps so as to have a different amplitude for each repetition.
Repeated six times. As a result, 256 × 256 (or 256 × 512) matrix data is obtained. By performing a two-dimensional Fourier transform on this data, a two-dimensional distribution image having the direction of the second gradient magnetic field and the direction of the third gradient magnetic field as the vertical axis and the horizontal axis is obtained.

In the obtained two-dimensional distribution image, signals from fat and silicone unnecessary for diagnosis are effectively suppressed by the preparation pulses 51 and 52, respectively, so that a two-dimensional distribution image having high diagnostic value can be obtained. it can.

In this embodiment, the high-frequency pulse 51 for fat suppression is applied first, and then the high-frequency pulse 52 for silicone suppression is applied. However, the order of application is not limited to this. . However, it is preferable to suppress the spin with the shorter relaxation time first.

In this embodiment, the case has been described in which the sequence according to the present invention is activated after a tomographic image has been obtained in advance by an ordinary imaging sequence such as a spin echo method, but such a preceding imaging sequence may be omitted. It is possible.

Next, a pulse sequence of another embodiment of the MRI method of the present invention will be described with reference to FIG. In this embodiment, the incorporation of the preparation pulse and the execution of the normal imaging sequence after the preparation pulse are the same, except that the preparation pulse 61 for simultaneously exciting both the signal from fat and the signal from the silicone compound is used. Used.

That is, in the period A, the high-frequency pulse 61 is applied as a preparation pulse. This high frequency pulse 61
Is composed of two signals, a frequency component ω1 and a frequency component ω2, and can be generated by the high frequency circuit 10 ′ shown in FIG. That is, the signal of the frequency ω 1 from the first modulator 33 and the signal of the frequency ω 2 from the second modulator 34 are combined by the combiner 35, amplified by the high frequency power amplifier 36, and applied to the high frequency coil 4. I do. As a result, a high-frequency magnetic field 61 having two frequency components ω1 and ω2 is applied to the subject 1 as a carrier. By applying such a high-frequency pulse 61, nuclear spins having resonance frequencies of the frequency ω1 and the frequency ω2 are excited by saturation. Here, the nuclear spin of the adipose tissue and the nuclear spin of the silicone compound are saturated and excited.

The subsequent steps are followed by the same photographing pulse sequence as in the embodiment of FIG. That is, the 90 ° high-frequency magnetic field 63 and the 180 ° high-frequency magnetic field 6 that excite the hydrogen nuclear spins
As 6, a known imaging sequence such as a spin echo method, a gradient echo method, or an EPI method is performed using a frequency band including the frequency component ω1 and the frequency component ω2. FIG. 6 also shows the spin echo method as in the embodiment of FIG. 5, and the first to third gradient magnetic fields are completely the same, so that the description is omitted, but also in this case, prior to the imaging sequence. Since the longitudinal magnetization of the adipose tissue and the nuclear spin of the silicone compound are saturated in advance, it is possible to obtain an image of high diagnostic value in which signals that hinder the diagnosis are suppressed.

In the above embodiments, the case where the present invention is applied to mammography has been described. However, the method and the apparatus of the present invention use an artificial object having a nuclear spin having a resonance frequency different from the target nuclear spin in addition to fat. The same can be applied to the measurement for the implanted subject.

[0041]

As described above, according to the present invention,
Since not only fat but also the nuclear spins of artificial materials such as silicone inserts can be saturated, the signal from the nuclear spins of tissues that exhibit these high signal intensities and reduce the density resolution of surrounding tissues is suppressed, and the density resolution is reduced. High images can be taken.

[Brief description of the drawings]

FIG. 1 is a block diagram of the overall configuration of an MRI apparatus according to the present invention.

FIGS. 2A and 2B are diagrams showing an embodiment of a high-frequency circuit according to the present invention, wherein FIG. 2A is a block diagram of the high-frequency circuit, and FIG.

FIG. 3 is a block diagram showing another embodiment of the high-frequency circuit according to the present invention.

4A and 4B are diagrams for explaining a breast examination, wherein FIG. 4A is an image of the breast and FIG.

FIG. 5 is a timing chart showing an embodiment of a photographing sequence according to the present invention.

FIG. 6 is a timing chart showing another embodiment of the photographing sequence according to the present invention.

[Explanation of symbols]

 1 ... subject 2 ... magnet device 3 ... gradient magnetic field coil 4, 5 ... high frequency coil 7-9 ... gradient Magnetic field (GC) power supply 10, 10 '... high frequency circuit 11 ... reception circuit 12 ... computer (arithmetic processing means) 51 ... first high frequency Magnetic field 52: Second high-frequency magnetic field 54: Third high-frequency magnetic field

Claims (6)

[Claims] 1. A magnetic resonance imaging method for generating a tomographic image of an examination part by causing a nuclear magnetic resonance phenomenon in an examination part of a subject, wherein: a) disposing the examination part in a static magnetic field space; A) applying a first high-frequency magnetic field having a frequency ω1 to the inspection site; c) applying a second high-frequency magnetic field having a frequency ω2 (ω21ω1) to the inspection site; Using a third high-frequency magnetic field having a frequency band including a frequency ω1 and a frequency ω2 to drive a pulse sequence for measuring a nuclear magnetic resonance signal from the examination site. 2. A magnetic resonance imaging method for producing a tomographic image of an examination part by causing a nuclear magnetic resonance phenomenon in an examination part of a subject, wherein: a) disposing the examination part in a static magnetic field space; A) applying a high-frequency magnetic field that excites a predetermined nuclear spin of the examination site; c) measuring a nuclear magnetic resonance signal from the nuclear spin; d) obtaining a frequency spectrum from the nuclear magnetic resonance signal;
Determining at least two different resonance frequencies ω1, ω2; e) applying a first high-frequency magnetic field having a frequency ω1 to the inspection site; f) applying a second high-frequency magnetic field having a frequency ω2 to the inspection site. And g) driving a pulse sequence for measuring a nuclear magnetic resonance signal from the examination site using a third high-frequency magnetic field having a frequency band including a frequency ω1 and a frequency ω2 at the examination site. A magnetic resonance imaging method. 3. A magnetic resonance imaging method for generating a tomographic image of an examination part by causing a nuclear magnetic resonance phenomenon in an examination part of a subject, wherein: a) disposing the examination part in a static magnetic field space; b. Applying a high-frequency magnetic field that substantially simultaneously saturates the nuclear spins of the tissue having at least two different resonance frequencies ω1 and ω2 among the nuclear spins of the examination site;
And c) driving a pulse sequence for measuring a nuclear magnetic resonance signal from the examination site using a third high-frequency magnetic field having a frequency band including a frequency ω1 and a frequency ω2 at the examination site. Magnetic resonance imaging method. 4. A magnetic resonance imaging method for obtaining a tomographic image of an examination part by causing a nuclear magnetic resonance phenomenon in an examination part of a subject, wherein: a) disposing the examination part in a static magnetic field space; A) applying a high-frequency magnetic field that excites a predetermined nuclear spin of the examination site; c) measuring a nuclear magnetic resonance signal from the nuclear spin; d) obtaining a frequency spectrum from the nuclear magnetic resonance signal;
Determining at least two different resonance frequencies ω1, ω2; e) applying a high frequency magnetic field that substantially simultaneously saturates the nuclear spins of the tissue having at least two different resonance frequencies ω1, ω2 among the nuclear spins of the examination site. F) applying a high-frequency magnetic field that substantially simultaneously saturates the nuclear spins of the tissue having at least two different resonance frequencies ω1, ω2 among the nuclear spins of the examination site;
And g) driving a pulse sequence for measuring a nuclear magnetic resonance signal from the examination site using a third high-frequency magnetic field having a frequency band including a frequency ω1 and a frequency ω2 at the examination site. Magnetic resonance imaging method. 5. A static magnetic field generating means for generating a uniform static magnetic field in a space in which a subject is disposed, a gradient magnetic field generating means for generating a magnetic field having a magnetic field intensity different according to a position in said space, Means for generating a high-frequency magnetic field for resonantly exciting nuclear spins, means for detecting a nuclear magnetic resonance signal of the nuclear spins, and means for arithmetically processing the detected signals and displaying the result In the imaging apparatus, the means for generating a high-frequency magnetic field includes a means for generating a plurality of high-frequency magnetic fields so as to selectively excite nuclear spins of at least two specific tissues of the subject. Imaging device. 6. The means for generating a high-frequency magnetic field includes a first high-frequency magnetic field having a frequency ω1, a second high-frequency magnetic field having a frequency ω2 (ω2 ≠ ω1), and a frequency ω1 and a second high-frequency magnetic field having a frequency ω1 under the control of the arithmetic processing means. 6. The magnetic resonance imaging apparatus according to claim 5, further comprising means for generating a third high-frequency magnetic field having a frequency band including ω2.