JP7151996B2 - camera - Google Patents

Description

TECHNICAL FIELD The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus capable of imaging Magnetic Resonance Elastography (MRE) for measuring tissue hardness.

In the medical field, an MRI apparatus (Magnetic Resonance Imaging apparatus: Magnetic Resonance Imaging apparatus) is used, which has little effect on patients such as radiation exposure. In the MRI system, the hydrogen nuclei (protons) contained in each cell of the human body are excited by applying a high-frequency magnetic field corresponding to the spin of the protons, and the excited protons return to their original state (relaxation). Based on the electromagnetic waves, it is possible to obtain images in which areas with different proton densities (eg, water and fat) are shaded.
MRE (Magnetic Resonance Elastography) uses an MRI device to image the object while applying vibration (approximately 50 Hz to 100 Hz in the case of the trunk) to determine the "hardness" inside the object. This is an imaging method that utilizes the difference in vibration wave propagation due to the difference in the hardness to image the hardness (see Patent Documents 1 and 2).

In general, lesions become harder as the degree of malignancy increases, and "palpation" has long been practiced for diagnosing the degree of malignancy. Although palpation is a simple and effective diagnostic method, it is difficult to palpate deep parts of the body or parts surrounded by bones. In MRE, forcible vibration is generated on the surface of the human body, and differences in local hardness are imaged from how the vibration wave propagates through the body. As a result, MRE can measure the hardness of parts that have been difficult to palpate, and may provide images with completely different diagnostic value than before.
When the hardness of an object changes, the sound velocity and wavelength of the waves propagating inside it (propagating waves) change. Therefore, in MRE, an imaging target is imaged while applying vibrations in synchronization with the MRI apparatus (see Non-Patent Document 1). This makes it possible to visualize propagating waves inside the object to be imaged. The image of propagating waves obtained at this time is called a wave image. Since the wave image is an image of the wavelength of the local propagating wave, it is possible to calculate an image that reflects the local stiffness. An image obtained by calculation is called an elastogram.

In order to display the propagation of vibration, it is easier to express it as a moving image instead of a still image. Here, with devices for taking moving pictures such as general video cameras, moving pictures are taken by taking still pictures at a speed of about 1/30 second. It cannot capture images at high speed like a camera. Therefore, in MRE, in order to obtain a wave image of how vibration is transmitted, the MRI and vibration are synchronized and "frame-by-frame" images are taken a plurality of times. In the MRE, currently used equipment divides one cycle of vibration into four times (shifting the phase of vibration by π/2) and performs “frame-by-frame photography”. Therefore, a series of about four "frame-by-frame" shots are required to perform MRE.

Japanese Patent Application Publication No. 2005-507691 (“0008”, “0014” to “0023”) JP 2011-98158 A (“0003” to “0018”, “0026” to “0029”)

Muthupillai R, Lomas DJ, Rossman PJ, Greenleaf JF, Manduca A, Ehman RL, Magnetic resonance elastography by direct visualization of propagating acoustic strain waves. Science 1995;269(5232):1854-7

(Problem of conventional technology)
In the case of MRE imaging, when the vibration phase is shifted four times and the imaging target moves (for example, breathing) in each "frame-by-frame" shooting, the position of the image shifts and an error occurs. may cause Therefore, imaging with low spatial resolution (large pixel size, rough image) is forced to achieve four “frame-by-frame” shots with one breath-hold (approximately 20 seconds or less). In general, in both MRI and MRE, imaging with high spatial resolution (small pixel size, fine image) requires a longer imaging time than imaging with low spatial resolution (pixel size). will need to hold their breath for a long time. Therefore, holding the breath for a long time increases the burden on the subject, and in reality, it is difficult to hold the breath for a long time. There is a problem.

A technical object of the present invention is to shorten the imaging time of an MR image as compared with the conventional configuration.

In order to solve the technical problem, the photographing device of the invention described in claim 1,
a magnetic field generating device for generating a static magnetic field, a gradient magnetic field whose magnetic field changes according to the position, and an alternating magnetic field preset based on the magnetic resonance conditions of protons in the examination area of the subject;
an alternating magnetic field applying means for applying the alternating magnetic field with a preset repetition time interval;
receiving means for receiving the electromagnetic wave based on an echo time, which is the time for receiving the electromagnetic wave emitted when the protons in the inspected portion excited by the alternating magnetic field relax;
a vibration imparting member that imparts vibration to a portion to be inspected, the vibration imparting member being capable of imparting a plurality of vibrations having different phases;
Gradient magnetic field applying means for controlling the magnetic field generating device to apply the gradient magnetic field for MRE from a preset direction to the part to be inspected, wherein the a means for applying the gradient magnetic field for applying the gradient magnetic field;
MR corresponding to the phase of the electromagnetic wave signal based on the electromagnetic wave acquired according to the echo time corresponding to the time of applying the gradient magnetic field, based on the difference between two electromagnetic wave signals whose acquisition times are adjacent. MR phase image acquisition means for acquiring a phase image;
characterized by comprising

The invention according to claim 2 is the imaging device according to claim 1,
the vibration imparting member imparting superimposed vibration obtained by superimposing vibration of a predetermined first frequency and vibration of a second frequency different from the first frequency to the inspected portion;
One period of the first frequency is divided by a first number of vibration phase decompositions, and one period of the second frequency is divided by a second number of vibration phase divisions different from the first number of vibration phase decompositions. a gradient magnetic field applying means for applying the gradient magnetic field at a time;
The MR that acquires an MR phase image corresponding to the vibration of the first frequency and an MR phase image corresponding to the vibration of the second frequency based on the difference between two electromagnetic signals whose acquisition timings of the electromagnetic wave signals are adjacent to each other. phase image acquisition means;
characterized by comprising

According to the first aspect of the present invention, MR phase images of a plurality of vibration phases can be acquired in one observation, and the imaging time of MR images can be shortened compared to the conventional configuration.
According to the second aspect of the invention, MR phase images for vibrations of a plurality of frequencies can be acquired in one observation, and the imaging time of MR images can be shortened compared to the conventional configuration. .

FIG. 1 is an explanatory diagram of a magnetic resonance imaging apparatus according to Embodiment 1 of the present invention. FIG. 2 is a functional block diagram of a computer main body in the magnetic resonance imaging apparatus of Example 1. FIG. FIG. 3 is an explanatory diagram of application of a magnetic field and application of vibration in Example 1, and is a graph in which the horizontal axis represents time. FIG. 4 is an explanatory diagram of processing for creating an MR image according to the first embodiment. FIG. 5 is an explanatory diagram of the relationship between vibration and gradient magnetic field in a conventional MRE, FIG. 5A is an explanatory diagram when the vibration phase is 0°, FIG. 5B is an explanatory diagram when the vibration phase is 90°, and FIG. 5C. is an explanatory diagram when the vibration phase is 180°, and FIG. 5D is an explanatory diagram when the vibration phase is 360°. 6A and 6B are explanatory diagrams of an example of imaging results, FIG. 6A is an explanatory diagram of imaging results by the conventional imaging method, and FIG. 6B is an explanatory diagram of imaging results by the imaging method of the first embodiment. 7A and 7B are explanatory diagrams of an example of photographing results of the shoulder portion of a person, FIG. 7A is an explanatory diagram of photographing results by the conventional photographing method, and FIG. FIG. 8 is an explanatory diagram of the process of creating an MR image according to the second embodiment, and corresponds to FIG. 4 of the first embodiment. 9A and 9B are explanatory diagrams of an example of imaging results, FIG. 9A is an explanatory diagram of imaging results by the conventional imaging method, and FIG. 9B is an explanatory diagram of imaging results by the imaging method of the second embodiment. FIG. 10 is an explanatory diagram of a modification.

Next, specific examples of embodiments of the present invention (hereinafter referred to as examples) will be described with reference to the drawings, but the present invention is not limited to the following examples.
It should be noted that in the following explanation using the drawings, illustration of members other than those necessary for the explanation is omitted as appropriate for ease of understanding.

FIG. 1 is an explanatory diagram of a magnetic resonance imaging apparatus according to Embodiment 1 of the present invention.
In FIG. 1, a magnetic resonance imaging apparatus 1 of Embodiment 1 as an example of an imaging apparatus of the present invention has a magnet unit 2 as an example of a magnetic field generation device. A through hole 3 is formed in the magnet portion 2 so as to extend through the magnet portion 2 in the horizontal direction. A bed 6 on which a lying subject 4 is supported can pass through the through hole 3 .
The magnet section 2 has a static magnetic field generating magnet 11 as an example of a static magnetic field applying member. A superconducting electromagnet or a permanent magnet can be used as the static magnetic field generating magnet. A gradient magnetic field generating coil 12 as an example of a gradient magnetic field applying member is arranged inside the static magnetic field generating magnet 11 . A high-frequency magnetic field generating coil 13 as an example of an excitation magnetic field applying member is arranged inside the gradient magnetic field generating coil 12 . A receiving coil 14 for receiving electromagnetic waves is arranged inside the high-frequency magnetic field generating coil 13 as an example of a receiving section.

Further, in Example 1, for MRE measurement, the subject 4 has a diaphragm (passive driver) as an example of a vibration imparting member on a portion of the body surface corresponding to the position of the liver as an example of a portion to be inspected. ) 16 are supported. The diaphragm 16 is a member that applies vibrations to the subject 4 at a preset frequency, and may have any conventionally known configuration described in Patent Document 2 or the like, for example.

A computer device 21 as an example of an information processing device is electrically connected to the magnet portion 2 via a cable Cb. Therefore, the computer device 21 is configured to be able to transmit and receive control signals for the static magnetic field generating magnets 11 and the like, detection signals for the receiving coils 14 and the like to and from the magnet unit 2 . The computer device 21 has a computer main body 22, a display 23 as an example of a display section, and a keyboard 24 and a mouse 25 as examples of an input section. In the first embodiment, the configuration in which the computer device 21 and the magnet unit 2 are connected by the cable Cb was exemplified. It is also possible to transmit and receive information using a communication method.

(Description of the control unit of the computer main body 22 of the first embodiment)
FIG. 2 is a functional block diagram of a computer main body in the magnetic resonance imaging apparatus of Example 1. FIG.
In FIG. 2, the controller 41 of the computer main body 22 of the first embodiment includes an I/O (input/output interface) for inputting/outputting signals with the outside, adjusting input/output signal levels, etc., and performing necessary startup processing. ROM (read-only memory) that stores programs and data, etc., RAM (random access memory) for temporarily storing necessary data and programs, and performs processing according to the start-up program stored in ROM, etc. It is composed of a computer device having a CPU (Central Processing Unit) and a clock oscillator, etc. Various functions can be realized by executing programs stored in the ROM and RAM.
The control unit 41 stores basic software for controlling basic operations, a so-called operating system OS, an imaging device control program AP1 as an example of an application program, and other software (not shown).

(Elements connected to the control unit 41 of the first embodiment)
Output signals from signal output elements such as the keyboard 24 , the mouse 25 and the receiving coil 14 are input to the control unit 41 .
Further, the control unit 41 of the first embodiment outputs control signals to controlled elements such as the display 23, the static magnetic field generating magnet 11, the gradient magnetic field generating coil 12, the high frequency magnetic field generating coil 13, and the like.

(Function of control unit 41)
The photographing device control program AP1 of the control unit 41 of the first embodiment has the following functional units (program modules) 51-58.

The magnetic field control means 51 controls the magnet unit 2 to control the magnetic field for performing MR imaging of the examined part of the subject 4 . The magnetic field control means 51 of the first embodiment includes a repetition time storage means 51a, an echo time storage means 51b, a static magnetic field application means 51c, a gradient magnetic field application means 51d, and a high frequency magnetic field application means as an example of an alternating magnetic field application means. and means 51e.

FIG. 3 is an explanatory diagram of application of a magnetic field and application of vibration in Example 1, and is a graph in which the horizontal axis represents time.
The repetition time storage means 51a stores a repetition time TR, which is an interval of application of a high-frequency magnetic field as an example of an alternating magnetic field applied to excite protons contained in a part of the subject 4 to be examined.

The echo time storage means 51b stores an echo time TE, which is the interval from the application of the high-frequency magnetic field to the acquisition of the electromagnetic waves emitted when the excited protons return (relax) to their original state. In FIG. 3, in Example 1, the echo time storage means 51b stores the echo time TE, which is the period from the application of the high-frequency magnetic field to the acquisition of the electromagnetic waves. In Example 1, the echo time TE is set at vibration phases of 0°, 90°, 180°, 270°, 360° (=0°), and 450° (=90°) with respect to the vibration 66 applied by the diaphragm 16. °), . . . That is, the gradient magnetic field 61 is set to be applied four times (90° phase intervals) for one cycle (360°) of the oscillation 66 .
Although the repetition time TR and the echo time TE are set in advance in the first embodiment, they can be set and changed by manually inputting them by the user of the magnetic resonance imaging apparatus 1. be.

The static magnetic field applying means 51c controls the static magnetic field generating magnet 11 to generate a static magnetic field. The static magnetic field applying means 51c of Example 1 generates, for example, a static magnetic field of 3 [T].
The gradient magnetic field applying means 51d controls the gradient magnetic field generating coil 12 to generate a gradient magnetic field (gradient magnetic field) 61 for MRE whose magnetic field changes according to the position. Therefore, the gradient magnetic field 61 is a magnetic field called a vibration detection gradient magnetic field MEG (motion encoding gradient). As shown in FIG. 3, the first gradient magnetic field applying means 51d of the first embodiment applies slices in three axial directions, ie, a slice direction, a readout direction and a phase direction, which are orthogonal to each other. A gradient magnetic field 61 is generated in the direction (slice axis).
The high-frequency magnetic field applying means 51e controls the high-frequency magnetic field generating coil 13 to generate a high-frequency magnetic field 63, which is an alternating magnetic field corresponding to the frequency that excites protons.

The vibration application control means 52 controls the diaphragm 16 to apply vibration 66 to the inspected portion. In FIG. 3, the gradient magnetic field 61 is applied four times at phase intervals of 90° with respect to the period T of the vibration 66 applied by the vibration applying control means 52 of the first embodiment. In addition, in the first embodiment, the vibration imparting control means 52 is not limited to the vibration 66 shown in FIG. 3, and has a function of changing the vibration 66 of arbitrary frequency, amplitude, and phase according to the user's input.

The signal acquiring means 53, which is an example of receiving means, acquires an electromagnetic wave signal generated when the protons of the subject 4 relax via the receiving coil 14 during the echo time TE. Therefore, in Example 1, in a state in which the vibration shown in FIG. Take multiple shots.

FIG. 4 is an explanatory diagram of processing for creating an MR image according to the first embodiment.
The MR image acquisition means 54 has a signal processing means 54a, an MR intensity image creation means 54b, and an MR phase image creation means 54c. to create
The signal processing means 54a performs signal processing on the received electromagnetic wave signal. The signal processing means 54a of the first embodiment defines the signal obtained by the signal obtaining means 53 as the real part r (real part) and the signal obtained by delaying the signal obtained by the signal obtaining means 53 by π/2 as the imaginary part i ( imaginary part). That is, it generates a complex number based on the received electromagnetic wave signal, a so-called k-space (frequency space) signal in the technical field of MRI. Then, inverse Fourier transform (inverse fast Fourier transform in the embodiment) is performed on the real part r and the imaginary part i to transform them into signals R and I in the real space. Based on the real part R and the imaginary part I in the real space, the intensity M=(R ² +I ² ) ^1/2 and the phase φ=tan ⁻¹ (I/R) in the complex plane are calculated. Note that this calculation has been introduced in a conventional MRI apparatus and is publicly known, so further detailed description will be omitted.

The MR intensity image creating means 54b creates an MR intensity image based on the intensity M calculated by the signal processing means 54a. Note that the MR intensity image is an image that is generally used for diagnosis as an MRI image.

The MR phase image creating means 54c creates an MR phase image (used as a Wave Image in MRE) based on the phase φ calculated from the electromagnetic wave signal. Here, the MR phase image creating means 54c of the first embodiment creates an MR phase image based on the phase φ calculated from the electromagnetic wave signal measured at the echo time TE.
In FIG. 4, subtracting (taking the difference) the electromagnetic wave signal detected in the first gradient magnetic field (first echo) from the electromagnetic wave signal detected in the second gradient magnetic field (second echo) yields the first The echo portions cancel each other out, leaving only the electromagnetic wave signal corresponding to the second echo only, and as a result, only the measurement result of the vibration phase of 0° remains. Similarly, when the electromagnetic wave signal detected by the second echo is subtracted from the electromagnetic wave signal detected by the third echo, only the electromagnetic wave signal corresponding to only the third echo remains, and only the measurement result of the vibration phase of 90° remains. . Similarly, the difference between the fourth echo and the third echo gives the measurement result for the vibration phase of 180°, and the difference between the fifth echo and the fourth echo gives the measurement result for the vibration phase of 270°. In this manner, MR phase images are created for each of the phases of the vibration applied by the vibration application control means 52 of 0°, 90°, 180°, and 270°. Therefore, in Example 1, the acquisition times of electromagnetic wave signals (first echo, second echo, third echo, . 2 echoes, ...), an MR phase image (MRE image) corresponding to the phase of the electromagnetic wave signal is acquired (created).

The wavelength acquiring means 55 acquires the wavelength λ of the vibration wave propagating inside the subject 4 due to the vibration applied by the diaphragm 16 . The wavelength acquisition unit 55 of the first embodiment obtains the phase φ Obtain the wavelength λ of the vibration wave from the transition of . Specifically, the wavelength λ of the vibration wave is estimated for each local region of the image from the state of propagation of the vibration wave obtained from images with vibration phases of 0°, 90°, 180°, and 270°.

The hardness estimating means 56 estimates the hardness μ of the portion to be inspected based on the wavelength λ of the vibration wave, the frequency f of the vibration wave imparted by the diaphragm 16, and the density ρ of the portion to be inspected. . The frequency f of the vibration wave is known from the frequency f of the vibration wave imparted by the diaphragm 16, and the density ρ of the inspected portion is approximately 1 [g/cm ³ ], which is the density of the human body. The hardness (elastic modulus) μ is calculated from μ=ρ·(λ·f) ² .
The MRE image creating means 57 creates an MRElastogram image (MRE image) in which hardness is imaged using the MR phenomenon. The MRE image creating means 57 of the first embodiment creates an MRE image that is color-coded according to the hardness μ calculated for each local region (pixel). As an example, a hard portion (pixel with a large hardness μ value) is displayed in red, and as it becomes softer (a pixel with a smaller hardness μ value), the display changes to yellow, green, blue, and purple. It is possible.

The image display means 58 displays the images created by the MR image acquisition means 54 and the MRE image creation means 57 on the display 23 . That is, the display 23 displays an MR intensity image (an image used for normal diagnosis), an MR phase image (used as a wave image in MRE), and an elastogram image (MRE image), which are cross-sectional images of the examination site. be. In addition, in Example 1, it is difficult to understand the anatomical structure only with the Wave Image image and the Elastogram image, so it is possible to provide a display mode in which the MR intensity image and the Wave Image image and the Elastogram image are displayed in an overlapping manner. be. In addition, it is also possible to display the images in an overlapping manner, or not to display all the images on the display 23, but to switch and display the MR intensity image, the Wave Image image, or the Elastogram image according to the input. Also, it is possible to arrange the MR intensity image and the Elastogram image side by side in the same cross section, or to display the Elastogram images in different cross sections side by side.

(Action of Example 1)
FIG. 5 is an explanatory diagram of the relationship between vibration and gradient magnetic field in a conventional MRE, FIG. 5A is an explanatory diagram when the vibration phase is 0°, FIG. 5B is an explanatory diagram when the vibration phase is 90°, and FIG. 5C. is an explanatory diagram when the vibration phase is 180°, and FIG. 5D is an explanatory diagram when the vibration phase is 360°.
In the magnetic resonance imaging apparatus 1 of Example 1 having the above configuration, a gradient magnetic field is applied four times in one period of the vibration 66, and from the detected electromagnetic wave signals, 0°, 90°, 180°, and 270° An MR phase image for each vibration phase can be acquired.
As shown in FIG. 5, in the conventional MRE, a gradient magnetic field 02 having a period 02a synchronized with the period 01a of the vibration 01 is applied. Then, as shown in FIG. 5A, the first measurement is performed by applying the gradient magnetic field 02 when the phase shift is 0° (the vibration phase is 0°), and the second measurement is performed when the vibration phase is 90°. is 180° for the third measurement, and the vibration phase is 270° for the fourth measurement.

On the other hand, in Example 1, MR phase images of each vibration phase of 0°, 90°, 180°, and 270° can be acquired by one measurement. Therefore, the imaging time can be shortened to 1/4 compared with the conventional MRE measurement. Therefore, the period during which breathing is stopped and the period during which vibrations 66 are received from the diaphragm 16 can be shortened, and the burden and pain on the subject (patient) can be reduced.
In addition, although the imaging time can be shortened in the first embodiment, the spatial resolution can be made higher than that of the prior art if the imaging time is the same. Therefore, highly accurate observation and imaging are possible, contributing to diagnosis by doctors.

In addition, as compared with the conventional case of four imaging operations, only one imaging operation is required, so errors due to movement of the imaging target (breathing, body movement, etc.) can be reduced. Therefore, it is possible to reduce elastic modulus calculation errors due to errors.
Furthermore, since the imaging time is shortened, it becomes possible to image more cross-sections in the same time, and to calculate the elastic modulus from a plurality of cross-sections.

6A and 6B are explanatory diagrams of an example of imaging results, FIG. 6A is an explanatory diagram of imaging results by the conventional imaging method, and FIG. 6B is an explanatory diagram of imaging results by the imaging method of the first embodiment.
A conventional imaging method in which one set of imaging is performed four times is compared with the imaging method in which four vibration phases are imaged in one time according to the first embodiment. Two sets each of the conventional imaging method and the imaging method of Example 1 (that is, 8 times in the conventional method and 2 times in Example 1) were photographed, and the photographed results were averaged.
There was almost no difference between the result of the conventional imaging method shown in FIG. 6A and the result of the imaging method of Example 1 shown in FIG. 6B. That is, it was confirmed that even with the imaging method of Example 1, imaging was possible at the same level as with the conventional imaging method.

7A and 7B are explanatory diagrams of an example of photographing results of the shoulder portion of a person, FIG. 7A is an explanatory diagram of photographing results by the conventional photographing method, and FIG.
7 was also photographed in the same manner as in FIG. As shown in FIGS. 7A and 7B, it was confirmed that Example 1 (FIG. 7B) also provided imaging results of the same level as the conventional one (FIG. 7A).

FIG. 8 is an explanatory diagram of the process of creating an MR image according to the second embodiment, and corresponds to FIG. 4 of the first embodiment.
Next, Embodiment 2 of the present invention will be described. In the description of Embodiment 2, components corresponding to those of Embodiment 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. do.
Although the second embodiment is different from the first embodiment in the following points, it is constructed in the same manner as the first embodiment in other respects.

In FIG. 8, in the magnetic resonance imaging apparatus 1 of the second embodiment, the vibration applying control means 52 controls the diaphragm 16 to vibrate at the first frequency 66a (see the solid line in FIG. 8) and vibrate at the second frequency. 66b (see the dashed line in FIG. 8) and superimposed vibration are applied. In FIG. 8, the two vibrations 66a and 66b are shown separately for easy understanding. generate. As an example, 75 Hz can be set as the first frequency and 100 Hz can be set as the second frequency.

The gradient magnetic field applying means 51d of Example 2 divides one cycle of the first frequency (75 Hz) into four times (90° intervals) as an example of the number of times of first vibration phase decomposition, and 1 of the second frequency The gradient magnetic field 61 is applied at the time when the period is divided into three times (120° intervals) as an example of the number of second vibration phase divisions. Therefore, the gradient magnetic field 61 is applied four times in one cycle to the vibration 66a of the first frequency, and the gradient magnetic field 61 is applied three times in one cycle to the vibration 66b of the second frequency. will be applied.

The MR phase image creating means 54c of the second embodiment creates an MR phase image corresponding to the vibration of the first frequency and an MR phase image corresponding to the vibration of the second frequency based on the difference between the two electromagnetic wave signals whose acquisition times are adjacent to each other. Acquire corresponding MR phase images. A specific description will be given using FIG.
First, with respect to the vibration 66a of the first frequency, the result of the vibration phase of 0° is indicated as "a", the result of the vibration phase of 90° is indicated by "b", the result of 180° is indicated by "c", and the result of 270° The result of is denoted as "d". Similarly, for the vibration 66b of the second frequency, the result with a vibration phase of 0° is denoted as "a'", the result with a vibration phase of 120° as "b'", and the result with a vibration phase of 240° as "c'". ”.

In FIG. 8, for example, when the electromagnetic wave signal of the fifth echo is subtracted from the electromagnetic wave signal of the sixth echo (obtaining the difference), the vibration phase of the vibration 66a of the first frequency is 0° and the vibration of the vibration 66b of the second frequency is A result obtained by adding a phase of 120° is obtained. That is, "a+b'" is obtained. Then, the difference between the third echo and the second echo is "bb'". Similarly, "-ba'" is obtained from the difference between the fifth echo and the fourth echo, and "a+a'" is obtained from the difference between the second echo and the first echo. Then, by adding "a+b'" and "bb'", "a+b" is obtained, and by adding "-ba'" and "a+a'", "ab" is obtained. can get. Furthermore, "a" is obtained by adding "a+b" and "ab" and dividing by 2, and "b" is obtained by subtracting and dividing by 2. Similarly, an MR phase image of each phase of each vibration 66a, 66b is obtained.

(Action of Example 2)
In the magnetic resonance imaging apparatus 1 of the second embodiment having the above configuration, the gradient magnetic field is applied four times per cycle to the vibration 66a of the first frequency, and three gradient magnetic fields are applied to the vibration 66b of the second frequency in one cycle. This corresponds to application of a gradient magnetic field of . Then, from the detected electromagnetic wave signal, MR phase images of respective vibration phases of 0°, 90°, 180°, and 270° are acquired with respect to the vibration 66a of the first frequency, and the MR phase images are acquired with respect to the vibration 66b of the second frequency. MR phase images of each vibration phase of 0°, 120°, and 240° are acquired.
In the prior art, it was necessary to measure each vibration phase, and a total of seven measurements were required, whereas in Example 2, it is possible to create an MRE image with one measurement. . Therefore, the imaging time can be significantly shortened compared to the conventional technology.

In addition, in Example 2, images of vibrations 66a and 66b with different frequencies can be easily obtained. Therefore, a portion shallow from the body surface is diagnosed from an image of high frequency vibration 66b with high spatial resolution, and a portion deep from the body surface is diagnosed from an image of low frequency vibration 66a with high penetrating power (vibration is easily propagated). It is also possible to use the That is, it is possible to perform simultaneous evaluation of tissues shallow and deep from the body surface in one measurement.
Note that two MRE images are synthesized into one image and displayed by using a low-frequency image portion for a portion deeper than a predetermined value from the body surface and using a high-frequency image portion for a shallow portion. It is also possible to

9A and 9B are explanatory diagrams of an example of imaging results, FIG. 9A is an explanatory diagram of imaging results by the conventional imaging method, and FIG. 9B is an explanatory diagram of imaging results by the imaging method of the second embodiment.
In FIGS. 9A and 9B, in the results of the MRE images for the vibrations 66a and 66b of each frequency, in Example 2, an error (image with low accuracy) was observed in the peripheral part, but almost the same in the central part. results were obtained.
The marginal portion corresponds to the vicinity of the skin in the human body, and the central portion corresponds to the deep part of the body. As for the peripheral part, it is a part that can be diagnosed by a doctor's palpation, and the need for actual diagnosis is low for the results of MRE in the vicinity of the surface. Therefore, it was confirmed that the inside of the body can be observed with sufficient precision, and that there are few practical problems as an MRE image.

(Change example)
Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the invention described in the claims. It is possible. Modified examples (H01) to (H03) of the present invention are exemplified below.
(H01) In the above-described embodiment, the magnetic resonance imaging apparatus in which the magnet portion 2 is ring-shaped, that is, a so-called tunnel type magnetic resonance imaging apparatus was exemplified, but the present invention is not limited to this. For example, the magnet unit 2 can be applied to a U-shaped magnetic resonance imaging apparatus, that is, an open-type magnetic resonance imaging apparatus.
(H02) In the above examples, the specific numerical values exemplified can be arbitrarily changed according to design, use, and the like.

FIG. 10 is an explanatory diagram of a modification.
(H03) In the second embodiment, the vibration frequency is exemplified as 4 times and 3 times as the number of times of the first phase decomposition and the number of times of the second phase decomposition, respectively, but it is not limited to this. It can be changed according to the frequency of vibration. For example, when the first frequency is 40 Hz and the second frequency is 90 Hz, by setting the number of times of the first phase decomposition to 3 times and the number of times of the second phase decomposition to 4 times, the same imaging as in the second embodiment can be performed. It becomes possible. In addition, when the frequency of vibration becomes high, the interval between echoes becomes short. Therefore, as shown in FIG. Moreover, it is also possible to configure a single measurement to measure a plurality of vibration phases.

1... photographing device,
2 ... magnetic field generator,
16... Vibration imparting member,
51d ... Gradient magnetic field applying means,
51e ... means for applying an alternating magnetic field,
53 ... Receiving means,
54c... MR phase image acquisition means,
61 ... Gradient magnetic field,
66, 66a, 66b... vibration,
66a ... vibration of the first frequency,
66b ... vibration of the second frequency,
TE: echo time,
TR: Repeat time.

Claims (2)

a magnetic field generating device for generating a static magnetic field, a gradient magnetic field whose magnetic field changes according to the position, and an alternating magnetic field preset based on the magnetic resonance conditions of protons in the examination area of the subject;
an alternating magnetic field applying means for applying the alternating magnetic field with a preset repetition time interval;
receiving means for receiving the electromagnetic wave based on an echo time, which is the time for receiving the electromagnetic wave emitted when the protons in the inspected portion excited by the alternating magnetic field relax;
a vibration imparting member that imparts vibration to a portion to be inspected, the vibration imparting member being capable of imparting a plurality of vibrations having different phases;
Gradient magnetic field applying means for controlling the magnetic field generating device to apply the gradient magnetic field for MRE from a preset direction to the part to be inspected, wherein the a means for applying the gradient magnetic field for applying the gradient magnetic field;
MR corresponding to the phase of the electromagnetic wave signal based on the electromagnetic wave acquired according to the echo time corresponding to the time of applying the gradient magnetic field, based on the difference between two electromagnetic wave signals whose acquisition times are adjacent. MR phase image acquisition means for acquiring a phase image;
A photographing device comprising: the vibration imparting member imparting superimposed vibration obtained by superimposing vibration of a predetermined first frequency and vibration of a second frequency different from the first frequency to the inspected portion;
One period of the first frequency is divided by a first number of vibration phase decompositions, and one period of the second frequency is divided by a second number of vibration phase divisions different from the first number of vibration phase decompositions. a gradient magnetic field applying means for applying the gradient magnetic field at a time;
The MR that acquires an MR phase image corresponding to the vibration of the first frequency and an MR phase image corresponding to the vibration of the second frequency based on the difference between two electromagnetic signals whose acquisition timings of the electromagnetic wave signals are adjacent to each other. phase image acquisition means;
2. The photographing device according to claim 1, comprising:

Images