JP2010227417A - Focused oscillation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such the problem that the conventional oscillation device can not be used for finding a small hardness change in an early stage since it is hard in the device to control the frequency, amplitude, and phase, etc., of oscillation to be generated, and, for example, the device is not suitable in the case of a narrow measurement object and not suitable for measuring the minute distribution of viscoelastic moduli though it is suitable for obtaining the average value of the viscoelastic moduli in the wide range area of the measurement object. <P>SOLUTION: The focused oscillation device is used for an MR imaging apparatus or a magnetic resonance microscopy apparatus in order to acquire an image for identifying viscoelasticity of a subject by NMR. The device includes: a plurality of oscillation generating parts for generating oscillation to be given to the subject; a signal generating part for giving a signal for oscillation generation to the oscillation generating parts; and vibration transmission chips which are arranged between the oscillation generating parts and the subject and directionally disposed in a focus area, so that the generated vibration can be propagated inside the subject as an elastic wave and focused in the focus area. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is a focusing type excitation device used in an MR imaging apparatus or an MRI microscope apparatus, and includes a plurality of vibrators, and vibrational elastic waves generated by the vibrators vibrate in a specific region inside a subject. The present invention relates to a focusing vibration exciter configured to focus an elastic wave.

  In the field of medicine, quantitative measurement of physical properties such as elasticity and viscosity of living tissue is considered an important index for knowing the extent of lesions and their progress, and a method for obtaining such information in a non-invasive manner has been developed. It has been. For example, the MRE (Magnetic Resonance Elastography) method. The MRE method is a method of measuring the hardness of a tissue based on an elastic wave that is transmitted to the subject from the outside and transmitted through the subject. The elasticity generated inside the subject by an external vibration device. Waves are imaged and mechanical properties such as viscoelastic modulus are qualitatively or quantitatively measured from the image.

  As an external vibration device used for an MR imaging apparatus or an MRI microscope apparatus, there is an apparatus that mechanically vibrates a table on which a subject is placed and transmits the vibration to the subject (Patent Document 1). According to the vibration apparatus, since a uniform elastic wave can be generated over a wide range, quantitative measurement over a wide range in the subject, qualitative determination, and the like are possible.

  However, since the table on which the subject is placed is vibrated, there is a problem that vibration cannot be given locally and it is difficult to downsize the apparatus. Further, since the resonance frequency of the components of the external vibration device has a complicated influence, it is impossible to control with high accuracy. Furthermore, when the subject is a human, vibrations are transmitted to the entire body, which causes discomfort.

  In addition, as a device that directly transmits vibration to a subject, a vibration device including an acoustic driver, a flexible tube, and a passive actuator has been developed (Patent Documents 2 and 3). The vibration exciter employs a method in which compressed air generated by an acoustic driver is sent to a passive actuator via a flexible tube to transmit vibration to a subject. An elastic wave can be generated locally in the subject by arranging the passive actuator at any location on the subject without vibrating the entire subject.

  However, the vibration devices described in Patent Documents 2 and 3 are loud because they use an acoustic driver. Further, when the frequency is 100 Hz or more, there is a problem that the attenuation in the flexible tube that is the propagation path of the sound pressure energy becomes large. In addition, since energy absorption occurs in the flexible tube and air that mediates energy propagation, there is a problem that the energy efficiency is low and the apparatus is enlarged. Furthermore, since the resonance frequency of the components of the external vibration device has a complicated influence, it is very difficult to control with high accuracy. In addition, it is difficult to transmit vibration only to a predetermined target region, and there is a problem that unpleasant feeling is given when the subject is a human.

  And in invention of the said patent documents 1 thru | or 3, control of the frequency of the vibration to generate | occur | produce, an amplitude, a phase, etc. is so difficult that a frequency becomes high. For example, when using a low frequency, it is suitable for obtaining the average value of viscoelasticity over a wide area of the object to be measured. It is unsuitable. This cannot be used for the purpose of detecting small changes in hardness at an early stage.

JP-A-2005-304898 JP 2006-314787 A Special table 2008-201416

  In view of the above problems, the present inventors have developed a small vibration apparatus that can be placed in a gantry such as an MRI apparatus. The reason why the piezoelectric element is used as the vibrator is that the piezoelectric element can accurately control the amplitude and phase in a wide frequency band of about 50 Hz to 1000 Hz or more. The present inventors have used an external vibration device for generating a transverse wave (transverse wave device) (device for applying a shear stress to a subject) using a piezoelectric element as a vibrator, and an external vibration device for generating a longitudinal wave (longitudinal wave device). ) (Apparatus that applies normal stress to the subject). As an evaluation index of the elastic wave image, a signal-to-noise ratio (SNR: SNR = average value of amplitude / standard deviation of noise) was used. Here, it can be said that a device having a large SNR has higher measurement accuracy and is a more effective vibration device. As shown in FIG. 8, the transverse wave device (0801a) of (a) propagates only the transverse wave to the subject (0802a). Further, the longitudinal wave device (0801b) of (b) propagates a transverse wave as well as a longitudinal wave in the subject (0802b).

  Here, in the longitudinal wave and the transverse wave, the longitudinal wave has a long wavelength, and it is unsuitable to measure the viscoelastic modulus of a narrow region in the subject. Therefore, the method of measuring the viscoelastic modulus of the target region by detecting the transverse wave It was decided to adopt. In addition, when the elastic wave image generated by the shear wave device is compared with the elastic wave image generated by the longitudinal wave device, the longitudinal wave device has a larger SNR, and the elastic wave image is used to determine the viscosity in the uniform region of the subject. When the elastic modulus was measured, the standard deviation of the longitudinal wave device was smaller. That is, it has been shown that a method of generating a transverse wave with a longitudinal wave device is most effective.

However, since the transverse wave generated by the longitudinal wave device is rapidly attenuated inside the subject, the vibration is not sufficiently transmitted, and it is insufficient when the measurement target region is relatively deep in the subject.
Accordingly, in order to solve the above-described problem, the focusing-type vibration device of the present invention includes a plurality of vibrators that generate vibrations, and the vibration device configured to focus the vibrations generated from the vibrators in the measurement target region. I will provide a.

  (1) The present invention is a focusing type vibration apparatus used for an MR imaging apparatus or an MRI microscope apparatus for obtaining an image that can identify viscoelasticity of a subject by NMR, and is provided to a subject A plurality of vibration generating units for generating vibrations, a signal generating unit for providing a signal for generating vibrations to the vibration generating unit, and disposed between the vibration generating unit and the subject. There is provided a converging-type vibration device having a vibration transmitting chip that is directed to a focus region so as to propagate inside a subject as a wave and converge in the focus region.

  (2) The present invention provides the converging-type vibration device according to (1), wherein the vibration generating unit is a piezoelectric element.

  (3) The present invention provides the converging-type vibration device according to (1) or (2) above, wherein one vibration generating chip is provided for one vibration generating unit.

  (4) The present invention provides the converging-type vibration device according to any one of (1) to (3), wherein the vibration transmission chip is an acrylic block.

  (5) The present invention relates to the converging-type vibration device according to any one of (1) to (4), wherein the surface of the vibration transmitting chip that directly or indirectly contacts the subject has a concave curved surface shape. I will provide a.

  (6) The present invention provides the converging type excitation device according to any one of (1) to (5), wherein the signal generation unit provides a signal for the vibration generation unit to vibrate at a frequency of 100 hertz or more. To do.

  (7) The present invention relates to the converging-type vibration device according to any one of (1) to (6), which includes three or more vibration transmission chips.

  (8) In the present invention, any of the above (1) to (7), wherein the vibration transmitting chip is arranged so as to give vibration from the vicinity of the side surface on the table on which the subject accommodated for observation is arranged. A focusing accelerator according to claim 1 is provided.

  (9) In the present invention, a signal generation step for giving a signal to a plurality of vibrators to generate vibrations, and a vibration to be given to the subject by the plurality of vibrators are generated. A subject measurement comprising: a vibration focusing step for propagating and focusing in a focus region; and an NMR image acquisition step for detecting a transverse wave of the focused elastic wave and acquiring an NMR image using an MR imaging device or an MRI microscope device A method for acquiring an NMR image of a region is provided.

(10) The present invention provides an MR imaging device including the converging-type vibration device according to any one of (1) to (8).
(11) The present invention provides an MRI microscope apparatus including the converging-type vibration apparatus according to any one of (1) to (8).

  According to the converging-type vibration apparatus of the present invention, the frequency and phase of vibration transmitted to the subject can be controlled with high accuracy. In addition, since the apparatus can be miniaturized, it can be placed in a gantry such as an MRI apparatus, and can be brought into close contact with a subject to transmit vibration, resulting in high energy efficiency. Moreover, since vibrations in a high frequency band can be generated, the measurement accuracy is high. Furthermore, discomfort to the subject due to vibration can be suppressed.

Overview of the present invention Example diagram showing the shape of a vibration transmission chip External view of one embodiment of the present invention Sectional drawing of one Example of this invention Sectional drawing of one Example of this invention Process flow diagram of embodiment 2 Example of pulse sequence Schematic diagram showing elastic waves propagating by longitudinal and transverse wave devices

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, this invention should not be limited to these embodiments at all, and can be implemented in various modes without departing from the gist thereof. The first embodiment relates to claims 1 to 8, 10, 11 and the like. The second embodiment relates to claim 9 and the like.
<< Embodiment 1 >>
<Embodiment 1: Overview>

  The converging-type vibration device according to the present embodiment includes a plurality of vibration generation units, a signal generation unit, and a vibration transmission chip. The vibration transmitting chip is oriented so that elastic waves of vibrations generated by a plurality of vibration generating units propagate through the subject and converge in a specific focus region.

Therefore, an elastic wave having an amplitude necessary for measurement can be detected in the measurement target region inside the subject.
<Embodiment 1: Configuration>

  FIG. 1 is a conceptual diagram of a converging type vibration apparatus according to the present invention. It is sectional drawing of the figure which made the focusing type vibration apparatus contact | adhere to the test subject (0103) arrange | positioned on the bed (0108) of an MRI apparatus. A focusing-type vibration apparatus of the present invention is a vibration apparatus used in an MR imaging apparatus or an MRI microscope apparatus, and includes a plurality of vibration generation units (0101), a vibration transmission chip (0102), and a signal generation unit ( 0105).

  The MR imaging apparatus is, for example, an MRI apparatus, a clinical MRI apparatus or the like, and the MRI microscope apparatus is an NMR microscope (Nuclear Magnetic Resonance microscope), an MRM (Magnetic Resonance Microscope), or the like. Hereinafter, the “MR imaging apparatus or MRI microscope apparatus” is referred to as an MRI apparatus or the like.

  The “signal generation unit” (0105) is, for example, an electric signal that drives the vibration generation unit (0101) and its generation means. When the vibration generating unit (0101) is a piezoelectric element, the signal has a waveform indicated by “Oscillation” in FIG. The amplitude, wavelength, phase, and the like of vibration generated by a vibration generating unit, which will be described later, are controlled by a signal output from the signal generating unit (0105) to the vibration generating unit (0101). FIG. 7 will be described in the second embodiment.

  In addition, the signal which the said signal generation part (0105) gives is not specifically limited if it is the content which can generate | occur | produce the vibration required for the method of acquiring the image which can identify the viscoelasticity of a test subject. Preferably, the signal is controlled so that a vibration generating unit (0101), which will be described later, generates vibrations having a frequency of approximately 50 hertz or higher. This is because vibration with a frequency of less than about 50 hertz may not provide an image with a high signal-to-noise ratio that is necessary for obtaining an image that can identify the viscoelasticity of the subject. More preferably, it is 100 hertz or more. This is because an image with a high signal-to-noise ratio can be obtained with an amplitude suitable for image acquisition (about 0.01 mm). In addition, since the wavelength becomes shorter as the frequency is larger, even when the subject is relatively small, or when measuring the viscoelasticity of a small tissue inside the subject, the measurement target region described later is accurate. An image is obtained that can identify the viscoelasticity of the subject. When a piezoelectric element is used for the vibration generating unit (0101), a signal in a high frequency band of 200 Hz or higher can be given, and the amplitude and phase can be accurately controlled.

  The signal generator (0105) includes, for example, a function generator (0107) for generating an arbitrary vibration waveform in synchronization with an MRI apparatus or the like, and an amplifier (0106) for amplifying the vibration waveform.

  The “vibration generator” (0101) generates a vibration to be applied to the subject (0103). For example, an electromagnet driver, an acoustic driver (Patent Documents 2 and 3), an ultrasonic motor (or a piezoelectric motor), a piezoelectric element, and the like are applicable. Of these, piezoelectric elements are preferred. This is because a high frequency band of 200 Hz or higher can be used, and the amplitude and phase can be controlled even in the high frequency band. In addition, it is possible to reduce the size of the converging-type excitation device.

  The present invention includes a plurality of vibration generating units (0101), and the vibration generated by each vibration generating unit (0101) is focused in a focus region inside the subject, and the subject's An image capable of identifying viscoelasticity is acquired. Therefore, the converging-type vibration apparatus according to the present invention has two or more vibration generating units (0101). As will be described later, the plurality of vibration generating units (0101) may be arranged on a circular arc or on a spherical lattice so that the vibration transmitting chip (0102) can be easily oriented to the focus area (0104). May be.

  In addition, the frequency, amplitude, wavelength, phase, and the like of the vibration generated by each vibration generator (0101) may be appropriately determined according to the depth of the measurement target region in the subject, the type of the measurement target tissue, and the like. In addition, control is performed in consideration of the mutual relations such as the timing of vibration generation, the propagation speed of elastic waves inside the subject, and the timing of image acquisition by NMR. Note that all of these may be determined and controlled based on the signal generator (0105).

  The “subject” (0103) is an image acquisition target, and is not limited to humans, but includes animals such as mice, plants, and processed products.

  The “vibration transmitting chip” (0102) is disposed between the vibration generating unit (0101) and the subject (0103), and the generated vibration propagates inside the subject as an elastic wave to focus the region (0104). In such a manner, it is directed to the focus area so as to be converged at the center. That is, the vibration generated by the vibration generating unit (0101) is transmitted to the subject via the vibration transmitting chip (0102).

  The “elastic wave” is composed of a transverse wave and a longitudinal wave, and the focused vibration exciter of the present invention applies vibration to the subject so as to propagate the longitudinal wave and the transverse wave inside the subject. In addition, although either a longitudinal wave or a transverse wave may be used for acquiring an NMR image, a transverse wave having a short wavelength is preferable. Note that when acquiring an image using a transverse wave, even if a longitudinal wave is generated, the image acquisition is not affected, and vice versa.

  Further, the “focus area” refers to the vicinity of the center of the measurement target area (0111) in which the viscoelasticity is to be measured, among the image acquisition target areas (0110) inside the subject. Here, the image acquisition target region (0110) is a region in which an image can be acquired in an MRI apparatus or the like using the focusing type vibration device of the present invention, and among these, a region where viscoelasticity is to be measured more accurately. A peripheral region including the center is called a measurement target region (0111). “Directional arrangement in the focus area” means that the vibration transmitting chips (0402 and 0502) are arranged radially with the focus area (0406 and 0506) as the center, as shown in FIGS. In other words, when the elastic wave travels in the direction normal to the surface in contact with the subject, that is, the ceiling surface of the vibration transmission chip, the normal line of the ceiling surface of each vibration transmission chip intersects at the “focus area” To do.

  The measurement target region (0111) may be, for example, an upper region or a lower region of the image acquisition target region (0110), or may be a specific tissue such as a liver, kidney, brain, or the like.

  The vibration transmission chip (0102) is not particularly limited as long as it is a hard non-magnetic material that absorbs less vibration and hardly causes distortion in vibration. For example, wood, bamboo, non-magnetic plastic, etc. are applicable. An acrylic block is preferable. This is because it is robust, cheap, can be mass-produced, and easy to process. The connection method of the vibration transmitting chip and the vibration generating unit is not limited as long as the functions of each other are not impaired, and the vibration transmitting chip and the vibration generating unit may be integrally connected. In addition, the distance between the vibration generating unit (0101) and the subject (0103), that is, the vibration transmitting chip (0102) is not so absorbed that the vibration generated by the vibration generating unit (0101) is not absorbed and the vibration waveform is not distorted. ) Is preferably short.

  In addition, it is desirable that the shape of the surface where the vibration transmitting chip (0102) directly or indirectly contacts the subject can be appropriately changed according to the subject. An example of the shape is shown in FIG. The vibration transmitting chip (0201a) in (a) has a substantially rectangular parallelepiped shape, and the surface in contact with the subject is the same as the cross-sectional shape of the vibration generating unit (0202a). In addition, the vibration transmission chip (0201b) in (b) has a plane quadrangular surface in contact with the subject, and is configured to be larger than the cross-sectional shape of the vibration generating unit (0202b). Further, the vibration transmission chip (0201c) in (c) has a concave curved surface on the surface in contact with the subject, and is configured to be larger than the cross-sectional shape of the vibration generator (0202c). The vibration transmission chip of (b) and (b) of (a) is easier to converge the elastic wave propagating inside the subject than (a) and (b). In particular, (c) is preferable because the surface in contact with the subject has a concave curved surface shape, and the focusing of elastic waves can be controlled to a higher degree. Moreover, since the loss of the vibration energy which a vibration generation part (0101) generate | occur | produces can be suppressed, it is preferable also at the point that energy efficiency is good.

  Note that “the vibration transmission chip is directly in contact with the subject” means that the vibration transmission chip and the subject are in direct contact with each other without any intervention. In contrast, “indirect contact” means, for example, that the vibration transmission chip and the subject are more closely attached and that a gel-like substance is interposed between the vibration transmission chip and the subject so that vibration can be easily transmitted. And so on. However, in such a case, the gel-like substance must not absorb vibrations or cause distortions in the vibrations.

  Note that there may be one vibration transmission chip (0102) for the plurality of vibration generating units (0101), or a plurality of vibration transmission chips (0101), and there is no particular limitation. Preferably, as shown in FIG. 1, one vibration transmission chip (0102) is provided for one vibration generator (0101). This is because the direction in which the vibration generated by each vibration generating unit propagates as an elastic wave can be finely controlled, so that the focusing of the elastic wave in the focus region can be controlled more precisely.

  In addition, a configuration including three or more vibration transmitting chips (0102) is preferable regardless of the number of vibration generating units (0101). This is because as the number of vibration transmission chips (0102) increases, the vibration transmitted from one vibration transmission chip (0102) to the subject can be set to be relatively small, so that discomfort given to the subject can be suppressed. In addition, by controlling each vibration transmission chip (0102), it is possible to control the vibration applied to the subject. 3 to 5 exemplify a vibration exciter including nine vibration generators and nine vibration transmission chips. 3 to 5 will be described in Example 1 described later.

The vibration transmission chip (0102) may be arranged to transmit vibration from the upper surface or the bottom surface of the subject accommodated for observation. Preferably, it arrange | positions so that a vibration may be given from the side surface vicinity of the stand (0108) which arrange | positions a test subject (0103) like FIG. This is because a bed such as an MRI apparatus has a relatively large width, so that when the subject (0103) is placed on the table (0108), the focusing type addition of the present invention is added to the empty space near the side surface. This is because a vibration device is installed to appropriately transmit vibration to the subject (0103). Therefore, the vibration apparatus according to the present embodiment is preferable because it is not necessary to prepare an installation place or the like and an existing MRI apparatus or the like can be used as it is. In addition, since the vibration transmitting chip (0102) and the subject (0103) can be arranged closer to each other, loss of vibration energy generated by the vibration generating unit (0101) can be suppressed, so that energy efficiency is good. Furthermore, since it can be easily installed at a desired position with respect to the subject, there is no burden on the subject, and preparation for measurement can be performed in a short time.
<Embodiment 1: Effect>

According to the focusing type vibration device of this embodiment, the frequency and phase of vibration transmitted to the subject can be controlled with high accuracy, energy efficiency is good, and the device can be downsized. Moreover, since vibrations in a high frequency band can be generated, the measurement accuracy is high. Furthermore, discomfort to the subject can also be suppressed.
<< Embodiment 2 >>
<Embodiment 2: Overview>

  In the NMR image acquisition method of the present embodiment, signals are given to a plurality of vibrators to generate vibrations (signal generation step), and the vibrations generated by the vibrators propagate as elastic waves inside the subject and enter the focus region. And then focusing (vibration focusing step), and the transverse wave of the focused elastic wave is detected and an NMR image is acquired (NMR image acquiring step).

According to the method, it is possible to highly control the vibration generated by the vibrator and the elastic wave focused in the focus area according to the type of the subject and the type of the measurement target area inside the subject, so that a desired NMR image can be obtained. Can be obtained.
<Embodiment 2: Configuration>

  FIG. 6 shows a processing flow diagram of this embodiment. The NMR image acquisition method of the present embodiment includes a signal generation step (0601) that gives signals to a plurality of transducers, and a vibration focusing step that focuses the vibrations generated by the transducers as elastic waves in a focus region inside the subject ( 0602) and an NMR image acquisition step (0603) of detecting a transverse wave of the focused elastic wave and acquiring an NMR image using an NMR apparatus or the like.

  The “signal generation step” (0601) is a step of giving signals to a plurality of vibrators in order to generate vibration. The “vibrator” corresponds to the vibration generating unit in the first embodiment. The “signal” refers to an electric signal for driving the vibrator. The signal given to the vibrator is not particularly limited as long as the vibration generated by the vibrator is focused as an elastic wave in the focus region and a desired NMR image can be acquired. The signals given to the plurality of vibrators may all be the same signal, or may be different signals depending on the vibrator. This may be appropriately determined in consideration of the subject type, the measurement target region type, the distance to the focus region, and the like. Based on the signal given in this step, vibration is generated in a vibration focusing step described later.

  The “vibration focusing step” (0602) is a step of generating a vibration given to the subject by a plurality of vibrators (0604), and the vibration propagates inside the subject as an elastic wave to be focused in the focus region (0605). It is. “Propagating inside the subject as an elastic wave” means that both a transverse wave and a longitudinal wave propagate inside the subject. Of the elastic wave, only the transverse wave is detected in the NMR image acquisition step described later. This is because the transverse wave has a short wavelength, so that a highly accurate image can be acquired, the propagation speed is slow, and the propagating wave is easy to measure.

  The “NMR image acquisition step” (0603) is a step of detecting a transverse wave of a focused elastic wave and acquiring an NMR image using an MR imaging apparatus or an MRI microscope apparatus. Here, an existing method may be used as a method for detecting a transverse wave of an elastic wave and acquiring an NMR image using an NMR apparatus or the like.

  In addition, there exists MRE method (Magnetic Resonance Elastography) in the method of acquiring the NMR image of a test subject by the NMR image acquisition method of this embodiment, and measuring the viscoelasticity inside a test subject.

  The MRE method is a magnetic resonance imaging (MRI) for imaging a resonance signal (Magnetic Resonance signal, MR signal) of a proton contained in an object by using a technique of Nuclear Magnetic Resonance (NMR). Is one of the photography methods using A pattern of vibration propagating through the subject is imaged by photographing while applying vibration from outside the subject.

  The pulse sequence used for acquiring the NMR data is not particularly limited, such as SE method (Spine Echo), EPI method (Echo Planner), GRE method (Gradient Echo), and various sequences based on these methods. In the basic pulse sequence of the MRE method, the subject is vibrated using an external vibration device, and an elastic wave is induced in the subject (signal generation process, vibration focusing process). When a gradient magnetic field (Motion Sensitizing Gradients, MSG) synchronized with vibration is applied during imaging, the MR signal generated by the subject causes a phase difference with respect to the signal when no gradient magnetic field is applied. Then, the MR signal including the phase difference is subjected to two-dimensional Fourier transform, and an imaginary part corresponding to the phase change amount is imaged to visualize the vibration propagating in the subject.

From the obtained image, the wavelength, frequency, and reduction factor of the elastic wave propagating through the subject are calculated, and the viscoelastic modulus of the subject is measured by the wave equation.
<Embodiment 2: Effect>

  According to the NMR image acquisition method of the present embodiment, the amplitude necessary for acquiring the NMR image in the focus region can be obtained, and the vibration applied to the subject can be controlled to a high degree, so that a desired NMR image can be obtained.

  FIG. 3 shows an example of the configuration of the vibration generating unit and the vibration transmitting chip of the vibration exciter according to this embodiment. (A), (b) shows a perspective view, (c) shows a top view, (d) shows a bottom view. FIG. 4 is a sectional view taken along line AA ′ in FIG. 3A, and FIG. 5 is a sectional view taken along line BB ′ in FIG. The converging-type vibration apparatus of the present embodiment includes nine vibration generation units and nine vibration transmission chips. In FIG. 3, only one vibration transmission chip (0301) is shown for convenience. The surface on which the vibration transmitting chips (0301) are arranged has a concave curved surface shape.

  In FIG. 3, nine vibration transmission chips (0301) are arranged in a lattice pattern. Further, each vibration transmission chip (0301) is oriented so that the elastic wave is focused in the focus region. That is, the surface which connected the front-end | tip (surface which contacts a test subject) of a vibration transmission chip | tip is arrange | positioned so that it may become a concave curved surface shape. The center point of the concave curved surface shape corresponds to the focus area. Reference numeral 0302 denotes holes for piezoelectric element wiring and heat dissipation. In addition, since the vibration generation part is hidden, it is not illustrated.

  FIG. 4 is a cross-sectional view taken along the line AA ′ in FIG. In FIG. 1, it is sectional drawing seen from the upper surface direction of the paper surface. A vibration generating unit (0401) made of a piezoelectric element and a vibration transmission chip (0402) made of an acrylic block disposed between the vibration generating unit and the subject (0405) are provided. These are arranged so as to be sandwiched between two flat plates (0403) made of acrylic material and having a thickness of 5 mm (FIG. 5). Each acrylic block (0402) is oriented to the focus area (0406). In this embodiment, the focus area (0406) is set to a depth of 100 mm from the surface of the subject. The piezoelectric element (0401) is stretched and contracted in the longitudinal direction and imparts vibration to the subject (0405) via the acrylic block (0402). Only the bottom surface of (0401) is fixed. Further, the side surface is configured so as not to cause friction with the acrylic flat plate (0403). This is because the expansion and contraction of the piezoelectric element is not hindered.

  In addition, the piezoelectric element (0401) of a present Example is 40 mm x 3 mm x 2 mm. The acrylic block (0402) is 10 mm × 3 mm × 2 mm.

  FIG. 5 is a sectional view taken along line BB ′ in FIG. In FIG. 1, it is sectional drawing seen from the right side of the paper surface. A vibration generation unit (0501) made of a piezoelectric element and a vibration transmission chip (0502) made of an acrylic block disposed between the vibration generation unit and the subject (0505) are provided. Each acrylic block (0502) is oriented to the focus area (0506). The piezoelectric element (0501) is disposed so as to be sandwiched between two acrylic flat plates (0503) (0403 in FIG. 4). Also, a substantially fan-shaped acrylic flat plate (0504) having a thickness of 5 mm is disposed between the acrylic flat plate (0503) and an acrylic flat plate sandwiching another piezoelectric element. Other configurations are the same as those shown in FIGS.

FIG. 7 shows an example of a pulse sequence for elastic wave imaging using the ultra high speed imaging method (SE-EPI). In the figure, “TR” (Repetition Time) indicates the repetition time of MR signal acquisition, and “TE” (Echo Time) indicates the time from application of a 90 ° RF (Rario Frequency) pulse until the echo of the MR signal appears. . “Delay Time” is a delay time from the vibration start time to the application of the 90 ° RF pulse. In addition, “Gx, Gy, Gz” is used to select an imaging section from a three-dimensional orthogonal space (x, y, z) in combination with an RF pulse, and to add position information in the section to the frequency and phase of the MR signal. The gradient magnetic field for is shown. “MSG” (Motion Sensitizing Gradient) is a vibration-sensitized gradient magnetic field, and the displacement information of the same frequency and direction as MSG in the weak elastic wave generated in the elastic body is added to the phase of the MR signal. The gradient magnetic field to do is shown. “Oscillation” indicates vibration generated by the focusing type vibration device according to the present invention and applied to the subject.
By looking at the result of converging the vibration to the focus region, selecting the vibration generating unit that generates the vibration, or changing the signal of the signal generating unit by the vibration generating unit and converging the vibration to the focus region again. A better effect can also be obtained.

0101 Vibration generator 0102 Vibration transmission chip 0103 Subject 0104 Focus area 0105 Signal generator 0106 Amplifier 0107 Function generator 0108 Sleeper 0109 Gantry 0110 Image acquisition area 0111 Measurement object area

Claims (11)

In order to obtain an image capable of identifying the viscoelasticity of a subject by NMR, it is a focusing type vibration apparatus used in an MR imaging apparatus or an MRI microscope apparatus,
A plurality of vibration generators for generating vibrations applied to the subject;
A signal generation unit that gives a signal for vibration generation to the vibration generation unit;
A vibration transmitting chip disposed between the vibration generating unit and the subject and oriented to the focus region so that the generated vibration propagates through the subject as an elastic wave and converges in the focus region;
A converging-type excitation device having   The focusing vibration exciter according to claim 1, wherein the vibration generating unit is a piezoelectric element.   The focusing-type vibration apparatus according to claim 1, wherein one vibration transmission chip is provided for one vibration generation unit.   The focusing vibration exciter according to any one of claims 1 to 3, wherein the vibration transmitting chip is an acrylic block.   5. The converging-type vibration device according to claim 1, wherein a surface of the vibration transmission chip that directly or indirectly contacts the subject has a concave curved surface shape.   6. The converging-type excitation device according to claim 1, wherein the signal generating unit provides a signal for the vibration generating unit to vibrate at a frequency of 100 hertz or higher.   The focusing-type excitation apparatus as described in any one of Claim 1 to 6 provided with three or more vibration transmission chips.   The focusing type acceleration device according to any one of claims 1 to 7, wherein the vibration transmission chip is arranged so as to apply vibration from a vicinity of a side surface on a table on which a subject accommodated for observation is arranged. A signal generating step of giving signals to a plurality of vibrators to generate vibrations;
A vibration focusing step that generates vibrations to be given to the subject by a plurality of vibrators, and the vibrations propagate inside the subject as elastic waves and are focused in the focus region;
An NMR image acquisition step of detecting a transverse wave of the focused elastic wave and acquiring an NMR image using an MR imaging device or an MRI microscope device;
The NMR image acquisition method of the subject measurement area | region which has this.   An MR imaging apparatus comprising the converging-type excitation device according to claim 1.   The MRI microscope apparatus provided with the focusing type vibration apparatus as described in any one of Claim 1 to 8.