Vibration transmission device

Abstract

To efficiently transmit vibration to a subject.SOLUTION: A vibration transmission device for transmitting vibration to a measuring object from a sound wave generator that generates a sound wave in an MRE (Magnetic resonance elastography) includes a plurality of oscillators for respectively transmitting the vibration.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a vibration transmission device. [Background technology]

[0002] In magnetic resonance elastography (MRE) measurements, vibrations are transmitted to an organ or the like that is the measurement target by a passive driver. As shown in the figures in Non-Patent Documents 1 to 4, a single disk-shaped passive driver is usually used. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Magnetic resonance elastography by direct visualization of propagating acoustic strain waves, Science. 1995 Sep 29;269(5232):1854-7. doi: 10.1126 / science.7569924. [Non-Patent Document 2] Tissue characterization using magnetic resonance elastography: preliminary results, Phys Med Biol. 2000 Jun;45(6):1579-90. doi: 10.1088 / 0031-9155 / 45 / 6 / 313. [Non-Patent Document 3] MR elastography of the liver: preliminary results, Radiology. 2006 Aug;240(2):440-8. doi: 10.1148 / radiol.2402050606. [Non-Patent Document 4] Magnetic resonance imaging of hepatic fibrosis: emerging clinical applications, Hepatology. 2008 Jan;47(1):332-42. doi: 10.1002 / hep.21972. Summary of the Invention [Problem to be solved by the invention]

[0004] However, passive drivers that are commonly used may not be properly fixed due to differences in physique. If the passive driver is fixed in an inappropriate position or if it is not fixed and its position changes, it may have a negative effect on the accuracy of the MRE examination. An object of the present invention is to provide a vibration transmission device that solves the above-mentioned problems. [Means for solving the problem]

[0005] A vibration transmission device according to one embodiment of the present invention is a vibration transmission device that transmits vibrations from an acoustic wave generator that generates acoustic waves to a measurement object in MRE (magnetic resonance elastography), and is equipped with a number of transducers that each transmit the vibrations. Effect of the Invention

[0006] According to the present invention, vibrations can be efficiently transmitted to a subject. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram showing a magnetic resonance imaging apparatus according to an embodiment of the present invention. [Diagram 2] 1A and 1B are diagrams illustrating a structure of a vibration generating device according to an embodiment of the present invention. [Diagram 3] FIG. 13 is a diagram showing an example of a method of using the transducer. [Figure 4A] FIG. 13 is a diagram showing vibrations in wave pattern W2. [Figure 4B]FIG. 13 is a diagram showing vibrations in wave pattern W3. [Diagram 5] These are MRE images generated by measurements using different devices and wave patterns. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0009] (Configuration of Magnetic Resonance Imaging Apparatus) 1 is a diagram showing a magnetic resonance imaging apparatus 1 according to this embodiment. The magnetic resonance imaging apparatus 1 includes a magnetic field generator 2, a bed 4, a vibration generator 6, and a control device 21. The magnetic field generator 2 has a through-hole 3 that passes horizontally through the inside. The bed 4 is installed so as to be slidable relative to the magnetic field generator 2 through the through-hole 3. This allows the bed 4 and a subject 5 lying on the bed 4 to pass through the through-hole 3.

[0010] The magnetic field generating device 2 includes a static magnetic field generating device 11, a gradient magnetic field generating device 12, a high frequency magnetic field generating device 13, and an electromagnetic wave receiving device 14. The static magnetic field generating device 11 includes, for example, a superconducting electromagnet or a permanent magnet, and generates a static magnetic field in the through hole 3. The gradient magnetic field generating device 12 is disposed closer to the through hole than the static magnetic field generating device 11, and has, for example, a coil. The gradient magnetic field generating device 12 generates a gradient magnetic field in the through hole 3. The high frequency magnetic field generating device 13 is disposed closer to the through hole than the gradient magnetic field generating device 12, and has, for example, a coil. The high frequency magnetic field generating device 13 generates a high frequency magnetic field in the through hole 3. The electromagnetic wave receiving device 14 is disposed closer to the through hole than the high frequency magnetic field generating device 13, and has, for example, a coil. The electromagnetic wave receiving device 14 receives electromagnetic waves generated by an imaging target in the through hole 3.

[0011] The magnetic field generating device 2 is electrically connected to the control device 21 via a cable. The control device 21 controls the timing and magnitude of the generation of the gradient magnetic field by transmitting a control signal to the magnetic field generating device 2. The control device 21 also obtains information about the electromagnetic waves from the electromagnetic wave receiving device 14. The control device 21 may transmit and receive signals to and from the magnetic field generating device 2 via wireless communication.

[0012] The vibration generating device 6 includes a vibration transmitting device 15, a sound wave generating device 16, and a tube 17. The vibration transmitting device 15 and the sound wave generating device 16 are connected via the tube 17. The device is configured such that sound waves (vibrations in the air) generated by the sound wave generating device 16 are transmitted to the vibration transmitting device 15 via the tube 17. The tube 17 is, for example, hollow, and made of a non-magnetic material.

[0013] The sound wave generator 16 is provided with, for example, a voice coil to generate sound waves. The vibration transmitter 15 is attached, for example, to a body surface corresponding to the part to be examined of the subject 5. The sound waves generated by the sound wave generator 16 are transmitted to the vibration transmitter 15 via a tube 17, and are transmitted to the body surface corresponding to the part to be examined of the subject 5 to which the vibration transmitter 15 is attached.

[0014] The sound wave generator 16 is electrically connected to the control device 21 via a cable. The control device 21 transmits a control signal to the sound wave generator 16 to control the frequency and phase of the vibrations, the timing of vibration generation, and the like.

[0015] Fig. 2 is a diagram showing the structure of the vibration generator 6 according to this embodiment. The vibration transmitter 15 includes a plurality of vibrators 151 and a plurality of connecting members 155. In the example shown in Fig. 2, the vibration transmitter 15 includes five vibrators 151-1 to 151-5. Each of the transducers 151 is connected to the sound wave generator 16 via a tube 17. The tube 17 includes a first tube 171, a branching portion 172, and a second tube 173. The tube 17 includes the same number of second tubes 173 as the number of transducers 151. In the vibration generator 6 shown in FIG. 2, the tube 17 includes five second tubes 173-1 to 173-5. The first tube 171 connects the sound wave generator 16 to the branching portion 172. The branching portion 172 connects the first tube 171 to the second tube 173. The second tubes 173 connect the branching portions 172 to the corresponding transducers. The length of the second tube 173 may be different for each of the transducers 151 to be connected. For example, the second tube 173 has a structure including a tube within a tube, and the length can be expanded or contracted by sliding the tubes relative to each other, and the length can be arbitrarily adjusted. The length of the second tube 173 connected to the transducer 151 can be adjusted by connecting a tube of a desired length to the transducer 151 from among a plurality of tubes of different lengths, or by arbitrarily selecting the number of short tubes constituting the second tube 173 when the second tube 173 is composed of a plurality of short tubes. The short tube preferably has a length of 1 / N of the wavelength (N is an integer). By adjusting the length of the second tube 173 and changing the path length through which the sound wave is transmitted from the sound wave generator 16, the phase of the vibration transmitted by the transducer 151 can be arbitrarily adjusted for each transducer 151. For example, by extending the length of the second tube 173 by 1 / 4 of the wavelength of the sound wave propagating through the tube 17, the initial phase of the vibration generated by the transducer 151 can be delayed by π / 2.

[0016] Adjacent transducers 151 are connected to each other by a connecting member 155. The connecting member 155 is made of a bendable material (e.g., flexible resin or elastomer). This allows the vibration transmission device 15 to be used by wrapping it around the body, allowing vibrations to be transmitted to the target more appropriately. The multiple transducers 151 are lined up at regular intervals in the longitudinal direction of the vibration transmission device 15. The vibration transmission device 15 can be bent around an axis perpendicular to the longitudinal direction by the connecting member 155. FIG. 3 is a diagram showing an example of how to use the transducer 151. The transducer 151 is brought into close contact with the skin so as to cover the ribs and liver. The transducer 151 transmits vibrations to the ribs, and thereby to the liver.

[0017] The transducer 151 includes a connection part 152 and a main body 153. The side of the transducer 151 that comes into contact with the subject 5 is called the bottom side, and the side opposite the bottom side is called the top side. The main body 153 has an opening on the bottom side and is configured to be hollow. The connection part 152 is provided on the top of the main body 153. A tube 17 is connected to the connection part 152. As a result, when the bottom side of the transducer 151 is brought into contact with the subject 5, sound waves transmitted to the connection part 152 via the tube 17 vibrate the air inside the main body 153, vibrating the part in contact with the subject 5. Connecting member 155 connects the bottom side of transducer 151. It is desirable that the volume of air contained in main body 153 and the area of ​​the opening on the bottom side have the following relationship. Internal volume of the main body (cm 3 )=[1.41(cm)×vibration area(cm 2 )]+24.90(cm 3 )

[0018] The size of each transducer 151, the volume of air contained in main body 153, and the area of ​​the opening on the bottom side may be different. Also, each connection portion 152 may have a different length. It is preferable that the size of each transducer 151, the volume of air contained in main body 153, and the area of ​​the bottom opening are the same, and that the lengths of each connection portion 152 are the same. By making the sizes of each transducer 151 the same and making the lengths of each connection portion 152 and second tube 173 the same, it is possible to make the waves generated by the superposition of in-phase sound waves output from each transducer 151 into spherical waves.

[0019] The transducer 151 may have a vibration plate on the bottom side, and transmit vibrations of the air inside the main body 153 to the subject 5 in contact with the transducer 151 via the vibration plate.

[0020] In this embodiment, the vibration transmission device 15 includes a plurality of vibrators 151. The vibration transmission device 15 as a whole is about the same size as a normally used passive driver, and the size of each of the vibrators 151 is small. This allows the device to be placed in close contact with a body having a curve, and ensures vibration strength. Moreover, the multiple transducers 151 are connected by a connecting member 155. In particular, the bottom sides of the multiple transducers 151 are connected by a connecting member 155. This makes it easy to bring the transducers into close contact with the body, and allows vibrations to be efficiently transmitted to the subject.

[0021] In this embodiment, by adjusting the length of the tube 17, the vibration transmission device 15 can transmit vibrations of different phases even if the phase of the sound generated by the sound wave generator 16 is constant. This makes it possible to transmit waves with new characteristics to the target without making major changes to the control device 21 or the sound wave generator 16.

[0022] (Experimental Results) An experiment was conducted to compare a conventional vibration transmission device (passive driver) with the vibration transmission device according to this embodiment. In the experiment, the device shown in FIG. 2 was used as the conventional passive driver and the proposed vibration transmission device 15. When using the vibration transmission device 15, vibrations were transmitted using a pattern (wave pattern W1) in which vibrations output from all the vibrators 151 were in the same phase, and a pattern (wave patterns W2 and W3) in which vibrations of different phases were output.

[0023] FIG. 4A is a diagram showing the vibration phase in wave pattern W2. FIG. 4B is a diagram showing the vibration phase in wave pattern W3. In wave pattern W2, when the wavelength of vibration is λ, second tube 173-1 is λ / 2 longer than second tube 173-3, second tube 173-2 is λ / 4 longer than second tube 173-3, second tube 173-4 is λ / 4 shorter than second tube 173-3, and second tube 173-5 is λ / 2 shorter than second tube 173-3. As a result, when the phase of the vibration output from transducer 151-3 is used as a reference, the phase of the vibration output from transducer 151-2 is shifted by +2 / π, the phase of the vibration output from transducer 151-1 is shifted by +π, the phase of the vibration output from transducer 151-4 is shifted by -2 / π, and the phase of the vibration output from transducer 151-5 is shifted by -π. In wave pattern W3, when the wavelength of the vibration is λ, the lengths of second tube 173-2 and second tube 173-4 are the same, and second tubes 173-1, 173-3, and 173-5 are λ / 2 longer than second tube 173-2. As a result, in wave pattern W2, when the phase of the vibration output from transducers 151-2 and 151-4 is used as a reference, the phase of the vibration output from transducers 151-1, 151-3, and 151-5 is shifted by +π. The above length of the second tubes 173 is merely an example, and the length of each of the second tubes 173 can be increased or decreased by an integer multiple of λ to transmit vibrations of the same wave pattern.

[0024] FIG. 5 shows MRE images generated by measurements using each device and wave pattern. In the vibration generating device 6 used in the comparative device, one disk-shaped passive driver was used as the vibration transmitting device 15. In the device proposed in this embodiment, the vibration transmitting device 15 can be placed closer to the subject than in the comparative device, vibrations can be transmitted more efficiently, and MRE images with higher resolution can be obtained. In addition, by transmitting vibrations in different wave patterns, the organ to be measured can be vibrated in different ways. This allows different MRE images to be obtained, which may enable more diverse diagnoses.

[0025] Other Embodiments Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design changes, etc. are possible within the scope that does not deviate from the gist of the present invention.

[0026] The vibration transmission device 15 does not necessarily have to include the connecting member 155. In this case, each vibrator 151 is used by being brought into close contact with the body independently. In this case, just as it is desirable that the lengths of the connecting members 155 are the same, it is also desirable that the distances between the vibrators 151 when brought into close contact with the body are equal. [Explanation of symbols]

[0027] REFERENCE SIGNS LIST 1 magnetic resonance imaging device, 2 magnetic field generator, 3 through hole, 4 bed, 5 subject, 6 vibration generator, 11 static magnetic field generator, 12 gradient magnetic field generator, 13 high frequency magnetic field generator, 14 electromagnetic wave receiver, 15 vibration transmitter, 16 sound generator, 17 tube, 21 control device, 151 transducer, 152 connection part, 153 main body, 154 diaphragm, 155 connecting member

Claims

1. In MRE (Magnetic Resonance Elastography), a vibration transmission device that transmits vibrations from a sound wave generator that generates sound waves to a measurement target, A plurality of vibrators each transmitting the vibration are provided. Vibration transmission device.

2. a plurality of tubes for connecting the sound wave generating device and the transducers to each other and for propagating the sound waves; The length of each of the plurality of tubes can be extended and shortened. The vibration transmission device according to claim 1 .

3. The plurality of transducers are connected by a bendable connecting portion. The vibration transmission device according to claim 1 or 2.

4. The plurality of transducers are connected to each other at their ends opposite to the connection portion with the sound wave generating device by the connection portion. The vibration transmission device according to claim 3 .

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