JP5669889B2 - Biological information acquisition device - Google Patents

Description

  The present invention relates to a biological information acquisition apparatus.

  In general, imaging devices using X-rays, ultrasound, and MRI (nuclear magnetic resonance method) are widely used in the medical field. On the other hand, research on optical imaging devices that obtain in-vivo information by propagating light irradiated on a living body from a light source such as a laser into a subject such as a living body and detecting the propagating light is also active in the medical field. It is advanced to. One such optical imaging technique is Photoacoustic Tomography (PAT: Photoacoustic Tomography).

  Photoacoustic tomography surrounds the subject with time-dependent changes in the acoustic wave generated from the living tissue that has absorbed the energy of the light propagated and diffused within the subject by irradiating the subject with pulsed light generated from the light source. It is a technique for visualizing information related to optical characteristic values inside a subject by detecting the signals at a plurality of locations and mathematically analyzing the obtained signals. As a result, an initial pressure generation distribution or optical characteristic value distribution generated by light irradiation in the subject, particularly a light energy absorption density distribution, and the like can be obtained, and can be used for specifying a malignant tumor location.

  In general, in photoacoustic tomography, the time variation of an acoustic wave is measured with respect to an object at various points on a closed space surface, particularly a spherical measurement surface, which surrounds the entire object. If it can be measured using (point detection), theoretically, the initial sound pressure distribution generated by light irradiation can be completely visualized. However, in an actual subject, it is impossible to obtain acoustic wave detection information on the entire closed space surface surrounding the whole subject. For this reason, a flat type measurement system as shown in FIG. 1 may be used. In FIG. 1, 1 is an acoustic wave detector, 2 is a light absorber or acoustic wave generation source, 3 is a subject, 4 is an image reconstruction area, and 5 is an acoustic wave. Even in such a flat plate type measurement system, if an acoustic wave can be measured in a sufficiently large area (ideally an infinite surface) with respect to the area 4 for visualizing the initial pressure distribution due to the pressure generated by pulse light irradiation, the acoustic wave It is mathematically known that the source distribution of the above can be substantially reproduced (see Non-Patent Document 1).

PHYSICAL REVIEW E71, 016706 (2005)

  However, if the size of the acoustic wave detector 1 is increased and the number of detector elements included in the acoustic wave detector 1 is increased in order to increase the acoustic wave measurement region, the electronic control system for controlling the size becomes large. The result is a very expensive system. Further, when a large acoustic wave detector having a large number of elements is manufactured, a method in which a large acoustic wave detector is manufactured by dividing into small element groups that are easy to manufacture and arranging a plurality of elements is used.

  However, when the number of elements becomes enormous, all the elements may not be wired due to restrictions on the wiring cables that send electric signals from the respective elements to the outside (the cables become thicker). Furthermore, a groove (boundary portion) for reducing crosstalk of elements is provided between the divided element groups, and an acoustic wave cannot be detected in that region.

  Therefore, in view of the above problems, the present invention has a more realistic distribution of acoustic wave sources even if the size and number of elements that can be detected simultaneously in the acoustic wave detector are limited in the finally obtained biological information image. It is an object of the present invention to provide a biological information acquisition apparatus that can reconstruct a close image.

An object information acquiring apparatus according to the present invention includes an acoustic wave detector in which a plurality of elements that detect an acoustic wave generated from an object and convert it into an electrical signal are arranged, and the acoustic wave detector is moved from a first position to a second position. A subject information acquisition device comprising: a movement control means for moving to a position; and a signal processing device for reconstructing a subject information image based on the electrical signal, wherein the acoustic wave detector is the first position. After the acoustic wave is detected by the movement control means, the element is moved so that the element is positioned at the second position where the element is not positioned at the first position, and then the second An acoustic wave is detected at a position, and the movement width of the element from the first position to the second position is an integral multiple of the width of the element in the movement direction, and the signal processing device The electrical signal obtained at position 1 and the second position And combining the electrical signals, characterized in that to reconstruct the object information image from the combined signal.

  In the biological information acquisition apparatus of the present invention, even if the size and the number of elements that can be simultaneously measured in the acoustic wave detector are limited, the biological information that can reconstruct an image closer to the actual acoustic wave source distribution An acquisition device can be provided.

It is a schematic diagram which shows an example of a structure of the conventional biometric information acquisition apparatus. It is a schematic diagram which shows an example of a structure of the biometric information acquisition apparatus which can apply this invention. It is a schematic diagram which shows an example of a structure of the acoustic wave detector of the biological information acquisition apparatus which can apply this invention. It is an example of the moving method of the acoustic wave detector of the biological information acquisition apparatus which can apply this invention. (A) is an example of an acoustic wave generation source, (b) is an example of an image obtained without moving the acoustic wave detector, and (c) is an image obtained by the biological information acquisition apparatus of the present invention. It is an example.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows an embodiment of biometric information acquisition according to the present invention. Here, the best mode for carrying out the present invention will be described with reference to FIG. The biological information acquisition apparatus described in the present embodiment enables imaging of biological information for the purpose of diagnosis of malignant tumors, vascular diseases, and the like, and follow-up of chemical treatment. In the present invention, biological information is the distribution of acoustic wave sources, including the initial pressure distribution in the living body, or the optical characteristic value distribution derived therefrom, and the concentration distribution of substances constituting the living tissue obtained from the information. Show. For example, the substance concentration distribution is oxygen saturation.

  The biological information acquisition apparatus according to this embodiment includes a light source 11 that irradiates a subject 13 with light 12, an optical device 14 such as a lens that guides the light 12 emitted from the light source 11 to the subject 13, and light absorption such as blood vessels. An acoustic wave detector 17 that detects and converts an acoustic wave 16 generated when the body 15 absorbs a part of light energy into an electrical signal, an electronic control system 18 that amplifies or digitally converts the electrical signal, and a living body It comprises a signal processing device 19 that constructs an image relating to information, a display device 20 that displays the image, and a system 21 that controls movement of the acoustic wave detector 17.

  Note that an acoustic wave 16 is generated from the light absorber 15 in the living body by irradiating the subject with the pulsed light 12. This is because the temperature of the absorber rises due to the absorption of the pulsed light, the volume rises due to the temperature rise, and an acoustic wave is generated. Further, the time width of the light pulse at this time is preferably set to such a degree that the heat / stress confinement condition is satisfied in order to confine the absorbed energy in the light absorber 15 efficiently. Typically, it is several to several tens of nanoseconds. The generated acoustic wave 16 is detected by the acoustic wave detector 17, and the detected electrical signal is processed by the control system. The acoustic wave detector 17 is configured to measure the acoustic wave 16 at various places while moving mechanically by the movement control system 21. Further, the electrical signal is converted into a biological information image by a signal processing device 19 such as a PC and displayed on an image display device 20 such as a display.

  Next, the movement control method of the acoustic wave detector in the biological information acquisition apparatus of the present invention will be described. FIG. 3 is an example of the acoustic wave detector 17 of FIG. 2, and is a schematic view seen from the surface side in contact with the subject 13.

  In FIG. 3, 31 indicates the entire acoustic wave detector, and 32 indicates the element. In the acoustic wave detector 31 of FIG. 3, the elements 32 are arranged in a staggered manner (elements and gaps are alternately arranged). When the acoustic wave detector 31 having such an element arrangement is moved while being shifted by the width of the element in the movement direction (X direction), an apparent gap is formed in the element arrangement as shown in FIG. The number of elements is the same as the arrangement of elements without providing them. In addition, the space | gap said here is an area | region which cannot send an acoustic wave to an electrical system as an electrical signal, and the element which is not wired is also considered as a space | gap. In other words, the acoustic wave detector is apparently arranged in a packed element, but the unwired element becomes a gap because it cannot transmit an electrical signal to the 18 electronic control system. In FIG. 4, 33 is a detection region of the acoustic wave detector before movement (first position), and 34 is a detection region of the acoustic wave detector after movement (second position). Reference numeral 35 denotes an area where the acoustic wave detection area after the acoustic wave detector moves overlaps with the acoustic wave detection area before the movement.

  Note that the arrangement of the elements is not limited to the staggered arrangement shown here. For example, it may be a form in which elements and gaps are arranged in order for each row. If the number of elements is the same when the acoustic wave detector is moved and densely arranged without providing gaps, any arrangement is used. It doesn't matter. In other words, it is only necessary that the acoustic wave detectors are arranged so that the elements corresponding to the gap before the movement (first position) correspond to the elements after the movement (second position).

  Further, from the viewpoint of ease of image reconstruction, the gap is preferably an integer multiple of the element size, and the moving width of the acoustic wave detector is the element size (the element width in the moving direction). ) Is preferably an integer multiple of.

FIG. 5A shows an example of an initial acoustic wave source distribution on the acoustic wave detector. Here, 64 is an acoustic wave generation source. The acoustic wave generated from 64 is detected without movement control by the acoustic wave detector shown in FIG. 3, and the image is reconstructed using a conventional image reconstruction method such as a time domain algorithm or a Fourier domain algorithm. A conceptual diagram of the image is shown in FIG. In FIG.5 (b), 65 has shown the shape of the reconstructed acoustic wave generation source. Here, D _a represents the diameter of the acoustic wave source that is reconstructed. Next, FIG. 5C is a conceptual diagram of an image reconstructed by using the acoustic wave information before and after the movement of the acoustic wave detector of FIG. 3 by one element. Here again, the time domain method or the Fourier domain method, which is a conventional method, can be used as the reconstruction method. Note that the data before and after the movement are combined and treated as information in accordance with the position of each measuring element, and image reconstruction is performed. In the figure, 66 is the shape of the acoustic wave generating source is reconstructed, D _b represents the diameter of the acoustic wave source that is reconstructed. Comparing these, 66 is closer to the shape of 64 which is the actual acoustic wave generation source than 65, and the diameter is smaller. This is because the acoustic wave detector is moved by the width of the element so that the acoustic wave detection area is overlapped before and after the movement, and the apparent number of elements used when reconstructing an image can be increased (no gap) This is because the same signal input as the acoustic wave detector is possible. As a result, the image reconstruction system is improved, and the position and size of the acoustic wave generation source can be imaged with high accuracy even if the size and the number of elements of the acoustic wave detector are limited.

  In addition, when creating a large acoustic wave detector by arranging a plurality of small element groups, a boundary part that cannot detect acoustic waves is provided between the small element groups, but if this boundary part is configured as the gap part, The boundary can be enlarged, and manufacturing is facilitated.

  Furthermore, it becomes easy to irradiate light from the acoustic wave detector side arranged by arranging a light source with an optical fiber or the like in the gap. In the method of generating acoustic waves by irradiating the subject with light, if light is irradiated from the outside of the acoustic wave detector, if the acoustic wave detector is large, it becomes difficult to propagate the light directly below it, Decrease. On the other hand, if light can be irradiated from within the acoustic wave detection element as described above, light can be irradiated directly under the acoustic wave detector, which is effective in improving the quality of the reconstructed image.

  Next, this embodiment will be specifically described.

  In FIG. 2, the light source 11 is intended to irradiate light of a specific wavelength that is absorbed by a characteristic component among the components constituting the living body. However, the light source may be provided integrally with the biological information acquisition apparatus of the present invention, or may be provided separately from the light source. As the light source, at least one pulse light source capable of generating pulsed light on the order of several nanometers to several hundred nanoseconds is provided. In the case where the sound pressure of the acoustic wave to be detected may be small, it is not limited to the pulse light of the order described above, but may be light having a temporally changing intensity such as a sine wave. Although a laser capable of obtaining a large output is preferable as the light source, a light emitting diode or the like can be used instead of the laser. As the laser, various lasers such as a solid laser, a gas laser, a dye laser, and a semiconductor laser can be used.

  In the present embodiment, an example in which there is one light source 11 is shown, but a plurality of light sources may be used. In that case, a plurality of light sources that oscillate the same wavelength may be used in order to increase the irradiation intensity of the light that irradiates the living body. A plurality may be used. In addition, if the light source 11 can use a oscillating wavelength-convertible dye, OPO (Optical Parametric Oscillators), titanium sapphire, or alexandrite crystals, it is possible to measure the difference in optical characteristic value distribution depending on the wavelength. . Regarding the wavelength of the light source to be used, a region of 700 nm to 1100 nm, which is less absorbed in the living body, is preferable. However, when obtaining the optical characteristic value distribution of the living tissue relatively near the surface of the living body, it is also possible to use a wavelength region having a wider range than the above wavelength region, for example, a wavelength region of 400 nm to 1600 nm.

  Reference numeral 12 in FIG. 2 denotes light emitted from a light source, which can be propagated using an optical waveguide or the like. Although not shown in the drawing, an optical fiber is preferable as the optical waveguide. When using an optical fiber, it is possible to use a plurality of optical fibers for each light source to guide light to the surface of the living body, or to guide light from a plurality of light sources to a single optical fiber, All light may be guided to the living body using only one optical fiber. Reference numeral 14 in FIG. 2 denotes an optical component, which mainly means a mirror that reflects light, a lens that collects or enlarges light, or changes its shape. Any optical component may be used as long as the subject 13 is irradiated with the light 12 emitted from the light source in a desired shape. In general, it is preferable to spread light over a certain area rather than condensing light with a lens. In addition, it is preferable that the region where the subject is irradiated with light is movable. In other words, the biological information acquisition apparatus of the present invention is preferably configured so that light generated from the light source can move on the subject. By being movable, it is possible to irradiate light over a wider range. Further, it is more preferable that the region where the subject is irradiated with light (light irradiated to the subject) moves in synchronization with the acoustic wave detector. As a method of moving the region irradiated with light to the subject, the light source itself may be mechanically moved, although the moving mirror or the like may be used.

  The subject 13 is intended for diagnosis of human or animal malignant tumors or vascular diseases, or for the follow-up of chemical treatment, and so on if it is the subject of diagnosis such as breasts, fingers or limbs of the human body or animals. Can be used as a subject. The light absorber of the subject 13 indicates a substance having a high absorption coefficient in the subject. For example, if the human body is a measurement target, it is a malignant tumor containing hemoglobin, a blood vessel containing a lot of it, or a lot of new blood vessels.

  The acoustic wave detector 17 shown in FIG. 2 detects an acoustic wave generated from an object that has absorbed a part of the energy of light propagated in the subject and converts it into an electrical signal. The acoustic wave detector according to the present invention can be any acoustic wave as long as it can detect acoustic waves such as a transducer using a piezoelectric phenomenon, a transducer using optical resonance, and a transducer using a change in capacitance. A detector may be used.

  The acoustic wave detector in the biological information acquisition apparatus of the present invention is preferably one in which elements are two-dimensionally arranged as shown in FIG. By using such a two-dimensional array element, acoustic waves can be detected simultaneously at a plurality of locations, the detection time can be shortened, and influences such as vibration of the subject can be reduced. In addition, although not shown, it is desirable to use an acoustic impedance matching agent such as gel or water for suppressing reflection of acoustic waves between the acoustic wave detector 17 and the subject.

  The movement control system 21 of the acoustic wave detector shown in FIG. 2 uses a drive stage and a stage controller that use a normal motor or the like, but any type can be used as long as the acoustic wave detector 17 can be operated two-dimensionally. It doesn't matter.

  The acoustic wave detector of the present invention is positioned and moved in a step-and-repeat manner that repeats stationary → detection → movement, and detects an acoustic wave in a stopped state. It is preferable to receive the acoustic wave a plurality of times in a stopped state at this one position. By using the average value of a plurality of signals, an image with less noise can be reconstructed.

  The electronic control system 18 of FIG. 2 amplifies the electrical signal obtained from the acoustic wave detector 17 and converts it from analog to digital. 2 may store any data obtained from the electronic control system, and any data can be used as long as it can be converted into image data of an optical characteristic value distribution by a calculation means. For example, a computer that can analyze various data can be used. As a data analysis method (image reconstruction method), a filter-corrected back projection method, a Fourier transform method, a spherical radon transform method, a synthetic aperture method, or the like used in normal photoacoustic tomography can be used. Any image display apparatus of FIG. 2 can be used as long as it can display the image data generated by the signal processing apparatus. For example, a liquid crystal display can be used.

  When light having a plurality of wavelengths is used, the absorption coefficient distribution in the subject is calculated by the above system for each wavelength. It is also possible to image the concentration distribution of the substances that make up the living body by comparing these values with the wavelength dependence of the substances that make up the living tissue (glucose, collagen, oxidized / reduced hemoglobin, etc.) It is.

DESCRIPTION OF SYMBOLS 11 Light source 12 Light 3, 13 Subject 14 Optical component 2, 15, 35, 64 Light absorber or initial pressure distribution 5, 16, Acoustic wave 1, 17, 31 Acoustic wave detector 18 Electronic control system 19 Signal processing apparatus 20 Image display device 21 Movement control system 4 Imaging area 32 Element 33 Detection area before moving acoustic wave detector 34 Detection area after moving acoustic wave detector 65, 66 Imaged initial pressure distribution

Claims (6)

An acoustic wave detector in which a plurality of elements for detecting an acoustic wave generated from a subject and converting it into an electrical signal are arranged; a movement control means for moving the acoustic wave detector from a first position to a second position; A subject information acquisition device having a signal processing device for reconstructing a subject information image based on an electrical signal,
The acoustic wave detector detects an acoustic wave at the first position, and the element is positioned at the second position where the element is not positioned at the first position by the movement control means. And after detecting the acoustic wave at the second position,
The movement width of the element from the first position to the second position is an integer multiple of the width of the element in the movement direction;
The signal processing apparatus combines the electrical signal obtained at the first position and the electrical signal obtained at the second position, and reconstructs an object information image from the combined signal. Subject information acquisition apparatus. Wherein the first position movement width in the second position, the test object information acquisition apparatus according to claim 1, characterized in that the same as the width of the element in the movement direction. The acoustic wave is subject body information acquiring apparatus according to the light generated from the light source in claim 1 or 2, characterized in that generated by irradiating the subject. Test body information acquiring apparatus according to claim 3, characterized in that the light generated from the light source is configured to move the object above. Test body information acquiring apparatus according to claim 4, wherein the acoustic wave detector in synchronism with the region in which the light generated from the light source is irradiated on the subject is moving. The acoustic wave detector, the test body information acquiring apparatus according to any of claims 1 to 5, characterized in that by arranging the element in two dimensions.

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