JP2010088496A - Biological information acquisition apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biological information acquisition apparatus highly accurately imaging the position and size of an absorbent body. <P>SOLUTION: The biological information acquisition apparatus includes an acoustic wave detector wherein a plurality of elements for detecting acoustic waves generated by irradiating an object with light and converting them to electric signals are arrayed, a movement control means for moving the acoustic wave detector, and a signal processor for reconfiguring a biological information image on the basis of the electric signals. The acoustic wave detector detects the acoustic waves at a first position, and the acoustic wave detector is moved to a second position having a region overlapping with the first position by the movement control means and detects the acoustic waves at the second position. By the signal processor, the electric signals obtained at the first and second positions are utilized in the overlapping region and the biological information image is reconfigured. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a biological information acquisition apparatus.

  In general, imaging apparatuses 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. Detect at multiple locations. Then, the obtained signal is subjected to mathematical analysis processing to visualize information related to the optical characteristic value inside the subject. 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.

As an example of this photoacoustic tomography, Patent Document 1 discloses a method of reconstructing an image by moving a light irradiation region and an acoustic wave detector.
USP 5840023

  In general, in photoacoustic tomography, an acoustic wave is measured with respect to a subject at various points on a closed space surface surrounding the whole subject, particularly a spherical measurement surface. 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 over the entire closed space surface surrounding the 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 type measurement system, if an acoustic wave can be measured in a sufficiently large region (ideally an infinite surface) with respect to the region 4 for visualizing the initial pressure distribution, the distribution of the acoustic wave source is almost reproduced. It is mathematically known that it can be done. However, if the size of the acoustic wave detector 1 and the number of detector elements included in the acoustic wave detector 1 are increased in order to increase the measurement area of the acoustic wave, the electronic control system for controlling the size of the detector becomes large. As a very expensive system. Therefore, as in Patent Document 1, a method of detecting an acoustic wave in an apparently large area by moving an acoustic wave detector has been proposed. However, such a method has a problem that a positional deviation occurs in an obtained image due to a limitation of a region where light can be irradiated and accuracy of a moving machine.

  Therefore, in view of the above-described problems, the present invention corrects a positional shift so that a biological information image finally obtained can reproduce an image closer to actual biological information even when the acoustic wave detector is moved. An object is to provide an information acquisition device.

  The biological information acquisition apparatus of the present invention includes an acoustic wave detector in which a plurality of elements that detect an acoustic wave generated from a subject and convert it into an electrical signal, a movement control unit that moves the acoustic wave detector, and the electrical A biological information acquisition device having a signal processing device for reconstructing a biological information image based on a signal, wherein the acoustic wave detector detects an acoustic wave at a first position, and the movement control means detects the first wave. The acoustic wave is detected at the second position after moving to a second position having an area overlapping with a partial area of the first position, and the signal processing device detects the first and second positions. The biological information image in the overlapping area is reconstructed using the electrical signal obtained in step (b).

  By providing an overlapping area in the detection area of the acoustic wave detector before and after the movement, it is possible to provide a biological information acquisition apparatus that corrects positional deviation and reconstructs an image closer to actual biological information.

  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, it is preferable to know the time width of the light pulse at this time to such an extent that the heat / stress confinement condition is satisfied in order to efficiently confine the absorbed energy in the light absorber 15. 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 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. The acoustic wave detector 31 is configured by arranging a plurality of elements 32 that detect acoustic waves and convert them into electric signals. Here, an example is shown in which an acoustic wave detector is configured by two-dimensionally arranging M × N elements. The acoustic wave detector 31 repeats stationary → measurement → movement by the movement control system 21 in FIG. 2, and moves by positioning in a step-and-repeat manner. As a specific moving method, as shown in FIG. 4A, the acoustic wave detector is moved in one direction (X direction) to complete the detection of one stripe region, and then the X direction. A method of moving to a direction orthogonal to the direction (Y direction) and detecting the adjacent stripe region again can be considered. Alternatively, as shown in (b), a method of detecting in the X direction and the Y direction in order and moving in a spiral shape from the outside to the inside or from the inside to the outside may be used. That is, when the elements are arranged in two dimensions, the acoustic wave detector moves in the element arrangement direction (X direction or Y direction).

  As shown in FIG. 5, the biological information acquisition apparatus according to the present invention is characterized in that the detection area of the acoustic wave detector before and after the movement has an overlapping area. In FIG. 5, 33 is the detection area of the acoustic wave detector before the movement (first position), 34 is the detection area of the acoustic wave detector after the movement (second position), and 35 is the area before and after the movement. This is an area where the detection areas of the acoustic wave detector overlap. By having such overlapping regions, it is possible to correct the positional deviation. For example, an image immediately above the overlapping area is formed using data measured at the first position. Similarly, an image immediately above the overlapping area is constructed using data measured at the second position. In principle, the images must be the same, but if the measurement position is shifted due to the vibration of the subject or the mechanical accuracy of the moving mechanism, an image shift occurs. As a result, when the difference between the two images is taken, if there is a movement shift, an image corresponding to the shift amount is generated. By analyzing the image, the deviation of the measurement position can be calculated. Then, if the image reconstruction is performed with the data at the second position in consideration of the shift amount, the image shift can be reduced.

  FIG. 6A shows an example of an initial sound pressure distribution distributed on the acoustic wave detector, and 36 indicates an acoustic wave generation source. FIG. 6A shows a three-dimensionally distributed acoustic wave source projected onto the acoustic wave detector. FIG. 6B shows a conceptual diagram of an image obtained when an image is reconstructed by a conventional method that does not have a region where the initial pressure distribution overlaps the detection region. As shown in FIG. 6B, image misalignment may occur at the boundary of the image reconstruction area due to the vibration of the subject or the mechanical accuracy of the moving mechanism.

  On the other hand, FIG. 6C shows a conceptual diagram of an image obtained when an overlapping area is provided in the detection area before and after movement. As shown in FIG. 6C, in the case where the detection region overlaps with the detection region before and after the movement, the acoustic wave detection signal before and after the movement can be used in the overlapping region 35. By performing image reconstruction, it is possible to correct the positional deviation of the image, and an image closer to the actual initial pressure distribution can be obtained. In addition to the above-described method, the positional deviation correction method includes a method of reconstructing images from separate electrical signals obtained at the first and second positions, and averaging the images. A method of reconstructing the image after averaging the separate electrical signals obtained at the first and second positions is conceivable. As an image averaging method, each voxel value on the overlap measurement region may be added and divided by two. Similarly, the averaging of the electrical signals may be performed simply by averaging the signals obtained from the elements in the overlapping measurement region. In such a method of averaging signals or images, the amount of positional deviation is also averaged, so image deviation is reduced even in an image obtained by reconstruction using the data.

  As described above, by overlapping the areas where the acoustic wave detector detects acoustic waves, it is possible to correct the positional deviation and reconstruct an image closer to actual biological information.

  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 that absorbs less 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. Any acoustic wave detector may be used 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.

  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 of FIG. 2 uses a drive stage and a stage controller using a normal motor or the like. However, if the acoustic wave detector 17 can be operated two-dimensionally (X direction or Y direction). Anything can be used. As described above, it is necessary to include a control mechanism in which the acoustic wave detection area after the acoustic wave detector 17 moves has an area that overlaps the acoustic wave detection area before the movement. It is also possible to use a simple controller. The acoustic wave detector is moved so as to have at least one of the X direction and the Y direction as the overlapping region, but it is preferable to move so as to have an overlapping region in both the X direction and the Y direction.

  Moreover, it is preferable that the single movement width of the acoustic wave detector 17 is an integral multiple of the width of one element in the movement direction. That is, as shown in FIG. 3, when an element is M × N two-dimensional array and the area of one element is S, the overlapping area when the acoustic wave detector moves in the X direction is S × N × i (i is an integer from 1 to M-1). Similarly, when moving in the Y direction, it is represented by S × M × j (j is an integer from 1 to N−1). By moving in this way, the positional deviation can be corrected more accurately.

  The acoustic wave detector of the present invention is positioned and moved in a step-and-repeat manner that repeats stationary → moving, 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. Next, the image display apparatus shown in FIG. 2 can be used as long as it can display 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.

  By using the biological information acquisition device shown in such an embodiment, an image closer to actual biological information can be reconstructed.

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. It is a schematic diagram which shows the area | region which overlaps before and behind the movement 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 by a conventional biological information acquisition device, and (c) is an example of an image obtained by the biological information acquisition device of the present invention. is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Light source 12 Light 3, 13, 43 Subject 14 Optical component 2, 15, 36 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 35 Area where acoustic wave detector detection areas overlap before and after movement 37 Imaging Initial pressure distribution

Claims (8)

An acoustic wave detector in which a plurality of elements that detect acoustic waves generated from the subject and convert them into electrical signals are arranged, movement control means for moving the acoustic wave detectors, and reconstructing a biological information image based on the electrical signals A biological information acquisition device having a signal processing device,
The acoustic wave detector detects the acoustic wave at a first position, and moves to a second position having an area overlapping with a partial area of the first position by the movement control unit. Detecting the acoustic wave at a second position;
The biometric information acquisition apparatus, wherein the signal processing apparatus reconstructs a biometric information image in the overlapping region using electrical signals obtained at the first and second positions.   2. The biological information according to claim 1, wherein a moving width of the acoustic wave detector from the first position to the second position is an integral multiple of a width of the one element in a moving direction. Acquisition device.   The biological information acquisition apparatus according to claim 1, wherein the acoustic wave is generated by irradiating a subject with light generated from a light source.   The biological information acquisition apparatus according to claim 3, wherein the light generated from the light source is configured to be movable on the subject.   The biological information acquisition apparatus according to claim 4, wherein the acoustic wave detector moves in synchronization with a region in which light generated from the light source is irradiated on a subject.   The biological information acquisition apparatus according to claim 1, wherein the acoustic wave detector is formed by two-dimensionally arranging the elements.   2. The signal processing device according to claim 1, wherein each of the biometric information images is reconstructed from separate electrical signals obtained at the first and second positions, and the biometric information images are averaged. The biological information acquisition apparatus according to any one of 6.   The biological information according to claim 1, wherein the signal processing device reconstructs a biological information image by averaging separate electrical signals obtained at the first and second positions. Acquisition device.

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