JP2014144109A - Subject information acquisition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a subject information acquisition device capable of accurately aligning a photoacoustic image with the actual position of a subject in photoacoustic imaging without complicating the device.SOLUTION: A subject information acquisition device comprises: light emitting sections 18 and 19 which emit light from a light source; a member 11 which is disposed between a subject 10 and the light emitting sections 18 and 19 and transmits light; a light absorber disposed on the member; a probe 15 which receives acoustic waves generated by the subject 10 and the light absorber irradiated with the light from the light emitting sections 18 and 19 and converts the acoustic waves into electric signals; and a signal processing section 16 which generates image data on an interior of the subject and the light absorber using the electric signals.

Description

  The present invention relates to a subject information acquisition apparatus.

  In the medical field, imaging apparatuses using X-rays, ultrasound, and MRI (nuclear magnetic resonance method) are used. In the medical field, research on an optical imaging apparatus that obtains in-vivo information by propagating light irradiated from a light source such as a laser into a subject such as a living body and detecting the propagating light or the like has been advanced. As one of such optical imaging techniques, a photoacoustic imaging technique has been proposed.

  When pulse light from a light source is irradiated on a subject, a phenomenon in which an acoustic wave is generated from a living tissue that has absorbed light energy is called a photoacoustic effect. Photoacoustic imaging is a technique that detects acoustic waves generated by the photoacoustic effect at a plurality of locations, analyzes the signals, and visualizes information related to optical characteristic values inside the subject. Thereby, it is possible to obtain an optical characteristic value distribution in the subject, particularly a light energy absorption density distribution.

  In addition, application of photoacoustic imaging technology to lesions such as breast cancer inside a living body is also being studied. In this case, light is strongly scattered in the living body and greatly attenuated in the depth direction. Therefore, in Non-Patent Document 1, the breast is pressed during measurement to reduce the thickness.

  On the other hand, the development of photoacoustic microscopes that increase the resolution of photoacoustic imaging by converging sound or condensing pulsed light is also underway. In Non-Patent Document 2, a resolution equivalent to the convergence spot diameter at the focal point of the ultrasonic wave is obtained by converging the ultrasonic wave using a focus transducer and condensing the light at the focal point of the ultrasonic wave.

S. Manohar et al., “Region-of-interest breast studies using the Twente Photoacoustic Mammoscope (PAM)”, Proc. Of SPIE Vol. 6437 643702-1 Nature Protocols vol.2 No.4 797-804 (2007); H.F.Zang et al.

  In photoacoustic imaging, accurate alignment of the obtained photoacoustic image may be necessary. For example, in clinical practice, a lesion is extracted while viewing a photoacoustic image, or an accurate position of the lesion is specified when puncturing is performed. In addition, when monitoring the pharmacokinetics of a photoacoustic molecular probe or the like in a subject, accurate information such as the position of a lesioned part and the position of probe accumulation is required.

  However, Non-Patent Document 1 and Non-Patent Document 2 do not describe such exact alignment. For this reason, it has been difficult for the conventional photoacoustic imaging apparatus to accurately position the photoacoustic image and the actual subject image and to accurately specify the measurement location, the lesion, and the like of the subject.

  In order to perform such accurate alignment, a marker (hereinafter referred to as an alignment mark) that can align the scan range with the actual subject position is effective.

  The present invention has been made in view of the above problems, and an object thereof is to perform accurate alignment between a photoacoustic image and an actual subject position without complicating the apparatus in photoacoustic imaging. is there.

The present invention employs the following configuration. That is,
A light emitting unit that emits light from a light source;
A light transmitting member disposed between the subject and the light emitting unit;
A light absorber disposed on the member;
A probe that receives an acoustic wave generated from the subject and the light absorber irradiated with light from the light emitting unit and converts the acoustic wave into an electrical signal;
Using the electrical signal, a signal processing unit that generates image data of the subject and the light absorber;
A subject information acquisition apparatus characterized by comprising:

  According to the present invention, in photoacoustic imaging, accurate alignment between a photoacoustic image and an actual subject position can be performed without complicating the apparatus.

1 is a diagram illustrating a configuration of a biological information imaging apparatus according to Embodiment 1. FIG. The figure which shows a grid-shaped light absorber. The figure which shows the example of the pattern of a light absorber. FIG. 5 is a diagram illustrating a configuration of a biological information imaging apparatus according to a second embodiment. FIG. 6 is a diagram for explaining image display in a third embodiment. 10 is a flowchart showing processing in the third embodiment. FIG. 10 is a diagram illustrating a configuration of a biological information imaging apparatus according to a fourth embodiment. FIG. 9 is a diagram for explaining image display in a fourth embodiment. FIG. 10 is a diagram for explaining specific processing in the fourth embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described below should be changed as appropriate according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the following description.

  In the present invention, the acoustic wave includes an elastic wave called a sound wave, an ultrasonic wave, a photoacoustic wave, and an optical ultrasonic wave. The subject information acquisition apparatus of the present invention utilizes a photoacoustic effect that receives acoustic waves generated in a subject by irradiating the subject with light (electromagnetic waves) and acquires characteristic information in the subject. Device.

  The object information in the object information acquisition apparatus is the initial sound pressure of the acoustic wave generated by the light irradiation, the light energy absorption density or absorption coefficient derived from the initial sound pressure, or the concentration of the substance constituting the tissue. This is characteristic information reflecting the above. The concentration of the substance is, for example, the concentration of oxyhemoglobin and reduced hemoglobin, oxygen saturation, or the like. The characteristic information may be distribution information of each position in the subject instead of numerical data. That is, an initial sound pressure distribution, an absorption coefficient distribution, an oxygen saturation distribution, and the like may be generated as image data.

In the following description, a biological information imaging apparatus for imaging characteristic information in a subject that is a living body will be described as an example of the subject information acquiring apparatus. However, the measurement object of the present invention is not limited to a living body. Further, the subject information acquisition apparatus may not have an image display apparatus, and may be configured to generate image data and transmit it to the outside.

<Embodiment 1>
FIG. 1 shows a configuration example of a biological information imaging apparatus in the present embodiment. The apparatus includes a light transmissive member 11 and a holding member 12 for holding a living body 10 as a subject. The apparatus also includes light emitting units 18 and 19 that irradiate the living body 10 with the irradiation light 13. The apparatus also includes a probe 15 that detects acoustic waves and converts them into electrical signals. The apparatus also includes a signal processing unit 16 that generates image data. The image display unit 17 is an image display device that displays a processing result by the signal processing unit.

FIG. 2A is a view of the light transmissive member 11 viewed from the side opposite to the subject. The light transmissive member 11 is provided with a light absorber 21 in a grid shape on the surface that does not contact the living body 10. The light absorber 21 is an alignment mark that absorbs the irradiation light 13 and generates a photoacoustic wave.
Here, black ink is used as the material of the light absorber 21. However, the light absorber is not limited to this, and any light absorber can be used as long as it absorbs the irradiation light 13 irradiated on the living body 10 and generates a photoacoustic wave. Further, printing is suitable as means for arranging the light absorber 21 on the light transmissive member 11, but other fixing methods may be used.

The probe 15 detects a photoacoustic wave generated from the light absorber 21 or the light absorber 14 (blood, tumor, etc.) in the living body and converts it into an electrical signal. The signal processing unit analyzes image signals derived from the light absorbers 14 and 21 to perform image reconstruction, and generates image data that is original data for displaying an image to the user.
The obtained image data is displayed on the image display unit 17. At this time, a maximum value projection method (Maximum Intensity Projection: hereinafter referred to as MIP) using the maximum value on the projection line as a pixel value is suitable. Thereby, the image which the grid overlapped on the photoacoustic image of a biological body is displayed. However, any method other than MIP may be used as long as image data derived from both light absorbers can be superimposed and displayed at the same time.

  FIG. 2B is a displayed MIP image. On the monitor 22, a grid-like photoacoustic image 23 showing the light absorber 21 and a photoacoustic image 24 showing the light absorber 14 in the living body are superimposed. By using this grid as an alignment mark, accurate alignment between the photoacoustic image and the actual subject position can be performed.

  Moreover, it is preferable that the image display unit 17 simultaneously displays the image data and the captured image of the subject and the light absorber acquired in advance. Therefore, the photoacoustic imaging apparatus may include an imaging unit, or may be configured to receive a captured image from the outside. In the former case, the imaging means is an image acquisition unit, and in the latter case, the communication system is an image acquisition unit.

  If only the grid is to be erased from the displayed photoacoustic image, the image data at the grid position may be erased from the image data obtained by the image reconstruction and displayed in MIP. Alternatively, the photoacoustic wave generated from the light absorber 21 arrives at the probe 15 later than the photoacoustic wave generated from the living body 10, and therefore, after the signal that is later in time is cut from the electrical signal, the image is displayed. Reconfiguration may be performed.

The arrangement pattern of the light absorbers 21 that are alignment marks is not limited to a grid. FIG. 3 shows an example of the arrangement pattern.
FIG. 3A shows an example in which dot-like light absorbers 31 are arranged at equal intervals on the light transmissive member 11. From the positional relationship between the point-like photoacoustic image and the photoacoustic image showing the light absorber 14 in the living body, the position of the light absorber 14 in the subject can be easily specified.
FIG. 3B shows an example in which a grid-shaped light absorber 32 is disposed on the light transmissive member 11, and numbers (reference numeral 33) corresponding to the respective positions are disposed at intersections of the grid. These can be arranged by printing. By arranging numbers in this way, the position can be easily identified even when the scan range is wide.
FIG. 3C is an example in which the light absorber 34 is printed on the light transmissive member 11 in advance so as to correspond to the assumed contour of the living body. Thereby, the positional relationship between the living body holding position and the scan range can be compared on the photoacoustic image.

  In addition to these patterns, it is possible to use a pattern of the light absorber 21 corresponding to each subject. It is also possible to use a light absorber 21 on which a scale display or the like is printed. Further, the light absorber 21 is not necessarily arranged over the entire light transmissive member 11. If the light absorber 21 is disposed only within the range corresponding to the measurement region of the subject in the light transmissive member 11 or only within the range in which the subject is orthogonally projected onto the light transmissive member. It ’s enough.

  The light absorber 21 is preferably provided on the opposite surface of the light transmissive member 11 from the subject. However, it may be provided on the same surface as the subject or in the light transmissive member 11. When the light absorber 21 is disposed on the surface where the light transmissive member 11 and the subject are in contact with each other, the light absorber 21 is preferably one that is sparingly soluble in water.

  The light transmissive member 11 preferably has high light transmittance and high durability against light. For example, glass or acrylic can be used as such a material. If a flat member is used as the light transmissive member, the shape of the subject surface can be stabilized and image reconstruction can be facilitated.

The holding member 12 preferably has high light transmittance and high durability against light. Furthermore, it is preferable that the acoustic wave has a small attenuation and has an acoustic impedance close to that of a living body. For example, polymethylpentene can be used as such a material.
Further, it is desirable to use an acoustic coupling medium for suppressing reflection of acoustic waves between the holding member 12 and the living body 10 and between the holding member 12 and the probe 15. For example, an impedance matching gel can be used.

  Hereinafter, the apparatus configuration will be described in detail. In the description, with respect to the living body 10, the holding member 12 side on which the probe 15 is disposed is referred to as a probe side, and the light transmissive member 11 side is referred to as a non-probe side.

  As the irradiation light 13, light having a wavelength with a characteristic that is absorbed by a specific component among components constituting the living body 10 is used. In this embodiment, the irradiation light 13 is irradiated from both sides of the light emitting unit 19 on the probe side and the light emitting unit 18 on the non-probe side, but it is also possible to irradiate only from the light emitting unit 18. is there. In addition, although irradiation is performed from both sides of the probe in the irradiation from the light emitting unit 19, it is sufficient that light is irradiated on the surface of the living body 10 positioned in front of the probe 15, for example, one side of the probe You may irradiate from.

A light guide such as an optical bundle fiber or a mirror that guides light emitted from the light source to the living body can be used as the light emitting units 18 and 19. Alternatively, a light source may be arranged in the light emitting unit 18. The irradiation light 13 is preferably pulsed light, particularly preferably having a pulse width on the order of several nanometers to several hundred nanoseconds.
As a light source for generating the irradiation light 13, a laser is preferable. As the laser, various lasers such as a solid laser, a gas laser, a dye laser, and a semiconductor laser can be used. Further, a light emitting diode or the like may be used instead of the laser. If a dye capable of converting the oscillation wavelength, OPO (Optical Parametric Oscillators), or titanium sapphire laser is used, it is possible to measure the difference in the 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, it is also possible to use a wavelength range wider than the above wavelength range, for example, a wavelength range of 400 nm to 1600 nm, and a terahertz wave, microwave, and radio wave range.
In addition, the light source of the irradiation light 13 can be scanned along the surface of the living body 10.

  As the probe 15, any acoustic wave detector can be used as long as it can detect an acoustic wave signal, such as a transducer using a piezoelectric phenomenon, a transducer using optical resonance, or a transducer using a change in capacitance. May be used. The probe 15 may be configured to scan along the surface of the subject 10 like the light source 13. A wide range can be measured by scanning the subject synchronously.

In the present embodiment, the array type probe 15 in which the receiving elements are arranged in a two-dimensional array is shown. However, the present invention is not limited to such an arrangement, and acoustic waves are generated at a plurality of locations. Should just be comprised so that detection is possible. That is, since the same effect can be obtained if acoustic waves can be detected at a plurality of locations, a probe (single transducer) having one receiving element may be scanned on the surface of the holding member 12.
When the electrical signal obtained from the probe 15 is small, it is preferable to amplify the signal intensity using an amplifier.

Based on the electrical signal obtained from the probe 15, the signal processing unit 16 determines the position and size of the light absorber 14 in the living body, or an optical characteristic value distribution such as a light absorption coefficient or a light energy deposition amount distribution. The optical characteristic value distribution of the light absorber 22 on the light transmissive member 11 is calculated.
As a reconstruction algorithm for obtaining an optical characteristic value distribution from the obtained electrical signals at a plurality of positions, universal back projection, phasing addition, and the like are conceivable. When using these algorithms, in this embodiment, it is necessary to consider the refraction of acoustic waves and the change in sound speed caused by the holding member 12 positioned between the living body 10 and the probe 15.

The signal processing unit 16 may store any intensity of the acoustic wave and its temporal change, and any signal can be used as long as it can be converted into optical characteristic value distribution data by the calculation means.
In addition, when multiple wavelengths of light are used, the optical coefficients in the living body are calculated for each wavelength, and those values are specific to the substances that make up the living tissue (glucose, collagen, oxidized / reduced hemoglobin, etc.) Compare with the wavelength dependence of. Thereby, it is also possible to image the concentration distribution of the substance constituting the living body.

  It is preferable that the image display unit 17 simultaneously displays the image data and the captured image of the subject and the light absorber acquired in advance. The captured image may be acquired after calculating the image data. The image display unit 17 may be a component of the device or an external component connected to the device.

  By using such a biological information imaging apparatus, accurate alignment between the photoacoustic image and the actual subject position can be easily performed without complicating the apparatus.

<Embodiment 2>
FIG. 4 shows a configuration example of the biological information imaging apparatus in the present embodiment. The difference from the first embodiment is that the apparatus is a container-shaped holding portion 50, 5 instead of the light transmissive member 11 and the holding member 12.
1 and the probe 15 is provided inside the holding portion 51. Constituent elements common to the apparatus shown in FIG. 1 are denoted by the same reference numerals, and only different portions will be described below.

In the present embodiment, the living body 10 can be held by a film by using the container-like holding portions 40 and 41. Since the member between the living body 10 and the probe 15 is formed into a film shape, multiple reflection of acoustic waves by the holding unit is suppressed, so that high-definition imaging is possible.
In addition, since multiple reflections are unlikely to occur, it is possible to arrange a light absorber serving as an alignment mark on the probe side. It is also possible to arrange a light absorber serving as an alignment mark on the holding member 12 on the probe side in FIG. However, in that case, the photoacoustic wave generated from the light absorber is multiple-reflected in the holding member 12 to deteriorate the in-vivo image.

  The holding parts 40 and 41 hold the living body 10 so as to sandwich the living body 10. The bottom surface of the holding unit 40 (the surface in contact with the living body) is a light transmissive film 42. In the present embodiment, the film 42 is considered as a member that transmits light of the present invention. The bottom surface of the holding unit 41 (the surface in contact with the living body) is also a light transmissive film 43. The light-transmitting film 43 is preferably one that transmits sound, and for example, a polyethylene film can be used. The container of the holding part 41 is filled with an acoustic coupling medium 44 such as water or castor oil.

  The light transmissive film 43 is provided with a light absorber 21 as an alignment mark as shown in FIGS. The light absorber 21 absorbs the irradiation light 13 and generates a photoacoustic wave. The light absorber 21 can be manufactured by fixing a material such as black ink to a film by a technique such as printing.

Since irradiation light, a probe, a signal processing unit and an image display unit, a signal processing method and an image display method can be the same as those in the first embodiment, detailed description thereof is omitted. In the present embodiment, the holding unit 40 may be a light transmissive plate member.
Furthermore, although the light absorber is provided on the light transmissive film 43 in the present embodiment, the same effect can be obtained by providing the light absorber on the light transmissive film 42.
By using the biological information imaging apparatus shown in such an embodiment, accurate alignment between the photoacoustic image and the actual subject position can be easily performed without complicating the apparatus. .

<Embodiment 3>
The overall configuration of the biological information imaging apparatus according to the third embodiment, the irradiation light, the probe, the signal processing unit, and the image display unit can be the same as those in each of the above embodiments, and detailed description thereof is omitted. To do. Hereinafter, description will be made with reference to FIG.

  FIG. 5A is a view of the light transmissive member 11 viewed from the side opposite to the subject. A grid-shaped light absorber 51 is arranged. Components that are the same as those shown in FIG. 2 are given the same reference numerals, and detailed descriptions thereof are omitted.

  A light source having a variable wavelength is used. For example, a titanium sapphire laser or an OPO laser can be used. Moreover, the control means for switching a wavelength is provided. A plurality of lasers that emit light of different wavelengths may be switched and used. The material of the light absorber 51 and the wavelength of the irradiation light are set so that the light wavelength region absorbed by the light absorber 14 in the living body and the light wavelength region absorbed by the light absorber 51 are different.

A flowchart of the present embodiment is shown in FIG.
In step S601, the light source irradiates the held living body 10 with the irradiation light 13 having the first wavelength (λ1) absorbed by the light absorber 14 in the living body.
In step S602, the probe 15 detects the photoacoustic wave generated from the light absorber 14 and converts it into an electrical signal.
In step S603, the signal processing unit 16 generates first image data such as optical characteristic value distribution information from the electrical signal. When the first image data is displayed, a photoacoustic image 52 of the light absorber in the living body is imaged as shown in FIG.

In step S604, the wavelength of the irradiation light 13 is switched to the second wavelength (λ2) absorbed by the light absorber 51 on the light transmissive member 11, and the irradiation light 13 is irradiated.
In step S605, the probe 15 detects the photoacoustic wave generated from the light absorber 51 and converts it into an electrical signal.
In step S606, the signal processing unit 16 generates second image data such as optical characteristic value distribution information from the electrical signal. When the second image data is displayed, a photoacoustic image 53 of the light absorber on the transmissive member 11 is imaged as shown in FIG.

  In step S607, the first image data and the second image data are superimposed and displayed. As a result, as shown in FIG. 6D, a grid-like photoacoustic image 53 showing the light absorber 51 on the light transmissive member 11 and a photoacoustic showing the light absorber 14 in the living body are displayed on the monitor 54. The image 52 is displayed as a superimposed MIP image.

Moreover, it is preferable that the image display unit 17 simultaneously displays the image data and the captured image of the subject and the light absorber acquired in advance. By using the grid displayed at this time as an alignment mark, the photoacoustic image and the actual subject can be accurately aligned (S608).
In this embodiment, only one wavelength (λ1) is used when generating an in-vivo image. However, by using a plurality of wavelengths, it is possible to image the concentration distribution and oxygen saturation of the substance in the living body. Conversely, as the light absorber on the light transmissive member, one that absorbs light in a wavelength region similar to the wavelength absorbed by the light absorber in the living body may be used.

  By using such a biological information imaging apparatus, accurate alignment between the photoacoustic image and the actual subject position can be easily performed without complicating the apparatus.

<Embodiment 4>
FIG. 7 shows a configuration example of the biological information imaging apparatus in the present embodiment. This apparatus can image the optical characteristic values in the living body and the concentration distribution of substances constituting the living tissue with high resolution for the diagnosis of tumors, vascular diseases and the like, and the follow-up of chemical treatment.

  The subject to be measured is the living body 70. It is preferable to include a subject holding base 701 on which the living body 70 is arranged. The apparatus includes a light emitting unit 71 and a water tank 72. Irradiation light 74 is emitted from the light emitting portion 71. The apparatus preferably includes an optical component 75 that collects the irradiation light in the living body. An acoustic coupling medium 79 is disposed in the water tank 72. The bottom surface of the water tank 72 is a light transmissive film 73. The light transmissive film 73 includes a light absorber that serves as an alignment mark.

The apparatus also includes a focus type ultrasonic probe 76 that detects a photoacoustic wave generated when light is irradiated on a light absorber inside or outside the living body and converts it into an electric signal. The focusing position of the irradiation light and the focus position of the focus type ultrasonic probe 76 are arranged so as to match.
Moreover, the signal processing part 77 and the image display part 78 are provided similarly to the said embodiment.

FIG. 8A shows a film 81 (corresponding to reference numeral 73 in FIG.
It is the figure seen from the opposite side to the surface which contacts 0 (equivalent to the code | symbol 70 of FIG. 7), ie, the upper surface. The light transmissive film 81 is provided with a light absorber 82 serving as an alignment mark in a grid shape. The light absorber 82 absorbs the irradiation light 13 and generates a photoacoustic wave. For example, black ink fixed by printing can be used.

  The focus type probe 76 is a probe (single transducer) having one receiving element designed to converge an ultrasonic wave, and a light absorber 82 and a light absorber in a living body such as blood. The photoacoustic wave generated from 83 is detected and converted into an electric signal. By scanning the focus type probe 76 and the irradiation position of the irradiation light 74 in synchronization, the living body can be measured two-dimensionally. In FIG. 8A, a range 84 surrounded by a solid line is two-dimensionally scanned.

When displaying a two-dimensional scan result, a maximum value projection method (Maximum Intensity Projection: hereinafter referred to as MIP) using a maximum value on a projection line as a pixel value can be used. Thereby, the image which the grid overlapped on the photoacoustic image of a biological body is displayed. Any method other than MIP may be used as long as the light absorber in the living body can be displayed simultaneously with the alignment mark.
FIG. 8B is a displayed MIP image. On the monitor 85, a grid-like photoacoustic image 86 showing the light absorber 82 and a photoacoustic image 87 showing the light absorber 83 in the living body are superimposed and displayed.
It is preferable that the image display unit 17 simultaneously displays the image data and the captured image of the subject and the light absorber acquired in advance.

  FIG. 8C shows a conventional photoacoustic microscope apparatus in which the light transmissive film 81 does not have a light absorber serving as an alignment mark. When photoacoustic imaging is performed using this apparatus, a photoacoustic image as shown in FIG. 8D is obtained. However, since the light absorber 83 such as a blood vessel in the living body is under the skin and is difficult to see, accurate alignment and scan range identification are difficult without the alignment mark.

On the other hand, in the present embodiment, by using the grid-like photoacoustic image 86 as an alignment mark, it is possible to accurately align the photoacoustic image and the actual subject position.
When only the grid is to be erased from the displayed photoacoustic image, the obtained image data may be displayed in MIP without including the data of the grid position. Alternatively, since the photoacoustic wave generated from the light absorber 82 reaches the focus type probe 76 earlier in time than the photoacoustic wave generated from the living body, a signal earlier in time is cut from the electrical signal. What is necessary is just to convert into image data.

The shape of the light absorber 82 is not limited to a grid shape, and any shape that functions as an alignment mark may be used. The light absorber 82 is preferably insoluble in water.
The light transmissive film 81 preferably has high light transmittance and high durability against light. For example, a polyethylene film can be used as such a material.

As the light emitting unit 71, a light guide (for example, an optical fiber) that guides pulsed light emitted from a light source can be used. Further, a light source may be arranged in the light emitting part 71.
The acoustic coupling medium 79 in the water tank 72 may be anything that acoustically matches the living body and the focus type probe 76, and water can be used, for example.

The focus type probe 76 preferably includes an acoustic lens for converging sound. However, any probe that can converge the sound may be used. For example, a probe having a concave receiving surface may be used.
As a probe, any acoustic wave detector can be used as long as it can detect an acoustic wave signal, such as a transducer using a piezoelectric phenomenon, a transducer using optical resonance, or a transducer using a change in capacitance. It may be used. The probe is preferably capable of receiving high-frequency ultrasonic waves. Furthermore, a broadband is preferable.

As the focus type probe 76, a probe in which receiving elements are arranged in an array may be used instead of a single transducer. In this case, it is necessary to provide a sound collection lens or the like for each receiving element.
When the electric signal obtained from the focus type probe 76 is small, it is preferable to amplify the signal intensity using an amplifier.

Based on the electrical signal obtained from the focus type probe 76, the signal processing unit 77 calculates the position and size of the absorber in the living body, or the optical characteristic value distribution such as the light absorption coefficient or the light energy deposition amount distribution. calculate. Further, the optical characteristic value distribution of the light absorber 82 on the light transmissive film 81 is calculated.
For image processing to obtain optical characteristic value distribution from electrical signals at multiple positions, after performing envelope detection using Hilbert transform, the time axis of sound arrival time is converted to the spatial axis in the sound focus direction Thus, it is conceivable to perform three-dimensional position data.

Specific processing in the present embodiment will be described with reference to FIG.
As a living body, a nude mouse was used.
The focus type probe is made of PZT and has a center frequency of 50 MHz, and an acoustic lens designed so that the sound is focused at a position of 8 mm from the lens surface is disposed on the entire surface of the PZT. The water tank is filled with water for acoustic matching.

  FIG. 9A is a captured image obtained by photographing the film 90 as a light transmissive member from the opposite side to the subject before the photoacoustic measurement. In FIG. 9A, a light absorber 91 is printed in a grid shape with black ink on a light transmissive film 90 which is a polyethylene film.

A YAG laser is used as the light source. The repetition frequency of the emitted pulsed light is 10 Hz, the pulse width is 10 ns, and the wavelength is 532 nm. The pulsed light emitted by the YAG laser is emitted to the living body using an optical fiber having a core diameter of 550 μm.
In addition, an aluminum mirror and an axicon lens are used as optical components for collecting light at the focal point of the sound.

  Photoacoustic measurement is performed while scanning the probe and the light irradiation position using a stepping motor. The scan pitch is 50 μm in both the X direction and the Y direction, and a range of 5 mm × 5 mm surrounded by the solid line 92 is measured by scanning 100 steps each.

FIG. 9B is a MIP display of the measurement result. The blood vessel image 93 of the mouse and the grid image 94 of the light absorber 91 are displayed so as to overlap each other.
Then, by comparing FIG. 9A and FIG. 9B captured in advance, accurate alignment between the blood vessel position in the photoacoustic image and the actual living body position can be easily performed.

  On the other hand, FIG. 9C is a captured image in a conventional apparatus having no light absorber on the light transmissive film. FIG. 9D shows an image of the measurement result obtained by this apparatus. As can be seen, it is difficult to accurately align the blood vessel position in the acoustic image with the actual living body position.

  As described above, according to the biological information imaging apparatus of the present invention, accurate alignment between the photoacoustic image and the actual subject position can be easily performed without complicating the apparatus.

As described above, according to the present invention, for the diagnosis of tumors and vascular diseases and the follow-up of chemical treatment, etc., the distribution of optical characteristic values in the living body and the substances constituting the living tissue obtained from the information It is possible to form an image of the density distribution. The present invention can be used as a medical diagnostic imaging apparatus.
Furthermore, application to non-destructive inspection for non-biological substances is also possible.

  11: Light transmissive member, 21: Light absorber, 16: Probe, 16: Signal processing unit, 18, 19: Light emitting unit

Claims (15)

A light emitting unit that emits light from a light source;
A light transmitting member disposed between the subject and the light emitting unit;
A light absorber disposed on the member;
A probe that receives an acoustic wave generated from the subject and the light absorber irradiated with light from the light emitting unit and converts the acoustic wave into an electrical signal;
Using the electrical signal, a signal processing unit that generates image data of the subject and the light absorber;
A subject information acquisition apparatus characterized by comprising: 2. The subject according to claim 1, wherein the signal processing unit generates image data of the subject and the light absorber so that the image data can be displayed on an image display device by a maximum value projection method. Information acquisition device. The object information acquiring apparatus according to claim 1, wherein the light absorber is arranged in a range corresponding to a measurement region of the object among the members. 3. The subject information acquisition apparatus according to claim 1, wherein the light absorber is disposed within a range of the member in which the subject is orthogonally projected onto the member. 4. An image acquisition unit for acquiring a captured image of the subject and the light absorber;
5. The object information acquisition apparatus according to claim 1, wherein the signal processing unit displays the captured image together with the image data on an image display device. 6. 6. The object information acquiring apparatus according to claim 1, wherein the light source is capable of irradiating light having a plurality of wavelengths. The object information acquiring apparatus according to claim 1, wherein the light absorber is disposed on a side of the member that does not contact the object. The object information acquiring apparatus according to claim 1, wherein the light absorber is hardly soluble in water. The object information acquiring apparatus according to claim 1, wherein the light absorber is printed on the member. The object information acquiring apparatus according to claim 1, wherein the light absorber is arranged in a grid shape on the member. The object information acquiring apparatus according to claim 1, wherein the light absorbers are arranged at regular intervals in a dot shape on the member.   10. The object information acquiring apparatus according to claim 1, wherein the light absorber is disposed on the member so as to correspond to an assumed contour of the object. 11. The object information acquiring apparatus according to claim 1, wherein the member has a flat plate shape. The object information acquiring apparatus according to claim 13, wherein the member is made of glass or acrylic. The object information acquiring apparatus according to claim 1, wherein the member has a film shape.

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