WO2016051749A1

WO2016051749A1 - Object information acquiring apparatus

Info

Publication number: WO2016051749A1
Application number: PCT/JP2015/004892
Authority: WO
Inventors: Yasufumi Asao; Tooru Imai
Original assignee: Canon Kabushiki Kaisha
Priority date: 2014-09-29
Filing date: 2015-09-25
Publication date: 2016-04-07
Also published as: JP2016067491A

Abstract

Provided is an object information acquiring apparatus having: an optical system that irradiates an object with light from a light source and generates an acoustic wave; a probe that receives the acoustic wave propagated from a measuring region in the object; a signal processing unit that acquires specific information of the object using an electric signal; and a fixing unit that is disposed in a fixing region surrounding the measuring region in the object, and fixes the object in a position where the probe can receive the acoustic wave propagated from the measuring region.

Description

OBJECT INFORMATION ACQUIRING APPARATUS

The present invention relates to an object information acquiring apparatus.

Recently imaging apparatuses using x-ray, ultrasound and MRI (Magnetic Resonance Imaging) are used in medical fields. Vigorous research on optical imaging apparatuses, which propagates light radiated from a light source such as a laser through an object such as a living body and detects the propagated light or the like to acquire information inside the living body, is ongoing in medical fields. Currently, optical imaging apparatuses are receiving attention not only in medical fields but also in cosmetic fields. Photoacoustic imaging is proposed as one such optical imaging technique.

Photoacoustic imaging is a technique that irradiates an object with pulsed light generated from the light source, detects an acoustic wave (photoacoustic wave) generated from biological tissue which absorbed energy of the propagated/diffused light in the object, and visualizes information related to the optical characteristic value inside the object. Thereby the optical characteristic value distribution inside the object, especially the light energy absorption density distribution, can be acquired.

For example, a blood vessel image inside a living body can be imaged noninvasively by using light having a wavelength which can be well absorbed by hemoglobin as the pulsed light. Collagen, elastin or the like under skin can be imaged by using a different wavelength. Fat, blood glucose or the like can also be imaged. Further, the blood vessel image can be enhanced and a lymphatic vessel can be imaged by using a contrast agent.
Moreover, in the photoacoustic imaging, oxygen saturation degree distribution in blood can be measured based on the sound pressure intensity ratio of the photoacoustic wave when pulsed lights with a plurality of wavelengths are radiated, using the difference in the absorption spectrum of the light energy of oxyhemoglobin and that of deoxyhemoglobin in blood.

A well known three-dimensional visualization technique using photoacoustic imaging is a technique to generate three-dimensional data related to the optical characteristic value by receiving a photoacoustic wave generated from the light absorber using a probe disposed on a two-dimensional surface, and reconstructing the image. This three-dimensional visualization technique is called "photoacoustic tomography (PAT)".

Furthermore, photoacoustic microscopes are receiving attention as an apparatus that visualizes specific information at high spatial resolution using photoacoustic imaging. Photoacoustic microscopes can acquire high resolution images by focusing light or sound using an optical lens or an acoustic lens.

In Non-patent Literature 1, an ultrasonic focus type photoacoustic microscope using an acoustic lens is presented. According to Non-patent Literature 1, the image of blood vessels existing in an area close to skin can be imaged at high resolution. An example of an object in this case is blood vessels under the skin of a small animal, such as a mouse.
In Non-patent Literature 2, the oxygen saturation degree distribution in the blood vessels of the ear of a mouse is calculated using a photoacoustic microscope.

However, in photoacoustic apparatuses, such as a PAT apparatus and a photoacoustic microscope, it is known that the depth to be visualized and the spatial resolution normally are in a trade-off relationship. In other words, a photoacoustic image has a characteristic that spatial resolution drops more as the tissue is located in a deeper location of a living body. This is because light easily disperses in a living body, and a photoacoustic wave with high frequency, generated in a living body, easily attenuates. Because of this, the major application of the photoacoustic microscope having high spatial resolution is visualizing a light absorber in skin that is located in a relatively shallow portion of a living body. If blood hemoglobin is the target as the light absorber, blood vessels located in the dermic layer are visualized.

In vivo dark-field reflection-mode photoacoustic microscopy, Vol.30, No.6, OPTICS LETTERS Functional photoacoustic microscopy for high-resolution and noninvasive in vivo imaging, Nature Biotechnology 24, 848 851 (Jul. 2006)

In the case of Non-patent Literature 1, a small animal or the like can be measured in a live state, but if the measurement target moves during the measurement, generating a high resolution image is difficult. If a high resolution visualizing unit is used in the case of Non-patent Literature 1, a slight body motion is displayed as an extremely severe artifact. In other words, the body of an animal, including a human body, is constantly moving in a several mm range due to breathing, heart beating and the slight shaking of the body. The influence of such body motion on an image is minor if the resolution of the imaging apparatus is low, but this becomes major as the resolution is higher.

Even if body motion is generated during measurement by the high resolution imaging apparatus, the influence of body motion on the image can be minor if the apparatus can acquire the image instantaneously. But a certain amount of time is required in the case of a photoacoustic microscope, since the image is formed by scanning the focus positions of the light or sound by a point sequence system. Therefore body motion influences the accuracy of the image.

Further, a problem of determining the oxygen saturation degree of blood using a plurality of pulsed lights, as in the case of Non-patent Literature 2, is that images generated by the plurality of wavelengths shift due to the motion of the measurement target, which makes accurate calculation of oxygen saturation degree distribution impossible.

With the foregoing in view, it is an object of the present invention to accurately acquire specific information with less influence by body motion when photoacoustic measurement is performed on an object of which body motion may occur.

To solve the above problem, the present invention provides an object information acquiring apparatus, comprising:
a light source;
an optical system that irradiates an object with light from the light source and generates an acoustic wave;
a probe that receives the acoustic wave propagated from a measuring region in the object and converts the acoustic wave into an electric signal;
a signal processing unit that acquires specific information of the object using the electric signal; and
a fixing unit that is disposed in a fixing region surrounding the measuring region in the object, and fixes the object in a position where the probe can receive the acoustic wave propagated from the measuring region.
The present invention also provides a fixing unit for an object information acquiring apparatus that receives, by a probe, an acoustic wave generated from an object irradiated with light from a light source, and acquires specific information of the object using the acoustic wave, the fixing unit fixing the object in a position where the probe can receive the acoustic wave propagated from a measuring region of the object,
the fixing unit comprising a member disposed in a fixing region surrounding the measuring region in the object.

According to the present invention, specific information can be accurately acquired with less influence by body motion when photoacoustic measurement is performed on an object of which body motion may occur.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

Fig. 1 is a diagram depicting a configuration of a photoacoustic microscope apparatus of Embodiment 1. Fig. 2A and Fig. 2B are diagrams depicting an application of an adhesive layer to an object. Fig. 3 is a flow chart of a measurement by the photoacoustic microscope apparatus. Fig. 4 is a timing chart of a measurement by the photoacoustic microscope apparatus. Fig. 5 is a diagram depicting a configuration of a photoacoustic tomography apparatus of Embodiment 2. Fig. 6 is a diagram depicting a configuration of a photoacoustic tomography apparatus of Embodiment 3. Fig. 7A and Fig. 7B are diagrams depicting a configuration of an adhesive layer of Embodiment 4. Fig. 8A and Fig. 8B are diagrams depicting a configuration of an adhesive layer of Embodiment 5. Fig. 9 is a diagram depicting a configuration of a protective film of the adhesive layer. Fig. 10 is a diagram depicting a configuration of a photoacoustic microscope apparatus of Embodiment 6. Fig. 11 is a diagram depicting a fixing unit of Embodiment 6. Fig. 12 is a diagram depicting another fixing unit of Embodiment 6. Fig. 13 is a flow chart of a measurement by the photoacoustic microscope apparatus of Embodiment 6. Fig. 14 is a diagram depicting an air suction unit. Fig. 15 is a diagram depicting a configuration of a photoacoustic microscope apparatus of Embodiment 7. Fig. 16 is a diagram depicting a hand held type probe of Embodiment 9.

Embodiments of the present invention will now be described with reference to the drawings. Dimensions, materials and shapes of the components described below, and relative positions thereof or the like should be appropriately changed in accordance with the configuration and various conditions of an apparatus to which the invention is applied, and are not intended to limit the scope of the present invention.

The present invention relates to a technique that detects an acoustic wave propagated from an object, generates specific information inside the object, and acquires the information. Therefore the present invention can be interpreted as an object information acquiring apparatus or a control method thereof, or an object information acquiring method and a signal processing method. The present invention can also be interpreted as a program for allowing an information processing apparatus having such a hardware resource as a CPU to execute these methods, or as a storage medium storing the program. The present invention can also be interpreted as an acoustic wave measuring apparatus and a control method thereof.

The object information acquiring apparatus of the present invention includes an apparatus utilizing a photoacoustic imaging technique to irradiate an object with light (electromagnetic wave), and receive (detect) an acoustic wave which is generated inside the object or on the surface of the object, and propagates according to the photoacoustic effect. This object information acquiring apparatus acquires specific information inside the object in an image data format or the like based on the photoacoustic measurement, and can therefore by called a "photoacoustic imaging apparatus".

The specific information in the photoacoustic apparatus indicates a generation source distribution of an acoustic wave generated by light irradiation, initial sound pressure distribution inside the object, light energy absorption density distribution and absorption coefficient distribution derived from the initial sound pressure distribution, and density of substance constituting the tissue. In concrete terms, the specific information is oxy/deoxyhemoglobin concentration distribution, blood component distribution, such as oxygen saturation degree distribution, determined from the oxy/deoxyhemoglobin concentration distribution, or distribution of fat, collagen, water or the like. The specific information may be determined, not as numeric data, but as distribution information at each position inside the object. In other words, the distribution information, such as absorption coefficient distribution and oxygen saturation degree distribution, may be used as object information.

The acoustic wave referred to in the present invention is typically an ultrasonic wave, and includes an elastic wave called a "sound wave" and "acoustic wave". An acoustic wave generated by the photoacoustic wave is called a "photoacoustic wave" or a "light induced ultrasonic wave". An electric signal converted from an acoustic wave by a probe is also called an "acoustic signal", and an acoustic signal generated from a photoacoustic wave in particular is called a "photoacoustic signal".
Focusing on the aspect of generating a high resolution image near the surface of the object by light, the photoacoustic apparatus of the present invention can be a photoacoustic microscope. A possible object in the present invention is the skin of a living body or blood vessels near the skin surface. The object, however, is not limited to these examples.

(Embodiment 1)
In Embodiment 1, an ultrasonic focus type photoacoustic microscope will be described in detail. The method of the present invention, however, can also be applied to a light focus type photoacoustic microscope.

(Description of general configuration)
A general configuration of the photoacoustic microscope of Embodiment 1 will be described first with reference to Fig. 1.
A pulsed light source 101 emits a pulsed light under control of a measuring control unit 102. The pulsed light transmits through an optical fiber 103 and is guided to an optical system for irradiating a living body with excitation light. The pulsed light 104 emitted from the optical fiber 103 is collimated by a lens 105, and a part of the pulsed light is reflected by a beam splitter 106. The pulsed light that transmitted through the beam splitter 106 is spread in a circle by a conical lens 107.

A part of the pulsed light reflected by the beam splitter 106 is collected by a lens 108 and is detected by a photodetector 109. The detected signal is converted into a digital signal (pulsed light signal) by a data acquisition board (DAQ board) 110, and is stored in an internal memory. The pulsed light signal detected by the photodetector 109 is used for correcting an error generated by the change of light quantity of the photoacoustic signal, or is used as a trigger signal to determine a measuring timing of the photoacoustic wave.

The pulsed light 104 that is spread in a circle by the conical lens 107 is reflected by a mirror 111, so as to be collected again. When the photoacoustic wave is measured, the focal point of the collected light is aligned to enter inside the object 113. The pulsed light diffused inside the object 113 is absorbed by a light absorber 112, such as blood, inside the object, in accordance with the absorption coefficient of the light. Then a photoacoustic wave 114 is generated by the photoacoustic effect.

The photoacoustic wave 114 is detected by a probe 115 disposed near the center of the mirror 111, and the change of the sound pressure intensity thereof is converted into an electric signal. An acoustic lens is disposed in the probe 115, and the sound wave generated from the focal position of the acoustic lens can be detected with good sensitivity. The focal point of the acoustic lens is designed to be in a position included by the focal region of the pulsed light. Water, stored in a water tank 116, exists between the probe 115 and the object 113 as the acoustic matching material. A gel type matching material may be coated between the bottom of the water tank 116 and the object 113.

The electric signal converted from the photoacoustic wave 114 by the probe 115 is sent to a signal amplifier (AMP) 117 by which signal intensity is amplified. The amplified signal is converted into a digital signal by the data acquisition board (DAQ board) 110, and is stored in the internal memory. A signal processing unit 118 performs signal processing on the data stored in the data acquisition board 110. An image processing unit 119 performs image processing on the signal, and generates image data. A display unit 120 displays the image data.
The measuring control unit 102 performs not only emission control of the pulsed light source 101, but also a control for

automatic stages

122 and 123 and a control for data sampling of the data acquisition board 110.

Members surrounded by a frame 121 in Fig. 1 are integrated in a casing (not illustrated). The casing is connected to the

automatic stages

122 and 123 that can scan on a two-dimensional surface, and can be moved to a desired position in the xy directions by the control of the measuring control unit 102. Thereby the casing portion indicated by the frame 121 is two-dimensionally scanned in the xy directions in Fig. 1 in the water tank 116.

If the object 113 is a stationary object, the relative positional relationship between the water tank 116 and the object 113 is fixed. Therefore the positions of the focal point of the pulsed light 104 focused on the object 113 and the focal point of the sound wave of the probe 115 are moved by the two-dimensional scanning of the casing, and the photoacoustic wave is detected at each measuring position, whereby the photoacoustic signal data on the two-dimensional surface can be acquired.
If the object 113 is a moving object, such as a living body, on the other hand, body motion influences the measurement. As a result, a location of the object, which is different from the portion instructed by the measuring control unit 102, may be measured. To prevent this, an adhesive layer 124 is disposed in Embodiment 1, so that the measuring region does not move. The method of disposing the adhesive layer will be described later.

In the above configuration, the focal region of the pulsed light 104 includes the focal point of the ultrasonic wave of the acoustic lens of the probe 115 (ultrasonic focus type). The present invention however can also be applied to a light focus type photoacoustic microscope where the focal region of the pulsed light is smaller than the focal region of the ultrasonic wave. In other words, the focal region, when the pulsed light 104 is focused using an objective lens or the like, may be included in the region of a focal point of the ultrasonic wave of the acoustic lens of the probe 115. Since the size of the focal point of the light determines the resolution of the photoacoustic microscope, a photoacoustic image having higher resolution can be acquired if the light focus type photoacoustic microscope is used. The apparatus of Embodiment 1 is a photoacoustic microscope, hence an image of the measuring target can be formed by scanning the focal positions of light or sound in point sequence.

(Fixing object by adhesive layer)
Fixing the object by the adhesive layer to reduce body motion will be described in more detail. By fixing the adhesive layer, a change in the relative positional relationship between the water tank 116 and the object 113 is controlled. However, if the object 113 is strongly constrained and body motion is completely stopped, the burden on the living body increases. Therefore in the adhesive method to be used, it is preferable to fix the relative positional relationship between the water tank 116 and the object 113 while allowing some body motion.

It is preferable to dispose the adhesive layer in a location that is different from the measuring region, since the adhesive layer could cause unexpected noise. Various shapes can be used for the adhesive layer, such as a shape constituted by a circular or angular closed curve, or a plurality of curves or lines. In Embodiment 1, the fixing unit that reduces the motion of the object is called the "adhesive layer", but this does not mean that the shape of the fixing unit is limited. In other words, the fixing unit is not limited to a layer type member if the member is disposed between the object and the water tank (or the probe), and can control the change in the relative positions.
If the adhesive layer is thick, an air layer may be generated between the water tank 116 and the object 113, which interferes with propagation of sound waves. In such a case, it is preferable to use an acoustic matching material, such as matching gel for ultrasonic waves, or water.

Fig. 2A illustrates an example of a location of the adhesive layer that is adhered when the skin of a human face is measured. The entire face is not fixed by the adhesive layer, but the region 201a around the measuring region of the cheek is the adhesive region. The adhesive region is outside the measuring region, and surrounds the measuring region. The size of the adhesive region should be minimal. Because of the presence of the adhesive region, the measuring region can be kept in a fixed state, even if body motion is generated, by the elasticity of the skin of the cheeks or the entire face. In the embodiment using the adhesive layer, this adhesive region corresponds to the fixed region of the present invention.

Fig. 2B illustrates an example of a location of the adhesive layer that is adhered when the skin of a human finger is measured. The entire hand is not fixed, but the region 201b around the measuring region of the finger is the adhesive region. The adhesive region is outside the measuring region, and the size should be minimal. Thereby the measuring target region can be kept in a fixed state, even if body motion is generated, by the elasticity of the skin of the finger, or by bending or extending the joint of the finger.

The material of the adhesive layer may be any material that has a function to adhere the object and the apparatus. For example, a double-sided tape or glue can preferably be used, and in the case of human skin, medical double-sided tape is more preferable since it is nonabrasive to a living body.

(Data acquisition process)
A method of acquiring the two-dimensional surface data of the photoacoustic signal generated inside the object 113 and displaying the image using the ultrasonic focus type photoacoustic microscope described with reference to Fig. 1 will now be described in concrete terms.

(Flow chart)
The measuring procedure will be described first with reference to the flow chart on the measurement in Fig. 3. Before measurement, an object 113, of which photoacoustic image is measured using the ultrasonic focus type photoacoustic microscope, is set in advance. After the object is set, the measuring flow starts.
When the object is set, the water tank 116 and the object 113 are adhered to each other using the adhesive layer 124, as mentioned above. In this case, the adhesive layer may be adhered to the measuring segment of the object in advance, and is then adhered to the apparatus. Otherwise the adhesive layer may be disposed in the apparatus in advance, and the object may be adhered to the adhesive layer (steps S301, S302).

Then the measuring region is set. Since the adhesive area may cause unexpected noise, the scanning is controlled such that the adhesive layer is excluded from the measuring region. For this, it is preferable to provide an input unit (not illustrated) that can specify a range or that can input numeric values via a mouse or touch pad. A function to detect the location of the adhesive layer using a camera or the like, and automatically set the inner side of the adhesive layer as the scanning region, may be provided. It may be specified not to use an electric signal originating from the adhesive layer for a subsequent processing (step S303).

Then the photoacoustic measurement is executed (step S304).
First the object 113 is irradiated with the pulsed light 104, and a photoacoustic wave 114, generated from a light absorber, such as hemoglobin existing inside the object, is detected and converted into an electric signal by the probe 115. The converted photoacoustic signal is amplified by the signal amplifier 117, is then converted into a digital signal by the data acquisition board (DAQ board) 110, and is stored in the internal memory. The data stored in the data acquisition board 110 is sent to the signal processing unit 118 according to the control of the measuring control unit 102. The measurement is executed at all the measuring locations while moving the measuring position by an automatic stage, and the photoacoustic measurement is completed. A stage to scan the object side may be disposed.

In step S305, the signal processing unit 118 performs signal processing for the acquired photoacoustic signal at each location. The signal processing performed here is: deconvolution considering the pulse width of the pulsed light source 101; envelope detection, or the like. If a frequency that is characteristic of the noise added to the signal is known in advance, and can be separated from the primary frequency of the light induced ultrasonic signal, then the specific frequency component due to the noise can be removed. Further, components that originated from the multiple-reflected photoacoustic wave on the surface of the object or on the bottom of the water tank 116 are removed. If the photoacoustic wave generated on the surface of the object is conspicuous, the components that originated from the photoacoustic wave may also be removed here.

In step S306, the image processing unit 119 creates voxel data using the electric signal after signal processing, based on the signal intensity distribution on the automatic stage scanning surface in the object depth direction, and performs image processing, as appropriate. At this time, noticeable artifacts are removed from the voxel data if any. When the oxygen saturation degree of the light absorber in the object is calculated, for example, the voxel data that stores the oxygen saturation degrees may be created in advance based on the voxel data of the photoacoustic signal intensity acquired at a plurality of wavelengths of the pulsed light. It is also possible that when the wavelength of a pulsed light is set regarding blood hemoglobin in the object as the major light absorber and measurement is performed, the image of the blood vessels is binarized and extracted from the acquired voxel data, for example.

In step S307, the voxel data created from the photoacoustic signal intensity distribution in S306 is displayed in the display unit 120 by a display method desired by the user. For example, a method of displaying a cross-section that is orthogonal to each axis of the three-dimensional coordinates, or a method of displaying the voxel data in each axis direction as the two-dimensional distribution of the maximum values, the minimum values or the means values, is used. In this case, a user interface program may be constructed so that the user can set the ROI (Region Of Interest) in the voxel data, and statistical information and oxygen saturation degree information on the shape of the absorber in the region are displayed.

(Timing chart)
The timing of each operation in the measurement of the photoacoustic signal will be described with reference to the timing chart in Fig. 4. To simplify description, the shapes and timings of the signals are simplified here.

In Fig. 4, the reference numeral 401 indicates an emission timing of the pulsed light source 101. The emission timing of the pulsed light source is controlled by the measuring control unit 102. The present invention is not limited to this, but the emission timing may be controlled based on the trigger signal, which is outputted from the encoder of the automatic stage, for example, at an equal moving distance interval or equal time interval.
The reference numeral 402 indicates a trigger signal to be a reference of the start of measurement of the photoacoustic signal, generated from the pulsed light detected by the photodetector 109. This trigger signal may be generated by referring to a signal that controls the emission timing of the pulsed light source.

The signal indicated by the reference numeral 403 is a photoacoustic wave, which was excited by the pulsed light emitted at the timing of the signal 401, and reached the probe. This signal is generated with a delay corresponding to the time of the photoacoustic wave that reached the transducer from the generation source inside the object.
The reference numeral 504 indicates a sampling timing to measure the photoacoustic wave that reached the transducer, and stores the measurement result in the memory. According to necessity, measurement is started at a timing that is delayed from the measuring trigger signal, and sampling is performed for a time required for imaging the photoacoustic wave. If there is sufficient memory in the data acquisition board (DAQ board) 110, the measurement may be started without delay. It is preferable to set the measuring sampling frequency to a frequency as high as possible, to at least double the primary frequency of the photoacoustic wave to be generated.

(Addition of preferred configuration)
The preferred configuration of the apparatus will be added.
For the pulsed light 104 with which the object 113 is irradiated, light with a wavelength having a characteristic that is absorbed by a specific component, out of components constituting the object 113, is used. The pulse width of the pulsed light 104 is in a several pico to several hundred nanosecond order, and if the object is a living body, using a pulsed light in a several nano to several tens nanoseconds order is preferable. For the pulsed light source 101 that generates the pulsed light 104, laser is preferable, but a light emitting diode, a flash lamp or the like may be used instead of laser. If the object is a living body, design considering safety standards on laser light is performed.

For the laser used for the pulsed light source 101, various lasers including a solid-state laser, gas laser, dye laser and a semiconductor laser can be used. If a dye laser or OPO (Optical Parametric Oscillators), of which wavelength of the oscillated light can be converted, is used, the difference based on the wavelength of the optical characteristic value distribution can be measured. Regarding the wavelength of the pulsed light source 101, wavelength regions from 400 nm to 1600 nm can be used, and terahertz wave, microwave and radio wave regions can also be used.
If lights with a plurality of wavelengths are used as the pulsed light 104, an optical coefficient in the living body is calculated for each wavelength, and these values and a wavelength dependency that is unique to the substance constituting the biological tissue (e.g. glucose, collagen, oxy/deoxyhemoglobin) are compared. Thereby the concentration distribution of the substance constituting the living body can be imaged.

The probe of the present invention has a receiving element that converts a received acoustic wave into an electric signal, and outputs the electric signal. In the case of the later mentioned photoacoustic tomography apparatus, an element array, in which a plurality of receiving elements are arrayed linearly or two-dimensionally, is used, whereby the measuring time is decreased and the SN ratio improves. The receiving element is preferably a piezoelectric element, but the element is not limited to this.
The display unit 120 is preferably a liquid crystal display device, CRT or the like, but the display is not limited to this.

The open part in the upper side of the water tank 116 is preferably covered by a cover made of waterproof material, such as vinyl, to prevent water from splashing out of the water tank. A duct or valve to supply or discharge water when necessary may be connected to the water tank 116 in order to improve maintenance performance. In this case, it is preferable to include a controller to automatically supply or discharge water. The liquid, as an acoustic matching material to be supplied to the water tank 116, need not be water. Any liquid that is highly transmissive to pulsed light 104, and that can match the acoustic impedance of a photoacoustic wave 114, can be used.

As described above, by fixing the positional relationship between the object and the water tank (or a member in the propagating direction of the photoacoustic wave) using a fixing unit, such as an adhesive layer, the influence of body motion of the object in the photoacoustic microscope imaging can be decreased, and a high resolution image can be acquired.

(Embodiment 2)
In Embodiment 2, a photoacoustic tomography apparatus will be described. This apparatus acquires the sound pressure of a photoacoustic wave, generated in the object, in a plurality of locations on the two-dimensional surface, and performs image reconstruction calculation, so as to generate three-dimensional information related to the optical characteristic values inside the object. The photoacoustic tomography apparatus is the same as the photoacoustic microscope of Embodiment 1 in terms of receiving a photoacoustic wave generated by the photoacoustic effect. However unlike Embodiment 1, the region where light or a sound wave is focused and a photoacoustic wave is detected upon measurement is not limited.

(Description on general configuration)
A configuration of the apparatus of Embodiment 2 will be described with reference to Fig. 5. A same composing element as Embodiment 1 is denoted with a same number, for which description is simplified.

The water tank 116 and the object 113 are adhered to each other by the adhesive layer 124. The pulsed light source 101 emits the pulsed light 104 for exciting the photoacoustic wave. The pulsed light 104 transmits through the beam splitter, and is then radiated onto the object via a mirror 501, a concave lens 502 or the like.
In Example 2, the pulsed light is spread by a concave lens 502 and is radiated onto the object. The photoacoustic wave 114 from the light absorber 112 inside the object is excited by the radiated pulsed light 104. A probe 503 detects the sound pressure of this photoacoustic wave.

In Embodiment 2, only the probe 503, surrounded by the dashed line frame 504, is scanned on the two-dimensional surface using an automatic stage (not illustrated). On the other hand, the optical system for guiding the pulsed light to excite the photoacoustic wave is fixed. By this automatic stage scanning, the photoacoustic wave 114 can be acquired at a plurality of locations on the two-dimensional surface. The probe 503 of Embodiment 2 does not include an acoustic lens.
In Fig. 6, the configuration to radiate the light from outside the probe is illustrated, but a configuration to radiate the light from the center of the probe, that is, from a position between light receiving elements, may be used.

Since the optical system and the acoustic wave receiving system have the above configuration in Embodiment 2, the photoacoustic wave is detected with somewhat wide directivity. An image processing unit 505 of Embodiment 2 calculates the initial pressure distribution of the photoacoustic wave inside the object by reconstructing an image from the photoacoustic signal acquired on the two-dimensional surface.

(Data acquisition process)
The data acquisition process will be described next. The difference from Embodiment 1 is that the image processing unit 505 performs the image reconstruction calculation, and creates the voxel data of the initial pressure distribution inside the object. A known method can be used for image reconstruction, such as phasing addition, filtered back projection, universal back projection and a Fourier transform method. Using such a method, the initial sound pressure values of pixels or voxels of the target region are determined, and absorption coefficients are determined based on the light quantity distribution, whereby the specific information distribution, reflecting the functional information of the object, can be acquired and presented to the user. Further, the oxygen saturation degree distribution can be calculated based on the absorption coefficient distribution at a plurality of wavelengths.

(Fixing object by adhesive layer)
In Embodiment 2 as well, the relative positional relationship between the water tank 116 and the object 113 can be fixed by the adhesive layer 124, which is a fixing unit. The material, size and adhering method of the adhesive layer are selected based on the same concept as Embodiment 1, so that the relative positional relationship between the water tank 116 and the object 113 is fixed while allowing body motion.

According to Embodiment 2, in the photoacoustic tomography apparatus as well, the influence of the body motion of the object can be reduced, and a high resolution image can be acquired by fixing the positional relationship between the object and the water tank using the adhesive layer, just like the case of the photoacoustic microscope.

(Embodiment 3)
In Embodiment 3, the PAT principal is used, just like Embodiment 2. In Embodiment 3 however, the PAT image is acquired at a fixed position without scanning the probe, by using a one-dimensional or two-dimensional array probe. In the apparatus configuration of Embodiment 3 illustrated in Fig. 6, a composing element the same as Fig. 1 and Fig. 5 is denoted with a same number, for which description is simplified. A probe 601 in Fig. 6 is an array type probe in which a plurality of receiving elements is arrayed. The probe has a casing which supports the element array. Therefore a photoacoustic tomographic image can be acquired even if measurement is performed at only one location without moving the probe.

In the case of Embodiment 3 as well, just like the above embodiments, the adhesive layer 124 can be used to control the influence of body motion. In this case, the adhesive layer 124 can be directly adhered to the probe 601. Here if an air layer exists between the object 113 and the probe 601, a sound wave is not propagated, so it is preferable to create a configuration that allows the sound wave to propagate, such as using a matching gel.
Besides the method of disposing the adhesive layer on a part of the probe and using a matching gel on the remaining portion, as illustrated in Fig. 6, an ultrasonic wave may be propagated by disposing the adhesive layer on the entire surface of the probe.

A measuring control unit 602 of Embodiment 3 controls the array type probe interlocking with the light irradiation so that the acoustic wave propagated from a region of interest which is set in the object can be received, and receives data at an appropriate timing. An image processing unit 603 of Embodiment 3 has a function to acquire a tomographic image inside the object from the data acquired by scanning, and a function to synthesize three-dimensional image data from a plurality of tomographic images.
In Fig. 6, the configuration to radiate the light from outside the probe is illustrated, but light may be radiated from the center of the probe, that is, from a position between the receiving elements.

According to the photoacoustic tomography apparatus of Embodiment 3, when an object is measured using a probe in which the receiving elements are arrayed, changes in the positional relationship between the probe and the object can be controlled by the effect of the adhesive layer. In Embodiment 3, a container for acoustic matching material, such as a water tank, is not used, hence cost is reduced by a simplification of the apparatus configuration, and the burden on the subject whose face or hand is measured can be reduced. Further, an increase in the number of elements leads to a decrease in measuring time, an improvement in measuring accuracy, and an improvement in the SN ratio.

The configuration of Embodiment 3 is particularly preferable when a hand held type probe is used for the probe 3. In other words, the measuring time should not be lengthy if the probe is contacted to the measuring region disposed on the face or hand of the subject, as illustrated in Fig. 2, but in the case of Embodiment 3, specific information can be acquired quickly and at high accuracy.

(Embodiment 4)
In each embodiment described above, the adhesive layer 124 is used as the fixing unit of the apparatus and the object, and matching gel or the like is used as the acoustic matching material when necessary. In this case, the matching gel or the like may spread, contact the adhesive layer, and diminish adhesion. Therefore Embodiment 4 has a configuration that controls the spread of the matching gel, and minimizes the influence of the matching gel to the adhesive layer.

Fig. 7A and Fig. 7B are diagrams depicting an adhesive layer according to Embodiment 4. Fig. 7A is a plan view of the adhesive layer. The reference numeral 701 indicates a segment that has an adhesive function, and 702 indicates a partition structure for separating the matching gel or water from the adhesive layer, so that the matching gel or water does not flow into the adhesive layer. Fig. 7B is a cross-sectional view at the A-A’ line when the adhesive layer is viewed from the side. The

reference numerals

701 and 702 indicate the same segments as Fig. 7A. In Fig. 7, the partition is higher (thicker) than the adhesive layer to prevent the matching gel from flowing in, but the partition and the adhesive layer may have similar heights.

The reference numeral 703 indicates a film to be a base material to support the partition structure 702 and the adhesive layer 701, so that the partition structure 702 and the adhesive layer 701 do not separate from each other. This film is preferably a thin and transparent member, since the light and the ultrasonic wave must transmit through. In terms of transmitting the ultrasonic wave, the thickness is preferably 200 μm or less. The base film 703 has a structure that contacts the object or the apparatus, and if the base film 703 is slippery, this is the same as having no adhesive layer at all, and the effect of the present invention is not demonstrated. Hence it is preferable that all or a part of the base film is adhesive.
Depending on how the object and the apparatus are set, the partition layer and the adhesive layer may be disposed without the base film, therefore the base film 703 can be used when necessary.

According to the configuration of Embodiment 4, the spread of the matching gel or the like can be prevented while demonstrating the effect of the adhesive layer that fixes the positional relationship.

(Embodiment 5)
In each embodiment described above, the acoustic matching material is assumed to be matching gel, water or the like. However handling liquid is troublesome, since cleaning is required and the subject may feel uncomfortable. In Embodiment 5, urethane gel or an agar-agar like solid is used instead of such liquid as matching gel and water.

Fig. 8A and Fig. 8B are diagrams depicting an adhesive layer according to Embodiment 5. Fig. 8A is a plan view of the adhesive layer. The reference numeral 801 indicates a segment that has an adhesive function, and 802 indicates an acoustic matching material constituted by urethane gel or an agar-agar like solid material. Fig. 8B is a cross-sectional view at the A-A’ line when the adhesive layer is viewed from the side. The

reference numerals

801 and 802 indicate the same segments as Fig. 8A. In Fig. 8, the matching material is thicker than the adhesive layer so that the matching material contacts the object with certainty, but the matching material and the adhesive layer may have similar heights. The apparatus is designed in a range where the adhesive layer contacts the object by the deformation of the matching material.

By this configuration, the acoustic matching between the apparatus and the object can be performed, and the photoacoustic wave can be propagated with certainty. The acoustic matching material is preferably a material of which light absorption is low. Particularly in the case of a light focus type photoacoustic microscope, a material of which light absorption is low and scattering is low at the wavelength to be used is preferable, since the influence of light scattering is large.

The reference numeral 803 indicates a film to be a base material to support the acoustic matching material 802 and the adhesive layer 801, so that the acoustic matching material 802 and the adhesive layer 801 do not separate from each other. This film is preferably a thin and transparent member since the light and the ultrasonic wave must transmit through. In terms of transmitting the ultrasonic wave, thickness is preferably 200 μm or less. The base film 803 has a structure that contacts the object or the apparatus, and if the base film 803 is slippery, this is the same as having no adhesive layer at all, and the effect of the present invention is not demonstrated. Hence it is preferable that all or a part of the base film is adhesive.
Depending on how the object and the apparatus are set, the partition layer and the adhesive layer may be disposed without the base film, therefore the base film 803 can be used when necessary.

The adhesiveness of the acoustic matching material 802 and the adhesive layer 801 used for Embodiment 5 may deteriorate due to the adherence of dirt in the air and due to the adherence of oil depending on the storage state, which may make it difficult to provide the predetermined functions. Moreover, the acoustic matching material 802 and the adhesive layer 801 contact human skin directly, hence both must be hygienic. Therefore it is preferable to use a film to protect the acoustic matching material 802 and the adhesive layer 801. It is even more preferable to seal everything, including the base film, matching material and adhesive layer, in a vinyl or laminated film container.

Fig. 9 shows an example of the film. The

protective films

804 and 806 are disposed on the adhesive layer 801 and the acoustic matching material 802 respectively. It is preferable to dispose pull-

tabs

805 and 807 so that the protective films can be easily peeled off. In the same manner, it is preferable to dispose a protective film on an adhesive portion of the base film 803. The adhesive layer having the base film is preferably disposable and replaceable with a new base film for each measurement. Thereby a good hygienic state can be maintained, and handling becomes easier when only a fixing unit is distributed in the market.
Protection of the acoustic matching material and the adhesive layer can be in any form as long as it can be stored regardless the external environment, and is not limited to a protective film, and a container dedicated to the composing members of the present invention may be used.

According to the configuration of Embodiment 5, the problem of using liquid acoustic matching material can be prevented, while maintaining the effect of the adhesive layer to fix the positional relationship.

(Embodiment 6)
In Embodiment 6, another mode of the fixing unit will be described using an example of the ultrasonic focus type photoacoustic microscope again. Fig. 10 is a block diagram depicting a configuration of the apparatus of Embodiment 6. A same composing element as Fig. 1 is denoted with a same number, for which description is simplified.

As illustrated in Fig. 10, a cylindrical partition (first partition) is disposed in the lower part of the water tank 116, so as to include a region to perform photoacoustic measurement on the object 113. The inside of the partition is called "first space 131". A cylindrical partition (second partition) is disposed so as to include the first space 131, and the space between this partition and the first space 131 is called "second space 132". Fig. 11 shows the state when this structure is viewed from the lower side (object side). Here the partition type structure is described as an example, but the present invention is not limited to this if the structure can create a space having some degree of air tightness with the object.
The upper part of these spaces is sealed by the bottom surface of the water tank 116. The lower part of the space is open. When the photoacoustic measurement is performed, the opening at the lower part of the first space 131 and the second space 132 is closed by contacting the surface of the object 113.

The photoacoustic microscope apparatus of Embodiment 6 includes a gel supply unit 133, a gel collecting unit 134, and an air suction unit 135. The gel supply unit 133 supplies matching gel, used for matching the acoustic impedance of the photoacoustic wave 114 excited inside the object 113, to the first space 131 via a duct. The gel collecting unit 134 is connected to the first space 131 via the duct. The gel collecting unit 134 releases air from a first area so as to fill in gel smoothly, or collects the used gel from the first space.

The air suction unit 135 is connected to the second space via a duct. The air suction unit 121 sucks air to make the inside of the second space to be negative pressure, and using the atmospheric pressure difference, sucks the air of the suction region where the opening at the lower part of the second space and the surface of the object 113 contact. Thereby the surrounding region on the surface of the object 113, for which the photoacoustic measurement is performed, is fixed. In the embodiments using the air suction unit, the suction region corresponds to the fixing region of the present invention.

The first space and the second space may be constructed as illustrated in Fig. 12. Fig. 12 is also a view of each space from the object 113 side. In this case, the first space 131, to fill gel in, and the second space 132, to suck air from, are spatially separated without sharing a partition. Furthermore, the second space is divided into a plurality of spaces, each of which is connected to the air suction unit 135.
In Embodiment 6, the second space for fixing the object to the water tank by negative pressure may be regarded as the fixing unit, or the second space and the air suction unit together may be regarded as the fixing unit.

In this description, the first space 131 for filling in the matching gel has a partition structure where only the lower part is open. However, when the bottom surface of the water tank 116 and the object 113 are in close proximity, the matching gel can be stably held without the partition structure. Here the first space may be an open space. In this case, the matching gel is coated onto a region including the measuring region, so that the matching gel exists between the water tank 116 and the object 113 when the measurement is performed. Even in this state, the object 113 can be fixed using the atmospheric pressure difference of the second space. In this case, the gel collecting unit is not always required.

The member surrounded by the dashed line frame 126 in Fig. 10 is disposed on an automatic stage (not illustrated), so as to be scanned on the two-dimensional surface. The depth of the ultrasonic focal point of the probe 115 inside the object 113 can be adjusted by a mechanism (not illustrated) that adjusts the position in a direction that is orthogonal to the two-dimensional surface. The measuring control unit 102 not only performs emission control of the pulsed light source 101, but also performs the above mentioned control of the automatic stage (not illustrated) and the data sampling of the data acquisition board 110.

(Processing flow)
The processing flow of Embodiment 6 will be described with reference to Fig. 13.
In step S1301, the object 113 is set and fixed by air suction to control the movement of the measuring region during measurement. A concrete fixing procedure is as follows. First the opening at the lower part of the space 117 in Fig. 1 is positioned to include the measuring region of the object, and the opening is closed by the surface of the object. In this state, the opening at the lower part of the second space 132 is also closed by the surface of the object surrounding the measuring region. Then the air in the sealed second space is sucked out by the air suction unit 135, so as to fix the surface of the object 113. After fixing, the matching gel is supplied from gel supply unit 133 to the sealed first space 131 until the first space 131 is filled. At this time, the matching gel can be smoothly filled by the gel collecting unit appropriately sucking air existing in the first space. The gel may be supplied by the pressure difference created by the gel collecting unit actively sucking air.

In the above processing, if the first space 117 is open without having a partition structure, the matching gel may be coated before the positioning. In this case, the matching gel is coated onto the region including the measuring region, so that the matching gel exists between the water tank 116 and the object 113.

In step S1302, the measuring parameters for operating each measuring apparatus from the measuring control unit 102 are set. In concrete terms, the measuring parameters are: the measuring pitch of the photoacoustic measurement; the range of the measuring region; the sampling frequency to store the photoacoustic signal per location; storing time; scanning speed of the automatic stage; acceleration; and emission frequency, light quantity, wavelength or the like of the pulsed light source 101.

In step S1303, the depth of the acoustic focal point of the probe 115 in the object 113 is adjusted to perform the photoacoustic measurement. This adjustment is performed by a height adjustment mechanism that can adjust in a direction that is orthogonal to the two-dimensional surface where the above mentioned stage scanning is performed. This depth is adjusted in accordance with the depth in the object from the surface when the clearest image is acquired. However the deeper the position in the object the more difficult clear imaging becomes, due to scattering and attenuation of the photoacoustic wave caused by the internal tissue of the object and by the diffusion of the pulsed light 104 inside the object. Therefore in the depth adjustment, the depth is experimentally set in advance considering this characteristic.

In step S1304, the photoacoustic measurement is performed at each measuring position in the measuring region, with reference to the measuring parameters and the range of the measuring region that are set. The processing timing in this case is the same as the chart in Fig. 4. The subsequent signal processing and the display processing are executed in the same manner as Embodiment 1 described with reference to Fig. 3.

According to the fixing unit using the suction force of air as described in Embodiment 6, the motion of the measuring target can be controlled by a simple configuration, and the specific information inside the object can be imaged at high resolution.

(Addition of preferred configuration)
A preferred configuration of the air suction unit 135 will be described with reference to Fig. 14. A negative pressure generation unit 1402 is connected with the second space 132 via a duct 1401. A negative pressure state can be generated in the negative pressure generation unit using a vacuum pump or the like. The atmostpheric pressure inside the negative pressure generation unit 1402 is monitored by an atmospheric pressure control unit 1403 and is controlled to implement a desired value.
Further, the atmospheric pressure control unit controls the open/close of an air valve 1404, which is disposed in the duct 1401 and opened for emergencies. In concrete terms, when the pressure in the negative pressure generation unit 1402 drops to a predetermined value or less, the atmospheric pressure control unit 1403 performs an operation to open the air valve 1404 blocking the external atmosphere and the inside of the duct 1401, so that the atmospheric pressure in the duct 1401 becomes the same as the external atmosphere. By this operation, the atmospheric pressure in the duct does not drop very much, even during emergencies, and safety of the object is guaranteed.

The atmospheric pressure that is set by the atmospheric pressure control unit is preferably changed depending on the surface of the object. If the object is a mucous membrane, the atmospheric pressure is set to a value in the -several kPa to -25 kPa range, and if the object is normal skin, the atmospheric pressure is set to a value in the -20 kPa to -50 kPa range. However the atmospheric pressure can be set to a negative pressure outside these ranges, while considering the state of the object.
It is effective to detect the atmospheric pressure in the second space, in terms of maintaining the atmospheric pressure in an appropriate range that is determined based on the characteristics of the object, the physical properties of the material constituting the space or the like, and fixing the object efficiently.

(Embodiment 7)
A configuration of a photoacoustic microscope apparatus according to Embodiment 7 will be described with reference to Fig. 15. In Embodiment 7, a suction pad 1501 is used as the fixing unit for the object 113. By pushing the suction pad 1501 against the object 113, the air inside the suction pad is released, and the object 113 and the suction pad 1501 stick to each other. This means that in Embodiment 7, the air suction unit, as shown in Embodiment 6, is unnecessary. The suction pad 1501 fixes the object by contacting to the surface of the object outside the region where the photoacoustic measurment is performed. This portion is called the "suction pad contact region", and in an embodiment where a suction pad is used, this suction pad contact region corresponds to the fixing region of the present invention.

To match the acoustic impedance of the photoacoustic wave, matching gel 1502 is held in an open space between the surface of the object 113 and the water tank 116 in Fig. 15. However the matching method is not limited to this. For example, instead of the matching gel 1502, the partition member surrounding the first space 131, the gel supply unit 133, and the gel collecting unit 134 may be disposed as in the case of Embodiment 6.

In the configuration using the suction pad according to Embodiment 7 as well, the object can be fixed to the water tank using the suction force of the air, hence the motion of the measuring target can be controlled with a simple configuration, and the specific information inside the object can be imaged at high resolution.

(Embodiment 8)
In Embodiment 6, the photoacoustic microscope in which the air suction unit sucks air inside the closed space and the object is contacted to the water tank by this negative pressure was described. In Embodiment 7, the photoacoustic microscope in which the object is contacted to the water tank using the suction pad was used. In Embodiment 8, these fixing units are applied to a photoacoustic tomography apparatus.

The photoacoustic tomography apparatus of Embodiment 8 has a same configuration as the apparatus of Embodiment 2 described with reference to Fig. 5, and the apparatus of Embodiment 3 described with reference to Fig. 6, but a difference is that a suction mechanism or a suction pad is included as the fixing unit instead of the adhesive layer. By this configuration as well, the influence of body motion of the object can be minimized when the photoacoustic tomography measurement is performed, and good images can be acquired. A sequence of the flow from the light irradiation to data acquisition and image reconstruction, and the configuration of the apparatus required for the photoacoustic tomography are the same as Embodiments 2 and 3.

(Embodiment 9)
In Embodiment 9, an example of applying the above mentioned fixing unit, which reduces the body motion of the object by the atmospheric pressure to a photoacoustic tomography apparatus that uses a hand held type probe, will be described. In Fig. 16 as well, a composing element the same as the above embodiments is denoted with a same number, for which description is simplified.

The apparatus of Embodiment 9 is a hand held type apparatus, where an array type probe 1602, in which receiving elements are one-dimensionally or two-dimensionally arrayed, is supported by a casing 1603. The casing 1604 includes a grip portion 1604 for the user (e.g. physician, technician) to hold. An advantage of this apparatus is that it is highly portable. Moreover, the use of an array type probe can shorten the measuring time, expand the measuring region, and improve the SN ratio. On the other hand, the hand held type is more easily influenced not only by body motion, but also by hand shaking, since the user holds the casing by hand. Therefore there is a heightened necessity for the fixing unit to control the change in the positional relationship between the probe of the apparatus and the object.

In the example in Fig. 16, an optical path 1601, to transmit the pulsed light, is disposed inside the casing 1603, and the object 113 is irradiated with the light from the irradiation end near the center of the probe via the matching gel 1604 filled in the first space. The light irradiation method is not limited to the one illustrated in Fig. 16. Light may be radiated from the side face of the probe, for example, or may be radiated from a distant position.

With the apparatus having this hand held type probe as well, the influence of body motion can be controlled and good images can be acquired by using the air suction unit 135 which fixes the object and the probe by controlling the atmospheric pressure in the second space. Further, matching the acoustic impedance can be maintained by disposing the gel supply unit 133 and the gel collecting unit 134. The fixing unit combined with the hand held type probe is not limited to this, and the hand held type probe may be fixed by using the suction pad or the adhesive layer.

According to the object information acquiring apparatus disclosed in this description, even if the object is a living organism, the burden on the living body can be reduced, and stable images can be acquired. Therefore according to the present invention, the optical characteristic value distribution inside the living body and the concentration distribution of the substance constituting the biological tissue acquired from this information can ideally be imaged. Therefore the present invention can be applied to medical image diagnostic apparatuses, health apparatuses, cosmetic apparatuses and biometric authentication devices. Furthermore, the present invention can be used to diagnose tumors, vascular diseases or the like, and for follow up observation of chemotherapy. Applications to non-destructive inspections for xenobiotic objects are easily implemented by an individual skilled in the art. As described above, the present invention can be widely used as an inspection apparatus.

Other Embodiments
Embodiments of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions recorded on a storage medium (e.g., non-transitory computer-readable storage medium) to perform the functions of one or more of the above-described embodiment(s) of the present invention, and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more of a central processing unit (CPU), micro processing unit (MPU), or other circuitry, and may include a network of separate computers or separate computer processors. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)^TM), a flash memory device, a memory card, and the like.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No. 2014-198427, filed on September 29, 2014, which is hereby incorporated by reference herein in its entirety.

Claims

An object information acquiring apparatus, comprising:
a light source;
an optical system that irradiates an object with light from the light source and generates an acoustic wave;
a probe that receives the acoustic wave propagated from a measuring region in the object and converts the acoustic wave into an electric signal;
a signal processing unit that acquires specific information of the object using the electric signal; and
a fixing unit that is disposed in a fixing region surrounding the measuring region in the object, and fixes the object in a position where the probe can receive the acoustic wave propagated from the measuring region.
The object information acquiring apparatus according to Claim 1, wherein
the fixing unit is an adhesive layer that fixes the object by adhesion.
The object information acquiring apparatus according to Claim 2, wherein
the adhesive layer fixes the object by a double sided tape or glue.
The object information acquiring apparatus according to Claim 2 or 3, further comprising an acoustic matching material that is disposed in the measuring region surrounded by the adhesive layer, in accordance with a thickness of the adhesive layer.
The object information acquiring apparatus according to Claim 4, wherein
the acoustic matching material is liquid, and
the object information acquiring apparatus further comprises a partition structure disposed between the adhesive layer and the measuring region.
The object information acquiring apparatus according to Claim 4, wherein
the acoustic matching material is solid.
The object information acquiring apparatus according to Claim 1, wherein
the fixing unit includes a structure that contacts the object and creates a space with the object, and
an air suction unit that sucks air from the space.
The object information acquiring apparatus according to Claim 7, wherein
the structure includes a first partition that creates a first space with the measuring region of the object, and a second partition that creates a second space with the fixing region of the object and the first partition, and
the air suction unit sucks air from the second space.
The object information acquiring apparatus according to Claim 7, wherein
the structure creates a first space with the measuring region of the object, and creates a second space, which is divided into a plurality of spaces, in the fixing region of the object, and
the air suction unit sucks air from the second space.
The object information acquiring apparatus according to Claim 8 or 9, wherein
the air suction unit includes: a negative pressure generation unit that generates a negative pressure state in the second space; and an atmospheric pressure control unit that detects atmospheric pressure generated by the negative pressure generation unit, and controls the negative pressure generation unit in accordance with the atmospheric pressure.
The object information acquiring apparatus according to Claim 10, wherein
when the atmospheric pressure generated by the negative pressure generation unit drops to a predetermined value or less, the atmospheric pressure control unit controls the atmospheric pressure to be the same as an external atmosphere.
The object information acquiring apparatus according to any one of Claims 8 to 11, further comprising a supply unit that supplies liquid acoustic matching material to the first space.
The object information acquiring apparatus according to Claim 12, further comprising a collecting unit that collects the acoustic matching material from the first space.
The object information acquiring apparatus according to Claim 1, wherein
the fixing unit is a suction pad.
The object information acquiring apparatus according to any one of Claims 1 to 14, further comprising a member to match the acoustic impedance of the probe and that of the object, wherein
the fixing unit fixes a positional relationship of the fixing region and the member to match the acoustic impedance.
The object information acquiring apparatus according to Claim 15, wherein
the member to match the acoustic impedance is a water tank filled with liquid.
The object information acquiring apparatus according to Claim 15 or 16, wherein
a protective film, which can be peeled off upon measurement, is disposed on the fixing unit.
The object information acquiring apparatus according to Claim 17, wherein
the fixing unit is supported by a base film that is adhered to either the object or the member to match the acoustic impedance.
The object information acquiring apparatus according to any one of Claims 1 to 14, wherein
the probe is supported by a casing of the probe, and
the fixing unit fixes a positional relationship of the fixing region and the casing of the probe.
The object information acquiring apparatus according to Claim 19, wherein
the casing of the probe has a grip portion which a user can grip by hand.
The object information acquiring apparatus according to Claim 19 or 20, wherein
a protective film, which can be peeled off upon measurement, is disposed on the fixing unit.
The object information acquiring apparatus according to any one of Claims 19 to 21, wherein
the fixing unit is supported by a base film that is adhered to either the object or the casing of the probe.
The object information acquiring apparatus according to any one of Claims 1 to 22, further comprising an acoustic lens that focuses the acoustic wave received by the probe, wherein
the optical system radiates the light so as to include a focal region of the acoustic lens.
The object information acquiring apparatus according to any one of Claims 1 to 22, further comprising an acoustic lens that focuses the acoustic wave received by the probe, wherein
the optical system focuses the light using an objective lens, and radiates the light so that a focal region of the light is included in a focal region of the acoustic lens.
The object information acquiring apparatus according to Claim 23 or 24, further comprising a scanning unit that scans the focal region of the acoustic lens.
The object information acquiring apparatus according to any one of claims 1 to 25, wherein
the signal processing unit acquires the specific information inside the object by reconstructing an image using the electric signal.
The object information acquiring apparatus according to any one of Claims 1 to 22, further comprising a scanning unit that scans at least one of the probe and the object.
A fixing unit for an object information acquiring apparatus that receives, by a probe, an acoustic wave generated from an object irradiated with light from a light source, and acquires specific information of the object using the acoustic wave, the fixing unit fixing the object in a position where the probe can receive the acoustic wave propagated from a measuring region of the object,
the fixing unit comprising a member disposed in a fixing region surrounding the measuring region in the object.
The fixing unit according to Claim 28, wherein
a protective film, which can be peeled off upon measurement, is disposed on the fixing unit.
The fixing unit according to Claim 29, wherein
the fixing unit is supported by a base film.