WO2014192488A1

WO2014192488A1 - Photoacoustic measurement probe, and probe unit and photoacoustic measurement device provided therewith

Info

Publication number: WO2014192488A1
Application number: PCT/JP2014/061951
Authority: WO
Inventors: 覚入澤; 辻田　和宏
Original assignee: 富士フイルム株式会社
Priority date: 2013-05-29
Filing date: 2014-04-30
Publication date: 2014-12-04
Also published as: JP2014230631A

Abstract

Provided is a photoacoustic measurement probe which is capable of achieving a uniform energy density when irradiating a subject with light even when a bundle fiber is branched and a different amount of light is guided into each of the emitting units; also provided are a photoacoustic measurement device and a probe unit provided with said photoacoustic measurement probe. This photoacoustic measurement probe (11) is provided with an acoustic wave detection element (20a), a bundle fiber (40), and two emitting units (42) which emit, towards the subject (M), a measurement optical beam (L) guided by means of the bundle fiber (40). One end of the bundle fiber (40) branches to connect to each of the two emitting units (42), and the two emitting units (42) have different optical guiding structures in order to equalize the energy density during emission through the emitting units (42a and 42b) of the branched optical beams (La and Lb, respectively) made up of different amounts of light.

Description

Photoacoustic measurement probe, probe unit including the same, and photoacoustic measurement apparatus

The present invention relates to a probe for measuring a photoacoustic signal generated in a subject, a probe unit including the probe, and a photoacoustic measuring apparatus.

In recent years, non-invasive measurement methods using photoacoustic effects have attracted attention. This measurement method irradiates a subject with pulsed light having a predetermined wavelength (for example, wavelength band of visible light, near-infrared light, or mid-infrared light), and an absorbing substance in the subject is subjected to energy of the pulsed light. The photoacoustic wave, which is an elastic wave generated as a result of absorbing water, is detected, and the concentration of the absorbing substance is quantitatively measured. The absorbing substance in the subject is, for example, glucose or hemoglobin contained in blood. A technique for detecting such a photoacoustic wave and generating a photoacoustic image based on the detection signal is called photoacoustic imaging (PAI) or photoacoustic tomography (PAT).

In photoacoustic imaging, as disclosed in Patent Documents 1 and 2, for example, an acoustic wave detection unit, a plurality of light emission units disposed around the acoustic wave detection unit, and light emitted from a laser light source are emitted from each light source. In some cases, a probe including a bundle fiber that guides light to a portion is used.

JP 2012-166209 A JP 2012-179350 A

By the way, in the probe as described above, when the bundle fiber is branched and the light is guided to each light emitting portion, the energy intensity of the laser light incident on the bundle fiber has a Gaussian distribution in the first place. Even if the light beams are branched, the light amounts of the light guided to the respective light emitting portions do not necessarily match each other.

In order to eliminate this deviation in the amount of light, it is conceivable to change the arrangement of the fiber strands, but this is a complicated operation. In addition, from the viewpoint of durability of the bundle fiber, when using a bundle fiber having a thin fiber strand around a single thick fiber strand, a large amount of light is applied to the thick fiber strand. Since the portion is incident, it is difficult to eliminate the deviation of the light amount.

As described above, there is a case where the deviation of the light amount of the light guided to each light emitting part by branching the bundle fiber may be allowed to some extent. In such a case, the light is irradiated to the subject. There is a risk that the energy density will be non-uniform.

The present invention has been made in view of the above problems, and in a probe for photoacoustic measurement, even when the light amount of light guided to each light emitting portion by branching a bundle fiber is different, It is an object of the present invention to provide a photoacoustic measurement probe that can make the energy density uniform when irradiated on a subject, a probe unit including the probe, and a photoacoustic measurement apparatus.

In order to solve the above problems, the photoacoustic measurement probe of the present invention is
An acoustic wave detection element;
Bundle fiber,
Two light emitting portions for emitting the measurement light guided by the bundle fiber toward the subject,
One end of the bundle fiber is branched and connected to each of the two light emitting portions,
The two light emitting portions are branched light that is measurement light branched by a bundle fiber, and light guides different from each other so that the energy density when branched lights having different amounts of light exit the light emitting portion are equal. It has a structure.

Note that the “two light emitting portions” does not limit the number of light emitting portions of the probe to two. When the probe has three or more light emitting portions, it is sufficient to satisfy the requirements of the present invention in at least two light emitting portions selected from them.

And in the probe of the present invention, each light emitting part has a light guide member connected to the bundle fiber at one end face, and a diffusion part for diffusing the branched light emitted from the other end face of the light guide member, Regarding the light guide structure of the two light emitting portions, it is preferable that at least one of the design of the light guide member and the design of the diffusion portion is different. In this case, it is preferable that the diffusion angle of the diffusion part with the larger light amount is larger than the diffusion angle of the diffusion part with the smaller light amount. Moreover, it is preferable that the distance from the diffusion part with the larger light quantity to the emission end of the light emission part is longer than the distance from the diffusion part with a smaller light quantity to the emission end of the light emission part. Moreover, it is preferable that the length of the light guide member with the larger light amount in the light guide direction is longer than the length of the light guide member with the smaller light amount in the light guide direction.

Alternatively, in the probe of the present invention, each light emitting portion has a light guide member connected to the bundle fiber at one end surface, and only the light emitting portion with the larger light amount emitted from the other end surface of the light guide member. It is preferable to employ a configuration that further includes a diffusion part that diffuses the branched light.

In the probe of the present invention, it is preferable that the diffusing portion diffuses the light beam in an elliptical shape.

In the probe of the present invention, the bundle fiber includes a first fiber strand that forms the center portion of the bundle fiber on the non-branched side and a plurality of second fiber strands that form the outer peripheral portion around the center portion. A configuration is adopted in which a part of the second fiber strand having a diameter smaller than the diameter of the first fiber strand and another part of the second fiber strand are branched. It is preferable.

Alternatively, in the probe of the present invention, the bundle fiber includes a first fiber strand constituting the center portion of the bundle fiber on the non-branched side and a plurality of second fiber strands constituting the outer peripheral portion around the center portion. However, it is preferable to employ a configuration in which the first fiber strand is branched by a second fiber strand having a diameter smaller than that of the first fiber strand.

The probe unit of the present invention is
A light source unit having a light source that outputs measurement light, and a connection unit that optically connects the measurement light to the bundle fiber of the probe;
A probe for photoacoustic measurement connected to the connection part,
The probe includes an acoustic wave detection element, a bundle fiber, and two light emitting units that emit measurement light guided by the bundle fiber toward the subject.
The bundle fiber is branched at one end and connected to the two light emitting parts, respectively, and the measurement light is divided into two branched lights having different light amounts and guided to the two light emitting parts,
The two light emitting portions have different light guide structures, and the energy density when the branched light incident thereon is emitted from the light emitting portion is equal to each other.

In the probe unit of the present invention, each of the two light emitting portions includes a light guide member having one end face connected to the bundle fiber and a diffusion portion for diffusing the branched light emitted from the other end face of the light guide member. It is preferable that at least one of the design of the light guide member and the design of the diffusion portion is different from each other in the light guide structure of the two light emitting portions. In this case, it is preferable that the diffusion angle of the diffusion portion where the branched light having the larger light amount is incident is larger than the diffusion angle of the diffusion portion where the branched light having the smaller light amount is incident. In addition, the distance from the diffuser where the branched light with the larger light amount enters to the exit end of the light exit unit is the distance from the diffuser with the smaller amount of light incident to the exit end of the light exit unit. Longer than that is preferred. In addition, the length of the light guide member in which the branched light having the larger light amount is incident may be longer than the length of the light guide member in which the branched light having the smaller light amount is incident. preferable.

The photoacoustic measuring device of the present invention is
A probe for photoacoustic measurement;
A signal processing unit that generates a photoacoustic image based on the photoacoustic wave detected by the probe,
The probe includes an acoustic wave detection element, a bundle fiber, and two light emitting units that emit measurement light guided by the bundle fiber toward the subject.
One end of the bundle fiber is branched and connected to each of the two light emitting sections, and the measurement light is divided into two branched lights having different light amounts and guided to the two light emitting sections,
The two light emitting portions have different light guide structures, and are characterized in that energy densities are equal when branched light incident on each of the two light emitting portions is emitted from the light emitting portion.

And in the photoacoustic measuring device of the present invention, the two light emitting parts include a light guide member having one end face connected to the bundle fiber, a diffusion part for diffusing the branched light emitted from the other end face of the light guide member, and Preferably, at least one of the light guide member design and the diffuser design is different from each other in the light guide structure of the two light emitting portions. In this case, it is preferable that the diffusion angle of the diffusion portion where the branched light having the larger light amount is incident is larger than the diffusion angle of the diffusion portion where the branched light having the smaller light amount is incident. In addition, the distance from the diffuser where the branched light with the larger light amount enters to the exit end of the light exit unit is the distance from the diffuser with the smaller amount of light incident to the exit end of the light exit unit. Longer than that is preferred. In addition, the length of the light guide member in which the branched light having the larger light amount is incident may be longer than the length of the light guide member in which the branched light having the smaller light amount is incident. preferable.

In the photoacoustic measurement apparatus of the present invention, it is preferable that the signal processing unit generates a reflected acoustic image based on the reflected acoustic wave reflected in the subject.

In the probe, the probe unit, and the photoacoustic measuring device of the present invention, when two branched lights having different light amounts are incident on the two light emitting parts, the energy density of the two branched lights when the light emitting parts are emitted is The two light emitting portions have different light guide structures so as to be equal to each other. That is, the light guide structure of each light emitting part is designed to equalize the energy density of the two branched lights when they exit the light emitting part by offsetting the difference in the light quantity of the two branched lights. Yes. As a result, it is possible to make the energy density uniform when light is irradiated onto the subject even when the amount of the light guided to each light emitting portion by branching the bundle fiber is different. .

It is the schematic which shows the structure of the photoacoustic measuring device of 1st Embodiment. FIG. 2A is a schematic diagram illustrating a configuration example in the longitudinal direction of the probe, and FIG. 2B is a schematic diagram illustrating a configuration example in the short direction of the probe. FIG. 3A is a diagram showing a bundle fiber composed of one thick fiber strand and a plurality of fiber strands arranged around it, and FIG. 3B is a fusion process of the bundle fiber of FIG. 3A FIG. FIG. 4A is a schematic cross-sectional view illustrating a configuration example of the light emitting portion, and FIG. 4B is a schematic cross-sectional view illustrating another configuration example of the light emitting portion. FIG. 5A is a schematic diagram illustrating how the branched light emitted from the light emitting unit is detected by the optical sensor, and FIG. 5B is a schematic cross-sectional view illustrating the relationship between the light emitting unit and the light detection position. 6A, 6 </ b> B, and 6 </ b> C are schematic diagrams illustrating a method for adjusting the energy density when the light exit part of the branched light is emitted. 7A and 7B are schematic diagrams illustrating a method of adjusting the energy density when the number of branched fiber strands is different. It is a schematic sectional drawing which shows the other structural example of a light-projection part. It is a schematic sectional drawing which shows the other structural example of a light-projection part. It is a schematic sectional drawing which shows the other structural example of a light-projection part. It is the schematic which shows the structure of the photoacoustic measuring device of 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. In addition, for easy visual recognition, the scale of each component in the drawings is appropriately changed from the actual one.

“First Embodiment”
First, the probe, the probe unit, and the photoacoustic measuring device of the first embodiment will be described. FIG. 1 is a schematic diagram showing a configuration of the photoacoustic measurement apparatus of the present embodiment, and FIG. 2A is a schematic diagram showing a configuration example in the longitudinal direction of the probe. FIG. 2B is a schematic diagram illustrating a configuration example of the probe in the short direction.

The photoacoustic measurement device 10 of this embodiment has a photoacoustic image generation function that generates a photoacoustic image based on, for example, a photoacoustic signal. Specifically, as shown in FIG. 1, the photoacoustic measurement apparatus 10 of the present embodiment includes an ultrasonic probe (probe) 11, an ultrasonic unit 12, a laser unit 13, and a display unit 14.

<Probe>
The probe 11 irradiates the subject with ultrasonic waves and detects the acoustic wave U propagating through the subject M. That is, the probe 11 can perform irradiation (transmission) of ultrasonic waves to the subject M and detection (reception) of reflected ultrasonic waves (reflected acoustic waves) that have been reflected back from the subject M. Furthermore, the probe 11 can also detect a photoacoustic wave generated in the subject M when the absorber 65 in the subject M absorbs the laser light. In the present specification, “acoustic wave” means an ultrasonic wave and a photoacoustic wave. Here, “ultrasonic wave” means an elastic wave transmitted by the probe and its reflected wave, and “photoacoustic wave” means an elastic wave generated in the subject M due to a photoacoustic effect caused by irradiation of measurement light. means. Moreover, as the absorber 65, a blood vessel, a metal member, etc. are mentioned, for example.

For example, as shown in FIGS. 1 and 2, the probe 11 of the present embodiment is disposed so as to sandwich the transducer array 20, a bundle fiber 40 in which a plurality of optical fiber strands are bundled, and the transducer array 20. In addition, two light emitting portions 42 and a casing 45 including them are provided.

The transducer array 20 is composed of, for example, a plurality of ultrasonic transducers 20a (acoustic wave detection elements) arranged one-dimensionally or two-dimensionally. The ultrasonic transducer 20a is a piezoelectric element made of a polymer film such as piezoelectric ceramics or polyvinylidene fluoride (PVDF). The ultrasonic transducer | vibrator 20a has the function to convert the received signal into an electric signal, when the acoustic wave U is received. Further, the ultrasonic transducer 20a also generates an electrical signal when irradiated with measurement light. This electric signal is caused by the pyroelectric effect or the photoacoustic effect of the ultrasonic transducer 20a. In the present invention, the contact state between the probe 11 and the subject M may be determined based on the electrical signal (photodetection signal) generated due to the irradiation of the measurement light to the ultrasonic transducer. . These electric signals generated in the transducer array 20 are output to a receiving circuit 21 described later. The probe 11 is selected according to the imaging region from among sector scanning, linear scanning, convex scanning, and the like.

The bundle fiber 40 guides the laser beam L from the laser unit 13 to the light emitting unit 42. The bundle fiber 40 is not particularly limited, and a known fiber such as a quartz fiber can be used. For example, FIG. 3A shows a bundle fiber 40 composed of one thick fiber strand 41a and a plurality of fiber strands 41b arranged around it. In general, the optical fiber can be made of a material that is more resistant to light energy in the core portion than in the cladding portion. Therefore, in the bundle fiber as shown in FIG. 3A, since a thick fiber strand (for example, a diameter of 0.4 to 0.8 mm) is arranged in the center portion, the bundle fiber is locally in the center portion where the energy density becomes high. It can suppress that (especially end surface) is destroyed. FIG. 3B is a diagram illustrating a case where the bundle fiber of FIG. 3A is fused. In the bundle fiber subjected to the fusion treatment, the cladding of each fiber strand is fused while the outer edge shape of each fiber strand is changed. As a result, compared with a bundle fiber using an adhesive, an extra gap between fiber strands is reduced in a bundle fiber subjected to a fusion treatment. When the bundle fiber of FIG. 3A is fused, for example, the fiber element wire 41a and the fiber strand 41b change to a fiber strand 41c and a fiber strand 41d, respectively. There may be one or more thick fiber strands constituting the central portion. As shown in FIG. 1 and FIG. 2, the bundle fiber 40 branches on the output side, and the ends of the branched portions are connected to different light output portions 42. Thereby, the bundle fiber 40 divides the laser beam emitted from the laser unit 13 into two and guides it to the light emitting unit 42.

The branch format is not particularly limited. For example, the bundle fiber 40 is branched into a combination of a fiber strand 41a constituting the central portion and a part of a plurality of fiber strands 41b constituting the outer peripheral portion and other fiber strands 41b. Also good. Or you may branch into the fiber strand 41a which comprises a center part, and the some fiber strand 41b which comprises an outer peripheral part.

The light emitting part 42 is a part that irradiates the subject with the laser light guided by the bundle fiber 40. FIG. 4A is a schematic cross-sectional view illustrating a configuration example of a light emitting unit. As shown in FIG. 2 and FIG. 4A, in this embodiment, the elevation direction of the transducer array 20 (array direction of the transducer array) is such that the two light emitting sections 42 face each other with the transducer array 20 in between. In the direction perpendicular to the direction parallel to the detection surface). Further, as shown in FIG. 4B, the light emitting unit 42 may be inclined so that the light emitting axis of the light emitting unit faces the transducer array 20 side. In this case, it becomes easy to irradiate light to the region directly below the transducer array 20.

For example, in the present embodiment, the light emitting unit 42 includes a first light guide member 46, a diffusion unit 47, and a second light guide member 48. The first light guide member 46, the diffusing portion 47, and the second light guide member 48 are arranged in series with respect to the light traveling direction, for example, and are fixed by, for example, a fixed frame body (not shown). Is done.

The first light guide member 46 guides the measurement light (also referred to as branched light) divided and guided by the branched bundle fiber 40 to the diffusion unit 47. The light exit end of the branched portion of the bundle fiber 40 is optically coupled to the light entrance end of the first light guide member 46. For example, a light guide plate can be used as the first light guide member. The light guide plate is a plate that performs special processing on the surface of an acrylic plate or a quartz plate, for example, and uniformly emits light from one end surface from the other end surface.

The diffusing unit 47 diffuses the branched light emitted from the first light guide member 46. Thereby, the irradiation range of the branched light is further expanded. As the diffusion unit 47, for example, a diffusion plate can be used. Further, as the diffusion plate, a lens diffusion plate in which minute concave lenses or the like are randomly arranged on one surface of the substrate, for example, a quartz plate in which diffusion fine particles are dispersed can be used. Further, the diffusion part 47 does not have to be a member independent of the first light guide member 46. For example, a diffusion layer may be provided at the light emitting end portion of the first light guide member 46, or a diffusion surface may be provided at the light emitting end surface.

For example, the diffusing portion 47 is fixed to a fixing member (not shown) with an adhesive, but when adhering the lens diffusing plate, it is preferable to use an adhesive having high light diffusibility. This is because if the adhesive adheres to the lens diffusing surface, the light diffusibility of that portion is lost and strong light may be emitted locally. When an adhesive having light diffusibility is used, light can be diffused by the light diffusibility of the adhesive even when the adhesive adheres to the lens diffusion surface. As the adhesive, for example, an adhesive such as silicone rubber containing a white pigment can be used. An example of the white pigment is TiO ₂ . The content of TiO ₂ is preferably 1 wt% to 20 wt%. As the silicone rubber, for example, liquid rubber KE-45-W manufactured by Shin-Etsu Chemical Co., Ltd. can be used.

The second light guide member 48 emits the branched light diffused by the diffusion unit 47 toward the subject. Further, the emission end of the second light guide member 48 is fitted into the optical window portion (opening portion) of the housing 45 and fulfills the function of filling the gap. Thereby, it can prevent that a foreign material mixes in from the optical window part of the housing 45 to the inside of a housing at the time of use of a probe, or bacteria enter. Further, instead of providing the diffusion layer and the diffusion surface in the first light guide member 46, the light incident end portion and the light incident end surface of the second light guide member 48 may be provided, respectively.

In the present invention, the two light emitting portions have different light guide structures so that the energy densities when branched lights having different light amounts are emitted from the light emitting portions are equal. For example, such a structure can be realized by changing at least one of the design of the light guide member and the design of the diffusion portion. “Branched light with different amounts of light” means that the energy amount of each branched light differs by 5% or more of the maximum energy amount. A deviation of 5% or more of the maximum energy amount leads to, for example, image unevenness. Here, whether or not the energy densities of the branched lights having different light amounts (for example, two branched lights incident on the

light emitting portions

42a and 42b) are equal is determined as follows.

FIG. 5A and FIG. 5B are schematic diagrams showing a method for measuring energy density. In particular, FIG. 5A is a schematic diagram showing how the branched light (emitted light) emitted from the light emitting part 42a is detected by the optical sensor, and FIG. 5B is a schematic diagram showing the relationship between the light emitting part and the light detection position. It is sectional drawing. First, as shown in FIGS. 5A and 5B, the diameter φ of the emitted light L1 emitted from the light emitting portion 42a at a position away from the emitting end face 42s (that is, the emitting end) of the light emitting portion 42a by a predetermined distance D. The light that has passed through the aperture is detected by the optical sensor 50 to which the measuring instrument 51 is connected. Light detection is performed at a plurality of positions while moving the position of the center of the opening in the width direction (left-right direction in FIG. 5A) at intervals of 1 mm with the detection surface of the optical sensor 50 perpendicular to the optical axis AX. Is called. The movement is performed from end to end within a range W corresponding to the emission end face 42s of the light emission part 42a, that is, within a range where the end of the opening does not exceed the range W. The distance D and the diameter φ are 3 mm and 3.5 mm, respectively. In the present embodiment, the emission end face 42s of the light emission part 42a is the emission end face of the second light guide member 48a. For example, when there is no second light guide member 48a, it becomes the emission end face of the diffusion part 47a. Then, the energy density measured at each measurement position is divided by the opening area to calculate the energy density at each measurement position, and the average value L1ave thereof is calculated. Next, the average value L2ave of the energy density is calculated in the same manner for the emitted light L2 from the light emitting part 42b. When the maximum value of the energy density for each measurement position is L1max and L2max for each light emitting part, L1ave × 0.8 ≦ L2ave ≦ L1ave × 1.2 and L1max × 0.8 ≦ L2max ≦ L1max × 1 .2 satisfying both of the relational expressions, it is assumed that the energy density when the light emitting portions of the emitted lights L1 and L2 are emitted is equal. For example, a pyroelectric sensor PE10BB manufactured by OPHIR can be used as the optical sensor 50, and a display NOVAII manufactured by OPHIR can be used as the measuring instrument 51, for example.

In the present embodiment, the design (shape, size, material, arrangement, etc.) of the first light guide member 46, the design (diffusion angle, structure, arrangement, etc.) of the diffusion portion 47, and the design of the second light guide member 48 are designed. (Shape, size, material, arrangement, etc.) are appropriately determined based on the amount of branched light guided to each light emitting section. The amount of the branched light can be calculated in advance based on the specification of the light source unit 13 to which the probe 11 is attached, for example. Alternatively, the laser light may actually be incident on the bundle fiber to measure the amount of each branched light, and then each member may be appropriately selected based on the measured value.

Specifically, the energy density is adjusted as follows. 6A, 6 </ b> B, and 6 </ b> C are schematic diagrams illustrating a method of adjusting the energy density of the branched light when the light exit portion is emitted. FIG. 6A shows a state in which branched lights having different light amounts are emitted as emitted lights L1 and L2 having the same energy density as a result of being guided through the

light emitting parts

42a and 42b, respectively. 6B shows a state in which the branched light La having the larger light quantity is guided through the light emitting portion 42a and emitted as the outgoing light L1, and FIG. 6C shows the branched light Lb having the smaller light quantity emitted from the light. A state in which the light is guided through the portion 42b and emitted as the emitted light L2 is shown.

In the light emitting unit 42a, the amount of the branched light La is larger than the amount of the branched light Lb that guides the light emitting unit 42b, so that the diffusion angle of the diffusion unit 47a is set larger than the diffusion angle of the diffusion unit 47b. For example, the diffusion angle of the diffusion part 47a is 80 degrees, and the diffusion angle of the diffusion part 47b is 40 degrees. Thereby, the irradiation range of the branched light La guided through the light emitting part 42a is expanded (FIGS. 6B and 6C). Therefore, the rate of decrease in energy density is greater in the light emitting portion 42a than in the light emitting portion 42b. As a result, when the branched light La is emitted from the light emitting part 42a, the energy densities of the branched light La and the branched light Lb are matched. Of the diffused branched light, the light diffused beyond the range of the exit end face 42s of the light exit portion 42a (that is, the light leaked from a portion other than the exit end face 42s of the light exit portion 42a) passes through the optical window portion. It cannot pass through and is blocked by the inner wall of the housing 45. Therefore, it is advisable to apply a coating or the like for light absorption on the housing wall.

<Laser unit>
The laser unit 13 has, for example, a Q-switch solid-state laser light source that emits laser light L, and outputs the laser light L as light to be irradiated on the subject M. The laser unit 13 corresponds to the light source unit in the present invention. For example, the laser unit 13 is configured to output a laser beam L in response to a trigger signal from the control unit 34 of the ultrasonic unit 12. The laser unit 13 preferably outputs pulsed light having a pulse width of 1 to 100 nsec as laser light. For example, in the present embodiment, the light source of the laser unit 13 is a Q switch alexandrite laser.

The wavelength of the laser light is appropriately determined according to the light absorption characteristics of the absorber in the subject to be measured. For example, when the measurement target is hemoglobin in a living body (that is, when imaging a blood vessel), it is generally preferable that the wavelength belongs to the near-infrared wavelength region. The near-infrared wavelength region means a wavelength region of about 700 to 850 nm. However, the wavelength of the laser beam is not limited to this. The laser beam L may be a single wavelength or may include a plurality of wavelengths (for example, 750 nm and 800 nm). Furthermore, when the laser light L includes a plurality of wavelengths, the light of these wavelengths may be irradiated to the subject M at the same time, or may be irradiated while being switched alternately. The laser unit 13 may be a YAG-SHG-OPO laser or a Ti-Sapphire laser that can output laser light in the near-infrared wavelength region in addition to the alexandrite laser.

<Ultrasonic unit>
The ultrasonic unit 12 includes a reception circuit 21, an AD conversion unit 22, a reception memory 23, a photoacoustic image generation unit 24, a display control unit 30, and a control unit 34. The ultrasonic unit 12 corresponds to the signal processing unit in the present invention.

The control unit 34 controls each unit of the photoacoustic measurement apparatus 10, and includes a trigger control circuit (not shown) in the present embodiment. The trigger control circuit sends an optical trigger signal to the laser unit 13 when the photoacoustic measurement device is activated, for example. As a result, in the laser unit 13, the flash lamp is turned on and excitation of the laser rod is started. And the excitation state of a laser rod is maintained and the laser unit 13 will be in the state which can output a pulse laser beam.

Then, the control unit 34 transmits a Qsw trigger signal from the trigger control circuit to the laser unit 13. That is, the control unit 34 controls the output timing of the pulsed laser light from the laser unit 13 by this Qsw trigger signal. In the present embodiment, the control unit 34 transmits the sampling trigger signal to the AD conversion unit 22 simultaneously with the transmission of the Qsw trigger signal. The sampling trigger signal is a cue for the start timing of the photoacoustic signal sampling in the AD converter 22. As described above, by using the sampling trigger signal, it is possible to sample the photoacoustic signal in synchronization with the output of the laser beam.

The receiving circuit 21 receives the photoacoustic signal detected by the probe 11. The photoacoustic signal received by the receiving circuit 21 is transmitted to the AD converter 22.

The AD converter 22 samples the photoacoustic signal received by the receiving circuit 21 and converts it into a digital signal. The AD converter 22 samples the photoacoustic signal received at a predetermined sampling period based on, for example, an AD clock signal having a predetermined frequency input from the outside.

The reception memory 23 stores the photoacoustic signal sampled by the AD conversion unit 22. Then, the reception memory 23 outputs the photoacoustic signal data detected by the probe 11 to the photoacoustic image generation unit 24.

For example, the photoacoustic image generation unit 24 reconstructs data for one line by adding the photoacoustic data stored in the reception memory 23 to each other with a delay time corresponding to the position of the ultrasonic transducer. The tomographic image (photoacoustic image) data is generated based on the photoacoustic data. In addition, this photoacoustic image generation part 24 may replace with a delay addition method, and may perform a reconfiguration | reconstruction by CBP method (Circular BackBack Projection). Alternatively, the photoacoustic image generation unit 24 may perform reconstruction using a Hough transform method or a Fourier transform method. The photoacoustic image generation unit 24 outputs the photoacoustic image data generated as described above to the display control unit 30.

The display control unit 30 displays the photoacoustic image on the display unit 14 such as a display device based on the photoacoustic image data acquired from the photoacoustic image generation unit 24. When a plurality of photoacoustic images are acquired by the probe 11 having a transducer array in which the probe 11 is arranged two-dimensionally or by probe scanning, for example, the display control unit 30 obtains volume data based on the photoacoustic images. It is also possible to create and display the composite image on the display unit 14 as a three-dimensional image.

As described above, in the probe, the probe unit, and the photoacoustic measurement device of the present embodiment, the two light emitting units have the same energy density when the branched lights having different light amounts are emitted from the light emitting unit. It has a different light guide structure. In other words, the light guide structure of each light emitting part is designed to equalize the energy density of the two branched lights when emitted from the light emitting part by offsetting the difference in the light quantity of the two branched lights. Yes. As a result, it is possible to make the energy density uniform when light is irradiated onto the subject even when the amount of the light guided to each light emitting portion by branching the bundle fiber is different. .

<Design changes>
In the above embodiment, the case where the diffusion angle of the diffusion unit 47a is set to be uniformly large has been described, but the present invention is not limited to this. 7A and 7B are schematic diagrams illustrating a method of adjusting the energy density when the number of branched fiber strands is different. For example, as shown in FIGS. 7A and 7B, when the number of fiber strands 41e connected to the light emitting portion 42a side is smaller than the number of fiber strands 41f connected to the light emitting portion 42b side. The diffusing unit 47a may be configured to diffuse the branched light in an elliptical shape so that the major axis of the ellipse is along the arrangement direction of the transducer array 20. For example, the diffusion angle in the major axis direction and the minor axis direction of the diffusion part 47a is 60 degrees and 1 degree, respectively, and the diffusion angle of the diffusion part 47b is 30 degrees. In this case, as shown in FIG. 7A, when the number of fiber strands connected to the light emitting portion is small, there is an advantage that the light irradiation range can be expanded in the arrangement direction of the transducer array 20. For example, it is effective when a bundle fiber as shown in FIG. 3A or 3B is used and the fiber strand is divided into a central portion and an outer peripheral portion.

In the above embodiment, the case where the energy density is adjusted by the difference in the diffusion angle of the diffusion portion has been described, but the present invention is not limited to this. For example, as shown in FIG. 8, the first light guide member 46 and the diffusing portion 47 are the same in both light emitting portions 42 with respect to the structure itself, but in the light guide direction of the second light guide member. A configuration in which the length, that is, the distance from the diffusion portion 47 to the emission end of the light emission portion 42 is different can be employed. Specifically, the distance X1 (for example, 15 mm) from the diffusing portion 47 of the light emitting portion where the branched light La having the larger light amount is incident to the emitting end is the light emitting portion where the branched light Lb having the smaller light amount is incident. Is set to be longer than a distance X2 (for example, 2 mm) from the diffusion portion 47 to the emission end. Even in this case, the irradiation range of the branched light La guided through the light emitting portion 42 is wider than the irradiation range of the branched light Lb (FIG. 8). As a result, when the branched light La is emitted from the light emitting portion 42, the energy densities of the branched light La and the branched light Lb are matched.

For example, as shown in FIG. 9, the diffusion portion 47 and the second light guide member 48 are the same in both light emitting portions 42, but the length of the first light guide member in the light guide direction is the same. Different configurations can be adopted. Specifically, the length Y1 (for example, 60 mm) of the first light guide member 46a of the light emitting portion where the branched light La having a larger amount of light is incident is the light emission where the branched light Lb having a smaller amount of light is incident. It is set longer than the length Y2 (for example, 20 mm) of the first light guide member 46b. In this case, the branched light La traveling through the first light guide member 46a repeats more reflections within the light guide member than the branched light Lb traveling through the light guide member 46b, and the light guide member 46a is The range of the emission angle of the branched light La when emitted is wider than the range of the emission angle of the branched light Lb when emitted from the light guide member 46b. Therefore, even in this case, the irradiation range of the branched light La guided through the light emitting portion 42 is wider than the irradiation range of the branched light Lb. As a result, when the branched light La is emitted from the light emitting portion 42, the energy densities of the branched light La and the branched light Lb are matched.

Further, for example, as shown in FIG. 10, it is also possible to adopt a configuration in which a diffusion part is not provided in the light emitting part where the branched light having the smaller light quantity is incident. For example, the light emitting part into which the branched light having the larger light quantity is incident is composed of the first light guide member 46, the diffusing part 47, and the second light guiding member 48, and the light into which the branched light having the smaller light quantity is incident. The emission part is composed of only one light guide member 49. Even in this case, the irradiation range of the branched light La having a larger amount of light guided through the light emitting section 42 is wider than the irradiation range of the branched light Lb. As a result, when the branched light La is emitted from the light emitting portion 42, the energy densities of the branched light La and the branched light Lb are matched.

“Second Embodiment”
Next, a probe, a probe unit, and a photoacoustic measurement apparatus according to the second embodiment will be described. FIG. 11 is a schematic diagram illustrating the configuration of the photoacoustic measurement apparatus according to the second embodiment. This embodiment is different from the first embodiment in that an ultrasonic image is generated in addition to the photoacoustic image. Therefore, a detailed description of the same components as those in the first embodiment will be omitted unless particularly necessary.

The photoacoustic measurement apparatus 10 of this embodiment includes an ultrasonic probe (probe) 11, an ultrasonic unit 12, a laser unit 13, and a display unit 14. The ultrasonic probe (probe) 11, the laser unit 13, and the display unit 14 are the same as those in the first embodiment.

<Ultrasonic unit>
The ultrasonic unit 12 of the present embodiment includes an ultrasonic image generation unit 29 and a transmission control circuit 33 in addition to the configuration of the photoacoustic measurement apparatus shown in FIG.

In the present embodiment, in addition to the detection of the photoacoustic signal, the probe 11 outputs (transmits) ultrasonic waves to the subject and detects reflected ultrasonic waves (reflected acoustic waves) from the subject with respect to the transmitted ultrasonic waves (reflected acoustic waves). Receive). As the ultrasonic transducer for transmitting and receiving ultrasonic waves, the ultrasonic transducer according to the present invention may be used, or a new ultrasonic transducer separately provided in the probe 11 for transmitting and receiving ultrasonic waves is used. May be. Moreover, you may perform transmission / reception of an ultrasonic wave from the structure isolate | separated. For example, ultrasonic waves may be transmitted from a position different from the probe 11, and reflected ultrasonic waves with respect to the transmitted ultrasonic waves may be received by the probe 11.

When the ultrasonic image is generated, the control unit 34 sends an ultrasonic transmission trigger signal to the transmission control circuit 33 to instruct ultrasonic transmission. Upon receiving this trigger signal, the transmission control circuit 33 transmits an ultrasonic wave from the probe 11. The probe 11 detects the reflected ultrasonic wave from the subject after transmitting the ultrasonic wave.

The reflected ultrasonic waves detected by the probe 11 are input to the AD conversion unit 22 via the reception circuit 21. The control unit 34 sends a sampling trigger signal to the AD conversion unit 22 in synchronization with the timing of ultrasonic transmission to start sampling of reflected ultrasonic waves. The AD converter 22 stores the reflected ultrasound sampling signal in the reception memory 23. Either sampling of the photoacoustic signal or sampling of the reflected ultrasonic wave may be performed first.

The ultrasonic image generation unit 29 performs signal processing such as reconstruction processing, detection processing, and logarithmic conversion processing based on the reflected ultrasonic waves (its sampling signals) detected by the plurality of ultrasonic transducers of the probe 11. Generate ultrasonic image data. For the generation of the image data, a delay addition method or the like can be used similarly to the generation of the image data in the photoacoustic image generation unit 24.

The display control unit 30 causes the display unit 14 to display, for example, a photoacoustic image and an ultrasonic image separately or a composite image thereof. The display control unit 30 performs image composition by superimposing a photoacoustic image and an ultrasonic image, for example.

In the present embodiment, the photoacoustic measurement device generates an ultrasonic image in addition to the photoacoustic image. Therefore, in addition to the effects of the first embodiment, by referring to the ultrasonic image, a portion that cannot be imaged by the photoacoustic image can be observed.

DESCRIPTION OF SYMBOLS 10 Photoacoustic measuring device 11 Probe 12 Ultrasonic unit 13 Laser unit 14 Display part 20 Transducer array 20a Ultrasonic vibrator 21 Reception circuit 22 AD conversion part 23 Reception memory 24 Photoacoustic image generation part 29 Ultrasonic image generation part 30 Display Control unit 33 Transmission control circuit 34 Control unit 40 Bundle fibers 41a to 41f Fiber strand 42 Light emitting unit 45 Housing 46 First light guide member 47 Diffusing unit 48 Second light guide member L Laser light La, Lb Branched light M Subject U Acoustic wave

Claims

An acoustic wave detection element;
Bundle fiber,
Two light emitting portions for emitting the measurement light guided by the bundle fiber toward the subject,
The bundle fiber is branched at one end and connected to the two light emitting parts, respectively, and the measurement light is divided into two branched lights having different light amounts and guided to the two light emitting parts, respectively.
The probe for photoacoustic measurement, wherein the two light emitting portions have different light guide structures, and energy density when the branched light incident on each of the two light emitting portions is emitted from the light emitting portion is equal to each other .
The two light emitting parts each have a light guide member having one end face connected to the bundle fiber, and a diffusion part for diffusing the branched light emitted from the other end face of the light guide member,
2. The probe according to claim 1, wherein the light guide structures of the two light emitting portions are different from each other in at least one of a design of the light guide member and a design of the diffusion portion.
3. The probe according to claim 2, wherein a diffusion angle of the diffusion portion where the branched light having a larger light amount is incident is larger than a diffusion angle of the diffusion portion where the branched light having a smaller light amount is incident.
The distance from the diffuser where the branched light with the larger light quantity enters to the exit end of the light exit part is from the diffuser where the branched light with the smaller light quantity enters to the exit end of the light exit part. The probe according to claim 2 or 3, which is longer than the distance of.
The length in the light guide direction of the light guide member on which the branched light having the larger light amount is incident is longer than the length in the light guide direction of the light guide member on which the branched light having the smaller light amount is incident. Item 5. The probe according to any one of Items 2 to 4.
The two light emitting portions each have a light guide member having one end face connected to the bundle fiber,
2. The probe according to claim 1, wherein only the light emitting portion into which the branched light having a larger amount of light enters further has a diffusion portion that diffuses the branched light emitted from the other end surface of the light guide member.
The probe according to any one of claims 2 to 6, wherein the diffusion unit is capable of diffusing a light beam in an elliptical shape.
The bundle fiber is a first fiber strand constituting a center portion of the bundle fiber on the non-branched side and a plurality of second fiber strands constituting an outer peripheral portion around the center portion, and 8. The method according to any one of claims 1 to 7, wherein the branching is made into a part of a set of second fiber strands whose diameter is smaller than a diameter of the fiber strand and another part of a pair of second fiber strands. The probe as described.
The bundle fiber includes a first fiber strand that forms a center portion of the bundle fiber on a non-branched side, and a plurality of second fiber strands that form an outer peripheral portion around the center portion. The probe according to any one of claims 1 to 7, wherein the probe branches off into a second fiber strand having a diameter smaller than that of the one fiber strand.
A light source unit having a light source that outputs measurement light, and a connection unit that optically connects the measurement light to a bundle fiber of the probe;
A probe for photoacoustic measurement connected to the connection part,
The probe includes an acoustic wave detection element, a bundle fiber, and two light emitting units that emit the measurement light guided by the bundle fiber toward a subject,
The bundle fiber is branched at one end and connected to the two light emitting parts, respectively, and the measurement light is divided into two branched lights having different light amounts and guided to the two light emitting parts, respectively.
The probe unit characterized in that the two light emitting parts have different light guide structures, and the energy density when the branched light incident on each of the two light emitting parts is emitted from the light emitting part is equal to each other.
The two light emitting parts each have a light guide member having one end face connected to the bundle fiber, and a diffusion part for diffusing the branched light emitted from the other end face of the light guide member,
The probe unit according to claim 10, wherein the light guide structures of the two light emitting portions are different from each other in at least one of a design of the light guide member and a design of the diffusion portion.
The probe unit according to claim 11, wherein a diffusion angle of the diffusing portion where the branched light having a larger light amount is incident is larger than a diffusion angle of the diffusing portion where the branched light having a smaller light amount is incident.
The distance from the diffuser where the branched light with the larger light quantity enters to the exit end of the light exit part is from the diffuser where the branched light with the smaller light quantity enters to the exit end of the light exit part. The probe unit according to claim 11 or 12, which is longer than the distance.
The length in the light guide direction of the light guide member on which the branched light having the larger light amount is incident is longer than the length in the light guide direction of the light guide member on which the branched light having the smaller light amount is incident. The probe unit according to any one of 11 to 13.
A probe for photoacoustic measurement;
A signal processing unit that generates a photoacoustic image based on the photoacoustic wave detected by the probe,
The probe includes an acoustic wave detection element, a bundle fiber, and two light emitting units that emit measurement light guided by the bundle fiber toward a subject.
The bundle fiber is branched at one end and connected to the two light emitting parts, respectively, and the measurement light is divided into two branched lights having different light amounts and guided to the two light emitting parts, respectively.
The two light emitting units have different light guide structures, and the energy density when the branched light incident on each of the two light emitting units is emitted from the light emitting unit is equal to each other.
The two light emitting parts each have a light guide member having one end face connected to the bundle fiber, and a diffusion part for diffusing the branched light emitted from the other end face of the light guide member,
The photoacoustic measuring device according to claim 15, wherein the light guide structures of the two light emitting units are different from each other in at least one of a design of the light guide member and a design of the diffusion unit.
17. The photoacoustic measurement according to claim 16, wherein a diffusion angle of the diffusing portion where the branched light having the larger light amount is incident is larger than a diffusion angle of the diffusing portion where the branched light having the smaller light amount is incident. apparatus.
The distance from the diffuser where the branched light having the larger light quantity enters to the exit end of the light emitting part is the exit of the light emitting part from the diffuser where the branched light having the smaller light quantity is incident. The photoacoustic measuring device of Claim 16 or 17 longer than the distance to an end.
The length in the light guide direction of the light guide member into which the branched light having the larger light amount is incident is longer than the length in the light guide direction of the light guide member in which the branched light having the smaller light amount is incident. The photoacoustic measuring device of any one of Claims 16-18.
The photoacoustic measuring device according to any one of claims 15 to 19, wherein the signal processing unit generates a reflected acoustic image based on a reflected acoustic wave reflected in the subject.