JP2014184025A - Photoacoustic measuring device, probe, acoustic matching member, photoacoustic measuring method and contact determination method of probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoacoustic measuring device and a photoacoustic measuring method which can perform contact determination with an easier method in photoacoustic measurement using a probe having an acoustic matching member.SOLUTION: A photoacoustic measuring device 10 includes: a probe 11 having a light emission unit for emitting measurement light L and an acoustic wave detection element; a determination unit 28 which determines whether the probe 11 and an analyte M are in a contact state or a non-contact state; and a light intensity control unit (for example, a changeover control unit 36 and an intensity changeover unit 37) which controls the intensity of the measurement light to a first intensity or a second intensity greater than the first intensity in accordance with the determination result by the determination unit 28. The probe 11 includes an acoustic matching member partially having a light transmission part for transmitting the measurement light. The determination unit 28 performs the determination on the basis of the mode of change of a light detection signal due to the radiation of the measurement light L transmitted through the light transmission part to the acoustic wave detection element.

Description

  The present invention relates to a photoacoustic measurement device, a probe, and an acoustic matching member for performing measurement in a subject based on a photoacoustic signal generated in the subject. The present invention also relates to a photoacoustic measurement method and a probe contact determination method which are carried out using them.

  In recent years, a measurement method using a photoacoustic effect has attracted attention. This measurement method irradiates a subject with pulsed light having a predetermined wavelength (for example, a wavelength band of visible light, near-infrared light, or mid-infrared light), and a specific 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 absorption of water, is detected, and the concentration of the specific substance is quantitatively measured. The specific 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 the photoacoustic measurement as described above, a photoacoustic wave is detected by a probe including a light emitting part such as an optical fiber and an acoustic wave detecting element such as a piezoelectric element. However, when the probe as described above is used, the handling performance is improved, but there is a problem that the measurement light is emitted in an unintended direction.

  Therefore, in order to solve such a problem, for example, Patent Documents 1 to 4 make a contact determination as to whether or not the probe and the subject are in contact, and increase or decrease the intensity of the measurement light according to the determination result. Discloses a method of making them.

  Specifically, in Patent Document 1, two predetermined peaks are extracted from a detection signal from a piezoelectric sensor, contact determination is performed based on information on these peak positions, and the intensity of measurement light is determined according to the determination result. Is disclosed. Patent Document 2 or 3 discloses that contact determination is performed based on an ultrasonic image acquired immediately before, and measurement light is emitted according to the determination result. Patent Document 4 discloses that contact determination is performed based on a distance measured by a distance measuring laser beam, and measurement light is emitted according to the determination result.

JP 2009-011593 A JP 2012-187389 A JP 2012-205886 A JP 2012-187394 A

  By the way, in the photoacoustic measurement, an acoustic matching member (for example, an acoustic lens) that acoustically matches the acoustic wave detection element and the subject may be provided at the contact portion of the probe. In general, the acoustic matching member is configured to shield the measurement light as a whole in order to prevent the measurement light from becoming measurement noise. Therefore, when using a probe provided with such an acoustic matching member, contact determination cannot be performed by the method of Patent Document 1.

  The present invention has been made in view of the above problems, and in photoacoustic measurement using a probe provided with an acoustic matching member, a photoacoustic measurement apparatus, a probe, and a photoacoustic measurement apparatus that can perform contact determination by a simpler method. An object of the present invention is to provide an acoustic matching member, a photoacoustic measurement method, and a probe contact determination method.

In order to solve the above problems, the photoacoustic measurement device of the present invention is:
In a photoacoustic measurement apparatus that includes a probe having a light emitting portion that emits measurement light and an acoustic wave detection element, and that measures a photoacoustic signal from a subject caused by emission of the measurement light by the acoustic wave detection element,
A determination unit for determining whether the probe and the subject are in contact state or non-contact state;
The intensity of the measurement light is controlled to the first intensity when the determination unit determines that the probe and the subject are in a non-contact state, and the intensity of the measurement light is determined when the probe and the subject are in a contact state. A light intensity control unit that controls the second intensity greater than the first intensity,
The probe has an acoustic matching member that acoustically matches the acoustic wave detection element and the subject at the contact portion of the probe,
Of the acoustic matching member, a part facing the acoustic wave detection element is a light transmission part that transmits the measurement light, and the other region is a light shielding part that shields the measurement light,
The determination unit is characterized in that the determination is performed based on a change mode of the light detection signal caused by the irradiation of the measurement light transmitted through the light transmission unit to the acoustic wave detection element.

  In the photoacoustic measurement apparatus of the present invention, it is preferable that there are a plurality of acoustic wave detection elements, and the light transmission portion has a slit shape extending in the arrangement direction of the plurality of acoustic wave detection elements. In this case, the plurality of acoustic wave detection elements include an acoustic wave detection element for contact detection as an acoustic wave detection element facing the light transmitting portion, and an acoustic for photoacoustic measurement that detects a photoacoustic signal from the subject. It is preferable to have a wave detection element. Furthermore, a plurality of acoustic wave detecting elements for contact detection and acoustic wave detecting elements for photoacoustic measurement are arranged in plural, and a configuration in which the arrangement directions are parallel to each other can be adopted.

Further, in the photoacoustic measurement device of the present invention, when the measurement light has second component light having a wavelength different from that of the first component light used for photoacoustic measurement of the absorber in the subject,
The light transmission part transmits the second component light and blocks the first component light,
The light intensity control unit preferably controls the intensity of the measurement light by increasing or decreasing the intensity of the first component light.

  In the photoacoustic measurement apparatus of the present invention, the determination unit obtains the number of acoustic wave detection elements that detect the light detection signal based on the light detection signal, and determines the change in the number of the light detection signal. It can be handled as a change, and the above determination can be made based on the magnitude when the number is compared with the threshold number.

  In the photoacoustic measurement device of the present invention, when the change in the number is handled as the change in the light detection signal, the threshold number when determining the change from the contact state to the non-contact state is from the non-contact state to the contact state. It is preferable that it is larger than the threshold number when the change is judged. In addition, when there are a plurality of acoustic wave detection elements, it is preferable that the determination unit counts the number of only the specific acoustic wave detection elements among the plurality of acoustic wave detection elements.

  Alternatively, in the photoacoustic measurement device of the present invention, the determination unit obtains the intensity of the light detection signal based on the light detection signal, handles the change in the intensity as the change in the light detection signal, and determines the intensity and the threshold value. The above determination can be made based on the magnitude when compared with the strength.

The probe of the present invention comprises
In a probe having a light emitting portion for emitting measurement light and an acoustic wave detecting element,
An acoustic matching member that acoustically matches the acoustic wave detection element and the subject is provided in the contact portion of the probe,
Among the acoustic matching members, a part facing the acoustic wave detection element is a light transmission part that transmits the measurement light, and the other region is a light shielding part that shields the measurement light.

  In the probe of the present invention, it is preferable that there are a plurality of acoustic wave detection elements, and the light transmission portion has a slit shape extending in the arrangement direction of the plurality of acoustic wave detection elements.

  In the probe of the present invention, when the measurement light has second component light having a wavelength different from that of the first component light used for photoacoustic measurement of the absorber in the subject, the light transmitting portion It is preferable that the second component light is transmitted and the first component light is shielded.

The acoustic matching member of the present invention is
An acoustic matching member attached to a contact portion of a probe having a light emitting portion for emitting measurement light and an acoustic wave detecting element,
A part facing the acoustic wave detection element is a light transmission part that transmits the measurement light, and the other area is a light shielding part that shields the measurement light.

  In the acoustic matching member of the present invention, when the measurement light has second component light having a wavelength different from that of the first component light used for photoacoustic measurement of the absorber in the subject, light The transmission part preferably transmits the second component light and shields the first component light.

The photoacoustic measurement method of the present invention is
A probe having a light emitting portion for emitting measurement light and an acoustic wave detecting element, and further having an acoustic matching member for acoustically matching the acoustic wave detecting element and the subject at an abutting portion of the probe. Using a probe that is part of the member facing the acoustic wave detection element is a light transmission part that transmits the measurement light and the other region is a light shielding part that shields the measurement light,
Judgment whether the probe and the subject are in a contact state or a non-contact state based on the change of the light detection signal due to the irradiation of the measurement light transmitted through the light transmission part to the acoustic wave detection element Done
The intensity of the measurement light is controlled to the first intensity when it is determined that the probe and the subject are in a non-contact state, and greater than the first intensity when it is determined that the probe and the subject are in a contact state. The photoacoustic signal from the subject is measured by controlling to the second intensity.

  In the photoacoustic measurement method of the present invention, the number of acoustic wave detection elements that detect the photodetection signal is obtained based on the photodetection signal, and the change in the number is handled as the change in the photodetection signal. The above determination can be made based on the magnitude when the number and the threshold number are compared.

  Alternatively, in the photoacoustic measurement method of the present invention, the intensity of the light detection signal is obtained based on the light detection signal, the change in the intensity is treated as the change in the light detection signal, and the intensity and the threshold intensity are compared. The above determination can be made on the basis of the magnitude at the time.

The probe contact determination method of the present invention includes:
A probe having a light emitting portion for emitting measurement light and an acoustic wave detecting element, and further having an acoustic matching member for acoustically matching the acoustic wave detecting element and the subject at an abutting portion of the probe. Using a probe that is part of the member facing the acoustic wave detection element is a light transmission part that transmits the measurement light, and the other region is a light shielding part that shields the measurement light,
Judgment whether the probe and the subject are in a contact state or a non-contact state based on the change of the light detection signal due to the irradiation of the measurement light transmitted through the light transmission part to the acoustic wave detection element It is characterized by doing.

  In the probe contact determination method of the present invention, the number of acoustic wave detecting elements that detect the light detection signal is obtained based on the light detection signal, and the change in the number is handled as the change in the light detection signal. Thus, the determination can be made based on the size when the number is compared with the threshold number.

  Alternatively, in the probe contact determination method of the present invention, the intensity of the light detection signal is obtained based on the light detection signal, the change in the intensity is handled as the change in the light detection signal, and the intensity and the threshold intensity are calculated. The above determination can be made based on the magnitude of the comparison.

  The photoacoustic measuring device and probe of the present invention use an acoustic matching member having a light transmission part in part, and the acoustic matching member of the present invention has a light transmission part in a part thereof, so that the light transmission part is transmitted. The contact determination can be performed based on the change of the light detection signal caused by the irradiation of the measured light to the acoustic wave detection element. That is, according to the present invention, it is not necessary to provide other components for contact detection (for example, a contact detection sensor or a length measuring unit). As a result, in photoacoustic measurement using a probe provided with an acoustic matching member, contact determination can be performed by a simpler method.

  Since the photoacoustic measurement method and the probe contact determination method of the present invention use a probe including an acoustic matching member having a light transmission part in part, the acoustic wave detection element of the measurement light transmitted through the light transmission part It is possible to make a contact determination based on the manner of change in the light detection signal caused by irradiation of the light. As a result, in the same manner as described above, in photoacoustic measurement using a probe equipped with an acoustic matching member, it is possible to perform contact determination by a simpler method.

It is a conceptual diagram which shows the structure of the photoacoustic measuring device of 1st Embodiment. It is (a) schematic front view and (b) schematic side view which show the structure of a probe. It is a conceptual diagram which shows the structural example of an electroacoustic conversion part. It is a conceptual diagram which shows the example (when all the detection elements are used) of the contact judgment based on the number of the acoustic wave detection elements which are detecting the signal. It is a conceptual diagram which shows the example (when the detection element of both ends is used) of the contact judgment based on the number of the acoustic wave detection elements which are detecting the signal. It is a flowchart which shows the process of the photoacoustic measuring method of 1st Embodiment. It is a conceptual diagram which shows the structure of the photoacoustic measuring device of 3rd Embodiment.

  Hereinafter, although an embodiment of the present invention is described using a drawing, the present invention is not limited to this. In addition, for easy visual recognition, the scale of each component in the drawings is appropriately changed from the actual one.

“First Embodiment”
First, a photoacoustic measurement device, a probe, an acoustic matching member, a photoacoustic measurement method, and a probe contact determination method according to a first embodiment of the present invention will be described. FIG. 1 is a conceptual diagram showing the configuration of the photoacoustic measurement apparatus of the first embodiment, and FIG. 2 is a schematic front view and (b) a schematic side view showing the configuration of the probe.

  The photoacoustic measuring device 10 of this embodiment has a photoacoustic image generation function which generates a photoacoustic image based on a photoacoustic signal, for example. 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 this specification, “acoustic wave” means an ultrasonic wave and a photoacoustic wave. Here, “ultrasonic wave” means an elastic wave transmitted by the probe, and “photoacoustic wave” means an elastic wave generated in the subject M due to the photoacoustic effect caused by irradiation of the measurement light. Examples of the absorber 65 include blood vessels and metal members.

  The probe 11 of this embodiment is provided with the electroacoustic conversion part 43, the optical fiber 40, the light-guide plate 42, and the housing | casing 45 containing these, as FIG. 1 and FIG. 2 show, for example. The electroacoustic conversion unit 43 includes the acoustic matching member 19 and the transducer array 20.

  The acoustic matching member 19 is a member having an acoustic impedance between the acoustic impedance of the transducer array 20 and the acoustic impedance of the subject M, and a function of matching these two acoustic impedances. Accordingly, even a member having another function such as an acoustic lens, for example, can be used as an acoustic matching member in the present invention as long as it has a medium acoustic impedance and is provided on the subject M side of the transducer array 20. included. The acoustic matching member 19 is provided with a region that transmits the measurement light (light transmission portion 19a) and a region that blocks the measurement light (light shielding portion 19b). The light transmission part 19 a is formed to face a part of the transducer array 20 so that the measurement light transmitted through the light transmission part 19 a reaches the transducer array 20.

  For example, the transducer array 20 includes 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 is determined based on the electrical signal (light detection signal) generated due to the irradiation of the measurement light to the ultrasonic transducer in this way. 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. In addition, the transducer array 20 detects contact by detecting measurement light transmitted through the light transmission unit, separately from the ultrasonic transducer for detecting photoacoustic waves from the subject and performing photoacoustic measurement. You may have the ultrasonic vibrator for.

  FIG. 3 is a conceptual diagram illustrating a configuration example of the electroacoustic conversion unit 43. 3A to 3E are electroacoustic transducers 43 viewed from the detection surface side of the probe 11, and the right diagrams are XX of the electroacoustic transducers 43 in the left diagram. It is sectional drawing. For example, in FIG. 3a, a light transmission portion 19a is provided so as to face one ultrasonic transducer 20a in the transducer array 20, and the other portion of the transducer array 20 is covered by a light shielding portion 19b. ing. In FIG. 3a, the measurement light transmitted through the light transmitting portion 19a enters one ultrasonic transducer 20a facing the light transmitting portion 19a, and a light detection signal is generated from the ultrasonic transducer 20a.

  In FIG. 3b, a light transmission portion 19a is provided so as to face the four ultrasonic transducers 20a in the transducer array 20, and the other portions of the transducer array 20 are covered by the light shielding portion 19b. Yes. Therefore, the light detection signal is generated by the four ultrasonic transducers. Further, the light transmission part 19a is provided so as to face only a part of one ultrasonic transducer. Since the intensity of the light detection signal is usually sufficiently large, even if it is provided in this way, it can be sufficiently detected. Rather, since the presence of the light transmission part 19a can cause noise when detecting a photoacoustic wave from the subject, the light transmission part 19a is partly related to one ultrasonic transducer. It is preferable that they are provided so as to face each other only. The number of elements is not limited to four and can be selected as appropriate.

  In c and d of FIG. 3, a slit-shaped light transmission portion 19 a extending in the arrangement direction of the ultrasonic transducers is provided so as to face a part of each ultrasonic transducer 20 a in the transducer array 20. The other part of the transducer array 20 is covered with a light shielding part 19b. Therefore, the light detection signal is generated by all the ultrasonic transducers in the transducer array 20.

  In FIG. 3e, the transducer array 20 has an ultrasonic transducer 20b for contact detection and an ultrasonic transducer 20c for photoacoustic measurement, and the light transmitting portion 19a has ultrasonic vibration for contact detection. The light shielding portion 19b is formed so as to cover the other portion of the transducer array 20 so as to face the child 20b. In this way, when there are a plurality of ultrasonic transducers for contact detection and a plurality of ultrasonic transducers for photoacoustic measurement and the arrangement directions are parallel to each other, the ultrasonic transducer for contact detection is used. Since the degree of contact between the ultrasonic transducer and the subject and the degree of contact between the ultrasonic transducer for photoacoustic measurement and the subject have the same tendency, it is possible to grasp the contact state more accurately. .

  In addition, the measurement light has a first component light used for photoacoustic measurement of the absorber in the subject M, and a second having a wavelength different from the wavelength of the first component light (that is, it does not belong to this wavelength band). In the case of having the component light, the light transmitting unit 19a transmits the second component light and blocks the first component light, and the light intensity control unit measures by increasing or decreasing the intensity of the first component light. It is preferable to control the intensity of light. With this configuration, when the photoacoustic measurement is performed, all of the first component light is shielded by the acoustic matching member, so that the influence of the presence of the light transmitting portion 19a on the photoacoustic measurement can be reduced. .

  The optical fiber 40 guides the laser light L from the laser unit 13 to the light guide plate 42. The optical fiber 40 is not particularly limited, and a known fiber such as a quartz fiber can be used. For example, in this embodiment, the laser light L is guided from the laser unit 13 to the inside of the probe 11 by one optical fiber, and is branched into a plurality by the branch coupler 41 inside the probe 11, and two light guide plates described later. 42 is guided. A bundle fiber can also be used.

  The light guide plate 42 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 face from the other end face. In this embodiment, it corresponds to the light emitting portion of the present invention. As shown in FIG. 2, in the present embodiment, the elevation direction of the transducer array 20 (perpendicular to the array direction of the transducer array) so that the two light guide plates 42 face each other with the electroacoustic conversion unit 43 interposed therebetween. It is arranged on both sides in the direction parallel to the detection surface. The optical fiber 40 and the light guide plate 42 are optically coupled to each other.

  The portion of the light guide plate 42 on the side coupled to the optical fiber 40 is formed in a tapered shape, for example, as shown in FIG. Thereby, the irradiation range of measurement light can be expanded efficiently. Further, the portion of the light guide plate 42 coupled to the optical fiber 40 is preferably formed of a glass material in order to avoid damage due to light energy. On the other hand, other portions are formed of a resin material such as acrylic.

  The laser light L guided by the optical fiber 40 is incident on the light guide plate 42 and then irradiated to the subject M from the opposite end. The light guide plate 42 has a mechanism for diffusing light at the tip thereof (such as a resin containing scattering particles) or a light traveling direction on the transducer array 20 side so that a wider range of the subject M can be irradiated with the laser light L. There may be a mechanism (such as a notch for refracting light) to be directed.

  By configuring the probe 11 as described above, it is possible to accurately generate an ultrasonic image and a photoacoustic image as reflected acoustic images for the same imaging range. As a result, a complicated alignment process between the ultrasonic image and the photoacoustic image may be unnecessary.

<Laser unit>
The laser unit 13 is a light source unit that emits laser light L to be irradiated onto the subject M as measurement light. As the subject M absorbs the laser light, a photoacoustic wave is generated in the subject M. The laser light emitted from the laser unit 13 is guided to the tip of the probe 11 using light guide means such as an optical fiber 40 and is irradiated from the probe 11 to the subject M.

  For example, the laser unit 13 of the present embodiment includes a laser light source 35 such as a Q-switch alexandrite laser and a switching control unit that increases or decreases the intensity (or light amount) of the laser light L emitted from the laser light source 35 using the intensity switching unit 37. 36 and a connection portion 38 for connecting the laser light L whose intensity has been adjusted to the optical fiber 40. The switching control unit 36 and the intensity switching unit 37 correspond to the light intensity control unit in the present invention.

  For example, the intensity switching unit 37 is an ND (neutral density) filter. In this case, the intensity of the laser beam L is adjusted depending on whether or not the ND filter is inserted. Then, the switching control unit 36 controls the intensity switching unit 37 (for example, by inserting or removing an ND filter) according to the determination result of the contact determination of the determination unit 28 described later, thereby switching the light intensity. Specifically, when it is determined that the probe 11 and the subject M are in a non-contact state as a result of the contact determination, the switching control unit 36 inserts, for example, an ND filter to relatively reduce the intensity of the laser light L. Control to a small first intensity. On the other hand, as a result of the contact determination, when it is determined that the probe 11 and the subject M are in contact, the switching control unit 36 removes, for example, the ND filter and sets the intensity of the laser light L higher than the first intensity. Control to 2 strength. For example, the second intensity is a light intensity required for performing desired photoacoustic measurement. The first intensity is an appropriate intensity that complies with the safety standard of laser light. As an example, when a laser beam having a wavelength of 756 nm is used, the standard of the first intensity as the amount of energy incident on a 7 mm diameter region at a position 10 cm away is 84 μJ to reduce the light intensity to the class 3R level. Yes, to reduce the light intensity to class 1 level, it is 16 μJ.

  When a trigger control circuit (not shown) in the control unit 34 outputs a light trigger signal, the laser unit 13 turns on the flash lamp and excites the laser light source 35. For example, in the present embodiment, the laser unit 13 preferably outputs pulsed light having a pulse width of 1 to 100 nsec as laser light. The wavelength of the laser light is appropriately determined depending on the light absorption characteristics of the absorber in the subject to be measured. In general, hemoglobin in a living body absorbs light of 360 to 1000 nm, although the optical absorption characteristics differ depending on the state (oxygenated hemoglobin, deoxygenated hemoglobin, methemoglobin, etc.). Therefore, when measuring hemoglobin in a living body, it is preferable to set the thickness to about 600 to 1000 nm with relatively little absorption of other biological substances. Further, from the viewpoint of reaching deeper in the subject in the living body, the wavelength of the laser light is preferably 700 to 1000 nm, and particularly preferably in the near infrared wavelength region (700 to 850 nm). In addition to the first component light having the wavelength for photoacoustic measurement, the laser unit 13 is configured to output the second component light for contact detection having a wavelength that does not belong to the wavelength band of the first component light. May be.

  As the laser light source 35, a light source such as a semiconductor laser (LD) that generates a specific wavelength component or monochromatic light including the component, another solid-state laser, or a gas laser can be used.

<Ultrasonic unit>
The ultrasonic unit 12 of the present embodiment includes a reception circuit 21, an AD conversion unit 22, a reception memory 23, a photoacoustic image generation unit 24, a determination unit 28, a display control unit 30, and a control unit 34.

  The control part 34 controls each part of the photoacoustic measuring device 10, and is provided with a trigger control circuit in this embodiment, for example. 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, the flash lamp is turned on in the laser unit 13 and the 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 laser beam.

  The control unit 34 then 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 laser light from the laser unit 13 by this Qsw trigger signal. For example, the control unit 34 can be configured to start transmission of a Qsw trigger signal when a predetermined switch provided in the probe 11 is pressed. If comprised in this way, the position of the probe 11 when a switch is pushed can be handled as a starting point of probe scanning. Further, if the transmission of the Qsw trigger signal is terminated when the switch is pressed next time, the position of the probe 11 at that time can be handled as the end point of the probe scan.

  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 conversion unit 22 is a sampling unit, and samples the photoacoustic signal received by the reception circuit 21 and converts it into a digital signal with the reception of the sampling trigger signal from the control unit 34 as a signal. The AD converter 22 samples the received signal 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 detected by the probe 11 to the photoacoustic image generation unit 24.

  The photoacoustic image generation unit 24 reconstructs the photoacoustic signal data received from the reception memory 23 to generate a photoacoustic image. Specifically, the photoacoustic image generation unit 24 adds signal data from each ultrasonic transducer 20a with a delay time corresponding to the position of each ultrasonic transducer 20a, and generates signal data for one line. (Delayed addition method). The photoacoustic image generation unit 24 may perform reconstruction by a CBP method (Circular Back Projection) instead of the delay addition method. Alternatively, the photoacoustic image generation unit 24 may perform reconstruction using the Hough transform method or the Fourier transform method. The reconstructed data is constructed as a tomographic image through signal processing such as detection processing and logarithmic conversion processing. Since the photodetection signal is not necessary for the generation of the photoacoustic image, the portion of the photodetection signal is removed from the received signal using the time difference from light irradiation to reception, and then the signal after removal is used. It is preferable to generate a photoacoustic image based on it.

  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.

  The determination unit 28 determines whether the probe 11 and the subject M are in a contact state or a non-contact state based on the change mode of the light detection signal. Depending on the distance between the probe 11 and the subject M and the manner of contact, the content of the light detection signal detected by the transducer array 20 (its shape, such as its intensity and peak width, and the position where the signal is actually detected) changes. To do. Therefore, the determination unit 28 performs contact determination based on the change mode of the light detection signal.

  Specifically, for example, the determination unit 28 obtains the number of ultrasonic transducers 20a that respectively detect the light detection signal based on the light detection signal, and handles the change in the number as the change in the light detection signal. Thus, the determination can be made based on the size when the number is compared with the threshold number. The threshold number means the maximum number for determining that a contact state exists. For example, if the reference number that the probe 11 and the subject M are in contact (threshold number = N) is provided when the number is N or less, the determination unit 28 determines that the number is from N + 1 to N. When the number changes from N to N + 1, it is determined that the state has changed from the contact state to the non-contact state. To do. For example, if the threshold number is set to be less than the total number of ultrasonic transducers, or is set to ½ or less of the total number of ultrasonic transducers, a signal is detected from only one element. It is possible to grasp in a stepwise manner a contact state in which the measurement light does not leak more than a contact state such as being present.

  In the above description, the case where the threshold number when judging the change from the non-contact state to the contact state is the same as the threshold number when judging the change from the contact state to the non-contact state has been described. The invention is not limited to this. For example, the threshold number when determining a change from the contact state to the non-contact state can be set smaller than the threshold number when determining a change from the non-contact state to the contact state.

  FIG. 4 is a conceptual diagram showing an example of such contact determination. For example, FIG. 4 shows a state in which the transducer array 20 including 18 ultrasonic transducers 20 a is sandwiched between two light guide plates 42. In FIG. 4, it is assumed that the acoustic matching member has a light transmitting portion partially opposed to all ultrasonic transducers, for example, as shown in c or d of FIG. 3. In FIG. 4, the illustration of the acoustic matching member is omitted for easy understanding.

  First, when the probe is away from the subject, the light detection signal is detected by all the ultrasonic transducers 20a (a in FIG. 4). When the probe and the subject start to contact, the number of ultrasonic transducers 20a that cannot detect the light detection signal (the shaded portion in FIG. 4b) increases, so that the light detection signal is actually detected. The number of ultrasonic transducers that are present decreases (b in FIG. 4). This is because the reflected light does not reach the ultrasonic transducer in the region where the detection surface is covered with the subject. Further, when the number of ultrasonic transducers that are actually detecting the light detection signal reaches the threshold number (three in FIG. 4) when judging the change from the non-contact state to the contact state, When the 15th ultrasonic transducer 46a no longer detects the light detection signal, the determination unit 28 determines that the contact state has been reached, and the determination result is transmitted to the switching control unit 36 via the control unit 34. . As a result, the second intensity laser beam is emitted from the light guide plate 42 (c in FIG. 4). The shading of the light guide plate 42 represents a state in which the second intensity laser beam is emitted. Thereafter, photoacoustic measurement is performed in a state where the entire transducer array 20 is in contact (d in FIG. 4). Next, after the completion of the implementation, when the probe starts to be separated from the subject, the number of ultrasonic transducers 20a that actually detect the light detection signal increases (e in FIG. 4). Further, when the number of the elements exceeds the threshold number (9 in FIG. 4) when judging the change from the contact state to the non-contact state, that is, the ninth ultrasonic transducer 46b from the left end detects the light. When no signal is detected, the determination unit 28 determines that the non-contact state has been reached, and the determination result is transmitted to the switching control unit 36 via the control unit 34. As a result, the first intensity laser beam is emitted from the light guide plate 42 (f in FIG. 4). Therefore, when changing from the contact state to the non-contact state, the intensity of the laser beam can be lowered before the probe is completely separated from the subject (g in FIG. 4).

  In the above description, the case where the contact proceeds from the end of the transducer array 20 has been described. However, the progress of the contact may proceed at random. Also, obtaining the number of ultrasonic transducers that are actually detecting the photodetection signal means that if the total number of ultrasonic transducers is known, the number of ultrasonic transducers that cannot detect the photodetection signal Is equivalent to

  When scanning the subject manually while abutting the probe, a region where the transducer array and the subject are not in contact with each other is partially due to the effects of arm shake or subject movement. Can occur. In such a case, changing the intensity of the laser light every time such a non-contact partial region occurs may be troublesome in carrying out photoacoustic measurement. Therefore, as described above, the threshold number when judging the change from the contact state to the non-contact state is made larger than the threshold number when judging the change from the non-contact state to the contact state. Even if the non-contact partial area is slightly generated after the state is reached, the photoacoustic measurement can be continued without delay.

  In the above description, the contact determination is performed using all ultrasonic transducers, but the present invention is not limited to this. For example, in the case where the change in the number is handled as the change in the light detection signal, the determination unit only selects a specific ultrasonic transducer (acoustic wave detection element) among a plurality of ultrasonic transducers (acoustic wave detection elements). The number may be counted as a target.

  FIG. 5 is a conceptual diagram showing an example of such contact determination. For example, in FIG. 5, two ultrasonic transducers 47a and 47b at both ends of the transducer array 20 are employed as specific ultrasonic transducers. First, when the probe is away from the subject, a light detection signal is detected by both ultrasonic transducers (a in FIG. 5). When the ultrasonic transducer 47a no longer detects the light detection signal, the determination unit 28 determines that the contact state has been reached, and the determination result is transmitted to the switching control unit 36 via the control unit 34. As a result, the second intensity laser beam is emitted from the light guide plate 42 (b in FIG. 5). Thereafter, photoacoustic measurement is performed in a state where the entire transducer array 20 is in contact (c in FIG. 5). Next, after the completion of the implementation, when the ultrasonic transducer 47b detects the light detection signal, the determination unit 28 determines that the non-contact state has been reached, and the determination result is sent to the switching control unit 36 via the control unit 34. Sent. As a result, the first intensity laser beam is emitted from the light guide plate 42 (d in FIG. 5). Therefore, when changing from the contact state to the non-contact state, the intensity of the laser beam can be lowered before the probe is completely separated from the subject (e in FIG. 5).

  The specific ultrasonic transducer is appropriately selected according to, for example, the type of probe and the measurement site. For example, a group of continuous ultrasonic transducers in the vicinity of the center of the transducer array 20 may be employed, or a group of every other or every two ultrasonic transducers may be employed.

  Next, the flow of the photoacoustic measurement method and the contact determination method will be described with reference to FIG. FIG. 6 is a flowchart showing the steps of the photoacoustic measurement method of the present embodiment. First, in STEP 1, since the probe 11 and the subject M are in a non-contact state, the laser light L lowered to the first intensity is emitted. For example, the laser beam is emitted immediately after the apparatus 10 is turned on or in response to an appropriate button operation. In STEP 2, a light detection signal resulting from the emission of the laser light is detected. Next, in STEP 3, a contact determination is performed by the determination unit 28 based on the detected change state of the light detection signal, and when the contact state is determined as a result, the light intensity is increased to the second intensity. In STEP 4, the laser beam L having the second intensity is emitted. On the other hand, when the non-contact state is determined, the light intensity remains unchanged, and the laser beam L having the first intensity is emitted again after a predetermined time. When the laser beam L having the second intensity is emitted in STEP 4, a photoacoustic signal resulting from the emission of the laser beam is detected in STEP 5. This photoacoustic signal is used to generate a photoacoustic image in the photoacoustic image generation unit 24. Thereafter, in STEP 6, it is determined whether or not photoacoustic measurement has been completed. If all photoacoustic measurements have not been completed, contact determination is performed again based on the most recently detected mode of change in the photodetection signal. Done. The contact determination may be performed every time one pulse is generated, may be performed every time a plurality of pulses are generated, or may be performed every predetermined time.

  As described above, the photoacoustic measurement device and the probe of this embodiment use an acoustic matching member having a light transmission part in part, and the acoustic matching member of this embodiment has a light transmission part in part thereof. Therefore, it is possible to make a contact determination based on the manner in which the light detection signal changes due to the irradiation of the measurement light transmitted through the light transmission portion to the acoustic wave detection element. That is, according to the present invention, it is not necessary to provide other components for contact detection (for example, a contact detection sensor or a length measuring unit). As a result, in photoacoustic measurement using a probe provided with an acoustic matching member, contact determination can be performed by a simpler method.

  Since the photoacoustic measurement method and the probe contact determination method of the present embodiment use a probe having an acoustic matching member having a light transmission part in part, acoustic wave detection of measurement light transmitted through the light transmission part It is possible to make a contact determination based on how the light detection signal changes due to irradiation of the element. As a result, in the same manner as described above, in photoacoustic measurement using a probe equipped with an acoustic matching member, it is possible to perform contact determination by a simpler method.

<Design changes>
Although the case where the laser light source 35 is mainly a solid laser has been described above, the present invention is not limited to this. For example, it is possible to use a semiconductor laser as the laser light source 35. In this case, the control means for controlling the drive current value of the semiconductor laser functions as the light intensity control unit of the present invention.

  In the above description, a case has been described in which a change in the number of ultrasonic transducers that actually detect a light detection signal is handled as a change in the light detection signal, but the present invention is not limited to this. For example, the intensity of the light detection signal can be obtained, the change in the intensity can be handled as the change in the light detection signal, and the contact determination can be made based on the magnitude when the intensity and the threshold intensity are compared. This is because the intensity of the light detection signal depends on the distance between the probe and the subject, and the signal intensity increases as the distance decreases. The threshold strength means the minimum strength for determining that the contact state is present. For example, if the criterion is that the probe and the subject are in contact (threshold strength = α) when the intensity is greater than or equal to α, the determination unit 28 determines that the probe and the subject when the intensity reaches α. It is determined that the state of the sample has reached the contact state from the non-contact state, and when the intensity falls below α, it is determined that the state has changed from the contact state to the non-contact state. As the intensity of the light detection signal, the sum, maximum value or average value of the signal values of the light detection signals detected by the respective ultrasonic transducers can be employed.

“Second Embodiment”
Next, a second embodiment of the photoacoustic measurement device, probe, acoustic matching member, photoacoustic measurement method, and probe contact determination method of the present invention will be described. FIG. 7 is a conceptual diagram illustrating a configuration of the photoacoustic measurement apparatus according to the second embodiment. This embodiment is different from the first embodiment in that an ultrasonic image as a reflected acoustic wave 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, as 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. In addition, transmission and reception of ultrasonic waves may be 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 the 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 wave detected by the probe 11 is input to the AD conversion unit 22 via the receiving 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 generating 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.

  For example, the display control unit 30 causes the display unit 14 to display the photoacoustic image and the 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 effect 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 transducer 21 Reception circuit 22 Conversion part 23 Reception memory 24 Photoacoustic image generation part 28 Judgment part 29 Ultrasonic image generation part Reference Signs List 30 Display control unit 33 Transmission control circuit 34 Control unit 35 Laser light source 36 Switching control unit 37 Intensity switching unit 40 Optical fiber 41 Branch coupler 42 Light guide plate 43 Electroacoustic conversion unit 45 Housing 65 Absorber M Subject U Acoustic wave

Claims (20)

In a photoacoustic measurement apparatus that includes a probe having a light emitting portion that emits measurement light and an acoustic wave detection element, and that measures a photoacoustic signal from a subject caused by emission of the measurement light by the acoustic wave detection element,
A determination unit for determining whether the probe and the subject are in a contact state or a non-contact state;
When the determination unit determines that the probe and the subject are in a non-contact state, the intensity of the measurement light is controlled to a first intensity, and it is determined that the probe and the subject are in a contact state A light intensity controller that controls the intensity of the measurement light to a second intensity that is greater than the first intensity.
The probe has an acoustic matching member that acoustically matches the acoustic wave detection element and the subject at the contact portion of the probe,
A part of the acoustic matching member that faces the acoustic wave detection element is a light transmission part that transmits the measurement light, and another region is a light shielding part that shields the measurement light,
The light characterized in that the determination unit performs the determination based on a change state of a light detection signal caused by irradiation of the measurement light transmitted through the light transmission unit to the acoustic wave detection element. Acoustic measuring device. There are a plurality of the acoustic wave detection elements,
The photoacoustic measuring device according to claim 1, wherein the light transmission part has a slit shape extending in an arrangement direction of the plurality of acoustic wave detection elements.   The plurality of acoustic wave detection elements includes a contact detection acoustic wave detection element as the acoustic wave detection element facing the light transmission part, and a photoacoustic measurement sound for detecting a photoacoustic signal from the subject. The photoacoustic measuring device of Claim 2 which has a wave detection element.   The photoacoustic measuring device according to claim 3, wherein a plurality of the acoustic wave detecting elements for contact detection and the acoustic wave detecting elements for photoacoustic measurement are arranged in plural, and the arrangement directions thereof are parallel to each other. When the measurement light has a second component light having a wavelength different from the wavelength of the first component light used for photoacoustic measurement of the absorber in the subject,
The light transmission part transmits the second component light and blocks the first component light;
5. The photoacoustic measurement device according to claim 1, wherein the light intensity control unit controls the intensity of the measurement light by increasing or decreasing the intensity of the first component light. 6.   The determination unit obtains the number of acoustic wave detection elements that detect the light detection signal based on the light detection signal, treats the change in the number as a change in the light detection signal, and determines the number and the threshold number. The photoacoustic measuring device of any one of Claim 1 to 5 which performs the said judgment based on the magnitude when comparing with.   The photoacoustic measurement according to claim 6, wherein a threshold number when judging a change from the contact state to the non-contact state is larger than a threshold number when judging a change from the non-contact state to the contact state. apparatus.   The photoacoustic measuring device according to claim 6 or 7, wherein the determination unit is configured to count the number only for a specific acoustic wave detection element among the plurality of acoustic wave detection elements.   The determination unit obtains the intensity of the light detection signal based on the light detection signal, treats the change in the intensity as a change in the light detection signal, and based on the magnitude when the intensity and the threshold intensity are compared. The photoacoustic measurement device according to claim 1, wherein the determination is performed. In a probe having a light emitting portion for emitting measurement light and an acoustic wave detecting element,
An acoustic matching member that acoustically matches the acoustic wave detection element and the subject is provided in the contact portion of the probe,
Among the acoustic matching members, a part facing the acoustic wave detection element is a light transmission part that transmits the measurement light, and another region is a light shielding part that shields the measurement light. . There are a plurality of the acoustic wave detection elements,
The probe according to claim 10, wherein the light transmission part has a slit shape extending in an arrangement direction of the plurality of acoustic wave detection elements. When the measurement light has a second component light having a wavelength different from the wavelength of the first component light used for photoacoustic measurement of the absorber in the subject,
The probe according to claim 10 or 11, wherein the light transmission unit transmits the second component light and blocks the first component light. An acoustic matching member attached to a contact portion of a probe having a light emitting portion for emitting measurement light and an acoustic wave detecting element,
An acoustic matching member, wherein a part facing the acoustic wave detection element is a light transmission part that transmits the measurement light, and another region is a light shielding part that shields the measurement light. When the measurement light has a second component light having a wavelength different from the wavelength of the first component light used for photoacoustic measurement of the absorber in the subject,
The acoustic matching member according to claim 13, wherein the light transmissive portion transmits the second component light and blocks the first component light. A probe having a light emitting part for emitting measurement light and an acoustic wave detecting element, and further having an acoustic matching member for acoustically matching the acoustic wave detecting element and the subject at an abutting part of the probe, A part of the matching member that faces the acoustic wave detection element is a light transmission part that transmits the measurement light, and another region is a probe that is a light shielding part that blocks the measurement light,
The probe and the subject are in a contact state or in a non-contact state based on an aspect of a change in a light detection signal caused by irradiation of the measurement light transmitted through the light transmission unit to the acoustic wave detection element. Make a decision,
The intensity of the measurement light is controlled to a first intensity when it is determined that the probe and the subject are in a non-contact state, and when the probe and the subject are determined to be in a contact state, A photoacoustic measurement method, wherein the photoacoustic signal from the subject is measured by controlling to a second intensity greater than the first intensity.   When the number of acoustic wave detection elements detecting the light detection signal is obtained based on the light detection signal, the change in the number is treated as the change in the light detection signal, and the number and the threshold number are compared. The photoacoustic measurement method according to claim 15, wherein the determination is performed based on the size of the image.   The intensity of the light detection signal is obtained based on the light detection signal, the change in the intensity is treated as the change in the light detection signal, and the determination is made based on the magnitude when the intensity and the threshold intensity are compared. The photoacoustic measuring method of Claim 15. A probe having a light emitting part for emitting measurement light and an acoustic wave detecting element, and further having an acoustic matching member for acoustically matching the acoustic wave detecting element and the subject at an abutting part of the probe, A part of the matching member that faces the acoustic wave detection element is a light transmission part that transmits the measurement light, and another region is a probe that is a light shielding part that blocks the measurement light,
The probe and the subject are in a contact state or in a non-contact state based on an aspect of a change in a light detection signal caused by irradiation of the measurement light transmitted through the light transmission unit to the acoustic wave detection element. A method for determining contact of a probe, comprising determining whether or not there is a probe.   When the number of acoustic wave detection elements detecting the light detection signal is obtained based on the light detection signal, the change in the number is treated as the change in the light detection signal, and the number and the threshold number are compared. The probe contact determination method according to claim 18, wherein the determination is performed based on the size of the probe.   The intensity of the light detection signal is obtained based on the light detection signal, the change in the intensity is treated as the change in the light detection signal, and the determination is made based on the magnitude when the intensity and the threshold intensity are compared. The probe contact determination method according to claim 18.

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