JP2016036659A - Photoacoustic imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoacoustic imaging apparatus which can suppress false irradiation of light from a light-emitting device to human eyes or the like while suppressing complication of a configuration.SOLUTION: A photoacoustic imaging apparatus 100 includes: a detection generation part 24; a light source part 21 including a light-emitting diode element 21a; a light source drive part 22; and a forward voltage detection part 23 which can detect a forward voltage value of the light-emitting diode element 21a. The light source drive part 22 is configured to stop power supply for the light source part 21 on the basis of the forward voltage value detected by the forward voltage detection part 23.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photoacoustic imaging apparatus, and more particularly to a photoacoustic imaging apparatus including a detection generation unit capable of acquiring an acoustic wave.

  Conventionally, a photoacoustic imaging apparatus including a detection generation unit capable of acquiring an acoustic wave is known (for example, see Patent Document 1).

  Patent Document 1 discloses a subject information acquisition apparatus including an ultrasonic probe capable of acquiring an acoustic wave. The subject information acquisition apparatus includes a first light source that generates irradiation light for generating an acoustic wave from a subject, and a second light that generates evaluation light for generating reflected light by irradiating the subject. A light source, a second illumination optical system for irradiating the subject with light from the second light source, a light sensor for detecting reflected light reflected by the subject, and a control device. Is provided. The control device is configured to perform control so that the subject is not irradiated with the irradiation light from the first light source when the intensity signal (light amount) of the reflected light acquired by the optical sensor is outside the predetermined light amount range. Has been. Accordingly, it is possible to prevent light from being accidentally irradiated from the first light source to a part other than the subject (such as the human eye).

JP 2014-61137 A

  However, in the subject information acquisition apparatus of Patent Document 1 described above, in order to prevent light from being accidentally irradiated from the first light source to other than the subject (such as the eyes of the human body), the second light source, Since the second illumination optical system and the optical sensor are provided, there is a problem that the structure (mechanical configuration) of the subject information acquisition apparatus is complicated.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to suppress light from a light-emitting element while suppressing a complicated structure (mechanical configuration). Is to provide a photoacoustic imaging apparatus that can suppress accidentally irradiating other than the subject (such as the eyes of a human body).

  In order to achieve the above object, a photoacoustic imaging apparatus according to one aspect of the present invention detects an acoustic wave generated when light is absorbed by a detection target inside a subject, and applies to the subject. A detection generation unit capable of generating an ultrasonic wave for irradiation, a light emitting element provided in the vicinity of the detection generation unit and capable of irradiating light to the subject, and the light emitting element for generating light A light source driving unit that supplies the power of the light source to the light emitting element, and a forward voltage detecting unit that can detect a forward voltage value of the light emitting element. The light source driving unit is configured to detect the light emitting element detected by the forward voltage detecting unit. Based on the forward voltage value of the light-emitting element corresponding to the temperature, the supply of power to the light-emitting element is stopped, or the supply of power to the light-emitting element is limited.

  Here, for example, when there is an air layer between the detection generation unit and the subject (when the ultrasonic irradiation portion and the subject are not in contact with each other), the acoustic impedance of the air is detected and generated by the detection generation unit. Therefore, the ultrasonic wave generated by the detection generator repeats reflection in the vicinity of the detection generator. And the ultrasonic wave produced | generated by the detection production | generation part is absorbed in the vicinity of a detection production | generation part, and becomes heat. For this reason, when the part irradiated with the ultrasonic wave and the subject are not in contact with each other, the temperature in the vicinity of the detection generation unit increases. Further, it is known that the temperature of the light emitting element and the forward voltage value of the light emitting element have a correlation, and the forward voltage value of the light emitting element decreases when the temperature of the light emitting element (junction temperature) increases.

  The inventors of the present application have come up with the present invention by paying attention to the above phenomenon. That is, in the photoacoustic imaging apparatus according to one aspect of the present invention, as described above, the light source driving unit is based on the forward voltage value of the light emitting element corresponding to the temperature of the light emitting element detected by the forward voltage detecting unit. When the supply of power to the light-emitting element is stopped or the power supply to the light-emitting element is limited so that the ultrasonic irradiation portion and the subject are not in contact with each other Since the light emission from the light emitting element is stopped or the light emission from the light emitting element is limited, the light from the light emitting element is mistakenly irradiated to a subject other than the subject (such as the human eye). This can be suppressed. In addition, since only the forward voltage detection unit is provided, it is possible to prevent the light from the light emitting element from being accidentally irradiated to a subject other than the subject (such as the eyes of a human body), and thus the second light source and the second illumination. Unlike the case where the optical system and the optical sensor are separately provided, it is possible to suppress the complexity of the structure of the photoacoustic imaging apparatus. As a result, it is possible to prevent the light from the light emitting element from being accidentally irradiated to other than the subject (such as the eyes of the human body) while suppressing the complication of the structure (mechanical configuration).

  In the photoacoustic imaging apparatus according to the above aspect, preferably, the light source driving unit supplies the light emitting element to the light emitting element when the forward voltage value of the light emitting element corresponding to the temperature of the light emitting element is equal to or lower than the first threshold value. The supply of power is stopped, or the supply of power to the light emitting element is limited. If comprised in this way, it can be judged more easily whether the temperature of the vicinity of a detection production | generation part is abnormal by comparing a forward voltage value and a 1st threshold value. Further, when the rate of decrease in the forward voltage value is equal to or higher than the second threshold value, the supply of power to the light emitting element is stopped or the supply of power to the light emitting element is limited. In contrast, even when the forward voltage value continuously decreases in a state where the forward voltage value decrease rate is less than the second threshold value, it is possible to determine whether or not the temperature in the vicinity of the detection generation unit is abnormal. .

  In the photoacoustic imaging apparatus according to the above aspect, the light source driving unit preferably emits light when the rate of decrease in the forward voltage value of the light emitting element corresponding to the temperature of the light emitting element is equal to or higher than the second threshold value. The power supply to the element is stopped or the power supply to the light emitting element is limited. With this configuration, the second threshold value can be set to a value that takes into account the heat generated by the light irradiation from the light emitting element (a decrease rate of a constant forward voltage value). It is possible to determine whether or not the ultrasonic irradiation portion and the subject are in contact with each other. Further, unlike the case where the power supply to the light emitting element is stopped or the power supply to the light emitting element is limited when the forward voltage value is equal to or lower than the first threshold value, the forward voltage value is less than the first threshold value. Even in a state where the voltage value is equal to or higher than the first threshold value (a state where the temperature in the vicinity of the detection generation unit is low), it is possible to determine whether or not the ultrasonic irradiation portion and the subject are in contact with each other. .

  In the photoacoustic imaging apparatus according to the above aspect, preferably, the light source driving unit irradiates the subject with light from the light emitting element and detects an acoustic wave generated by a detection target inside the subject. Light is emitted based on the forward voltage value of the light emitting element corresponding to the temperature of the light emitting element detected during the period of supplying the small power while supplying less power to the light emitting element sometimes. The power supply to the element is stopped or the power supply to the light emitting element is limited. If comprised in this way, in the period which detects a forward voltage value, the heat_generation | fever accompanying light irradiation from a light emitting element can be made small. As a result, a decrease in the forward voltage value due to heat generation is suppressed, so that it can be more accurately determined whether or not the temperature in the vicinity of the detection generation unit is abnormal.

  In the photoacoustic imaging apparatus according to the above aspect, preferably, a plurality of light emitting elements are provided, and some of the plurality of light emitting elements are a plurality of light emitting elements connected in series to each other. The forward voltage detection unit is configured to be able to detect the forward voltage value of each of the plurality of light emitting element groups, and the light source driving unit is configured to detect each of the plurality of light emitting element groups. Based on the fact that any one of the forward voltage values decreases, the supply of power to the light emitting element is stopped or the supply of power to the light emitting element is limited. If comprised in this way, unlike the case where the sum total of the forward voltage of all the light emitting elements is detected, the abnormality of the temperature of the vicinity of the (local) detection production | generation part for every light emitting element group can be detected.

  In the photoacoustic imaging apparatus according to the above aspect, preferably, a plurality of light emitting elements are provided, and the light source driving unit is a light emitting element disposed closest to the detection generation unit among the plurality of light emitting elements. Based on the decrease of the forward voltage value of the element, the supply of power to the light emitting element is stopped, or the supply of power to the light emitting element is limited. If comprised in this way, since the light emitting element arrange | positioned nearest to the detection production | generation part among several light emitting elements has the small distance with a detection production | generation part, the change of the temperature of the vicinity of a detection production | generation part will be shown. It can be detected quickly.

  In the photoacoustic imaging apparatus according to the above aspect, the light emitting element is preferably formed of a light emitting diode element. With this configuration, the light emitting diode element has lower directivity than the light emitting element that emits laser light, and therefore, even when a positional shift occurs, the light irradiation range is relatively difficult to change. Thus, unlike the case of using a light emitting element that emits laser light, precise alignment (positioning) of optical members is not necessary, and an optical surface plate or a strong housing for suppressing characteristic fluctuation due to vibration of the optical system is required. The body becomes unnecessary. As a result, the optical member is not required to be precisely aligned, and an optical surface plate and a rigid housing are not required, so that the size of the photoacoustic imager and the complexity of the structure of the photoacoustic imager are suppressed. be able to.

  In the photoacoustic imaging apparatus according to the above aspect, the light emitting element is preferably constituted by a semiconductor laser element. With this configuration, the subject can be irradiated with laser light having a relatively high directivity as compared with the light-emitting diode element. Therefore, most of the light from the semiconductor laser element can be reliably irradiated onto the subject. be able to.

  In the photoacoustic imaging apparatus according to the above aspect, the light emitting element is preferably composed of an organic light emitting diode element. If comprised in this way, the light source part (probe part) containing an organic light emitting diode element can be reduced in size easily by using the organic light emitting diode element which is easy to make thin.

  According to the present invention, as described above, the light from the light emitting element is erroneously irradiated to a subject other than the subject (such as the human eye) while suppressing the complexity of the structure (mechanical configuration). Can be suppressed.

1 is a block diagram illustrating an overall configuration of a photoacoustic imaging apparatus according to a first embodiment of the present invention. It is the block diagram which showed the structure of a part of photoacoustic imaging device by 1st Embodiment of this invention. It is a figure for demonstrating the characteristic (relationship between a forward voltage value and a current value) of the light emitting diode element by 1st Embodiment of this invention. It is a figure for demonstrating the characteristic (relationship between a forward voltage value and junction temperature) of the light emitting diode element by 1st Embodiment of this invention. It is the perspective view which showed the structure of the probe part by 1st Embodiment of this invention. It is the figure which showed the arrangement position of the light emitting diode element by 1st Embodiment of this invention. It is a figure for demonstrating the temperature rise of the probe part by 1st Embodiment of this invention. It is a timing chart for demonstrating operation | movement of the photoacoustic imaging device by 1st Embodiment of this invention. It is a figure for demonstrating the detection of the acoustic wave and ultrasonic wave by 1st Embodiment of this invention. It is a timing chart for demonstrating the detection period of the forward voltage value by 1st Embodiment of this invention. It is a flowchart for demonstrating the light irradiation control processing of the photoacoustic imaging device by 1st Embodiment of this invention. It is a timing chart for demonstrating operation | movement of the photoacoustic imaging device by 2nd Embodiment of this invention. It is a flowchart for demonstrating the light irradiation control processing of the photoacoustic imaging device by 2nd Embodiment of this invention. It is a timing chart for demonstrating the detection period of the forward voltage value by 3rd Embodiment of this invention. It is a flowchart (1) for demonstrating the light irradiation control processing of the photoacoustic imaging device by 3rd Embodiment of this invention. It is a flowchart (2) for demonstrating the light irradiation control processing of the photoacoustic imaging device by 3rd Embodiment of this invention. It is the figure which showed the arrangement position of the light emitting diode element by 4th Embodiment of this invention. It is the figure which showed the arrangement position of the light emitting diode element by 5th Embodiment of this invention. It is the block diagram which showed the structure of a part of photoacoustic imaging device by the 1st modification of 1st Embodiment of this invention. It is the figure which showed the structure of the light source part by the 2nd modification of the 1st Embodiment of this invention, and a 3rd modification.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
With reference to FIGS. 1-6, the structure of the photoacoustic imaging device 100 by 1st Embodiment of this invention is demonstrated.

  The photoacoustic imaging apparatus 100 according to the first embodiment of the present invention is provided with a probe unit 20 as shown in FIG. The probe unit 20 is formed in a linear type (refer to FIG. 5), and performs light irradiation, which will be described later, and transmission of ultrasonic waves B1 and B2 by being brought into contact with the subject 10 (the body surface of the human body) by an operator. It is configured to be possible. The probe unit 20 is configured to detect the acoustic wave A1 and the ultrasonic wave B2 from the inside of the subject 10 and transmit the acoustic wave A1 and the ultrasonic wave B2 as a received signal to the main body unit 30 described later via the cable 50 of about 2 m. Yes.

  The photoacoustic imaging apparatus 100 is provided with a main body 30. The main body unit 30 is configured to process and image the received signal detected by the probe unit 20.

  Further, the photoacoustic imaging apparatus 100 is provided with an image display unit 40. The image display unit 40 is configured to acquire and display an image processed by the main body unit 30.

  As shown in FIGS. 1 and 2, the probe unit 20 is provided with a light source unit 21. The light source unit 21 is provided with a plurality (for example, 70) of light emitting diode elements 21a capable of emitting pulsed light having an infrared wavelength (for example, a wavelength of about 850 nm) that easily enters the subject 10. It has been. The plurality of light emitting diode elements 21a are connected to each other in series (see FIG. 2). Note that light having a wavelength in the infrared region is light that is invisible to the human eye, and may not be noticed even if it is irradiated directly to the eye.

Further, as shown in FIG. 2, the probe unit 20 is provided with a light source driving unit 22. The light source drive unit 22 is configured to acquire power from an external power supply unit (not shown). The light source driving unit 22 is configured to supply power to the light source unit 21 based on a light trigger signal from the control unit 31 described later. Specifically, the driving voltage V _D 1 is applied to the anode side of the light emitting diode element 21 a of the light source unit 21.

The probe unit 20 is provided with a forward voltage detection unit 23. The forward voltage detection unit 23 includes a forward voltage detection circuit 23a and a voltage detection A / D converter 23b. The forward voltage detection circuit 23a is connected to the light source driving unit 22 and the cathode side of the light emitting diode element 21a of the light source unit 21, respectively. The voltage (driving voltage V _D 1) on the light source driving unit 22 side and the light emitting diode element 21a are connected. The voltage value obtained by subtracting the voltage (voltage V _D2 ) on the cathode side of the battery can be acquired. That is, the forward voltage detection circuit 23 a is configured to be able to acquire the total value of the forward voltage values (forward voltage value V _F ) of the plurality of light emitting diode elements 21 a included in the light source unit 21. The forward voltage detection circuit 23 a is configured to acquire a voltage value based on a sampling trigger signal synchronized with the light trigger signal from the control unit 31. In the following description in the present specification, “the total value of the forward voltage values of the plurality of light emitting diode elements 21a included in the light source unit 21” is simply referred to as “forward voltage value V _F ”.

Further, the voltage detecting A / D converter 23b, and obtains a sampling trigger signal from the control unit 31, based on the obtained sampling trigger signal, the forward voltage V _F of the analog format forward voltage detecting circuit 23a obtains It is configured to convert the forward voltage value V _F of the digital format. The voltage detection A / D converter 23 b is configured to transmit the converted digital format forward voltage value V _F to the control unit 31.

Further, as shown in FIG. 3, the light emitting diode element 21a, when a constant temperature (junction temperature), the current value and the forward voltage value V _F flowing through the light emitting diode element 21a, has a correlation. For example, in the case of the forward voltage value V _F0 1, the current value is 1 A, and in the case of the forward voltage value V _F02 , the current value is 10 A. Then, as shown in FIG. 4, the light emitting diode element 21a is, when the value of the current flowing through the light emitting diode element 21a is constant, the forward voltage V _F and junction temperature, has a relationship of a linear function. That is, the light emitting diode element 21a is the junction temperature rises, has a characteristic that the forward voltage value V _F decreases. For example, in the case of the forward voltage value V _F1 1, the junction temperature is 60 ° C., and in the case of the forward voltage value V _F1 2, the junction temperature is 20 ° C.

Therefore, by considering the characteristics of the light emitting diode elements 21a, photoacoustic imaging apparatus 100 according to the first embodiment, the first Works the forward voltage V _F corresponding to the temperature of the light emitting diode element 21a is described below When the threshold value Vt1 or less, the supply of power to the light source unit 21 can be stopped.

  Further, as shown in FIG. 5, the light emitting diode element 21a is configured to irradiate light toward the arrow Y1 direction side. Then, the pulsed light emitted from the probe unit 20 to the subject 10 is absorbed by a detection target (for example, hemoglobin or the like) in the subject 10 as described later (see FIG. 9). Then, the detection object expands and contracts (returns from the expanded size to the original size) in accordance with the irradiation intensity (absorption amount) of the pulsed light, so that the detection target object (the subject 10) performs acoustics. A wave A1 (see FIG. 9B) is generated. In this specification, for convenience of explanation, an ultrasonic wave generated when the detection target in the subject 10 absorbs light is referred to as “acoustic wave A1” and is generated by the detection generation unit 24 and The ultrasonic wave reflected by the specimen 10 is distinguished and described as “ultrasonic wave B2” described later.

  The probe unit 20 is provided with a detection generation unit 24. The detection generation unit 24 includes an acoustic lens 24a, an acoustic matching layer 24b, an ultrasonic transducer substrate 24c, and a backing material 24d that are bonded to each other, and detects an acoustic wave A1 from the subject 10. In addition, an ultrasonic wave B1 for irradiating the subject 10 can be generated.

  As shown in FIG. 6, the ultrasonic transducer substrate 24c has a plurality of (eg, 128) ultrasonic waves linearly arranged in the X direction at a predetermined interval (eg, 0.3 mm interval). A vibrator 24e is provided. The light source unit 21 is disposed on the arrow Z2 direction side of the ultrasonic transducer substrate 24c. In FIG. 6, the number of ultrasonic transducers 24 e is described as being smaller than 128 for ease of explanation. Further, the number of the light emitting diode elements 21a is also described as a number smaller than 70.

  The ultrasonic transducer 24e is composed of a piezoelectric element (for example, lead zirconate titanate (PZT)). And the ultrasonic transducer | vibrator 24e is comprised so that it may vibrate and produce a voltage (reception signal), when above-mentioned acoustic wave A1 is acquired. And the ultrasonic transducer | vibrator 24e is comprised so that the acquired received signal may be transmitted to the receiving circuit 32 mentioned later.

  Further, the ultrasonic transducer 24e is configured to be able to generate an ultrasonic wave B1 by vibrating at a frequency corresponding to a transducer drive signal from the control unit 31.

  The acoustic matching layer 24b is composed of a plurality of layers having different acoustic impedances, and is configured to match the acoustic impedance between the ultrasonic transducer 24e and the subject 10. For example, the acoustic matching layer 24b has an acoustic impedance that gradually decreases from the ultrasonic transducer 24e toward the subject 10, and at the portion joined to the acoustic lens 24a (the subject 10 side), the acoustic impedance of the subject 10 is increased. It is comprised so that it may become a value substantially equal to an impedance. Note that the acoustic matching layer 24b may be configured by an acoustic impedance layer (one layer) having a substantially intermediate value between the ultrasonic transducer 24e and the subject 10.

  The acoustic lens 24a is configured to irradiate the subject 10 while focusing the ultrasonic wave B1 from the acoustic matching layer 24b (ultrasonic transducer 24e).

  The backing material 24d is arranged behind the ultrasonic transducer 24e (arrow Y2 direction side), and is configured to suppress propagation of the ultrasonic wave B1, the ultrasonic wave B2, and the acoustic wave A1 backward. ing.

  Then, as shown in FIG. 7A, the ultrasonic wave B1 generated by the ultrasonic transducer 24e is reflected by a substance (detection target) having a large acoustic impedance in the subject 10. In addition, the ultrasonic wave B2 (the reflected wave of the ultrasonic wave B1) is acquired by the ultrasonic vibrator 24e, and the ultrasonic vibrator 24e is configured to vibrate by the ultrasonic wave B2.

  And the detection production | generation part 24 is comprised so that a received signal may be transmitted to the receiving circuit 32 similarly to the case where it vibrates with the acoustic wave A1, when it vibrates with the ultrasonic wave B2. The photoacoustic imaging apparatus 100 irradiates the subject 10 with pulsed light by the light source unit 21 to generate the acoustic wave A1, and acquires the acoustic wave A1 by the detection generation unit 24 (light irradiation period τ3). (See FIG. 10) and the detection generation unit 24 irradiate the subject 10 with the ultrasonic wave B1 and the period during which the ultrasonic generation B2 is acquired by the detection generation unit 24 are configured so as not to overlap. A1 and ultrasonic wave B2 can be distinguished.

  As shown in FIG. 1, the main body 30 is provided with a control unit 31. The control unit 31 includes a CPU (Central Processing Unit) and the like, and is configured to control the entire photoacoustic imaging apparatus 100 by transmitting a control signal to each unit. For example, the control unit 31 is configured to transmit a light trigger signal to the light source driving unit 22. As a result, the light source driving unit 22 supplies power based on the light trigger signal to the light source unit 21 so that the light source unit 21 emits pulsed light (for example, a pulse width of about 150 nm and a repetition frequency of 1 kHz). It is configured to be.

  The main body 30 is provided with a receiving circuit 32. The reception circuit 32 includes a coupling capacitor and the like, and is configured to acquire a reception signal (AC component) from the detection generation unit 24. In addition, the reception circuit 32 is configured to acquire a reception signal during a period (acoustic wave transmission / reception period τ1) in which a reception acceptance signal is acquired by the control unit 31. The receiving circuit 32 is configured to transmit the acquired received signal to the image signal A / D converter 33.

  Further, the main body 30 is provided with an image signal A / D converter 33. The image signal A / D converter 33 is configured to convert the reception signal (analog signal) acquired from the reception circuit 32 into a digital signal corresponding to the sampling trigger signal acquired from the control unit 31. Has been. The image signal A / D converter 33 is connected to the reception memory 34, and the image signal A / D converter 33 transmits the reception signal converted into a digital signal to the reception memory 34. It is configured.

  In addition, the main body 30 is provided with a reception memory 34. The reception memory 34 is configured to temporarily store a reception signal converted into a digital signal. The reception memory 34 is connected to the data processing unit 35 and is configured to transmit the stored acoustic wave signal to the data processing unit 35.

  The main body 30 is provided with a data processing unit 35. The data processing unit 35 is connected to the acoustic wave image reconstruction unit 51, and the data of the acoustic wave A <b> 1 is configured to be transmitted to the acoustic wave image reconstruction unit 51. The data processing unit 35 is connected to the ultrasonic image reconstruction unit 54, and is configured to transmit ultrasonic B2 data to the ultrasonic image reconstruction unit 54.

  The main body unit 30 is provided with an acoustic wave image reconstruction unit 51. The acoustic wave image reconstruction unit 51 is configured to perform processing for reconstructing the acquired data of the acoustic wave A1 as an image.

The acoustic wave image reconstruction unit 51, in reconstructing the image, to obtain the temperature correction information corresponding to the forward voltage value V _F of forward voltage detection unit 23 obtains from the control unit 31, corrects the image Is configured to do. For example, the light emitting diode element 21a has a property that the wavelength (center wavelength) of the light emitted from the light emitting diode element 21a changes according to the temperature inside the probe unit 20. In addition, the light absorption coefficient of the detection target of the subject 10 has a different value depending on the wavelength. Therefore, the acoustic wave image reconstruction unit 51 can perform imaging more accurately by correcting in consideration of a change in the wavelength of light emitted from the light emitting diode element 21a due to a temperature change.

  The acoustic wave image reconstruction unit 51 is connected to the detection / logarithmic converter 52, and is configured to transmit the data of the acoustic wave A1 reconstructed as an image to the detection / logarithmic converter 52.

  Further, the main body 30 is provided with a detection / logarithmic converter 52. The detection / logarithmic converter 52 is configured to perform waveform processing of data reconstructed as an image. The detection / logarithmic converter 52 is connected to the acoustic wave image construction unit 53 and is configured to transmit the waveform-processed data.

  The main body unit 30 is provided with an acoustic wave image construction unit 53. The acoustic wave image constructing unit 53 is configured to perform processing for constructing a tomographic image in the subject 10 based on the waveform-processed data. The acoustic wave image construction unit 53 is connected to the image composition unit 57 and configured to transmit a tomographic image based on the acoustic wave A1.

  The main body unit 30 is provided with an ultrasonic image reconstruction unit 54, a detection / logarithmic converter 55, an ultrasonic image construction unit 56, and an image composition unit 57. The ultrasonic image reconstruction unit 54 is configured to perform processing for reconstructing ultrasonic B2 data acquired from the data processing unit 35 as an image. The ultrasound image reconstruction unit 54 is configured to transmit a tomographic image based on the ultrasound B2 to the image composition unit 57 via the detection / logarithmic converter 55 and the ultrasound image construction unit 56. ing.

  The main body unit 30 is provided with an image composition unit 57. The image synthesis unit 57 is configured to perform a process of synthesizing the tomographic image based on the acoustic wave A1 and the tomographic image based on the ultrasonic wave B2, and output the synthesized image to the image display unit 40.

  The main body 30 is provided with an operation unit 58. The operation unit 58 is configured to receive an operation from the operator. For example, the operation unit 58 acquires operation information such as turning on / off the power of the photoacoustic imaging apparatus 100 and starting and ending observation (irradiation of light and ultrasonic waves B1), and uses the acquired operation information as a control unit. It is comprised so that it may transmit to 31.

  And the image display part 40 is comprised by the liquid crystal panel etc., and is comprised so that the image acquired from the main-body part 30 may be displayed.

  Next, the principle of temperature rise inside the probe unit 20 (near the detection generation unit 24) in the first photoacoustic imaging apparatus 100 will be described with reference to FIG.

  As shown in FIG. 7A, when the probe unit 20 and the subject 10 are in contact, the difference between the acoustic impedance of the surface of the probe unit 20 and the acoustic impedance of the subject 10 is small. The ultrasonic wave B <b> 1 irradiated from the unit 20 to the subject 10 enters the subject 10. Then, the ultrasonic wave B <b> 2 reflected from the detection target inside the subject 10 enters the probe unit 20. Note that the intensity of the ultrasonic wave B2 is attenuated when propagating through the subject 10, and thus is smaller than the intensity of the ultrasonic wave B1.

  On the other hand, as shown in FIG. 7B, when the probe unit 20 and the subject 10 are not in contact (when there is an air layer between the probe unit 20 and the subject 10), the probe unit 20 Since the difference between the acoustic impedance of the surface and the acoustic impedance of the air layer is large, the ultrasonic wave B1 irradiated from the probe unit 20 is reflected at the boundary between the probe unit 20 and the air layer. Then, the ultrasonic wave B1 reflected at the boundary between the probe unit 20 and the air layer is absorbed by each part of the probe unit 20 while being repeatedly reflected inside the probe unit 20, thereby generating heat. Thereby, when the probe unit 20 and the subject 10 are not in contact with each other, the temperature inside the probe unit 20 (particularly, in the vicinity of the detection generation unit 24 and the light source unit 21) increases.

  Next, the operation of the light source driving unit 22 in the photoacoustic imaging apparatus 100 according to the first embodiment will be described with reference to FIG.

In the first embodiment, when the forward voltage value V _F corresponding to the temperature of the light emitting diode element 21a by the light source drive unit 22 is equal to or less than the first threshold value Vt1, the power to the light emitting diode element 21a Supply is stopped. It should be noted that the probe unit 20 and the subject 10 are in contact at the time point t1 to the time point t2, and the probe unit 20 and the subject 10 are not in contact at the time point after the time point t2. An explanation will be given.

From time t1 to time t4, the ultrasonic wave B1 is emitted from the detection generation unit 24 and the subject 10 is irradiated with light from the light source unit 21. Therefore, the forward voltage value V _F gradually decreases as the temperature of the light source unit 21 starts to rise from the time t2 when the probe unit 20 and the subject 10 are not in contact with each other. Then, at time t4, the forward voltage V _F becomes the first threshold value Vt1 following light irradiation stop from (the light source unit 21 which supply is stopped of power from the light source driving unit 22 to the light source unit 21 )

Specifically, since the probe unit 20 and the subject 10 are in contact from time t1 to time t2, the temperature of the light emitting diode element 21a is constant. Thus, at the time point t1~ time t2, the forward voltage _{V F,} the voltage value V1.

Then, at time t2, since a state where the probe portion 20 and the object 10 is not in contact, the temperature of the inside of the probe unit 20 is increased, at time t3, the forward voltage V _F, the voltage value V2 It becomes. In this case, the voltage value V2 is higher than the first threshold value Vt1, and the supply of power to the light source unit 21 by the light source driving unit 22 is continued.

Then, at time t4, the forward voltage V _F, becomes the voltage value V3, the voltage value V3 is equal to or less than the first threshold value Vt1, the power supply to the light source unit 21 by the light source drive unit 22 is stopped The

  Next, as shown in FIG. 9, the length of the period required for the detection generator 24 to transmit the ultrasonic wave B1 and receive the ultrasonic wave B2 will be described. The ultrasonic transmission / reception period τ1 is set in consideration of the principle described below.

  As shown in FIG. 9A, description will be made assuming that there is a detection target (for example, a blood vessel, a nerve tissue, etc.) at the position of the measurement depth L inside the subject 10. The ultrasonic wave B <b> 1 irradiated from the detection generation unit 24 propagates from the surface of the subject 10 toward the inside at the sound speed S and reaches the detection target with a propagation time ta (= L / S). Since the detection object has a larger acoustic impedance than the surrounding biological tissue, the ultrasonic wave B1 is reflected by the detection object. The reflected ultrasonic wave B2 propagates through the subject 10 at the speed of sound S and reaches the detection generator 24 with the same propagation time ta. Thus, the reception period tr1 from the start of irradiation of the ultrasonic wave B1 to the completion of reception of the ultrasonic wave B2 reflected at the measurement depth L is approximately twice as long as the propagation period ta (tr1 = ta × 2). . Accordingly, for example, the reception period tr1 is about 40 μs when the observation depth L to be observed is 30 mm. Therefore, the detection target within 30 mm is detected by setting the ultrasonic transmission / reception period τ1 to 40 μs. It becomes possible.

  On the other hand, as shown in FIG. 9B, the description will be made on the assumption that there is a detection target (for example, an injection needle (light absorber)) at the position of the measurement depth L inside the subject 10. When light is emitted from the light source unit 21 toward the inside from the surface of the subject 10, the light propagates through the subject 10 at the speed of light C and reaches the detection target with a propagation time tb1 (= L / C). . When the detection object receives light, the internal molecule absorbs the energy of the light and releases heat. The detection object expands in volume by this emitted heat and generates an acoustic wave A1 (photoacoustic effect). The acoustic wave A1 propagates through the subject 10 at the speed of sound S and reaches the detection generation unit 24 at the propagation time tb2 (= L / S). Therefore, the reception period tr2 from the start of light irradiation until the reception of the acoustic wave A1 returning from the measurement depth L is completed is the sum of the propagation periods tb1 and tb2 (tr2 = tb1 + tb2). However, since the speed of light C is much higher than the speed of sound S, the propagation time tb1 for the light to reach the detection target from the light source unit 21 can be substantially ignored. As a result, tr2≈tb2. Therefore, the length of the acoustic wave transmission / reception period can be set by a period that is approximately half the ultrasonic transmission / reception period τ1.

Next, the detection period τ2 of the forward voltage value V _F in the first photoacoustic imaging apparatus 100 will be described with reference to FIG.

  As shown in FIG. 10, after the ultrasonic transmission / reception period τ1, a light irradiation period τ3 and a forward voltage value detection period τ2 are started. In addition, the light irradiation period τ3 and the forward voltage value detection period τ2 are started substantially simultaneously, and the forward voltage value detection period τ2 ends at a time later than the time when the light irradiation period τ3 ends.

  Specifically, the voltage level of the reception acceptance signal is set to H at time t11. That is, transmission of the ultrasonic wave B1 and reception of the ultrasonic wave B2 are started from the detection generation unit 24. When the probe unit 20 and the subject 10 are not in contact with each other, the temperature inside the probe unit 20 rises. At time t12, the voltage level of the reception acceptance signal is set to L.

At time t13, the voltage levels of the optical trigger signal and the forward voltage value data signal are set to H. That is, the power from the light source driver 22 to the light source unit 21 is supplied, the forward voltage V _F is obtained by the forward voltage detection unit 23.

  At time t14, the voltage level of the optical trigger signal is set to L. At time t15, the voltage level of the forward voltage value data signal is set to L. From time t16 to time t17, driving similar to that at time t11 to time t15 is performed. Further, the time point t11 and the time point t16 have a repetition period τ4, and the same drive as the time point t11 to the time point t15 is performed every fixed repetition period τ4.

  Next, a light irradiation control process flow of the photoacoustic imaging apparatus 100 according to the first embodiment will be described with reference to FIG. Processing in the photoacoustic imaging apparatus 100 is performed by the control unit 31.

  First, in step S1, it is determined whether or not “power” is turned on. That is, it is determined whether or not a signal for turning on the “power supply” has been received. This determination is repeated until “power” is turned on. If “power” is turned on, the process proceeds to step S2.

  In step S2, the probe ID is acquired. That is, a probe ID is acquired from a probe ID storage unit (not shown) provided inside the probe section 20. Thereafter, the process proceeds to step S3.

  In step S3, the first threshold value Vt1 is set. Further, the first threshold value Vt1 is set to a set value (set value determined for each probe unit 20) based on the probe ID acquired in step S2. Thereafter, the process proceeds to step S4.

  In step S4, it is determined whether or not “observation” has started. That is, it is determined whether or not a signal for starting “observation” has been received. This determination is repeated until “observation” is started. If “observation” is started, the process proceeds to step S5.

  In step S5, the ultrasonic wave B1 is transmitted. Then, it progresses to step S6.

  In step S <b> 6, reception of the ultrasonic wave B <b> 2, image processing, and image display on the image display unit 40 are performed. Then, it progresses to step S7.

  In step S7, light irradiation is performed. That is, power is supplied from the light source driving unit 22 to the light source unit 21. Thereafter, the process proceeds to step S8.

Then, in step S8, the detection of the forward voltage _{V F} is performed. Thereafter, the process proceeds to step S9.

Then, in step S9, the forward voltage V _F is whether the first threshold value Vt1 less is determined. That is, the forward voltage V _F detected in step S8, whether the first threshold value Vt1 less is determined. If the forward voltage _{V F} is equal to or less than the first threshold value Vt1, the process proceeds to step S12, the forward voltage _{V F} is not equal to or less than the first threshold value Vt1 (than the first threshold value Vt1 If so, the process proceeds to step S10.

  In step S10, the acoustic wave A1 is received, image processing, and an image is displayed on the image display unit 40. Then, it progresses to step S11.

  In step S11, it is determined whether or not “observation” has been completed. That is, it is determined whether or not a signal for ending “observation” has been received. When “observation” is ended, the light irradiation control process of the photoacoustic imaging apparatus 100 according to the first embodiment is ended. When “observation” is not ended, the process returns to step S5.

Further, in step S12 the process proceeds when the forward voltage V _F in step S9 is equal to or less than the first threshold value Vt1, the temperature inside the probe unit 20 determines that there is an abnormality, according to the first embodiment The light irradiation control process of the photoacoustic imaging apparatus 100 is ended. That is, in this case, irradiation of light from the light source unit 21 and generation of the ultrasonic wave B1 by the detection generation unit 24 are stopped.

  In the first embodiment, the following effects can be obtained.

In the first embodiment, as described above, the light source driving unit 22, on the basis of the forward voltage value V _F of the light emitting diode element 21a corresponding to the temperature of the light emitting diode elements 21a detected by the forward voltage detection unit 23, the light emitting By configuring so that the supply of power to the diode element 21a is stopped, the light from the light source unit 21 can be obtained when the portion (probe unit 20) that radiates the ultrasonic wave B1 and the subject 10 are not in contact with each other. Therefore, it is possible to prevent light from the light source unit 21 from being accidentally irradiated to other than the subject 10 (such as human eyes). Further, by providing only the forward voltage detection unit 23, it is possible to prevent the light from the light source unit 21 from being accidentally irradiated to other than the subject 10 (such as the eyes of the human body). Unlike the case where the illumination optical system 2 and the optical sensor are separately provided, the structure of the photoacoustic imaging apparatus 100 can be prevented from becoming complicated. As a result, it is possible to prevent the light from the light source unit 21 from being accidentally irradiated to a part other than the subject 10 (such as the eyes of a human body) while suppressing the complexity of the structure (mechanical configuration). .

In the first embodiment, as described above, when the light source driving section 22, the forward voltage V _F of the light emitting diode element 21a corresponding to the temperature of the light emitting diode element 21a is equal to or less than the first threshold value Vt1 In addition, the power supply to the light source unit 21 is stopped. Thus, by comparing the forward voltage V _F and the first threshold value Vt1, more easily, the temperature in the vicinity of the detector generator 24 (internal probe unit 20) determines whether abnormal or not be able to. Further, when the reduction rate of the forward voltage V _F is equal to or greater than a predetermined threshold value, different from the case configured to stop supplying power to the light source unit 21, decrease rate of the forward voltage V _F is given in a state below the threshold, it can be continuously reduced forward voltage V _F, the temperature in the vicinity of the detector generating unit 24 determines whether abnormal or not.

  In the first embodiment, as described above, the light emitting diode element 21 a is provided in the light source unit 21. Thereby, since the light emitting diode element 21a has lower directivity than the light emitting element that emits laser light, the light irradiation range is relatively unlikely to change even when a positional shift occurs. Unlike the case where a light emitting element that emits laser light is used, precise alignment (positioning) of optical members is not required, and an optical surface plate or a strong housing for suppressing characteristic fluctuations due to vibration of the optical system Is no longer necessary. As a result, the photoacoustic imaging apparatus 100 is increased in size and the structure of the photoacoustic imaging apparatus 100 is complicated because precise alignment of the optical members is unnecessary and an optical surface plate and a strong housing are unnecessary. Can be suppressed.

(Second Embodiment)
Next, the configuration of the photoacoustic imaging apparatus 200 according to the second embodiment will be described with reference to FIG. In the second embodiment, the photoacoustic image according to the first embodiment is configured to stop the supply of power to the light source unit when the forward voltage value of the light-emitting diode element is equal to or less than the first threshold value. Unlike the manufacturing apparatus 100, when the rate of decrease of the forward voltage value of the light-emitting diode element is equal to or higher than the second threshold value, the supply of power to the light source unit is stopped.

  As shown in FIG. 1, the photoacoustic imaging apparatus 200 according to the second embodiment is provided with a probe unit 220 and a main body unit 230. The probe unit 220 is provided with a light source driving unit 222. The main body unit 230 is provided with a control unit 231. Other configurations of the photoacoustic imaging apparatus 200 according to the second embodiment are the same as those of the photoacoustic imaging apparatus 100 according to the first embodiment.

  Next, the operation of the light source driving unit 222 in the photoacoustic imaging apparatus 200 according to the second embodiment will be described with reference to FIG.

In the second embodiment, when the reduction rate of the forward voltage V _F of the light emitting diode element 21a corresponding to the temperature of the light emitting diode element 21a is a second threshold value Rt1 or by the light source driving unit 222, The supply of power to the light source unit 21 is stopped. It should be noted that at time t21 to time t22, the probe unit 220 and the subject 10 are in contact with each other, and at a time point after the time t22, the probe unit 220 and the subject 10 are not in contact with each other. An explanation will be given.

From time t21 to time t25, the object 10 is irradiated with the ultrasonic wave B1 from the detection generation unit 24 and the light source unit 21. Therefore, the temperature of the light source unit 21 starts to rise from time t22 when the probe unit 220 and the subject 10 are not in contact with each other. As a result, the forward voltage value V _F gradually decreases. Then, at time t25, decrease rate of the forward voltage _{V F ((V14-V13)} / τ5) becomes a value larger than the second threshold value Rt1, supply of electric power from the light source driver 222 to the light source unit 21 Is stopped (irradiation of light from the light source unit 21 is stopped).

Specifically, from time t21 to time t22, since the probe unit 220 and the subject 10 are in contact with each other, the temperature of the light emitting diode element 21a is constant. Thus, at the time point t21~ time t22, the forward voltage _{V F,} the voltage value V11.

Then, at time t22, since the state in which the probe unit 220 and the object 10 is not in contact, the temperature of the interior of the probe 220 is raised, at the time t23, the forward voltage _{V F,} the voltage value V12 next, at time t24, the forward voltage _{V F} is a voltage value V13. In this case, reduction rate of the forward voltage _{V F (V12-V11) /} τ5 and (V13-V12) / τ5 is smaller than the second threshold value Rt1, to the light source unit 21 by the light source driving part 222 The supply of power is continued.

Then, at time t25, decrease rate of the forward voltage _{V F} is, (V14-V13) / τ5 next, since the second threshold value Rt1 above, the power supply to the light source unit 21 by the light source driving unit 22 Is stopped.

  Next, a light irradiation control process flow of the photoacoustic imaging apparatus 200 according to the second embodiment will be described with reference to FIG. Processing in the photoacoustic imaging apparatus 200 is performed by the control unit 231. Further, the steps denoted by the same reference numerals as the light irradiation control process of the photoacoustic imaging apparatus 100 according to the first embodiment are the same as the light irradiation control process (see FIG. 11) according to the first embodiment. Shall.

  In step S101, a second threshold value Rt1 is set. The second threshold value Rt1 is set to a set value determined for each probe unit 220. Thereafter, the process proceeds to step S4.

Then, in step S102, whether or not reduction rate of the forward voltage _{V F} is a second threshold value Rt1 more is determined. If reduction rate of the forward voltage V _F is equal to or greater than the second threshold value Rt1, the process proceeds to step S103, if reduction ratio of the forward voltage V _F is not a second threshold value Rt1 above, step Proceed to S10.

  In step S103, the temperature inside the probe unit 220 (temperature change rate) is determined to be abnormal, and the light irradiation control process of the photoacoustic imaging apparatus 200 according to the second embodiment is terminated. That is, in this case, irradiation of light from the light source unit 21 and generation of the ultrasonic wave B1 by the detection generation unit 24 are stopped.

  In the second embodiment, the following effects can be obtained.

In the second embodiment, as described above, the light source driving unit 222, reduction rate of the forward voltage V _F of the light emitting diode element 21a corresponding to the temperature of the light emitting diode element 21a is a second threshold value Rt1 more In this case, the power supply to the light source unit 21 is stopped. Thus, the second threshold value Rt1, can be set to a value based on the (sometimes decrease rates over the forward voltage V _F) heat generated by the irradiation of light from the light emitting diode element, More accurately, it can be determined whether or not the portion (probe unit 220) that irradiates the ultrasonic wave B1 and the subject 10 are in contact with each other. Further, unlike the first embodiment, the forward voltage V _F is even first threshold Vt1 or more states (state temperature of the probe portion 220 is low), in contact with the probe 220 and the object 10 with one another It can be determined whether or not. Other effects of the photoacoustic imaging apparatus 200 according to the second embodiment are the same as those of the photoacoustic imaging apparatus 100 according to the first embodiment.

(Third embodiment)
Next, the configuration of the photoacoustic imaging apparatus 300 according to the third embodiment will be described with reference to FIG. In 3rd Embodiment, the photoacoustic image by 1st Embodiment comprised so that the forward voltage value of the light emitting diode element at the time of the detection operation which detects the acoustic wave which generate | occur | produces with the detection target inside a subject could be acquired. Unlike the conversion apparatus 100, the forward voltage value of the light emitting diode element detected during a period during which a small amount of power is supplied is obtained.

  As shown in FIG. 1, the photoacoustic imaging apparatus 300 according to the third embodiment is provided with a probe unit 320 and a main body unit 330. In addition, the probe unit 320 is provided with a light source driving unit 322. The main body 330 is provided with a control unit 331.

  Here, in the third embodiment, the light source driving unit 322 detects the acoustic wave A1 generated by the detection target inside the subject 10 by irradiating the subject 10 with light from the light emitting diode element 21a. Power (for example, current value 1 mA) smaller than power (for example, current value 15A) supplied to the light emitting diode element 21a at the time (light irradiation period τ11) is configured to be supplied to the light source unit 21.

  Specifically, the light source driver 322 includes a constant current diode (CRD) and the like, and has a small current value such that the light emitting diode element 21a does not generate heat (or the generation of heat can be ignored). Electric power (for example, a constant current having a current value flowing through the light emitting diode element 21 a of 1 mA) can be supplied to the light source unit 21. The light source driving unit 322 is configured to supply small power (small current) to the light source unit 21 based on a small current trigger signal from the control unit 331. In the following description, supplying small power having a current value that does not generate heat from the light emitting diode element 21a to the light source unit 21 is simply referred to as “supplying small power (small current)”.

Furthermore, the characteristics of the light emitting diode element 21a (see FIGS. 3 and 4), regardless of the current value, by obtaining a forward voltage V _F of the light emitting diode elements 21a, estimate the temperature of the light emitting diode element 21a It is possible.

Also, low power (low current) period for supplying (small current supply period Tau12) and the forward voltage V _F to get the period (forward voltage value detection period Tau13), for example, is set to approximately 240Myuesu.

  The other configuration of the photoacoustic imaging apparatus 300 according to the third embodiment is the same as that of the photoacoustic imaging apparatus 100 according to the first embodiment.

Next, the detection period τ12 of the forward voltage value V _F in the third photoacoustic imaging apparatus 300 will be described with reference to FIG.

Here, in the third embodiment, the forward voltage value V of the light emitting diode element 21a corresponding to the temperature of the light emitting diode element 21a detected during the period during which small electric power (small current) is supplied (small current supply period τ13). Based on _F , the supply of power to the light source unit 21 is stopped.

As shown in FIG. 14, the forward voltage value detection period τ12 and the small current supply period τ13 are started and ended at substantially the same time. That is, the forward voltage V _F is obtained by the forward voltage detection unit 23 to the low current supply period Tau13. Meanwhile, unlike the photoacoustic imaging apparatus 100 according to the first embodiment, the light irradiation time τ11 is forward voltage V _F is not acquired.

Further, the forward voltage value detection period τ12, the small current supply period τ13, and the ultrasonic transmission / reception period τ14 are started substantially simultaneously, and the forward voltage value detection period τ12 and the small current supply period τ13 end the ultrasonic transmission / reception period τ14. Is finished. That is, the forward voltage value detection period τ12 includes an ultrasonic transmission / reception period τ14. Thus, it is possible to obtain the rate of change of temperature of the light emitting diode element 21a (reduction rate of the forward voltage V _F) while transmission and reception of ultrasound B2 of the ultrasonic B1.

In addition, the light irradiation period τ11 starts after the time point (time point t33) when the forward voltage value detection period τ12 ends. Incidentally, in the forward voltage value detection period Tau12, when reduction rate of the forward voltage V _F is equal to or greater than the third threshold value Rt2 are not light irradiation period τ11 begins, the irradiation of the light from the light source unit 21 Is not done. The third threshold value Rt2 is set similarly to the second threshold value Rt1 according to the second embodiment.

Specifically, at time t31, the voltage levels of the small current trigger signal, the reception acceptance signal, and the forward voltage value data signal are set to H. Note that the sampling trigger signal is transmitted a plurality of times from the control unit 331 to the forward voltage value detection unit 323 in the state where the voltage level of the forward voltage value data signal is H (in the forward voltage value detection period τ12. That is, forward voltage value detection. several times during the period Tau12, together with the acquisition of the forward voltage V _F is performed, the calculation of the reduction ratio of the forward voltage V _F is performed. Then, at time t32, the voltage level of the received reception signal is in the L.

  At time t33, the voltage levels of the small current trigger signal and the forward voltage value data signal are set to L. Further, the voltage level of the optical trigger signal is set to H. Thereafter, at time t34, the voltage level of the optical trigger signal is set to L. In addition, the time point t31 and the time point t35 have a repetition period τ15, and the same drive as the time point t31 to the time point t34 is performed every fixed repetition period τ15.

  Next, a light irradiation control process flow of the photoacoustic imaging apparatus 300 according to the third embodiment will be described with reference to FIG. Processing in the photoacoustic imaging apparatus 300 is performed by the control unit 331. Further, the steps denoted by the same reference numerals as the light irradiation control process of the photoacoustic imaging apparatus 100 according to the first embodiment are the same as the light irradiation control process (see FIG. 11) according to the first embodiment. Shall.

  In step S201, the third threshold value Rt2 is set. Further, the third threshold value Rt2 is set to a setting value (setting value determined for each probe unit 320) based on the probe ID acquired in step S2. Thereafter, the process proceeds to step S4.

  In step S202, supply of small electric power (small current) to the light source unit 21 is started. Thereafter, the process proceeds to step S203.

Then, in step S203, the detection of the forward voltage _{V F} is performed. That is, the detection of the forward voltage V _F immediately before the ultrasonic B1 is transmitted from the detector generator 24 is performed. Thereafter, the process proceeds to step S204.

In step S204, the third threshold value Rt2 is corrected. That is, the correction of the third threshold value Rt2 based on the forward voltage _{V F} acquired in step S203 is performed. For example, if a relatively high forward voltage V _F (when the temperature of the light emitting diode element 21a is relatively low), upon contact with the object 10, since the constant temperature rise is expected, constant temperature rise Is corrected so as to change to the third threshold value Rt2 in which is considered. Thereafter, the process proceeds to step S205.

  In step S205, the ultrasonic wave B1 is transmitted. Thereafter, the process proceeds to step S206.

In step S206, the forward voltage value V _F (Nth) is detected. Thereafter, the process proceeds to step S207.

Then, in step S207, whether or not reduction rate of the forward voltage _{V F} is the third threshold value Rt2 more is determined. That is, the detected forward voltage V _{F (second} N-th) in step S207, divided by the period τ5 a difference between the detected forward voltage V _{F (second} N-1 th) in step S207 to the previous value Is greater than or equal to the third threshold value Rt2. If reduction rate of the forward voltage V _F is the third threshold value Rt2 above, the process proceeds to step S209, if reduction ratio of the forward voltage V _F is not the third threshold value Rt2 above, Proceed to step S208.

  In step S208, it is determined whether or not the forward voltage value detection period τ12 has ended. When the forward voltage value detection period τ12 ends, the process proceeds to step S211 (see FIG. 16), and when the forward voltage value detection period τ12 does not end, the process returns to step S206.

  Then, as shown in FIG. 16, in step S211, reception of the ultrasonic wave B2, image processing, and image display on the image display unit 40 are performed. Thereafter, the process proceeds to step S212.

  In step S212, supply of small electric power (small current) is stopped. Thereafter, the process proceeds to step S213.

  In step S213, light irradiation is performed. That is, power (for example, a current value of 15 A) that can detect the acoustic wave A <b> 1 generated by the detection target inside the subject 10 is supplied from the light source driving unit 323 to the light source unit 21. Thereafter, the process proceeds to step S214.

  In step S214, reception of the acoustic wave A1, image processing, and image display on the image display unit 40 are performed. Thereafter, the process proceeds to step S215.

  Then, in step S215, it is determined whether or not “observation” has been completed. That is, it is determined whether or not a signal for ending “observation” has been received. When “observation” is ended, the light irradiation control process of the photoacoustic imaging apparatus 300 according to the third embodiment is ended. When “observation” is not ended, the process returns to step S202 (see FIG. 15). .

Further, as shown in FIG. 15, in step S209 to proceed when reduction rate of the forward voltage _{V F} is the third threshold value Rt2 more in step S207, the temperature inside the probe unit 320 is abnormal It is judged. Then, the process proceeds to step S210.

  In step S210, the supply of small electric power (small current) is stopped. Thereafter, the light irradiation control process of the photoacoustic imaging apparatus 300 according to the third embodiment is ended (see FIG. 16). That is, in this case, irradiation of light from the light source unit 21 and generation of the ultrasonic wave B1 by the detection generation unit 24 are stopped.

  In the third embodiment, the following effects can be obtained.

In the third embodiment, as described above, the light source driving unit 323 irradiates the subject 10 with light from the light emitting diode element 21a, and detects the acoustic wave A1 generated by the detection target inside the subject 10. During the detection operation (light irradiation period τ11), a power (small current) smaller than the power supplied to the light source unit 21 is supplied to the light source unit 21 and a small power (small current) is supplied (small current). based on the forward voltage value V _F of the light emitting diode element 21a corresponding to the detected temperature of the light emitting diode element 21a to the supply period τ13), configured to stop supplying power to the light source unit 21. As a result, in the small current supply period τ13, heat generation associated with light irradiation from the light emitting diode element 21a can be reduced. As a result, since the reduction of the forward voltage V _F due to heat generation is suppressed, it is possible to more accurately, the temperature in the vicinity of the detector generator 24 (internal probe section 320) determines whether abnormal or not . Other effects of the photoacoustic imaging apparatus 300 according to the third embodiment are the same as those of the photoacoustic imaging apparatus 100 according to the first embodiment.

(Fourth embodiment)
Next, the configuration of the photoacoustic imaging apparatus 400 according to the fourth embodiment will be described with reference to FIGS. 1 and 17. In the fourth embodiment, unlike the photoacoustic imaging device 100 according to the first embodiment configured such that all of the plurality of light emitting diode elements are connected in series with each other, of the plurality of light emitting diode elements 21a. The plurality of light emitting diode elements 21a are configured to form a plurality of light emitting element groups connected in series with each other.

  As shown in FIG. 1, the photoacoustic imaging apparatus 400 according to the fourth embodiment is provided with a probe unit 420 and a main body unit 430. The probe unit 420 includes a light source unit 421, a light source driving unit 422, and a forward voltage detection unit 423. The main body 430 is provided with a control unit 431.

Here, in the fourth embodiment, the light source unit 421 includes light emitting element groups 421a to 421c formed by connecting some of the plurality of light emitting diode elements 21a in series. It is comprised so that it may contain. Further, the forward voltage detection unit 423 is configured to be able to detect the respective forward voltages _V F 1 to V _F 3 of the light emitting element group 421A～421c. In addition, the light source driving unit 422 stops supplying power to the light source unit 421 based on a decrease in one of the forward voltage values V _F 1 to V _F 3 of the light emitting element groups 421a to 421c. Is configured to do.

Specifically, as shown in FIG. 17, the plurality of light emitting diode elements 21a are arranged at a predetermined interval along the arrangement direction (X direction) in which the ultrasonic transducers 24e are arranged. . The light emitting element group 421a is formed by connecting a plurality of light emitting diode elements 21a arranged on the arrow X1 direction side to each other in series. The light emitting element group 421c is formed by connecting a plurality of light emitting diode elements 21a arranged on the arrow X2 direction side to each other in series. The light emitting element group 421b is formed by connecting a plurality of light emitting diode elements 21a arranged in the center in the X direction in series. Note that the forward voltage value of the light emitting element group 421a is the forward voltage value V _F 1, the forward voltage value of the light emitting element group 421b is the forward voltage value V _F 2, and the forward voltage value of the light emitting element group 421c is the forward voltage value V _F 3. To do.

Then, the light source driving unit 422 is configured to be capable to apply the driving voltage _{V D} 1 to the respective light emitting element groups 421A～421c (supplying power). Further, the forward voltage value detection unit 423 is connected to the respective light emitting element groups 421A～421c, to be capable of detecting each of the forward voltage value _V F 1 to V _F 3 of the light emitting element group 421A～421c It is configured.

Then, the control unit 431, if any of the respective forward voltages _V F 1 to V _F 3 of the light emitting element group 421a~421c by the light source driving unit 422 is less than the fourth threshold value Vt2, the light source It is comprised so that control which stops supply of the electric power to the part 421 may be performed. That is, irradiation of light from the light source unit 421 is stopped based on the temperature rise of any one of the light emitting element groups 421a to 421c. The fourth threshold value Vt2 is set in the same manner as the first threshold value Vt1 according to the first embodiment. The other configuration of the photoacoustic imaging apparatus 400 according to the fourth embodiment is the same as that of the photoacoustic imaging apparatus 100 according to the first embodiment.

  In the fourth embodiment, the following effects can be obtained.

In the fourth embodiment, as described above, the light source unit 421 includes the light emitting element group 421a formed by connecting some of the plurality of light emitting diode elements 21a in series with each other. To 421c. Further, the forward voltage detection unit 423, the possibility to configure to detect the respective forward voltages _V F 1 to V _F 3 of the light emitting element group 421A～421c. In addition, the light source driving unit 422 stops supplying power to the light source unit 421 based on a decrease in one of the forward voltage values V _F 1 to V _F 3 of the light emitting element groups 421a to 421c. To be configured. Thus, unlike the case of detecting the sum of forward voltage values (forward voltage value V _F ) of all the light emitting diode elements 21a, the vicinity (probe) of the (local) detection generation unit 24 for each of the light emitting element groups 421a to 421c. It is possible to detect an abnormality in the temperature inside the unit 420. The other effects of the photoacoustic imaging apparatus 400 according to the fourth embodiment are the same as those of the photoacoustic imaging apparatus 100 according to the first embodiment.

(Fifth embodiment)
Next, the configuration of the photoacoustic imaging apparatus 500 according to the fifth embodiment will be described with reference to FIGS. 1 and 18. In the fifth embodiment, the supply of power to the light source unit is stopped based on the decrease in the forward voltage value of the light emitting diode element arranged closest to the detection generation unit among the plurality of light emitting diode elements. Is configured to do.

  As shown in FIG. 1, the photoacoustic imaging apparatus 500 according to the fifth embodiment includes a probe unit 520 and a main body unit 530. The probe unit 520 is provided with a light source unit 521, a light source drive unit 522, and a forward voltage detection unit 523. The main body 530 is provided with a control unit 531.

Here, in the fifth embodiment, the control unit 531 uses the light source driving unit 522 to forward voltage value V of the light emitting element group 521a disposed closest to the detection generation unit 24 among the light emitting element groups 521a to 521c. _{When F} is less than or equal to the fifth threshold value Vt3, control is performed to stop the supply of power to the light source unit 521. The fifth threshold value Vt3 is set in the same manner as the first threshold value Vt1 according to the first embodiment.

  Specifically, as shown in FIG. 18, the plurality of light emitting diode elements 21a include light emitting element groups 521a to 521c. The light emitting element groups 521a to 521c are arranged at a predetermined interval along the arrangement direction (X direction) in which the ultrasonic transducers 24e are arranged.

  The light emitting element group 521a is arranged on the arrow Z1 direction side and on the arrow Z2 direction side of the ultrasonic transducer 24e. The light emitting element groups 521b and 521c are disposed on the arrow Z2 direction side of the light emitting element group 521a. That is, the light emitting element group 521a is disposed closest to the detection generation unit 24 (the ultrasonic transducer 24e) among the light emitting element groups 521a to 521c.

Further, the forward voltage detection unit 523 is configured to detect a forward voltage V _F of the light emitting element group 521a. Then, the control unit 531, when the forward voltage value V _F obtained is equal to or less than the fifth threshold value Vt3, is configured to perform control of stopping supply of electric power to the light source unit 521 by the light source driving unit 532 ing. The other configuration of the photoacoustic imaging apparatus 500 according to the fifth embodiment is the same as that of the photoacoustic imaging apparatus 100 according to the first embodiment.

  In the fifth embodiment, the following effects can be obtained.

In the fifth embodiment, as described above, the light source driving unit 522, the forward voltage value _{V F} of the light emitting element groups 521a that is located closest to the detector generator 24 of the light emitting element group 521a~521c Based on this, the power supply to the light source unit 521 is stopped. As a result, the light emitting element group 521a of the light emitting element groups 521a to 521c that is disposed closest to the detection generating unit 24 is located in the vicinity of the detection generating unit 24 (probe) because the distance from the detection generating unit 24 is small. It is possible to quickly detect a change in temperature inside the portion 520. Other effects of the photoacoustic imaging apparatus 500 according to the fifth embodiment are the same as those of the photoacoustic imaging apparatus 100 according to the first embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the first to fifth embodiments, an example in which the supply of power from the light source driving unit to the light source unit is stopped based on the forward voltage value, and the light irradiation from the light source unit is stopped. However, the present invention is not limited to this. In the present invention, based on the forward voltage value, the supply of power from the light source driving unit to the light source unit is limited (current value is reduced), and the irradiation of light from the light source unit is limited (the light amount is reduced). You may comprise.

Further, in the first embodiment, when the forward voltage value detected by the forward voltage detection unit is equal to or less than the first threshold value, power is supplied from the light source driving unit to the light source unit according to a command from the control unit. Although the example configured to stop is shown, the present invention is not limited to this. In this invention, you may comprise so that supply of the electric power from a light source drive part to a light source part may be stopped by means other than the instruction | command of a control part. For example, as in the modification shown in FIG. 19, provided with a comparator 623b in the forward voltage detection unit 623, the forward voltage V _F of the forward voltage detecting unit 623 has detected it reaches the first threshold value Vt1 below In such a case, a stop signal may be directly transmitted to the light source driving unit 622 without using the control unit 631, and the supply of power from the light source driving unit 622 to the light source unit 21 may be stopped.

Here, as shown in FIG. 19, the photoacoustic imaging apparatus 600 according to the first modification is provided with a light source drive unit 622, a forward voltage detection unit 623, and a control unit 631. Further, the forward voltage detection unit 623 is provided with a comparator 623b. The comparator 623b includes a like comparator is configured to obtain the forward voltage V _F detected by the forward voltage circuit 23a. The comparator of the comparator 623b receives a voltage value corresponding to the first threshold value Vt1 as a reference voltage. Thus, the comparator 623b is forward voltage V _F is configured to be capable of equal to or less than a first threshold value Vt1. Then, the comparator 623b, when the forward voltage V _F is equal to or less than the first threshold value Vt1, without passing through the control unit 631 outputs a power supply stop signal to the light source driver 622, a light source drive The unit 622 is configured to stop the supply of power to the light source unit 21 based on the power supply stop signal.

  Moreover, although the example which provides the light source drive part of this invention in a probe part was shown in the said 1st-5th embodiment, this invention is not limited to this. In this invention, you may provide a light source drive part other than a probe part. For example, the light source driving unit may be provided in the main body unit.

  Further, in the second embodiment and the third embodiment, the forward voltage value reduction rate of the present invention is the difference between the forward voltage value (Nth time) and the previously detected forward voltage value (N-1th time). And although the example comprised so that it might calculate by dividing by a predetermined period was shown, this invention is not limited to this. In the present invention, a method other than the method of dividing the forward voltage value decrease rate by a predetermined period by subtracting the forward voltage value (Nth) from the previously detected forward voltage value (N-1). You may calculate by. For example, the forward voltage value is detected five times by the forward voltage value detection unit, and the decrease value of the detected forward voltage value is divided by the elapsed time (predetermined period × 5) detected five times to calculate the decrease rate. May be. Thereby, it is possible to suppress the influence of disturbance noise and the like.

  Moreover, in the said 1st-5th embodiment, when it determines that the temperature of the vicinity of a detection production | generation part is abnormal based on a forward voltage value, supply of the electric power from a light source drive part to a light source part is stopped. In addition, although an example is shown in which the irradiation of ultrasonic waves from the detection generation unit is stopped, the present invention is not limited to this. In the present invention, when the temperature in the vicinity of the detection generation unit is determined to be abnormal based on the forward voltage value, the supply of power from the light source drive unit to the light source unit is stopped, while the super You may comprise so that irradiation of a sound wave may be continued.

  Moreover, although the example which comprises the probe part of this invention by linear shape was shown in the said 1st-5th embodiment, this invention is not limited to this. In the present invention, the probe portion may be configured by a shape other than the linear type. For example, the probe portion may be configured by a convex shape or may be configured by a sector shape.

  In the first to fifth embodiments, the signal such as the optical trigger signal of the present invention has been described with reference to the voltage level example (H or L), but the present invention is not limited to this. The present invention is not limited to the voltage level examples for signals such as the optical trigger signal described above. For example, when the voltage level of the light trigger signal is L, the light source unit may be configured to emit light.

  Moreover, in the said 1st-5th embodiment, when the forward voltage value is below a 1st threshold value, the structure which stops supply of the electric power to a light source part, and the fall rate of a forward voltage value are 2nd. Although the configuration in which the supply of power to the light source unit is stopped when it is equal to or greater than the threshold has been described as a separate embodiment, the present invention is not limited to this. In the present invention, when the forward voltage value is equal to or lower than the first threshold value, the supply of power to the light source unit is stopped, and when the forward voltage value decrease rate is equal to or higher than the second threshold value. You may comprise so that both the structure which stops supply of the electric power to a light source part may be provided.

  In the first to fifth embodiments, for convenience of explanation, the processing of the control unit of the present invention has been described using a flow-driven flowchart in which processing is performed in order along the processing flow. Not limited to. In the present invention, the processing operation of the control unit may be performed by event-driven (event-driven) processing that executes processing for each event. In this case, it may be performed by a complete event drive type or a combination of event drive and flow drive.

  Moreover, although the said 1st-5th embodiment showed the example which irradiates light to a test object using a light emitting diode element as a light emitting element of this invention, this invention is not limited to this. In this invention, you may comprise so that light may be irradiated to a subject using light emitting elements other than a light emitting diode element. For example, a semiconductor laser element 721a (or an organic light emitting diode element 821a) may be used for the light source unit 721 (or 821) as in the modification shown in FIG.

  Here, as shown in FIG. 20, the light source unit 721 according to the second modification is provided with a semiconductor laser element 721a, which is configured to irradiate the subject 10 with light. In this case, the semiconductor laser element 721a can irradiate the subject 10 with laser light having a relatively high directivity as compared with the light emitting diode element, so that most of the light from the semiconductor laser element 721a is reliably covered. The specimen 10 can be irradiated.

  Further, as shown in FIG. 20, the light source unit 821 according to the third modified example is provided with an organic light emitting diode element 821a, and is configured to be able to irradiate the subject 10 with light from the organic light emitting diode element 821a. . In this case, the organic light emitting diode element 821a can be easily thinned, and the light source unit 821 can be easily downsized.

10 Subject 21a Light emitting diode element (light emitting element)
22, 222, 322, 422, 522, 622 Light source drive unit 23, 323, 423, 523, 623 Forward voltage detection unit 24 Detection generation unit 100, 200, 300, 400, 500, 600 Photoacoustic imaging apparatus 421a to 421c 521a to 521c Light emitting element group 721a Semiconductor laser element (light emitting element)
821a Organic light-emitting diode element (light-emitting element)

Claims (9)

A detection generator capable of detecting an acoustic wave generated by light being absorbed by a detection target inside the subject and generating an ultrasonic wave for irradiating the subject;
A light emitting element that is provided in the vicinity of the detection generation unit and capable of irradiating the subject with light;
A light source driving unit that supplies the light emitting element with power for generating light by the light emitting element;
A forward voltage detector capable of detecting a forward voltage value of the light emitting element,
The light source driving unit stops supplying power to the light emitting element based on the forward voltage value of the light emitting element corresponding to the temperature of the light emitting element detected by the forward voltage detecting unit, or A photoacoustic imaging apparatus configured to limit power supply to a light emitting element.   The light source driving unit stops supplying power to the light emitting element when a forward voltage value of the light emitting element corresponding to a temperature of the light emitting element is equal to or lower than a first threshold value, or The photoacoustic imaging apparatus according to claim 1, wherein the photoacoustic imaging apparatus is configured to limit power supply to the light emitting element.   The light source driving unit, when the rate of decrease of the forward voltage value of the light emitting element corresponding to the temperature of the light emitting element is equal to or higher than a second threshold, to stop the supply of power to the light emitting element, Or the photoacoustic imaging device of Claim 1 or 2 comprised so that supply of the electric power to the said light emitting element may be restrict | limited.   The light source driving unit emits light from the light emitting element to the subject and detects the acoustic wave generated by the detection target inside the subject, compared to the power supplied to the light emitting element during the detection operation. Based on a forward voltage value of the light emitting element corresponding to the temperature of the light emitting element detected during a period of supplying the small power to the light emitting element, a small power is supplied to the light emitting element. The photoacoustic imaging apparatus of any one of Claims 1-3 comprised so that supply of power may be stopped or supply of the electric power to the said light emitting element may be restrict | limited. A plurality of the light emitting elements are provided,
A part of the plurality of light emitting elements among the plurality of light emitting elements forms a plurality of light emitting element groups connected in series with each other,
The forward voltage detection unit is configured to be able to detect a forward voltage value of each of the plurality of light emitting element groups,
The light source driving unit stops supplying power to the light emitting element based on a decrease in one of the forward voltage values of each of the plurality of light emitting element groups, or to the light emitting element. The photoacoustic imaging device according to claim 1, wherein the photoacoustic imaging device is configured to limit supply of electric power. A plurality of the light emitting elements are provided,
The light source driving unit supplies power to the light emitting element based on a decrease in a forward voltage value of the light emitting element disposed closest to the detection generation unit among the plurality of light emitting elements. The photoacoustic imaging device according to claim 1, wherein the photoacoustic imaging device is configured to stop the power supply or to limit power supply to the light emitting element.   The photoacoustic imaging apparatus according to claim 1, wherein the light emitting element is configured by a light emitting diode element.   The photoacoustic imaging apparatus according to claim 1, wherein the light emitting element is configured by a semiconductor laser element.   The photoacoustic imaging apparatus according to claim 1, wherein the light emitting element is configured by an organic light emitting diode element.

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