KR20180106902A - Photoacoustic apparatus and control method thereof, and photoacoustic probe - Google Patents

Abstract

A probe including a light source and an acoustic wave generated from a subject irradiated with light from the light source; A temperature information acquisition unit for acquiring a temperature of the probe; And a control unit for controlling irradiation of light by the light source in accordance with the temperature.

Description

[0001] PHOTOACOUSTIC APPARATUS AND CONTROL METHOD THEREOF, AND PHOTOACOUSTIC PROBE [0002]

The present invention relates to a photoacoustic apparatus, a control method thereof, and a photoacoustic probe.

BACKGROUND ART [0002] Recently, as an imaging technique using light, a photoacoustic device that images the interior of a subject using a photoacoustic effect has been researched and developed. The photoacoustic apparatus is a device that generates an image of the inside of a subject using ultrasound (photoacoustic wave) generated by a photoacoustic effect from a light absorber that absorbs energy of light irradiated to the subject.

Like the ultrasonic diagnostic apparatus, a photoacoustic apparatus that forms a shape of a hand-held probe and can easily access a region to be observed has been researched and developed. Japanese Patent Laying-Open No. 2016-047077 discloses a photoacoustic imaging apparatus having a probe incorporating a light source and a receiver.

Japanese Patent Application Laid-Open No. 2016-047077

A part of the power supplied to the light source for light emission is converted into heat, and the light source generates heat. When the probe has a light source (if the light source is disposed inside the housing), the temperature of the probe may rise due to heat generation of the light source. The temperature rise of the probe may cause defects in the apparatus due to heat or inconvenience such as knee or object of the examinee.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a technique for suppressing temperature rise of a probe due to heat generation of a light source in an apparatus in which a light source is embedded in the probe.

According to the present invention,

A probe including a light source and an acoustic wave generated from a subject irradiated with light from the light source;

A temperature information acquisition unit for acquiring a temperature of the probe; And

And a control unit for controlling irradiation of light by the light source in accordance with the temperature.

Further, according to the present invention,

Light source;

A receiving unit for receiving an acoustic wave generated from a subject irradiated with light from the light source;

A temperature information acquisition unit for acquiring the temperature of the photoacoustic probe; And

And a control unit for controlling irradiation of light by the light source according to the temperature.

Further, according to the present invention,

Irradiating light onto a subject with a light source included in the probe;

The receiving unit included in the probe receiving the acoustic wave generated from the subject to which the light is irradiated;

The temperature information acquiring unit acquiring the temperature of the probe; And

And the control unit controls the irradiation of the light by the light source in accordance with the temperature.

According to the present invention, it is possible to provide a technique for suppressing an increase in temperature of the probe due to heat generation of a light source in an apparatus in which a light source is embedded in the probe.

Further features of the present invention will become apparent from the following description of the embodiments with reference to the accompanying drawings.

1 is a block diagram of a photoacoustic apparatus according to a first embodiment,
2 is a schematic diagram of a hand-held probe according to the first embodiment,
3 is a block diagram showing a computer and a peripheral configuration according to the first embodiment,
4A to 4C are timing charts for explaining the amount of heat per unit time,
5 is a flowchart of the control of the first embodiment,
6A and 6B are graphs for explaining the light irradiation control method in the tracking priority protection mode,
Figs. 7A and 7B are graphs illustrating another method of controlling the light irradiation control in the tracking priority protection mode,
8A and 8B are graphs for explaining the light irradiation control method of the image quality first protection mode,
9A and 9B show another graph for explaining the light irradiation control method in the image quality first protection mode,
10A and 10B are graphs illustrating a light irradiation control method in a normal protection mode,
11 is a flowchart of the control of the second embodiment,
12A and 12B are graphs for explaining the light irradiation control method according to the second embodiment,
13 is a flowchart of control in the third embodiment,
14 is a graph for selecting a characteristic curve based on the velocity and the pressing force of the probe,
15A to 15D are flow charts of the control of the seventh embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, relative positions, and the like of the components described below should be appropriately changed depending on the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, it is not intended to limit the scope of the present invention to the embodiments described below.

TECHNICAL FIELD [0001] The present invention relates to a technique for detecting an acoustic wave propagated from a subject, generating characteristic information inside the subject, and acquiring the characteristic information. Accordingly, the present invention can be regarded as a subject information obtaining apparatus or a control method thereof, or a subject information obtaining method and a signal processing method. Further, the present invention can be regarded as a display method of generating and displaying an image representing characteristic information inside the subject. The present invention can also be considered as a program for causing these methods to be executed by an information processing apparatus having a hardware resource such as a CPU or a memory, or a computer-readable non-volatile storage medium for storing the program.

A subject information acquiring apparatus according to the present invention is a subject information acquiring apparatus for acquiring an acoustic wave generated inside a subject by irradiating light (electromagnetic wave) to a subject and acquiring characteristic information of the subject as image data, And an acoustic imaging device. In this case, the characteristic information refers to the information of characteristic values corresponding to each of a plurality of positions in the inspected object, which are generated by using signals derived from the received photoacoustic wave.

The photoacoustic image data according to the present invention is a concept including all image data derived from a photoacoustic wave generated by light irradiation. For example, the photoacoustic image data may include at least one of a sound pressure (initial sound pressure) of the photoacoustic wave, an energy absorption density and an absorption coefficient, and a concentration of a substance constituting the subject (for example, oxygen saturation) And image data representing characteristic information. In addition, photoacoustic image data representing spectral information such as the concentration of a substance constituting the subject is obtained based on the photoacoustic wave generated by light irradiation of a plurality of different wavelengths. The photoacoustic image data representing the spectral information may be a value obtained by weighting the intensity of oxygen saturation and oxygen saturation with an absorption coefficient, total hemoglobin concentration, oxyhemoglobin concentration, or dioxyhemoglobin concentration. Alternatively, the photoacoustic image data representing the spectral information may be a glucose concentration, a collagen concentration, a melanin concentration, or a volume fraction of fat or water.

A two-dimensional or three-dimensional characteristic information distribution is obtained based on the characteristic information of each position in the body. The distribution data can be generated as image data. The characteristic information may be obtained not as numerical data but as distribution information of each position inside the subject. In other words, distribution information such as initial sound pressure distribution, energy absorption density distribution, absorption coefficient distribution, and oxygen saturation distribution can be obtained.

Acoustic waves according to the invention are typically ultrasonic waves and include acoustic waves, also called acoustic waves or acoustic parasites. A signal (for example, an electric signal) converted from an acoustic wave by a transducer or the like is also referred to as an acoustic signal. However, the description of the ultrasonic waves and acoustic waves in this specification is not intended to be limited to the wavelength of the acoustic waves. The acoustic wave generated by the photoacoustic effect is called photoacoustic wave or optical ultrasound. A signal (e.g., an electrical signal) derived from a photoacoustic wave is also referred to as a photoacoustic signal. The distribution data is also called photoacoustic image data or reconstructed image data.

In the following embodiments, a photoacoustic probe used for acquiring a photoacoustic signal and including a light source and a receiver will be described in detail. Therefore, the present invention can also be regarded as a photoacoustic probe and its control method. In the following embodiments, a photoacoustic probe of a handheld type is also described, but the probe according to the present invention is not limited to a handheld probe.

In the photoacoustic measurement, in general, the intensity of the photoacoustic wave increases as the light quantity of the irradiating light is larger, and the S / N ratio of the photoacoustic wave received signal is improved. As a result, photoacoustic image data with high image quality when displayed is obtained.

In a handheld probe of a photoacoustic apparatus, it is conceivable to arrange a light source in a probe housing. Also in such a configuration, it is preferable to increase the light amount of the irradiation light in order to display a high-quality photoacoustic image. However, when a part of the electric power supplied to the light source is converted into heat, the light source generates heat, and therefore, when large power is supplied to the light source for the purpose of increasing the light amount of the light, the heat generation amount of the light source also increases.

In the present specification, the "light amount" is defined as the total amount of light energy of one pulse (unit: J (row)) (hereinafter also referred to as irradiation amount). The product obtained by multiplying the light amount by the number of times of light emission per second (the repetition frequency of light irradiation) is defined as the average power (unit: W (watt)) of the irradiation light.

For example, when a laser diode is used as a light source and light is emitted at an interval of 0.1 second at a light amount of 0.01 [J] (10 times per second), the average power of the irradiation light is 0.01 [J] Times / s] = 0.1 [W]. In this case, assuming that the photoelectric conversion efficiency with respect to the supply power is 10 [%], the supply power 1 [W] is required to generate the average power at 0.1 [W]. In this case, the amount of heat generated per unit time of the light source is 0.9 [W]. In this case, it is assumed that all of the power supplied to the light source, which is not converted to light, is converted into heat. Further, the light of one pulse includes light of all waveforms including triangular waves and sinusoidal waves in addition to light whose temporal change in light intensity is a square wave.

It is difficult to provide the hand-held probe with a cooling mechanism such as forced air cooling and water cooling. Therefore, even when the amount of heat generated by the light source provided inside the housing is small, there is a possibility that a temperature rise occurs inside the housing. This temperature rise may cause a device defect in the housing. Further, due to the temperature rise of the housing, there is a possibility that the user who is handling the probe, the user such as a doctor, and the patient who is the subject may feel uncomfortable.

The inventor of the present invention has found that a temperature information acquisition unit such as a temperature sensor is mounted in a handheld probe or a housing and then the amount of light and the repetition frequency of light irradiation Thereby achieving optimal control. In other words, the present inventor has reached the point of controlling the amount of light and the repetition frequency of light irradiation so that the temperature of the interior of the handheld probe or the housing does not exceed a predetermined upper limit value, thereby controlling the power supplied to the light source. Typically, the power supplied to the light source is appropriately adjusted so that the temperature rise due to the heating value proportional to the value obtained by multiplying the light amount of the irradiation light by the repetition frequency of the light irradiation is not more than the allowable temperature, do.

In addition, when the subject is skin of a human body, the maximum allowable exposure dose (MPE) should be maintained. The light amount may be limited so as not to exceed the MPE, in addition to the limitation of the temperature inside the handheld probe or the housing temperature.

The application of the present invention is not limited to the photoacoustic apparatus described in the following embodiments. The present invention is applicable to any device having a light source embedded in a hand-held probe. For example, the present invention may be applied to a handheld type probe incorporating a light source and a light receiving element that receives reflected light or transmitted light of the light emitted from the light source. In other words, the present invention may be applied to an apparatus comprising a handheld probe having a light source and an information acquisition unit for acquiring information about an object to be irradiated based on a reception signal of light propagated through the object to be irradiated.

First Embodiment

Device Configuration

Hereinafter, the configuration of the photoacoustic apparatus according to the present embodiment will be described with reference to FIG. 1 is a schematic block diagram of the entire photoacoustic apparatus. The photoacoustic apparatus according to the present embodiment includes a probe 180 (a light irradiating unit 110, a receiving unit 120 and a temperature sensor 200), a signal collecting unit 140, a computer 150, a display unit 160, an input unit 170, And a power supply unit 190.

When the light irradiation unit 110 irradiates light to the subject 100, photoacoustic waves are generated from the light absorber inside the subject 100 or the surface due to the photoacoustic effect. The power supply unit 190 supplies electric power for driving the light source of the light irradiation unit 110. The receiving unit 120 receives the photoacoustic wave and outputs an electric signal (photoacoustic signal) as an analog signal.

The signal collecting unit 140 converts the analog signal output from the receiving unit 120 into a digital signal and outputs the digital signal to the computer 150. The computer 150 stores the digital signal output from the signal collecting unit 140 as signal data derived from a photoacoustic wave.

The computer 150 performs processing to be described later on the stored digital signal to generate image data. The computer 150 performs image processing for displaying the obtained image data, and then outputs the image data to the display unit 160. [ The display unit 160 displays a photoacoustic image. A doctor, article or the like as a user can perform a diagnosis by checking the photoacoustic image displayed on the display unit 160. [ The display image is stored in the memory in the computer 150, the data management system connected with the modality and the network, or the like, based on a saving instruction from the user or the computer 150. [

As the reconstruction algorithm for converting the signal data into three-dimensional volume data, any technique such as time domain back projection, Fourier domain back projection, and model based method (iterative calculation method) can be adopted. Examples of time domain back projection include Universal Back Projection (UBP), Filter Correction Back Projection (FBP), or phasing addition (Delay-and-Sum). In image reconstruction, the absorption coefficient distribution is acquired based on the initial sound pressure distribution of the photoacoustic wave and the light amount distribution inside the subject. In the present invention, the amount of irradiation light is changed dynamically according to the temperature of the probe, so that the light amount distribution inside the object is also changed. In consideration of this, it is preferable that, when the computer performs image reconstruction, the signal data is corrected by a method of referring to the light amount information at the time of acquisition of the photoacoustic wave and applying a gain as necessary.

The display unit 160 may display a GUI or the like in addition to the image generated by the computer 150. [ The input unit 170 is configured to accept input of information by the user. The user can use the input unit 170 to perform operations such as start and end of measurement, storage indication of a created image, and the like.

The probe 180

2 is a schematic diagram of a handheld probe 180 according to the present embodiment. The probe 180 includes a light irradiation unit 110, a receiving unit 120, a temperature sensor 200, and a housing 181.

The temperature sensor 200 inside the probe 180 is preferably a housing 181 serving as a movable portion or a vicinity of the light source or the driver circuit 114 of the light irradiating portion 110 having a strict operating temperature condition . The temperature sensor 200 is mounted by thermal bonding at such a suitable installation place. The temperature sensor 200 outputs the temperature of the inside of the probe (for example, the vicinity of the light source) or the temperature of the housing (hereinafter simply referred to as the probe temperature) to the computer 150 as an analog signal or a digital signal .

The housing 181 is a housing surrounding the light irradiation unit 110 and the receiving unit 120. By holding the housing 181, the user can use the probe 180 as a handheld probe.

The light irradiation unit 110 includes a light source 111, an optical system 112 for propagating light generated from the light source 111, and a driver circuit 114 for driving the light source 111. The optical system 112 propagates light generated from a light source 111 such as an LED or an LD and exits from the emission end 113. [

The probe 180 is connected to the signal collecting unit 140, the computer 150 and the power supply unit 190 via a cable 182. [ The cable 182 includes a wiring for supplying power to the driver circuit 114 from the power supply unit 190, a wiring for sending a control signal for controlling the light amount and the light emission timing to the driver circuit 114 from the control unit 153, And a wiring for transmitting the analog signal output from the signal collecting unit 140 to the signal collecting unit 140. The cable 182 may be provided with a connector and may be configured to separate the probe 180 and other components of the photoacoustic device. In the present embodiment, the configuration in which the driver circuit 114 and the power supply unit 190 are combined corresponds to a drive unit that supplies power to the light source 111. [ In other words, the driving unit according to the present embodiment includes the driver circuit 114 and the power supply unit 190.

Also, the probe 180 according to the present embodiment may be a wireless hand-held probe 180 without a cable 182. In this case, the power supply unit 190 may be built in the probe 180, and various signals may be wirelessly transmitted and received between the probe 180 and other components. However, when the power supply unit 190 is built in the probe 180, the amount of heat generated inside the housing 181 increases due to the heat generated by the power consumption of the power supply unit 190. Therefore, in order to suppress the temperature rise inside the housing 181, the power supply unit 190 may be disposed outside the housing 181. [ Furthermore, a part of the driver circuit 114 having a large power consumption and a large heating value may be disposed outside the housing 181.

Detailed configuration

Hereinafter, the details of each component of the photoacoustic apparatus according to the present embodiment will be described.

The light-

The light irradiation unit 110 includes a light source 111, an optical system 112, and a driver circuit 114.

As the light source 111, a laser diode (LD) or a light emitting diode (LED) is suitable. As the light source 111, an LD or an LED capable of emitting light so as to follow a serrated drive waveform (drive current) of 1 MHz or more may be employed. However, if light for generating a photoacoustic wave can be emitted, the light source is not limited to LD or LED. Further, it is possible to acquire the degree of oxygen saturation using the wavelength variable light source as the light source 111. [

The pulse width of the light emitted by the light source 111 is typically 1 ns or more and 1 μs or less. Also, as the wavelength of light, a range of about 400 nm to 1600 nm can be used. When capturing a blood vessel at a high resolution, a wavelength (400 nm or more and 700 nm or less) that is well absorbed by a blood vessel is preferable. When capturing the deep portion of a living body, a wavelength (700 nm or more and 1100 nm or less) at which a background tissue (water or fat, etc.) of a living body is typically weakly absorbed is preferable. However, the pulse width and the wavelength are not limited to the above.

As the optical system 112, optical elements such as a lens, a mirror, and an optical fiber can be used. When a breast or the like is used as the subject 100, a light diffusing plate or the like may be used as the emitting end 113 of the optical system for irradiating the subject 100 with a beam diameter of a pulse beam widened. On the other hand, in the photoacoustic microscope, in order to increase the resolution, the emission end 113 of the optical system 112 may be formed of a lens or the like, and the focused beam may be irradiated. It is also possible that the light irradiation unit 110 does not have the optical system 112 and that the light source 111 directly irradiates the subject 100 with light. The driver circuit 114 is a circuit for generating a drive current for driving the light source 111 using electric power from the power supply unit 190.

The receiving unit 120,

The receiving unit 120 includes a transducer for receiving an acoustic wave to output an electric signal, and a support for supporting the transducer. As the member constituting the transducer, a piezoelectric ceramics material typified by lead zirconate titanate (PZT), a polymer piezoelectric film material typified by polyvinylidene fluoride (PVDF), or the like can be used. In addition to piezoelectric elements, a capacitive micro-machined ultrasonic transducer (CMUT) or a transducer using a Fabry-Perot interferometer can be used. Any kind of transducer may be employed as long as it can receive an acoustic wave and output an electric signal. Since the frequency components constituting the photoacoustic wave are typically 100 KHz to 100 MHz, it is preferable to use a transducer capable of detecting these frequencies.

The signal obtained by the transducer is a time-resolved signal. That is, the amplitude of the signal obtained by the transducer indicates a value based on the sound pressure received at the transducer at each time (for example, a value proportional to the sound pressure).

A plurality of transducers may be arranged side by side on a flat or curved surface called a 1D array, a 1.5D array, a 1.75D array, or a 2D array.

The receiving unit 120 may also include an amplifier for amplifying the time-series analog signal output from the transducer. Also, the receiving section 120 may include an A / D converter for converting the time-series analog signal output from the transducer into a time-series digital signal. In other words, the receiving unit 120 may include the signal collecting unit 140, which will be described later.

Ideally, when a plurality of transducers are used, it is preferable to arrange a transducer to enable the transducer to surround the entire periphery of the subject 100. However, when the subject 100 is large, it is impossible to dispose the transducer so as to surround the entire periphery of the subject 100. In this case, by arranging the transducer on the hemispherical supporter, acoustic waves propagating in many directions from the subject 100 can be received. Further, the arrangement and number of the transducers and the shape of the support may be optimized according to the test body, and are not limited to the above description.

A medium may be disposed in a space between the receiving section 120 and the inspected object 100 to acoustically match the two. As the medium, a material having an acoustic property at the interface with the inspected object 100 or the transducer and having a high transmittance of the photoacoustic wave as much as possible is employed. As the medium, for example, water, oil, ultrasonic gel or the like can be employed.

Further, when the apparatus according to the present embodiment generates an ultrasonic image by transmission and reception of an acoustic wave in addition to a photoacoustic image, the transducer may function as a transmitter for transmitting an acoustic wave. The transducer as the receiving section and the transducer as the transmitting section may be a single (common) transducer or may be a separate component.

The temperature sensor (200)

The temperature sensor 200 as the temperature information acquiring unit according to the present embodiment will be described. The temperature sensor 200 may be composed of, for example, a sensor such as a thermistor, a thermocouple, or a resistance thermometer. The temperature sensor 200 may be provided in the vicinity of the light source 111 having a strict operating temperature condition (the upper limit temperature is low). It is preferable that the temperature sensor 200 is mounted to the housing 181 by thermal coupling when the temperature limit of the housing 181 which is the movable part is strict (lower limit temperature is low). The apparatus according to the present invention controls at least one of the amount of light and the timing of light irradiation (typically, repetition frequency) so that the temperature of the temperature sensor 200 does not exceed the undetermined upper limit. The control relating to the irradiation of this light is performed by controlling the electric power supplied to the light source. Therefore, it is necessary to mount the temperature sensor 200 by thermal coupling to a portion where temperature rise is desired to be managed.

Instead of the temperature sensor 200 for directly measuring the temperature, the temperature information acquiring unit may acquire the temperature (temperature) by the calculation based on the amount of power supplied to the light source, the amount of heat acquired based on the amount of power and the photoelectric conversion efficiency, An apparatus for acquiring information may be used. Any method may be adopted as long as it can acquire desired temperature information.

The signal collecting unit 140,

The signal collecting unit 140 includes an amplifier for amplifying an electric signal that is an analog signal output from the receiving unit 120 and an A / D converter for converting an analog signal output from the amplifier into a digital signal. The signal collecting unit 140 may be a field programmable gate array (FPGA) chip or the like. The digital signal output from the signal collecting unit 140 is stored in the storage unit 152 in the computer 150. [ The signal collecting unit 140 is also referred to as a data acquisition system (DAS). In this specification, an electric signal is a concept including an analog signal and a digital signal.

The signal collecting unit 140 may start the process as a trigger in synchronization with the light emission from the light irradiating unit 110. [ As the trigger, a signal output from the light detection sensor attached to the emission end 113 of the light irradiation unit 110 can be used. The signal collecting unit 140 may start the process when it receives the measurement start instruction signal from the input unit 170. [

Further, the probe 180 may include a signal collecting unit 140 composed of an amplifier, an ADC, and the like. In other words, the signal collecting unit 140 may be disposed inside the housing 181. With this configuration, the information between the handheld probe 180 and the computer 150 can be propagated as a digital signal, so that the noise resistance can be improved. In addition, by using a high-speed digital signal, it is possible to reduce the number of times of bowing as compared with the case of transmitting an analog signal, and it becomes possible to improve the operability of the hand-held probe 180. [

The computer 150,

The computer 150 as the information processing unit includes an operation unit 151, a storage unit 152, and a control unit 153. [ The function of each part will be described when the processing flow is explained.

The unit for providing the arithmetic function as the arithmetic unit 151 may be a processor such as a CPU or a graphics processing unit (GPU), or an arithmetic circuit such as a field programmable gate array (FPGA) chip. These units may be composed of a single processor or a single arithmetic circuit as well as a plurality of processors or arithmetic circuits. The calculating unit 151 may receive various parameters including the subject sound velocity and the configuration of the holding unit from the input unit 170 and process the received signal.

The storage unit 152 may be constituted by a non-temporary storage medium such as a read-only memory (ROM), a magnetic disk, or a flash memory. The storage unit 152 may be a volatile medium such as a random access memory (RAM). The storage medium in which the program is stored is a non-temporary storage medium. Alternatively, the storage unit 152 may be composed of a plurality of storage media. The storage unit 152 may be connected to the computer 150 on-line. The storage unit 152 can store the photoacoustic image data generated by the arithmetic unit 151 and the display image based on the photoacoustic image data.

The control unit 153 is constituted by calculation elements such as a CPU. The control unit 153 controls the operation of each component of the photoacoustic device. The control unit 153 may control the operation of each component of the photoacoustic device upon receiving the instruction signal according to various operations such as start of measurement from the input unit 170. [ The control unit 153 reads the program codes stored in the storage unit 152 and controls the operation of each component of the photoacoustic device. The computer 150 may be a dedicated workstation. In addition, each component of the computer 150 may be constituted by different hardware and operated in conjunction with each other.

The output of the temperature sensor 200 is input to the control unit 153 by an analog signal or a digital signal. When the output of the temperature sensor 200 is sent to the control section 153 by an analog signal, the analog signal is converted into a digital signal by an A / D converter (not shown) in the control section 153, . The control unit 153 of the computer 150 controls the operation of each component included in the photoacoustic apparatus and controls the light irradiation based on the temperature detected by the temperature sensor. Specifically, the repetition frequency of the light irradiation and the irradiation light amount are controlled. In each of the embodiments described later, the speed detected by the speed sensor or the pressing force detected by the pressure sensor can be used to control light irradiation.

3 shows a specific configuration example of the computer 150 according to the present embodiment. The computer 150 according to the present embodiment includes a CPU 154, a GPU 155, a RAM 156, a ROM 157, and an external storage device 158. A liquid crystal display 161 as a display unit 160 and a mouse 171 and a keyboard 172 as an input unit 170 are connected to the computer 150.

The computer 150 and the receiving unit 120 may be configured to be housed in a common housing. In this case, the photoacoustic probe can be used as a standalone photoacoustic device. Further, a part of the signal processing may be performed by a computer housed in the housing, and the remaining signal processing may be performed by a computer provided outside the housing. In this case, computers installed inside and outside the housing are collectively referred to as computers according to the present embodiment. In other words, the hardware constituting the computer need not be housed in a single housing.

The display unit 160 displays,

The display unit 160 is a display such as a liquid crystal display or an organic electroluminescence (EL) display. The display unit 160 is a device for displaying an image based on the subject information or the like obtained by the computer 150 or a numerical value at a specific position. The display unit 160 may display an image and a GUI for operating the apparatus. In addition, the subject information can be displayed after the image processing (such as adjustment of the luminance value) is performed on the display unit 160 or the computer 150. [

The input unit 170,

As the input unit 170, an operation console configured by a mouse, a keyboard, or the like that can be operated by the user can be used. Further, the display section 160 may be constituted by a touch panel, and the display section 160 may be used as the input section 170. [

Further, each component of the photoacoustic apparatus may be constituted as a separate device, or may be constituted as a single device integrated therewith. Also, at least a part of the components of the photoacoustic apparatus may be constituted as one unit integrated.

The power unit 190,

The power supply unit 190 is a power supply for generating electric power. The power supply unit 190 supplies power to the driver circuit 114 of the light irradiation unit 110. When the power supplied from the power supply unit 190 is consumed by the driver circuit 114 and the light source 111 or the like, heat is generated together with the light. As the power source unit 190, a DC power source, a primary battery, and a secondary battery can be used. When the power source unit 190 is formed of a battery, the power source unit 190 can be accommodated in the probe 180 in a space saving manner. The driver circuit 114 and the power supply unit 190 may be controlled by the control unit 153 in the computer 150. [ The probe 180 may include a control unit for controlling the power supply unit 190 and the driver circuit 114. [

The subject (100)

The subject 100 does not constitute a photoacoustic device, but will be described below. The photoacoustic apparatus according to the present embodiment can be used for the purpose of diagnosing malignant tumors or vascular diseases in humans or animals, and observing the progress of chemotherapy. Therefore, the subject 100 may be a living body, more specifically, a subject to be diagnosed such as a breast or an organ of a person or an animal, a limb including a vein nerve, a head part, a cervix, an abdomen, do. For example, if the human body is a subject to be measured, the object of the light absorber may be a blood vessel containing a large amount of oxyhemoglobin or dioxyhemoglobin or dioxyhemoglobin, or a new blood vessel formed in the vicinity of the tumor. The object of the light absorber may be a plaque of the carotid artery wall or the like. Further, a dye, gold fine particles such as methylene blue (MB), indocyanine green (ICG), or the like may be used as a light absorber. In addition, a light absorber attached to a puncture needle or a puncture needle may be used as an observation target.

Control method of light source and calorific value per unit time

Figs. 4A to 4C are timing charts for explaining the control method of the light source and the calorific power per unit time according to the present embodiment. Fig. Figs. 4A to 4C show respective timings of emission of irradiation light, reception of photoacoustic wave, generation of image data, and display of image data. The vertical axis in the timing chart of "light emission" 4A to 4C, the irradiation light amount assumes a value proportional to the electric power supplied to the light source 111. In addition,

In Fig. 4A, the refresh frequency of the image display is set to 20 [Hz], which enables display to track the normal movement of the hand-held type probe. In Fig. 4A, the refresh frequency of image display coincides with the repetition frequency of light irradiation.

4A, the control unit 153 sets the light amount set value 0.01 [J] in the driver circuit 114 and outputs the light emission timing signal to the driver circuit 114 at 0.05 second intervals . The driver circuit 114 drives the light source 111 in accordance with the light emission timing signal from the control unit 153 and information on the light amount set value.

Next, the receiving section 120 receives the photoacoustic wave caused by the light from the light source 111 at the timing shown in "reception" in Fig. 4A. The arithmetic operation unit 151 performs a reconstruction process on the basis of the signal output from the receiving unit 120 at the timing shown in "Image generation" in Fig. 4A, and generates image data. Then, the control unit 153 transmits the image data to the display unit 160 and causes the display unit 160 to display the image based on the image data. The display unit 160 displays an image based on the image data during the period shown in "Image display" in Fig. 4A.

In the timing chart shown in Fig. 4A, the image 1 is displayed for 0.05 second, and the image 2 is displayed for 0.05 second. The above steps are repeated, and the display of the image based on the new image data is updated every 0.05 seconds. As described above, the calorific power per unit time of the hand-held probe is determined by the amount of light and the repetition frequency of light irradiation. Assuming that the photoelectric conversion efficiency with respect to the supply power is 10 [%] and the irradiation light amount is 0.01 [J], the amount of heat generated per unit time of the light source 111 is 0.09 [J] /0.05)=1.8 [W].

Fig. 4B is a timing chart in which the light amount is different from that in Fig. 4A although it shares the same repetition frequency of light irradiation. In Fig. 4B, the repetition frequency is 20 [Hz] as in Fig. 4A, and light is irradiated at a period of 0.05 sec. Further, since the update of the display image is also performed every 0.05 second, the followability is equivalent to that of Fig. 4A. On the other hand, the irradiation light amount in Fig. 4B is set to 0.005 [J], i.e., half of Fig. 4A. With this setting, the amount of heat generated per unit time of the light source 111 is reduced to 0.9 [W].

4C is a timing chart in which the same amount of light is shared, but the repetition frequency of light irradiation is different from FIG. 4A. The irradiation light amount in FIG. 4C is 0.01 [J] as shown in FIG. 4A. Therefore, the S / N ratio of each of the obtained reconstructed images is equivalent to the reconstructed image obtained in FIG. 4A. On the other hand, the repetition frequency of the light irradiation in Fig. 4C is 10 [Hz], or in other words, the repetition period of the light irradiation is twice as large as that in Fig. 4A. With this setting, the amount of heat generated per unit time of the light source 111 is reduced to 0.9 [W].

As described above, it is known that the calorific power per unit time of the light source 111 which repeats light irradiation can be controlled by the repetition frequency of light irradiation and the irradiation light amount.

Protected mode

The present invention provides a method for optimally controlling two conditions, a repetition frequency and an irradiation light amount, based on the temperature detected by the temperature sensor (200). Specifically, when the temperature detected by the temperature sensor exceeds a permissible value, the computer according to the present invention suppresses the light emission of the light source to prevent the temperature rise of the electronic element inside the probe 180, Prevent destruction. Further, the temperature rise of the housing 181 is suppressed, thereby preventing the patient or the user from feeling uncomfortable.

In the first embodiment of the present invention, first, the user uses the input unit 170 to designate a protection mode for preventing the temperature rise of the probe 180 from a plurality of modes. For example, an icon or the like is displayed on the display unit 160 so that the "normal protection mode", the "following priority protection mode", and the "image quality priority protection mode" can be selected and the mouse 171 or the keyboard 172 May be selected. In addition, in order to reduce the labor of selection every time measurement is performed, a default protection mode may be determined depending on the inspected object, the imaging mode, and the like. In this case, it is preferable that the user can change from the default protection mode using the input unit 170. [ Although the number of protection modes is three in the first embodiment, the number of protection modes is not limited to this, and may be one, two, or four or more.

The "following priority protection mode" is a protection mode in which the refresh frequency of the image display (that is, the repetition frequency of light irradiation) is not lowered. The "image quality first protection mode" is a protection mode in which S / N of each reconstructed image is not deteriorated. "Normal protection mode" is a protection mode that provides a balance between trackability and image quality (S / N). Hereinafter, the operation of each protection mode will be described.

In the "follow-first-priority protection mode", when the temperature of the probe 180 rises, control is performed to decrease the irradiated light amount before lowering the repetition frequency of light irradiation, thereby reducing the amount of heat per unit time of the light source 111 . Alternatively, when the temperature of the probe 180 rises, control is performed to decrease the irradiated light amount to a larger extent than to lower the repetition frequency of the light irradiation, thereby reducing the heat generation amount per unit time of the light source 111. By controlling in this way, when the temperature rise is small, the refresh frequency of the image display (that is, the repetition frequency of light irradiation) does not decrease, and thus a reconstructed image with good followability can be obtained.

In the "image quality first protection mode", when the temperature of the probe 180 rises, control is performed so that the repetition frequency of the light irradiation is lowered before the irradiation light amount is reduced, thereby reducing the heat generation amount per unit time of the light source 111 . Alternatively, when the temperature of the probe 180 rises, control is performed such that the repetition frequency of the light irradiation is lowered more than the amount of reduction of the irradiation light amount, thereby reducing the heat generation amount per unit time of the light source 111. By controlling in this manner, when the temperature rise is small, the irradiated light amount is not reduced, and a reconstructed image with a good S / N can be obtained.

In the " normal protection mode ", control is provided to provide a balance between image quality and follow-up. In other words, when the temperature of the probe 180 rises, control is performed such that both the irradiation light amount and the repetition frequency of the light irradiation are lowered while balancing, thereby reducing the heat generation amount per unit time of the light source 111. For example, if the repetition frequency of the default light irradiation is sufficiently high, the repetition frequency of the light irradiation may be lowered first, and if the default irradiation amount is large, the irradiation light amount may be decreased first. In the " normal protection mode ", the user who observes the reconstructed image controls not to detect deterioration in image quality (S / N) and follow-up. By controlling in this manner, it is possible to suppress the amount of heat per unit time of the light source 111 while reducing both image quality and followability to provide a balance.

The control in the normal protection mode is not limited to one kind of control. For example, the user may be able to specify the ratio at which the light amount control and the repetition frequency control each contribute to the suppression of heat generation. When the ratio is specified, the user can use a UI such as a slide bar displayed on the display unit or a physical knob using a variable resistor or the like.

Control flow

Next, the contents of the control of each protection mode will be described in detail using the flowchart shown in Fig.

Step S100. First, the user designates the protection mode and starts imaging. At this time, the default light irradiation repetition frequency and the default light amount can be used. Also, if a default protected mode is provided, the user does not necessarily have to specify the protected mode.

Step S101. Next, the computer determines whether the temperature detected by the temperature sensor 200 (hereinafter simply referred to as the temperature of the temperature sensor 200) is larger than the threshold value T3 (greater than the third threshold value) Or less. The threshold value T3 is an upper limit value at which light emission of the light source 111 must be stopped immediately when the threshold value is exceeded. In this case, the threshold value T3 is set to 60 占 폚. If it is determined in step S101 that the temperature of the temperature sensor 200 is larger than the threshold value T3, the operation transitions to step S140 to stop the light emission of the light source 111 and stop the acquisition of the reconstructed image . In addition, a message such as "imaging stopped due to probe temperature rise" is displayed on the display unit 160. [ Alternatively, notification in combination with beep sound may be performed (step S141). Subsequently, the imaging is stopped.

Step S102. On the other hand, if it is determined in step 101 that the temperature of the temperature sensor 200 is equal to or lower than the threshold value T3, the operation proceeds to step S102. In step S102, the computer determines whether the temperature of the temperature sensor 200 is equal to or less than the threshold value T1 (a value equal to or less than the first threshold value) or greater than the threshold value T1. The threshold value T1 is set to a temperature at which the heat generation of the light source 111 needs to be suppressed because the temperature of the probe 180 is high to some extent. In this case, the threshold value T1 is set at 40 占 폚. If it is determined in step S102 that the temperature of the temperature sensor 200 is equal to or less than the threshold value T1, the temperature of the probe 180 is sufficiently low and the default light irradiation repetition frequency and default light amount can be maintained without incidence. The operation proceeds to step S104 without changing the repetition frequency and the light amount.

Subsequently, in step S104, the optical pulse is irradiated, the corresponding photoacoustic wave is received, a reconstructed image is generated, and the result is displayed on the display unit 160. [ In S104, the notification unit may be used to notify the user of information indicating what the protected mode is in operation, and information indicating the current light quantity and the repetition frequency. As the notification unit, the display unit 160 may be used, or a sound output apparatus (not shown) may be used.

Step S103. On the other hand, the determination that the temperature of the temperature sensor 200 is higher than the threshold value T1 in step S102 means that the temperature of the probe 180 is high to some extent. Therefore, the process proceeds to the next step S103 to determine which protection mode the current protection mode is.

Steps S110 to S112. If it is determined in step S103 that the "tracking priority protection mode" is being selected, the operation transitions to step S110. In step S110, the control unit reduces the amount of light of the light source 111 to suppress the amount of heat generated per unit time emitted from the light source 111. [

In the next step S111, the computer determines whether the temperature of the temperature sensor 200 is a value equal to or greater than the threshold value T2 (a value equal to or greater than the second threshold value) or smaller than the threshold value T2. The threshold value T2 is selected from the temperature between the threshold values T3 and T1. In this case, the threshold value T2 is set at 50 占 폚. When the temperature of the temperature sensor 200 is lower than the threshold value T2, this means that the temperature reduction effect due to the reduction of the light amount is sufficiently obtained, and thus the operation proceeds to step S104.

On the other hand, if it is determined in step S111 that the temperature of the temperature sensor 200 is equal to or greater than the threshold value T2, this means that a sufficient temperature reduction effect can not be obtained only by decreasing the light amount. For this reason, the operation proceeds to step S112 to lower the repetition frequency of the light irradiation (lengthen the light emission period) in order to limit the amount of heat generated per unit time emitted from the light source 111. [ The repetition frequency of the light irradiation and the irradiation light amount are determined as described above, and the operation proceeds to the next step S104. In step S104, light pulses are irradiated at the determined repetition frequency and light amount, and a photoacoustic signal is received to generate and display a reconstructed image.

The processing in step S112 is not limited to the fall of the repetition frequency. For example, in the follow-first-priority protection mode, control may be performed to reduce the amount of heat generated only by the irradiation light amount reduction processing. Similarly, in step S132 related to the image quality-first protection mode, which will be described later, the heating value may be reduced only by the repetition frequency lowering.

It is necessary to add that the judgment using the threshold value T2 and the threshold value T3 is not essential and a simpler processing flow than the one shown in Fig. 5 may be employed. For example, the computer determines whether the temperature of the temperature sensor 200 is greater than the threshold value T1 or less than the threshold value T1. If the temperature is greater than the threshold value T1, the computer decreases the light amount or the repetition frequency until the threshold value becomes less than T1 , A processing flow may be employed.

The method of determining the repetition frequency of the light irradiation and the irradiation light amount in steps S110 to S112 will be described more specifically based on the graphs shown in Figs. 6A and 6B. 6A is a graph showing the control of the irradiation light amount according to the temperature of the temperature sensor. The abscissa represents the temperature of the temperature sensor, and the ordinate represents the intensity ratio of the light amount irradiated in step S104 to the default light amount (100%). For example, when the default amount of light is 0.01 [J] and the temperature of the temperature sensor is 50 [deg.] C, the light amount is set to 50 [%], that is, 0.005 [J]. Further, at a temperature exceeding 50 캜, the light amount may be maintained as indicated by the solid line, or the light amount may be decreased as indicated by the dotted line (reference character a).

6B is a graph showing the control of the repetition frequency of light irradiation according to the temperature of the temperature sensor. The abscissa represents the temperature of the temperature sensor, and the ordinate represents the ratio of the repetition frequency when the light is irradiated in step S104 to the repetition frequency (100%) of the default light irradiation. For example, when the default repetition frequency is 20 [Hz], if the temperature of the temperature sensor is 60 [deg.] C, the actual repetition frequency decreases to 50%, i.e., 10 [Hz].

6A and 6B, the amount of heat per unit time of the light source 111 can be reduced and the temperature of the probe 180 can be lowered even when the temperature of the temperature sensor is high. In the examples shown in Figs. 6A and 6B, the contribution of the light amount suppression is larger than the contribution of the repetition frequency decreasing with respect to the reduction in the heat generation amount. 6A and 6B, the ratio of the default repetition frequency to the actual repetition frequency is merely an example, and a different value may be used instead.

In the above description, the flow of determination and control based on the threshold values T1, T2, and T3 has been described. In such a flow, the amount of light and the repetition frequency of light irradiation can be easily defined by an equation, so that the capacity of the control program can be reduced. However, the characteristics shown in Figs. 6A and 6B may be retained in the storage unit as the conversion table, and the light amount and the repetition frequency of the light irradiation may be determined with reference to the conversion table based on the temperature.

When a conversion table is used, a conversion table in which the light amount and the repetition frequency are gradually changed as shown in Figs. 7A and 7B may be used. By using the conversion table shown in Figs. 7A and 7B, when the temperature of the probe 180 rises, control is performed so as to reduce the irradiation light amount to a larger extent than the amount at which the repetition frequency of light irradiation is lowered. In other words, with respect to the temperature suppression, the control is performed such that the contribution of the light amount reduction becomes larger than the contribution of the repetition frequency fall. As a result, when the temperature of the probe 180 is high, the heat generation amount per unit time of the light source 111 can be lowered while keeping trackability.

Steps S130 to S132. If it is determined in step S103 that the "image quality priority protection mode" is selected, the operation transitions to step S130. In step S130, the repetition frequency of light irradiation of the light source 111 is lowered (the light emission period is lengthened) in order to limit the amount of heat generated per unit time emitted from the light source 111. [ In the next step S131, it is determined whether the temperature of the temperature sensor 200 is equal to or greater than the threshold value T2. The threshold value T2 is selected from the temperature between the threshold values T3 and T1. In this case, the threshold value T2 is set at 50 占 폚. If the temperature of the temperature sensor 200 is lower than the threshold value T2, this means that the temperature reduction effect is sufficiently obtained by lowering the repetition frequency, so the operation proceeds to step S104.

If it is determined in step S131 that the temperature of the temperature sensor 200 is equal to or higher than the threshold value T2, this means that a sufficient temperature reduction effect can not be obtained only by lowering the repetition frequency. Therefore, the operation proceeds to step S132 to reduce the amount of irradiation light to limit the amount of heat generated per unit time emitted from the light source 111. [ The repetition frequency of the light irradiation and the irradiation light amount are determined as described above, and the operation proceeds to the next step S104. In step S104, light pulses are irradiated at the determined repetition frequency and light amount, and a photoacoustic signal is received to generate and display a reconstructed image.

The method of determining the repetition frequency of the light irradiation and the irradiation light amount in steps S130 to S132 will be described more specifically based on the graphs shown in Figs. 8A and 8B. 8A is a graph showing the control of the irradiation light amount according to the temperature of the temperature sensor. The abscissa represents the temperature of the temperature sensor, and the ordinate represents the intensity ratio of the light amount irradiated in step S104 to the default light amount (100%). For example, when the default amount of light is 0.01 [J] and the temperature of the temperature sensor is 50 [deg.] C, the light amount is set to 100 [%], or 0.01 [J] [%], That is, 0.005 [J].

8B is a graph showing the control of the repetition frequency of light irradiation according to the temperature of the temperature sensor. The abscissa represents the temperature of the temperature sensor, and the ordinate represents the ratio of the repetition frequency when the light is irradiated in step S104 to the repetition frequency (100%) of the default light irradiation. For example, if the default repetition frequency is 20 [Hz], if the temperature of the temperature sensor is 50 [deg.] C, the actual repetition frequency is reduced to 50%, i.e. 10 [Hz]. At a temperature exceeding 50 캜, the repetition frequency may be maintained as indicated by the solid line or the repetition frequency may be decreased as indicated by the dotted line (ref. B).

8A and 8B, the amount of heat per unit time of the light source 111 can be reduced and the temperature of the probe 180 can be lowered even when the temperature of the temperature sensor is high. In the examples shown in Figs. 8A and 8B, the contribution of the repetition frequency fall is larger than the contribution of the light amount suppression in reducing the heat generation amount. The ratio of the default light amount to the actual irradiation light amount in FIGS. 8A and 8B and the ratio of the default repetition frequency to the actual repetition frequency is merely an example, and other values may be used instead.

In the above description, the flow of determination and control based on the threshold values T1, T2, and T3 has been described. In such a flow, the amount of light and the repetition frequency of light irradiation can be easily defined by an equation, so that the capacity of the control program can be reduced. However, the characteristics shown in Figs. 8A and 8B may be held in the storage unit as the conversion table, and the light amount and the repetition frequency of light irradiation may be determined by referring to the conversion table based on the temperature.

When the conversion table is used, a conversion table in which the light quantity and the repetition frequency are gradually changed as shown in Figs. 9A and 9B may be used. 9A and 9B, when the temperature of the probe 180 rises, control is performed so that the repetition frequency of the light irradiation is lowered more than the amount of reducing the irradiation light amount. In other words, with respect to the temperature control, the control is performed such that the contribution of the repetitive frequency fall becomes larger than the contribution of the light amount decrease. As a result, when the temperature of the probe 180 is high, the amount of heat generated per unit time of the light source 111 can be reduced while maintaining the image quality (S / N).

Step S120. If it is determined in step S103 that the "normal protection mode" is selected, the operation transitions to step S120. In step S120, both the repetition frequency of the light irradiation of the light source 111 and the irradiation light amount are reduced in order to limit the amount of heat generated per unit time emitted from the light source 111. [ In the next step S104, light pulses are irradiated at the determined repetition frequency and irradiated light amount, and a photoacoustic signal is received to generate and display a reconstructed image.

The method of determining the repetition frequency of the light irradiation and the irradiation light amount in step S120 will be described more specifically based on the graphs shown in Figs. 10A and 10B. 10A is a graph showing the control of the irradiation light amount according to the temperature of the temperature sensor. The abscissa represents the temperature of the temperature sensor, and the ordinate represents the intensity ratio of the light amount irradiated in step S104 to the default light amount (100%). For example, when the default light amount is 0.01 [J] and the temperature of the temperature sensor is 40 [deg.] C, the light amount is set to 100 [%], that is, 0.01 [ 50 [%], that is, 0.005 [J].

10B is a graph showing the control of the repetition frequency of light irradiation according to the temperature of the temperature sensor. The abscissa represents the temperature of the temperature sensor, and the ordinate represents the ratio of the repetition frequency when the light is irradiated in step S104 to the repetition frequency (100%) of the default light irradiation. For example, if the default frequency is 20 [Hz] and the temperature of the temperature sensor is 40 [deg.] C, the actual repetition frequency is set to 100%, i.e. 20 [Hz] , The actual repetition frequency is set to 50 [%], that is, 10 [Hz].

10A and 10B, the amount of heat per unit time of the light source 111 can be reduced and the temperature can be lowered even when the temperature of the temperature sensor is high. In the examples shown in Figs. 10A and 10B, the contribution of the light amount suppression and the contribution of the repetitive frequency fall are comparable to each other with respect to the reduction of the calorific power. In addition, the ratio of the default irradiation amount to the actual irradiation amount in Figs. 10A and 10B and the ratio of the default repetition frequency to the actual repetition frequency are only examples, and other values may be used instead. In other words, it is not necessary to reduce the image quality (S / N) and follow-up ratio at the same rate if the user can control the image quality (S / N) and followability so as not to detect significant deterioration.

In the above description, the flow of determination and control based on the threshold values T1 and T3 has been described. In such a flow, the irradiation light quantity and the repetition frequency of light irradiation can be easily defined by an equation, so that the capacity of the control program can be reduced. On the other hand, the characteristics shown in Figs. 10A and 10B may be held in the storage unit as a conversion table, and the irradiation amount and the repetition frequency of light irradiation may be determined with reference to the conversion table based on the temperature.

In the " normal protection mode ", when the temperature of the probe 180 is high, the amount of heat generated per unit time of the light source 111 can be lowered while providing a balance between the image quality (S / N) and the followability of each reconstructed image.

As described above, by using the light source control method as in the present embodiment, the temperature rise of the photoacoustic probe including the light source can be appropriately suppressed. Further, since the user can select a desired protection mode, appropriate image display can be performed, for example, even during real-time display, if necessary.

Second Embodiment

In the first embodiment, the control method of the repetition frequency and the irradiation light amount is changed in accordance with the temperature of the probe 180 for each designated protection mode. On the other hand, the second embodiment does not have a protection mode. Instead, in the second embodiment, the repetition frequency and the irradiation light amount are controlled according to the temperature of the probe 180 while referring to the movement (speed) of the probe 180.

The configuration of the apparatus according to the second embodiment is almost the same as that shown in Figs. 1, 2, and 3, so only the difference will be described. The probe 180 according to the second embodiment further includes a velocity sensor serving as a velocity information acquiring section for acquiring velocity when the probe 180 moves. The speed sensor can be realized, for example, by integrating the signal of the acceleration sensor and calculating the speed. However, the speed information acquisition unit may employ any method as long as it can acquire the speed, and is not limited to the one using the acceleration sensor.

Also in the second embodiment, it is the same as in the first embodiment that the repetition frequency of the light irradiation and the irradiation light amount are optimally controlled in accordance with the temperature detected by the temperature sensor 200. [ However, in the second embodiment, instead of the fixed protection mode, it is possible to dynamically determine the repetition frequency and the irradiated light amount (speed) according to the temperature detected by the temperature sensor 200 while referring to the magnitude (speed) .

In general, the resolution of the human eye is reduced for a moving subject. On the other hand, when a moving object is viewed by a human, the update frequency (refresh frequency) of the screen of the display device is low, the continuity of the motion is lowered, and the movement is seen to be fluctuated. In other words, for a moving object, moving image display emphasizing the frequency of image update is preferable to the resolution of the image. The second embodiment dynamically controls the repetition frequency of the light irradiation and the irradiation light amount in accordance with the speed of the probe 180 when the temperature of the probe 180 rises using such a characteristic.

The control method according to the second embodiment will be described with reference to the flowchart shown in Fig.

Step S200. First, imaging starts under instruction from the user.

Step S201. Next, the computer determines whether the temperature of the temperature sensor 200 is greater than or equal to the threshold value T3. In this case, the threshold value T3 is set to 60 占 폚. If the temperature of the temperature sensor 200 is greater than the threshold value T3 in step S201, the operation shifts to step S210, the light emission of the light source 111 is stopped, and the acquisition of the reconstructed image (imaging) is also stopped. Further, a message such as "imaging stopped due to rise of the probe temperature ", etc. is displayed on the display unit 160 (step S211). Subsequently, the imaging is stopped.

Step S202. On the other hand, if it is determined in step S201 that the temperature of the temperature sensor 200 is equal to or lower than the threshold value T3, the operation proceeds to step S202. In step S202, the computer determines whether to change or not to change the default repetition frequency or the default light amount in accordance with the temperature of the temperature sensor 200 while referring to the speed of the probe, and determines a new value when the change is made .

Specifically, when the speed of the probe is relatively slow or when the probe is stopped, the motion of the obtained reconstructed image is also slow, so even if the refresh frequency is low, the feeling of disturbance of the followability is small. Further, when the speed of the probe is relatively slow or when the probe is stopped, the user is paying attention to a specific region of the subject, and it is considered that the user is in a state in which he wants to observe the specific region in detail. Taking this into consideration, when reducing the amount of heat generated per unit time of the light source 111, the refresh frequency may be lowered (the repetition frequency of light irradiation may be lowered) while minimizing the decrease of the irradiation light amount. Thus, it is possible to generate an image having a low refresh frequency but a good image quality (good S / N ratio).

On the other hand, when the speed of the probe is comparatively fast, the motion of the obtained reconstructed image is fast, and if the refresh frequency is not kept high, the feeling of disturbance of follow-up becomes large. In addition, when the obtained reconstructed image moves fast, it is difficult to observe the details of the image, so there is no problem even when the S / N ratio of each reconstructed image is bad. In consideration of this, when the amount of heat generated per unit time of the light source 111 is reduced, the amount of irradiation light may be decreased while minimizing the decrease in the refresh frequency.

Steps S203 and S204. The optical pulse is irradiated with the repetition frequency of the light irradiation and the irradiation light amount determined in S202, and the photoacoustic signal is received to generate and display the reconstructed image. Then, in step S204, it is determined whether or not the image capturing is completed. When the image capturing is not finished, the operation returns to step S201 and the image capturing is repeated.

Next, the method of determining the repetition frequency of the light irradiation and the irradiation light amount in step S202 will be described more specifically based on the graphs shown in Figs. 12A and 12B. 12A is a graph for explaining a method of determining the irradiation light amount in accordance with the temperature of the temperature sensor while referring to the speed of the probe. The abscissa represents the temperature of the temperature sensor, and the ordinate represents the ratio of the amount of light irradiated in step S203 to the default amount of light (100%).

12B is a graph for explaining a method of determining the repetition frequency of light irradiation according to the temperature of the temperature sensor while referring to the speed of the probe. The abscissa represents the temperature of the temperature sensor, and the ordinate represents the ratio of the repetition frequency of the light irradiation when light is irradiated in step S203 to the repetition frequency (100%) of the default light irradiation.

The characteristic curves C0 to C4 in Figs. 12A and 12B are selected in accordance with the speed of the probe 180. Fig. For example, when the speed of the probe 180 is extremely slow or when the probe 180 is stopped, the characteristic curve C0 is selected so as to reduce the heat generation amount per unit time of the light source 111 while maintaining the light amount . On the other hand, when the speed of the probe 180 is high, the characteristic curve C4 is selected so as to reduce the heat generation amount per unit time of the light source 111 while maintaining the refresh frequency. When the probe is at an intermediate speed, the characteristic curves C1 to C3 are selected according to the speed.

In addition, the number of characteristic curves is not limited to five. By using more characteristics, the feeling of discomfort when the characteristics are changed is reduced. The shape of the characteristic curve shown in Figs. 12A and 12B is an example, and other characteristic curves may be used instead. Further, although the term "curve" is used in this description, the curved shape of the graph representing the characteristic is not an essential requirement. Further, instead of using the graph as shown in Figs. 12A and 12B, the control according to the present embodiment can be realized by using a function of the temperature of the sensor and the velocity of the probe as variables.

Features of the characteristics shown in Figs. 12A and 12B are as follows. When the arbitrary velocities V1 and V2 have a relationship represented by V1 < V2, the repetition frequency of the light irradiation at the velocity V1 is set to be smaller than the repetition frequency of the light irradiation at the velocity V2 determined based on the temperature of the temperature sensor The temperature of the probe 180 is controlled more suitably. 12A and 12B show that the control is performed such that the contribution of the amount of light decrease becomes larger than the contribution of the repetitive frequency fall when the probe speed is lowered and the contribution of the repetitive frequency fall becomes smaller , The control is performed such that the contribution of the light amount reduction is greater than that of the light amount reduction.

As described above, according to the second embodiment of the present invention, it is possible to reduce the labor of the user such as designation of the protection mode, and further, to determine the optimum amount of light and the repetition frequency of light irradiation in accordance with the speed of the probe . As a result, when the user views the reconstructed image, it is possible to prevent the temperature rise of the probe 180 without experiencing a sense of deterioration.

Third Embodiment

In the third embodiment, the heating frequency per unit time of the light source 111 is suppressed by controlling the repetition frequency and the irradiation light amount in accordance with the temperature of the probe 180 while referring to the pressing force of the probe 180. [ The configuration of the apparatus according to the third embodiment is almost the same as that shown in Figs. 1, 2, and 3, so only different points will be described. The probe 180 according to the third embodiment further includes a pressure sensor as a pressure information acquiring unit. The pressure sensor is a sensor that detects the force (pressing force) that the contact surface of the receiving portion 120 of the probe 180 presses the object. The difference from the second embodiment of the third embodiment is that the light irradiation is performed dynamically in accordance with the temperature detected by the temperature sensor 200 while referring to the pressing force of the probe 180, And the amount of irradiation light is controlled.

Generally, when a user observes a subject using the probe 180, the more the area to be watched is deeper, the greater the tendency of the user to press the probe 180 strongly on the subject unknowingly. The third embodiment dynamically controls the repetition frequency and the light amount while referring to the pressing force of the probe 180 by using such a characteristic.

The control method according to the third embodiment will be described with reference to the flowchart shown in Fig. 11. The difference between FIG. 11 and FIG. 13 is that step S202 in FIG. 11 is replaced with step S220 in FIG. 13, so description of steps other than step S220 will be omitted. In step S220, the computer determines whether or not to change the default repetition frequency or the default irradiation light amount in accordance with the temperature of the temperature sensor 200 while referring to the pressing force of the probe, and if it is changed, the computer determines a new value .

Specifically, when the pressing force is relatively large, the user often observes the deep portion. Taking this into consideration, the refresh frequency may be lowered (the repetition frequency of light irradiation may be lowered) while minimizing the decrease in the amount of irradiation light when the amount of heat per unit time of the light source 111 is reduced. As a result, an image with a good image quality (good S / N ratio) can be generated although the refresh frequency is low. Light is easily attenuated due to absorption and scattering inside the object, and the light hardly reaches the deep portion. In consideration of this, it is desirable to maintain the irradiation light amount when observing the deep portion.

On the other hand, when the pressing force is relatively small, the user often observes a shallow portion. In consideration of this, when the amount of heat generated per unit time of the light source 111 is reduced, the amount of irradiation light may be reduced while minimizing the decrease in the refresh frequency.

Next, a method of determining the repetition frequency of the light irradiation and the irradiation light amount in step S220 will be described with reference to the graphs shown in Figs. 12A and 12B which were also used in the second embodiment. In the third embodiment, the characteristic curves C0 to C4 in Figs. 12A and 12B are selected in accordance with the pressing force of the probe 180. Fig. For example, when the pressing force of the probe 180 is large, the characteristic curve C0 is selected so as to reduce the heating amount per unit time of the light source 111 while maintaining the light amount. On the other hand, when the pressing force of the probe 180 is small, the characteristic curve C4 is selected so as to reduce the heat generation amount per unit time of the light source 111 while maintaining the refresh frequency. When the pressing force of the probe has an intermediate value, the characteristic curves C1 to C3 are selected in accordance with the value.

In addition, the number of characteristic curves is not limited to five. By using more characteristics, the feeling of discomfort when the characteristics are changed is reduced. The shape of the characteristic curve shown in Figs. 12A and 12B is an example, and other characteristic curves may be used instead. Further, instead of using the graph as shown in Figs. 12A and 12B, the control according to the present embodiment can be realized by using a function in which the temperature of the sensor and the pressing force of the probe are used as variables.

The characteristics shown in Figs. 12A and 12B can be interpreted as follows in the third embodiment. When the arbitrary pressing forces P1 and P2 have a relationship represented by P1 < P2, by controlling the irradiation light amount at the pressing force P2 to be larger than the irradiation light amount at the pressing force P1 determined based on the temperature of the temperature sensor, The temperature rise of the probe 180 is suppressed. 12A and 12B, in the third embodiment, the control is performed such that the contribution of the light amount reduction becomes larger than the contribution of the repetitive frequency fall as the pressing force is lowered when the heat generation of the light source is lowered. The control is performed so that the contribution of the frequency fall becomes larger than the contribution of the light amount reduction.

As described above, according to the third embodiment of the present invention, it is possible to reduce the labor of the user such as the designation of the protection mode, and further improve the repetition frequency of the light irradiation You can decide. As a result, even if the user views the deep portion, it is possible to prevent the temperature rise of the probe 180 without experiencing the S / N deterioration feeling due to the insufficient amount of light.

Fourth Embodiment

In each of the embodiments described above, the irradiation light quantity and the repetition frequency are determined according to the temperature of the temperature sensor. In the fourth embodiment, the irradiation light quantity and the repetition frequency are determined in consideration of the temperature change in addition to the temperature of the temperature sensor. The configuration of the apparatus according to the fourth embodiment is the same as that of the first to third embodiments.

The control method according to the fourth embodiment can be applied in combination to each of the above-described embodiments. Now, the contents of the fourth embodiment will be described using Figs. 6A and 6B. 6A and 6B are graphs for controlling the irradiation light amount and the repetition frequency according to the probe temperature. In the first to third embodiments, although the temperature at a certain time is used, information on a change in temperature (for example, information as to whether the temperature is rising or falling) is not used. On the other hand, in the fourth embodiment, the tendency of the temperature change is also referred to. For example, in the case of 50 占 폚, if the temperature is rising, it is preferable to reduce the heat generation amount per unit time of the light source 111 by a larger amount. In addition, when the temperature is falling from 50 deg. C, it is not necessary to reduce the amount of heat generated per unit time of the light source 111 so much.

Now, a method of realizing the control using the tendency of the temperature change will be described. The computer calculates the difference between the temperature of the temperature sensor at the current time and the temperature of the previous temperature sensor at a time preceding the current time by a specified amount of time. When the temperature is rising, the temperature difference becomes a positive value, and when the temperature is falling, the temperature difference becomes a negative value. The computer multiplies this difference by a coefficient, adds it to the temperature of the temperature sensor, and obtains a new temperature (predicted temperature) at a point of time when a predetermined time has elapsed. Subsequently, the predicted temperature is applied to the abscissa of the graphs shown in Figs. 6A and 6B to determine the amount of light and the repetition frequency of light irradiation. This process can be applied to the graphs of Figs. 6A, 6B to 10A and 10B according to the first embodiment and the graphs of Figs. 12A and 12B according to the second and third embodiments. The processing can also be applied to a case where the light amount and the repetition frequency are obtained by using a function instead of a graph.

According to the fourth embodiment of the present invention, in addition to the effects of the first to third embodiments, it is possible to control the repetition frequency of the light irradiation and the irradiation light amount on the basis of the temperature and temperature variation of the probe 180, The amount of heat generated per unit time of the heat exchanger 111 can be suppressed. In particular, when the temperature tends to rise, the amount of heat generation can be suppressed preferentially. As a result, temperature control of the probe 180 can be performed more appropriately.

Fifth Embodiment

In the present invention, the second embodiment and the third embodiment can be used in combination. The computer according to the fifth embodiment uses both the velocity of the probe acquired by the velocity information acquisition section and the pressure of the probe acquired by the pressure information acquisition section to determine the irradiation light amount and the repetition frequency. In this case, for example, a characteristic curve according to the velocity of the probe and the pressing force of the probe may be selected according to the graph as shown in Fig. In other words, if the velocity is large, a characteristic curve for maintaining the repetition frequency of light irradiation is selected, and if the pressing force is large, a characteristic curve for maintaining the irradiation light amount is selected. Fig. 14 is merely an example, and a feature curve may be selected by another method if the above-described points are satisfied.

Sixth Embodiment

A microcomputer or the like is mounted on the probe 180 itself and delegated to the microcomputer so as to execute at least a part of the function of the control unit 153 so that the temperature rise of the probe due to the heat generation of the light source is based on the temperature of the temperature sensor . In this case, the photoacoustic probe itself functions as a subject information acquiring device. The sixth embodiment is even more preferable because it is possible to carry out a control flow for suppressing an optimum temperature rise for each kind of probe.

Further, in the present invention, the temperature of the probe 180 is prevented from rising by controlling the refresh frequency (repetition frequency of light irradiation) and the irradiation light amount. Therefore, it is preferable to present the information to the user using the display unit 160, the type of the current protection mode, information indicating whether or not the protection mode is in operation, the refresh frequency (repetition frequency of light irradiation) Do. It is also preferable to display these pieces of information together with the obtained reconstructed image. A method of displaying information superimposed on the reconstructed image when the information is displayed together with the reconstructed image or a method of displaying the information in an area around the reconstructed image can be employed.

Seventh Embodiment

In the seventh embodiment, when the amount of light generated by one pulse of light emission is insufficient, pulsed light is emitted a plurality of times, and the obtained photoacoustic signals are averaged to improve S / N, A description will be given of a configuration for calculating a photoacoustic image. In this case, it is preferable to perform a simple average, a moving average, a weighted average, and the like for the addition average. Further, in addition to the addition averaging, any statistical processing for obtaining a signal usable for image reconstruction from a plurality of signals obtained based on a plurality of pulsed light emission may be performed. The seventh embodiment is suitable when an LD, an LED, or the like is used as the light source 111 and the S / N ratio of the photoacoustic signal caused by one pulse of light is not sufficient.

Sixth Embodiment In the previous description, a configuration in which one pulse of light is emitted in order to obtain one reconstructed image is employed. Therefore, the total amount of one pulse of light energy is described as the irradiation light amount. On the other hand, in the seventh embodiment, pulsed light is emitted a plurality of times in order to obtain one reconstructed image, and the obtained photoacoustic signals are additionally averaged. For this reason, in the seventh embodiment, the total amount of light pulsed multiple times in order to obtain one reconstructed image is treated as equivalent to the above-described irradiation light amount. With this handling, the method of controlling the irradiated light amount of each of the above-described embodiments can be applied to this embodiment.

The "light irradiation repetition frequency" in each of the above embodiments is not a frequency defined based on the interval of plural times of pulse light emission in order to perform addition averaging in the present embodiment, And corresponds to a frequency (refresh frequency) based on the frequency.

15A to 15D are timing charts for explaining the control method of the light source 111 according to the seventh embodiment and the calorific value per unit time. 15A to 15D are substantially the same as those in Figs. 4A to 4C, and therefore, overlapping description will be omitted. Figs. 15A to 15D show timings of emission of irradiation light, reception of photoacoustic wave, average of signals, generation of image data, and display of image data. The vertical axis in the timing chart of "light emission" represents the light amount of each pulse light emission in the plural times of pulse light emission. Also, the total amount of light (irradiated light amount according to this embodiment) by plural times of pulse light emission is also described.

4A to 4C differs from Figs. 4A to 4C in that pulse light emission is performed a plurality of times, the obtained photoacoustic signals are additionally averaged, and image reconstruction is performed on the basis of additionally averaged photoacoustic signals. When the pulse light is emitted a plurality of times in this manner, controlling the light amount itself of each pulse light emission during a plurality of pulse light emission makes the circuit more complicated. Therefore, in the seventh embodiment, the light amount of each pulse light emission is fixed during a plurality of pulse light emission, and the light amount (irradiation light amount) is controlled by controlling the number of light emission in a plurality of times of pulse light emission.

According to the control of the amount of light (irradiation light amount) as described above, since the light amount of each pulse light emission during the plurality of pulse light emission is fixed, the light amount distribution (intensity of light amount) Lt; / RTI &gt; Therefore, there is an advantage that it is not necessary to control the gain of the amplifier of the signal collecting unit 140 for each pulse emission.

In Fig. 15A, the refresh frequency of the image display is set to 20 [Hz] which enables display to follow the normal movement of the hand-held type probe.

When the photoacoustic measurement starts in Fig. 15A, the control unit 153 sets the light amount set value 0.01 [J] in the driver circuit 114 at the timing shown in "light emission". The amount of light set at this time is the total amount of light pulsed multiple times. The driver circuit causes the light source 111, such as an LD or an LED, to emit pulses only a number of times of pulse emission corresponding to the light amount set value, based on the light emission timing signal every 0.05 second from the control unit 153. [ For example, when the amount of light per pulse is 0.001 [J], the number of times of light emission is 10 times. The light emission interval is, for example, 2 [mSec].

Subsequently, the receiving section 120 receives the photoacoustic wave generated due to the plurality of pulsed light emission from the light source 111 at the timing indicated by "reception / average" in Fig. 15A, Averages. In addition, the averaging processing need not be performed by the receiving unit 120. [ For example, the calculating unit 151 may perform the averaging process or a circuit for performing the averaging process.

Subsequently, the arithmetic unit 151 performs a reconstruction process based on the additionally averaged photoacoustic signal output from the receiving unit 120 at the timing shown in "Image generation" in Fig. 15A, and generates image data.

Next, the control unit 153 transmits the image data to the display unit 160, and causes the display unit 160 to display an image based on the image data. The display unit 160 displays an image based on the image data during the period shown in "Image display" in Fig. 15A.

In the timing chart shown in Fig. 15A, the image 1 is first displayed for 0.05 seconds, and then the image 2 is displayed for 0.05 second. The above steps are repeated to update the image display based on the new image data every 0.05 seconds.

As described above, the calorific power per unit time of the hand-held probe is determined by the irradiation light amount and the repetition frequency of light irradiation. In the present embodiment, the irradiation light amount is the total light amount by a plurality of times of pulse light emission for obtaining one reconstructed image, and the repetition frequency of light irradiation is a frequency based on a period for acquiring the reconstructed image.

15A, assuming that the photoelectric conversion efficiency with respect to the supplied power is 10 [%] and the irradiation light amount is 0.01 [J] (the light amount of one pulse light emission is 0.001 [J] x 10 times) ) Is 0.009 [J] x 10 x (1 / 0.05) = 1.8 [W].

By controlling the light irradiation, the reception of the photoacoustic wave, and the processing of the received signal as in the present embodiment, even when the light amount of the light source is insufficient, the S / N ratio The image can be reconstructed.

Variation example

Fig. 15B shows a timing chart in which the same repetition frequency of light irradiation is shared, but the irradiation light amount (the number of pulse light emission) is different from Fig. 15A. The repetition frequency in Fig. 15B is 20 [Hz] as shown in Fig. 15A. The light source 111 emits light pulses five times at intervals of 2 [mSec] every 0.05 second. Since the update of the display image can be performed every 0.05 seconds, followability comparable to Fig. 15A can be obtained. On the other hand, the irradiation light amount in Fig. 15B is set to 0.005 [J] (0.001 [J] times of light amount of one pulse light emission), that is, half of Fig. 15A. With this setting, the amount of heat generated per unit time of the light source 111 is reduced to 0.9 [W].

Fig. 15C is a timing chart in which the same irradiation light amount is shared, but the repetition frequency of light irradiation is different from Fig. 15A. The irradiation light amount in Fig. 15C is 0.01 [J] (0.001 [J] x 10 times of light amount of one pulse light emission) as shown in Fig. 15A. Therefore, the S / N ratio of each of the obtained reconstructed images is equivalent to the reconstructed image obtained in Fig. 15A. On the other hand, the repetition frequency of the light irradiation in Fig. 15C is 10 [Hz], that is, a period of 0.1 second, which is twice the cycle of Fig. With this setting, the amount of heat generated per unit time of the light source 111 is reduced to 0.9 [W].

As described above, the calorific value per unit time of the light source 111 is determined by the amount of light irradiation (the frequency based on the period for acquiring the reconstructed image) and the irradiation light amount (one pulse light emission for obtaining one reconstructed image Light amount x number of light emission: proportional to the number of light emission).

In the above description, the amount of light per pulse emission is the same (fixed value: 0.001 [J]) in a plurality of pulsed light emission for obtaining one reconstructed image. However, in the present invention, the amount of light may be different for each pulse emission. In this case as well, the total amount of light by the plural times of pulsed light emission for obtaining one reconstructed image may be treated as the irradiation light amount.

Further, as shown in Fig. 15D, the irradiation light amount (total light amount by pulse light emission a plurality of times) may be changed every cycle of the light irradiation repetition frequency (period for acquiring the reconstructed image) in order to control the heat generation amount. 15D, a light amount of 0.002 [J] is used for reconstructing the image 1 and a light amount of 0.008 [J] is used for reconstructing the image 2. [ In this case, the S / N of the reconstructed image of a certain frame hardly deteriorates corresponding to the irradiated light quantity, and the S / N of the reconstructed image of the other frame deteriorates.

When the control as shown in Fig. 15D is performed, the refresh frequency is not changed, so followability does not deteriorate. In addition, a reconstructed image with little S / N degradation can be obtained (image 2). For this reason, when it is desired to acquire a still image, an image (image 2) of a frame having a large amount of irradiated light may be selected. By performing such control, the temperature rise of the probe 180 can be prevented while balancing the followability and the image quality.

15D, the amount of light for each pulse emission is constant (0.001 [J]). Therefore, as described above, it is possible to fix the gain of the amplifier of the signal collecting unit 140 corresponding to each of a plurality of pulse light emissions. Further, since the photoacoustic signals in each of a plurality of pulsed light emissions are additive-averaged, there is an advantage that reconstruction can be performed under the same conditions regardless of the number of pulse light emission corresponding to each irradiation light amount.

15D, the method of changing the irradiation light amount for every image reconstruction can be applied to a configuration in which one image is reconstructed by one pulse light emission as in the first to sixth embodiments described above . In this case, the light amount may be changed for each pulse emission, and the gain of the amplifier of the signal collecting unit 140 may be varied to correct the change of the photoacoustic signal due to the change of the irradiation light amount.

15A to 15D) and the irradiation light amount (the amount of one pulse light emission for obtaining one reconstructed image times the number of light emissions: the number of light emission times Proportional) is merely an example. But may be appropriately changed in accordance with the characteristics of the system or the image quality desired by the user.

Other Embodiments

Embodiments of the present invention may also be practiced with other computer-readable media including computer-readable instructions stored on a storage medium (e.g., non-volatile computer readable storage medium) For example, by reading and executing the computer-executable instructions from the storage medium to perform one or more functions of the embodiment (s) to perform the functions of the system or device &lt; RTI ID = 0.0 &gt;Lt; RTI ID = 0.0 &gt; computer. &Lt; / RTI &gt; The computer may have one or more of a central processing unit (CPU), a micro processing unit (MPU), or other circuit elements, or may have a separate computer or a network of separate computer processors. The computer-executable instructions may be provided to the computer from, for example, a network or the storage medium. The storage medium may be, for example, a hard disk, a random access memory (RAM), a read only memory (ROM), a storage of a distributed computing system, an optical disk (compact disk (CD), digital versatile disk Disk (BD) ^TM, etc.), a flash memory device, a memory card, and the like.

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

Claims (20)

A probe including a light source and an acoustic wave generated from a subject irradiated with light from the light source;
A temperature information acquisition unit for acquiring a temperature of the probe; And
And a control unit for controlling irradiation of light by the light source according to the temperature.
The method according to claim 1,
Wherein the control unit controls the heat generation from the light source by controlling the electric power supplied to the light source when the temperature exceeds the first threshold value.
3. The method of claim 2,
Wherein the control unit controls at least one of a light amount and a repetition frequency when irradiating the light.
The method of claim 3,
Wherein the control unit controls the irradiation of the light,
A mode in which the contribution of the process for reducing the amount of light to the lowering of heat generation from the light source is larger than the contribution of the process for lowering the repetition frequency; And
A mode in which the contribution of the process of lowering the repetition frequency to the lowering of heat generation from the light source is larger than the contribution of the process of decreasing the light amount,
At least in a plurality of modes.
5. The method of claim 4,
Wherein the control unit performs processing with a higher contribution in the mode during operation among the processing of decreasing the light amount and the processing of decreasing the repetition frequency when the temperature is larger than the first threshold value,
Thereafter, when the temperature is equal to or greater than the second threshold value, which is higher than the first threshold value, the process of decreasing the amount of light and the process of decreasing the repetition frequency Is performed.
5. The method of claim 4,
Wherein the control unit determines the mode according to an input from a user using an input unit or in accordance with a default setting.
The method of claim 3,
And a notification unit for notifying the user of the light amount and the repetition frequency of the light.
The method of claim 3,
Further comprising an arithmetic section for obtaining the characteristic information of the inspected object by using the signal outputted from the receiving section in response to receiving the acoustic wave.
9. The method of claim 8,
And the control section causes the display section to display an image representing the characteristic information for each repetition frequency.
9. The method of claim 8,
Wherein the light source performs one pulse emission every cycle of the repetition frequency,
Wherein the receiving section receives the acoustic wave based on the one-time pulse light emission and outputs a signal,
And the arithmetic unit acquires the characteristic information based on the signal for each cycle of the repetition frequency.
9. The method of claim 8,
Wherein the light source performs pulse light emission a plurality of times for each cycle of the repetition frequency,
Wherein the receiving section receives the acoustic wave for each of the plurality of pulsed light emissions to output a plurality of signals,
Wherein the operation unit acquires the characteristic information based on a signal obtained by adding and averaging the plurality of signals every period of the repetition frequency.
12. The method of claim 11,
Wherein the control unit controls at least one of the number of times of the light emission in the plurality of times of the pulse light emission and the light amount of each of the plurality of times of the pulse light emission in one cycle of the repetition frequency, The total amount of light in the light source is controlled.
The method according to claim 1,
Wherein the temperature information acquiring unit acquires the temperature of the probe housing or the temperature in the vicinity of the light source contained in the probe as the temperature of the probe.
The method of claim 3,
Further comprising a velocity information acquiring section for acquiring velocity of the probe,
Wherein the control unit controls irradiation of light by the light source according to the speed.
15. The method of claim 14,
Wherein the controller performs control such that the contribution of the processing for reducing the light amount becomes larger than the contribution of the processing for decreasing the repetition frequency when the speed of the light source is lowered.
The method of claim 3,
Further comprising a pressure information acquiring section that acquires a pressing force applied when the probe is pressed against the subject,
Wherein the control unit controls irradiation of light by the light source in accordance with the pressing force.
17. The method of claim 16,
Wherein the control section performs control such that the contribution of the process of lowering the repetition frequency becomes larger than the contribution of the process of decreasing the light amount when the heating power of the light source is lowered as the pressing force is larger.
18. The method according to any one of claims 1 to 17,
Wherein the control section determines the contents of the control for lowering the heat generation from the light source based on the predicted temperature obtained from the tendency of the temperature change of the probe.
Light source;
A receiving unit for receiving an acoustic wave generated from a subject irradiated with light from the light source;
A temperature information acquisition unit for acquiring the temperature of the photoacoustic probe; And
And a control unit for controlling irradiation of light by the light source according to the temperature.
Irradiating light onto a subject with a light source included in the probe;
The receiving unit included in the probe receiving an acoustic wave generated from the subject to which the light is irradiated;
The temperature information acquiring unit acquiring the temperature of the probe; And
Wherein the control unit controls the irradiation of the light by the light source in accordance with the temperature.

Images