JP2019187689A - Photoacoustic probe - Google Patents

Abstract

To provide a technique to perform suitable communication between a photoacoustic apparatus main body and a photoacoustic probe which includes a plurality of light sources and a plurality of communication interfaces.SOLUTION: The photoacoustic probe includes: a light source selection unit for selecting one from among a plurality of light source units; a reception unit for receiving a photoacoustic wave generated by a subject projected with light emitted from the light source unit, and then outputting a photoacoustic signal; a reduction processing unit for performing reduction processing on the data amount of the photoacoustic signal; first communication means communicatable at a first communication rate; a communication unit which includes second communication means communicatable at a second higher communication rate and communicates with the photoacoustic apparatus main body to transmit the photoacoustic signal; and a communication means selection unit for selecting communication means between the first and second communication means. The reduction processing unit determines the content of the reduction processing, according to the light source unit selected by the light source selection unit and the communication means selected by the communication means selection unit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photoacoustic probe.

  In recent years, as an imaging technique using light, a photoacoustic apparatus that images the inside of a subject using a photoacoustic effect has been researched and developed. The photoacoustic apparatus forms an absorption coefficient distribution image based on an ultrasonic wave (photoacoustic wave) generated by a photoacoustic effect from a light absorber that has absorbed the energy of light irradiated on the subject. And it is an apparatus which produces | generates the structure image and functional image in a subject from an absorption coefficient distribution image.

In the photoacoustic apparatus, as in the case of the ultrasonic diagnostic apparatus, a device that has the shape of a handheld probe and can easily access the observation site has been researched and developed.
Patent Document 1 discloses an ultrasonic diagnostic apparatus in which communication between an ultrasonic probe and an apparatus main body can be switched between cable communication and wireless communication with improved operability.
Patent Document 2 discloses a wireless ultrasonic probe that uses a data compression circuit to reduce the transmission bandwidth.

Special table 2010-528698 Special table 2002-530142 gazette

  Generally, in a photoacoustic apparatus, a preferable light source varies depending on an observation site. Further, a preferable communication interface varies depending on a communication environment in which observation is performed. Therefore, a photoacoustic probe that has a plurality of light sources and a plurality of communication interfaces and is capable of switching them is desired. However, Patent Literature 1 and Patent Literature 2 assume an ultrasonic diagnostic apparatus, and knowledge about the type of light source in the case of a photoacoustic apparatus and the problem due to the wavelength of the light source and the communication speed between the probe and the apparatus main body. There was no.

  The present invention has been made in view of the above problems. The objective of this invention is providing the technique which performs suitable communication between a photoacoustic apparatus main body and a photoacoustic probe provided with a some light source and a some communication interface.

The present invention employs the following configuration. That is,
A light source selection unit for selecting one of the light source units from a plurality of light source units;
A receiving unit that receives a photoacoustic wave generated by irradiating the subject with light emitted from the light source unit and outputs a photoacoustic signal;
A reduction processing unit for performing processing for reducing the data amount of the photoacoustic signal;
A first communication means capable of communication at a first communication rate and a second communication means capable of communication at a second communication rate higher than the first communication rate, A communication unit that communicates with the apparatus body and transmits the photoacoustic signal;
A communication means selector for selecting a communication means from the first communication means and the second communication means;
With
The reduction processing unit determines the content of the reduction processing according to the light source unit selected by the light source selection unit and the communication unit selected by the communication unit selection unit. It is a probe.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which performs suitable communication between a photoacoustic apparatus main body and a photoacoustic probe provided with a some light source and a some communication interface can be provided.

Block diagram showing the configuration of the photoacoustic apparatus of Example 1 Schematic which shows the structure of the photoacoustic probe of Example 1. FIG. FIG. 1 is a block diagram illustrating a configuration of a computer of the photoacoustic apparatus according to the first embodiment. Flow chart showing the overall processing of the first embodiment Flow chart showing the characteristic processing of the first embodiment The figure explaining the combination of the light source and communication means of Example 1. Timing chart showing contents of reduction processing of embodiment 1

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

  The present invention relates to a technique for detecting acoustic waves propagating from a subject, generating characteristic information inside the subject, and acquiring the characteristic information. Therefore, the present invention can be understood as a subject information acquisition apparatus or a control method thereof, a subject information acquisition method, or a signal processing method. The present invention can also be understood as a display method for generating and displaying an image indicating characteristic information inside a subject. The present invention can also be understood as a program that causes an information processing apparatus including hardware resources such as a CPU and a memory to execute these methods, and a non-transitory storage medium that stores the program and is readable by a computer.

  The subject information acquisition apparatus of the present invention receives an acoustic wave generated in a subject by irradiating the subject with light (electromagnetic waves), and acquires the subject's characteristic information as image data. Includes devices that use. In this case, the characteristic information is characteristic value information corresponding to each of a plurality of positions in the subject, which is generated using a reception signal obtained by receiving a photoacoustic wave.

  The photoacoustic image data according to the present invention is a concept including all image data derived from photoacoustic waves generated by light irradiation. For example, the photoacoustic image data includes at least one subject such as a sound pressure generated by the photoacoustic wave (initial sound pressure), an absorption energy density, an absorption coefficient, and a concentration of a substance constituting the subject (such as oxygen saturation). It is image data representing the spatial distribution of information. Note that photoacoustic image data indicating spectral information such as the concentration of a substance constituting the subject is obtained based on photoacoustic waves generated by light irradiation with a plurality of different wavelengths. The photoacoustic image data indicating the spectral information may be oxygen saturation, a value obtained by weighting the oxygen saturation with an intensity such as an absorption coefficient, a total hemoglobin concentration, an oxyhemoglobin concentration, or a deoxyhemoglobin concentration. Further, the photoacoustic image data indicating 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 subject. 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 in the subject. That is, distribution information such as initial sound pressure distribution, energy absorption density distribution, absorption coefficient distribution, and oxygen saturation distribution.

  The acoustic wave referred to in the present invention is typically an ultrasonic wave and includes an elastic wave called a sound wave or an acoustic wave. An electric signal converted from an acoustic wave by a transducer or the like is also called an acoustic signal. However, the description of ultrasonic waves or acoustic waves in this specification is not intended to limit the wavelength of those elastic waves. An acoustic wave generated by the photoacoustic effect is called a photoacoustic wave or an optical ultrasonic wave. An electrical signal derived from a photoacoustic wave is also called a photoacoustic signal. The distribution data is also called photoacoustic image data or reconstructed image data.

  In addition, the object information acquisition apparatus in the following embodiments is mainly intended for diagnosis of human or animal malignant tumors, vascular diseases, etc., follow-up of chemical treatment, and the like. Therefore, a subject to be examined is a part of a living body, specifically, an examination target of one part of a human or animal (such as breast, organ, circulatory organ, digestive organ, bone, muscle, and fat). The substance to be examined includes hemoglobin, glucose, and water, melanin, collagen, lipid, etc. present in the body. Furthermore, any substance having a characteristic light absorption spectrum, such as a contrast medium such as ICG (Indocyanine Green) administered into the body, may be used. An inanimate object such as a phantom may be used as the subject.

  In the following embodiments, a photoacoustic apparatus that irradiates a subject with pulsed light, receives a photoacoustic wave from the subject, and generates a blood vessel image (structure image) in the subject as the subject information acquisition apparatus. take up. In the following embodiments, a photoacoustic apparatus having a handheld photoacoustic probe is taken up, but the present invention can also be applied to a photoacoustic apparatus that mechanically scans by providing a probe on a stage.

<Examination of light source and communication interface>
In general, the amount of light required for photoacoustic measurement varies depending on the depth of the observation site. For example, when the observation site is a site at a shallow depth from the surface layer such as skin, the amount of light may be relatively small. In such a case, a semiconductor light emitting element such as a semiconductor laser (LD) or a light emitting diode (LED) may be used as the light source. Moreover, as a communication interface, it is good to use the radio | wireless communication interface arrange | positioned inside a probe with a power supply. As a result, a cableless configuration can be realized and the operability of the probe can be improved.

  Here, a light source such as a semiconductor laser or a semiconductor light emitting element can shorten the light emission period as compared with a solid laser or the like. Therefore, when the semiconductor light emitting element emits light at a relatively short light emission interval and a photoacoustic wave is received by the photoacoustic probe, the amount of photoacoustic signal data is larger than that of a solid-state laser or the like, and communication with the photoacoustic apparatus body is performed. The amount also increases. On the other hand, the communication speed of wireless communication is generally slower than that of wired communication (communication rate is low). For this reason, it may be difficult to send all the photoacoustic signals obtained using the semiconductor light emitting element as the light source to the apparatus main body. In such a case, it is necessary to perform a communication amount reduction process such as performing a data amount reduction process on the obtained photoacoustic signal or reducing the data amount itself of the generated photoacoustic signal.

  In addition, when a region deep from the surface layer such as a breast or thigh is a target, a solid-state laser having a relatively large amount of light is desirable as a light source. Here, it is generally necessary for the solid laser to have a longer light emission interval than a semiconductor light emitting element or the like. This is to prevent the irradiation light amount from the solid laser having a relatively large light amount from exceeding the maximum permissible exposure (MPE: Maximum Permissible Exposure). As a result, the light emission period of the solid-state laser becomes longer and the photoacoustic signal generated per time is reduced, so that the communication amount can be reduced as compared with a semiconductor light emitting element or the like. Therefore, when transmitting a photoacoustic signal derived from a solid-state laser, the transmission data reduction rate may be smaller than when transmitting a photoacoustic signal derived from a semiconductor light emitting element.

  Even when the light source is the same, when the communication interface is changed from wireless communication to wired communication (for example, optical communication) with a high communication speed (high communication rate), the reduction rate of the communication amount can be reduced. As described above, it is necessary to optimize the reduction rate of the communication amount according to the combination of the light emission period and the communication interface.

[Example 1]
<Device configuration>
Hereinafter, the configuration of the photoacoustic apparatus according to the present embodiment will be described with reference to the block diagram of FIG. The photoacoustic apparatus 1 includes a photoacoustic apparatus main body 100 and a photoacoustic probe 200. In this embodiment, the subject 2 has two types of skin and breast of the subject's hand, and a semiconductor laser is used when measuring the hand, and a solid-state laser is used when measuring the breast. The first light source unit 3 may be included in the photoacoustic apparatus 1 or may be provided separately from the photoacoustic apparatus 1.

(Photoacoustic device body)
The photoacoustic apparatus main body 100 includes a main body computer 110, a main body interface group, an input unit 180, and a display unit 190. The body-side interface group includes a body-side wireless interface 131, a body-side LAN (Local Area Network) interface 132, and a body-side optical interface 133, and constitutes a body-side communication unit. The main body computer includes a calculation unit 111, a storage unit 112, and a main body control unit 113.

(Main computer)
The main body computer 110 can be configured by a processor, a processing circuit, a memory, and the like. Each block in the computer may be configured by a processing circuit having a physical entity, or may be realized as a functional block by a program module or the like.

  The main body control unit 113 controls each block of the photoacoustic apparatus main body. The main body control unit 113 determines the control conditions of the apparatus based on information set by the user via the input unit 180, and transmits it to the probe side via the communication interface. There are various methods for the type of information to be input and the control conditions. For example, on the main body side, only the type of subject and a desired image quality may be set. In this case, the probe computer selects a light source according to the type of the subject, and selects a communication means having a data transmission capability for realizing the designated image quality. As the image quality, not only the resolution but also the frame rate and the number of colors of the moving image may be designated.

The main body control unit 113 also receives input from the input unit 180, performs display control on the display unit 190, and controls each communication interface.
The memory | storage part 112 preserve | saves the photoacoustic signal received via the communication interface. The calculation unit 111 performs image reconstruction using the photoacoustic signal. The image data reconstructed from the photoacoustic signal may be displayed in real time on the display unit or may be stored in the storage unit.

(Processing cycle from light irradiation to display)
Here, the period of light irradiation (irradiation interval) at the photoacoustic probe, the period of transmission of photoacoustic signals from the photoacoustic probe to the photoacoustic apparatus body (transmission interval), the period of image reconstruction, and the display unit The relationship between image display cycles will be described.

When the communication means has a sufficient data transmission capability, the irradiation interval and the transmission interval can be matched. On the other hand, when the data transmission capability of the communication means per unit time is smaller than the data amount of the photoacoustic signal output within the same time, the reduction processing unit reduces the data amount.
Further, when the computer on the main body side has sufficient computing capability, the period of image reconstruction can be made to coincide with the period of photoacoustic signal transmission. On the other hand, when the computing power of the computer on the main body side is insufficient, it is possible to store the reconstructed image data in the storage unit without displaying the real-time image, or to perform synthesis described later in the reconstruction. I need it.

Furthermore, when the display frame rate of the display unit and the image reconstruction period match, the reconstructed image data may be displayed as it is. Otherwise, the main body computer converts the photoacoustic image data into a display frame rate on the display unit.
Alternatively, composition processing may be performed at the time of image reconstruction, and the period of the reconstruction data may be matched with the display frame rate. The composition is not limited to simple addition, but includes weighted addition, addition average, moving average, and the like.

  Note that the terms “period”, “interval”, and “frame rate” in light irradiation, data transmission, image reconstruction, and image display do not necessarily mean that the repetition time is completely constant. That is, even when repeating at non-constant time intervals, a term such as “period” may be used. For example, even when there is a rest period in a certain cycle, or when the time interval changes within a range where there is no practical problem, these words are used.

(Main body side interface group)
Each interface included in the main body side interface group receives the photoacoustic signal from the corresponding probe side interface. It is preferable to enable bidirectional communication between the probe side and the main body side.

  The main body side wireless interface 131 establishes communication with the probe side wireless interface 231 and receives a photoacoustic signal. For example, a wireless interface conforming to a wireless LAN standard such as Wi-Fi (Wireless Fidelity) is suitable.

  The main body side LAN interface 132 establishes communication with the probe side LAN interface 232 and receives a photoacoustic signal. For example, a LAN interface including a connector for inserting a LAN cable, a conversion circuit for signals transmitted / received via the LAN, and the like is preferable. Alternatively, a LAN interface that conforms to the industrial LAN standard may be used. If the communication is impossible because the LAN cable 132 is not inserted, the main body LAN interface 132 notifies that fact.

  The main body side optical interface 133 establishes communication with the probe side optical interface 233 and receives a photoacoustic signal. For example, an optical communication interface including a connector for inserting an optical fiber and a conversion circuit for a signal transmitted / received via an optical cable is suitable. If the communication is impossible because the optical cable 133 is not inserted or the like, the main body side optical interface 133 notifies that fact.

(Input section)
The input unit 180 receives an instruction input from the user. The main body control unit sends an instruction from the user and a set value from the photoacoustic apparatus main body to the probe via the wireless interface. The set value may include any data necessary for the control on the probe side, such as the light emission cycle, the number of repetitions, the light amount of the light source, and the A / D conversion rate.

(Display section)
The display unit 190 displays the photoacoustic image reconstructed according to the control of the main body control unit 113. If necessary, the obtained photoacoustic image data may be subjected to display imaging processing or GUI graphic synthesis processing. As the display unit, a liquid crystal display, an organic EL display, or the like can be used. The display unit may be integrated with the photoacoustic apparatus main body or may be provided separately. A user such as a doctor or an engineer checks the photoacoustic image on the display unit. The image displayed on the display unit may be stored in a memory in the computer or a data management system connected to the photoacoustic apparatus via a communication network based on a storage instruction from the user or the computer.

((Photoacoustic probe))
The photoacoustic probe 200 includes a receiving unit 210, a signal processing unit 220, a probe-side interface group, a probe-side computer 250, a power supply unit 260, a configuration related to the first light irradiation unit, and a configuration related to the second light irradiation unit. The probe-side interface group includes a probe-side wireless interface 231, a probe-side LAN interface 232, and a probe-side optical interface 233, and constitutes a probe-side communication unit. The probe computer 250 includes a communication means selection unit 251, a light source selection unit 252, a probe control unit 253, and a reduction processing unit 254. As a configuration related to the first light irradiation unit, there are a first light source unit interface 281 and a first light irradiation unit 282. As a configuration related to the second light irradiation unit, there are a second light source unit driver 291, a second light source unit 292, and a second light irradiation unit 293.

(Receiver)
The receiving unit 210 includes a transducer that receives a photoacoustic wave generated from a subject irradiated with light and outputs an electrical signal, and a support that supports the transducer. A plurality of transducers may be arranged side by side on the support. The support may be flat or hemispherical. However, when a handheld photoacoustic probe is used, the configuration is such that the ease of handling of the photoacoustic probe is not impaired. Moreover, the structure which uses a single transducer like a photoacoustic microscope may be sufficient. As the transducer, a transducer using a piezoelectric material, a capacitive transducer, or the like can be used. Examples of the piezoelectric material include a piezoelectric ceramic material such as PZT (lead zirconate titanate) and a polymer piezoelectric film material such as PVDF (polyvinylidene fluoride).

In the space between the receiving unit 210 and the subject, a medium for propagating the photoacoustic wave may be disposed in order to match the acoustic impedance at the interface. Examples of the medium include water, oil, and ultrasonic gel.
The photoacoustic apparatus 1 may include a holding member that holds the subject and stabilizes the shape. As the holding member, a material having high light transmittance and high acoustic wave transmittance (for example, polymethylpentene, polyethylene terephthalate, acrylic, etc.) is preferable.

(Signal processing part)
The signal processing unit 220 processes the reception signal (time-resolved signal) acquired by the reception unit. The amplitude of the received signal represents a value based on the sound pressure received by the transducer at each time. The signal processing unit 220 includes an amplifier that amplifies the analog electric signal output from the reception unit 210 and an A / D converter that converts the analog signal output from the amplifier into a digital signal. The amplifier may be a variable gain amplifier, and the signal processing unit may be configured with an FPGA chip or the like. When the receiving unit 210 includes a plurality of transducers, the signal processing unit 220 may include a plurality of amplifiers corresponding to each transducer.

(Probe computer)
The probe-side computer 250 can be configured with a processor, a processing circuit, a memory, and the like. Each block in the computer may be configured by a processing circuit having a physical entity, or may be realized as a functional block by a program module or the like.

The communication means selection unit 251 selects an appropriate communication means between the photoacoustic apparatus main body and the photoacoustic probe. Each communication means has a different central communication rate. For example, comparing optical communication, LAN communication, and wireless communication, optical communication has the highest communication rate (first communication rate), LAN communication has medium (second communication rate), and wireless communication. Communication is the lowest (third communication rate). The communication means selection unit 251 determines a communication rate according to the amount of information to be transmitted per unit time and the surrounding communication environment, and selects a communication means that can realize the communication rate. Examples of the communication environment include noise and radio wave interference from surrounding electronic devices, weather during outdoor use, deterioration of probes and parts of the apparatus main body, and distance between the probe and the apparatus. The surrounding communication environment is obtained by, for example, transmitting / receiving test data stored in advance in memory between corresponding interfaces and calculating a delay amount, a data reproduction rate, an error ratio, and the like.

  The light source selection unit 252 selects an appropriate light source. In the present embodiment, the first light source unit (solid laser) is selected during breast measurement, and the second light source unit (semiconductor laser) is selected during skin measurement.

  The probe control unit 253 controls the light emission timing using the first light source unit 3 and the first light irradiation unit 282 and the light emission timing using the second light source unit 292 and the second light irradiation unit 293. The probe control unit 253 also controls the conversion rate and conversion timing of A / D conversion and acquires a photoacoustic signal for each light emission of the first and second light source units. The probe control unit 253 also transmits a photoacoustic signal to the photoacoustic apparatus main body via the probe-side interface group. The probe control unit 253 also has a function of a memory controller, and writes a photoacoustic signal in the memory 270 acquired for each light emission of the first and second light source units. When the probe is not a hand-held type and is a mechanical scanning type using a scanning mechanism such as an XY stage, the probe control unit 253 moves the probe along a predetermined path.

  The reduction processing unit 254 performs processing for reducing the data amount of the photoacoustic signal. The reduction processing unit 254 determines the content of the reduction processing according to the type of light source and communication means.

(Power supply part)
The power supply unit 260 is mounted inside the housing (housing) of the photoacoustic probe, and supplies power to each block in the probe. In order to supply large electric power when the light source emits light, a secondary battery such as a nickel metal hydride battery, a lithium ion battery, or a lithium polymer battery with high energy density may be used. In particular, it is preferable to use a rechargeable battery. However, the photoacoustic probe and the photoacoustic apparatus main body or the power supply apparatus may be connected by a power cable (not shown). In this case, although the degree of freedom of the probe operation is reduced, measurement stop due to power shortage can be avoided. Moreover, you may use a power cable and a battery together.

  The photoacoustic probe may include notification means (not shown) for notifying the user of the current communication quality and the combination of the currently selected communication means and light source. In particular, the notification may be performed when the communication quality is deteriorated or when there is a possibility that data transmission that satisfies the selected communication means and communication rate may be impossible. For the notification, any means such as an audio speaker or LED can be used.

(Probe side interface group)
Each interface included in the probe side interface group transmits a photoacoustic signal to a corresponding main body side interface. In addition, it is preferable to enable bidirectional communication between the probe side and the main body side. Thereby, setting data and the like from the photoacoustic apparatus main body can be input to the probe-side computer. In the following embodiments, data that has undergone various data amount reduction processes such as averaging, compression, and thinning is transmitted from the probe-side interface group. However, if possible, the RAW data output from the signal processing unit may be transmitted. In that case, it can be said that the reduction processing of the same amount of data was performed.

  The probe-side wireless interface 231 establishes communication with the main body-side wireless interface 131 and transmits a photoacoustic signal. For example, a wireless interface conforming to a wireless LAN standard such as Wi-Fi is suitable.

  The probe-side LAN interface 232 establishes communication with the main body-side LAN interface 132 and transmits a photoacoustic signal. For example, a LAN interface including a connector for inserting a LAN cable, a conversion circuit for signals transmitted / received via the LAN, and the like is preferable. Alternatively, a LAN interface that conforms to the industrial LAN standard may be used. The probe-side LAN interface 232 notifies that if communication is impossible because the LAN cable is not inserted or the like.

  The probe side optical interface 233 establishes communication with the main body side optical interface 133 and transmits a photoacoustic signal. For example, an optical communication interface including a connector for inserting an optical fiber and a conversion circuit for a signal transmitted / received via an optical cable is suitable. The probe-side optical interface 233 notifies that if communication is impossible because the optical cable is not inserted or the like.

(Configuration of light source and light irradiation unit)
The first light source unit 3 is a solid-state laser device. For example, a Nd: YAG laser, an alexandrite laser, a titanium sapphire laser using an Nd: YAG laser as an excitation source, an OPO (Optical Parametric Oscillators) laser, or the like can be used. In addition, a wavelength tunable laser may be used to acquire a substance concentration such as oxygen saturation as characteristic information. The first light source unit and the photoacoustic probe are connected by an optical member such as an optical fiber, a mirror, a prism, or a lens. The irradiation light is typically pulsed light having a pulse width of 10 ns to 1 μs.

  The first light source unit interface 281 transmits a control signal to the first light source unit in accordance with a command from the computer, receives light from the first light source unit via the optical member, and transmits the light to the first light irradiation unit 282. Output. The first light irradiation unit 282 is an emission end, which processes laser light into a desired shape and irradiates the subject. As described above, since the output of the solid-state laser is large, it is possible to obtain light with a high S / N ratio by reaching the deep part of the subject, but it is necessary to make the irradiation interval between pulses of the pulsed light relatively long. (Typically about several tens of Hz). The light emission interval from the first light irradiation unit is referred to as a first irradiation interval.

  The 2nd light source part 292 arrange | positioned in the housing | casing of a photoacoustic probe is a semiconductor laser. A light emitting diode may be used. Regarding the semiconductor laser, a configuration capable of irradiating light with a plurality of wavelengths is preferable. The second light source unit driver 291 transmits a control signal to the second light source unit 292 in accordance with a command from the probe control unit 254, and causes the subject to irradiate the subject with laser light from the second light irradiation unit 293. The second light irradiation unit 293 is an emission end for irradiating the subject with light in a desired shape. Semiconductor light-emitting elements such as semiconductor lasers and light-emitting diodes have a relatively small amount of light, so that the light irradiation interval (light emission interval) can be made relatively short (typically several hundred MHz). Note that an averaging process may be performed in order to compensate for the shortage of light and improve the S / N ratio. This addition averaging process may also serve as a data amount reduction process. The light emission interval from the second light irradiation unit is referred to as a second irradiation interval. The second irradiation interval is shorter than the first irradiation interval.

In addition, the 1st light irradiation part may serve as the 2nd light irradiation part. The first light source unit interface may also serve as the second light source unit driver. The first light source unit interface 281 detects whether or not the first light source unit is connected to the probe. When the first light source unit is connected to the probe, the light source selection unit uses either the first light source unit or the second light source unit based on a control signal indicating a measurement instruction from the photoacoustic apparatus main body side. Select whether or not.
If the first light source unit is not connected, this is notified to the photoacoustic apparatus main body or to the user via the notification unit.

(Subject)
The subject 2 does not constitute a photoacoustic apparatus, but will be described below. The photoacoustic apparatus can be used for the purpose of diagnosing human or animal malignant tumors, vascular diseases, etc., and observing the progress of chemotherapy. Therefore, the subject 2 is assumed to be a target site for diagnosis such as a living body, specifically breasts of human bodies or animals, each organ, blood vessel network, head, neck, abdomen, extremities including fingers and toes. The For example, if the human body is an object to be measured, oxyhemoglobin or deoxyhemoglobin, a blood vessel containing many of them, or a new blood vessel formed in the vicinity of a tumor may be used as a light absorber. Further, a plaque of the carotid artery wall or the like may be a target of the light absorber. In addition, a dye such as methylene blue (MB) or indocyanine green (ICG), gold fine particles, or a substance introduced from the outside, which is accumulated or chemically modified, may be used as the light absorber. Moreover, it is good also considering the light absorber attached | subjected to the puncture needle and the puncture needle as an observation object. The subject may be an inanimate object such as a phantom or a test object. As described above, here, the skin of the breast and the hand are the subjects.

<Configuration example of photoacoustic probe>
FIG. 2A is a schematic cross-sectional view showing an example of the configuration of the photoacoustic probe, and particularly describes main components related to light irradiation and photoacoustic wave reception. In the inside of the housing 201 of the photoacoustic probe 200, there are roughly arranged a receiving unit 210, a first light source unit interface 281, a first light irradiation unit 282, a second light source unit 292, and a second light irradiation unit 293. Has been. For the sake of simplification, other components such as the second light source driver and the probe computer are omitted. The user can use the photoacoustic probe as a handheld photoacoustic probe by gripping the housing.

  FIG. 2B is an example of the arrangement of the light emitting end and the receiving unit 210 on the receiving surface on the distal end side (side in contact with the subject) of the housing 201. On the receiving surface, the receiving unit 210 has a two-dimensional array structure. Around the receiving unit, there are arranged a plurality of emission ends of a second light irradiation unit for branching light from the second light source unit 292 made of a semiconductor laser and guiding it to the subject. Further, around the second light irradiation unit, a plurality of emission ends of the first light irradiation unit for branching light from the light source unit and guiding the light to the subject are arranged. According to this configuration, light can be irradiated over a wide range. Moreover, you may change the wavelength of irradiated light for every output end. In addition, the structure which guide | induces the light from the light source written in a common light irradiation part may be sufficient.

<Computer configuration example>
FIG. 3A shows a specific configuration example of the main body computer. FIG. 3 (a) shows only the computer and main components related thereto. The main body computer 110 includes a CPU 1101, a GPU 1102, a RAM 1103, and a ROM 1104. A liquid crystal display 1901 that functions as the display unit 190 and a mouse 1801 and a keyboard 1802 that function as the input unit 180 are connected to the main body computer. The main body computer is further connected with a wireless LAN interface 1311 that functions as the main body side wireless interface 131, a wired LAN interface 1321 that functions as the main body side LAN interface 132, and an optical communication interface 1331 that functions as the main body side optical interface 133. Yes. Further, a main body computer may be realized by linking a plurality of information processing apparatuses. In addition, an information processing apparatus installed in a remote place provided by a cloud computing service or the like may be used.

FIG. 3B shows a specific configuration example of the probe-side computer. The probe computer 250 includes a CPU 2501, a RAM 2502, and a ROM 2503. A wireless LAN interface 2311 that functions as the probe-side wireless interface 231, a wired LAN interface 2321 that functions as the probe-side LAN interface 232, and an optical communication interface 2331 that functions as the probe-side optical interface 233 are connected to the probe-side computer. .

<Overall processing flow>
The overall process flow will be described with reference to FIG. In step S101, the photoacoustic apparatus main body receives a photoacoustic measurement instruction input from the user via the input unit. Here, it is assumed that the type of subject (breast or skin) and the desired image quality are specified. The main body computer transmits the input information to the photoacoustic probe using any communication interface for which communication has been established. Note that the probe may have a function of accepting an instruction from the user.

  After the instruction is received by the probe, in step S102, the communication means selection unit confirms the communication quality and the connection state of each communication means. The light source selection unit checks the connection state of each light source. If there is a communication means for which communication has not been established or a light source unit that cannot be used, the information is stored in the memory.

In step S103, the probe-side computer selects a light source and communication means. In addition, the reduction processing unit determines the presence / absence and contents of reduction processing. This process will be described in detail later.
In step S104, the selected light source unit irradiates the subject with light.
In step S105, the receiving unit receives a photoacoustic wave generated from the subject and outputs a photoacoustic signal. Subsequently, the signal processing unit performs amplification processing and digital conversion processing.

In step S106, the probe-side computer determines whether data amount reduction processing is necessary based on the result of S103. If necessary, the process proceeds to step S107, and the reduction processing unit executes the process.
In step S108, the probe-side communication interface corresponding to the communication means selected in S103 transmits a photoacoustic signal to the main body side.
In step S109, the calculation unit of the main body computer reconstructs the received photoacoustic signal to generate a photoacoustic image indicating the characteristic information. Then, the display unit displays the photoacoustic image inside the subject at a predetermined frame rate.

  In the above flow, S101 to S103 are pre-processing sets executed before the start of photoacoustic measurement. In order to cope with the conversion of the communication environment and the status of the apparatus, such pre-processing may be executed periodically.

  S104 to S108 are measurement processing sets related to photoacoustic measurement, and S109 is a generation processing set related to information generation and presentation. In FIG. 4, the measurement process set and the generation process set are executed as a series of processes. Such a series of processes is performed within a predetermined unit time corresponding to one or a predetermined number of times of light irradiation. Furthermore, by continuously performing such a series of processes, the inside of the subject can be observed in real time using a handheld photoacoustic probe. However, even when only the measurement processing set is performed first, the effect of the present invention can be obtained.

<Flow of selection / reduction processing>
The contents of the process in S103 will be described with reference to FIG. Note that these processes are merely examples, and the contents of the processes are not limited as long as the communication means, the light source, and the reduction rate are obtained. Since the reconfiguration process requires hardware with high computing power, it is normally performed on the photoacoustic apparatus main body side. Therefore, the photoacoustic probe transmits a photoacoustic signal to the photoacoustic apparatus body within a unit time defined by the light irradiation interval. At this time, the probe-side computer performs an optimum data amount reduction process according to the selected combination of the light source and the communication means. Examples of the reduction process include averaging, compression, and thinning.

  The relationship between the combination of the light source and communication means and the data amount reduction rate in this flow will be described. In the example of this flow, as a light source, a semiconductor light emitting element (corresponding to the second light source unit) with an irradiation frequency of about several hundred MHz and a solid state laser (corresponding to the first light source unit) with a frequency of about several tens Hz. And are used. In order to simplify the description, there are two types of communication means: LAN and wireless communication. In this example, the wireless communication corresponds to the first communication means, and the communication rate corresponds to the first communication rate. The LAN corresponds to the second communication means, and the communication rate corresponds to the second communication rate. The communication amount (communication rate) per unit time of the second communication rate is larger than the first communication rate. When the communication unit further has an optical communication function, the optical communication can be called a third communication means. The third communication rate of optical communication has a larger communication volume than the second communication rate.

In step S201 in FIG. 5, the light source selection unit selects a light source based on the instruction content received from the main body side. Here, if the subject is a breast, a solid-state laser is selected, and if the subject is skin, a semiconductor light emitting element is selected.
In step S202, the communication means selection unit confirms whether or not the LAN connection between the main body and the probe is established with reference to the result of S102 in FIG. If the LAN connection is not established, the process proceeds to step S203, and wireless communication is selected as the communication means.

  In step S204, the communication means selection unit calculates a basic communication amount per unit time based on the instruction content received from the main body side. The basic communication amount per unit time is the light irradiation period by the light source selected in S201, and the data amount of the photoacoustic signal generated by processing the photoacoustic wave generated by one light irradiation by the signal processing unit. , Based on.

  In step S205, the communication means selection unit compares the basic communication amount with a threshold value Th1. Here, the threshold value Th1 is the maximum value of the communication amount that can be transmitted by wireless communication per unit time. If the basic communication amount is equal to or less than the threshold value Th1, the data transmission capability of wireless communication is sufficient, and the process proceeds to S206 and wireless communication is selected. Thereby, even if the LAN cable is accidentally disconnected during the probe operation, the measurement can be continued without interrupting the data transmission. On the other hand, if the basic communication amount is larger than the threshold Th1, the process proceeds to S207 to select LAN communication.

  After steps S203 and S207, the process proceeds to step S208, and the reduction processing unit determines whether it is necessary to reduce the amount of data communication. In the subsequent process of S203, the basic communication amount per unit time is compared with the threshold value Th1, as in the case of S205. On the other hand, in the subsequent process of S207, the basic communication amount per unit time is compared with the threshold Th2. Here, the threshold Th2 is the maximum value of the traffic that can be transmitted per unit time by LAN communication. Each threshold value may be stored in a memory. The reduction processing unit determines that data reduction is necessary when the selected communication means cannot transmit all the generated photoacoustic signals, and proceeds to S209.

  In S209, the reduction processing unit determines the reduction rate based on the ratio between the threshold and the basic traffic so that as much information as possible can be transmitted. However, considering the possibility that the communication environment will deteriorate during measurement, a reduction rate with some margin may be used. Further, the reduction method is determined according to the content of the user instruction. For example, when the user gives priority to the frame rate, the data amount is compressed for each light irradiation. On the other hand, when the user gives priority to image quality, thinning processing and averaging processing are performed.

  Although the case where there are two types of communication means has been described in the above flow, for example, the same applies to the case where optical communication is added. That is, the communication means may be selected based on the type of light source, apparatus state, instruction content, and the like, and the presence / absence of reduction processing and the reduction rate may be determined.

<Reduction processing>
FIG. 7 is a timing chart showing an example of the data amount reduction method of this embodiment.

  FIG. 7A is a chart when there is no need to reduce the amount of data, and corresponds to the case of S206 in FIG. 5 or the case of S208 = No. Each time the light irradiation unit emits light from the selected light source, the signal processing unit generates a photoacoustic signal from the photoacoustic wave received by the reception unit. And the selected communication means transmits a photoacoustic signal.

  FIG. 7B shows a case where the amount of data is reduced by thinning out transmission data. That is, the photoacoustic signal derived from the even number of irradiations (tb2, tb4,...) Is not transmitted to the main body side. The reduction rate in the case of FIG. 7B is 50%, and the reduction rate can be changed by changing the thinning timing. Moreover, it is preferable to share a thinning pattern in advance between the photoacoustic apparatus main body and the photoacoustic probe. Thereby, even when thinning processing that is not equally spaced is performed on the probe side, the display timing can be adjusted on the main body side to realize smooth real-time display.

  FIG. 7C shows a case where the amount of transmission data is reduced by thinning out the number of times of light irradiation in the first place. That is, a reduction rate of 50% is realized by not performing even-numbered light irradiation. Also by this method, the amount of data communication can be kept within the capability range of the communication means.

(compression)
FIG. 7D shows a case where transmission data is compressed. In this method, since the data amount of each light irradiation is compressed, the data amount can be reduced without lowering the frame rate. As a configuration for performing compression, for example, a configuration in which the photoacoustic probe includes an addition circuit that performs addition processing on the output from the signal processing unit can be employed. Adder circuit reduces the amount of data by adding signals output from multiple adjacent transducers (elements) or adding digital signals output from the A / D converter at a predetermined sampling interval To do. Alternatively, the transducer may simply be thinned out. The data reduction rate can be adjusted by changing the number of transducers added and the thinning rate.

  Moreover, the photoacoustic signal that is the output of each transducer has a high correlation in the time axis direction. Using this relationship, the compression process can also be executed by performing, for example, DPCM (differential pulse code modulation). Further, DPCM may be performed between data of the same time sent for each light emission cycle to compress the data. At this time, irreversible compression may be performed. Further, DPCM may be performed between data at the same time sent for each cycle of the imaging frame rate to compress the data. Also at this time, irreversible compression may be performed. In addition, any known data compression method can be used.

(Averaging)
FIG. 7E shows a case where transmission data is averaged. Here, the data obtained by three times of light irradiation (te1 to te3) are averaged. Thereby, the amount of data communication can be reduced to 1/3. The number of added data is determined according to the required reduction rate. As an addition target, signals derived from the same transducer may be used.

  As described above, by performing the processing of the present embodiment, when the handheld photoacoustic probe and the photoacoustic apparatus main body communicate to transmit and receive data, the types of the communication means and the light source are appropriately determined. The amount of data communication can be reduced as necessary.

(Modification 1)
In the above description, the communication means is selected based on the basic communication amount and the threshold value, and the presence / absence of reduction and the reduction rate are determined. However, the content of the reduction process may be determined more simply based on information unique to the apparatus. FIG. 6A shows the content of the reduction process when the present modification is applied to the same configuration as the flow of FIG. That is, in this modification, the reduction rate is mechanically determined according to the combination of the light source and the communication unit, in other words, according to the light emission cycle of the light source and the communication rate of the communication unit. For example, in the case of a combination of a semiconductor light emitting element having a short light emission interval and wireless communication having a low communication rate, the reduction rate is increased. A specific reduction rate may be determined in advance based on the configuration unique to the apparatus and stored in the memory.

(Modification 2)
FIG. 6B shows the content of the reduction process when optical communication with a higher communication rate is added. When a high-speed optical communication is used and a solid-state laser having a long emission interval is used, the data amount is not reduced. In this case as well, it may be considered that the same reduction processing is performed. Further, even when a semiconductor light emitting element having a short light emission interval is used, the reduction process can be minimized. In the case of FIG. 6B, it may be considered that “wireless communication is the first communication means and LAN is the second communication means”. Further, it may be considered that “wireless communication is the first communication means and optical communication is the second communication means”. Further, it may be considered that “LAN is the first communication means and optical communication is the second communication means”. Alternatively, it may be considered that “wireless communication is the first communication means, LAN is the second communication means, and optical communication is the third communication means”.

  As described above, according to the first and second modified examples, the processing at the time of data transmission can be easily determined. The content of the reduction process in FIG. 6 is an example, and the reduction method and the reduction rate may be changed according to parameters such as the light emission period of each light source, the data transmission capability of each communication means, and the content of instructions from the user. Absent. Further, it is preferable that the reduction method and the reduction rate corresponding to each parameter are stored in the memory in advance.

  In the above embodiment, the semiconductor light emitting element and the solid-state laser are used as the light source, but the present invention can be applied regardless of the type and combination of the light sources as long as the light emission periods are different. In the above embodiment, optical communication, LAN, and radio are used as communication means. However, the present invention can be applied to any communication means of any type and combination as long as the communication rates are different. As described above, according to the present invention, it is possible to optimize the amount of a photoacoustic reception signal sent from the photoacoustic probe to the apparatus main body according to the combination of the light emission period and the communication interface.

(Other examples)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  200: photoacoustic probe, 252: light source selection unit, 282: first light irradiation unit, 293: second light irradiation unit, 210: reception unit, 254: reduction processing unit, 231: probe-side wireless interface, 232: Probe side LAN interface, 233: Probe side optical interface

Claims (10)

A light source selection unit for selecting one of the light source units from a plurality of light source units;
A receiving unit that receives a photoacoustic wave generated by irradiating the subject with light emitted from the light source unit and outputs a photoacoustic signal;
A reduction processing unit for performing processing for reducing the data amount of the photoacoustic signal;
A first communication means capable of communication at a first communication rate and a second communication means capable of communication at a second communication rate higher than the first communication rate, A communication unit that communicates with the apparatus body and transmits the photoacoustic signal;
A communication means selector for selecting a communication means from the first communication means and the second communication means;
With
The reduction processing unit determines the content of the reduction processing according to the light source unit selected by the light source selection unit and the communication unit selected by the communication unit selection unit. probe. The photoacoustic probe according to claim 1, wherein the reduction processing unit increases the reduction rate of the reduction processing as the communication rate of the communication unit is low. The light source unit includes a first light source unit that irradiates light at a first irradiation interval, and a second light source unit that irradiates light at a second irradiation interval shorter than the first irradiation interval,
The photoacoustic probe according to claim 1, wherein the reduction processing unit increases the reduction rate of the reduction processing as the light irradiation interval is shorter. The photoacoustic probe according to claim 3, wherein the first light source unit is a solid-state laser, and the second light source unit is a semiconductor light emitting element. The reduction processing unit is based on a communication amount per unit time of the first communication unit and a data amount of the photoacoustic signal generated in the unit time due to light irradiation from the selected light source unit. 5. The photoacoustic probe according to claim 1, wherein the content of the reduction process is determined. The photoacoustic according to any one of claims 1 to 5, wherein the content of the reduction processing includes at least one of averaging, compression, and thinning for the photoacoustic signal. probe. The photoacoustic apparatus body includes an input unit for inputting an instruction from a user,
The photoacoustic probe according to claim 1, wherein the reduction processing unit determines the content of the reduction processing according to the content of the instruction. When the instruction gives priority to a frame rate, the reduction processing unit compresses the photoacoustic signal, and when the instruction gives priority to image quality, the reduction processing unit takes the photoacoustic signal. The photoacoustic probe according to claim 7, wherein averaging or thinning is performed on the optical signal. 9. The combination of the first communication unit and the second communication unit is any one of wireless communication and LAN, wireless communication and optical communication, and LAN and optical communication. The photoacoustic probe of any one of Claims. 9. The communication device according to claim 1, wherein the communication unit further includes third communication means capable of performing communication at a third communication rate that is higher than the second communication rate. The photoacoustic probe according to item.

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