JP2020096750A - Photoacoustic imaging apparatus, control method and program - Google Patents

Abstract

To quantitatively evaluate a measurement result in a photoacoustic method.SOLUTION: A photoacoustic imaging apparatus according to an embodiment includes a light irradiation part, a detection part, an image generation part and a control part. The light irradiation part irradiates the light. The detection part detects a photoacoustic wave generated from a subject with the absorption of the light. The image generation part generates a photoacoustic image having a pixel value for each pixel on the basis of a signal obtained by the detection part. The control part controls the irradiation direction and the amount of light of the light irradiation part so that the amount of light irradiated from the light irradiation part into a living body becomes a predetermined standard amount of light.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to a photoacoustic imaging apparatus, a control method, and a program.

A light that obtains a tomographic image of a living body by receiving light photoacoustic waves (also called photoultrasonic waves) generated by a light absorber inside the living body by irradiating the living body as a subject with light. Acoustic imaging devices have been proposed. For example, hemoglobin contained in red blood cells is used as a light absorber, so that the distribution of fine blood vessels can be grasped and used for diagnosis of the state of new blood vessels in inflammatory diseases such as rheumatism.

However, conventionally, the light irradiation to the subject is performed by a laser having a strong directivity, and the light irradiation is performed by the fixed light irradiation unit. The intensity of the received photoacoustic wave did not accurately reflect the concentration or amount of the light absorber. In addition, it was difficult to quantitatively evaluate the measurement results.

International Publication No. 2016/147706

The problem to be solved by the present invention is to enable quantitative evaluation of measurement results by photoacoustic.

The photoacoustic imaging apparatus according to the embodiment includes a light irradiation unit, a detection unit, an image generation unit, and a control unit. The light irradiation unit irradiates light. The detection unit detects a photoacoustic wave generated from the subject by absorbing the light. The image generation unit generates a photoacoustic image having a pixel value for each pixel based on the signal obtained by the detection unit. The control unit controls the irradiation direction and the amount of light of the light irradiation unit so that the amount of light irradiated from the light irradiation unit into the living body becomes a predetermined reference light amount.

FIG. 1 is a diagram illustrating a configuration example of a photoacoustic imaging apparatus according to an embodiment. FIG. 2 is a diagram showing a configuration example of the probe. FIG. 3 is a diagram (1) showing a configuration example of the light irradiation section in the probe. FIG. 4 is a diagram (2) showing a configuration example of the light irradiation section in the probe. FIG. 5 is a diagram (3) showing a configuration example of the light irradiation section in the probe. FIG. 6A is a diagram (1) illustrating an arrangement example of the light emitting units when the irradiation direction is switched nonmechanically. FIG. 6B is a diagram (1) showing an example of the shape of the irradiation surface. FIG. 7A is a diagram (2) showing an arrangement example of the light emitting units in the case of non-mechanically switching the irradiation direction. FIG. 7B is a diagram (2) showing an example of the shape of the irradiation surface. FIG. 8A is a diagram (3) illustrating an arrangement example of the light emitting units in the case of non-mechanically switching the irradiation direction. FIG. 8B is a diagram (3) showing an example of the shape of the irradiation surface. FIG. 9 is a flowchart (1) showing a processing example of the embodiment. FIG. 10 is a flowchart (2) showing a processing example of the embodiment. FIG. 11 is a diagram showing a state of measuring the attenuation due to the dye under the skin of the subject. FIG. 12 is a flowchart (3) showing a processing example of the embodiment. FIG. 13A is a diagram (1) illustrating an example of the control of the irradiation direction according to the depth. FIG. 13B is a diagram (2) showing an example of the control of the irradiation direction according to the depth. FIG. 13C is a diagram (3) showing an example of control of the irradiation direction according to the depth. FIG. 14 is a diagram showing an example of a photoacoustic image when a wire phantom is used as the subject. FIG. 15 is a flowchart (4) showing a processing example of the embodiment. FIG. 16 is a flowchart (5) showing a processing example of the embodiment. FIG. 17 is a diagram showing how the thickness of each layer of the subject is measured. FIG. 18 is a flowchart (6) showing a processing example of the embodiment. FIG. 19 is a diagram showing an example of selecting a photoacoustic wave using time information according to the thickness of. FIG. 20 is a flowchart (7) showing a processing example of the embodiment. FIG. 21 is a diagram showing an example of the data structure of the measurement result. FIG. 22 is a flowchart (8) showing a processing example of the embodiment.

Embodiments of a photoacoustic imaging apparatus, a control method, and a program will be described below with reference to the drawings. The embodiment is not limited to the following contents. Moreover, the content described in one embodiment or the modification is similarly applied to other embodiments or the modification in principle.

(Overall structure)
FIG. 1 is a diagram showing a configuration example of a photoacoustic imaging apparatus 1 according to an embodiment. In FIG. 1, the photoacoustic imaging apparatus 1 has a device body 100, a probe 101, an input interface 104, and a display 105. The probe 101 has a light irradiation unit 102 and a detection unit 103. The light irradiation unit 102 is electrically or optically connected to the apparatus main body 100. The detection unit 103, the input interface 104, and the display 105 are electrically connected to the device body 100. The subject P such as a living body with which the probe 101 is in contact is not included in the configuration of the photoacoustic imaging apparatus 1.

The light irradiation unit 102 irradiates the subject P with light (pulse light). The light irradiator 102 has an internal light source such as a laser diode or the like, and does not have an internal light source, and an optical fiber such as an optical fiber or a lens for receiving light from the light source 110 of the apparatus body 100. It may have a system (light propagation member). Further, the light irradiation unit 102 has a mechanism for mechanically or non-mechanically changing the irradiation direction of light with respect to the subject P. Further, the light irradiation unit 102 is controlled in light amount according to the depth measured by the subject P. Details will be described later.

The pulsed light emitted from the light irradiation unit 102 propagates/diffuses in the subject P and is absorbed by the light absorber existing in the subject P. The light absorber absorbs the energy of the pulsed light of each wavelength and generates a photoacoustic wave (optical ultrasonic wave). Examples of the light absorber include substances such as hemoglobin and glucose (blood sugar) contained in the living body. The light absorber is not limited to the above substances, and any substance capable of absorbing the energy of pulsed light can be applied. For example, melanin present on the body surface is also included in the light absorber. In addition to the in-vivo substances, for example, dyes such as methylene blue and indocyanine green, fine gold particles, and substances (or drugs) obtained by accumulating or chemically modifying them are also administered to the subject P. It can be used as a light absorber. Each light absorber absorbs energy of pulsed light having a specific wavelength and generates a photoacoustic wave, respectively.

The detection unit 103 receives a photoacoustic wave generated inside the subject P and propagating to the surface. The detection unit 103 has a single or a plurality of vibrators (piezoelectric vibrators). The detection unit 103 may include a preamplifier and an A/D (Analog/Digital) converter. The preamplifier amplifies the output signal of the vibrator. The A/D converter A/D converts the photoacoustic wave (including normal ultrasonic waves) amplified by the preamplifier, and outputs a digital electric signal. The detection unit 103 is used not only for receiving ultrasonic waves but also for transmitting (generating) ultrasonic waves.

When the detection unit 103 has a single transducer, the probe 101 moves on the subject P for scanning so as to cover a predetermined measurement range of the subject P. This movement may be performed mechanically or manually. The relative position of the probe 101 with respect to the subject P is grasped during movement. When the detection unit 103 has a plurality of transducers, the transducers are arranged one-dimensionally, and when the two-dimensional range is measured, the probe 101 is arranged in a direction orthogonal to the arrangement direction of the transducers. Is moved. In the case of a two-dimensionally arranged transducer, the range covered by a plurality of transducers can be measured without moving the probe 101. Even in the case of a two-dimensionally arranged oscillator, the measurement range may be expanded by moving the probe 101.

The input interface 104 corresponds to a mouse, keyboard, buttons, panel switch, touch command screen, foot switch, trackball, joystick, and the like. For example, the input interface 104 receives various setting requests from the operator of the photoacoustic imaging apparatus 1, and transfers the received various setting requests to the apparatus main body 100.

The display 105 displays a GUI (Graphical User Interface) for an operator of the photoacoustic imaging apparatus 1 to input various setting requests using the input interface 104, and image data and diagnostics generated in the apparatus main body 100. Display the result screen, etc.

The device body 100 is a device that controls light irradiation from the light irradiation unit 102 of the probe 101, and generates a photoacoustic image and diagnoses based on the photoacoustic wave received by the detection unit 103. The device body 100 includes a light source 110, a reception circuit 120, a signal processing circuit 130, an image generation circuit 140, a storage circuit 150, a processing circuit 160, an irradiation direction control circuit 170, a light amount control circuit 180, and a transmission. And a circuit 190. When the light source is provided on the light irradiation unit 102 side of the probe 101, the light source 110 is unnecessary. The light source 110, the reception circuit 120, the signal processing circuit 130, the image generation circuit 140, the storage circuit 150, the processing circuit 160, the irradiation direction control circuit 170, the light amount control circuit 180, and the transmission circuit 190 are communicably connected to each other.

The light source 110 emits light (pulse light) having a preset wavelength. For example, the light source 110 is a laser light source that generates high-power light. Examples of laser light sources include solid-state lasers, gas lasers, dye lasers, semiconductor lasers, and the like. As the light source 110, a light source capable of emitting light having an arbitrary wavelength can be appropriately used depending on the type of the light absorber used. For example, distinguishing between arteries and veins by switching the wavelength of irradiation light according to the absorption wavelength of oxygenated hemoglobin in arteries and the absorption wavelength of deoxygenated hemoglobin in veins You can Further, the light source 110 can adjust the light irradiation timing, the pulse width, the intensity, and the like under the control of the processing circuit 160 and the light amount control circuit 180 described later.

It is preferable that the light source 110 has a strong output and can continuously change the wavelength, but it may be configured by a plurality of single-wavelength lasers having different wavelengths. Further, the light source 110 is not limited to the laser light source, and may be configured by a light emitting diode, a flash lamp, or the like. Further, the light source 110 may be provided, for example, in a separate housing installed outside the apparatus main body 100, or may be provided inside the light irradiation unit 102 as described above.

The irradiation direction control circuit 170 controls the irradiation direction of the light irradiation unit 102 of the probe 101 with respect to the subject P. When the light irradiation unit 102 is provided with a mechanical drive unit that changes the irradiation direction, the irradiation direction control circuit 170 outputs a control signal to the drive unit. Further, when a signal indicating the state such as the irradiation direction is output from the drive unit of the light irradiation unit 102, the irradiation direction control circuit 170 inputs the signal and outputs a control signal according to the state. When the light irradiation unit 102 is not provided with a mechanical drive unit that changes the irradiation direction and the irradiation direction is changed by switching the plurality of light emitting units, the irradiation direction control circuit 170 switches the plurality of light emitting units. A control signal is output to the switching unit.

The light amount control circuit 180 controls the light amount of the light irradiation unit 102 of the probe 101. When a light source is built in the light irradiation unit 102, the light amount control circuit 180 controls the power supplied to the light source of the light irradiation unit 102 or outputs a light amount control signal to the light source. When the light irradiator 102 does not include a light source and the light source 110 on the apparatus main body 100 side is used, the light amount control circuit 180 controls power supplied to the light source 110 or outputs a light amount control signal to the light source 110. To do.

The reception circuit 120 receives a detection signal from the detection unit 103 of the probe 101. When the detection unit 103 has a preamplifier, an A/D converter, etc., the reception circuit 120 receives a digital signal from the detection unit 103. When the detection unit 103 does not have a preamplifier, an A/D converter, etc., the reception circuit 120 has a preamplifier, an A/D converter, etc., and receives digital reception data from the analog electric signal output from the detection unit 103. To generate. The preamplifier amplifies the output signal of the detection unit 103. The A/D converter A/D converts the photoacoustic wave amplified by the preamplifier and outputs a digital electric signal. As described above, the preamplifier and the A/D converter may be provided on the detector 103 side. In that case, the reception circuit 120 serves as an input interface that connects the detection unit 103 and the apparatus main body 100.

The transmission circuit 190 supplies a drive signal for ultrasonic wave transmission to the detection unit 103 of the probe 101. In the processing example described later, ultrasonic waves are transmitted from the detection unit 103 to the subject P, the reflected waves from the boundaries of the layers forming the skin of the subject P are received by the same detection unit 103, and the time of the reflected waves is It is used to measure the thickness of each layer from the information.

The signal processing circuit 130 reconstructs a photoacoustic image using the light irradiation position by the probe 101 and the reception data from the detection unit 103 by the reception circuit 120, and thereby distribution data of characteristic values in the subject P is obtained. To generate. For example, one-dimensional or two-dimensional distribution data of characteristic values can be obtained from the light irradiation position sequentially changed one-dimensionally or two-dimensionally and the reception level of the photoacoustic wave. In addition, by associating the depth corresponding to the time from the light irradiation to the reception of the photoacoustic wave, the distribution data with the depth dimension added can be obtained. Note that the signal processing circuit 130 may be programmatically executed in the processing circuit 160 or a similar processing circuit.

The image generation circuit 140 generates image data from the distribution data generated by the signal processing circuit 130. For example, the image generation circuit 140 generates image data in which the intensity of the photoacoustic wave is represented by brightness from the distribution data generated by the signal processing circuit 130. As the image data, there is a photoacoustic image having a pixel value for each pixel. The image generation circuit 140 may be programmatically executed in the processing circuit 160 or a similar processing circuit.

Further, the image generation circuit 140 can execute various kinds of image processing on the image data. For example, the image generation circuit 140 executes various kinds of image processing such as smoothing processing and edge enhancement processing according to the operator's request. The image generation circuit 140 also attaches incidental information (character information of various parameters, scale, body mark, etc.) to the image data, and stores it in the storage circuit 150.

The storage circuit 150 stores various programs such as a control program for performing scan processing, various image processing, and display processing, diagnostic information (for example, patient ID, doctor's finding, etc.), diagnostic protocol, various body marks, and the like. Remember. Further, the storage circuit 150 stores the image data generated by the image generation circuit 140 together with the supplementary information. Further, the data stored in the storage circuit 150 can be transferred to an external device via a communication interface (not shown).

The processing circuit 160 controls the entire processing of the photoacoustic imaging apparatus 1. For example, the processing circuit 160 is based on various setting requests input by the operator via the input interface 104, various control programs and various data read from the storage circuit 150, and the light source 110, the receiving circuit 120, and the signal processing circuit. 130, the image generation circuit 140, the irradiation direction control circuit 170, the light amount control circuit 180, and the transmission circuit 190 are controlled. Further, the processing circuit 160 causes the display 105 to display the image data and the diagnostic result stored in the storage circuit 150. The processing circuit 160, the irradiation direction control circuit 170, and the light amount control circuit 180 are examples of a control unit.

Further, the processing circuit 160 executes a prescan control function 161, a main scan control function 162, a diagnostic function 163, and a browsing function 164. Here, for example, the respective processing functions executed by the pre-scan control function 161, the main scan control function 162, the diagnostic function 163, and the browsing function 164, which are the constituent elements of the processing circuit 160, are realized in the form of a program executable by a computer. It is recorded in the storage device (for example, the storage circuit 150) of the acoustic imaging apparatus 1. The processing circuit 160 is a processor that realizes a function corresponding to each program by reading each program from the storage device and executing the program. In other words, the processing circuit 160 in a state where each program is read out has each function shown in the processing circuit 160.

The pre-scan control function 161 controls the processing related to the pre-scan prior to the main scan, and corrects the differences between races and individuals that do not affect the disease. The main scan control function 162 controls the process related to the main scan and acquires a photoacoustic image having a pixel value for each pixel. The diagnosis function 163 is for diagnosing a disease from the photoacoustic image acquired by the main scan or its characteristic data. The browsing function 164 supports browsing of the photoacoustic image acquired by the main scan or its characteristic data. Details of each will be described later.

The word "processor" used in the above description means, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an application-specific integrated circuit (ASIC), a programmable logic device (for example, It means a circuit such as a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA). The processor realizes the function by reading and executing the program stored in the storage circuit 150. Instead of storing the program in the storage circuit 150, the program may be directly incorporated in the circuit of the processor. In this case, the processor realizes the function by reading and executing the program incorporated in the circuit. It should be noted that each processor of the present embodiment is not limited to the case where each processor is configured as a single circuit, and a plurality of independent circuits may be combined to configure one processor to realize its function. Good. Further, a plurality of constituent elements in each drawing may be integrated into one processor to realize its function.

Further, each constituent element of each illustrated device is functionally conceptual, and does not necessarily have to be physically configured as illustrated. That is, the specific form of distribution/integration of each device is not limited to the one shown in the figure, and all or part of the device may be functionally or physically distributed/arranged in arbitrary units according to various loads and usage conditions. It can be integrated and configured. Furthermore, each processing function performed by each device may be implemented entirely or in part by a CPU and a program that is analyzed and executed by the CPU, or may be implemented as hardware by a wired logic.

Further, of the processes described in the above embodiments, all or part of the processes described as being automatically performed may be manually performed, or the processes described as being manually performed. All or part of the above can be automatically performed by a known method. In addition, the processing procedures, control procedures, specific names, and information including various data and parameters shown in the above-mentioned documents and drawings can be arbitrarily changed unless otherwise specified.

(More detailed configuration of probe)
FIG. 2 is a diagram showing a configuration example of the probe 101. In FIG. 2, the probe 101 is provided with, for example, two light irradiation units 102 with a detection unit 103 sandwiched in a housing 101a having a bottom on the upper side of the drawing and an opening on the lower side of the drawing. The number of light irradiation units 102 may be one or more. A film 101c is provided on the side of the casing 101a that contacts the subject P, a liquid 101b is placed in the space inside the casing 101a, and the subject P side of the light irradiation unit 102 and the detector 103 is immersed in the liquid 101b. It is like this.

FIG. 3 is a diagram showing a configuration example of the light irradiation unit 102 in the probe 101, which is an example in which the light irradiation direction is mechanically changed. In FIG. 3, the light irradiation units 102 on both sides of the detection unit 103 include a light emitting unit 102a and a driving unit 102b that moves the light emitting unit 102a itself. The light emitting portion 102a may be a light source such as a laser diode or an end portion such as an optical fiber that guides light from the light source 110 in the apparatus body 100.

FIG. 4 is a diagram showing another configuration example of the light irradiation unit 102 in the probe 101, which is an example in which the light irradiation direction is mechanically changed. In FIG. 4, the light irradiation units 102 on both sides of the detection unit 103 include a light emission unit 102a and a polarization unit 102c that polarizes the light emitted from the light emission unit 102a and the polarization direction is mechanically controllable. Is equipped with. More specifically, the polarization unit 102c includes a polarization lens and a drive unit that moves the arrangement of the polarization lens. The light emitting portion 102a may be a light source such as a laser diode or an end portion such as an optical fiber that guides light from the light source 110 in the apparatus body 100. The polarization unit 102c has an advantage that it can be made smaller than the driving unit 102b shown in FIG.

FIG. 5 is a diagram showing another configuration example of the light irradiation unit 102 in the probe 101, which is an example in which the irradiation direction of light is changed non-mechanically (electrically or optically). In FIG. 5, the light irradiation units 102 on both sides of the detection unit 103 are provided with three light emission units 102a1, 102a2, and 102a3 in the illustrated example, and these light emission units 102a1, 102a2, and 102a3 are the switching units 102d. Are summarized by. The light emitting portions 102a1, 102a2, and 102a3 include a light source such as a laser diode and an end portion such as an optical fiber that guides light from the light source 110 in the apparatus body 100. When the light emitting units 102a1, 102a2, 102a3 are light sources such as laser diodes, the switching unit 102d is an electrical changeover switch. When the light emitting portions 102a1, 102a2, 102a3 are end portions of an optical fiber or the like that guides light from the light source 110 in the apparatus body 100, the switching portion 102d is an optical path switch. The light irradiation unit 102 of FIG. 5 has an advantage that it can be configured smaller than the light irradiation unit 102 shown in FIG. 3, has higher resistance to impact, and can shorten the time required to change the irradiation direction.

FIG. 6A is a diagram showing an arrangement example of the light emitting units 102a1 to 102a3 in the case of non-mechanically switching the irradiation direction (FIG. 5), and is a diagram seen from above or below in FIG. In FIG. 6A, the light irradiation units 102 are provided on both sides of the detection unit 103, and the light emission units 102a1, 102a2, and 102a3 of the respective light irradiation units 102 are connected to the detection unit 103 along the surface contacting the subject. On the other hand, they are arranged in a one-dimensional (straight line) pattern in a radial pattern. FIG. 6B is a diagram showing an example of the shape of the irradiation surface in the case of the configuration of FIG. 6A, in which the light beams from the light irradiation units 102 on both sides of the detection unit 103 are overlapped.

FIG. 7A is a diagram showing another arrangement example of the light emitting units 102a1 to 102a3 when the irradiation direction is switched non-mechanically (FIG. 5), and is a diagram seen from above or below in FIG. In FIG. 7A, a light irradiation unit 102 is provided on both sides of the detection unit 103 and in a direction orthogonal to the detection unit 103, and the light emission units 102a1, 102a2, and 102a3 of the respective light irradiation units 102 are provided on the surface contacting the subject. Along the radial direction with respect to the detection unit 103, they are two-dimensionally arranged in a plan view. FIG. 7B is a diagram showing an example of the shape of the irradiation surface in the case of the configuration of FIG. 7A, in which the light beams from the light irradiation unit 102 on both sides of the detection unit 103 and in the direction orthogonal to this are overlapped.

FIG. 8A is a diagram showing another arrangement example of the light emitting units 102a1 to 102a3 in the case of non-mechanically switching the irradiation direction (FIG. 5), and is a diagram seen from above or below in FIG. In FIG. 8A, the light irradiation units 102 are provided on both sides of the detection unit 103, and the light emission units 102a1, 102a2, and 102a3 of the respective light irradiation units 102 are connected to the detection unit 103 along the surface contacting the subject. On the other hand, they are arranged in a circular arc shape that is concentric with the center of the detection unit 103. A plurality of light sources (laser diodes, etc.) are arranged in the arc-shaped light emitting portions 102a1, 102a2, 102a3. FIG. 8B is a diagram showing an example of the shape of the irradiation surface in the case of the configuration of FIG. 8A, in which a plurality of light beams from the light irradiation units 102 on both sides of the detection unit 103 are overlapped.

(motion)
FIG. 9 is a flowchart showing a processing example of the embodiment, showing an overall processing example at the time of use. In FIG. 9, when the process is started, first, the prescan control function 161 of the processing circuit 160 executes the prescan prior to the main scan (step S1), and then executes the main scan (step S2), and the process To finish.

Step S1 shown in FIG. 9 is a step corresponding to the prescan control function 161. In step S1, the processing circuit 160 reads the program corresponding to the prescan control function 161 from the storage circuit 150 and executes the program, whereby the prescan control function 161 is realized. Step S2 is a step corresponding to the main scan control function 162. In step S2, the processing circuit 160 reads the program corresponding to the main scan control function 162 from the storage circuit 150 and executes the program to realize the main scan control function 162.

FIG. 10 is a flowchart showing a processing example of the embodiment, which is a detailed example of the prescan (step S1) in FIG. In FIG. 10, when the processing is started, the pre-scan control function 161 of the processing circuit 160 causes the light irradiation unit 102 of the probe 101 to irradiate the subject P with light (step S11). In the prescan, the irradiation direction control circuit 170 controls the light irradiation unit 102 in a predetermined reference irradiation direction, and the light amount control circuit 180 controls the light irradiation unit 102 or the light source 110 to a predetermined reference light amount. ..

Next, the prescan control function 161 of the processing circuit 160 receives the photoacoustic wave from the detection unit 103 (step S12), and selects the signal from the subcutaneous pigment (melanin) using the time information (step S13). That is, since the photoacoustic wave propagates through the subject P at the speed of sound, the photoacoustic wave must be received with a delay from the irradiation of light by a time corresponding to the distance between the position where the subcutaneous pigment exists and the detection unit 103. Therefore, it is possible to sort by acquiring the received data within a predetermined time before and after that.

FIG. 11 is a diagram showing a state of measuring the attenuation due to the subcutaneous dye of the subject P. In FIG. 11, the subject P has layers of keratin p1, epidermis p2, dermis p3, and subcutaneous tissue p4 from the surface side. The pigment p5 is mainly present between the epidermis p2 and the dermis p3. Blood vessels p6 are present in the dermis p3 and the subcutaneous tissue p4. In the above-described prescan, the photoacoustic wave W generated by the dye p5 is selected and received by the light L emitted from the light emitting unit 102.

Next, returning to FIG. 10, the pre-scan control function 161 of the processing circuit 160 irradiates and irradiates light with respect to a predetermined location on the subject P (for example, any one location in the measurement target range or a plurality of different locations). It is determined whether or not the reception of the acoustic wave is performed (step S14). That is, in correcting the light amount, it is not necessary to measure up to an accurate distribution of the concentration or amount of the subcutaneous dye, and an average value may be obtained. Therefore, at least one predetermined position It is said that implementation is acceptable, and measurement by thinning is acceptable. Then, when the pre-scan control function 161 of the processing circuit 160 determines that the irradiation of light and the reception of the photoacoustic wave have not been performed at a predetermined location (No in step S14), the location is changed to The process is repeated from irradiation (step S11).

When the pre-scan control function 161 of the processing circuit 160 determines that the irradiation of light and the reception of the photoacoustic wave have been performed at the predetermined location (Yes in step S14), the signal intensity of the reception signal from the subcutaneous dye is determined. Calculate (step S15). When there are received signals at a plurality of points, for example, average signal strength is calculated.

Next, the prescan control function 161 of the processing circuit 160 compares the calculated signal intensity with a reference that has been facilitated in advance, and calculates the light attenuation rate due to the light absorption of the dye (step S16). The reference is, for example, data in which the signal strength and the attenuation rate obtained in advance by experiments or the like are associated with each other under the same conditions (irradiation direction and light amount) as the light irradiation (step S11). Desired.

Next, the pre-scan control function 161 of the processing circuit 160 sets (corrects) the irradiation direction and the light amount of light according to the depth of the subject P according to the calculated attenuation rate (step S17). For example, except for the difference in light attenuation due to the subcutaneous dye, it can be assumed that the tendency of light attenuation in the layers below is the same regardless of race or individual. Therefore, by applying the attenuation rate at the position where the subcutaneous dye has passed to the reference data that associates the depth and the attenuation rate of light, the depth and the attenuation rate of light in the layer further below the subcutaneous layer In order to cancel the attenuation and realize a constant amount of light at each depth, the irradiation direction and the amount of light from the light irradiation unit 102 to the subject P are calculated according to the depth. Thus, the prescan control process is completed.

Steps S11 to S17 shown in FIG. 10 are steps corresponding to the prescan control function 161. Steps S11 to S17 are steps in which the processing circuit 160 reads out the program corresponding to the prescan control function 161 from the storage circuit 150 and executes the program to implement the prescan control function 161.

The order of the processes in the flowchart described with reference to FIG. 10 may be changed within a range that does not essentially affect the result. In addition, the processing may be performed in parallel within a range that does not essentially affect the result.

FIG. 12 is a flowchart showing a processing example of the embodiment, which is a detailed example of the main scan (step S2) in FIG. It should be noted that the processing for one plane position (x, y) along the surface in contact with the subject P is shown, and one-dimensional processing is performed for a predetermined range along the surface in contact with the subject P. Alternatively, when performing a two-dimensional scan, the same processing is repeated after changing the plane position (x, y) on the subject P.

In FIG. 12, when the processing is started, the main scan control function 162 of the processing circuit 160 sets the measurement depth (step S21). For example, the lower limit or the upper limit of the depth range to be measured is set as the initial value.

Next, the main scan control function 162 of the processing circuit 160 controls the light amount of the light irradiation unit 102 of the probe 101 to the light irradiation direction and light amount corresponding to the depth set in the prescan (step S22), and the light irradiation is performed. Light is emitted from the section 102 (step S23). That is, the irradiation direction control circuit 170 controls the light irradiation unit 102 in a predetermined irradiation direction, and the light amount control circuit 180 controls the light irradiation unit 102 or the light source 110 to a predetermined light amount.

13A to 13C are diagrams showing an example of control of the irradiation direction according to the depth, and the case of the non-mechanical configuration shown in FIG. 5 is taken as an example. FIG. 13A shows an example in which the depth is shallow, and light is emitted from the outermost light emitting portions 102a1 of the light emitting portions 102 on both sides of the detecting portion 103. FIG. 13B shows an example in which the depth is medium, and light is emitted from the central light emitting portions 102a2 of the light emitting portions 102 on both sides of the detecting portion 103. FIG. 13C shows an example in which the depth is deep, and light is emitted from the innermost light emitting portions 102a3 of the light emitting portions 102 on both sides of the detecting portion 103. Although the case of the non-mechanical structure shown in FIG. 5 is taken as an example, the case of the mechanical structure shown in FIG. 3 or FIG. The direction is changed. Further, as described above, when a plurality of light irradiation units 102 are provided around the detection unit 103, it is not necessary to control them in the same irradiation direction, and the light beams may overlap at a target depth position. You can do this.

Next, returning to FIG. 12, the main scan control function 162 of the processing circuit 160 receives the photoacoustic wave from the detection unit 103 (step S24), and selects the signal from the depth set using the time information ( Step S25).

Next, the main scan control function 162 of the processing circuit 160 determines whether or not the depth of a predetermined range has been performed (step S26), and if not (No of step S26), the depth is set (step S26). Repeat from S21). In the depth setting (step S21) in this case, when starting from the lower limit of the range of depth to be measured, a predetermined step value is added to the immediately preceding depth to determine the range of depth to be measured. When starting from the upper limit, a value at a predetermined step is subtracted from the depth immediately before.

When it is determined that the main scan control function 162 of the processing circuit 160 has performed the depth within the predetermined range (Yes in step S26), the signal processing circuit 130 and the image generation circuit 140 reconstruct and generate a photoacoustic image. Perform (step S27). In order to improve the processing speed, it is desirable to reconfigure only the light irradiation range that is determined according to the light irradiation direction and not perform unnecessary reconstruction. Further, in blood vessel measurement, when the photoacoustic wave emitted by hemoglobin, which is a light absorber, propagates to the probe 101, the signal intensity is attenuated according to the propagation distance (depth). Therefore, at the time of image generation, the measurement value is quantified by performing visualization in which the signal intensity of the photoacoustic wave is increased (gain is increased) according to the depth of the observation target.

Next, the main scan control function 162 of the processing circuit 160 outputs the generated photoacoustic image to the display 105 or the like (step S28). FIG. 14 is a diagram showing an example of a photoacoustic image when a wire phantom is used as the subject P, and is an example of a photoacoustic image viewed from a direction perpendicular to the surface (xy plane) of the subject P. is there. The wire phantom is one in which a wire of a light absorber is submerged at a position of a predetermined depth in a substance imitating a living body such as intralipos (the wire is arranged in the lateral direction in the illustrated example). This completes the control processing of the main scan.

Steps S21 to S28 shown in FIG. 12 are steps corresponding to the main scan control function 162. Steps S21 to S28 are steps in which the main scan control function 162 is realized by the processing circuit 160 reading out and executing a program corresponding to the main scan control function 162 from the storage circuit 150.

Note that the order of processing in the flowchart described with reference to FIG. 12 may be changed within a range that does not essentially affect the result. In addition, the processing may be performed in parallel within a range that does not essentially affect the result.

(Example of other prescan processing)
The pre-scan described in FIG. 9 corrects (calibrates) the effect of light attenuation due to the subcutaneous dye, which is different depending on the race or individual. By measuring the thickness, the accuracy of correction (calibration) can be further improved.

FIG. 15 is a flowchart showing another processing example of the embodiment, which shows an overall processing example at the time of use. In FIG. 15, when the process is started, the prescan control function 161 of the processing circuit 160 first executes the first prescan prior to the main scan (step S0), and then executes the second prescan (step S0). S1). Then, the main scan control function 162 of the processing circuit 160 executes the main scan (step S2). The main scan (step S2) is similar to the processing shown in FIG. In order to use the result of the first prescan (step S0), the second prescan (step S1) is placed after the first prescan (step S0), but the first prescan (step S0) is performed. If the result of () is not used in the second prescan (step S1), the execution order of the first prescan (step S0) and the second prescan (step S1) may be reversed.

Steps S0 and S1 shown in FIG. 15 are steps corresponding to the prescan control function 161. Steps S0 and S1 are steps in which the processing circuit 160 reads out the program corresponding to the prescan control function 161 from the storage circuit 150 and executes the program to implement the prescan control function 161. Step S2 is a step corresponding to the main scan control function 162. In step S2, the processing circuit 160 reads the program corresponding to the main scan control function 162 from the storage circuit 150 and executes the program to realize the main scan control function 162.

FIG. 16 is a flowchart showing another processing example of the embodiment, which is a detailed example of the first prescan (step S0) in FIG. In FIG. 16, when the processing is started, the pre-scan control function 161 of the processing circuit 160 uses the detection unit 103 of the probe 101 for transmission instead of reception, supplies a drive signal from the transmission circuit 190 to the detection unit 103, and An ultrasonic wave is transmitted to the sample P (step S01).

Next, the prescan control function 161 of the processing circuit 160 causes the detection unit 103 to receive an ultrasonic wave (reflected wave) (step S02).

Next, the pre-scan control function 161 of the processing circuit 160 performs the transmission and reception of ultrasonic waves at a predetermined location on the subject P (for example, an arbitrary location within the measurement target range or a plurality of different locations). It is determined whether or not (step S03). That is, in correcting the light amount, it is not necessary to measure up to an accurate distribution of the thickness of each layer, and an average value may be obtained, so that it is possible to perform it at least at one or more predetermined locations. The measurement by thinning out is acceptable. Then, when the pre-scan control function 161 of the processing circuit 160 determines that the transmission and reception of the ultrasonic waves are not performed at the predetermined location (No in step S03), the location is changed to transmit the ultrasonic waves ( The process is repeated from step S01).

When the pre-scan control function 161 of the processing circuit 160 determines that the ultrasonic wave has been transmitted and received at a predetermined location (Yes in step S03), the thickness of each layer is calculated using the time information of the received signal. (Step S04). FIG. 17 is a diagram showing how the thickness of each layer of the subject P is measured, and as described above, the subject P has layers of the keratin p1, the epidermis p2, the dermis p3, and the subcutaneous tissue p4 from the surface side. Existing. Here, when the ultrasonic wave W1 is transmitted from the detection unit 103, the ultrasonic wave W2 returns to the detection unit 103 as a reflected wave thereof. The reflected wave occurs at the boundary of each layer with different acoustic impedance, and its arrival time depends on the depth, so the thickness of each layer can be calculated from the difference in time information of multiple reflected waves from different boundaries. .. Thus, the control process of the first prescan is completed.

Steps S01 to S04 shown in FIG. 16 are steps corresponding to the prescan control function 161. Steps S01 to S04 are steps in which the processing circuit 160 reads the program corresponding to the prescan control function 161 from the storage circuit 150 and executes the program to implement the prescan control function 161.

The order of the processes in the flowchart described with reference to FIG. 16 may be changed within a range that does not essentially affect the result. In addition, the processing may be performed in parallel within a range that does not essentially affect the result.

FIG. 18 is a flowchart showing another processing example of the embodiment, which is a detailed example of the second prescan (step S1) in FIG. 18, steps S11-2 to S17-2 are the same as FIG. 10 except step S13-2 and step S17-2. That is, in step S13-2 of FIG. 18, the signal from the subcutaneous dye is selected using the time information according to the thickness of each layer measured in the first prescan (step S0). FIG. 19 is a diagram showing an example of selecting a photoacoustic wave using time information according to the layer thickness, based on the time information of the reflected wave of the ultrasonic wave measured in the first prescan (step S0). , The photoacoustic waves (signals of the epidermis) emitted from the layer of the epidermis p2 are selected.

Further, in step S17-2 of FIG. 18, depending on the thickness of each layer calculated in the first prescan (step S0) and the attenuation rate due to the subcutaneous pigment calculated in the second prescan (step S1). , The irradiation direction and the amount of light according to the depth of the subject P are set (corrected). That is, it can be assumed that the properties of each layer with respect to light are almost the same regardless of race or individual, and since the attenuation rate increases with thickness, the attenuation rate per unit thickness of each layer and each layer The attenuation rate at each depth can be calculated more accurately by considering the thickness of the. Then, since the irradiation direction and the light amount of light according to the depth of the subject P are set (corrected) based on the attenuation rate, the irradiation direction and the light amount are calibrated more accurately.

Steps S11-2 to S17-2 shown in FIG. 18 are steps corresponding to the prescan control function 161. Steps S11-2 to S17-2 are steps in which the prescan control function 161 is realized by the processing circuit 160 reading the program corresponding to the prescan control function 161 from the storage circuit 150 and executing it.

Note that the order of processing in the flowchart described with reference to FIG. 18 may be changed within a range that does not essentially affect the result. In addition, the processing may be performed in parallel within a range that does not essentially affect the result.

(Example of diagnosis process)
FIG. 20 is a flowchart showing another example of processing of the embodiment, which is an example of processing for diagnosing a disease from the photoacoustic image acquired by the photoacoustic imaging apparatus 1 or its characteristic data. 20, when the processing is started, the diagnostic function 163 of the processing circuit 160 acquires a photoacoustic image or characteristic data from the storage circuit 150 or the like (step S41), and responds to a disease stored in the storage circuit 150 in advance. It is compared with the photoacoustic image or the characteristic data (step S42). Then, the diagnosis function 163 of the processing circuit 160 outputs a disease corresponding to the photoacoustic image or the characteristic data having a high degree of coincidence as a diagnosis result (step S43), and ends the processing.

The photoacoustic image or its characteristic data acquired by the photoacoustic imaging apparatus 1 is measured with the amount of light kept constant regardless of the depth inside the subject P, and therefore does not affect the diagnosis of disease. Quantitative evaluation is possible without being affected by differences in races and individuals, and it is expected that diseases will be diagnosed accurately.

Steps S41 to S43 shown in FIG. 20 are steps corresponding to the diagnostic function 163. Steps S41 to S43 are steps in which the diagnostic function 163 is realized by the processing circuit 160 reading the program corresponding to the diagnostic function 163 from the storage circuit 150 and executing it.

Note that the order of processing in the flowchart described with reference to FIG. 20 may be changed within a range that does not essentially affect the result. In addition, the processing may be performed in parallel within a range that does not essentially affect the result.

(Example of data structure for more accurate comparison)
The region to be measured and the light amount of the light irradiated at the time of measurement (the intensity of the light irradiation received by the measurement target) are stored, and the measurement result (photoacoustic image or the same) measured at the same region and light amount is stored. By comparing the characteristic data) with each other, more accurate comparison becomes possible. FIG. 21 is a diagram showing an example of the data structure of the measurement result, in which a name or code indicating the site of measurement, a value indicating the amount of light at the time of measurement, and a photoacoustic image or its characteristic data (both are Including the case of holding at the same time). The data having such a structure can also be used as reference data for diagnosing a disease.

(Processing example of result display)
FIG. 22 is a flowchart showing a processing example of the embodiment, which is a processing example of displaying the measurement result. In FIG. 22, when the processing is started, the browsing function 164 of the processing circuit 160 acquires the photoacoustic image or the characteristic data from the storage circuit 150 or the like (step S51).

Next, the browsing function 164 of the processing circuit 160 groups the light amounts (the intensity of light irradiation received by the measurement target) into the same group (step S52), and displays the photoacoustic images or the feature data side by side for each group (step S53). ).

Since the photoacoustic images or the characteristic data having the same light amount can be quantitatively evaluated, it is expected that the diagnosis can be facilitated by displaying them side by side.

Steps S51 to S53 shown in FIG. 22 are steps corresponding to the browsing function 164. Steps S51 to S53 are steps in which the browsing function 164 is realized by the processing circuit 160 reading the program corresponding to the browsing function 164 from the storage circuit 150 and executing the program.

The order of the processes in the flowchart described with reference to FIG. 22 may be changed within a range that does not essentially affect the result. In addition, the processing may be performed in parallel within a range that does not essentially affect the result.

According to at least one embodiment described above, it is possible to quantitatively evaluate the photoacoustic measurement result.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof, as well as included in the scope and spirit of the invention.

1 Photoacoustic Imaging Device 101 Probe 102 Light Irradiation Unit 103 Detection Unit 110 Light Source 120 Reception Circuit 130 Signal Processing Circuit 140 Image Generation Circuit 150 Storage Circuit 160 Processing Circuit 161 Prescan Control Function 162 Main Scan Control Function 163 Diagnostic Function 164 Viewing Function 170 Irradiation direction control circuit 180 Light intensity control circuit 190 Transmitting circuit P Subject

Claims (12)

A light irradiation unit for irradiating light,
A detection unit that detects a photoacoustic wave generated from the subject by absorption of the light,
An image generation unit that generates a photoacoustic image having a pixel value for each pixel based on the signal obtained by the detection unit;
A control unit that controls the irradiation direction and the amount of light of the light irradiation unit so that the amount of light irradiated from the light irradiation unit into the living body becomes a predetermined reference light amount,
A photoacoustic imaging device comprising: The control unit calculates an attenuation rate by the dye based on the intensity of the photoacoustic wave from the subcutaneous dye of the subject due to the light irradiation from the light irradiation unit in the prescan, and the main factor based on the attenuation rate is calculated. Corrects the light amount of the light irradiation unit during scanning,
The photoacoustic imaging apparatus according to claim 1. The control unit calculates the thickness of each layer based on the reflected wave from each layer of the subject due to the ultrasonic irradiation from the detection unit in the prescan, and the light irradiation unit of the light irradiation unit during the main scan based on the thickness. Correct the light intensity,
The photoacoustic imaging apparatus according to claim 1. The light emitting unit includes one or more light emitting units and a driving unit that mechanically moves the light emitting units.
The photoacoustic imaging apparatus according to claim 1. The light emitting unit includes one or more light emitting units and a driving unit that mechanically moves an optical axis of the light emitting units.
The photoacoustic imaging apparatus according to claim 1. The light emitting unit includes a plurality of light emitting units and a switching unit that switches the light emitting units.
The photoacoustic imaging apparatus according to claim 1. The plurality of light emitting units are radially arranged with respect to the detection unit along a surface contacting the subject,
The photoacoustic imaging apparatus according to claim 6. The plurality of light emitting portions are arranged in a one-dimensional manner along a surface in contact with the subject.
The photoacoustic imaging apparatus according to claim 7. The plurality of light emitting portions are two-dimensionally arranged along a surface in contact with the subject.
The photoacoustic imaging apparatus according to claim 7. The plurality of light emitting units are arranged in an arc shape with respect to the detection unit along a surface contacting the subject,
The photoacoustic imaging apparatus according to claim 7. Irradiating light with a light irradiation unit,
A step of detecting a photoacoustic wave generated from the subject by the absorption of the light by a detection unit;
A step of generating a photoacoustic image having a pixel value for each pixel on the basis of the signal obtained by the detection section by an image generation section;
A step of controlling the irradiation direction and the light quantity of the light of the light irradiation section by the control section so that the light quantity irradiated into the living body from the light irradiation section becomes a predetermined reference light quantity,
Including a control method. The procedure of irradiating light with the light irradiation unit,
A procedure for detecting a photoacoustic wave generated from a subject by absorption of the light by a detection unit,
A procedure of generating a photoacoustic image having a pixel value for each pixel based on the signal obtained by the detection unit by the image generation unit,
A procedure for controlling the irradiation direction and the light quantity of the light of the light irradiation section by the control section, so that the light quantity irradiated into the living body from the light irradiation section becomes a predetermined reference light quantity,
A program that causes a computer to execute.