WO2012169178A1

WO2012169178A1 - Photoacoustic image generating device and method

Info

Publication number: WO2012169178A1
Application number: PCT/JP2012/003686
Authority: WO
Inventors: 辻田　和宏; 覚入澤
Original assignee: 富士フイルム株式会社
Priority date: 2011-06-07
Filing date: 2012-06-06
Publication date: 2012-12-13
Also published as: JP2013013713A; JP5743957B2

Abstract

[Problem] To provide a photoacoustic image generating device with which the location of a puncture needle can be ascertained by photoacoustic imaging. [Solution] A laser (13) emits a laser beam. The laser beam is irradiated from a light-irradiating means towards a subject. A puncture needle (15) has a light-emitting unit (16), and laser beam irradiation is implemented via the light-emitting unit (16). A probe (11) detects the photoacoustic signal generated when a light absorber within the subject absorbs the laser beam irradiated from the light-irradiating means. The probe (11) also detects the photoacoustic signal generated when a light absorber within the subject absorbs a laser beam emitted from the light-emitting unit (16). An image generating means (23) generates a photoacoustic image on the basis of the photoacoustic signals.

Description

Photoacoustic image generation apparatus and method

The present invention relates to a photoacoustic image generation apparatus and method, and more specifically, photoacoustics that generate a photoacoustic image by irradiating a subject with laser light and detecting ultrasonic waves generated in the subject by the laser light irradiation. The present invention relates to an image generation apparatus and method.

An ultrasonic inspection method is known as a kind of image inspection method capable of non-invasively examining the state inside a living body. In the ultrasonic inspection, an ultrasonic probe capable of transmitting and receiving ultrasonic waves is used. When ultrasonic waves are transmitted from the ultrasonic probe to the subject (living body), the ultrasonic waves travel inside the living body and are reflected at the tissue interface. By receiving the reflected sound wave with the ultrasonic probe and calculating the distance based on the time until the reflected ultrasonic wave returns to the ultrasonic probe, the internal state can be imaged.

Also, photoacoustic imaging is known in which the inside of a living body is imaged using the photoacoustic effect. In general, in photoacoustic imaging, a living body is irradiated with pulsed laser light such as a laser pulse. Inside the living body, the living tissue absorbs the energy of the pulsed laser light, and ultrasonic waves (photoacoustic signals) are generated by adiabatic expansion due to the energy. By detecting this photoacoustic signal with an ultrasonic probe or the like and constructing a photoacoustic image based on the detection signal, in-vivo visualization based on the photoacoustic signal is possible.

Here, Patent Document 1 refers to a combination of biological information imaging using photoacoustics and treatment using a puncture needle. In Patent Literature 1, a photoacoustic image is generated, and the image is observed to find an affected part such as a tumor or a part suspected of being affected. In order to inspect such a site more precisely or to inject an affected part, etc., a puncture needle such as an injection needle or a cytodiagnosis needle is used to collect cells or inject into the affected part. In Patent Document 1, it is assumed that puncture can be performed while observing an affected area using a photoacoustic image.

JP 2009-31262 A

By the way, when performing puncture of a puncture needle while observing a photoacoustic image in Patent Document 1, it is possible to confirm where the affected part or a suspicious part is located by a photoacoustic image, but at which position the puncture needle is stuck. Is difficult to confirm with a photoacoustic image. If the position of the puncture needle cannot be confirmed on the photoacoustic image, it is impossible to grasp the positional relationship between the puncture needle, particularly the tip thereof, the affected part, or the suspected part, and while observing the photoacoustic image It becomes difficult to puncture the puncture needle at a desired position.

In view of the above, an object of the present invention is to provide a photoacoustic image generation apparatus and method that can confirm the position of a puncture needle on a photoacoustic image.

In order to achieve the above object, the present invention provides a light source that emits light, light irradiation means that irradiates light from the light source toward the subject, and a puncture needle that includes a light emitting unit that emits light from the light source. Based on the photoacoustic signal, an ultrasonic probe that detects a photoacoustic signal generated when the light absorber in the subject absorbs the light emitted from the light irradiation means and the light emitted from the light emitting unit. There is provided a photoacoustic image generation apparatus comprising image generation means for generating a photoacoustic image.

In the present invention, it is preferable that the puncture needle has a light emitting portion at least at the tip thereof.

The light emitting part can be composed of a light guide member formed so that its thickness decreases toward the tip of the puncture needle.

The puncture needle may have a plurality of light emitting units arranged at positions separated from each other. In this case, at least one of the plurality of light emitting units may be configured by a portion where the core is exposed at an intermediate point of the optical fiber that guides light from the light source.

In the present invention, the light irradiation from the light irradiation means and the light emission from the light emitting section are performed simultaneously, and the ultrasonic probe is emitted from the light emitting section and the photoacoustic signal resulting from the light emitted from the light irradiation means. It is good also as detecting simultaneously the photoacoustic signal resulting from light.

Instead of the above, the light irradiation from the light irradiation means and the light emission from the light emitting unit are separately performed, and the image generation means performs the first based on the photoacoustic signal caused by the light irradiated from the light irradiation means. Generating a photoacoustic image, generating a second photoacoustic image based on a photoacoustic signal resulting from light emitted from the light emitting unit, and synthesizing the first photoacoustic image and the second photoacoustic image It is good.

The light source may emit light having a plurality of different wavelengths. In that case, the image generation means may generate a photoacoustic image based on the magnitude relationship of the signal intensity of the photoacoustic signal detected when the light of each wavelength is irradiated.

The image generation means may have a deconvolution means for deconvolution of a differential waveform of light irradiated to the subject from the photoacoustic signal.

The present invention also includes a step of irradiating light from the light irradiation means toward the subject, a step of irradiating the subject from the light emitting portion of the puncture needle having the light emitting portion, and a light absorber in the subject. Detecting a photoacoustic signal generated by absorbing the light emitted from the light irradiating means and the light emitted from the light emitting unit, and generating a photoacoustic image based on the photoacoustic signal. A photoacoustic image generation method characterized by the above is provided.

In the photoacoustic image generation method of the present invention, the step of irradiating light from the light irradiating unit and the step of irradiating light from the light emitting unit are performed simultaneously, and the step of detecting the photoacoustic signal is performed by the light irradiating unit You may detect simultaneously the photoacoustic signal resulting from light and the photoacoustic signal resulting from the light radiate | emitted from the light emission part.

Instead of the above, in the step of irradiating light from the light irradiating means and the step of irradiating light from the light emitting unit separately and detecting the photoacoustic signal, the light irradiating means is caused by the light irradiated from the light irradiating means. In the step of separately detecting the photoacoustic signal and the photoacoustic signal caused by the light emitted from the light emitting unit and generating the photoacoustic image, the first step is based on the photoacoustic signal caused by the light emitted from the light irradiation unit. 1 photoacoustic image is generated, a second photoacoustic image is generated based on a photoacoustic signal resulting from light emitted from the light emitting unit, and the first photoacoustic image and the second photoacoustic image are combined. May be.

In the photoacoustic image generation apparatus and method of the present invention, a light emitting unit is provided on the puncture needle, and the subject is irradiated with light from the light emitting unit. The light emitted from the light emitting unit is absorbed in the vicinity of the puncture needle, and a photoacoustic signal is generated in the vicinity of the puncture needle. By generating a photoacoustic image based on the photoacoustic signal, it is possible to recognize the location where light is emitted from the light emitting unit on the photoacoustic image, and to confirm the position where the puncture needle is present. .

The block diagram which shows the photoacoustic image generating apparatus of 1st Embodiment of this invention. The side view which shows the external appearance of a probe. The front view which shows the external appearance of a probe. The figure which shows the structural example of a light emission part. The figure which shows the illumination range of a light irradiation part, and the illumination range of a light emission part. The figure which shows the example which provided the light emission part in the front-end | tip part of the puncture needle. The figure which shows the illumination range of the light irradiation part at the time of providing a light emission part in the front-end | tip of a puncture needle, and the illumination range of a light emission part. The figure which shows the example which provided two light emission parts in the puncture needle. The figure which shows the structural example for obtaining the two light emission parts shown in FIG. The figure which shows the illumination range of the light irradiation part at the time of providing two light emission parts, and the illumination range of a light emission part. The flowchart which shows an operation | movement procedure. The block diagram which shows the image generation means in the photoacoustic image generation apparatus of 2nd Embodiment of this invention. The block diagram which shows the image generation means in the photoacoustic image generation apparatus of 3rd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a photoacoustic image generation apparatus according to a first embodiment of the present invention. A photoacoustic image generation apparatus (photoacoustic image diagnostic apparatus) 10 includes a probe (ultrasonic probe) 11, an ultrasonic unit 12, and a laser unit (light source) 13. The laser unit 13 generates laser light that irradiates a subject such as a living tissue. The wavelength of the laser light may be appropriately set according to the biological tissue to be observed. The laser light emitted from the laser unit 13 is guided to the probe 11 and the puncture needle 15 using light guide means such as an optical fiber.

The probe 11 is configured as an ultrasonic probe for an endoscope, for example. The probe 11 has light irradiation means for irradiating the subject with laser light guided to the probe 11. The probe 11 detects a photoacoustic signal generated by absorbing the laser beam irradiated by the light absorber in the subject. The probe 11 has, for example, a plurality of ultrasonic transducers arranged one-dimensionally. The light irradiating means does not need to be provided on the probe 11 and may be irradiated with laser light from a place other than the probe 11.

The puncture needle 15 is a needle that is punctured into the subject. The puncture needle 15 has a light emitting unit 16 that emits laser light. When the puncture needle 15 is punctured into the subject, the laser light emitted from the light emitting unit 16 is irradiated to a living tissue or the like in the subject. The illumination range of the light emitting unit 16 is narrower than the illumination range (light irradiation range) of the light irradiation means provided in the probe 11. In addition, since the light emitted from the light emitting unit 16 may be applied to the living tissue in the vicinity of the puncture needle 15, the amount of light and power of the laser light emitted from the light emitting unit 16 is the laser light emitted from the light irradiation unit. It may be lower than the amount of light and power.

The ultrasonic unit 12 includes a receiving circuit 21, AD conversion means 22, image generation means 23, and control means 24. The receiving circuit 21 receives photoacoustic signals detected by a plurality of ultrasonic transducers included in the probe 11. The AD conversion means 22 converts the photoacoustic signal received by the receiving circuit 21 into a digital signal. The AD converter 22 samples the photoacoustic signal at a predetermined sampling period based on, for example, a predetermined sampling clock signal input from the outside.

The image generation means 23 generates a photoacoustic image based on the photoacoustic signal detected by the probe 11. The generation of the photoacoustic image includes, for example, image reconstruction such as phase matching addition, detection, logarithmic conversion, and the like. The image display unit 14 displays the photoacoustic image generated by the image generation unit 23 on a display monitor or the like. The control unit 24 controls each part in the ultrasonic unit 12. For example, the control unit 24 sends a laser oscillation trigger signal to the laser unit 13 to emit laser light from the laser unit 13. A sampling trigger signal is sent to the AD conversion means 22 in accordance with the laser light irradiation to control the sampling start timing of the photoacoustic signal.

2A and 2B show the appearance of the probe 11. FIG. FIG. 2A is a side view of the probe 11, and FIG. 2B is a front view of the probe 11. The probe 11 includes, for example, light irradiation means (light irradiation units) 32 on both sides of a plurality of one-dimensionally arranged ultrasonic transducers 33 when viewed from the front (FIG. 2B). The light irradiation unit 32 irradiates the subject with laser light guided from the laser unit 13 using the optical fiber 31 (FIG. 2A). The light irradiation part 32 is comprised as a surface light source, for example. The light irradiation range (illumination range) of the light irradiation unit 32 corresponds to the generation range of the photoacoustic image. A blood vessel or a lesioned part in the subject absorbs the laser beam emitted from the light irradiation unit 32 and generates a photoacoustic signal.

The probe 11 has a puncture guide 38 for guiding the puncture needle 15. The puncture needle 15 is guided by the puncture guide 38 and punctured into the subject at a predetermined angle. FIG. 2A shows a state where the puncture needle 15 is punctured within the illumination range 34. Although not shown in FIG. 2A, the laser beam guided using the optical fiber 31 is also emitted from the light emitting portion 16 of the puncture needle 15. The light emitted from the light emitting unit 16 is absorbed by, for example, a component such as blood contained in the biological tissue of the subject, and a photoacoustic signal is generated from that portion.

FIG. 3 shows a configuration example of the light emitting unit 16. The light emitting unit 16 is configured as, for example, a linear light source. The light emitting unit 16 is configured by a light guide member formed so that the thickness decreases toward the distal end direction (light traveling direction) of the puncture needle 15, for example. Specifically, it can be configured with a tapered fiber core whose thickness decreases toward the distal end of the puncture needle 15. The tapered shape may be formed by polishing or the like. Unlike the light irradiation unit 32 of the probe 11, the light emitting unit 16 does not need to illuminate a wide range because the light emitting unit 16 only needs to irradiate the living tissue near the puncture needle with the laser light from the light emitting unit 16.

FIG. 4 shows the illumination range of the light irradiation unit 32 (FIG. 1) and the illumination range of the light emitting unit 16 of the puncture needle 15. When the light emitting unit 16 enters the inside of the illumination range 34 of the light irradiation unit 32 of the probe 11, in the illumination range 35 of the light emitting unit 16, in addition to the laser light from the light irradiation unit 32, from the light emitting unit 16 of the puncture needle 15. The laser beam is irradiated. The probe 11 detects a photoacoustic signal generated when the light absorber in the subject absorbs the laser light emitted from the light irradiation unit 32 and the laser light emitted from the light emitting unit 16 of the puncture needle 15. The image generation unit 23 generates a photoacoustic image based on the detected photoacoustic signal.

For example, the laser beam irradiation from the light irradiation unit 32 and the laser beam irradiation from the light emitting unit 16 of the puncture needle 15 are performed separately. For example, laser light irradiation is first performed from the light irradiation unit 32 to detect a photoacoustic signal, and then laser light irradiation is performed from the light emitting unit 16 of the puncture needle 15 to detect the photoacoustic signal. The image generation unit 23 generates a first photoacoustic image based on the photoacoustic signal resulting from the laser light emitted from the light irradiation unit 32. Moreover, a 2nd photoacoustic image is produced | generated based on the photoacoustic signal resulting from the laser beam irradiated from the light emission part 16 of the puncture needle 15, and the produced | generated two images are synthesize | combined.

The lesion 36 and the blood vessel 37 in the illumination range 34 can be imaged by the generated first photoacoustic image. Further, since the light emitting unit 16 of the puncture needle 15 emits laser light only in the vicinity of the puncture needle 15, in the second photoacoustic image, a photoacoustic signal is linearly formed according to the position and direction of the puncture needle. The part to be detected appears. The user observes the synthesized photoacoustic image and searches for the boundary between the strong and weak portions of the photoacoustic signal appearing in a straight line, thereby specifying the position of the puncture needle 15 in the photoacoustic image. can do.

For example, in FIG. 4, suppose that it is desired to puncture the puncture needle 15 into the lesion 36 imaged by the photoacoustic image. At this time, care must be taken so that the tip of the puncture needle 15 does not pierce the blood vessel 37 by mistake. A user such as a doctor punctures the puncture needle 15 while observing the photoacoustic image. At this time, in the photoacoustic image, since the portion irradiated with the laser light from the light emitting unit 16 is drawn brightly, the user can confirm the position of the puncture needle 15 in the photoacoustic image. Since the position of the puncture needle 15 can be confirmed in the photoacoustic image, it is possible to avoid a situation where the tip of the puncture needle 15 accidentally pierces the blood vessel 37.

In addition, although the example in which the light emission part 16 is provided corresponding to the whole puncture needle 15 was demonstrated in FIG. 3, the light emission part 16 does not necessarily need to be provided over the whole puncture needle 15, At least the front-end | tip What is necessary is just to be provided in the part. For example, a laser beam may be guided to the tip of the puncture needle 15 using a thin optical fiber or the like, and a light emitting unit may be provided at the tip of the puncture needle 15. The optical fiber that guides the laser beam to the needle tip may pass through the inside of the puncture needle 15 or may be arranged outside the puncture needle 15.

FIG. 5 shows an example in which the light emitting unit 16 is provided at the tip of the puncture needle 15. FIG. 6 shows an illumination range 34 of the light irradiation unit 32 and an illumination range 35 of the light emitting unit 16 when the light emitting unit is provided at the tip of the puncture needle. In the case of this example, the length of the light emitting unit 16 is shortened in the length direction of the puncture needle 15, and the illumination range 35 is narrower than in the case of FIG. However, even with such a configuration, the position of the tip of the puncture needle 15 can be specified in the photoacoustic image.

The light-emitting part 16 provided in the puncture needle 15 is not restricted to one, It is good also as providing the several light-emitting part 16 arrange | positioned in the mutually distant position. FIG. 7 shows an example in which two light emitting portions 16 are provided on the puncture needle 15. The puncture needle 15 has a light emitting portion 16b at an intermediate portion in addition to the light emitting portion 16a at the tip portion. FIG. 8 shows a configuration example for obtaining the two light emitting

units

16a and 16b shown in FIG. For example, the light emitting portion 16b in the intermediate portion of the puncture needle 15 can be realized by partially peeling off the optical fiber cladding 42 to expose the core 41 and further polishing a part of the core 41. The light emitting portion 16a at the tip can be realized by exposing the core 41.

FIG. 9 shows the illumination range of the light irradiation unit 32 and the illumination range of the light emitting unit 16 when two light emitting units are provided. An illumination range 35a and an illumination range 35b are formed corresponding to the

light emitting portions

16a and 16b of the puncture needle 15. In this case, a photoacoustic signal is detected from the vicinity of the puncture needle 15 in each of the illumination range 35a and the illumination range 35b. In the photoacoustic image, the position connecting the portions where the two photoacoustic signals are detected can be detected as the position of the puncture needle.

FIG. 10 shows the operation procedure. The control means 24 of the ultrasonic unit 12 sends a laser oscillation trigger signal to the laser unit 13. Upon receiving the laser oscillation trigger signal, the laser unit 13 starts laser oscillation and emits pulsed laser light. The subject is irradiated with the pulse laser beam emitted from the laser unit 13 from the light irradiation unit 32 (FIG. 2A) of the probe 11 (step S1).

The probe 11 detects a photoacoustic signal generated in the subject by the laser beam irradiation from the light irradiation unit 32 (step S2). The AD converter 22 receives the photoacoustic signal via the receiving circuit 21 and samples the photoacoustic signal. The image generation means 23 generates a first photoacoustic image based on the sampled photoacoustic signal (step S3).

Subsequently, laser light irradiation is performed from the light emitting portion 16 of the puncture needle 15 (step S4). The probe 11 detects a photoacoustic signal generated in the subject by the irradiation of the laser light from the light emitting unit 16. (Step S5). The AD converter 22 receives the photoacoustic signal via the receiving circuit 21 and samples the photoacoustic signal. The image generation means 23 generates a second photoacoustic image based on the sampled photoacoustic signal (step S6).

The image generation means 23 synthesizes and outputs the generated first and second photoacoustic images. The image display means 14 displays the synthesized photoacoustic image (step S7). Instead of performing image generation by the image generation unit 23, the image display unit 14 may display the first and second photoacoustic images in a superimposed manner.

In the present embodiment, the puncture needle 15 is provided with a light emitting unit 16 and laser light is emitted from the light emitting unit 16. The laser light emitted from the light emitting unit 16 is absorbed in the vicinity of the puncture needle 15, and a photoacoustic signal is generated in the vicinity of the puncture needle 15. By generating a photoacoustic image based on such a photoacoustic signal, the position of the puncture needle 15 and the like can be confirmed on the photoacoustic image. In particular, a photoacoustic image (first photoacoustic image) generated by irradiating laser light from the light irradiation unit 32 and a photoacoustic image (second photon) generated by irradiating laser light from the light emitting unit 16 of the puncture needle 15. When the puncture needle 15 is punctured while observing the displayed photoacoustic image, the positional relationship between the position of the lesion and the like on the photoacoustic image and the puncture needle 15 is displayed. Can be grasped.

Subsequently, a second embodiment of the present invention will be described. In the present embodiment, the subject is irradiated with light of a plurality of wavelengths, and a photoacoustic signal when the light of each wavelength is irradiated is detected. In the present embodiment, functional imaging is performed by using the photoacoustic signal when light of a plurality of wavelengths is irradiated, and utilizing the fact that the light absorption characteristics of each light absorber differ depending on the wavelength.

In this embodiment, the laser unit 13 (FIG. 1) is configured to be able to emit laser beams having a plurality of different wavelengths. The pulsed laser light emitted from the laser unit 13 is guided to the probe 11 using light guide means such as an optical fiber, and is emitted from the probe 11 toward the subject. Further, the pulsed laser light emitted from the laser unit 13 is emitted from the light emitting portion 16 of the puncture needle 15 in the direction of the subject. In the following description, it is assumed that the laser unit 13 can emit a pulse laser beam having a first wavelength and a pulse laser beam having a second wavelength.

For example, consider about 750 nm as the first wavelength (center wavelength) and consider about 800 nm as the second wavelength. The molecular absorption coefficient at a wavelength of about 750 nm of oxygenated hemoglobin (oxy-Hb combined with oxygen) contained in a large amount of human arteries is lower than the molecular absorption coefficient at a wavelength of about 800 nm. On the other hand, the molecular absorption coefficient at a wavelength of about 750 nm of deoxygenated hemoglobin (hemoglobin deoxy-Hb not bound to oxygen) contained in a large amount in veins is higher than the molecular absorption coefficient at a wavelength of about 800 nm. By utilizing this property and examining whether the photoacoustic signal obtained at a wavelength of about 750 nm is relatively large or small with respect to the photoacoustic signal obtained at a wavelength of about 800 nm, A photoacoustic signal from a vein can be discriminated.

The receiving circuit 21 receives the photoacoustic signal detected by the probe 11. The AD conversion means 22 samples the photoacoustic signal received by the receiving circuit 21. The AD conversion means 22 samples a photoacoustic signal at a predetermined sampling period in synchronization with, for example, an AD clock signal.

The sampling of the photoacoustic signal is repeated for the number of wavelengths of light emitted from the laser unit 13. For example, first, the subject is irradiated with light of the first wavelength from the laser unit 13, and the photoacoustic signal detected by the probe 11 when the subject is irradiated with pulsed laser light of the first wavelength is sampled. Next, the subject is irradiated with light of the second wavelength from the laser unit 13, and the photoacoustic signal detected by the probe 11 when the pulse laser beam of the second wavelength is irradiated is sampled. The image generation means 23 includes a photoacoustic signal (first photoacoustic signal) corresponding to light having the first wavelength and a photoacoustic signal (second photoacoustic signal) corresponding to light having the second wavelength. A photoacoustic signal that can distinguish between an artery and a vein is generated based on the relative magnitude of the relative signal intensity.

FIG. 11 shows the image generation means 23 in this embodiment. The image generation unit 23 includes a two-wavelength data complex number conversion unit 231, a photoacoustic image reconstruction unit 232, a two-wavelength data calculation unit 233, an intensity information extraction unit 234, a detection / logarithm conversion unit 235, and a photoacoustic image construction unit 236. Have. The two-wavelength data complex numbering means 231 generates complex number data in which one of the first photoacoustic signal and the second photoacoustic signal is a real part and the other is an imaginary part. In the following description, it is assumed that the two-wavelength data complexization unit 231 generates complex data having the first photoacoustic signal as a real part and the second photoacoustic signal as an imaginary part.

The photoacoustic image reconstruction means 232 receives complex number data from the two-wavelength data complex numbering means 231 and reconstructs the photoacoustic signal. The photoacoustic image reconstruction means 232 performs image reconstruction from the input complex number data by a Fourier transform method (FTA method). For the image reconstruction by the Fourier transform method, for example, a conventionally known method described in the document “Photoacoustic Image Reconstruction-A A Quantitative Analysis” Jonathan I I Sperl I et al. SPIE-OSA Vol. it can. The photoacoustic image reconstruction unit 232 inputs Fourier transform data indicating the reconstructed image to the intensity information extraction unit 234 and the two-wavelength data calculation unit 233.

The two-wavelength data calculation means 233 extracts the relative magnitude of the relative signal intensity between the photoacoustic data corresponding to each wavelength. In this embodiment, the two-wavelength data calculation unit 233 uses the reconstructed image reconstructed by the photoacoustic image reconstruction unit 232 as input data, and compares the real part and the imaginary part from the input data that is complex data. Sometimes, phase information indicating which is relatively large is extracted. For example, when the complex number data is represented by X + iY, the two-wavelength data calculation unit 233 generates θ = tan−1 (Y / X) as the phase information. When X = 0, θ = 90 °. When the first photoacoustic data (X) constituting the real part and the second photoacoustic data (Y) constituting the imaginary part are equal, the phase information is θ = 45 °. The phase information approaches θ = 0 ° as the first photoacoustic data is relatively large, and approaches θ = 90 ° as the second photoacoustic data is relatively large.

The intensity information extraction unit 234 generates intensity information indicating the signal intensity based on the photoacoustic data corresponding to each wavelength. In the present embodiment, the intensity information extraction unit 234 uses the reconstructed image reconstructed by the photoacoustic image reconstruction unit 232 as input data, and generates intensity information from the input data that is complex number data. For example, when the complex number data is represented by X + iY, the intensity information extraction unit 234 extracts (X2 + Y2) 1/2 as the intensity information. The detection / logarithm conversion means 235 generates an envelope of data indicating the intensity information extracted by the intensity information extraction means 234, and then logarithmically converts the envelope to widen the dynamic range.

The photoacoustic image construction means 236 receives the phase information from the two-wavelength data calculation means 233 and the intensity information after the detection / logarithmic conversion processing from the detection / logarithmic conversion means 235. The photoacoustic image construction unit 236 generates a photoacoustic image based on the input phase information and intensity information. For example, the photoacoustic image construction unit 236 determines the luminance (gradation value) of each pixel in the distribution image of the light absorber based on the input intensity information. The photoacoustic image construction unit 236 determines the color (display color) of each pixel in the light absorber distribution image based on, for example, phase information. The photoacoustic image construction unit 236 determines the color of each pixel based on the input phase information using, for example, a color map in which a phase range of 0 ° to 90 ° is associated with a predetermined color.

Here, since the range of the phase from 0 ° to 45 ° is a range in which the first photoacoustic signal is larger than the second photoacoustic signal, the source of the photoacoustic signal is more than the absorption with respect to light having a wavelength of 798 nm. It is considered that this is a vein through which blood mainly containing deoxygenated hemoglobin is less absorbed with respect to light having a wavelength of 756 nm. On the other hand, since the first 45 ° to 90 ° phase is a range in which the first photoacoustic data is smaller than the second photoacoustic data, the source of the photoacoustic signal has a wavelength larger than the absorption with respect to light having a wavelength of 798 nm. It is considered that this is an artery through which blood mainly containing oxygenated hemoglobin flows, which absorbs more light at 756 nm.

Therefore, as a color map, for example, the phase gradually changes so that the phase is 0 ° in blue and the phase becomes colorless (white) as the phase approaches 45 °, and the phase 90 ° is red and the phase is 45. Use a color map that gradually changes its color to become white as it approaches °. In this case, on the photoacoustic image, the portion corresponding to the artery can be represented in red, and the portion corresponding to the vein can be represented in blue. Instead of using the intensity information, the gradation value may be constant and only the color classification of the portion corresponding to the artery and the portion corresponding to the vein may be performed according to the phase information.

Generation of the photoacoustic image based on the photoacoustic signals corresponding to the light of the two wavelengths described above is performed by light irradiation from the light irradiation unit 32 (FIG. 2A) of the probe 11 and the light emission unit 16 (FIG. 1) of the puncture needle 15. To each of the light irradiation from. For example, light of a first wavelength and light of a second wavelength are sequentially emitted from the light irradiation unit 32 of the probe 11 toward the subject, and a photoacoustic signal corresponding to each wavelength is detected to detect a photoacoustic image. (First photoacoustic image) is generated. Thereafter, the light of the first wavelength and the light of the second wavelength are sequentially emitted from the light emitting unit 16 of the puncture needle 15 punctured in the subject, and a photoacoustic signal corresponding to each wavelength is detected to detect photoacoustics. An image (second photoacoustic image) is generated. The point which synthesize | combines a 1st photoacoustic image and a 2nd photoacoustic image may be the same as that of 1st Embodiment.

In the above, the light of the first wavelength and the light of the second wavelength are irradiated from the light irradiation from the light irradiation unit 32 of the probe 11 and the light irradiation from the light emitting unit 16 of the puncture needle 15, respectively. However, instead of this, light having a single wavelength may be emitted from the light emitting portion 16 of the puncture needle 15. When only light of a single wavelength is irradiated to the subject, the complexization by the two-wavelength data complexing means 231 and the extraction of phase information by the two-wavelength data calculating means 233 are not necessary. When only light having a single wavelength is irradiated, a photoacoustic image may be generated based on the intensity information extracted by the intensity information extraction unit 234.

In this embodiment, the laser unit 13 irradiates the subject with laser beams having a plurality of different wavelengths. By using a photoacoustic signal (photoacoustic data) when irradiated with pulsed laser beams of a plurality of wavelengths, it is possible to perform functional imaging using the fact that the light absorption characteristics of each light absorber differ depending on the wavelength. . For example, by irradiating light with a wavelength that makes it possible to distinguish between an artery and a vein, it is possible to determine whether the blood vessel existing in the direction in which the puncture needle travels is an artery or a vein. You can do it more safely.

Further, in the present embodiment, complex number data in which one of the first photoacoustic signal and the second photoacoustic signal obtained at two wavelengths is a real part and the other is an imaginary part is generated. Two reconstructed images are generated from the complex number data by Fourier transform. In this case, since reconfiguration is only required once, reconfiguration can be performed more efficiently than when the first photoacoustic signal and the second photoacoustic signal are reconfigured separately. .

Subsequently, a third embodiment of the present invention will be described. FIG. 11 shows image generation means 23a in the third embodiment of the present invention. The image generation unit 23a includes a deconvolution unit 237 in addition to the configuration of the image generation unit 23 in the second embodiment shown in FIG.

The deconvolution means 237 generates a signal obtained by deconvolution of the photodifferential waveform, which is a differential waveform of the time waveform of the light intensity of the light applied to the subject, from the photoacoustic signal reconstructed by the photoacoustic image reconstruction means 232. Generate. For example, the deconvolution means 237 executes a process of deconvolution of the optical differential waveform with respect to each of the real part and the imaginary part in the complexized data.

The two-wavelength data calculation means 233 generates phase information from the photoacoustic signal obtained by deconvolution of the optical differential waveform. Moreover, the intensity information extraction means 234 extracts intensity information from the photoacoustic signal from which the optical differential waveform is deconvoluted. The subsequent processing is the same as in the second embodiment. Note that irradiation with a plurality of wavelengths of light is not essential for deconvolution. That is, it is good also as irradiating a test object with the light of a single wavelength, and deconvolving an optical differential waveform from the detected photoacoustic signal.

The deconvolution means 237 converts the reconstructed photoacoustic signal from a time domain signal to a frequency domain signal, for example, by discrete Fourier transform. Further, the optical differential waveform is also converted from a time domain signal to a frequency domain signal by discrete Fourier transform. The deconvolution means 237 obtains the inverse of the Fourier-transformed optical differential waveform as an inverse filter, and applies the inverse filter to the Fourier-transformed frequency domain photoacoustic signal. By applying the inverse filter, the optical differential waveform is deconvoluted in the frequency domain signal. Thereafter, the photoacoustic signal to which the inverse filter is applied is converted from a frequency domain signal to a time domain signal by inverse Fourier transform.

Deconvolution of the optical differential waveform will be described. Consider a micro-absorbing particle that is a light absorber, and consider that this micro-absorbing particle absorbs pulsed laser light to generate a pressure wave (photoacoustic pressure wave). The pressure waveform pmicro (R, t) when the photoacoustic pressure wave generated from the micro-absorbing particle at the position r is observed at the position R with time t is [Phys. Rev. Lett. 86 (2001) From 3550.], the following spherical wave is obtained.

Here, I (t) is a time waveform of the light intensity of the excitation light, the coefficient k is a conversion coefficient when the particle absorbs light and outputs an acoustic wave, and vs is the sound velocity of the subject. . Positions r and R are vectors indicating positions in space. The pressure generated from the microabsorbent particles is a spherical wave proportional to the optical pulse differential waveform, as shown in the above formula.

Since the pressure waveform actually obtained from the object to be imaged has a macroscopic absorber size, it is considered to be a waveform obtained by superimposing the above micro absorption waveforms (superposition principle). Here, the absorption distribution of particles emitting macroscopic photoacoustic waves is A (r−R), and the observation waveform of pressure from the macroscopic absorber is pmacro (R, t). At the observation position R, since the photoacoustic wave from the absorbing particles located at the radius vst from the observation position R is observed at each time, the observation waveform pmacro (R, t) is expressed by the following pressure waveform equation: Indicated by

As can be seen from the above equation (1), the observed waveform shows a convolution type of optical pulse differentiation. The absorber distribution can be obtained by deconvolution of the optical pulse differential waveform from the observed waveform. In the above description, the example of deconvolution of the photodifferential waveform from the photoacoustic signal after reconstruction is described, but instead, the photodifferential waveform is deconvoluted from the photoacoustic signal before reconstruction. Also good.

In this embodiment, the differential waveform of the light irradiated to the subject is deconvoluted from the detected photoacoustic signal. By deconvolution of the optical differential waveform, the distribution of the light absorber can be obtained, and an absorption distribution image can be generated. By generating an absorption distribution image, blood vessels can be observed more clearly. Other effects are the same as those of the second embodiment.

In each of the above embodiments, the laser light irradiation from the light irradiation unit 32 and the laser light irradiation from the light emitting unit 16 of the puncture needle 15 have been described as being performed separately, but the laser light irradiation from the light irradiation unit 32 and The laser light irradiation from the light emitting unit 16 of the puncture needle 15 may be performed simultaneously. In that case, the probe 11 simultaneously receives a photoacoustic signal caused by the laser light emitted from the light emitting unit 32 and a photoacoustic signal caused by the laser light emitted from the light emitting unit 16 of the puncture needle 15 (at a time). )To detect. In this case, since the generation of the photoacoustic image is sufficient, the image display can be performed in a shorter time than when two photoacoustic images are generated and synthesized (superimposed) later.

In the second embodiment, the example in which the first photoacoustic signal and the second photoacoustic signal are complexized has been described. However, the first photoacoustic signal and the second photoacoustic are not complexized. The signal may be reconstructed separately. Further, the reconstruction method is not limited to the Fourier transform method. Further, in the second embodiment, the ratio between the first photoacoustic signal and the second photoacoustic signal is calculated using the complex information after being converted into a complex number, but the ratio is calculated from the intensity information of both. The same effect can be obtained. The intensity information can be generated based on the signal intensity in the reconstructed image corresponding to one wavelength and the signal intensity in the reconstructed image corresponding to the other wavelength.

When generating a photoacoustic image, the number of wavelengths of the pulsed laser light applied to the subject is not limited to two, and the subject is irradiated with three or more pulsed laser lights, and photoacoustic data corresponding to each wavelength is generated. A photoacoustic image may be generated based on this. In this case, for example, the two-wavelength data calculation unit 233 may generate a relative signal intensity magnitude relationship between the photoacoustic data corresponding to each wavelength as the phase information. Further, the intensity information extraction unit 234 may generate, as intensity information, a collection of signal intensities in photoacoustic data corresponding to each wavelength, for example.

As mentioned above, although this invention was demonstrated based on the suitable embodiment, the photoacoustic image generation apparatus of this invention is not limited only to the said embodiment, Various correction and change are possible from the structure of the said embodiment. Those subjected to are also included in the scope of the present invention.

Claims

A light source that emits light;
A light irradiating means for irradiating the subject with the light;
A puncture needle having a light emitting part for emitting the light;
An acoustic wave probe for detecting a photoacoustic signal generated by a light absorber in a subject absorbing light emitted from the light irradiating means and light emitted from the light emitting unit;
The photoacoustic image generation apparatus provided with the image generation means which produces | generates a photoacoustic image based on the said photoacoustic signal.
The photoacoustic image generating apparatus according to claim 1, wherein the puncture needle has a light emitting portion at least at a tip portion thereof.
3. The photoacoustic image generation according to claim 1, wherein the light emitting unit is configured by a light guide member formed so that a thickness thereof decreases in a distal direction of the puncture needle. apparatus.
The photoacoustic image generating apparatus according to any one of claims 1 to 3, wherein the puncture needle has a plurality of light emitting units arranged at positions separated from each other.
5. The photoacoustic image generation according to claim 4, wherein at least one of the plurality of light emitting units includes a portion where a core is exposed at an intermediate point of the optical fiber that guides the light. apparatus.
Light irradiation from the light irradiation means and light emission from the light emitting section are performed simultaneously, and the acoustic probe emits a photoacoustic signal resulting from the light emitted from the light irradiation means and the light emitting section. The photoacoustic image generating apparatus according to claim 1, wherein a photoacoustic signal caused by the emitted light is simultaneously detected.
The light irradiation from the light irradiation unit and the light emission from the light emitting unit are separately performed, and the image generation unit performs the first light based on the photoacoustic signal resulting from the light irradiated from the light irradiation unit. An acoustic image is generated, a second photoacoustic image is generated based on a photoacoustic signal resulting from the light emitted from the light emitting unit, and the first photoacoustic image and the second photoacoustic image are combined. The photoacoustic image generating apparatus according to claim 1, wherein
The photoacoustic image generating apparatus according to any one of claims 1 to 7, wherein the light source emits light having a plurality of different wavelengths.
The said image generation means produces | generates a photoacoustic image based on the magnitude relationship of the signal intensity of the photoacoustic signal detected when the light of each wavelength was irradiated. Photoacoustic image generation apparatus.
The photoacoustic according to any one of claims 1 to 9, wherein the image generation means includes deconvolution means for deconvolution of a differential waveform of light irradiated on the subject from a photoacoustic signal. Image generation device.
Irradiating light from the light irradiation means toward the subject;
Irradiating the subject with light from the light emitting part of the puncture needle having the light emitting part;
A step of detecting a photoacoustic signal generated by a light absorber in the subject absorbing light emitted from the light irradiating means and light emitted from the light emitting unit;
And a photoacoustic image generation method based on the photoacoustic signal.
Performing the step of irradiating light from the light irradiation means and the step of irradiating light from the light emitting unit,
The step of detecting the photoacoustic signal simultaneously detects a photoacoustic signal caused by light emitted from the light irradiation means and a photoacoustic signal caused by light emitted from the light emitting unit. Item 12. The photoacoustic image generation method according to Item 11.
The step of irradiating light from the light irradiating means and the step of irradiating light from the light emitting unit are performed separately,
In the step of detecting the photoacoustic signal, separately detecting a photoacoustic signal caused by light emitted from the light irradiating means and a photoacoustic signal caused by light emitted from the light emitting unit,
In the step of generating the photoacoustic image, a first photoacoustic image is generated based on a photoacoustic signal resulting from the light emitted from the light irradiation means, and photoacoustic resulting from the light emitted from the light emitting unit. The photoacoustic image generation method according to claim 11, wherein a second photoacoustic image is generated based on a signal, and the first photoacoustic image and the second photoacoustic image are synthesized.
The photoacoustic image generation method according to claim 11, wherein the puncture needle has a light emitting portion at least at a tip portion thereof.
The photoacoustic image generation method according to any one of claims 11 to 14, wherein the puncture needle has a plurality of light emitting units arranged at positions separated from each other.
The photoacoustic image generating method according to claim 11, wherein light having a plurality of wavelengths different from each other is emitted to the subject.
The photoacoustic image is generated based on the magnitude relationship of the signal intensity of the photoacoustic signal detected when the light of each wavelength is irradiated in the step of generating the photoacoustic image. The photoacoustic image generation method of description.
The photoacoustic image according to any one of claims 11 to 17, wherein the step of generating the photoacoustic image includes a step of deconvoluting a differential waveform of light irradiated on a subject from the photoacoustic signal. Image generation method.