Photoacoustic-ultrasonic probe having acoustic waveguide layer

Abstract

The present invention comprises: an acoustic waveguide layer having a slab shape or a square shape and having a light reflective surface for reflecting light irradiated from a light source, at an angle inclined with respect to an irradiation direction of the light; and a piezoelectric layer disposed on one surface or the other surface of the acoustic waveguide layer disposed such that the light reflected from the light reflective surface of the acoustic waveguide layer travels toward an object to be inspected, wherein a transparent electrode may be formed in a predetermined region of each of both surfaces of the piezoelectric layer.

Description

Photoacoustic-ultrasonic probe having an acoustic waveguide layer

[0001] This invention is most closely related to photoacoustic endoscopy (PAE) among the three core areas of photoacoustic imaging technology, which is attracting attention as a next-generation medical imaging technology: photoacoustic computed tomography (PACT), photoacoustic microscopy (PAM), and photoacoustic endoscopy (PAE).

[0002] In the case of a conventional transparent ultrasonic transducer-based photoacoustic array probe (Prior Art 1), when a laser beam fired toward a subject passes through an absorbing layer, a portion of the laser beam is absorbed by the absorbing layer (which also generates photoacoustic waves according to the photoacoustic principle) and is included in the “photoacoustic image of the subject” ultimately to be obtained, acting as a kind of image artifact.

[0003] In other words, the operating principle and ultimate goal of the device is to generate a "photoacoustic image of the subject" by irradiating a laser beam onto the subject to induce photoacoustic waves based on the photoacoustic effect and detecting them; however, the sound-absorbing layer, which is a component of the transparent ultrasonic transducer contained within the device (since its transparency is not very high unlike that of a transparent electrode), absorbs a significant amount of the laser beam passing through it, thereby generating photoacoustic waves as well.

[0004] As such, there has been a serious problem in which these unwanted photoacoustic waves, generated in the sound-absorbing layer rather than within the tissue under examination, mix with the photoacoustic waves generated from the tissue (i.e., the desired signal) because a portion of them enters the tissue and is reflected back out, resulting in them appearing as image artifacts.

[0005] The objective of the present invention is to provide a photoacoustic-ultrasonic probe having a unique structure capable of completely eliminating the sound-absorbing layer required in conventional transparent ultrasonic transducers from the light path by changing the position of the sound-absorbing layer through the addition of an element called an acoustic waveguide layer to guide ultrasound.

[0006] A photoacoustic-ultrasonic probe according to one embodiment of the present invention has a slab shape or a square shape and includes an acoustic waveguide layer having a light-reflecting surface that reflects light irradiated from a light source at an angle inclined with respect to the direction of irradiation of the light; and a piezoelectric layer disposed on one side or the other side of the acoustic waveguide layer arranged so that light reflected from the light-reflecting surface of the acoustic waveguide layer travels toward a subject, wherein a transparent electrode is formed in a predetermined area on both sides of the piezoelectric layer.

[0007] In addition, the acoustic waveguide layer comprises an optically and acoustically transparent material, and the light-reflecting surface may be formed in a diagonal direction opposite to the acoustic waveguide layer.

[0008] In addition, the acoustic waveguide layer includes two optical right-angle prisms joined together, and the two optical right-angle prisms may have a square shape.

[0009] Additionally, the light-reflecting surface may include at least one of a dielectric reflective film and a metal reflective film. However, the material of the light-reflecting surface is not limited thereto.

[0010] In addition, the acoustic waveguide layer has an acoustic impedance different from that of the piezoelectric layer, and can be configured so that photoacoustic waves or ultrasound generated when the light reaches the subject are transmitted to the piezoelectric layer through the acoustic waveguide layer.

[0011] Additionally, it may further include an absorbing layer positioned on the opposite side of the piezoelectric layer with respect to the acoustic waveguide layer, which attenuates the reverberation that occurs after the photoacoustic-ultrasonic wave is transmitted to the piezoelectric layer through the acoustic waveguide layer.

[0012] Additionally, the piezoelectric layer may be positioned so as to be spaced apart from the light transmission path with respect to the acoustic waveguide layer.

[0013] In addition, the transparent electrode may be formed in any one of a linear array shape, a concentric ring shape, and a double-door shape. However, the shape of the transparent electrode is not limited thereto and may be applied in other shapes.

[0014] In addition, the transparent electrode may be formed in an area other than the region corresponding to the central path of the light.

[0015] In addition, a matching layer may be further formed on the surface of the piezoelectric layer opposite to the acoustic waveguide layer to mitigate the acoustic impedance mismatch between the piezoelectric layer and the surrounding medium.

[0016] A photoacoustic-ultrasonic probe according to one embodiment of the present invention has the effect of having a unique structure that can completely eliminate the sound-absorbing layer required in conventional transparent ultrasonic transducers by changing the position of the sound-absorbing layer in the light path by adding an element called an acoustic waveguide layer and guiding ultrasound through it.

[0017] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description below.

[0018] FIG. 1 is a schematic diagram showing the structure of a photoacoustic-ultrasonic probe including an acoustic waveguide layer according to one embodiment of the present invention.

[0019] FIG. 2 is a schematic diagram showing the structure of a photoacoustic-ultrasonic probe based on an ultrasonic array transducer having a ring-shaped electrode in the basic structure of FIG. 1, according to another embodiment of the present invention.

[0020] FIG. 3 is a schematic diagram showing the structure of a photoacoustic-ultrasonic probe based on an ultrasonic array transducer having a bicameral electrode in the basic structure of FIG. 1, according to another embodiment of the present invention.

[0021] FIG. 4 is a schematic diagram showing the structure of a photoacoustic-ultrasonic probe in which the piezoelectric layer and the electrode layer are also completely removed from the path of the laser beam according to another embodiment of the present invention.

[0022] The present invention is capable of various modifications and may have various embodiments; therefore, specific embodiments are illustrated in the drawings and described in detail. The effects and features of the present invention, and the methods for achieving them, will become clear by referring to the embodiments described below in detail together with the drawings. However, the present invention is not limited to the embodiments disclosed below but can be implemented in various forms.

[0023] In the following embodiments, terms such as first, second, etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another component.

[0024] In the following examples, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0025] In the following embodiments, terms such as "include" or "have" mean that the features or components described in the specification are present, and do not preclude the possibility that one or more other features or components may be added.

[0026] In the following embodiments, when a component is described as being "connected" to another component, this includes not only being directly connected to the other component but also being indirectly connected by another component.

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. When describing with reference to the drawings, identical or corresponding components are given the same reference numerals, and redundant descriptions thereof will be omitted. The present invention broadly belongs to the field of ultrasound and photoacoustic imaging, and more specifically, relates to photoacoustic-ultrasound fusion endoscopy (PAE-EUS) applying a transparent ultrasound transducer.

[0028] The present invention provides a photoacoustic-ultrasound probe structure having an acoustic waveguide layer capable of resolving the problem of image artifacts occurring when a laser beam passes through an acoustic absorption layer (i.e., a backing layer) commonly included in conventional transparent ultrasound transducer-based photoacoustic array probes. The probe concept presented in the present invention can be applied in various ways, including handle-type, or handheld, probes designed to allow a user to directly hold the device and freely image any desired area; miniature probes used to visualize areas of interest in invasive or non-invasive surgical procedures; and endoscopic devices used to diagnose suspected diseased areas such as the gastrointestinal tract or blood vessels.

[0029] FIG. 1 is a schematic diagram showing the structure of a photoacoustic-ultrasonic probe including an acoustic waveguide layer according to one embodiment of the present invention.

[0030] Referring to FIG. 1, the structure of a photoacoustic-ultrasonic probe including an acoustic waveguide layer, which is a core concept of the present invention, will be described in detail according to one embodiment of the present invention.

[0031] A photoacoustic-ultrasonic probe according to an embodiment of the present invention comprises: an optical fiber (100) that guides a laser beam emitted from a predetermined laser light source (not shown); a laser beam shaper (120) that changes the laser beam emitted through the said optical fiber (100) to an appropriate size and shape; an acoustic waveguide layer (130) having a slab or cube shape that serves to redirect the laser beam passing through the said laser beam shaper (120) by approximately 90° and send it toward a subject (not shown), and is made of a material that allows sound waves to propagate well, thereby simultaneously serving as a kind of sound waveguide layer; a piezoelectric layer (110) located on the surface of the said acoustic waveguide layer (130) toward the subject; a transparent electrode (111) formed on the inner and outer surfaces of the said piezoelectric layer (110); and a rear surface of the said acoustic waveguide layer (130), that is, the surface opposite to the direction in which the laser beam is finally emitted. It may include a sound-absorbing layer (140) and a probe casing (150) that can wrap around the aforementioned elements in an appropriate shape.

[0032] That is, in the case of FIG. 1, which is an embodiment provided by the present invention, it should be noted that the piezoelectric layer (110), transparent electrode (111), and sound-absorbing layer (140), which can be said to be the three basic elements constituting a transparent ultrasonic transducer, are not in close contact with each other, but rather have a structure in which the piezoelectric layer (110) and the sound-absorbing layer (140) are separated with the aforementioned acoustic waveguide layer (130) in between.

[0033] Of course, in the case of the present invention as well, the transparent electrode (111) is formed on the surface of the piezoelectric layer (110), and although not all of it is depicted in detail in FIG. 1, the aforementioned transparent electrode (111) should be symmetrically formed not only on the outer surface of the aforementioned piezoelectric layer (110) but also on the opposite surface.

[0034] Generally, in an ultrasonic transducer, the sound-absorbing layer has a certain acoustic impedance difference from the piezoelectric layer (i.e., the piezoelectric layer), and determines the conversion efficiency when energy forms are converted from electricity to sound waves or from sound waves to electricity. In addition, it plays a role in eliminating signal reverberation by maximally dissipating all sound waves that can enter the space opposite to the piezoelectric layer—that is, the space toward the sound-absorbing layer—rather than the space toward the subject, thereby eliminating the resulting reverberation. For this reason, in acoustics, a sound-absorbing layer that performs such a role is also called a backing layer. However, the term "backing layer" emphasizes the meaning of a layer that has a certain acoustic impedance difference from the piezoelectric layer, rather than the role of eliminating reverberation or absorbing sound.

[0035] In this regard, in the photoacoustic-ultrasonic probe provided by the present invention, the acoustic waveguide layer (130) acts as the backing layer just described, while the sound-absorbing layer (140) primarily acts as a sound-absorbing layer that reduces reverberation on the signal.

[0036] Therefore, the acoustic waveguide layer (130) in the present invention must be a material having a predetermined acoustic impedance difference with the piezoelectric layer (110) and simultaneously capable of transmitting sound waves and laser beams without loss. In this regard, glass-based materials such as BK-7 or plastics with transparent properties such as acrylic or polycarbonate may be candidate materials for the acoustic waveguide layer (130). Of course, it is not limited to these materials.

[0037] In addition, another important function of the acoustic waveguide layer (130) in the present invention is to reflect the laser beam at 90°. Therefore, within the acoustic waveguide layer (130) having a slab or square shape, a light-reflecting surface (130R) having a very thin thickness capable of reflecting light well must be formed in the diagonal direction of the cube as shown in FIG. 1. The reason the thickness of the light-reflecting surface (130R) must be as thin as possible is that, according to the basic characteristics and principles of the present invention, sound waves must be transmitted through it. Considering all these requirements, the acoustic waveguide layer (130) required by the present invention can be implemented by joining two glass-based right-angle prisms, such as BK-7, commonly used in optical devices, so that their four sides are in close contact with each other. Of course, one side of the two prisms must be appropriately coated with a dielectric or a metallic material such as gold or aluminum. That is, an important feature of the present invention is that the acoustic waveguide layer (130), which is one of the core components of the present invention, can be easily implemented using two right-angle prisms commonly used in optics.

[0038] Due to this unique structure, the photoacoustic-ultrasonic probe according to the present invention, unlike the prior art (Prior Art 1), does not have the sound-absorbing layer (140) placed in the path of the laser beam, and thus does not generate any image artifacts. This point is very important because, as mentioned earlier, the material applied to the sound-absorbing layer of the current transparent ultrasonic transducer is not transparent like the transparent electrodes commonly used in industry. In other words, no matter how much one attempts to make the sound-absorbing layer transparent, the reality is that it generally exhibits a light absorption rate of 10% or more, which is by no means a small absorption rate value capable of generating significant image artifacts.

[0039] For reference, the probe casing (150) shown in FIG. 1 is not a core component of the present invention and can be modified into an appropriate form as desired for the application. Also, it is obvious that the optical fiber (100) and the laser beam shaper (120) are merely auxiliary elements introduced to explain the role and function of the acoustic waveguide layer (130), which is a core element of the present invention, and are not essential elements required for the implementation of the present invention. Furthermore, although not shown in FIG. 1, a matching layer may be added to the surface of the transparent electrode (111) on the outer surface of the piezoelectric layer (110) to reduce energy loss due to the reflection of sound waves that may occur at the interface between the transparent electrode (111) and the surrounding medium.

[0040] Meanwhile, in FIG. 1, the transparent electrodes (111) formed on the inner and outer surfaces of the piezoelectric layer (110) are shown arranged in a linear shape like a straight line and arranged in a number like an array. However, since the core of the photoacoustic-ultrasonic probe provided by the present invention lies in the concept of an acoustic waveguide layer (130), it is obvious that the shape of the transparent electrodes does not necessarily need to be limited to the shape shown in FIG. 1, and any other shape of electrode can be formed on the surface of the piezoelectric layer (110).

[0041] FIG. 2 is a schematic diagram showing the structure of a photoacoustic-ultrasonic probe based on an ultrasonic array transducer having a ring-shaped electrode in the basic structure of FIG. 1, according to another embodiment of the present invention.

[0042] Referring to FIG. 2, a photoacoustic-ultrasonic probe according to another embodiment of the present invention may include a transparent ultrasonic transducer having a ring-shaped electrode.

[0043] That is, in one embodiment of FIG. 1, straight electrodes are formed along one direction on the surface of the piezoelectric layer (110) to form a so-called linear array transducer, whereas in the embodiment of FIG. 2, ring-shaped transparent electrodes (111R) having different diameters are formed concentrically. By forming these ring-shaped electrodes in a concentric shape, the corresponding ultrasonic transducer can be given acoustic focusing ability.

[0044] Since one embodiment of Fig. 2 differs from Fig. 1 in the shape of the electrode, a detailed description of the remaining components is omitted.

[0045] The photoacoustic-ultrasonic probe according to the present invention may include not only electrodes of this type, but also transparent ultrasonic transducers having electrodes of any other type.

[0046] FIG. 3 is a schematic diagram showing the structure of a photoacoustic-ultrasonic probe based on a transparent ultrasonic array transducer having double-door (DD) electrodes in the basic structure of FIG. 1, according to another embodiment of the present invention.

[0047] Referring to FIG. 3, the transparent electrode formed on the inner and outer surfaces of the piezoelectric layer (110) may be a double-door transparent electrode (111DD). Generally, an array ultrasonic transducer refers to an ultrasonic transducer having a form in which two or more elements are spatially arranged, and the photoacoustic-ultrasonic probe according to one embodiment of the present invention may be implemented to include only two electrodes arranged in a double-door configuration.

[0048] However, in the drawing of Fig. 3, the reason for not forming an electrode at the central point where the two doors face each other and leaving it as a circular empty area is that, generally, the laser beam emitted from the optical fiber (100) exhibits a relatively higher energy flux at its center, so even if the latest transparent electrode technology is applied, the absorption rate of light absorbed by the transparent electrode cannot be made completely zero. In other words, this is to prevent the occurrence of image artifacts that may be caused by the transparent electrode. Therefore, in accordance with this purpose of implementation, in the case of Fig. 2, electrodes can be formed in a form where the innermost point of a plurality of ring-shaped electrodes arranged in a concentric circle is not formed and is left empty.

[0049] In a situation where even image artifacts that can be generated by a transparent electrode must be avoided, the position of the piezoelectric layer (110) can also be moved as in FIG. 4, another embodiment of the present invention.

[0050] FIG. 4 is a schematic diagram showing the structure of a photoacoustic-ultrasonic probe in which the piezoelectric layer and the electrode layer are also completely removed from the path of the laser beam according to another embodiment of the present invention.

[0051] Referring to FIG. 4, the piezoelectric layer (110), which is a key element in detecting photoacoustic waves or emitting ultrasound to perform traditional ultrasonic pulse-echo imaging, and the transparent electrode (111) formed on its inner and outer surfaces can be positioned behind the acoustic waveguide layer (130) like the sound-absorbing layer (140). That is, both the piezoelectric layer (110) and the transparent electrode (111) can be completely excluded from the path of the laser beam.

[0052] In this structure, for example, assuming a process of detecting photoacoustic waves, since the sound wave first passes through the acoustic waveguide layer (130) and reaches the piezoelectric layer (110), it can be seen that, based on physical principles, the acoustic waveguide layer (130) serves not only as a waveguide layer that transmits sound waves but also simultaneously as a matching layer.

[0053] Of course, even in the case of the embodiment shown in FIG. 4, it will be obvious that any other type of electrode can be formed on the surface of the piezoelectric layer (110), as in the embodiments of FIG. 2 and FIG. 3, without having to present the additional drawings related thereto.

[0054] In summary, through this specification, an original probe structure capable of fundamentally preventing image artifacts that have been troublesomely occurring in photoacoustic probes (Prior Art 1) using conventional transparent ultrasonic transducers during the implementation of the hardware has been described. The core of this structure can be seen as including an element called an acoustic waveguide layer, which is basically made of an optically and acoustically transparent material, has a slab or square shape, and has a light-reflecting surface formed diagonally thereto capable of reflecting light.

[0055] A photoacoustic-ultrasonic probe according to one embodiment of the present invention has a slab shape or a square shape and includes an acoustic waveguide layer (130) having a light-reflecting surface (130R) that reflects light irradiated from a light source at an angle inclined with respect to the direction of irradiation of the light; and a piezoelectric layer (110) disposed on one side or the other side of the acoustic waveguide layer (130) such that the light reflected from the light-reflecting surface (130R) of the acoustic waveguide layer (130) travels toward a subject, wherein a transparent electrode (111) is formed in a predetermined area on each side of the piezoelectric layer (110).

[0056] Additionally, the acoustic waveguide layer (130) may include an optically and acoustically transparent material, and the light-reflecting surface (130R) may be formed diagonally opposite to the acoustic waveguide layer (130).

[0057] Additionally, the acoustic waveguide layer (130) includes two optical right-angle prisms joined together, and the two optical right-angle prisms may have a square shape.

[0058] Additionally, the light-reflecting surface (130R) may include at least one of a dielectric reflective film and a metal reflective film.

[0059] Additionally, the acoustic waveguide layer (130) has an acoustic impedance different from that of the piezoelectric layer (110), and can be configured so that photoacoustic waves or ultrasound generated when the light reaches the subject are transmitted to the piezoelectric layer (110) through the acoustic waveguide layer (130).

[0060] Additionally, it may further include an absorbing layer (140) positioned opposite to the piezoelectric layer (110) with respect to the acoustic waveguide layer (130), which attenuates the reverberation that occurs after the photoacoustic-ultrasonic wave is transmitted to the piezoelectric layer (110) through the acoustic waveguide layer (130).

[0061] Additionally, the piezoelectric layer (110) may be positioned so as to be spaced apart from the light transmission path with respect to the acoustic waveguide layer (130).

[0062] In addition, the transparent electrode (111) may be formed in any one of a linear array shape, a concentric ring shape, or a double door shape.

[0063] Additionally, the transparent electrode (111) may be formed in an area other than the region corresponding to the center path of the light.

[0064] Additionally, a matching layer may be further formed on the surface of the piezoelectric layer (110) opposite to the acoustic waveguide layer (130) to mitigate the acoustic impedance mismatch between the piezoelectric layer (110) and the surrounding medium.

[0065] Therefore, it will be obvious to those skilled in the art that some of the embodiments provided in this specification can be modified in various ways and applied in other forms based on the core concept of this acoustic waveguide layer.

[0066] According to the present invention, a photoacoustic-ultrasonic probe according to one embodiment of the present invention has a unique structure capable of completely eliminating the sound-absorbing layer required in conventional transparent ultrasonic transducers from the light path by changing the position of the sound-absorbing layer by adding an element called an acoustic waveguide layer and guiding ultrasound through it.

[0067] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without altering its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. An acoustic waveguide layer having a slab shape or a square shape and having a light-reflecting surface that reflects light irradiated from a light source at an angle inclined with respect to the direction of irradiation of the light; and It includes a piezoelectric layer disposed on one or the other side of the acoustic waveguide, which is arranged so that light reflected from the light-reflecting surface of the acoustic waveguide propagates toward the subject. A photoacoustic-ultrasonic probe having transparent electrodes formed in predetermined regions on both sides of the piezoelectric layer.

2. In Paragraph 1, The above acoustic waveguide layer comprises an optically and acoustically transparent material, and The above light-reflecting surface is formed diagonally opposite to the acoustic waveguide layer, a photoacoustic-ultrasonic probe.

3. In Paragraph 1, The above acoustic waveguide layer includes two optical right-angle prisms joined together, and The two above-mentioned optical right-angle frigates are photoacoustic-ultrasonic probes having a square shape.

4. In Paragraph 1, The above-mentioned light-reflecting surface comprises at least one of a dielectric reflective film and a metal reflective film, in a photoacoustic-ultrasonic probe.

5. In Paragraph 1, The above acoustic waveguide layer has an acoustic impedance different from that of the piezoelectric layer, and A photoacoustic-ultrasonic probe configured such that photoacoustic waves or ultrasound generated when the light reaches a subject are transmitted to the piezoelectric layer through the acoustic waveguide layer.

6. In Paragraph 5, A photoacoustic-ultrasonic probe further comprising a sound-absorbing layer disposed on the opposite side of the piezoelectric layer with respect to the acoustic waveguide layer, which attenuates the reverberation that occurs after the photoacoustic-ultrasonic wave is transmitted to the piezoelectric layer through the acoustic waveguide layer.

7. In Paragraph 1, A photoacoustic-ultrasonic probe in which the piezoelectric layer is positioned so as to be spaced apart from the light transmission path with respect to the acoustic waveguide layer.

8. In Paragraph 1, The above transparent electrode is a photoacoustic-ultrasonic probe formed in any one of a linear array shape, a concentric ring shape, and a double-door shape.

9. In Paragraph 1, The above transparent electrode is a photoacoustic-ultrasonic probe formed outside the region corresponding to the central path of the light.

10. In Paragraph 1, On the surface of the piezoelectric layer opposite to the acoustic waveguide layer, A photoacoustic-ultrasonic probe having a matching layer further formed to mitigate acoustic impedance mismatch between the piezoelectric layer and the surrounding medium.

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