Multi-point focused photoacoustic endoscopic imaging catheter

Abstract

The application discloses a multi-point focusing photoacoustic endoscopic imaging catheter and relates to the technical field of biological imaging. The multi-point focusing photoacoustic endoscopic imaging catheter comprises a shell, a torque coil, an ultrasonic transducer, an optical fiber, a focusing lens, at least one light splitting prism and a mirror which are coaxially arranged along an optical path in sequence, the focusing lens, the at least one light splitting prism, the ultrasonic transducer and the mirror are arranged in the interior of the shell, one end of the optical fiber is fixed in the shell, and a gap is formed between the optical fiber and the focusing lens; each light splitting prism is used for splitting an incident light beam into a reflected first excitation light beam and a transmitted second excitation light beam, the first excitation light beam and the light beam emitted after being reflected by the mirror both converge right above the ultrasonic transducer, and the focal points of the first excitation light beam and the light beam emitted after being reflected by the mirror do not overlap. The application is used for obtaining a larger imaging range and acquiring a complete high-resolution endoscopic image.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bio-imaging, and particularly relates to a multi-point focusing photoacoustic endoscopic imaging catheter. BACKGROUND

[0002] Photoacoustic imaging is a new biomedical imaging method, and its basic principle is that after a biological tissue absorbs pulsed laser, it is partially or completely converted into heat energy, causing pressure to rise, and this pressure propagates in the form of ultrasound waves in the biological tissue, and is then received by an ultrasonic transducer and converted into an electrical signal, which is converted into an image after data processing. Photoacoustic imaging combines the high resolution of optical imaging and the depth advantage of ultrasonic imaging, and can image the structure and function of biological tissues, and has a high clinical application prospect.

[0003] At present, in many applications of photoacoustic endoscopic imaging, the development of microvascular network imaging and atheromatous plaque imaging in the digestive tract is more outstanding. Due to the strong light absorption of hemoglobin, photoacoustic imaging can perform high-sensitivity microvascular imaging without external markers, which is very suitable for non-invasive, accurate and long-term observation of the feeding vessels of digestive tract tumors, and provides important help for early diagnosis and treatment of cancer. For intravascular applications, because photoacoustic imaging technology can obtain tissue composition information combined with ultrasonic information, intravascular photoacoustic imaging can distinguish the structure of the blood vessel wall, the thickness of the fibrous cap and the composition distribution in the plaque, and provide new and powerful basis for the identification and diagnosis of vulnerable plaques in blood vessels. When photoacoustic endoscopic imaging is performed, the catheter needs to be inserted deep into the cavity, such as the digestive tract or blood vessels, and the catheter generally rotates rapidly in the cavity with the movement mechanism, and at the same time, the catheter performs a retraction movement to complete the scanning of the cavity.

[0004] The existing photoacoustic endoscopic catheter mainly uses a single Gaussian light beam as a pulsed excitation light to generate a photoacoustic signal. The pulsed excitation light with this design has only one focal point, and the size of the focal spot and the depth of field need to be balanced during design. Generally speaking, the smaller the focal spot, the shorter the depth of field, and vice versa. The larger the spot, the lower the excitation efficiency, and the worse the image signal-to-noise ratio. The existing technology usually reduces the spot size to achieve better excitation efficiency and improve the signal-to-noise ratio. However, directly reducing the spot size will shorten the imaging depth of field, thereby reducing the imaging range. In actual application, the biological tissue to be measured cannot be distributed in a perfect geometric shape, such as the existence of many folds in the digestive tract, and the blood vessels are not standard circles, so the photoacoustic signal at the defocus position will be poor. The existing technology is difficult to obtain a comprehensive and complete photoacoustic signal. In addition, the existing technology also uses a multi-angle excitation light beam to improve the excitation efficiency and improve the resolution. However, this implementation method has a large volume and is difficult to integrate into a photoacoustic endoscopic catheter, and in the existing technology, the focal points of the multiple light beams are all arranged at the same point, and this method cannot increase the depth of field. SUMMARY

[0005] This application provides a multi-point focusing photoacoustic endoscopic imaging catheter, which forms a dual-focus excitation light in the tiny space of the endoscopic catheter, achieving a longer depth of field with the same spot size, better adapting to physiological wrinkle changes in endoscopic imaging, obtaining a larger imaging range, and realizing high-resolution imaging.

[0006] To achieve the above objectives, this application provides a multi-point focusing photoacoustic endoscopic imaging catheter, comprising a housing, a torque coil, an ultrasonic transducer, and an optical fiber, a focusing lens, at least one beam splitter and a reflector arranged coaxially in sequence. The focusing lens, beam splitter, transducer and reflector are all disposed inside the housing, one end of the optical fiber is fixed inside the housing, and there is an adjustable gap between the optical fiber and the focusing lens.

[0007] The pulsed laser emitted from the optical fiber is focused by the focusing lens after passing through the gap between the optical fiber and the focusing lens. After being focused, the pulsed laser is split into a first excitation beam that is reflected and a second excitation beam that is transmitted after passing through a beam splitter. The first excitation beam is emitted directly, and the second excitation beam is emitted after being reflected by a mirror and intersects with the first excitation beam. The focal points of the first excitation beam and the second excitation beam do not overlap.

[0008] Furthermore, it also includes a first matching tube, a second matching tube, and a support fixed on the outer shell. The outer shell, the first matching tube, and the second matching tube are sequentially fitted from the outside to the inside. One end of the optical fiber passes through the second matching tube. The focusing lens is inserted into the first matching tube. The reflector and at least one beam splitter are all mounted on the support.

[0009] Furthermore, the ultrasonic transducer is a hollow ultrasonic transducer, which is fixed on a beam splitter prism.

[0010] Furthermore, the focal points of both the first and second excitation beams are located on the central axis of the hollow ultrasonic transducer.

[0011] Furthermore, the ultrasonic transducer is embedded in the support and located between the beam splitter and the reflector, and the support has a through hole that cooperates with the ultrasonic transducer.

[0012] Furthermore, it also includes a transparent protective tube, with the outer shell fitted inside the transparent protective tube, and the diameter of the outer shell being smaller than the diameter of the transparent protective tube.

[0013] Furthermore, an ultrasonic coupling agent is filled between the transparent protective tube and the outer shell of the outer shell.

[0014] Furthermore, the outer shell is made of metal.

[0015] Compared with the prior art, the application has the following beneficial effects: the application can increase the depth of field while keeping the light spot at the focal point unchanged or reducing the light spot at the focal point, thereby obtaining a larger imaging range and acquiring more complete and comprehensive photoacoustic signals from biological tissues. The application uses a light splitting prism to form two excitation light beams, without the need to increase the volume of the catheter. Two misaligned focal points are formed by using the light splitting prism and the mirror, so that the total depth of field is lengthened, and a larger range of photoacoustic signals can be obtained, which is more suitable for scanning in various wrinkle environments in the human body lumen and enhances the practicability in clinics. Multiple misaligned focal points are formed by using multiple light splitting prisms and mirrors, further increasing the depth of field. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0017] Figure 1 FIG. 1 is a structural schematic diagram of a multi-point focusing photoacoustic endoscopic imaging catheter in Embodiment 2 of the application;

[0018] Figure 2 FIG. 2 is a depth of field diagram of the imaging catheter with a light splitting prism in Embodiment 2 of the application;

[0019] Figure 3 FIG. 3 is a depth of field diagram of the imaging catheter without a light splitting prism;

[0020] Figure 4 FIG. 4 is a structural schematic diagram of a hollow ultrasonic transducer in the application;

[0021] Figure 5 FIG. 5 is a schematic diagram of a multi-point focusing photoacoustic endoscopic imaging catheter in Embodiment 3 of the application;

[0022] Figure 6 FIG. 6 is a structural schematic diagram of a multi-point focusing photoacoustic endoscopic imaging catheter in Embodiment 4 of the application;

[0023] Figure 7 FIG. 7 is an optical simulation diagram in Embodiment 2 of the application.

[0024] In the figure, 1 is a shell, 2 is a torque coil, 3 is an ultrasonic transducer, 4 is an optical fiber, 5 is a focusing lens, 6 is a light splitting prism, 7 is a mirror, 8 is a first matching tube, 9 is a second matching tube, 10 is a support, and 11 is a transparent protective tube. DETAILED DESCRIPTION

[0025] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of the present application.

[0026] In the description of the present application, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0027] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; for those of ordinary skill in the art, the specific meaning of the above-mentioned terms in the present application can be understood according to the specific circumstances.

[0028] The terms "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise stated, the meaning of "multiple" is two or more.

[0029] The embodiment 1 of the present application provides a multi-point focused photoacoustic endoscopic imaging catheter, which comprises a shell 1, a torque coil 2, an ultrasonic transducer 3, and an optical fiber 4, a focusing lens 5, at least one light splitting prism 6 and a mirror 7 arranged coaxially along the light path in sequence, the focusing lens 5, the at least one light splitting prism 6, the ultrasonic transducer 3 and the mirror 7 are arranged in the interior of the shell 1, one end of the optical fiber 4 is fixed in the shell 1, and there is an adjustable gap between the optical fiber 4 and the focusing lens 5; the other end of the optical fiber 4 is connected to the photoelectric slip ring of a three-dimensional spiral scanning device. One end of the torque coil 2 is fixed at the end of the shell 1, and the other end is fixed in the three-dimensional spiral scanning device. Each light splitting prism 6 is used to split the incident light beam into a reflected first excitation light beam and a transmitted second excitation light beam, the first excitation light beam and the light beam emitted after reflection by the mirror all converge above the ultrasonic transducer 3, the focal points of the respective first excitation light beams do not coincide, and the focal points of the light beams emitted after reflection by the mirror and the first excitation light beams do not overlap.

[0030] The pulsed laser emitted from the optical fiber 4 is focused by the focusing lens 5 after passing through the gap between the optical fiber 4 and the focusing lens 5, and the focused pulsed laser passes through the light splitting prism 6 and is reflected by the first excitation light beam and transmitted by the second excitation light beam. The second excitation light beam is reflected by the mirror 7 and emitted and intersects with the first excitation light beam. The intersected light beam is reflected to the sample to excite the ultrasonic signal. The ultrasonic signal is converted into an electrical signal by the ultrasonic transducer 3 and transmitted to the acquisition system by the coaxial cable. The ultrasonic transducer 3 completes the ultrasonic imaging independently by emitting and receiving. If there are multiple light splitting prisms 6 in the optical path, the second laser beam transmitted from the first light splitting prism 6 will be incident to the second light splitting prism 6. The light beam is again split into the first excitation light beam reflected by the light splitting prism 6 and the second excitation light beam emitted after being reflected by the mirror. The first laser beam reflected by the light splitting prism 6 and the light beam emitted after being reflected by the mirror are both intersected above the ultrasonic transducer 3, and the focal points of each light beam do not overlap.

[0031] Referring to Figure 1 , 7 , the embodiment 2 of the present application provides a multi-point focused photoacoustic endoscopic imaging catheter, which comprises a transparent protective tube 11, a shell 1, a torque coil 2, an ultrasonic transducer 3, a first matching tube 8, a second matching tube 9, a support 10 fixed in the shell 1, and an optical fiber 4, a focusing lens 5, a light splitting prism 6 and a mirror 7 coaxially arranged along the optical path in sequence. One end of the torque coil 2 is fixed at the end of the shell 1, and the other end is fixed in a three-dimensional spiral scanning device. The ultrasonic transducer 3 is a hollow ultrasonic transducer as shown in Figure 4 . The ultrasonic transducer 3 comprises a matching layer, a piezoelectric material and a backing connected in sequence. The ultrasonic transducer 3 can receive ultrasonic waves propagating in biological tissues and convert them into electrical signals. The hollow ultrasonic transducer is fixed on the light splitting prism 6.

[0032] The shell 1, the first matching tube 8 and the second matching tube 9 are coaxially sleeved from outside to inside. The shell 1 is a tubular structure, and the material can be but is not limited to metal. One end of the optical fiber 4 penetrates out of the second matching tube 9, and the other end is connected to the photoelectric slip ring of the three-dimensional spiral scanning device. The focusing lens 5 is inserted into the first matching tube 8, and there is a gap between the optical fiber 4 and the focusing lens 5. The optical fiber 4 is sleeved in the first matching tube 8, which can increase the diameter of the optical fiber end. The first matching tube 8 and the second matching tube 9 are coaxially sleeved, which ensures that the optical fiber 4 and the focusing lens 5 are coaxially placed and also fixes the gap between the optical fiber 4 and the focusing lens 5. The outer diameter of the first matching tube 8 is adapted to the size of the shell 1, which is convenient for placing in the shell 1. The mirror 7 and the light splitting prism 6 are both fixed on the support 10.

[0033] The distribution of the two focal points can be controlled by changing the interval between the mirror 7 and the light splitting prism 6, the interval between the optical fiber 4 and the focusing lens 5, and the angle of the mirror 7. The shell 1 is arranged in the transparent protective tube 11, the diameter of the shell 1 is smaller than the diameter of the transparent protective tube 11, and the shell 1 can rotate in the transparent protective tube 11; the transparent protective tube 11 and the shell 1 are filled with an ultrasonic coupling agent.

[0034] The pulsed laser emitted from the optical fiber 4 is focused by the focusing lens 5 after passing through the gap between the optical fiber 4 and the focusing lens 5, and is split into the reflected first excitation light beam and the transmitted second excitation light beam after passing through the light splitting prism 6. The first excitation light beam directly exits after passing through the central opening of the ultrasonic transducer 3, and the second excitation light beam exits after being reflected by the mirror 7 and intersects with the first excitation light beam. The focal points of the first excitation light beam and the second excitation light beam do not overlap, and both focal points are located on the central axis of the ultrasonic transducer 3. The intersected light beams reflect on the sample to excite the ultrasonic signal, the ultrasonic signal is converted into an electrical signal by the ultrasonic transducer 3 and is transmitted to the acquisition system by the coaxial cable, and the ultrasonic transducer 3 completes the ultrasonic imaging independently by emitting and receiving. The first excitation light beam coincides with the sound beam, and the other excitation light beam intersects with the sound beam at a certain angle.

[0035] Referring to Figure 2 and Figure 3 respectively are an imaging catheter with a light splitting prism and an imaging catheter without a light splitting prism, Figure 3 the catheter has only one focal point, and after the light splitting prism is added (as shown in Figure 2 ), the catheter has two focal points, and the depth of field is increased, so the imaging catheter with the light splitting prism can overcome the problem of limited depth of field range of the single focal point pulsed laser.

[0036] Referring to Figure 5 , embodiment 3 of the present application provides a multi-point focused photoacoustic endoscopic imaging catheter, which comprises a transparent protective tube 11, a shell 1, a torque coil 2, an ultrasonic transducer 3, a first matching tube 8, a second matching tube 9, a support 10 fixed on the shell 1, and an optical fiber 4, a focusing lens 5, a light splitting prism 6 and a mirror 7 arranged coaxially along the light path in sequence. One end of the torque coil 2 is fixed at the end of the shell 1, and the other end is fixed in a three-dimensional spiral scanning device. The shell 1 is a tubular structure made of metal. The shell 1, the first matching tube 8 and the second matching tube 9 are coaxially sleeved from outside to inside. One end of the optical fiber 4 penetrates out of the second matching tube 9, the other end of the optical fiber 4 is connected to the photoelectric slip ring of the three-dimensional spiral scanning device, the focusing lens 5 is inserted into the first matching tube 8, and there is a gap between the optical fiber 4 and the focusing lens 5. The mirror 7 and the light splitting prism 6 are both fixed on the support 10, and the ultrasonic transducer 3 is embedded in the support 10 and located between the light splitting prism 6 and the mirror 7.

[0037] The pulsed laser light emitted from the optical fiber 4 is focused by the focusing lens 5 after passing through the gap between the optical fiber 4 and the focusing lens 5, and the focused pulsed laser light is divided into the reflected first excitation light beam and the transmitted second excitation light beam after passing through the light splitting prism 6, the first excitation light beam is directly emitted, and the second excitation light beam is reflected by the mirror 7 and emitted to intersect with the first excitation light beam, the focal points of the first excitation light beam and the second excitation light beam do not overlap, and both focal points are located on the central axis of the ultrasonic transducer 3. The intersected light beams reflect on the sample to excite the ultrasonic signal, the ultrasonic signal is converted into an electric signal by the ultrasonic transducer 3 and transmitted to the acquisition system by the coaxial cable, and the ultrasonic transducer 3 independently completes ultrasonic imaging by emitting and receiving. The first excitation light beam and the second excitation light beam form an angle with the sound beam.

[0038] Referring to Figure 6 The embodiment 4 of the present application provides a multi-point focused photoacoustic endoscopic imaging catheter, which comprises a transparent protective tube 11, a shell 1, a torque coil 2, an ultrasonic transducer 3, a first matching tube 8, a second matching tube 9, a support 10 fixed in the shell 1, and an optical fiber 4, a focusing lens 5, two light splitting prisms 6 and a mirror 7 coaxially arranged along the light path in sequence. The shell 1, the first matching tube 8 and the second matching tube 9 are coaxially sleeved from outside to inside, one end of the torque coil 2 is fixed at the end of the shell 1, and the other end is fixed in a three-dimensional spiral scanning device. The shell 1 is a tubular structure made of metal. One end of the optical fiber 4 penetrates out of the second matching tube 9, and the other end is connected to the photoelectric slip ring of the three-dimensional spiral scanning device, the focusing lens 5 is inserted into the first matching tube 8, and there is a gap between the optical fiber 4 and the focusing lens 5. The mirror 7 and the two light splitting prisms 6 are fixed on the support 10, and the ultrasonic transducer 3 is fixed on the light splitting prism 6 close to the focusing lens 5.

[0039] The pulsed laser light emitted from the optical fiber 4 is focused by the focusing lens 5 after passing through the gap between the optical fiber 4 and the focusing lens 5, and the focused pulsed laser light is divided into the reflected first excitation light beam and the transmitted second excitation light beam after passing through the first light splitting prism 6, the first excitation light beam directly emits after passing through the central opening of the transducer, and the second excitation light beam is again divided into the reflected first excitation light beam and the transmitted second excitation light beam after passing through the second light splitting prism 6, the first excitation light beam reflected by the second light splitting prism 6 intersects with the first excitation light beam reflected by the first light splitting prism 6, and the second excitation light beam transmitted from the second light splitting prism 6 is reflected by the mirror 7 and emitted to intersect with the first excitation light beam, the three light beams intersect directly above the ultrasonic transducer 3 and the focal points do not overlap, and the three focal points are located on the central axis of the ultrasonic transducer 3. The intersected light beams reflect on the sample to excite the ultrasonic signal, the ultrasonic signal is converted into an electric signal by the ultrasonic transducer 3 and transmitted to the acquisition system by the coaxial cable, and the ultrasonic transducer 3 independently completes ultrasonic imaging by emitting and receiving. In this way, three focal points can be generated, further increasing the depth of field.

[0040] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any change or replacement within the technical scope disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A multi-point focused photoacoustic endoscopic imaging catheter, comprising: The device comprises a shell, a torque coil, an ultrasonic transducer, and an optical fiber, a focusing lens, at least one light splitting prism and a mirror arranged coaxially along an optical path in sequence, the focusing lens, the at least one light splitting prism, the ultrasonic transducer and the mirror are arranged inside the shell, one end of the optical fiber is fixed in the shell, and an adjustable gap is provided between the optical fiber and the focusing lens; Each light splitting prism is used for splitting the incident light beam into a reflected first excitation light beam and a transmitted second excitation light beam, the first excitation light beam directly irradiates the biological tissue, and the second excitation light beam irradiates the biological tissue after being reflected by the mirror, the first excitation light beam and the light beam irradiated by the mirror after being reflected by the mirror both converge right above the ultrasonic transducer, the focal points of the first excitation light beam and the light beam irradiated by the mirror after being reflected by the mirror are misaligned and both are located on the central axis of the ultrasonic transducer; The device further comprises a support fixed in the shell, the mirror and the at least one light splitting prism are arranged on the support; The ultrasonic transducer is embedded in the support and located between the light splitting prism and the mirror. The distribution of the two focal points can be controlled by changing the interval between the mirror and the light splitting prism, the interval between the optical fiber and the focusing lens, and the angle of the mirror.

2. The multi-point focused photoacoustic endoscopic imaging catheter of claim 1, wherein, The device further comprises a first matching tube and a second matching tube, the shell, the first matching tube and the second matching tube are sequentially sleeved from outside to inside, one end of the optical fiber penetrates out of the second matching tube, and the focusing lens is inserted into the first matching tube.

3. The multi-point focused photoacoustic endoscopic imaging catheter of claim 2, wherein, The ultrasonic transducer is a hollow ultrasonic transducer.

4. The multi-point focused photoacoustic endoscopic imaging catheter of claim 3, wherein, The focal points of the first excitation light beam and the second excitation light beam are both located on the central axis of the hollow ultrasonic transducer.

5. The multi-point focused optoacoustic endoscopic imaging catheter of claim 2, wherein, A through hole matched with the ultrasonic transducer is formed in the support.

6. The multi-point focused photoacoustic endoscopic imaging catheter of claim 1, wherein, The device further comprises a transparent protective tube, the shell is sleeved in the transparent protective tube, and the diameter of the shell is smaller than the diameter of the transparent protective tube.

7. The multi-point focused photoacoustic endoscopic imaging catheter of claim 6, wherein, An ultrasonic coupling agent is filled between the transparent protective tube and the shell.

8. The multi-point focused photoacoustic endoscopic imaging catheter of claim 1, wherein The shell is made of metal.

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