Integrated fiber optic ultrasonic endoscope and preparation method thereof

Abstract

The present invention discloses an integrated fiber optic ultrasonic endoscope and a preparation method, which belong to the field of ultrasonic sensors. It includes a multi-core optical fiber, a dielectric film, a strip sensing layer, a hybrid excitation wedge tip, a sensitivity enhancement column and an endoscope sheath. The sensitivity enhancement column and the strip sensing layer achieve double sensitivity, which greatly improves the sensitivity of lateral sensing, and achieves good directionality on the membrane plane through the strip structure of the sensing layer. The hybrid excitation wedge tip achieves double and four times the side sound field excitation of the traditional single-mode optical fiber in two intensity directions respectively. The present invention solves the problems of existing fiber optic ultrasonic sensors such as large size, low excitation power, low integration and low sensitivity.

Description

Technical Field

[0001] The present invention belongs to the field of ultrasonic detectors, and more specifically, relates to an integrated fiber optic ultrasonic endoscope and a preparation method thereof. Background Art

[0002] Cardiovascular disease is the leading cause of death worldwide, with 330 million people in China suffering from cardiovascular and cerebrovascular diseases. Intravascular ultrasound (IVUS), which uses a catheter to insert an ultrasound probe into the blood vessels to obtain vascular images and guide interventional treatment, has become the gold standard for coronary artery examinations.

[0003] Existing IVUS devices primarily use piezoelectric ceramic ultrasonic transducers, combined with phased array or mechanically rotating ultrasonic catheters. However, piezoelectric probes face the problem of bandwidth, size, and sensitivity being mutually restricted, making it difficult to simultaneously meet the requirements of miniaturization, high resolution, and high penetration depth, limiting their development in precision diagnosis and treatment. Therefore, there is an urgent need to conduct research on all-fiber, small-size, highly sensitive ultrasonic sensing technology and high-resolution ultrasonic imaging technology to break through the bottleneck of high-integration, high-penetration, high-definition imaging performance and provide innovative technologies for intravascular ultrasound imaging.

[0004] In recent years, ultrasonic endoscopes based on fiber-optic ultrasonic transducers have been favored by researchers due to their small size and large bandwidth. Many all-optical ultrasonic endoscope solutions have been reported in recent years, primarily using two or more optical fibers for ultrasonic emission and detection, which keeps the endoscope diameter at the millimeter level and makes further miniaturization difficult. Some researchers have also proposed using a single double-clad optical fiber for integrated transceiver lateral excitation, but the excitation energy is low and requires a bulky acoustic reflector for lateral detection. Therefore, there is an urgent need for a fiber-optic ultrasonic endoscope that combines small size, high integration, high ultrasonic excitation, and high lateral sensitivity. Summary of the Invention

[0005] In view of the defects of the prior art, the purpose of the present invention is to provide an integrated fiber optic ultrasonic endoscope and a preparation method, aiming to solve the problems of existing fiber optic ultrasonic sensors such as large size, low integration, low excitation sound pressure and low lateral sensitivity.

[0006] To achieve the above objectives, the first aspect of the present invention provides an integrated fiber optic ultrasonic endoscope, comprising a multi-core optical fiber, a dielectric film, a strip sensing layer, a hybrid excitation wedge tip, a sensitivity enhancement column and an endoscope sheath.

[0007] The multi-core optical fiber includes a central core and multiple cores uniformly surrounding the central core, wherein the central core is used to transmit detection light, and the remaining cores are used to transmit excitation light.

[0008] The dielectric film is located on the end face of the multi-core optical fiber, and the dielectric film includes a first dielectric film and a second dielectric film. The strip sensing layer and the hybrid excitation wedge tip are both located between the first dielectric film and the second dielectric film. The geometric center of the strip sensing layer coincides with the geometric center of the multi-core optical fiber. The cross section of the strip sensing layer covers the cross section of the central fiber core. The hybrid excitation wedge tip is located on the side of the strip sensing layer. The direction of the wedge tip slope is along the direction of the long side extension of the strip sensing layer. The cross section of the hybrid excitation wedge tip covers at least one fiber core. The sensitivity enhancement column is located on the other side of the second dielectric film and is located in the projection area of ​​the strip sensing layer (103) on the second dielectric film. The endoscopic sheath (106) is used to isolate the dielectric film (102), the strip sensing layer (103), the hybrid excitation wedge tip (104), and the sensitivity enhancement column (105) from the outside world.

[0009] During operation, the detection light is transmitted to the first dielectric film through the central core of the multi-core optical fiber, part of the detection light is returned, and the other part of the detection light is transmitted through the first dielectric film, transmitted to the second dielectric film through the strip sensing layer, and reflected and returned. The first dielectric film, the second dielectric film and the strip sensing layer together form an FP cavity, and the reflected light forms multi-beam interference in the FP cavity; the excitation light is transmitted to the first dielectric film through the other cores of the multi-core optical fiber, transmitted through the first dielectric film and absorbed by the mixed excitation wedge tip, thereby exciting a lateral pulse ultrasonic signal, and the lateral pulse ultrasonic signal interacts with the object to be measured to generate an echo signal to be measured; the echo signal acts on the sensitivity enhancement column and the FP cavity, thereby modulating the FP cavity length, and finally modulating the lateral pulse ultrasonic signal onto the detection light that forms multi-beam interference in the FP cavity, and realizing lateral detection of ultrasound by detecting the intensity of the detection light.

[0010] Preferably, the multi-core optical fiber is a seven-core optical fiber.

[0011] Preferably, the hybrid excitation wedge tip includes four wedge tip units, which are distributed in pairs on both sides of the strip-shaped sensing layer, and the inclined surfaces of the wedge tip units on the same side face opposite directions.

[0012] Preferably, the detection light signal is a C-band continuous laser; the excitation light signal is a pulsed laser with a wavelength of 1064 nm.

[0013] Preferably, the reflectivity of the dielectric film in the C band is 90% to 98%; and the reflectivity in the 1000-1100 nm band is less than 10%.

[0014] Preferably, the endoscope sheath includes an endoscope protective wall and a probe sheath, the endoscope protective arm is wrapped around the multi-core optical fiber, and the probe sheath includes an ultrasonic coupling liquid for wrapping and protecting the sensitization column and transmitting the ultrasonic signal.

[0015] The present invention also provides a method for preparing an integrated fiber optic ultrasonic endoscope, comprising the following steps:

[0016] S1, coating the side wall of the multi-core optical fiber with a flexible material;

[0017] S2. Cut the end face of the multi-core optical fiber flat and rinse it with deionized water;

[0018] S3, alternately depositing a silicon dioxide film and a titanium dioxide film as a first dielectric film by magnetron sputtering;

[0019] S4, using a two-photon polymerization 3D printing process to print a strip-shaped sensing layer using PDMS photoresist;

[0020] S5, mixing PDMS photoresist and carbon black powder, and curing them into a hybrid excitation wedge tip using a two-photon polymerization 3D printing process;

[0021] S6, alternately depositing a silicon dioxide film and a titanium dioxide film as a second dielectric film by magnetron sputtering;

[0022] S7, replacing IPS photoresist and using two-photon polymerization 3D printing process to prepare IPS columns as sensitization columns;

[0023] S8. Fix the multi-core optical fiber with a fiber clamp. Under a microscope, control the translation stage to insert the end face of the multi-core optical fiber into the protective cover filled with ultrasonic coupling liquid. Apply UV glue at the contact position between the protective cover and the edge of the optical fiber, and cure it under UV light for 1 minute.

[0024] Preferably, the thickness of the strip-shaped sensing layer is 20 μm.

[0025] Preferably, the wedge angle is 35 degrees.

[0026] Preferably, the sensitizing column is a cylinder with a length of 100um to 300um and a diameter of 10um to 20um. When the sensitizing column is acted upon by ultrasound, it generates violent vibrations and deformations near the resonant frequency. For ultrasonic signals transmitted from the side, it mainly manifests as lateral vibrations and torsion of the column. The vibrations and torsion are further transmitted to the strip sensing layer, thereby increasing the thickness of the sensing cavity layer and the refractive index change, and then increasing the intensity change of the reflected detection light, thereby achieving a sensitization effect. The height, diameter, and Young's modulus of the sensitizing column are designed according to the measurement requirements to adjust the sensing sensitivity and frequency band range; the higher the height, the smaller the diameter, the smaller the Young's modulus, and the higher the sensitivity. The higher the sensitivity, the relatively lower and narrower the frequency band, so a suitable sensing system can be selected according to different measurement targets.

[0027] Preferably, the endoscope sheath is made of a flexible material with good biocompatibility, wrapped around the optical fiber, and has an outer diameter of 270 μm.

[0028] Preferably, a seven-core optical fiber is used with a coating diameter of 250um, a cladding diameter of 150um, a core diameter of 8um, and a core spacing of 42um.

[0029] Compared with the prior art, the above technical solutions proposed by the present invention can achieve the following

[0030] Beneficial effects:

[0031] 1. The present invention realizes the integration of lateral ultrasonic excitation and detection under the condition of silent reflectors, and greatly improves the lateral excitation sound pressure and lateral response of the fiber optic ultrasonic probe. The sensitivity enhancement column and the strip sensing layer achieve dual sensitivity enhancement, greatly improving the sensitivity of lateral sensing, and the strip structure of the sensing layer achieves good directionality on the membrane plane. The hybrid excitation wedge tip covers 2 and 4 fiber cores in two directions, respectively, thereby achieving double and quadruple the lateral sound field excitation of traditional single-mode optical fibers in two intensity directions. This greatly improves the resolution of fiber optic endoscope imaging.

[0032] 2. This invention integrates ultrasonic excitation and detection on a single optical fiber. The probe is approximately 270 μm in diameter, comparable to a seven-core fiber, enabling deep detection into smaller blood vessels. Furthermore, this single fiber eliminates inter-fiber crosstalk, resolving the issues of larger size and severe inter-fiber crosstalk associated with conventional multi-fiber ultrasonic probes.

[0033] 3. The integrated fiber optic ultrasonic endoscope of the present invention has the advantages of small structure, strong flexibility and good biocompatibility, and can be well applied in biomedical scenarios.

[0034] 4. The materials of the device of the present invention are easy to obtain, the entire device is easy to implement, the cost is low, and the operation is reliable. The preparation method of the device is highly repeatable and can be mass-produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a structural diagram of the integrated fiber optic ultrasonic endoscope provided by the present invention;

[0036] Figure 2 This is a top view of the integrated fiber optic ultrasonic endoscope provided by the present invention;

[0037] Figure 3 This is a connection diagram of the integrated fiber optic ultrasonic endoscope and the optical transceiver system provided by the present invention. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0039] The invention provides an integrated fiber optic ultrasonic endoscope, comprising a multi-core optical fiber, a dielectric film, a strip-shaped sensing layer, a hybrid excitation wedge tip, a sensitivity enhancement column and an endoscope sheath.

[0040] The multi-core optical fiber includes a central core and multiple cores uniformly surrounding the central core, wherein the central core is used to transmit detection light, and the remaining cores are used to transmit excitation light.

[0041] The dielectric film is located on the end face of the multi-core optical fiber, and the dielectric film includes a first dielectric film and a second dielectric film. The strip sensing layer and the hybrid excitation wedge are both located between the first dielectric film and the second dielectric film. The geometric center of the strip sensing layer coincides with the geometric center of the multi-core optical fiber. The cross section of the strip sensing layer covers the cross section of the central core. The hybrid excitation wedge is located on the side of the strip sensing layer, the direction of the wedge slope is along the direction of extension of the long side of the strip sensing layer, and the cross section of the hybrid excitation wedge covers at least one core. The sensitivity enhancement column is located on the outer side of the second dielectric film and above the corresponding strip sensing layer. The endoscopic sheath is used to protect and isolate the dielectric film, the strip sensing layer, the hybrid excitation wedge, and the sensitivity enhancement column at the end face of the optical fiber.

[0042] During operation, the detection light is transmitted to the first dielectric film through the central core of the multi-core optical fiber, part of the detection light is returned, and the other part of the detection light is transmitted through the first dielectric film, transmitted to the second dielectric film through the strip sensing layer, and reflected and returned. The first dielectric film, the second dielectric film and the strip sensing layer together form an FP cavity, and the reflected light forms multi-beam interference in the FP cavity; the excitation light is transmitted to the first dielectric film through the other cores of the multi-core optical fiber, transmitted through the first dielectric film and absorbed by the mixed excitation wedge tip, thereby exciting a lateral pulse ultrasonic signal, and the lateral pulse ultrasonic signal interacts with the object to be measured to generate an echo signal to be measured; the echo signal acts on the sensitivity enhancement column and the FP cavity, thereby modulating the FP cavity length, and finally modulating the lateral pulse ultrasonic signal onto the detection light that forms multi-beam interference in the FP cavity, and realizing lateral detection of ultrasound by detecting the intensity of the detection light.

[0043] Specifically, the multi-core optical fiber is a seven-core optical fiber.

[0044] Specifically, the hybrid excitation wedge includes four wedge units, which are distributed in pairs on both sides of the strip-shaped sensing layer, and the inclined surfaces of the wedge units on the same side face opposite directions.

[0045] Specifically, the detection light signal is a C-band continuous laser; the excitation light signal is a pulsed laser with a wavelength of 1064 nm.

[0046] Specifically, the reflectivity of the dielectric film in the C band is 90% to 98%; and the reflectivity in the 1000-1100 nm band is less than 10%.

[0047] Specifically, the endoscope sheath includes an endoscope protective wall and a probe sheath. The endoscope protective arm is wrapped around the multi-core optical fiber, and the probe sheath includes an ultrasonic coupling liquid for wrapping and protecting the sensitization column and transmitting the ultrasonic signal.

[0048] The present invention also provides a method for preparing an integrated fiber optic ultrasonic endoscope, comprising the following steps:

[0049] S1, coating the side wall of the multi-core optical fiber with a flexible material;

[0050] S2. Cut the end face of the multi-core optical fiber flat and rinse it with deionized water;

[0051] S3, alternately depositing a silicon dioxide film and a titanium dioxide film as a first dielectric film by magnetron sputtering;

[0052] S4, using a two-photon polymerization 3D printing process to print a strip-shaped sensing layer using PDMS photoresist;

[0053] S5, mixing PDMS photoresist and carbon black powder, and curing them into a hybrid excitation wedge tip using a two-photon polymerization 3D printing process;

[0054] S6, alternately depositing a silicon dioxide film and a titanium dioxide film as a second dielectric film by magnetron sputtering;

[0055] S7, replacing IPS photoresist and using two-photon polymerization 3D printing process to prepare IPS columns as sensitization columns;

[0056] S8. Fix the multi-core optical fiber with a fiber clamp. Under a microscope, control the translation stage to insert the end face of the multi-core optical fiber into the protective cover filled with ultrasonic coupling liquid. Apply UV glue at the contact position between the protective cover and the edge of the optical fiber, and cure it under UV light for 1 minute.

[0057] Specifically, the thickness of the strip-shaped sensing layer is 20 μm.

[0058] Specifically, the wedge angle is 35 degrees.

[0059] Specifically, the sensitivity-enhancing column is a cylinder with a length of 100um to 300um and a diameter of 10um to 20um. When the sensitivity-enhancing column interacts with ultrasound, it produces violent vibrations and deformations near the resonant frequency. For ultrasonic signals transmitted from the side, this is mainly manifested as lateral vibration and torsion of the column. This vibration and torsion is further transmitted to the strip sensing layer, thereby increasing the thickness of the sensing cavity layer and the refractive index change, and further increasing the intensity change of the reflected detection light, thereby achieving a sensitivity-enhancing effect. The height, diameter, and Young's modulus of the sensitivity-enhancing column are designed according to measurement requirements to adjust the sensing sensitivity and frequency band range; the higher the height, the smaller the diameter, the smaller the Young's modulus, and the higher the sensitivity. The higher the sensitivity, the relatively lower and narrower the frequency band. Therefore, the appropriate sensing system can be selected according to different measurement targets.

[0060] Specifically, the endoscope sheath is made of a flexible material with good biocompatibility, wrapped around the optical fiber, and has an outer diameter of 270 μm.

[0061] Preferably, a seven-core optical fiber is used with a coating diameter of 250um, a cladding diameter of 150um, a core diameter of 8um, and a core spacing of 42um.

[0062] Example

[0063] Figure 1 This is a structural diagram of the integrated fiber optic ultrasonic endoscope provided in this embodiment. Figure 1 As shown, it includes a multi-core optical fiber 101 (seven-core optical fiber), a dielectric film 102, a strip sensing layer 103, a hybrid excitation wedge tip 104, a sensitivity enhancement column 105, and an endoscope sheath 106.

[0064] Figure 2 FIG. 1 is a top view of the integrated fiber optic ultrasonic endoscope provided by the present invention. Figure 2 As shown, the cores of the seven-core optical fiber are divided into a sensing core 1012 and six detection cores 1011. The strip sensing layer 103 is arranged as shown in the figure, covering the sensing core 1012 but avoiding the detection core 1011. The sensitivity enhancement column 105 is prepared above the strip sensing layer 103, and the preparation position is one core diameter distance away from the sensing core 1012 and centered relative to the short side of the strip sensing layer.

[0065] Figure 3 This is a connection diagram of the integrated fiber optic ultrasonic endoscope and the optical transceiver system provided by the present invention, such as Figure 3 As shown, the signal light emitting unit 2 and the excitation light emitting unit 3 send the detection light signal and the excitation light signal to the integrated fiber optic ultrasonic endoscope 1, and the light receiving unit 4 is used to receive the reflected light signal from the integrated fiber optic ultrasonic endoscope 1 and transmit it to the optical signal processing unit 5 to demodulate and analyze the sound signal to be measured.

[0066] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it is easy for those skilled in the art to understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An integrated fiber optic ultrasonic endoscope, characterized in that: The invention comprises a multi-core optical fiber (101), a dielectric film (102), a strip-shaped sensing layer (103), a hybrid excitation wedge tip (104), a sensitivity enhancement column (105), and an endoscope sheath (106); the multi-core optical fiber (101) comprises a central core and a plurality of cores uniformly surrounding the central core, the central core is used to transmit detection light, and the remaining cores are used to transmit excitation light; the dielectric film (102) is located at the end face of the multi-core optical fiber (101), the dielectric film (102) comprises a first dielectric film and a second dielectric film, the strip-shaped sensing layer (103) and the hybrid excitation wedge tip (104) are both located between the first dielectric film and the second dielectric film, and the strip-shaped sensing layer (103) is located at the end face of the multi-core optical fiber (101). The center of the strip sensing layer (103) coincides with the geometric center of the multi-core optical fiber (101); the cross section of the strip sensing layer (103) covers the cross section of the central fiber core; the hybrid excitation wedge tip (104) is located on the side of the strip sensing layer (103); the wedge tip slope is oriented along the direction of the long side extension of the strip sensing layer (103); the cross section of the hybrid excitation wedge tip (104) covers at least one fiber core; the sensitivity enhancement column (105) is placed on the other side of the second dielectric film and is located in the projection area of ​​the strip sensing layer (103) on the second dielectric film; the endoscopic sheath (106) is used to isolate the dielectric film (102), the strip sensing layer (103), the hybrid excitation wedge tip (104), and the sensitivity enhancement column (105) from the outside world; During operation, the detection light is transmitted to the first dielectric film through the central core of the multi-core optical fiber (101), a part of the detection light returns, and the other part of the detection light transmits the first dielectric film, transmits to the second dielectric film through the strip sensing layer (103), and is reflected and returned. The first dielectric film, the second dielectric film and the strip sensing layer together form an FP cavity, and the reflected light forms multi-beam interference in the FP cavity; the excitation light is transmitted to the first dielectric film through the other cores of the multi-core optical fiber (101), transmits through the first dielectric film and is absorbed by the mixed excitation wedge tip (104), thereby exciting a lateral pulse ultrasonic signal, and the lateral pulse ultrasonic signal acts on the object to be measured to generate an echo signal to be measured; the echo signal acts on the sensitivity enhancement column (105) and the FP cavity, thereby modulating the FP cavity length, and finally modulating the lateral pulse ultrasonic signal to the detection light that forms the multi-beam interference in the FP cavity, and realizing lateral detection of ultrasound by detecting the intensity of the detection light.

2. The integrated fiber optic ultrasonic endoscope according to claim 1, characterized in that: The multi-core optical fiber (101) is a seven-core optical fiber.

3. The integrated fiber optic ultrasonic endoscope according to claim 2, characterized in that: The hybrid excitation wedge tip (104) includes four wedge tip units, which are distributed in pairs on both sides of the strip-shaped sensing layer (103), and the inclined surfaces of the wedge tip units on the same side face opposite directions.

4. The integrated fiber optic ultrasonic endoscope according to claim 1, characterized in that: The detection light signal is a C-band continuous laser; the excitation light signal is a pulsed laser with a wavelength of 1064nm.

5. The integrated fiber optic ultrasonic endoscope according to claim 1, characterized in that: The reflectivity of the dielectric film (102) in the C band is 90% to 98%; and the reflectivity in the 1000-1100 nm band is less than 10%.

6. The integrated fiber optic ultrasonic endoscope according to claim 1, characterized in that: The endoscope sheath (106) comprises an endoscope protective wall and a probe sheath. The endoscope protective wall is wrapped around the multi-core optical fiber (101). The probe sheath comprises an ultrasonic coupling liquid for wrapping and protecting the sensitization column (105) and transmitting ultrasonic signals.

7. A method for preparing the integrated fiber optic ultrasonic endoscope according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, coating the side wall of the multi-core optical fiber (101) with a flexible material; S2, cutting the end face of the multi-core optical fiber (101) flat and washing it with deionized water; S3, alternately depositing a silicon dioxide film and a titanium dioxide film as a first dielectric film by magnetron sputtering; S4, using a two-photon polymerization 3D printing process to print a strip-shaped sensing layer (103) using PDMS photoresist; S5, mixing PDMS photoresist and carbon black powder, and curing them into a hybrid excitation wedge tip (104) using a two-photon polymerization 3D printing process; S6, alternately depositing a silicon dioxide film and a titanium dioxide film as a second dielectric film by magnetron sputtering; S7, replacing IPS photoresist, using two-photon polymerization 3D printing process to prepare IPS column as sensitization column (105); S8. Fix the multi-core optical fiber (101) with an optical fiber clamp, control the translation stage under a microscope to insert the end face of the multi-core optical fiber (101) into a protective sleeve filled with ultrasonic coupling liquid, apply ultraviolet glue at the contact position between the protective sleeve and the edge of the optical fiber, and cure it under ultraviolet light for 1 minute.

8. The preparation method according to claim 7, characterized in that The thickness of the strip-shaped sensing layer (103) is 20 μm.

9. The preparation method according to claim 7, characterized in that The wedge angle is 35 degrees.

10. The preparation method according to claim 7, characterized in that The sensitization column (105) is a cylinder with a length of 100um to 300um and a diameter of 10um to 20um.

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