Integrated optical fiber ultrasonic endoscope and preparation method

Abstract

The invention discloses an integrated optical fiber ultrasonic endoscope and a preparation method, and belongs to the field of ultrasonic sensors. Comprising a multi-core optical fiber, a dielectric film, a strip-shaped sensing layer, a mixed excitation inclined wedge, a sensibilization column and an endoscopic sheath. Double sensibilization is achieved through the sensibilization columns and the strip-shaped sensing layer, the sensitivity of lateral sensing is greatly improved, and good directivity is achieved on a film layer plane through the strip-shaped structure of the sensing layer. And the mixed excitation inclined wedges respectively realize side sound field excitation which is double and quadruple of that of the traditional single-mode optical fiber in two intensity directions. The problems that an existing optical fiber ultrasonic sensor is large in size, low in excitation power, low in integration level and low in sensitivity are solved.

Description

Technical Field

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

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

[0003] Existing IVUS devices mainly use piezoelectric ceramic ultrasonic transducers combined with phased array or mechanical rotary ultrasonic catheters. However, piezoelectric probes have 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, it is urgent to conduct research on all-fiber small-size, highly sensitive ultrasonic sensing technology and high-resolution ultrasonic imaging technology, 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 advantages of small size and large bandwidth. In recent years, many all-optical ultrasonic endoscope schemes have been reported, which mainly use two or more optical fibers to realize the emission and detection of ultrasonic waves respectively, so that the diameter of the endoscope is maintained at the millimeter level, which is difficult to achieve further miniaturization; some researchers have also proposed the use of a single double-clad optical fiber to achieve integrated transceiver lateral excitation, but the excitation energy is low and a bulky acoustic reflector is required to achieve lateral detection. Therefore, there is an urgent need for a fiber-optic ultrasonic endoscope that has 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 comprises a central core and a plurality of 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, 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 extension direction of the long side of the strip sensing layer, and the cross section of the hybrid excitation wedge tip covers at least one fiber core; the sensitivity enhancement column 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 endoscope 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, a part of the detection light is returned, and the other part of the detection light is transmitted through the first dielectric film, transmitted through the strip sensing layer to the second dielectric film, reflected and returned, and the first dielectric film, the second dielectric film and the strip sensing layer jointly 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 other cores of the multi-core optical fiber, transmitted through the first dielectric film and absorbed by the mixed excitation wedge tip, and a lateral pulse ultrasonic signal is excited, and the lateral pulse ultrasonic signal and the object to be measured act 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 to 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 two-photon polymerization 3D printing process, using PDMS photoresist to print the strip sensing layer;

[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, replace IPS photoresist, use two-photon polymerization 3D printing process to prepare IPS column as sensitization column;

[0023] S8. Fix the multi-core optical fiber with an optical fiber clamp, control the translation stage under a microscope to insert the end face of the multi-core optical fiber into a 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 um.

[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 acts on ultrasound, it generates violent vibrations and deformations near the resonant frequency. For the ultrasonic signal transmitted from the side, it mainly manifests as the lateral vibration and torsion of the column. The vibration 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 lower and narrower the frequency band will be. Therefore, a suitable sensing system can be selected according to different measurement targets.

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

[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 conceived 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 reflector, 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 realize double sensitivity enhancement, which greatly improves the sensitivity of lateral sensing, and realizes good directivity on the membrane plane through the strip structure of the sensing layer. 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 the traditional single-mode optical fiber in two intensity directions. The resolution ability of fiber optic endoscope imaging is greatly improved.

[0032] 2. The present invention realizes the integration of ultrasonic excitation and detection on a single optical fiber. The probe size is controlled to be the same size as that of a seven-core optical fiber, with a diameter of about 270um, which can penetrate into smaller blood vessels for detection, and there is no crosstalk between optical fibers in a single optical fiber. This solves the problem of large size and serious crosstalk between fibers in traditional multi-fiber ultrasonic detection.

[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 It is a structural diagram of the integrated fiber optic ultrasonic endoscope provided by the present invention;

[0036] Figure 2 It is a top view of the structure 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 solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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 used 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 sensing layer, a hybrid excitation wedge tip, a sensitivity enhancement column and an endoscope sheath.

[0040] The multi-core optical fiber comprises a central core and a plurality of 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 at the end face of the multi-core optical fiber, 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 core, the hybrid excitation wedge tip is located at the side of the strip sensing layer, the direction of the wedge tip slope is along the extension direction of the long side of the strip sensing layer, and the cross section of the hybrid excitation wedge tip covers at least one core; the sensitivity enhancement column is located above the corresponding strip sensing layer on the outside of the second dielectric film; the endoscope sheath is used to protect and isolate the dielectric film, the strip sensing layer, the hybrid excitation wedge tip, 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, a part of the detection light is returned, and the other part of the detection light is transmitted through the first dielectric film, transmitted through the strip sensing layer to the second dielectric film, reflected and returned, and the first dielectric film, the second dielectric film and the strip sensing layer jointly 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 other cores of the multi-core optical fiber, transmitted through the first dielectric film and absorbed by the mixed excitation wedge tip, and a lateral pulse ultrasonic signal is excited, and the lateral pulse ultrasonic signal and the object to be measured act 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 to 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 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.

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

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

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

[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 two-photon polymerization 3D printing process, using PDMS photoresist to print the strip sensing layer;

[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, replace IPS photoresist, use two-photon polymerization 3D printing process to prepare IPS column as sensitization column;

[0056] S8. Fix the multi-core optical fiber with an optical fiber clamp, control the translation stage under a microscope to insert the end face of the multi-core optical fiber into a 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 um.

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

[0059] Specifically, the sensitivity enhancement column is a cylinder with a length of 100um to 300um and a diameter of 10um to 20um. When the sensitivity enhancement column acts on ultrasound, it produces violent vibrations and deformations near the resonant frequency. For the ultrasonic signal transmitted from the side, it mainly manifests as the lateral vibration and torsion of the column. The vibration 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 sensitivity enhancement effect. The height, diameter, and Young's modulus of the sensitivity enhancement 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 lower and narrower the frequency band will be, so the appropriate sensing system can be selected according to different measurement targets.

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

[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 is a structural diagram of the integrated fiber optic ultrasonic endoscope provided in this embodiment, such as 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 structure 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 FIG. 1 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 rather than to limit it. 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 used 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 protection scope 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 provided with a plurality of cores uniformly surrounding the central core. The geometric 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 direction of the wedge tip slope is along the extension direction of the long side 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 endoscope 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 is returned, and the other part of the detection light is transmitted through the first dielectric film, transmitted through the strip sensing layer (103) to the second dielectric film, reflected and returned, and 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), transmitted through the first dielectric film and absorbed by the mixed excitation wedge tip (104), and a lateral pulse ultrasonic signal is excited, and the lateral pulse ultrasonic signal and the object to be measured act 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 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) comprises 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 in opposite directions.

4. The integrated fiber optic ultrasonic endoscope according to claim 1, characterized in that: The detection light signal is C-band continuous laser; the excitation light signal is 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 1000-1100nm 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 arm 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, flattening the end face of the multi-core optical fiber (101) 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 the IPS photoresist, and using a two-photon polymerization 3D printing process to prepare an IPS column as a 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) upside down into a protective cover filled with ultrasonic coupling liquid, apply ultraviolet glue at the contact position between the protective cover and the edge of the optical fiber, and cure 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 um.

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 sensitivity enhancement column (105) is a cylinder with a length of 100um to 300um and a diameter of 10um to 20um.

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