All-optical ultrasonic imaging device

Abstract

The invention discloses an all-optical ultrasonic imaging device which comprises a probe, an ultrasonic excitation device, an ultrasonic demodulation device and an imaging device. The probe comprises a photoacoustic conversion composite film, an excitation optical fiber probe and a demodulation optical fiber probe, and a pi-FBG sensor is arranged on the demodulation optical fiber; the excitation ultrasonic device sends short pulse laser to the excitation optical fiber probe and is used for exciting the opto-acoustic composite film to enable the opto-acoustic composite film to generate ultrasonic waves, and the pi-FBG sensor is used for receiving ultrasonic echoes obtained after the to-be-detected object reflects the ultrasonic waves; the ultrasonic demodulation device sends demodulation laser to the pi-FBG sensor, and the ultrasonic demodulation device is also used for receiving the detection laser; and the imaging device is connected with the ultrasonic demodulation device and is used for processing and imaging the detection laser. The all-optical technology has high electromagnetic interference tolerance, is very suitable for sensing in medical equipment, and is particularly suitable for imaging application in cardiovascular medicine.

Description

Technical Field

[0001] The present invention relates to the technical field of medical ultrasonic imaging, and in particular to an all-optical ultrasonic imaging device. Background Art

[0002] Ultrasound, defined as sound with frequencies ranging from 20 kHz to several GHz, has shown a wide range of applications in medical imaging, materials science, physics, chemistry, and nanotechnology. In ultrasonography, ultrasound pulses are transmitted into the body and the pulses are reflected as image contrast due to interfaces between tissues with different acoustic impedances. The echoing pulses carry physiological and pathological information within the tissue. In particular, high-frequency ultrasound with frequencies >20 MHz is very useful for high-resolution (<100 μm) biomedical applications such as endoscopic imaging, ophthalmology, intravascular imaging, and dermatology.

[0003] Imaging technology that uses ultrasound signals as information carriers has a wide range of applications in observing the internal structure of the human body, finding the source of disease, and examining pregnant women. Although magnetic resonance imaging (MRI) systems continue to improve the resolution to about 500μm. However, the initial investment and maintenance costs of MRI are high, and conventional interventional procedures are limited. In addition, the temporal resolution of MRI is limited, which limits its application in rapid imaging and rapid diagnosis. X-ray computed tomography is a relatively affordable method with a resolution of about 400μm, but it relies on ionizing radiation and is therefore unsafe for medical monitoring. Optical methods are a promising method for biomedical imaging. Optical coherence tomography (OCT) is an optical technology that can support real-time imaging with high resolution (5-10μm); however, OCT has a limited penetration depth (3-6 mm).

[0004] Compared to other medical imaging techniques, medical ultrasound imaging is safer and more portable, and can provide high frame rates of more than 25 frames per second. Currently, piezoelectric transducers are the main means of generating biomedical ultrasound for imaging and therapeutic applications. However, high-resolution ultrasound imaging (<100μm) is limited due to the limited bandwidth of the ultrasound signal generated by the piezoelectric effect. High-intensity focused ultrasound is valuable for therapeutic applications. Due to the fragility of piezoelectric materials and the impedance mismatch of large apertures, its application in precision treatment with high-frequency ultrasound is also challenging. Capacitive micromachined ultrasonic transducers (CMUTs) are an alternative technology that is expected to generate broadband ultrasound pulses, but there are technical challenges in realizing two-dimensional high-frequency CMUT arrays. However, piezoelectric transducers may have limited bandwidth and insufficient sensitivity for reduced element size.

[0005] Laser generated ultrasound (LGUS) technology generates high-intensity ultrasound waves based on the photoacoustic effect together with the surrounding medium with a high thermal expansion coefficient. Based on the photoacoustic effect, laser ultrasound technology generates ultrasonic pulses according to the laser profile. If a short laser is used, short ultrasonic pulses of the order of nanoseconds can be generated. Therefore, this is a relatively simple method to create broadband high-frequency ultrasonic signals. The laser-generated ultrasound method of the photoacoustic effect can greatly enhance the bandwidth of the ultrasonic signal and has the potential for high-resolution imaging. Compared with traditional piezoelectric ultrasonic transducers, laser-generated ultrasound technology is conducive to high-frequency arrays for high-resolution ultrasonic imaging. In addition, efficient, broadband laser-generated focused ultrasound can realize a wide range of high-intensity focused ultrasound applications, such as high-precision treatment and droplet injection. In addition, the non-contact excitation advantages provided by laser-generated ultrasound technology and the characteristics of generating broadband high-frequency ultrasonic signals allow the realization of unique applications that cannot be achieved with traditional ultrasonic transmitters.

[0006] Optical ultrasound imaging probes, which transmit and receive via light, are emerging as an alternative to electronic probes. They offer several key advantages, including the potential to generate and detect broadband ultrasound fields (tens of MHz) required for high-resolution intravascular imaging and immunity to electromagnetic interference. In addition, optical fibers for ultrasound transmission and reception can provide the level of miniaturization required for minimally invasive use, and their cost is suitable for disposable devices. Furthermore, the use of optical fibers allows the integration of complementary imaging and therapeutic modalities without compromising device size or performance. All-optical ultrasound imaging has unique advantages in providing high-resolution information and facilitating the construction of endoscopic ultrasound miniature probes. Therefore, all-optical ultrasound imaging technology can have the penetration depth of ultrasound while having high imaging resolution of biological tissues.

[0007] Since the discovery of lasers in the 1960s, optical generation and detection of ultrasound waves has been considered as a potential way to overcome some of the limitations of conventional piezoelectric ultrasonic transducers. Compared with piezoelectric transducers, optical-based technologies are more complex and expensive, and there are key issues such as relatively low transmission efficiency of laser-generated ultrasound technology and poor sensing sensitivity compared to optical detection of ultrasound waves. As a result, these issues have limited its widespread application in commercial industries, which is why piezoelectric transducers still dominate most ultrasound-related applications.

[0008] Therefore, there is an urgent need for an all-optical ultrasonic imaging device that can achieve continuous real-time imaging. Summary of the invention

[0009] In order to solve the problem of the all-optical ultrasonic imaging device that cannot realize continuous real-time imaging proposed in the above background technology, the present invention provides the following technical solutions:

[0010] An all-optical ultrasonic imaging device, comprising: a probe, an optical fiber catheter control component, an excitation ultrasonic device, an ultrasonic demodulation device and an imaging device; the probe comprises a photoacoustic conversion composite film, an excitation optical fiber and a demodulation optical fiber probe, and the demodulation optical fiber probe is provided with a π-FBG sensor;

[0011] The excitation ultrasound device and the ultrasound demodulation device are both connected to the probe via the optical fiber catheter control component, and the optical fiber catheter control component is used to control the rotation of the probe and the reciprocating movement along the vertical rotation direction;

[0012] The excitation ultrasound device is used to send a short pulse laser to the excitation optical fiber probe, the short pulse laser is used to excite the photoacoustic composite membrane to generate ultrasound, and the π-FBG sensor is used to receive the ultrasound echo obtained after the object to be detected reflects the ultrasound;

[0013] The ultrasonic demodulation device is used to send a demodulation laser to the π-FBG sensor, so that the demodulation laser is reflected as a detection laser under the action of the ultrasonic echo, and the ultrasonic demodulation device is also used to receive the detection laser;

[0014] The imaging device is connected to the ultrasonic demodulation device and is used to process and image the detection laser.

[0015] Preferably, the demodulated laser is tuned within a certain wavelength range according to a certain timing, so that the wavelength range of the laser emitted at each moment is different;

[0016] The wavelength of the short pulse laser does not fall within the wavelength range of the demodulation laser.

[0017] Preferably, the short pulse laser is a single-wavelength pulse laser.

[0018] Preferably, the optical fiber catheter control assembly comprises a rotor, a stator, a gear system and a prism component, the rotor rotates relative to the stator, the rotor drives the prism component to rotate through the gear system, the gear system enables the rotation speed of the prism component and the rotor relative to the stator to maintain a certain ratio value, and the prism component is a prism combination that can achieve an object-image rotation ratio of a predetermined ratio;

[0019] The rotor and the stator are both provided with two optical fiber collimators, and the optical axes of the two optical fiber collimators of the rotor and the two optical fiber collimators of the stator are parallel to the rotating axis of the rotor and are equidistant from the rotating axis. When the rotor rotates to a specific angle, the two optical fiber collimators of the rotor and the two optical fiber collimators of the stator are coaxial. Along the rotating axis direction of the rotor, the prism component is arranged between the rotor and the stator, and the light beams incident on the two optical fiber collimators of the stator are transmitted to the two optical fiber collimators of the rotor after passing through the prism component, and finally reach the probe.

[0020] Preferably, the photoacoustic conversion composite film is provided with a concave curved surface for generating focused ultrasound when laser is incident on the photoacoustic transducer device.

[0021] Preferably, the photoacoustic conversion composite film is arranged at the end of the excitation optical fiber, and is composed of a PDMS polymer film and a multi-walled carbon nanotube layer from the surface to the inside;

[0022] A gold-plated layer is provided on the back side of the optical fiber opposite to the concave curved surface, which is used to reflect the light beam to the concave curved surface.

[0023] Preferably, the method of disposing the photoacoustic conversion composite film at the end of the excitation optical fiber comprises:

[0024] S1, grinding the end and etching a concave surface;

[0025] S2, the optical fiber end obtained in step S1 is immersed in a multi-walled carbon nanotube gel to obtain a multi-walled carbon nanotube layer by a immersion and pulling method;

[0026] S3, the optical fiber end obtained in step S2 is immersed in the PDMS solution to obtain a PDMS polymer film by a PDMS pulling method.

[0027] Preferably, along the radial direction of the probe, the photoacoustic conversion composite film, the demodulation optical fiber probe and the excitation optical fiber probe are arranged in sequence, and the photoacoustic conversion composite film is arranged on the periphery of the excitation optical fiber and the demodulation optical fiber;

[0028] The probe further includes an ultrasonic shielding plate, the length of the excitation optical fiber probe extending from the optical fiber entrance into the probe is greater than the length of the demodulation optical fiber probe extending from the optical fiber entrance into the probe, and along the length direction of the probe, the ultrasonic shielding plate separates the π-FBG sensor and the end of the excitation optical fiber probe;

[0029] The end of the excitation optical fiber probe is provided with a polished bevel, and the polished bevel is coated with a metal reflective film, so that the laser transmitted to the end is reflected by the polished bevel and then incident on the photoacoustic conversion composite film;

[0030] The axis of the ultrasonic wave emission direction of the photoacoustic conversion composite membrane and the axis of the ultrasonic echo receiving direction of the π-FBG sensor form a preset angle.

[0031] Preferably, along the radial direction of the probe, the photoacoustic conversion composite film, the excitation optical fiber probe and the demodulation optical fiber probe are arranged in sequence, and the photoacoustic conversion composite film is arranged on the periphery of the excitation optical fiber and the demodulation optical fiber;

[0032] The probe further includes an ultrasonic shielding plate, the length of the excitation optical fiber probe extending from the optical fiber entrance into the probe is shorter than the length of the demodulation optical fiber probe extending from the optical fiber entrance into the probe, and along the length direction of the probe, the ultrasonic shielding plate separates the π-FBG sensor and the end of the excitation optical fiber probe;

[0033] The end of the excitation optical fiber probe is provided with a polished bevel, and the polished bevel is coated with a metal reflective film, so that the laser transmitted to the end is reflected by the polished bevel and then incident on the photoacoustic conversion composite film;

[0034] The axis of the ultrasonic wave emission direction of the photoacoustic conversion composite membrane and the axis of the ultrasonic echo receiving direction of the π-FBG sensor form a preset angle.

[0035] Preferably, the probe further comprises a circular tip housing, a retainer, and a twisted spring;

[0036] The retainer is fixedly connected to the circular tip housing and the demodulation optical fiber at two radially opposite surfaces respectively;

[0037] The twisted spring is arranged at the entrance end of the probe connected to the optical fiber, and the inner side of the twisted spring wraps the excitation optical fiber and the demodulation optical fiber.

[0038] Preferably, the all-optical ultrasound imaging device also includes a catheter transmission part and a catheter connector; the connecting end of the optical fiber catheter control component and the probe is provided with an optical fiber connector; the probe is connected to the catheter transmission part, the catheter connector and the optical fiber connector in sequence.

[0039] Preferably, the optical fiber catheter control assembly comprises an optical fiber slip ring with an optical filter assembly, so that the optical path where the ultrasonic demodulation light is located allows the ultrasonic demodulation light to pass through and cuts off the ultrasonic excitation light.

[0040] Preferably, the ultrasonic demodulation device comprises: a demodulation laser component, a fiber coupler and a fiber circulator, wherein:

[0041] The demodulation laser component is used to emit the demodulation laser;

[0042] The optical fiber coupler is used to couple the light beam transmitted through air into the optical multimode optical fiber for transmission;

[0043] The optical fiber circulator is used to output the demodulated laser to the π-FBG sensor, and is used to output the detection laser to the imaging device.

[0044] Preferably, the imaging device comprises: a photoelectric detector, a data acquisition card and a computer, wherein:

[0045] The photodetector is used to receive the detection laser and convert the optical signal of the detection laser into an electrical signal;

[0046] The data acquisition card is used to collect the electrical signal and quantize the electrical signal into a digital signal;

[0047] The computer is used to receive the digital signal, and perform data processing and ultrasonic imaging on the digital signal;

[0048] The optical fiber catheter control component includes a high-speed optical fiber slip ring, which cooperates with the data acquisition card and the photoelectric detector to achieve high-speed image acquisition.

[0049] Compared with the prior art, the beneficial effects of the present invention are: (i) All-optical technology with high electromagnetic interference tolerance; this is because the optical fiber has a small lateral size, flexibility and anti-electromagnetic interference ability, so it is very suitable for sensing in medical equipment, especially for imaging applications in cardiovascular medicine. (ii) The use of π-FBG sensors is suitable for detecting transversely incident ultrasound, and is fully compatible with the optical fiber transceiver configuration of intravascular imaging, so it is very suitable for the implementation of endoscopic catheter applications that require high-speed rotation; the omnidirectionality of the imaging probe is very suitable for receiving pulses from a distant ultrasonic imaging probe to track the position of the ultrasound positioning to the sample; using πFBG for ultrasonic detection and demodulation and realizing backward mode photoacoustic imaging can achieve high sensitivity to low-amplitude photoacoustic signals. (iii) Through the thermoelastic method, the use of short laser pulses to irradiate the photoacoustic composite film can generate broadband ultrasound from tens of MHz to hundreds of GHz, thereby achieving high spatial resolution imaging. (iv) The axial resolution can be enhanced by using modulated excitation light with a higher ultrasonic frequency. (V) By increasing the curvature of the composite film substrate to achieve focused beams and using shorter excitation light pulses to increase the center frequency, the lateral resolution is improved; (VI) By using a high-speed fiber slip ring type catheter controller, the imaging probe can rotate and move back and forth at high speed, achieving rapid clinical transformation and real-time circumferential imaging. (VII) The relative positions of the composite film, excitation fiber and demodulation fiber ensure that the demodulation accuracy and sensitivity of the ultrasound can be achieved during the rotational scanning process of the ultrasound. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0051] Figure 1 FIG. 4 is a functional schematic diagram of an all-optical ultrasonic imaging device according to an embodiment of the present invention.

[0052] Figure 2 Schematic diagram of the structure of an ultrasonic excitation device in one embodiment of the present invention.

[0053] Figure 3 FIG. 4 is a schematic diagram of the structure of an ultrasonic demodulation device in one embodiment of the present invention.

[0054] Figure 4a FIG. 4 is a schematic diagram of the structure of a probe in one embodiment of the present invention.

[0055] Figure 4b FIG. 4 is a schematic diagram of the structure of a probe in another embodiment of the present invention.

[0056] Figure 4c FIG. 4 is a schematic diagram of the structure of a probe in another embodiment of the present invention.

[0057] Figure 4d for Figure 4c Schematic diagram of the structure of the optical fiber end.

[0058] Figure 5 FIG. 4 is a schematic diagram of the structure of an optical fiber catheter in an embodiment of the present invention.

[0059] Figure 5a FIG. 4 is a schematic diagram of the structure of an optical fiber catheter control assembly in one embodiment of the present invention.

[0060] Figure 5b FIG. 4 is a schematic cross-sectional view parallel to the rotation axis of an optical fiber catheter control device in one embodiment of the present invention.

[0061] Figure 5c for Figure 5b A partial enlarged schematic diagram of area A in the middle.

[0062] Figure 6 FIG. 4 is a schematic diagram of the structure of an optical fiber slip ring in one embodiment of the present invention.

[0063] Figure 7 FIG. 1 is a functional structure diagram of a demodulation part in an embodiment of the present invention. DETAILED DESCRIPTION

[0064] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0065] like Figure 1 As shown, an all-optical ultrasonic imaging device 30 includes: a probe 50, an optical fiber catheter control component 40, an excitation ultrasonic device 10, an ultrasonic demodulation device 20 and an imaging device 30; the probe 50 includes a photoacoustic conversion composite film 52, an excitation optical fiber probe 51 and a demodulation optical fiber probe 55, and the demodulation optical fiber probe 55 is provided with a π-FBG sensor 54;

[0066] The excitation ultrasound device 10 and the ultrasound demodulation device 20 are both connected to the probe 50 via an optical fiber catheter control component 40, and the optical fiber catheter control component 40 is used to control the rotation of the probe 50 and the reciprocating movement along the vertical rotation direction;

[0067] The excitation ultrasound device 10 is used to send a short pulse laser to the excitation optical fiber probe 51, and the short pulse laser is used to excite the photoacoustic conversion composite film 52 to generate ultrasound. The π-FBG sensor 54 is used to receive the ultrasound echo obtained after the object to be detected reflects the ultrasound.

[0068] The ultrasonic demodulation device 20 is used to send demodulation laser to the π-FBG sensor 54.

[0069] So that the demodulation laser is reflected as the detection laser under the action of the ultrasonic echo, and the ultrasonic demodulation device 20 is also used to receive the detection laser;

[0070] The imaging device 30 is connected to the ultrasonic demodulation device 20 and is used to process and image the detection laser.

[0071] Specifically, the excitation ultrasound device 10 uses a pulsed laser to act on the photoacoustic conversion composite film 52 to generate ultrasound, and the ultrasound propagates in the biological tissue 53. When the ultrasound propagates in the biological tissue 53, a portion of the energy is reflected back by the biological tissue 53 to the position of the π-FBG sensor 54 connected to the ultrasonic demodulation device 20, and is sensed by it; the ultrasonic demodulation device 20 is connected to the probe 50, and sends a demodulation laser to the π-FBG sensor 54. Under the action of ultrasound, the reflection spectrum generated after the ultrasonic demodulation light source module is transmitted to the π-FBG sensor 54 drifts, which is the detection signal. By sampling and algorithmically demodulating the spectral drift information of the π-FBG sensor 54, the tomographic imaging of the biological tissue 53 can be reconstructed.

[0072] like Figure 1 As shown, the laser emitted by the excitation ultrasound device 10 is transmitted to the excitation fiber probe 51 through the fiber optic catheter control component 40, so that the excitation light is irradiated onto the photoacoustic conversion composite film 52, thereby generating ultrasound. The ultrasound propagates in the biological tissue and is back-reflected by the biological tissue. The reflected ultrasound is received by the π-FBG sensor 54, thereby reconstructing the tomographic image of the biological tissue structure.

[0073] like Figure 2 As shown, the excitation ultrasound device 10 is a laser light source that couples a multimode fiber to output laser light. The excitation ultrasound device 10 includes a light source assembly 103 and a first multimode optical fiber 105, wherein the light source assembly 103 includes a picosecond or nano-picosecond pulse laser 101 and a first optical fiber coupler 117 104. In some embodiments, it also includes a first lens group 102. The pulse laser 101 outputs a laser spot for spatial transmission. After being bundled by the first lens group 102, the light beam transmitted through the air is coupled into the first multimode optical fiber 105 for transmission through the first optical fiber coupling device 104. The first optical fiber coupling device 104 is composed of an optical fiber coupling lens and an optical fiber core with end face processing. The function of the optical fiber coupling lens is to focus the light spot transmitted through the air to a NA numerical aperture value and a light spot diameter OD value that matches the NA and OD of the optical fiber, so that it can enter the optical fiber with maximum coupling efficiency.

[0074] In a specific embodiment, the parameters of the pulse laser 101 are set to 50ps pulse width, 5kHz repetition rate, and 5uJ-20uJ fiber-coupled output end energy, which is used to excite the photoacoustic composite film to generate ultrasound.

[0075] like Figure 3 As shown, the light source part in the ultrasonic demodulation device 20 includes a demodulation laser component 113 and a second multimode optical fiber 115, wherein the demodulation laser component 113 includes a light source tunable laser 111 and a second optical fiber coupling device 114. In some embodiments, it also includes a second lens group 112. In actual use, the tunable laser 111 outputs a laser spot for spatial transmission, which is focused by the second lens group, and then the air-transmitted light beam is coupled into the second multimode optical fiber 115 for transmission through the second optical fiber coupling device 114.

[0076] In some embodiments, the demodulation laser is tuned within a certain wavelength range according to a certain timing, so that the wavelength range of the laser emitted at each moment is different;

[0077] The wavelength of the short pulse laser does not fall within the wavelength range of the demodulation laser. This facilitates the isolation of the demodulation laser optical path and the demodulation laser optical path in the optical fiber slip ring through a filter when the subsequent imaging probe rotates at high speed.

[0078] In some embodiments, the wavelength range is 1520 nm to 1570 nm.

[0079] In a specific embodiment, the parameters of the ultrasonic demodulation device 20 are set as follows: wavelength tuning range of 1520 to 1570 nm, line width of 200 kHz, 10-100 mW, narrow line width tunable laser, for interrogating the π-FBG sensor by edge detection method.

[0080] In some embodiments, the short pulse laser is a pulse laser of a single wavelength or includes pulse lasers of multiple different wavelengths.

[0081] In some embodiments, Figure 5b and Figure 5c As shown, the optical fiber catheter control assembly 40 includes a rotor 207, a stator 209, a gear system and a prism component 116. The rotor 207 rotates relative to the stator 209. The rotor 209 drives the prism component 116 to rotate through the gear system. The gear system allows the rotation speeds of the prism component 116 and the rotor 207 relative to the stator 209 to maintain a certain ratio value; the prism component 116 is a prism combination that can achieve an object-image rotation ratio of a predetermined ratio. The rotor 207 and the stator 209 are both provided with two optical fiber collimators 119, and the optical axes of the two optical fiber collimators 119 of the rotor 207 and the two optical fiber collimators 119 of the stator 209 are parallel to the rotation axis of the rotor 207 and are equidistant from the rotation axis. When the rotor 207 rotates to a specific angle, the two optical fiber collimators 119 of the rotor 207 and the two optical fiber collimators 119 of the stator 209 are coaxial. Along the rotation axis direction of the rotor 207, the prism component 116 is provided between the rotor 207 and the stator 209, and the light beams incident on the two optical fiber collimators 119 of the stator 209 reach the two optical fiber collimators 119 of the rotor 207 after passing through the prism component 116, and finally reach the probe.

[0082] In some embodiments, the photoacoustic conversion composite film 52 is provided with a concave curved surface for generating focused ultrasound when laser is incident on the photoacoustic transducer device.

[0083] In some embodiments, Figure 4c and Figure 4dAs shown, the photoacoustic conversion composite film 52 is arranged at the end of the excitation optical fiber probe 51, and the PDMS polymer film and the multi-walled carbon nanotube layer are arranged from the surface to the inside; the back of the optical fiber opposite to the concave curved surface is provided with a gold-plated layer 5, which is used to reflect the light beam to the concave curved surface 4, and the curvature radius of the concave curved surface 4 is 1 to 2 times the diameter of the optical fiber. The outer diameter OD of the circular tip shell 240 is between 0.9 and 1.5 mm, and the glue filling in the fixed area of ​​the probe 50 is limited to a refractive index within the range of 1.46 to 1.57. The invalid area at the top of the Π-FBG optical fiber grating 54 penetrates into the glue 241 and is solidified by the glue. The ultrasonic shielding plate 243 is placed between the Π-FBG optical fiber grating 54 and the photoacoustic conversion composite film 5252. The head of the excitation optical fiber probe 51 needs to be processed at a fixed angle to form a polished bevel 242, and the fixed angle is not limited to between 20° and 70°. The polished bevel needs to be plated with a metal reflective film, and the thickness of the reflective film is not limited to 50 to 200 μm. To prevent the Π-FBG fiber grating 54 from resonating with the ultrasonic echo and causing bit errors, the two sides of the retainer 247 are respectively attached to the Π-FBG fiber grating 54 and the outer wall of the catheter. The inner layer of the twisted spring 248 wraps the excitation fiber probe 51 and the sensing fiber, and the outer diameter is not limited to 0.9-1.5 mm.

[0084] like Figure 4d As shown, the end of the optical fiber is coated with a light absorbing material layer 3 and a high molecular polymer layer 4, and a gold-plated layer 5 is on the back side opposite to the curved surface.

[0085] In some embodiments, the method of disposing the photoacoustic conversion composite film at the end of the excitation optical fiber includes:

[0086] S1, grinding the end and etching a concave surface;

[0087] S2, the optical fiber end obtained in step S1 is immersed in a multi-walled carbon nanotube gel to obtain a multi-walled carbon nanotube layer by a immersion and pulling method;

[0088] S3, the optical fiber end obtained in step S2 is immersed in the PDMS solution to obtain a PDMS polymer film by a PDMS pulling method.

[0089] Specifically, the optical fiber used is a multimode optical fiber with a core diameter of 50-600 microns and a quartz or polymer cladding. After the coating layer is stripped off the end of the optical fiber with a wire stripper, the exposed end face is polished, and after being polished flat, it is etched with a laser to carve out a curved surface with a curvature radius r of 1 to 2 times the diameter of the optical fiber; the distal end of the above-carved optical fiber is soaked in concentrated nitric acid for 3-5 hours, and then ultrasonically cleaned with ultrapure water and ethanol, and then dried in an oven at 80-100°C for 1-2 hours for use;

[0090] The next step is Figure 4dAs shown, the gold-plated layer 5 is protected by the curved surface, and then sputtered by a magnetron sputtering device to obtain a gold film with a film thickness of 20-100nm, and the coating length e> the length of the curved surface;

[0091] The light-absorbing material layer is a multi-walled carbon nanotube layer (MWCNT), wherein the multi-walled carbon nanotubes are surface-modified to prepare MWCNT-gel, the engraved optical fiber distal end is immersed in the MWCNT-gel for 20 seconds by the immersion pulling method, then pulled at a speed of 6 cm / s, and dried at 50-80°C for 1 hour to obtain a multi-walled carbon nanotube layer.

[0092] The surface modification specifically includes the following steps: ① 1-pyrenebutyric acid and excess thionyl chloride (SOCl2) are transferred to a round-bottom flask and refluxed at 100°C for 30 minutes. Unreacted SOCl2 is removed by distillation until dry pyrenebutyric chloride remains; ② Solid pyrenebutyric chloride is dissolved in dry THF, oleylamine and triethylamine are dissolved in another anhydrous THF, and the pyrenebutyric chloride solution is added at 0°C; ③ Stir overnight at room temperature, dissolve the product in ether and wash with a large amount of water, extract the organic layer after washing and dry it with sodium sulfate, evaporate the ether and dry the product in vacuum at room temperature to obtain oleylamine functionalized pyrene; ④ MWCNT and oleylamine functionalized pyrene are dissolved in xylene (or ethyl acetate) in a mass ratio of 1:1 and ultrasonically treated for 5 hours, and all reactions are carried out under Schlenk conditions; ⑤ After ultrasonication, the treated MWCNT is washed with THF at least 5 times to remove the unadsorbed dispersant, and the surface-treated MWCNT is obtained after vacuum drying at room temperature for 24 hours;

[0093] Among them, MWCNT-gel is prepared by uniformly dispersing the surface-treated MWCNT in xylene by ultrasonic method to obtain a xylene solution of MWCNT, wherein the ratio of MWCNT to xylene is 5-15 mg / ml, wherein the ultrasonic time is 10-20 s, and the ultrasonic energy is 72 w; the obtained xylene solution is ultrasonically mixed with acetone at a volume ratio of 1:2 overnight to obtain the product.

[0094] The polymer film is polydimethylsilane (PDMS), which is prepared by the optical fiber with multi-walled carbon nanotube layer dipping and pulling method. Among them, PDMS and 10wt% curing agent are mixed with acetone, anisole, ethyl acetate, toluene, xylene and one or more mixtures thereof at 35-50wt%, and heated and dissolved under appropriate conditions to obtain PDMS solution, and the far end of the optical fiber with multi-walled carbon nanotube layer is dipped for 20s and then pulled at a speed of 6cm / s, and dried at 80-100℃ for 30min to obtain the optical fiber transducer device.

[0095] In some embodiments, the photoacoustic conversion composite film is a PDMS composite film or a PMMA composite film.

[0096] In some embodiments, Figure 4a As shown, along the radial direction of the probe, the photoacoustic conversion composite film 52 is arranged on the periphery of the excitation optical fiber and the demodulation optical fiber; the photoacoustic conversion composite film 52, the demodulation optical fiber and the excitation optical fiber are arranged in sequence; the probe also includes an ultrasonic shielding plate 243, and the length of the excitation optical fiber from the optical fiber entrance into the probe is greater than the length of the demodulation optical fiber from the optical fiber entrance into the probe, and along the length direction of the probe, the ultrasonic shielding plate separates the π-FBG sensor 54 and the end of the excitation optical fiber; the end of the excitation optical fiber is provided with a polished bevel 242, and the polished bevel 242 is coated with a metal reflective film, so that the laser transmitted to the end is reflected by the polished bevel 242 and then incident on the photoacoustic conversion composite film 52; the axis of the ultrasonic emission direction of the photoacoustic conversion composite film 52 and the axis of the ultrasonic echo receiving direction of the π-FBG sensor 54 form a preset angle.

[0097] In some embodiments, Figure 4b As shown, along the radial direction of the probe, the photoacoustic conversion composite film 52 is arranged on the periphery of the excitation optical fiber and the demodulation optical fiber; the photoacoustic conversion composite film 52, the excitation optical fiber and the demodulation optical fiber are arranged in sequence; the probe also includes an ultrasonic shielding plate 243, and the length of the excitation optical fiber from the optical fiber entrance into the probe is less than the length of the demodulation optical fiber from the optical fiber entrance into the probe, and along the length direction of the probe, the ultrasonic shielding plate separates the π-FBG sensor 54 and the end of the excitation optical fiber; the end of the excitation optical fiber is provided with a polished bevel 242, and the polished bevel 242 is coated with a metal reflective film, so that the laser transmitted to the end is reflected by the polished bevel 242 and then incident on the photoacoustic conversion composite film 52; the axis of the ultrasonic emission direction of the photoacoustic conversion composite film 52 and the axis of the ultrasonic echo receiving direction of the π-FBG sensor 54 form a preset angle.

[0098] In some embodiments, Figure 4a and 4b As shown, the probe also includes a circular tip shell 240, a retainer 247, and a twisted spring 248; the retainer 247 is fixedly connected to the circular tip shell 240 and the demodulation optical fiber at two radially opposite sides; the twisted spring 248 is arranged at the entrance end of the probe accessing the optical fiber, and the inner side of the twisted spring 248 wraps the excitation optical fiber and the demodulation optical fiber.

[0099] Specifically, if Figure 4a , Figure 4bAs shown, the outer diameter of the circular tip shell 240 is between 0.9 and 1.5 mm, the glue filling in the fixed area of ​​the probe 50 is limited to a refractive index within the range of 1.46 to 1.57, the invalid area at the top of the Π-FBG sensor 54 penetrates into the glue 241 and is solidified by the glue 241, wherein the ultrasonic shielding plate 243 is placed between the Π-FBG sensor 54 and the photoacoustic conversion composite film 52246, and the head of the excitation optical fiber probe 51 is polished at a fixed angle to form a polished bevel 242, and the fixed angle is not limited to between 20° and 70°. The polished bevel 242 needs to be plated with a metal reflective film, and the thickness of the reflective film is not limited to 50 to 200 μm. In order to prevent the Π-FBG optical fiber grating 54 from resonating with the ultrasonic echo at a fixed frequency and causing bit errors, the two sides of the retainer 247 are respectively attached to the Π-FBG optical fiber grating 54 and the outer wall of the catheter. The inner layer of the twisted spring 248 wraps the excitation optical fiber probe 51 and the sensing optical fiber, and the outer diameter is not limited to between 0.9 and 1.5 mm.

[0100] In some embodiments, Figure 1 As shown, the all-optical ultrasound imaging device 30 also includes an optical fiber catheter control component 40. The excitation ultrasound device 10 and the ultrasound demodulation device 20 are both connected to the probe 50 through the optical fiber catheter control component 40. The optical fiber catheter control component 40 is used to control the rotation of the probe 50 and the reciprocating movement along the vertical rotation direction. Figure 5a As shown, in some embodiments, a motor and a transmission mechanism are disposed on the base 205 of the optical fiber catheter control assembly 40, and the motor drives the rotor to rotate through the transmission mechanism.

[0101] Specifically, the small pulley 212 is sleeved on the rotating shaft of the motor and fixed by glue or interference fit. The tensioning wheel seat 213 is installed on the base 205 by screws passing through its waist hole, and can be adjusted by sliding back and forth along the direction of the line connecting the two centers of the waist hole. The inner ring of the tensioning wheel bearing 214 is fixed on the shaft of the tensioning wheel seat 213 by glue or interference fit. The synchronous belt 215 is wound around the tooth surfaces of the small pulley 212 and the large pulley, and by adjusting the position of the tensioning wheel seat 213, the synchronous belt 215 is tightened with the outer ring of the tensioning wheel bearing 214 to achieve smooth transmission from the motor to the rotor and high-speed rotation of the rotor. The guide rail module includes a guide rail seat 201, and a driving mechanism is arranged on the guide rail seat 201. The driving mechanism includes a rotating screw. The base 205 is provided with a threaded hole. The rotating screw and the threaded hole cooperate to drive the base 205 to move back and forth along the linear guide rail; the guide rod 202 is positioned through the mounting hole of the guide rail seat 201 and fixed with glue. The two guide rods 202 pass through the two through holes of the base 205 respectively, so that the base 205 can slide along the guide rod 202. The driving mechanism 204 is a linear motor, which is installed on the linear motor support 203 by screws, and the linear motor support 203 is also installed on the guide rail seat 201 by screws. The rotating screw 2041 of the linear motor 204 passes through the threaded through hole of the base 205, and drives the slider base 205 to slide smoothly along the guide rod 202 by rotating the screw 2041.

[0102] Among them, in some specific embodiments, such as Figure 5 As shown, the optical fiber catheter includes a probe 50, a catheter transmission part 501 and a catheter connector 502; the optical fiber catheter control component 40 is connected to the catheter connector 502, and the probe 50 performs retraction and rotation scanning operations driven by the optical fiber catheter control component 40, which is used to transmit the ultrasonic demodulation light and the ultrasonic excitation light to the probe 50 and perform high-speed rotation scanning and retraction while maintaining a relatively static state.

[0103] In some embodiments, Figure 6 As shown, the fiber optic catheter control assembly includes a fiber optic slip ring with a filter assembly 71, so that the ultrasound demodulation light is allowed to pass through the optical path where the ultrasound demodulation light is located and the ultrasound excitation light is cut off.

[0104] Specifically, if Figure 6As shown, the base 205 of the optical fiber catheter control assembly includes an optical fiber slip ring 129, and the optical fiber slip ring 129 includes a rotor structure 124 and a stator structure 122; the optical path of the stator structure 122 does not rotate, and the rotor structure 124 is partially driven by the motor to spin. The stator structure 122 includes a stator optical fiber collimator 127; the rotor structure 124 includes a rotor optical fiber collimator and a Dove prism 123. The rotor optical fiber collimator includes an ultrasonic demodulation optical rotor optical fiber collimator and an ultrasonic excitation optical rotor optical fiber collimator, which are used to couple the light beam of spatial optical transmission into optical fiber transmission; the stator optical fiber collimator includes an ultrasonic demodulation optical stator optical fiber collimator and an ultrasonic excitation optical stator optical fiber collimator, which are used to convert the light beam transmitted in the optical fiber into spatial optical transmission. The ultrasonic excitation light rotor fiber collimator and the ultrasonic excitation light stator fiber collimator are both composed of a fiber optic interface, a coupling lens, and a fiber optic ferrule with end face processing. The ultrasonic demodulation light rotor fiber collimator and the ultrasonic demodulation light stator fiber collimator are both composed of a fiber optic interface, a coupling lens, a fiber optic ferrule with end face processing, and a filter 71. The function of the filter 71 is to only pass the ultrasonic demodulation light and cut off the ultrasonic excitation light. This is to prevent the ultrasonic excitation light from entering the optical path of the ultrasonic demodulation light transmission and affecting the demodulation accuracy of the demodulation light. The excitation light generated by the excitation ultrasound device and the demodulation light generated by the ultrasonic demodulation device 20 are respectively converted by the stator collimator to be transmitted in the optical fiber into spatial light transmission. The two light beams are respectively incident on the dove microprism 123 for transmission, and then received by the rotor collimator and coupled into the ultrasonic excitation light fiber probe and the ultrasonic demodulation fiber probe respectively. The dove prism 123 and the rotor collimator rotate at the same time, so that the optical fibers of the two rotor collimators can respectively receive the excitation light and the demodulation light during the rotation process, thereby realizing the simultaneous rotation scanning of the two light beams.

[0105] In some embodiments, Figure 7 As shown, the ultrasonic demodulation device 20 includes: a demodulation laser component 113, a fiber coupler 117 and a fiber circulator 118, wherein:

[0106] The demodulation laser assembly 113 is used to emit a demodulation laser;

[0107] The optical fiber coupler 117 is used to couple the light beam transmitted through the air into the optical multimode optical fiber for transmission;

[0108] The optical fiber circulator 118 is used to output the demodulated laser to the π-FBG sensor 54 , and to output the detection laser to the imaging device 30 .

[0109] In some embodiments, Figure 7 As shown, the imaging device 30 includes: a photodetector 119, a data acquisition card 120 and a computer 121, wherein:

[0110] The photodetector 119 is used to receive the detection laser and convert the optical signal of the detection laser into an electrical signal;

[0111] The data acquisition card 120 is used to collect electrical signals and quantize the electrical signals into digital signals;

[0112] The computer 121 is used to receive digital signals, and perform data processing and ultrasonic imaging on the digital signals;

[0113] The optical fiber catheter control assembly 40 includes a high-speed optical fiber slip ring, which cooperates with the data acquisition card 120 and the photoelectric detector 119 to achieve image acquisition at a line rate of more than 100k.

[0114] like Figure 7 As shown, the laser emitted by the demodulation laser component 113 in the ultrasonic demodulation device 20 is tuned according to a certain wavelength range and a certain timing; the laser emitted by it is transmitted to the optical fiber slip ring optical path in the catheter control component 40 through optical fiber coupling, and then transmitted to the π-FBG sensor; under the action of ultrasonic sound pressure, the reflection spectrum of the π-FBG sensor drifts, and after being reflected to the optical fiber slip ring optical path structure of the catheter control component, it is transmitted to the port connected to the optical fiber coupler 117 by the optical fiber circulator 118; the reflection spectrum is then split to the input end of the photodetector 119 through the optical fiber coupler 117, and is received by the photodetector 119 and converted into an electrical signal, which is then collected by the data acquisition card 120 at a certain sampling rate, and the signal is transmitted to the computer 121. After being processed by the algorithm of the computer 121, a three-dimensional structure imaging with biological tissue characteristics can be obtained. If a balanced detector is used to receive the optical signal, two identical optical signal inputs need to be differentiated. If a photodetector 119 is used, multiple photodetectors 119 need to collect simultaneously in order to obtain the DC low-frequency component and the high-frequency component at the same time.

[0115] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An all-optical ultrasonic imaging device, characterized in that: It includes: Probe , an optical fiber catheter control component, an excitation ultrasound device, an ultrasound demodulation device and an imaging device; the probe comprises a photoacoustic conversion composite film, an excitation optical fiber probe and a demodulation optical fiber probe, and the demodulation optical fiber probe is provided with a π-FBG sensor; The excitation ultrasound device and the ultrasound demodulation device are both connected to the probe via the optical fiber catheter control component, and the optical fiber catheter control component is used to control the rotation of the probe and the reciprocating movement along the vertical rotation direction; The excitation ultrasound device is used to send a short pulse laser to the excitation optical fiber probe, the short pulse laser is used to excite the photoacoustic composite membrane to generate ultrasound, and the π-FBG sensor is used to receive the ultrasound echo obtained after the object to be detected reflects the ultrasound; The ultrasonic demodulation device is used to send a demodulation laser to the π-FBG sensor, so that the demodulation laser is reflected as a detection laser under the action of the ultrasonic echo, and the ultrasonic demodulation device is also used to receive the detection laser; The imaging device is connected to the ultrasonic demodulation device and is used to process and image the detection laser.

2. The all-optical ultrasonic imaging device according to claim 1, characterized in that: The demodulation laser is tuned within a certain wavelength range according to a certain time sequence, so that the wavelength range of the laser emitted at each moment is different; The wavelength of the short pulse laser does not fall within the wavelength range of the demodulation laser.

3. The all-optical ultrasonic imaging device according to claim 1, characterized in that: The short pulse laser is a pulse laser with a single wavelength.

4. The all-optical ultrasonic imaging device according to claim 1, characterized in that: The optical fiber catheter control assembly includes a rotor, a stator, a gear system and a prism component. The rotor rotates relative to the stator. The rotor drives the prism component to rotate through the gear system. The gear system allows the rotation speed of the prism component and the rotor relative to the stator to maintain a certain ratio value. The prism component is a prism combination that can achieve a predetermined ratio of the object-image rotation ratio. The rotor and the stator are both provided with two optical fiber collimators, and the optical axes of the two optical fiber collimators of the rotor and the two optical fiber collimators of the stator are parallel to the rotating axis of the rotor and are equidistant from the rotating axis. When the rotor rotates to a specific angle, the two optical fiber collimators of the rotor and the two optical fiber collimators of the stator are coaxial. Along the rotating axis direction of the rotor, the prism component is arranged between the rotor and the stator, and the light beams incident on the two optical fiber collimators of the stator are transmitted to the two optical fiber collimators of the rotor after passing through the prism component, and finally reach the probe.

5. The all-optical ultrasonic imaging device according to claim 1, characterized in that: The photoacoustic conversion composite film is provided with a concave curved surface, which is used to generate focused ultrasound when laser is incident on the photoacoustic transducer device.

6. The all-optical ultrasonic imaging device according to claim 5, characterized in that: The photoacoustic conversion composite film is arranged at the end of the excitation optical fiber, and is composed of a PDMS polymer film and a multi-walled carbon nanotube layer from the surface to the inside; A gold-plated layer is provided on the back side of the optical fiber opposite to the concave curved surface, which is used to reflect the light beam to the concave curved surface.

7. The all-optical ultrasonic imaging device according to claim 6, characterized in that: The method of disposing the photoacoustic conversion composite film at the end of the excitation optical fiber comprises: S1, grinding the end and etching a concave surface; S2, the optical fiber end obtained in step S1 is immersed in a multi-walled carbon nanotube gel to obtain a multi-walled carbon nanotube layer by a immersion and pulling method; S3, the optical fiber end obtained in step S2 is immersed in the PDMS solution to obtain a PDMS polymer film by a PDMS pulling method.

8. The all-optical ultrasonic imaging device according to claim 1, characterized in that: Along the radial direction of the probe, the photoacoustic conversion composite film, the demodulation optical fiber probe and the excitation optical fiber probe are arranged in sequence; The probe further includes an ultrasonic shielding plate, the length of the excitation optical fiber probe extending from the optical fiber entrance into the probe is greater than the length of the demodulation optical fiber probe extending from the optical fiber entrance into the probe, and along the length direction of the probe, the ultrasonic shielding plate separates the π-FBG sensor and the end of the excitation optical fiber probe; The end of the excitation optical fiber probe is provided with a polished bevel, and the polished bevel is coated with a metal reflective film, so that the laser transmitted to the end is reflected by the polished bevel and then incident on the photoacoustic conversion composite film; The axis of the ultrasonic wave emission direction of the photoacoustic conversion composite membrane and the axis of the ultrasonic echo receiving direction of the π-FBG sensor form a preset angle.

9. The all-optical ultrasonic imaging device according to claim 1, characterized in that: Along the radial direction of the probe, the photoacoustic conversion composite film, the excitation optical fiber probe and the demodulation optical fiber probe are arranged in sequence; The probe further includes an ultrasonic shielding plate, the length of the excitation optical fiber probe extending from the optical fiber entrance into the probe is shorter than the length of the demodulation optical fiber probe extending from the optical fiber entrance into the probe, and along the length direction of the probe, the ultrasonic shielding plate separates the π-FBG sensor and the end of the excitation optical fiber probe; The end of the excitation optical fiber probe is provided with a polished bevel, and the polished bevel is coated with a metal reflective film, so that the laser transmitted to the end is reflected by the polished bevel and then incident on the photoacoustic conversion composite film; The axis of the ultrasonic wave emission direction of the photoacoustic conversion composite membrane and the axis of the ultrasonic echo receiving direction of the π-FBG sensor form a preset angle.

10. The all-optical ultrasonic imaging device according to any one of claims 8 or 9, characterized in that: The probe also includes a round tip housing, a retainer, and a twisted spring; The retainer is fixedly connected to the circular tip housing and the demodulation optical fiber at two radially opposite surfaces respectively; The twisted spring is arranged at the entrance end of the probe connected to the optical fiber, and the inner side of the twisted spring wraps the excitation optical fiber and the demodulation optical fiber.

11. The all-optical ultrasonic imaging device according to claim 10, characterized in that: The all-optical ultrasonic imaging device also includes a catheter transmission part and a catheter connector; the connecting end of the optical fiber catheter control component and the probe is provided with an optical fiber connector; the probe is connected to the catheter transmission part, the catheter connector and the optical fiber connector in sequence.

12. The all-optical ultrasonic imaging device according to claim 1, characterized in that: The optical fiber catheter control component includes an optical fiber slip ring with an optical filter component, so that the optical path where the ultrasonic demodulation light is located allows the ultrasonic demodulation light to pass through and cuts off the ultrasonic excitation light.

13. The all-optical ultrasonic imaging device according to claim 1, characterized in that: The ultrasonic demodulation device comprises: a demodulation laser component, a fiber coupler and a fiber circulator, wherein: The demodulation laser component is used to emit the demodulation laser; The optical fiber coupler is used to couple the light beam transmitted through air into the optical multimode optical fiber for transmission; The optical fiber circulator is used to output the demodulated laser to the π-FBG sensor, and is used to output the detection laser to the imaging device.

14. The all-optical ultrasonic imaging device according to claim 13, characterized in that: The imaging device comprises: a photoelectric detector, a data acquisition card and a computer, wherein: The photodetector is used to receive the detection laser and convert the optical signal of the detection laser into an electrical signal; The data acquisition card is used to collect the electrical signal and quantize the electrical signal into a digital signal; The computer is used to receive the digital signal, and perform data processing and ultrasonic imaging on the digital signal; The optical fiber catheter control component includes a high-speed optical fiber slip ring, which cooperates with the data acquisition card and the photoelectric detector to achieve high-speed image acquisition.

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