An optical fiber ablation probe capable of sensing contact pressure

Abstract

The application discloses a fiber ablation probe capable of sensing contact force with tissue, and a microspherical functional structure is designed at the end of the probe. The functional structure is composed of PDMS silicone rubber material doped with gold nanoparticles (GNPs), and a high-reflectivity coating is coated on the surface of the functional structure to provide high reflection to a detection light signal. By utilizing the localized surface plasmon resonance (LSPR) characteristics of the GNPs, the real-time detection of stress can be realized by detecting the LSPR peak intensity change of the reflected light signal. At the same time, by utilizing the high photo-thermal conversion efficiency of the GNPs, the thermal ablation of the target tissue can be realized. The fiber ablation probe provided by the application can provide the contact force information between the probe and the tissue in real time while performing the cardiac photo-thermal ablation, and can effectively improve the operation accuracy and reduce the operation risk.

Description

(I) Technical Field

[0001] This invention relates to an optical fiber ablation probe capable of sensing contact force with tissue, combined with localized plasma resonance (LSPR) technology, for use in cardiac thermal ablation surgery and real-time stress monitoring during the procedure, belonging to the fields of optical detection and organic material application technology. (II) Background Technology

[0002] The heart is one of the most vital organs in the human body, providing power to the circulatory system. Normal arteries supply blood to the heart; once these vessels become blocked, it can easily lead to myocardial ischemia, hypoxia, or necrosis, causing cardiovascular disease. With the increasing aging population and changes in lifestyle, the incidence of cardiovascular disease is rising rapidly, becoming the leading cause of death worldwide, characterized by high morbidity, high disability rates, and high mortality rates. According to the World Health Organization (WHO), approximately 17.9 million people die from cardiovascular disease each year, accounting for about 30% of all deaths globally—equivalent to one in three deaths. This number is projected to rise to approximately 24 million by 2030. my country has the highest cardiovascular disease mortality rate globally, with cardiovascular disease accounting for over 40% of all deaths, and the current number of patients reaching as high as 330 million. The prevention and treatment of cardiovascular disease is therefore urgent. Currently, thermal ablation technology is the main treatment method for cardiovascular diseases such as arrhythmia (atrial fibrillation) and atherosclerosis. Traditional thermal ablation primarily relies on radiofrequency or microwave principles. A catheter is placed at the lesion site, releasing heat energy to ablate the target tissue. Therefore, monitoring the contact force between the instrument and the tissue is a crucial aspect of cardiac ablation. However, manual instrument control cannot guarantee uniform force application; excessive force can lead to complications such as perforation, while insufficient force prolongs ablation time and increases the ablation area. Real-time contact force monitoring can help surgeons improve thermal ablation efficiency and reduce surgical risks for patients. (III) Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide an optical fiber ablation probe with tissue contact force detection, which can provide real-time contact force information between the probe and the tissue while performing cardiac ablation.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] The fiber optic ablation probe adopts an all-fiber structure design, possessing both photothermal ablation and pressure-tactile sensing functions. The end face of the fiber is designed with a microspherical functional structure, characterized in that the functional structure is composed of PDMS silicone rubber material doped with gold nanoparticles (GNPs), and its surface is coated with a high-reflectivity coating to provide high reflectivity for the probe light signal.

[0006] The microspherical functional structure has soft mechanical properties, which can adapt to the mechanical properties of soft tissues. It utilizes the localized surface plasmon resonance (LSPR) effect of GNPs to achieve high-sensitivity detection of pressure. When the structure is subjected to stress, the reflected light exhibits the characteristic of linear intensity output.

[0007] The GNPs have high photothermal conversion efficiency, which can effectively convert light energy into heat energy, thereby achieving thermal ablation of the target tissue.

[0008] The high-reflectivity coating on the surface of the microspherical functional structure is a PDMS material with a porous structure prepared using a NaCl template. It exhibits high reflectivity, providing a reflectivity of over 90%. Optimal, the coating thickness is 300-500 μm.

[0009] The optical fiber ablation probe uses a 6+1 fiber bundle design, consisting of a central illumination fiber and six outer rings of reflective light collection fibers, in order to improve the detection level of reflected light signals.

[0010] The fiber optic ablation probe is characterized by its preparation method comprising the following steps:

[0011] Step (1): Mix the PDMS monomer and its curing agent thoroughly at a certain volume ratio (10:1 or 5:1), and then remove the internal gas components from the prepolymer under vacuum.

[0012] Step (2): Add gold salt HAuCl4 to the PDMS obtained in step (1), stir the mixture of gold salt and PDMS thoroughly, and place it in an ultrasonic bath for 30 minutes to obtain uniformly dispersed GNPs (the ultrasonic bath is carried out in an ice-water mixture to prevent PDMS from rapidly polymerizing through ultrasonic heating).

[0013] Step (3): Using the dip-pull method, the end of the optical fiber is vertically immersed into the GNPs-PDMS prepolymer solution prepared in step (2), and then the optical fiber is vertically pulled up from the solution at a low speed. Under the action of gravity, microspheres are formed on the end face of the optical fiber, and then cured at room temperature for 72 hours.

[0014] Step (4): A PDMS material with a porous structure was prepared using a NaCl template as a high-reflectivity coating. 5 mL of a 4M NaCl aqueous solution was added dropwise to 100 mL of 99.8% ethanol under strong magnetic stirring. After reacting for 5 minutes, the mixture was centrifuged (1000 rpm, 2 minutes), washed with ethanol, and the white precipitate was collected. Finally, the sample was dried in an oven at 80℃ for 12 hours to obtain NaCl powder.

[0015] Step (5): Collect the NaCl powder from step (4) as a sacrificial template, add PDMS prepolymer (monomer and curing agent at a mass ratio of 10:1) at a ratio of 5:1, and after thorough stirring, place the mixture in a vacuum environment to remove the internal gas components to obtain a high-reflectivity PDMS coating.

[0016] Step (6): The high-reflectivity PDMS coating prepared in step (5) is coated onto the surface of the optical fiber microspheres obtained in step (3) using an impregnation-coating method. The fiber end is then cured at 120°C for 12 hours, followed by immersion in deionized water at 40°C for 48 hours to remove NaCl particles. Finally, the optical fiber ablation probe is dried in a 40°C oven for 12 hours.

[0017] The working principle of this invention is as follows: The microspherical functional structure at the end of the fiber optic ablation probe is made of elastic PDMS material doped with GNPs. Due to the localized surface plasmon resonance effect of GNPs, it exhibits a strong absorption effect for specific wavelengths. When the tip of the fiber optic ablation probe is subjected to external pressure, the elastic microspherical functional structure is compressed and deformed, resulting in a reduction in the absorption optical path. Since the number of GNPs and the volume of the microspheres remain constant, the absorption intensity of the LSPR decreases with increasing pressure, ultimately resulting in a reduction in absorption loss. To achieve reflective photodetection, a highly reflective material is coated on the outer surface of the microspheres to reflect the probe light signal to the optical fiber for collection. The reflective coating increases the interaction optical path between the probe light and the GNPs, which is beneficial for improving the sensitivity of pressure sensing. By establishing the relationship between the light reflection intensity at the peak wavelength of the LSPR and the magnitude of the applied stress, quantitative detection of pressure can be achieved. In addition, GNPs also have excellent photothermal conversion characteristics. Under laser irradiation, the light generates a strong electric field, causing charge carrier movement and releasing heat energy. Utilizing the high photothermal conversion efficiency of GNPs, thermal ablation of the target tissue can be achieved.

[0018] The present invention also provides an experimental device based on the optical fiber ablation probe 5, the device comprising: a laser 1, an illumination optical fiber 2, an optical fiber coupler, a multimode optical fiber bundle 4, a reflected light collecting optical fiber 6, a photodetector 7, a data acquisition card 8, and a computer 9.

[0019] 1) The relationships between the components of the experimental setup are as follows: The output laser port 1-1 of laser 1 is connected to the first port 3-1 of fiber coupler via illumination fiber 2. The output laser from the third port 3-3 of fiber coupler is coupled into multimode fiber bundle 4, transmitting light energy to the fiber ablation probe 5. The laser transmitted to the micro-spherical functional structure 5-1 at the end of the fiber ablation probe 5 is reflected. The reflected laser is coupled through multimode fiber bundle 4 to the third port 3-3 of fiber coupler and output through the second port 3-2 of fiber coupler. The output light from the second port 3-2 of fiber coupler is transmitted to the photodetector port 7-1 via reflected light collecting fiber 6 for reception and conversion into a voltage signal. The output port 7-2 of the photodetector is connected to the data acquisition card port 8-1 via a BNC signal line for acquisition. The acquisition results are input into the computer 9 for processing via the data acquisition card.

[0020] 2) In the experimental setup, the laser operates at the LSPR peak wavelength of GNPs to achieve the highest pressure sensitivity and photothermal conversion efficiency.

[0021] 3) In the experimental setup, the fiber coupler 3 contains one illumination fiber 2 and six reflective light collecting fibers 6 for transmitting the reflected light signal from the fiber ablation probe.

[0022] 4) In the experimental setup, the light signal emitted by the laser 1 is transmitted through an illumination fiber to the microsphere functional structure solidified on the end face of the fiber, and then reflected back to the photodetector 7 via a highly reflective material coated on the outer surface of the microsphere functional structure and six reflective light collecting fibers to measure the intensity of the reflected light.

[0023] 5) In the experimental setup, the magnitude of the light intensity acquired by the data acquisition card 8 and the magnitude of the applied external force are basically linearly related in logarithmic coordinates. External stress information is obtained by calculating and outputting the light intensity.

[0024] This invention has advantages over existing technologies:

[0025] 1) The microspherical functional structure at the end of the fiber optic ablation probe is prepared using PDMS polymer material modified with gold nanoparticles. It has soft mechanical properties and can achieve good mechanical matching with equally soft biological tissues.

[0026] 2) By utilizing the LSPR effect of GNPs, the target tissue can be thermally ablated while monitoring external stress. It has good repeatability and can achieve long-term stable operation.

[0027] 3) By using a single-end reflective structure for detection, the interaction length between the signal light and the sensing fiber is increased, thereby improving the sensitivity and photothermal conversion efficiency of the fiber optic ablation probe. (iv) Description of the attached drawings

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the experimental setup for an optical fiber ablation probe.

[0030] Figure 2 This is a schematic diagram of the microsphere functional structure at the end of the fiber optic ablation probe.

[0031] icon:

[0032] 1: Laser; 1-1: Laser output port; 2: Illumination fiber; 3-1: First port of fiber coupler; 3-2: Second port of fiber coupler; 3-3: Third port of fiber coupler; 4: Multimode fiber bundle; 5: Fiber ablation probe; 5-1: Microsphere functional structure; 6: Reflected light collecting fiber; 7: Photodetector; 7-1: Input port of photodetector; 7-2: Output port of photodetector; 8: Data acquisition card; 8-1: Input port of data acquisition card; 9: Computer. (V) Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The specific preparation process of the invented fiber optic ablation probe is as follows:

[0035] Step (1) Synthesize and prepare PDMS prepolymer: Mix PDMS monomer and its curing agent thoroughly at a volume ratio of 5:1, and then remove the internal gas components of the prepolymer under vacuum.

[0036] Step (2) Preparation of GNP-PDMS sensing material: Gold salt HAuCl4 (doping concentration of 0.1% mg / ml) was added to the PDMS obtained in step (1). After thoroughly stirring the mixture of gold salt and PDMS, it was placed in an ultrasonic bath for 30 minutes to obtain uniformly dispersed GNP (the ultrasonic bath was carried out in an ice-water mixture to prevent PDMS from rapidly polymerizing by ultrasonic heating).

[0037] Step (3) Preparation of GNP-PDMS fiber ablation probe: Using the dip-pull method, the end of the fiber is vertically immersed into the GNP-PDMS prepolymer solution prepared in step (2) and pulled up vertically at low speed. Under the action of gravity, microspheres are formed on the end face of the fiber end, and then cured at room temperature for 72 hours.

[0038] Step (4): Prepare PDMS material with a porous structure as a high-reflectivity coating using NaCl template: Add 5 mL of NaCl aqueous solution (4M) dropwise to 100 mL of ethanol (99.8%) under strong magnetic stirring. After reacting for 5 minutes, centrifuge (1000 rpm, 2 minutes), wash with ethanol, and collect the white precipitate. Dry the sample in an oven at 80℃ for 12 hours.

[0039] Step (5): Collect the NaCl powder from step (4) as a sacrificial template, add PDMS prepolymer (monomer and curing agent at a mass ratio of 10:1) at a ratio of 5:1, and after thorough stirring, place the mixture in a vacuum environment to remove the internal gas components to obtain a high-reflectivity PDMS coating.

[0040] Step (6): The high-reflectivity PDMS coating prepared in step (5) was applied to the surface of the optical fiber microspheres obtained in step (3) using an impregnation-coating method. The end of the optical fiber was then cured at 120°C for 12 hours, and then immersed in deionized water at 40°C for 48 hours to remove NaCl particles. Finally, the optical fiber ablation probe was dried in an oven at 40°C for 12 hours. Figure 1 This is a schematic diagram of the fiber optic ablation probe experimental setup. The fabricated fiber optic microsphere functional structure is shown below. Figure 2 As shown. The specific devices used in this embodiment are: laser 1 with a wavelength of 532nm; fiber optic coupler 3 with a splitting ratio of 50:50; fiber optic ablation probe 5 consisting of 7 infrared quartz fibers with a core diameter of 200μm and a length of 50cm, protected by a PVC pipe with an outer diameter of 2mm; photodetector 7 with a response wavelength range of 400-1100nm; data acquisition card 8 with a sampling rate of 200kS / s; and computer 9 used to store and process the acquired data.

[0041] The specific process of this embodiment of the invention is as follows:

[0042] 1) The laser's output port 1-1 is connected to the first port 3-1 of the fiber coupler via the illumination fiber 2. The output laser from the third port 3-3 of the fiber coupler is coupled into the multimode fiber bundle 4, transmitting the light energy to the fiber ablation probe 5. The laser is transmitted to the micro-spherical functional structure 5-1 at the end of the fiber ablation probe and reflected. The reflected laser is coupled back to the third port 3-3 of the fiber coupler via the multimode fiber bundle 4 and output through the second port 3-2 of the fiber coupler. The output light from the second port 3-2 of the fiber coupler is transmitted to the photodetector port 7-1 via the reflected light collecting fiber 6, where it is received and converted into a voltage signal. The output signal from the photodetector port 7-2 is acquired by the data acquisition card port 8-1, and the acquisition result is sent to the computer 9 for storage and processing via the data acquisition card.

[0043] 2) In the experimental setup, the laser operates at the LSPR peak wavelength of GNPs to achieve the highest pressure sensitivity and photothermal conversion efficiency.

[0044] 3) In the experimental setup, the light emitted by the laser 1 is transmitted through an illumination fiber to the microspherical functional structure solidified on the end face of the fiber, and then reflected back to the photodetector 7 via a highly reflective material coated on the outer surface of the microspherical functional structure and six reflective light collecting fibers to measure the intensity of the reflected light.

[0045] 4) In the experimental setup, the magnitude of the light intensity acquired by the data acquisition card 8 and the magnitude of the applied external force are basically linearly related in logarithmic coordinates. External stress information is obtained by calculating and outputting the light intensity.

[0046] This invention employs an all-fiber structure design for the fiber optic ablation probe, simultaneously possessing photothermal ablation and pressure tactile sensing functions. The end face of the fiber optic cable features a microspherical functional structure made of elastic PDMS material doped with GNPs. Due to the localized surface plasmon resonance effect of GNPs, they exhibit strong absorption at specific wavelengths. When the fiber optic ablation probe tip is subjected to external pressure, the elastic microspherical functional structure is compressed and deformed, resulting in a reduction in the absorption optical path. Since the number of GNPs and the volume of the microspheres remain constant, the absorption intensity of the LSPR decreases with increasing pressure, ultimately manifesting as a reduction in absorption loss. The outer surface of the microspheres is coated with a highly reflective material, enabling reflective photodetection and increasing the interaction optical path between the probe light and the GNPs, thus improving the sensitivity of pressure sensing. By detecting changes in the LSPR peak intensity of the reflected light signal, real-time, quantitative detection of pressure can be achieved. Furthermore, GNPs possess excellent photothermal conversion characteristics; under laser irradiation, the light generates a strong electric field, inducing carrier motion and releasing heat energy. Utilizing the high photothermal conversion efficiency of GNPs, thermal ablation of target tissues can be achieved. The fiber optic ablation probe integrates photothermal ablation and pressure tactile sensing functions, meeting the requirement of providing real-time contact force information during surgery and solving the problem of uncontrollable contact force between traditional thermal ablation devices and tissues.

Claims

1. A fiber optic ablation probe capable of sensing contact force with tissue, used for cardiac thermal ablation surgery and real-time stress monitoring during the procedure; characterized in that, The fiber optic ablation probe has a microspherical functional structure at its end face, which is made of PDMS silicone rubber material doped with gold nanoparticles (GNPs). The GNPs are used for both pressure detection based on localized surface plasmon resonance (LSPR) and tissue ablation based on high photothermal conversion effect. The surface of the microspherical functional structure is coated with a highly reflective elastic coating to provide high reflectivity for the probe light signal; Therefore, the fiber optic ablation probe integrates pressure detection and photothermal ablation functions at its end.

2. The fiber optic ablation probe according to claim 1, characterized in that, The fiber optic ablation probe utilizes the high photothermal conversion efficiency of gold nanoparticles (GNPs) to convert light energy into heat energy, thereby achieving ablation treatment of target tissues.

3. The fiber optic ablation probe according to claim 1, characterized in that, The pressure detection is achieved by monitoring the changes in the intensity of the local surface plasmon resonance absorption peak of GNPs.

4. The fiber optic ablation probe according to claim 1, characterized in that, The fiber optic ablation probe adopts a 6+1 multimode fiber bundle design, consisting of one illumination fiber surrounding the center and six outer layers of reflective light collection fibers.

5. The fiber optic ablation probe according to claim 1, characterized in that, The high-reflectivity coating on the surface of the functional structure is a PDMS material with a porous structure prepared using a NaCl template. It has high reflectivity and can provide a reflectivity of up to 90% or more.

6. The fiber optic ablation probe according to claim 1, characterized in that, The method for preparing the functional structure includes the following steps: Step (1): Mix the PDMS base monomer and its curing agent thoroughly at a volume ratio of 5:1, and then remove the internal gas components from the prepolymer under vacuum. Step (2): Add gold salt HAuCl4 to the PDMS obtained in step (1), stir the mixture of gold salt and PDMS thoroughly, and place it in an ultrasonic bath for 30 minutes to obtain uniformly dispersed GNPs; wherein, the ultrasonic bath is carried out in an ice-water mixture to prevent PDMS from rapidly polymerizing by ultrasonic heating. Step (3): Using the dip-pull method, the end of the optical fiber is vertically immersed into the GNPs-PDMS prepolymer solution prepared in step (2), and then the optical fiber is vertically pulled up from the solution at a low speed. Under the action of gravity, microspheres are formed on the end face of the optical fiber, and then cured at room temperature for 72 hours. Step (4): PDMS material with a porous structure was prepared using NaCl template as a high-reflectivity coating. 5 mL of 4M NaCl aqueous solution was added dropwise to 100 mL of 99.8% ethanol under strong magnetic stirring. After reacting for 5 minutes, the mixture was centrifuged at 1000 rpm for 2 minutes, washed with ethanol, and the white precipitate was collected. The sample was then dried in an oven at 80℃ for 12 hours. Step (5): The NaCl powder collected in step (4) is used as a sacrificial template and PDMS prepolymer is added at a mass ratio of 5:

1. The PDMS prepolymer is made by mixing monomers and curing agents at a mass ratio of 10:

1. After thorough stirring, the mixture is placed in a vacuum environment to remove the internal gas components and obtain a high-reflectivity PDMS coating. Step (6): The high-reflectivity PDMS coating prepared in step (5) is coated onto the surface of the optical fiber microspheres obtained in step (3) using the immersion-coating method; then the end of the optical fiber is cured at 120°C for 12 hours, and then immersed in deionized water at 40°C for 48 hours to remove NaCl particles; finally, the optical fiber ablation probe is dried in an oven at 40°C for 12 hours.

7. An experimental apparatus comprising the fiber optic ablation probe (5) as described in claim 1, characterized in that, include: Laser (1), illumination fiber (2), fiber coupler, multimode fiber bundle (4), reflected light collecting fiber (6), photodetector (7), data acquisition card (8), and computer (9); The laser output port (1-1) of the laser (1) is connected to the first port (3-1) of the fiber coupler via the illumination fiber (2), and is coupled into the multimode fiber bundle (4) through the fiber coupler to transmit the light energy to the fiber ablation probe (5). The light signal output by the laser (1) is reflected by the micro-spherical functional structure (5-1) at the end of the fiber ablation probe (5) and then coupled to the second port (3-2) of the fiber coupler via the third port (3-3) of the fiber coupler. The output light of the second port (3-2) of the fiber coupler is transmitted to the input port (7-1) of the photodetector (7) via the reflected light collection fiber (6) and received and converted into a voltage signal. The output port (7-2) of the photodetector (7) is connected to the data acquisition card via the BNC signal line and is collected by the port (8-1) of the data acquisition card (8). The acquisition result is sent to the computer (9) for storage and processing through the data acquisition card.

8. The experimental apparatus according to claim 7, characterized in that, The light signal emitted by the laser (1) is transmitted through an illumination fiber to a microsphere functional structure solidified on the end face of the fiber, and then reflected back to the photodetector (7) via a highly reflective material coated on the outer surface of the microsphere functional structure and six reflective light collecting fibers to measure the intensity of the reflected light.

9. The experimental apparatus according to claim 7, characterized in that, The laser (1) operates at the plasmon resonance absorption peak of GNPs to achieve the highest pressure sensitivity and photothermal conversion efficiency.

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