Microwave ablation antenna with adjustable and controllable ablation area

Abstract

The microwave ablation antenna comprises an ablation antenna body, one end of the ablation antenna body is connected with an SMA connector to be connected with a coaxial cable, the other end of the ablation antenna body is an antenna tail end, the microwave ablation antenna further comprises a copper reflecting surface and a matching network, and the copper reflecting surface and the matching network are both installed at the positions close to the antenna tail end. The distance between the matching network and the tail end of the antenna is larger than the distance between the copper reflecting surface and the tail end of the antenna, the copper reflecting surface comprises multiple sections of concentric and same-radius arc-shaped reflecting surfaces with different opening angles, the arc-shaped reflecting surfaces are used for controlling focusing and distribution of microwave energy, and the matching network is used for realizing impedance matching between a signal source and a load. On the premise that the structure is compact and the invasiveness to a human body is low, flexible regulation and control of an omnidirectional and directional ablation area can be realized under a similar antenna structure by finely adjusting part of parameters of the reflecting surface.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave ablation, and in particular relates to a microwave ablation antenna with an adjustable ablation area. Background Art

[0002] In recent years, microwave ablation technology has developed rapidly. This technology mainly uses the electromagnetic field within the microwave frequency range to generate heat energy, so that the lesion tissue reaches a very high temperature in a short period of time, coagulates and necrotizes, thereby achieving the purpose of ablation treatment. As a key component in the microwave ablation process, the microwave ablation antenna is percutaneously inserted into the tumor tissue under the guidance of ultrasound, CT or MRI images to accurately transmit high-frequency electromagnetic energy.

[0003] When the shape of the tumor is close to a sphere, a large and round omnidirectional radiation area is ideal. However, when the tumor is irregular in shape or close to important organs or blood vessels, a microwave ablation antenna with a directional radiation area can avoid unnecessary damage. Although different designs can be used to realize microwave ablation antennas with omnidirectional and directional radiation areas, it is necessary to ensure that the structure is simple and easy to process, while achieving ideal radiation characteristics, which puts stringent requirements on the antenna design. In particular, it is necessary to achieve different radiation characteristics of antennas on similar structures, while ensuring a compact and low-invasive structure, which has become a difficult problem that antenna engineers need to solve urgently. Traditional microwave ablation antennas have the following problems: 1. It takes a long time, has low circularity and low directionality to achieve omnidirectional or directional ablation areas by manually or empirically optimizing parameters; 2. The structures of omnidirectional / directional microwave ablation antennas are very different and difficult to process and manufacture. Summary of the invention

[0004] The object of the present invention is to provide a microwave ablation antenna with an adjustable ablation area, so as to improve the directionality and ablation efficiency of the directional ablation area.

[0005] The technical solution to achieve the purpose of the present invention is: A microwave ablation antenna with an adjustable ablation area comprises an ablation antenna body, one end of the ablation antenna body is connected to an SMA connector and a coaxial cable, and the other end is an antenna end, and also comprises a copper reflecting surface and a matching network. The copper reflecting surface and the matching network are both installed at a position close to the antenna end, and the distance between the matching network and the antenna end is greater than the distance between the copper reflecting surface and the antenna end. The copper reflecting surface comprises a plurality of arc reflecting surfaces with the same center and radius and different opening angles, which are used to control the focusing and distribution of microwave energy, and the matching network is used to achieve impedance matching between a signal source and a load.

[0006] Furthermore, the multi-stage opening angles are optimized by using MATLAB and COMSOL joint simulation and genetic algorithm NSGA-Ⅱ.

[0007] Furthermore, the copper reflection surface includes a first reflection surface, a second reflection surface and a third reflection surface, and the three reflection surfaces form a three-reflection surface node, the first reflection surface is farthest from the end of the antenna, and the second reflection surface is located between the first reflection surface and the third reflection surface.

[0008] Furthermore, the heights of the first reflecting surface, the second reflecting surface and the third reflecting surface are all 0.67 mm.

[0009] Furthermore, the opening angle of the first reflecting surface is 35.85°, the opening angle of the second reflecting surface is 74.53°, and the opening angle of the third reflecting surface is 153.11°.

[0010] Furthermore, the opening angle of the first reflecting surface is 281.95°, the opening angle of the second reflecting surface is 198.47°, and the opening angle of the third reflecting surface is 229.45°.

[0011] Furthermore, the matching network adopts λ / 4 matching mode, the parameters of the matching network are optimized using the quasi-Newton method.

[0012] Furthermore, the ablation antenna body comprises an inner conductor, and the outer side of the inner conductor is sequentially coated with a PTFE medium, an outer conductor and an outer shell.

[0013] Furthermore, the copper reflective surface is mounted on the outer conductor by interference fit.

[0014] Furthermore, the outer conductor and PTFE medium near the end of the antenna are stripped off, and the matching network is connected to the inner conductor by welding. Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention proposes a copper reflective surface with multiple sections and different opening angles, and by reasonably designing the reflective surface angle, effectively controls the focusing and distribution of microwave energy, thereby improving the ablation effect and safety; the present invention adopts a quarter-wavelength matching network, and utilizes the characteristics of a quarter-wavelength transmission line to realize impedance conversion, thereby achieving the purpose of impedance matching between the signal source and the load; the microwave ablation antenna designed by the present invention has a simple structure, has the characteristics of adjustable radiation direction, and is suitable for different tumor sizes and locations, reduces the need for reprocessing due to design changes, reduces processing costs, and simplifies the processing process, and is easy to achieve mass production, and has potential application value in tumor ablation in various clinical scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1The figure is an overall cross-sectional view of a microwave ablation antenna with an adjustable ablation area.

[0016] Figure 2 This is a specific schematic diagram of the first type of copper reflective surface.

[0017] Figure 3 Schematic diagram of the second copper reflective surface.

[0018] Figure 4 This is a return loss diagram of a microwave ablation antenna with adjustable ablation area.

[0019] Figure 5 This is the tissue necrosis rate distribution map of the microwave ablation antenna with adjustable ablation area.

[0020] Explanation of reference numerals: 1. ablation antenna body; 101. inner conductor; 102. PTFE medium; 103. outer conductor; 104. housing; 2. copper reflection surface; 201. first reflection surface; 202. second reflection surface; 203. third reflection surface; 3. matching network DETAILED DESCRIPTION

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0022] Example 1

[0023] like Figure 1 As shown, a microwave ablation antenna with an adjustable ablation area is used to produce a highly directive directional ablation area. The antenna includes an ablation antenna body 1, which includes an inner conductor 101. The outer side of the inner conductor 101 is sequentially coated with a PTFE medium 102, an outer conductor 103 and an outer shell 104. One end of the body is connected to an SMA connector and a coaxial cable, and the other end is the antenna end. The outer conductor 103 and the PTFE medium 102 near the antenna end are stripped off, and a matching network 3 is stably connected to the inner conductor 101 by welding; a copper reflective surface 2 is installed on the outer conductor 103 near the antenna end by interference fit.

[0024] like Figure 2 As shown, on the basis of Example 1, the reflecting surface 2 includes a first reflecting surface 201, a second reflecting surface 202 and a third reflecting surface 203 which are sequentially away from the end of the antenna. The first reflecting surface 201, the second reflecting surface 202 and the third reflecting surface 203 form a three-reflecting surface node. Through the reflection effect of the three-reflecting surface node, the field generated by the antenna is constructive interference in the desired direction, while the field behind the reflector is destructive interference, thereby achieving the purpose of directional radiation.

[0025] Among them, the three reflecting surfaces include a first reflecting surface 201, a second reflecting surface 202 and a third reflecting surface 203 which are successively away from the end of the antenna. The opening angles of the three reflecting surfaces are different. In this example, the three design parameters of the three reflecting surfaces (the opening angles of the three reflecting surfaces) are optimized by joint simulation of MATLAB and COMSOL and genetic algorithm NSGA-Ⅱ, so that the microwave ablation antenna with an adjustable radiation area of ​​the present invention has a larger roundness in the omnidirectional heating mode and a higher directivity in the directional heating mode, can adapt to different clinical scenarios, and avoid unnecessary damage.

[0026] like Figure 1 As shown, the antenna is a monopole antenna with a length of 95 mm, an inner conductor 101 with a diameter of 0.93 mm, a PTFE medium 102 with a thickness of 2.05 mm, an outer conductor 103 with a diameter of 3.58 mm, and a shell 104 with a thickness of 1.42 mm.

[0027] The matching network 3 adopts λ / 4 matching mode, in λ A section of Teflon dielectric is removed from the / 4 matching section, and the diameter of the inner conductor of the section is modified. A gap is created between the matching network 3 and the outer conductor 103 and filled with air. According to the transmission line theory, removing the dielectric between the outer conductor and the inner conductor and changing the diameter of the inner conductor can change the capacitance per unit length of the coaxial cable. Therefore, by optimizing, we can change the equivalent capacitance and inductance values ​​by changing the various parameters of the quarter-wavelength matching section, thereby adjusting the overall impedance of the antenna to achieve impedance matching with the coaxial cable.

[0028] Said λ / 4 The design parameters of the matching network, namely the design parameters of the dielectric hollow segment and the conductor in the segment (the distance between the dielectric hollow segment and the end of the antenna, the length of the dielectric hollow segment, and the inner diameter of the conductor in the dielectric hollow segment) are optimized using the Quasi-Newton algorithm in ANSYS HFSS. The design parameters of the dielectric hollow segment and the conductor in the segment meet the following requirements: the distance between the dielectric hollow segment and the end of the antenna is 21.05 mm, the length of the dielectric hollow segment is 28.35 mm, and the diameter of the conductor in the dielectric hollow segment is 5.04 mm.

[0029] Return loss is an important parameter to measure the antenna matching performance. The smaller the value, the better the antenna impedance matching. λ The / 4 matching network optimizes the unit capacitance and inductance of the coaxial cable by removing a section of Teflon dielectric and changing the diameter of the inner conductor, so that the antenna and the coaxial cable achieve better impedance matching. Figure 4It can be seen that after this design optimization, the return loss of the directional and omnidirectional microwave ablation antennas is less than -10 dB in the target operating frequency band, which means that 90% of the energy enters the antenna. This shows that the reflected power of the antenna is effectively controlled, the matching effect is excellent, and the energy transmission loss is small.

[0030] Example 2

[0031] On the basis of Example 1, Figure 2 As shown, the design parameters of the three reflective surfaces provided in this embodiment meet the following requirements: the heights of the three reflective surfaces are all 0.67 mm, the opening angle of the first reflective surface is 35.85°, the opening angle of the second reflective surface is 74.53°, and the opening angle of the third reflective surface is 153.11°.

[0032] Example 3

[0033] On the basis of Example 1, Figure 3 As shown, the design parameters of the three reflecting surfaces provided in this embodiment meet the following requirements: the heights of the three reflecting surfaces are all 0.67 mm, the opening angle of the first reflecting surface is 281.95°, the opening angle of the second reflecting surface is 198.47°, and the opening angle of the third reflecting surface is 229.45°.

[0034] Through the design and optimization of the antenna, the electromagnetic wave energy is effectively focused and transmitted to the target tissue area, causing heating or electromagnetic radiation effects on specific biological tissues, thereby leading to tissue necrosis. The design parameters of the three reflective surfaces (the opening angles of the three reflective surfaces) are optimized by the genetic algorithm NSGA-Ⅱ, further improving the accuracy of the antenna in controlling the ablation area. Figure 5 It can be seen that in the omnidirectional heating mode, the antenna can achieve a high circularity ablation area of ​​91%, and in the directional heating mode, a high directivity ablation area of ​​83.3% can be obtained, achieving the expected effect.

[0035] 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. A microwave ablation antenna with an adjustable ablation area, comprising an ablation antenna body (1), one end of the ablation antenna body (1) is connected to an SMA connector and a coaxial cable, and the other end is an antenna end, characterized in that: It also comprises a copper reflecting surface (2) and a matching network (3), wherein the copper reflecting surface (2) and the matching network (3) are both installed at a position close to the end of the antenna, and the distance between the matching network (3) and the end of the antenna is greater than the distance between the copper reflecting surface (2) and the end of the antenna, and the copper reflecting surface (2) comprises a plurality of arc-shaped reflecting surfaces with the same center and radius and different opening angles, which are used to control the focusing and distribution of microwave energy, and the matching network (3) is used to achieve impedance matching between a signal source and a load.

2. The microwave ablation antenna with adjustable ablation area according to claim 1, characterized in that: The multi-stage opening angles are optimized by joint simulation using MATLAB and COMSOL and genetic algorithm NSGA-Ⅱ.

3. The microwave ablation antenna with adjustable ablation area according to claim 1, characterized in that: The copper reflection surface (2) comprises a first reflection surface (201), a second reflection surface (202) and a third reflection surface (203), the three reflection surfaces forming a three-reflection surface node, the first reflection surface (201) being farthest from the end of the antenna, and the second reflection surface (202) being located between the first reflection surface (201) and the third reflection surface (203).

4. The microwave ablation antenna with adjustable ablation area according to claim 3, characterized in that: The heights of the first reflecting surface (201), the second reflecting surface (202) and the third reflecting surface (203) are all 0.67 mm.

5. The microwave ablation antenna with adjustable ablation area according to claim 4, characterized in that: The opening angle of the first reflection surface (201) is 35.85°, the opening angle of the second reflection surface (202) is 74.53°, and the opening angle of the third reflection surface (203) is 153.11°.

6. The microwave ablation antenna with adjustable ablation area according to claim 4, characterized in that: The opening angle of the first reflection surface (201) is 281.95°, the opening angle of the second reflection surface (202) is 198.47°, and the opening angle of the third reflection surface (203) is 229.45°.

7. The microwave ablation antenna with adjustable ablation area according to claim 1, characterized in that: The matching network (3) adopts λ / 4 matching mode, the parameters of the matching network (3) are optimized using the quasi-Newton method.

8. The microwave ablation antenna with adjustable ablation area according to claim 1, characterized in that: The ablation antenna body (1) comprises an inner conductor (101), the outer side of the inner conductor (101) being covered with a PTFE medium (102), an outer conductor (103) and an outer shell (104) in sequence.

9. The microwave ablation antenna with adjustable ablation area according to claim 8, characterized in that: The copper reflection surface (2) is mounted on the outer conductor (103) by means of interference fit.

10. The microwave ablation antenna with adjustable ablation area according to claim 8, characterized in that: The outer conductor (103) and the PTFE medium (102) near the end of the antenna are stripped off, and the matching network (3) is connected to the inner conductor (101) by welding.

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