Low-radiation high-directivity antenna structure for microwave hyperthermia

Abstract

The invention provides a low-radiation high-directivity antenna structure for microwave hyperthermia, and relates to the technical field of medical microwave equipment antennas. Comprising an antenna radiator, two grounding metal columns, a metal substrate and a coaxial hose. The metal substrate is in sealed connection with one side of the microwave heating cavity, the two grounding metal columns are located in the microwave heating cavity, the grounding metal columns are perpendicular to the metal substrate and installed on the metal substrate, the two grounding metal columns are symmetrically arranged in a spaced mode, and the antenna radiator is parallel to the metal substrate and arranged on the upper portions of the grounding metal columns; and one end of the coaxial hose is connected with the antenna radiator, and the other end penetrates through the metal substrate, is positioned outside the microwave heating cavity and is used for externally connecting a solid-state microwave source. Through a reflecting surface structure formed by the elevated antenna radiator and the grounding metal column, the structure effectively inhibits sidelobe radiation and forms a concentrated main lobe by controlling a current return path and electromagnetic field distribution, so that microwave energy is accurately projected to a target tissue area, and the treatment depth and precision are improved.

Description

Technical Field

[0001] This invention relates to the field of antenna technology for medical microwave equipment, and more specifically, to a low-radiation, highly directional antenna structure for microwave thermotherapy. Background Technology

[0002] Microwave hyperthermia is a treatment method that utilizes high-frequency electromagnetic waves to generate a thermal effect in human tissues. Its basic principle is that microwaves act on water molecules within the tissue, causing them to rotate at high speed and generate heat through friction, thus raising the local temperature. Moderate heating (approximately 40–45°C) can improve blood circulation and relieve inflammation and pain, while higher temperatures (above 45°C) can induce tumor cell apoptosis or necrosis. Therefore, microwave hyperthermia can be used as an adjunct therapy for tumors and is also widely applied in inflammatory diseases and rehabilitation therapy. Compared to traditional infrared or radiofrequency heating, microwaves have stronger penetration and better temperature control precision, enabling non-invasive heating of subcutaneous or deep tissues. In recent years, microwave hyperthermia has also developed minimally invasive techniques such as microwave ablation and microwave scalpels, demonstrating unique advantages in tumor ablation, tissue cutting, and hemostasis. However, existing equipment still has shortcomings in energy focusing, directional control, energy utilization, and radiation suppression.

[0003] In existing technologies, the most common microwave hyperthermia solutions employ structures such as open dipole antennas or coaxial probes. These structures, based on the natural diffusion principle of microwave radiation, do provide a certain therapeutic effect for heating superficial tissues. For example, patent US5190054A proposes an improved coaxial microwave hyperthermia probe, which uses helical winding or variable-size slots on the outer conductor to create a more uniform heating pattern in both the axial and radial directions. However, this design has complex manufacturing processes, requiring extremely high precision in micron-level helical pitch or slot processing, increasing cost and mass production difficulty. The helical winding portion of flexible probes may loosen or break during insertion or bending, while the slot structure of rigid probes may weaken overall strength. Furthermore, the lack of active cooling and real-time temperature feedback mechanisms limits clinical applicability and safety, which may hinder its widespread application in actual medical practice.

[0004] Furthermore, existing research indicates that when the antenna structure lacks directional control, microwave energy can easily leak into non-target tissues, causing unnecessary radiation risks and reducing treatment safety. In clinical applications, individual patient differences and variations in tissue electrical parameters are even more significant, and traditional antenna structures are completely incapable of compensating for these complex conditions, resulting in a significant reduction in the intended focusing effect in practical applications. For example, patent document CN214074723U proposes a microwave hyperthermia device with adjustable installation position. This device uses an electric telescopic rod lifting mechanism and a motor reducer rotation mechanism on the base to adjust the treatment head in both vertical and horizontal directions, and braked sliding wheels at the four corners of the base for movement and fixation. While this solution improves the convenience of position adjustment, it still suffers from structural complexity, increased cost, and insufficient safety protection measures, failing to fundamentally address the comprehensive needs for flexibility, stability, and safety in clinical applications of microwave hyperthermia equipment.

[0005] The core of phase-controlled heating uniformity lies in using phase control of multiple antennas or patch arrays to coherently superimpose the electromagnetic fields of each radiating unit in the target tissue and rapidly change the phase combination to make the instantaneous energy peak continuously move within the tissue cross section. Since the scanning speed is much faster than the thermal diffusion time constant of the tissue, the local temperature does not have time to respond to the instantaneous peak, but instead manifests as a time-averaged power distribution, thereby forming a uniform thermal field on a macroscopic scale, achieving effective heating of deep tissues while avoiding local overheating.

[0006] In existing microwave hyperthermia techniques, a common approach is to use single-point or dual-waveguide antenna structures to concentrate microwave energy onto the lesion area. Theoretically, these structures can generate a thermal effect in localized tissues for tumor or inflammation treatment. However, their inherent drawbacks are significant: traditional devices require high output power to effectively heat deep tissues, leading to overheating and even burns on the skin surface, necessitating additional air cooling systems to alleviate patient pain. This not only increases system complexity but also reduces treatment efficiency. Furthermore, the waveguide antennas in existing devices have a fixed phase during multi-point heating, failing to create a uniform thermal field distribution within the tissue cross-section. They often only generate high temperatures at a single point or in a limited area, making it difficult to cover large lesions such as joints and muscles. More seriously, impedance mismatch often exists between the patch antenna and the skin, causing microwave leakage and the risk of localized burns. While cooling measures can reduce surface temperature, they also weaken the effectiveness of deep treatment. Patent US11511126B2 proposes a device for achieving heat transfer and uniform distribution through a flexible patch array and phase control, attempting to overcome the limitations of traditional equipment. However, it still faces problems such as complex system integration, cooling efficiency dependent on the medium, and insufficient adaptability to different patient tissue conditions. Patent document US2012172954A1 proposes a microwave hyperthermia system based on a multi-antenna array. By independently controlling the phase and amplitude of each antenna, it achieves energy focusing in the tumor area, while utilizing "cold zones" in different modes to counteract "hot spots" generated by other modes, improving heating uniformity and safety. However, it relies on a complex multi-antenna array and precise phase control, making hardware implementation and clinical operation challenging.

[0007] To address various needs, composite solutions combining different materials have emerged in existing technologies. For example, patent document CN102784436B describes a scheme involving mounting a metamaterial panel on a radiator body. This panel uses a designed refractive index distribution to focus electromagnetic waves, attempting to concentrate microwave energy at the lesion site. However, when this structure is applied in clinical practice, its inherent drawbacks become apparent: the metamaterial panel relies on a complex array of microstructures to achieve refractive index control, resulting in complex and costly manufacturing processes, making large-scale adoption in medical devices difficult. Furthermore, a fixed refractive index distribution only provides static focusing and cannot be flexibly adjusted according to different patient tissue parameters and treatment depths, leading to insufficient adaptability. In addition, metal wires or thin-film microstructures are prone to oxidation, aging, and performance degradation under high temperature, humidity, or long-term use environments, resulting in a decrease in shielding and focusing effects. Although this patent improves energy focusing through metamaterial design, it still fails to solve key problems such as structural complexity, insufficient durability, and poor clinical adaptability.

[0008] Many existing microwave hyperthermia devices employ a fixed box-type structure, with components housed inside the box and the treatment head positioned essentially in a fixed position. While this type of structure can indeed output microwave energy for heating local tissues in clinical use, its inherent limitations become apparent when adjustments are needed for different patient positions or treatment areas: traditional box-type hyperthermia devices lack lifting and turning functions, resulting in inflexible adjustment of the treatment head's height and direction, inconvenience during use, and even affecting the accuracy and comfort of treatment. Patent document CN214074723U proposes a microwave hyperthermia device with adjustable installation position, achieving vertical and horizontal adjustment of the treatment head by incorporating an electric telescopic rod lifting mechanism and a motor reducer rotation mechanism on the base. Although this solution improves the convenience of position adjustment, it still suffers from structural complexity, increased cost, and insufficient safety protection measures, failing to fundamentally address the comprehensive requirements of flexibility, stability, and safety in the clinical application of microwave hyperthermia equipment. Patent document CN201710832827 proposes a wearable microwave hyperthermia system for breast cancer treatment. By arranging multiple microstrip patch antenna units within a hemispherical water bladder, combined with deionized water cooling and phase control, it achieves targeted heating of tumors at different locations in the breast while minimizing damage to normal tissue, allowing heat to migrate and distribute evenly across the breast surface. However, this patent has a relatively complex structure, with a fixed number and arrangement of antennas, making it difficult to flexibly adapt to different breast shapes and tumor depths in different patients; the water bladder cooling relies on an external circulation system, increasing the difficulty of use and maintenance.

[0009] In principle, these solutions all follow traditional design approaches, making only localized optimizations to existing structures or control methods. For example, they might improve antenna placement, add cooling media, adjust phase control, or change the form of the outer conductor opening to enhance heating uniformity or ease of operation. However, these improvements still fail to break through the limitations of the traditional paradigm and do not offer fundamental solutions to key challenges in clinical applications—such as deep focusing in complex tissue environments, dynamic adaptation to different patient anatomy, and long-term safety and reliability. Summary of the Invention

[0010] The purpose of this invention is to provide a low-radiation, highly directional antenna structure for microwave hyperthermia, which addresses the shortcomings of existing technologies and solves the problems mentioned in the background.

[0011] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A low-radiation, highly directional antenna structure for microwave hyperthermia is mounted on a microwave heating cavity and includes an antenna radiator, two grounded metal posts, a metal substrate, and a coaxial flexible tube. The metal substrate is sealed to one side of the microwave heating cavity. Two grounding metal pillars are located inside the microwave heating cavity. The grounding metal pillars are mounted on the metal substrate perpendicular to the metal substrate. The two grounding metal pillars are spaced apart and symmetrically arranged. The antenna radiator is parallel to the metal substrate and is located on the upper part of the grounding metal pillars. One end of the coaxial flexible tube is connected to the antenna radiator, and the other end passes through the metal substrate and is located outside the microwave heating cavity for connecting an external solid-state microwave source.

[0012] Furthermore, the antenna radiator is made of a highly conductive metal material, including but not limited to one of copper, aluminum, and stainless steel.

[0013] Furthermore, the quality factor of the antenna radiator ranges from 3 to 8.

[0014] Furthermore, the antenna radiator has a cuboid structure, and a U-shaped groove is provided through the antenna radiator.

[0015] Furthermore, the connection point between the coaxial flexible tube and the antenna radiator is the center position of the antenna radiator.

[0016] Furthermore, the antenna radiator and the grounded metal post together form a reflective surface structure, which is used to suppress sidelobe radiation and form a concentrated main lobe.

[0017] Furthermore, the antenna radiator can withstand an input power of 300W.

[0018] Furthermore, the outer layer of the coaxial hose is made of a bend-resistant and high-temperature-resistant insulating material, and the interface part has a quick-plug structure.

[0019] The present invention has at least the following advantages or beneficial effects: 1. The reflective surface structure formed by the elevated antenna radiator and the grounded metal column effectively suppresses sidelobe radiation (sidelobe energy is reduced by more than 50%) by controlling the current return path and electromagnetic field distribution, forming a concentrated main lobe, so that microwave energy can be accurately projected to the target tissue area, improving the depth and precision of treatment.

[0020] 2. The antenna radiator is made of highly conductive metal material. The low Q value broadband design enables the antenna to maintain stable matching in a wide frequency band. It can adapt to the equivalent load changes caused by different tissue locations and water content, solving the problem of poor load robustness of traditional antennas and improving clinical reproducibility.

[0021] 3. The all-metal structure design breaks through the power limitations of traditional antennas, and can withstand a maximum input power of 300W.

[0022] 4. The directional constraint structure and impedance matching design work together to reduce energy leakage in non-target areas, improve energy utilization by more than 30%, reduce the risk of environmental electromagnetic radiation, and reduce power waste.

[0023] 5. The flexible coaxial tube design overcomes the positioning limitations of fixed antennas. Microwave energy generated by the antenna is transmitted to specific areas via the coaxial tube, allowing the operator to directly align the tube end with the target tissue for targeted heating. This design avoids the positioning limitations of fixed antennas, making the device more flexible and easier to operate in clinical applications. The outer layer of the tube is made of bend-resistant and high-temperature-resistant insulating material, and the interface uses a standardized quick-connect structure, ensuring stable electromagnetic performance even during repeated movements and adjustments. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of a low-radiation, highly directional antenna structure for microwave hyperthermia provided by the present invention; Figure 2 A schematic diagram of a low-radiation, highly directional antenna structure for microwave hyperthermia installed on a microwave heating cavity, provided by the present invention. Figure 3 This is a schematic diagram of a low-radiation, highly directional antenna structure for microwave hyperthermia provided by the present invention, without the installation of a metal substrate. Figure 4 A simulation of the focusing effect of a low-radiation, highly directional antenna structure for microwave hyperthermia; Figure 5 This is a simulation focusing effect diagram of a low-radiation, high-directivity antenna structure for microwave hyperthermia. Figure 6 This is a simulation focusing effect diagram of a low-radiation, highly directional antenna structure used in microwave thermotherapy.

[0026] Icons: 1. Antenna radiator; 2. Grounding metal post; 3. Solid-state microwave source; 4. Coaxial flexible tube; 5. Metal substrate; 6. Microwave radiation area; 7. Chamber; 8. Microwave heating cavity; 9. Tank. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments 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, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] Please refer to Figures 1 to 3 As shown, a low-radiation, highly directional antenna structure for microwave hyperthermia is mounted on a microwave heating cavity 8, comprising an antenna radiator 1, two grounded metal posts 2, a coaxial flexible tube 4, and a metal substrate 5. The metal substrate 5 is sealed to one side of the microwave heating cavity 8. The two grounded metal posts 2 are located within the chamber 7 of the microwave heating cavity 8, mounted perpendicularly to the metal substrate 5. The two grounded metal posts 5 are spaced apart and symmetrically arranged. The antenna radiator 1 is parallel to the metal substrate 5 and positioned above the grounded metal posts 2. One end of the coaxial flexible tube 4 is connected to the antenna radiator 1, and the other end passes through the metal substrate 5 and is located outside the microwave heating cavity 8. A solid-state microwave source 3 is connected externally via a wire. The solid-state microwave source 3 is prior art, and its structure and principle are not described in detail here.

[0029] The antenna radiator 1, elevated by grounded metal pillars 2, together with the metal substrate 5 below and the grounded metal pillars 2 on both sides, forms a complete current loop. Microwave energy is delivered to the antenna radiator 1 through the coaxial flexible tube 4, forming a high-frequency current distribution on the surface of the antenna radiator 1. The metal substrate 5 below provides a large-area reference ground, while the grounded metal pillars 2 on both sides provide a clear and controllable return path for the current in space: the high-frequency current flows from the antenna radiator 1 to the grounded metal pillars 2, then through the grounded metal pillars 2 to the metal substrate 5, and finally back to the coaxial outer conductor. The current return path is no longer loose and diffuse, but is confined to a specific area, thereby reducing unnecessary electromagnetic leakage and stray radiation, and improving radiation efficiency and directivity.

[0030] Simultaneously, with the current path restricted, the distribution of the electromagnetic field is also correspondingly restricted. The electromagnetic field distribution is jointly regulated by the directional enhancement structure and the reflector constraint, enabling microwave energy to achieve concentrated radiation and directional coupling at microwave radiation region 6. The electric field is mainly concentrated in the gap region between the antenna radiator 1 and the metal substrate 5, while the magnetic field is distributed around the current path. The lateral field is reflected or cut off by the grounded metal pillar 2, making it difficult to diffuse disorderly to both sides.

[0031] Specifically, the antenna radiator 1 is made of a highly conductive metal material, including but not limited to copper, aluminum, and stainless steel. The antenna radiator 1 has a cuboid structure, and a U-shaped groove 9 is provided through it, symmetrically arranged along an axis parallel to the x-axis of the antenna radiator 1. Furthermore, the quality factor of the antenna radiator ranges from 3 to 8.

[0032] This invention employs an all-metal unibody design. Both the antenna radiator 1 and the feed structure are made of highly conductive metal, avoiding the risk of dielectric material breakdown under high power. The metal structure, through optimized current distribution and heat dissipation paths, ensures both electromagnetic performance and improved mechanical strength and durability. This design enables the antenna to withstand input power up to 300W, far exceeding the capacity of traditional radiators that can only withstand tens of watts, meeting the clinical needs for rapid heating and deep internal heating.

[0033] Two grounding metal posts 2 are respectively set at both ends of the antenna radiator 1 near the metal substrate 5, and are symmetrically arranged along the axis parallel to the x-axis of the antenna radiator 1, and also symmetrically arranged along the axis parallel to the y-axis of the antenna radiator 1.

[0034] The coaxial flexible tube 4 includes an inner conductor, an inner layer, an outer conductor, and an outer layer arranged coaxially from the inside out. One end of the coaxial flexible tube 4 located outside the microwave heating cavity 8 is connected to the solid-state microwave source 3 via a wire. The wire is connected to the coaxial flexible tube 4 via an existing quick-connect structure. The other end is fixedly connected to the center of the antenna radiator. The outer layer is made of a bend-resistant and high-temperature-resistant insulating material.

[0035] The microwave energy generated by the microwave source is first transmitted to the antenna feed end via a flexible coaxial hose, and then radiated to the target tissue by the antenna to achieve directional heating. The flexible coaxial hose eliminates the fixed connection between the antenna and the microwave source, allowing the operator to flexibly adjust the antenna position according to clinical needs. This avoids the positioning limitations of a fixed structure and significantly improves operational convenience and adaptability. The outer layer of the hose is made of bend-resistant and high-temperature-resistant insulating material, and the interface uses a standardized quick-plug structure, maintaining stable electromagnetic transmission performance during repeated movements and adjustments.

[0036] The directivity and energy transmission efficiency of the antenna of this invention were calculated and analyzed using electromagnetic field simulation software. The results show that within the target operating frequency band, the antenna VSWR is significantly reduced, and the energy utilization rate is increased by more than 30%; the main lobe concentration is enhanced, and the near-field temperature field distribution is more uniform; the antenna maintains a stable operating state under an input power of 300W; and the coaxial flexible tube transmission section maintains low loss and high reliability after multiple bends and positioning adjustments.

[0037] Please refer to Figures 4 to 6As shown in the simulation diagram, the antenna exhibits good directivity and focusing effect at different positions, making it suitable for microwave hyperthermia equipment to treat different areas.

[0038] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-radiation, highly directional antenna structure for microwave hyperthermia, mounted on a microwave heating cavity, characterized in that, It includes an antenna radiator, two grounded metal posts, a metal substrate, and a coaxial flexible tube; The metal substrate is sealed to one side of the microwave heating cavity. Two grounding metal pillars are located inside the microwave heating cavity. The grounding metal pillars are mounted on the metal substrate perpendicular to the metal substrate. The two grounding metal pillars are spaced apart and symmetrically arranged. The antenna radiator is parallel to the metal substrate and is located on the upper part of the grounding metal pillars. One end of the coaxial flexible tube is connected to the antenna radiator, and the other end passes through the metal substrate and is located outside the microwave heating cavity for connecting an external solid-state microwave source.

2. The low-radiation, high-directivity antenna structure for microwave hyperthermia according to claim 1, characterized in that, The antenna radiator is made of a highly conductive metal material, including but not limited to copper, aluminum, and stainless steel.

3. The low-radiation, high-directivity antenna structure for microwave hyperthermia according to claim 1, characterized in that, The quality factor of the antenna radiator ranges from 3 to 8.

4. The low-radiation, high-directivity antenna structure for microwave hyperthermia according to claim 1, characterized in that, The antenna radiator has a cuboid structure, and a U-shaped groove is installed through the antenna radiator.

5. A low-radiation, highly directional antenna structure for microwave hyperthermia according to claim 1, characterized in that, The connection point between the coaxial flexible tube and the antenna radiator is the center of the antenna radiator.

6. A low-radiation, highly directional antenna structure for microwave hyperthermia according to claim 1, characterized in that, The antenna radiator and the grounded metal post together form a reflector structure, which is used to suppress sidelobe radiation and form a concentrated main lobe.

7. A low-radiation, highly directional antenna structure for microwave hyperthermia according to claim 1, characterized in that, The antenna radiator can withstand an input power of 300W.

8. A low-radiation, highly directional antenna structure for microwave hyperthermia according to claim 1, characterized in that, The outer layer of the coaxial flexible hose is made of a bend-resistant and high-temperature-resistant insulating material, and the interface is a quick-plug structure.

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