A method for manufacturing a microwave ablation antenna with a sharp tip and the microwave ablation antenna

Abstract

The application discloses a microwave ablation antenna with a pointed radiation head and a manufacturing method thereof. The manufacturing method comprises the following steps: establishing a microwave energy transmission path, penetrating a radio frequency cable through a handle, an antenna main body tube, a dielectric sleeve and a radiation head, establishing a cooling water circulation path, and establishing an antenna main body tube temperature measurement signal path. The microwave ablation antenna comprises a radiation head, a dielectric sleeve, a radio frequency cable, an antenna main body tube, a handle, a water supply pipe and a temperature measuring element. The application is based on the dipole antenna theory, and the optimal matching size parameters of the three-pronged radiation head, the dielectric sleeve, the electrically conductive filling medium and the radio frequency cable are obtained through finite element calculation, so that the effect of the microwave energy radiated by the pointed end of the radiation head is achieved.

Description

Technical Field

[0001] This invention relates to a minimally invasive treatment device, namely, a method for manufacturing a microwave ablation antenna with pointed radiation and the microwave ablation antenna thereof. Background Technology

[0002] Microwave ablation antennas are inserted into tumor tissue under the guidance of medical images such as ultrasound and CT, with ultrasound guidance being particularly common. The imaging effect of the radiated needle under ultrasound directly determines whether the ablation antenna can accurately hit the target tissue, and indirectly determines the efficacy and success of the ablation procedure. Currently, the commonly used imaging enhancement method is to increase the roughness of the ablation antenna tip, thereby increasing the diffuse reflection of ultrasound waves at the antenna tip to achieve the purpose of imaging enhancement. However, this improvement is very limited, and for ultrasound equipment with slightly lower resolution, this method is still insufficient to solve the imaging problem.

[0003] After the microwave ablation antenna is inserted into the target tissue, the instant the microwave equipment is turned on, the tissue at the center of microwave radiation will instantly heat up to over 100°C due to the high thermal efficiency of microwave energy. This instantaneous temperature gradient is sufficient to cause the water in the target tissue to vaporize instantly, generating steam, which appears as a hazy image under ultrasound imaging. Figure 11 Based on this phenomenon, if the thermal radiation point of the ablation antenna can be designed to be at the tip of the antenna, the vaporization position is the needle tip position, and the needle tip position can be easily located, avoiding abnormal damage caused by the inability to determine the needle tip position.

[0004] In addition, clinical cases frequently report expansion problems caused by poor temperature tolerance of the dielectric sheath at the tip of microwave antennas, leading to medical accidents.

[0005] The applicant's patent application, application number CN202110501294.6, publication number CN113576657A, discloses a medical ablation antenna, comprising a radiating antenna and a handle. It includes a microwave composite radiating head, a dielectric ring, a radiating antenna body, a water cavity box, an RF connector, and a temperature sensor. An embedded heating conductor is fitted within a puncture radiation sleeve to form the microwave composite radiating head, and the dielectric ring is positioned between the microwave composite radiating head and the radiating antenna body. The radiating antenna body is a structural tube containing a water supply pipe and a microwave transmission cable. An inlet and outlet connector are fixed to the water cavity box, and a water circulation channel is formed by the inlet connector, the inlet cavity, the gap between the water supply pipe and the microwave transmission cable, the gap between the water supply pipe and the structural tube of the radiating antenna body, the outlet cavity, and the outlet connector. The RF connector, microwave transmission cable, and microwave composite radiating head are electrically connected.

[0006] The applicant's patent application number is CN202120614401.1, and the authorized publication number is CN215018040U. It discloses a puncture needle comprising a puncture portion and a mounting and fixing portion. The puncture portion includes two bevels and a main beveled edge, with the needle tip offset from the needle axis. This utility model provides a puncture needle structure that allows for direct puncture without breaking the skin, significantly reducing puncture resistance, avoiding preoperative skin abrasion, and shortening surgical time.

[0007] This application is an improvement on the microwave ablation antenna based on the prior art. Summary of the Invention

[0008] The technical solution provided by this invention:

[0009] A method for fabricating a microwave ablation antenna with pointed radiation, comprising the following steps:

[0010] Step 1: Microwave energy transmission path:

[0011] The radio frequency cable passes through the handle, the antenna main tube 5, the dielectric sleeve 2, and the radiator head 1. The internal hole of the stepped post at the tail end of the radiator head 1 is connected to the inner conductor 803 of the radio frequency cable. The dielectric sleeve 2 is a cylindrical structure located between the radiator head 1 and the far end of the antenna main tube 5. The near end of the antenna main tube 5 is fixed to the handle, and the radio frequency cable is led out through the handle to connect to an external microwave power source.

[0012] Step 2: Cooling water circulation path:

[0013] The antenna main tube 5 contains a water supply pipe 7 that is fitted outside the radio frequency cable. The water inlet pipe at the handle is connected to the water inlet channel in the gap between the radio frequency cable and the water supply pipe 7. The water inlet channel turns back at the far end of the water supply pipe 7 to the water outlet channel formed by the gap between the water supply pipe 7 and the antenna main tube 5, and then leads out through the water outlet pipe in the handle, forming a cooling water circulation path.

[0014] Step 3: Temperature measurement signal path for antenna main tube 5:

[0015] The temperature sensing element 6 is located at the far end of the water supply pipe 7, inside the antenna main tube 5. The signal transmission line of the temperature sensing element 6 is led out from the handle through the antenna main tube 5 to connect to the external temperature measurement and processing circuit.

[0016] In the first step of the microwave energy transmission path:

[0017] The radiator head 1 is triangular in shape: the tip is a triangular structure, and the tail end is a stepped column. It is made of a material with good electrical conductivity, such as copper or stainless steel. The exposed part of the radiator head 1 has a length L1, and the tail end stepped column has a length L12, which satisfies the following condition: L1 + L12 = λ / 4, where λ is the wavelength corresponding to the microwave power source frequency.

[0018] The dielectric sleeve 2 is fitted onto the tail-end stepped post of the triangular radiator 1 and the outer conductor 801 of the radio frequency cable. The outer diameter OD21 of the large circular section of the dielectric sleeve 2 matches the outer diameter OD1 of the radiator 1. The far end of the antenna body tube 5 is fitted onto the small circular section of the dielectric sleeve 2. The outer diameter OD of the antenna body tube 5 matches the outer diameter OD21 of the large circular section of the dielectric sleeve 2. The gap between the inner wall of the dielectric sleeve 2 and the contact surface between the tail-end stepped post of the triangular radiator 1 and the outer conductor 801 of the radio frequency cable is no greater than 0.1 mm. The dielectric is filled with a dielectric with a dielectric constant εr2 of not less than 3. The filling dielectric 4 can withstand a temperature greater than 250℃.

[0019] When the dielectric constant εr1 of dielectric sleeve 2 is greater than 15, the lengths L2 of the large circular segment and L22 of the small circular segment of dielectric sleeve 2 satisfy: L2 + L22 = λ, where λ is the wavelength corresponding to the microwave power source frequency.

[0020] RF cables meet the following requirements: Where: Z0 is the characteristic impedance of the RF cable, OD82 is the inner diameter of the outer conductor 801 and the outer diameter of the dielectric layer 802 of the RF cable, OD81 is the outer diameter of the inner conductor 803 of the RF cable, and ε is the dielectric constant of the dielectric layer 802 of the RF cable.

[0021] When the antenna radiation frequency is 2450MHz, the exposed part of the triangular radiator 1 has a length of L1 = 1-4mm, an angle of θ = 30-50°, an outer diameter of OD1 = 1.2-2.1mm, a tail-end stepped column with a length of L12 = 1-4mm, an outer diameter of OD12 = 0.6-1.1mm, and an internal aperture of OD13 = 0.12-0.34mm.

[0022] The length of the large circular segment of dielectric sleeve 2 is L2 = 6-8mm, the length of the small circular segment of dielectric sleeve 2 is L22 = 6-8mm, the outer diameter of the large circular segment of dielectric sleeve 2 is OD21 = 1.2-2.1mm, the outer diameter of the small circular segment of dielectric sleeve 2 is OD22 = 1.1-1.9mm, and the inner diameter of dielectric sleeve 2 is OD23, which is 0.6-1.1mm based on the outer diameter of the 801 outer conductor of the coaxial cable.

[0023] When the characteristic impedance of the RF cable is 50Ω, the outer diameter OD81 of the inner conductor 803 is 0.12-0.34mm, and the inner diameter of the outer conductor 801 and the outer diameter of the dielectric layer 802 are OD82, which are 0.4-0.9mm. Typically, the outer diameter OD83 of the outer conductor 801 of the RF cable is 0.6-1.1mm. The exposed length L81 of the inner conductor 803 and the exposed length L82 of the dielectric layer 802 affect the radiation efficiency and the location of the radiant thermal field. This invention verifies that L81 = 3-5mm and L82 = 0.5-2mm.

[0024] The outer diameter OD of the antenna main tube 5 is 1.2-2.1mm. The gap between the antenna main tube 5 and the small circular segment of the dielectric sleeve 2 is filled with a conductive medium 3, such as solder. The thickness of the conductive medium 3 layer is 0.05-0.1mm, which serves to seal the gap between the dielectric sleeve 2 and the antenna main tube 5.

[0025] A microwave ablation antenna with pointed radiation includes: a radiating head 1, a dielectric sleeve 2, a radio frequency cable, an antenna body tube 5, a handle, a water supply pipe 7, and a temperature measuring element 6.

[0026] The radio frequency cable passes through the handle, the antenna main tube 5, the dielectric sleeve 2, and the radiator head 1. The internal hole at the tail end of the radiator head 1 is connected to the inner conductor 803 of the radio frequency cable. The dielectric sleeve 2 is a cylindrical structure located between the radiator head 1 and the far end of the antenna main tube 5. The near end of the antenna main tube 5 is fixed to the handle, and the radio frequency cable is led out through the handle to connect to an external microwave power source.

[0027] The antenna main tube 5 contains a water supply pipe 7 that is fitted outside the radio frequency cable. The water inlet pipe at the handle is connected to the water inlet channel in the gap between the radio frequency cable and the water supply pipe 7. The water inlet channel turns back at the far end of the water supply pipe 7 to the water outlet channel formed by the gap between the water supply pipe 7 and the antenna main tube 5, and then leads out through the water outlet pipe in the handle, forming a cooling water circulation path.

[0028] The temperature sensing element 6 is located at the far end of the water supply pipe 7, inside the antenna main tube 5. The signal transmission line of the temperature sensing element 6 is led out from the handle through the antenna main tube 5 to connect to the external temperature measurement and processing circuit.

[0029] The dielectric sleeve 2 is fitted onto the stepped post at the tail end of the triangular radiator 1 and the outer conductor 801 of the radio frequency cable. The outer diameter OD21 of the large circular section of the dielectric sleeve 2 matches the outer diameter OD1 of the radiator 1. The far end of the antenna body tube 5 is fitted onto the small circular section of the dielectric sleeve 2. The outer diameter OD of the antenna body tube 5 matches the outer diameter OD21 of the large circular section of the dielectric sleeve 2. The gap between the inner wall of the dielectric sleeve 2 and the contact surface between the triangular radiator 1 and the outer conductor 801 of the radio frequency cable is no greater than 0.1 mm. It is filled with a dielectric with a dielectric constant εr2 of not less than 3. The filling dielectric 4 can withstand a temperature greater than 250℃.

[0030] When the antenna radiation frequency is 2450MHz, the exposed part of the triangular radiator 1 has a length of L1 = 1-4mm, an angle of θ = 30-50°, an outer diameter of OD1 = 1.2-2.1mm, a step column length of L12 = 1-4mm, an outer diameter of OD12 = 0.6-1.1mm, and an internal aperture of OD13 = 0.12-0.34mm.

[0031] When the antenna radiation frequency is 2450MHz, the length of the large circular segment L2 of dielectric sleeve 2 is 6-8mm, the length of the small circular segment L22 of dielectric sleeve 2 is 6-8mm, the outer diameter of the large circular segment OD21 of dielectric sleeve 2 is 1.2-2.1mm, the outer diameter of the small circular segment OD22 of dielectric sleeve 2 is 1.1-1.9mm, and the inner diameter OD23 of dielectric sleeve 2 is 0.6-1.1mm based on the outer diameter of the 801 outer conductor of the RF cable.

[0032] When the antenna radiation frequency is 2450MHz, and the characteristic impedance of the RF cable is 50Ω, the outer diameter of the inner conductor 803 (OD81) is 0.12-0.34mm, and the inner diameter of the outer conductor 801 and the outer diameter of the dielectric layer 802 (OD82) are 0.4-0.9mm. Typically, the outer diameter of the outer conductor 801 (OD83) of the RF cable is 0.6-1.1mm. The exposed length L81 of the inner conductor 803 and the exposed length L82 of the dielectric layer 802 affect the radiation efficiency and the location of the radiation thermal field. This invention verifies that L81 = 3-5mm and L82 = 0.5-2mm.

[0033] When the antenna radiation frequency is 2450MHz, the outer diameter OD of the antenna main tube 5 is 1.2-2.1mm. The gap between the antenna main tube 5 and the small circular segment of the dielectric sleeve 2 is filled with conductive medium 3, such as solder. The thickness of the conductive medium 3 layer is 0.05-0.1mm, which plays a sealing role in the gap between the dielectric sleeve 2 and the antenna main tube 5.

[0034] In light of the clinical surgical risks associated with microwave ablation procedures, such as the difficulty in determining the relative position of the microwave radiation needle to the target tissue and the tendency for the dielectric sheath to expand, the present invention offers the following advantages:

[0035] 1. Based on the theory of dipole antennas, a variant dipole antenna consisting of a triangular radiating head 1 and a filling medium was designed. The conductive medium 3 is used as one of the dipole elements. While simplifying the joint, the dielectric sleeve 2 and the antenna body tube 5 can be directly sealed, achieving multiple benefits.

[0036] 2. Needle positioning has always been a challenge for clinicians during ablation surgery. This invention is based on dipole antenna theory and uses finite element software to calculate the optimal fit dimensions of the triangular radiating head 1, dielectric sleeve 2, conductive filling dielectric 3, and radio frequency cable, and provides the range of dimension fluctuation.

[0037] 3. By moving the microwave radiation heat of the microwave ablation antenna forward to the antenna tip and moving the point of maximum temperature density away from the dielectric sleeve 2, the problem of thermal expansion of the dielectric sleeve 2 during the operation is fundamentally solved, improving the safety of the operation and avoiding medical accidents.

[0038] The advanced medical microwave ablation antenna provided by this invention has been specifically designed to significantly improve surgical efficacy and safety.

[0039] Adjusting the position of the microwave thermal field radiation to the tip of the microwave antenna will reduce the temperature density at the dielectric sleeve 2 position, thus reducing the risk of thermal failure. When inserting the ablation antenna into the tumor tissue, simply insert the tip of the ablation antenna into the center of the target tissue sphere.

[0040] Obviously, the microwave antenna provided by this invention has a more accurate antenna needle positioning effect, an extremely low risk of dielectric sheath expansion, and a significant improvement in surgical safety. Attached Figure Description

[0041] Figure 1 This is a waveform diagram of the voltage and current on the dipole antenna element of the present invention;

[0042] Figure 2 This is a schematic diagram of a variant of the dipole antenna of the present invention;

[0043] Figure 3 This is a front view of the microwave ablation antenna with tip radiation according to the present invention;

[0044] Figure 4 This is a cross-sectional view of the tip of the microwave ablation antenna of the present invention.

[0045] Figure 5 The triangular radiating head 1 of the present invention;

[0046] Figure 6 The medium sleeve 2 of this invention;

[0047] Figure 7 This is a cross-sectional view of the far end of the radio frequency cable of the present invention;

[0048] Figure 8 This is a cross-sectional view of the antenna body tube 5 of the present invention;

[0049] Figure 9 This is a finite element simulation of the radiation thermal field cloud diagram of the present invention;

[0050] Figure 10 These are experimental photos comparing the radiated thermal fields of a conventional microwave antenna and the microwave antenna of this invention.

[0051] Figure 11 This is a diagram of a live ablation experiment using the microwave ablation antenna with its tip radiation, as described in this invention.

[0052] Figure 12 This invention illustrates the effect of the exposed length L1 of the radiator head on the position of the radiating point.

[0053] Figure 13 This invention illustrates the influence of the length L12 of the stepped column at the end of the radiating head on the position of the radiating point.

[0054] Figure 14 This invention illustrates the influence of the length L22 of the small circular segment of the dielectric sleeve on the position of the radiation point.

[0055] Figure 15 This invention illustrates the effect of the length L2 of the large circular segment of the dielectric sleeve on the position of the radiation point.

[0056] Figure 16 This invention illustrates the effect of the dielectric constant εr1 of the dielectric sleeve on the position of the radiation point.

[0057] Figure 17 This invention illustrates the effect of the dielectric constant εr2 of the filling medium on the location of the radiation point.

[0058] Among them: 1. Triangular radiating head; 2. Dielectric sleeve; 3. Conductive dielectric; 4. Filling dielectric; 5. Antenna main tube; 6. Temperature measuring element; 7. Water supply pipe; 801. Outer conductor of RF cable; 802. Dielectric layer of RF cable; 803. Inner conductor of RF cable. Detailed Implementation

[0059] The invention will now be further described with reference to the accompanying drawings.

[0060] Currently, the most commonly used microwave ablation antennas in clinical practice are coaxial-fed dipole microwave antennas, or monopole microwave antennas, a variant of dipole antennas. Image theory can be used to effectively analyze and design antennas from dipoles to monopoles. For a typical monopole antenna, the radiation resistance and power can be approximated as half that of a dipole antenna, and the directivity is approximately twice that of a dipole antenna, i.e.:

[0061]

[0062] Where: D is the power directivity coefficient, D dipole Corresponding to the dipole, D mono Corresponding monopole; Ω A For radiation resistance, Ω A,mono Corresponding to a monopole, Ω A,dipole Corresponding to a dipole.

[0063] Figure 1 The graphs show the voltage and current variations of a dipole antenna. Based on these relationships: the total length of the dipole is half a wavelength; the maximum voltage (+2Umax) is within the half-wavelength range; and the current is in the same direction within the half-wavelength range. If, based on dipole antenna theory, the total length of the dipole antenna is designed to be half a wavelength (λ / 2), then the radiated power can be maximized. Therefore, by rationally designing the dipole structure, such as... Figure 2In particular, La and Lb are the two poles of the dipole antenna of this invention. As mentioned above, when La + Lb = λ / 2, the radiation efficiency in the medium can be maximized. Typically, the finite element method (FEM) is used to establish a thermal field radiation model of the microwave ablation antenna and optimize the size distribution ratio of La and Lb so that La + Lb = λ / 2 (calculated using the formula below, where λ is the radiation wavelength of the electromagnetic wave in the tumor tissue). This allows the microwave to radiate with the highest efficiency in the tumor tissue while shifting the center of the thermal field forward to the tip.

[0064] Figure 2 This invention is a variant based on dipole antenna theory. According to dipole theory, maximizing radiated power can be achieved when the total antenna length is λ / 2. In the formula, n is the refractive index of the medium, λ0 is the vacuum wavelength, c = 3 × 10⁸ m / s, v = 2450 × 10⁹ Hz, εr' = 62.44, and then the wavelength λ of 2.45 GHz electromagnetic waves in human (liver) tumor tissue is calculated.

[0065] To design an antenna structure that optimizes both the radiated thermal field at the antenna tip and the radiation efficiency, finite element analysis software is required to determine the optimal structure, materials, and dimensions. The tip-radiating medical microwave antenna provided by this invention mainly consists of a triangular radiating electrode, a dielectric sheath, an RF cable, another radiating electrode composed of a conductive dielectric, an antenna body tube, a water supply pipe, and a temperature sensing element. The analyzed structural and material properties and related data will be described in detail below.

[0066] Depend on Figure 4 , Figure 5 As shown, the advanced radiation medical microwave ablation antenna provided by the present invention mainly consists of a triangular radiating head 1, a dielectric sleeve 2, radio frequency cables (801-803), another radiating pole composed of a conductive dielectric 3, an antenna body 5, a water supply pipe 6, and a temperature measuring element 7.

[0067] The triangular radiating head 1 is one pole of the pointed radiating antenna provided by this invention. The tip has a triangular structure, and the tail end is a stepped post connector. It is made of a material with good electrical conductivity, such as copper or stainless steel. According to... Figure 12 The finite element simulation analysis shown has an exposed portion length of L1 = 1-4 mm, an angle θ = 30-50°, an outer diameter OD1 = 1.2-2.1 mm, and the length of the tail-end stepped column L12+L1 affects the microwave radiation efficiency, which should ideally be λ / 4. Figure 13 The finite element simulation analysis shown has a tail-end stepped column length of L12 = 1-4 mm, an outer diameter of OD12 = 0.6-1.1 mm, and an internal hole diameter of OD13 = 0.12-0.34 mm.

[0068] The dielectric sleeve 2 is fitted onto the stepped post of the triangular radiator 1, serving as the isolation medium between one pole and the other pole of the dipole antenna triangular radiator. It is made of a high dielectric constant material, as confirmed by finite element analysis. Figure 16 When εr1 > 15, the microwave ablation morphology is approximately circular, with high radiation efficiency. The larger the dielectric constant, the closer the morphology is to a circle, and the microwave radiation point is located at the tip. The dielectric sleeve 2 is a cylindrical structure with an internally continuous structure; the outer cylindrical surface includes a large circular segment and a small circular segment. Based on finite element simulation analysis (… Figure 15 When L2 = 6-8 mm, an approximately circular shape can be obtained, with the microwave radiation point located at the tip; simultaneously, according to finite element simulation analysis ( Figure 14 The length of L22 needs to be adjusted to satisfy L22 + L2 = λ. If the antenna radiation frequency is 2450MHz, then L22 + L2 = 12.2mm. At this time, the microwave radiation point is located at the tip and is close to a perfect circle. The outer diameter of the large circular segment OD21 = 1.2-2.1mm, the outer diameter of the small circular segment OD22 = 1.1-1.9mm, and the inner diameter OD23 is designed based on the outer diameter of the 801 outer conductor of the RF cable, and is usually designed to be 0.6-1.1mm.

[0069] Radio frequency (RF) cables (801-803) consist of three parts: an outer conductor, a dielectric layer, and an inner conductor. For clinical microwave ablation, a characteristic impedance of 50Ω is commonly used at 2.45GHz. The outer diameter of the inner conductor (OD81) is 0.12-0.34mm, and the inner diameter of the outer conductor and the outer diameter of the dielectric layer (OD82) are commonly... The outer diameter of the outer conductor is typically 0.6-1.1 mm. The exposed length of the inner conductor L81 and the exposed length of the dielectric layer L82 affect the radiation efficiency and the location of the radiative thermal field. This invention verifies that L81 = 3-5 mm and L82 = 0.5-2 mm.

[0070] The dielectric sleeve 2 is fitted onto the triangular radiating head and the radio frequency cable (801-803). The fit gap affects the performance of the medical microwave antenna of this invention. All fit gaps should not exceed 0.1mm. Furthermore, based on finite element analysis... Figure 17 The gap between the three components is filled with a dielectric material with a dielectric constant εr2 of not less than 3, which should be able to withstand high temperatures above 250°C.

[0071] The antenna main tube 5 is the structural tube that carries the radiator head 1. It should have good bending strength, an outer diameter OD of 1.2-2.1 mm, and a wall thickness of no more than 0.1 mm. It is fitted onto the small circular segment of the dielectric sleeve 2. To form the other pole of the dipole antenna, a conductive medium, such as solder, is filled between the antenna main tube 5 and the small circular segment of the dielectric sleeve 2. This medium makes electrical contact with the outer conductor of the RF cable to form the other pole of the dipole antenna. Crucially, this dielectric layer has a wall thickness of 0.05-0.1 mm, serving both to support the antenna array and to seal the gap between the dielectric sleeve and the antenna main tube.

[0072] Temperature sensing element 6: During microwave ablation surgery, the temperature of the microwave antenna body is monitored to prevent the body 5 from burning the patient's skin. Therefore, a temperature sensing element 6 is designed on the small circular end face of the dielectric sleeve 2. The temperature sensing element 6 is required to have a temperature measurement range of not less than 100°C. It adopts thermocouple, thermistor or fiber optic temperature sensing element and is fixed to the inner wall of the antenna body tube 5 near the dielectric sleeve 2 by adhesive bonding.

[0073] Water supply pipe 7 is fitted onto RF cables 801-803, with its front end face close to the small round end face of dielectric sleeve 2, approximately 2mm apart. The gap between water supply pipe 7 and RF cables 801-803 forms an inlet channel, while the gap between water supply pipe 7 and the inner wall of antenna main tube 5 forms an outlet channel. Water supply pipe 7 has a wall thickness of 0.5mm, and its inner and outer diameters are designed to... Figure 9 The cross-sectional area S2 of the inlet chamber and the cross-sectional area S1 of the outlet chamber are the same.

[0074] Figure 10 The left image shows the microwave thermal field radiation position of currently available medical microwave ablation antennas. This position is located near the center of the dielectric sheath. The microwave thermal field is located at this position, and the center of the dielectric sheath is at the highest point of the temperature field. Obviously, this increases the risk of thermal expansion. Simultaneously, there is a certain length of unknown ineffective region between the microwave thermal field and the needle tip. During surgery, the radiated needle needs to pass through the center of the tumor tissue to ensure that the microwave thermal field matches the center of the tumor, in order to achieve the best therapeutic effect.

Claims

1. A microwave ablation antenna with tip radiation, comprising the following steps: Step 1: Microwave energy transmission path: A radio frequency cable passes through a handle, an antenna main tube (5), a dielectric sleeve (2) and a radiation head (1); the inner hole of the tail end step column of the radiation head (1) is connected with the inner conductor (803) of the radio frequency cable; the dielectric sleeve (2) is in a cylindrical structure, which is located between the radiation head (1) and the distal end of the antenna main tube (5); the proximal end of the antenna main tube (5) is fixed to the handle, and the radio frequency cable is led out of the handle to be connected with a microwave power source; Step 2: Cooling water circulation path: There is a water supply pipe (7) in the antenna main tube (5) which is sleeved on the radio frequency cable; the water inlet pipe at the handle is connected with the water inlet cavity between the radio frequency cable and the water supply pipe (7); the water inlet cavity is folded back to the water outlet cavity formed by the gap between the water supply pipe (7) and the antenna main tube (5) at the distal end of the water supply pipe (7), and then led out through the water outlet pipe in the handle to form a cooling water circulation path; Step 3: Antenna main tube (5) temperature measurement signal path: The temperature measuring element (6) is located at the distal end of the water supply pipe (7) in the antenna main tube (5); the signal transmission line of the temperature measuring element (6) is led out of the handle through the antenna main tube (5) to be connected with a temperature measurement processing circuit; The features in the first step microwave energy transmission path are: The radiation head (1) is in a three-pronged shape, the tip is in a three-pronged structure, and the tail end is in a step column; the length L1 of the exposed part of the radiation head (1) and the length L12 of the tail end step column satisfy: L1+L12=λ / 4, wherein λ is the wavelength corresponding to the frequency of the microwave power source; The dielectric sleeve (2) is sleeved on the tail end step column of the three-pronged radiation head (1) and the outer conductor (801) of the radio frequency cable; the large circular segment outer diameter OD21 of the dielectric sleeve (2) is consistent with the outer diameter OD1 of the radiation head (1); the antenna main tube (5) is sleeved on the small circular segment of the dielectric sleeve (2); the outer diameter OD of the antenna main tube (5) is consistent with the large circular segment outer diameter OD21 of the dielectric sleeve (2); the cooperation gap between the inner wall of the dielectric sleeve (2) and the contact surface of the tail end step column of the three-pronged radiation head (1) and the outer conductor (801) of the radio frequency cable is not greater than 0.1 mm; a dielectric with a dielectric constant εr2 not less than 3 is filled, and the dielectric with a dielectric constant εr2 not less than 3 can resist a temperature greater than 250℃; When the dielectric constant εr1 of the dielectric sleeve (2) is greater than 15, the length L2 of the large circular segment of the dielectric sleeve (2) and the length L22 of the small circular segment satisfy: L2+L22=λ, wherein λ is the wavelength corresponding to the frequency of the microwave power source; The radio frequency cable satisfies: wherein: Z0 is the characteristic impedance of the radio frequency cable, OD82 is the inner diameter of the outer conductor (801) and the outer diameter of the dielectric layer (802) of the radio frequency cable, OD81 is the outer diameter of the inner conductor (803) of the radio frequency cable, and ε is the dielectric constant of the dielectric layer (802) of the radio frequency cable.

2. The microwave ablation antenna with tip radiation according to claim 1, wherein: when the antenna radiation frequency is 2450 MHz, the length of the exposed part of the three-pronged radiation head (1) is L1=1-4 mm, the prong angle θ is 30-50°, and the outer diameter OD1 is 1.2-2.1 mm; the length of the tail end step column is L12=1-4 mm, the outer diameter OD12 is 0.6-1.1 mm, and the inner hole diameter OD13 of the tail end step column is 0.12-0.34 mm. The medium sleeve (2) has a large circular segment with a length L2 of 6-8 mm, a small circular segment with a length L22 of 6-8 mm, an outer diameter OD21 of 1.2-2.1 mm, an outer diameter OD22 of 1.1-1.9 mm, and an inner diameter OD23 of 0.6-1.1 mm, which is designed based on the outer diameter of the outer conductor (801) of the radio frequency cable; When the characteristic impedance of the radio frequency cable is 50 Ω, the outer diameter OD81 of the inner conductor (803) is 0.12-0.34 mm, the inner diameter of the outer conductor (801) and the outer diameter of the medium layer (802) OD82 are 0.4-0.9 mm, and the outer diameter OD83 of the outer conductor (801) of the radio frequency cable is 0.6-1.1 mm; the exposed length L81 of the inner conductor (803) is 3-5 mm, and the exposed length L82 of the medium layer (802) is 0.5-2 mm; The antenna main tube (5) has an outer diameter OD of 1.2-2.1 mm, and the gap between the antenna main tube (5) and the small circular segment of the medium sleeve (2) is filled with conductive medium (3) soldering tin with a thickness of 0.05-0.1 mm, which plays a sealing role between the medium sleeve (2) and the antenna main tube (5).

3. A microwave ablation antenna with a sharp tip, comprising a radiation head (1), a medium sleeve (2), a radio frequency cable, an antenna main tube (5), a handle, a water supply pipe (7), and a temperature measuring element (6); The radio frequency cable passes through the handle, the antenna main tube (5), the medium sleeve (2), and the radiation head (1); the inner hole of the tail end step column of the radiation head (1) is connected with the inner conductor (803) of the radio frequency cable, the medium sleeve (2) has a cylindrical structure and is located between the radiation head (1) and the distal end of the antenna main tube (5); the proximal end of the antenna main tube (5) is fixed to the handle, and the radio frequency cable is led out of the handle to be connected with a microwave power source; The antenna main tube (5) has a water supply pipe (7) sleeved outside the radio frequency cable, a water inlet cavity is formed between the radio frequency cable and the water supply pipe (7), and the water inlet cavity is connected to a water outlet cavity formed between the water supply pipe (7) and the antenna main tube (5) through a water inlet pipe in the handle, and then the water outlet cavity is connected to a water outlet pipe in the handle to form a cooling water circulation passage; The temperature measuring element (6) is located at the distal end of the water supply pipe (7) in the antenna main tube (5), and the signal transmission line of the temperature measuring element (6) is led out of the handle through the antenna main tube (5) to be connected with a temperature measurement processing circuit; The radiation head (1) is in a triangular shape, and the sum of the length L1 of the exposed part and the length L12 of the tail end step column is one fourth of the wavelength corresponding to the frequency of the microwave power source. ​ The medium sleeve (2) is sleeved on the tail end step column of the three-prong radiation head (1) and the outer conductor (801) of the radio frequency cable, the outer diameter OD21 of the large circular segment of the medium sleeve (2) is consistent with the outer diameter OD1 of the radiation head (1); the antenna main body tube (5) is sleeved on the small circular segment of the medium sleeve (2), the outer diameter OD of the antenna main body tube (5) is consistent with the outer diameter OD21 of the large circular segment of the medium sleeve (2); the cooperation gap between the inner wall of the medium sleeve (2) and the contact surface of the three-prong radiation head (1) and the outer conductor (801) of the radio frequency cable is not greater than 0.1 mm, the medium with a dielectric constant εr2 not less than 3 is filled, and the medium with the dielectric constant εr2 not less than 3 can resist a temperature greater than 250 DEG C.

4. The microwave ablation antenna with a tip radiation according to claim 3, characterized in that: when the antenna radiation frequency is 2450 MHz, the exposed part of the three-prong radiation head (1) has a length L1 = 1-4 mm, an angle θ = 30-50°, and an outer diameter OD1 = 1.2-2.1 mm, the tail end step column has a length L12 = 1-4 mm, an outer diameter OD12 = 0.6-1.1 mm, and an inner hole diameter OD13 = 0.12-0.34 mm.

5. The microwave ablation antenna with a tip radiation according to claim 4, characterized in that: when the antenna radiation frequency is 2450 MHz, the large circular segment of the medium sleeve (2) has a length L2 = 6-8 mm, the small circular segment of the medium sleeve (2) has a length L22 = 6-8 mm, the outer diameter OD21 of the large circular segment of the medium sleeve (2) is 1.2-2.1 mm, the outer diameter OD22 of the small circular segment of the medium sleeve (2) is 1.1-1.9 mm, and the inner diameter OD23 of the medium sleeve (2) is 0.6-1.1 mm based on the outer diameter of the outer conductor (801) of the radio frequency cable.

6. The microwave ablation antenna with a tip radiation according to claim 5, characterized in that: when the antenna radiation frequency is 2450 MHz, the radio frequency cable has a characteristic impedance of 50 Ω, the outer diameter OD81 of the inner conductor (803) is 0.12-0.34 mm, the inner diameter of the outer conductor (801) and the outer diameter of the dielectric layer (802) are OD82 = 0.4-0.9 mm, the outer diameter of the outer conductor (801) of the radio frequency cable is OD83 = 0.6-1.1 mm, the exposed length of the inner conductor (803) is L81 = 3-5 mm, and the exposed length of the dielectric layer (802) is L82 = 0.5-2 mm.

7. The microwave ablation antenna with a tip radiation according to claim 6, characterized in that: when the antenna radiation frequency is 2450 MHz, the outer diameter OD of the antenna main body tube (5) is 1.2-2.1 mm, the gap between the antenna main body tube (5) and the small circular segment of the medium sleeve (2) is filled with conductive medium (3) soldering tin, the thickness of the conductive medium (3) layer is 0.05-0.1 mm, and the conductive medium (3) plays a sealing role between the medium sleeve (2) and the antenna main body tube (5).

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