CN114305676B - Microwave ablation antenna based on disconnected outer conductor structure - Google Patents
Microwave ablation antenna based on disconnected outer conductor structure Download PDFInfo
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- CN114305676B CN114305676B CN202210228352.7A CN202210228352A CN114305676B CN 114305676 B CN114305676 B CN 114305676B CN 202210228352 A CN202210228352 A CN 202210228352A CN 114305676 B CN114305676 B CN 114305676B
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Abstract
The invention provides a microwave ablation antenna based on a disconnected outer conductor structure, and belongs to the technical field of microwave ablation. The ablation antenna comprises an ablation needle rod and a coaxial cable, wherein the tip of the ablation needle rod is conical, and a metal sleeve, an inner conductor, a first dielectric layer, a second dielectric layer, an outer conductor and an insulating dielectric layer are arranged in the ablation needle rod; the coaxial cable is divided into a front section, a middle section and a rear section, the front section inner conductor is welded with the head of the coaxial cable, the outer side of the middle section is sleeved with a metal sleeve, the inner part of the rear section is an inner conductor formed by a metal cylinder, the outer side of the inner conductor is sequentially covered with a dielectric layer II, an outer conductor, an insulating dielectric layer and a metal sleeve, the front end of the metal sleeve is provided with an air layer, and the dielectric layer I is arranged between the metal sleeve and the inner conductor. The ablation antenna does not need water cooling, has smaller diameter and lower damage to a human body; simple structure, under the condition of keeping low S11 parameter, the processing degree of difficulty is low, and in addition, the back radiation is less, and the ablation zone shape can be convenient adjust between spherical and ellipsoid.
Description
Technical Field
The invention relates to the technical field of microwave ablation, in particular to a microwave ablation antenna based on a disconnected outer conductor structure.
Background
In recent years, microwave ablation therapy has become one of the important therapeutic means for treating soft tissues such as liver cancer, kidney cancer, thyroid gland and the like. The microwave ablation is to radiate microwave by using an antenna, the microwave enables ions and polar water molecules in tissues to rotate, vibrate and rub with each other to generate a heat effect, so that a treatment area quickly reaches a high temperature, and the tissues are solidified, dehydrated and necrotized, thereby achieving the purpose of treatment.
As the technologies are increasingly perfect, the microwave ablation of the tumor has the characteristics of simplicity, convenience and safety. Compared with radio frequency, the utility model has high thermal efficiency and short operation time, can ablate the tumor with the diameter of 0.5 to 5cm in several seconds to 30 minutes, reduces the risk in the operation and the pain of the patient, and can control the size of the coagulation volume.
And according to the difference of the tumor shape and size, the clinical requirements on the ablation shape are diversified, in order to ensure complete ablation and reduce the damage to healthy tissues as much as possible, the 'conformal ablation' is a future trend, and on the premise of keeping a safe ablation boundary, the closer the ablation shape and the shape and size of the tumor focus of a patient are, the better.
At present, the mainstream microwave ablation antenna in the market transmits microwave to an antenna radiation end by adopting a coaxial cable, and an outer conductor of the coaxial cable can form induced current in the antenna radiation process, so that an ablation area is uncontrollable, and a drop-shaped ablation shape is formed. At present, the mainstream solution is to use a choke ring or a slot antenna, or to use water or the like as a cooling medium to cool the rear end of the microwave emitting region, thereby preventing the needle rod from burning the normal tissue.
For the two measures, the choke ring needs to satisfy 1/4 wavelength (the wavelength is about 2cm generally) in design to form high impedance to the waveform so as to suppress the induced current of the coaxial cable outer conductor. The dielectric properties of the tumor tissue change with increasing temperature, resulting in a decrease in the surface current suppression performance of the choke ring. Microwave energy is radiated in the lesion by notching the outer conductor of the coaxial line. However, in order to obtain a required ablation shape, the length of the currently opened groove is long, the distance between the grooves is large, so that the energy radiation part of the ablation needle is too long, an ablation area generated by gap radiation is in an ellipsoid shape, the roundness is small, the energy of the tip of the antenna is less, and the tail burning effect is easy to generate. If the needle rod is internally provided with the water cooling channel, the needle body of the ablation needle becomes thick, and the damage to the human body is large; meanwhile, the structure and process of the ablation needle become complicated, and thus reliability and safety are reduced; because of water cooling, water inlet and outlet pipes need to be connected, the load of the water inlet and outlet pipes influences the operation accuracy and stability of doctors during operation, and a specially-assigned person needs to support the wire pipes when the thyroid gland and other tumors are treated.
Therefore, there is a need to design a microwave ablation needle that can generate a spherical or ellipsoidal ablation region without water cooling or choke ring and other structures and additional parts, is convenient for clinical use, and has a simple structure and is convenient for processing.
Disclosure of Invention
The invention aims to provide a microwave ablation antenna based on a disconnected outer conductor structure.
The ablation antenna comprises an ablation needle rod and a coaxial cable, wherein the tip of the ablation needle rod is conical to provide a puncture effect, and the ablation needle rod comprises a metal sleeve, an inner conductor, a first dielectric layer, a second dielectric layer, an outer conductor and an insulating dielectric layer;
the coaxial cable is composed of an inner conductor, an outer conductor and a dielectric layer, the coaxial cable is divided into a front section, a middle section and a rear section, the front section inner conductor is welded with the outer conductor at the head of the coaxial cable, a metal sleeve is sleeved outside the middle section, the middle section disconnects the outer conductor, the inner conductor composed of a metal cylinder is arranged inside the rear section, the outer side of the inner conductor is sequentially covered with a dielectric layer II, the outer conductor, an insulating dielectric layer and a metal sleeve, an air layer is reserved at the front end of the metal sleeve, and the dielectric layer I is arranged between the metal sleeve and the inner conductor.
Wherein the coaxial cable head is machined to a desired shape based on impedance matching requirements.
The outer conductor and the metal sleeve are metal circular columns.
The outer conductor is of a disconnected structure, the outer conductor is disconnected backwards at a position 5mm away from the top end of the head of the coaxial cable, and generally, a gap of 4-8 mm is reserved between the outer conductor at the rear section of the cable and the outer conductor at the head of the coaxial cable, so that an open circuit is formed between the outer conductor and the head of the coaxial cable.
The metal sleeve sets up in coaxial cable's middle section, and is general, and metal sleeve length is 9~13mm, and metal sleeve leaves 0.5~2 mm's clearance apart from the coaxial cable head for the transmission of microwave energy. The spherical ablation area and the ellipsoidal ablation area can be controlled by using metal sleeves with different lengths during processing and manufacturing.
The first dielectric layer is positioned at the front end of the metal sleeve, the length of the first dielectric layer is smaller than that of the metal sleeve, and the second dielectric layer, the outer conductor and the insulating dielectric layer are sequentially arranged between the rear end of the metal sleeve and the inner conductor from inside to outside.
The diameter of the metal sleeve is about 1.4-1.6 mm, the metal sleeve is sleeved with the dielectric layer, and the metal sleeve and the outer conductor form an open circuit.
The dielectric is polytetrafluoroethylene.
The operating frequency of the ablation antenna is 2450 +/-50 MHz.
The ablation needle bar is made of polytetrafluoroethylene, and the outer side of the ablation needle bar is coated with a high-temperature resistant anti-sticking coating to prevent the tissue from being stuck with the needle bar at high temperature.
In order to realize the optimal impedance matching of the antenna, the top end of the antenna is processed into a required shape, such as a metal ring with a slightly larger welding diameter; the metal sleeve of the middle section of the coaxial cable can be thickened towards the inner side part, the thickened part can be welded on the metal sleeve and can also be integrally formed with the metal sleeve, and the thickened part can be processed into a specific size and a specific shape according to the requirement; the sleeve and the rear side gap of the coaxial cable are filled with polytetrafluoroethylene.
The technical scheme of the invention has the following beneficial effects:
1. the invention does not need water cooling, reduces the diameter of the antenna and has less damage to the human body;
2. a cooling water channel is not required to be added in the ablation needle, so that the complexity of the processing technology is reduced, and the reliability and safety are improved;
3. when the medical water supply device is used clinically, a water inlet and outlet pipe does not need to be connected, so that the influence of the load of the water inlet and outlet pipe on the operation accuracy and stability of a doctor during operation is avoided;
4. the invention has simple structure, does not have more technological requirements such as welding, riveting and the like under the condition of keeping low S11 parameters, and has low processing difficulty;
5. the invention has less gaps, is concentrated at the front end of the coaxial line, has higher intensity and concentrates energy radiation at the tip;
6. the ablation antenna produced by the invention has small backward radiation, and the shape of the ablation area can be conveniently adjusted between a spherical shape and an ellipsoidal shape.
Drawings
FIG. 1 is a schematic structural view of a microwave ablation antenna based on a disconnected outer conductor structure according to the present invention;
FIG. 2 is a cross-sectional view A of FIG. 1;
FIG. 3 is a cross-sectional view B of FIG. 1;
FIG. 4 is a graph showing the simulation result of the S parameter of the microwave ablation antenna based on the disconnected outer conductor structure in the liver according to the embodiment of the present invention;
fig. 5 is a graph of the simulation result of the 2.45GHz temperature field of the microwave ablation antenna based on the disconnected outer conductor structure in the liver in the embodiment of the invention.
Wherein: 1-an ablation needle bar; 2-an air layer; 3-a metal sleeve; 4, a first dielectric layer; 5-an inner conductor; 6-insulating medium layer; 7-an outer conductor; 8-medium layer II; 9-coaxial cable head.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
The invention provides a microwave ablation antenna based on a disconnected outer conductor structure.
As shown in fig. 1, fig. 2 and fig. 3, the ablation antenna comprises an ablation needle rod 1 and a coaxial cable, wherein the coaxial cable is arranged in the ablation needle rod 1, the tip of the ablation needle rod 1 is conical, and the ablation needle rod 1 comprises a metal sleeve 3, an inner conductor 5, a first dielectric layer 4, a second dielectric layer 8, an outer conductor 7 and an insulating dielectric layer 6;
the coaxial cable is composed of an inner conductor, an outer conductor and a dielectric layer and is divided into a front section, a middle section and a rear section, wherein the front section is a head of the coaxial cable, a second dielectric layer 8 is arranged outside the inner conductor of the front section, the end part of the inner conductor of the front section is wrapped by the outer conductor of the front section, the end part of the inner conductor of the front section is welded with the outer conductor, the outer conductor of the middle section is disconnected, a metal sleeve is sleeved at the disconnected part, an inner conductor composed of a metal cylinder is arranged inside the rear section, the second dielectric layer 8, the outer conductor 7, an insulating dielectric layer 6 and a metal sleeve 3 are sequentially covered on the outer side of the inner conductor 5, an air layer 2 is reserved at the front end of the metal sleeve 3, and a first dielectric layer 4 is arranged between the metal sleeve 3 and the inner conductor 5.
The outer conductor 7 and the metal sleeve 3 are metal circular columns.
The outer conductor 7 is of a disconnected structure, and a gap of 4-8 mm is formed between the outer conductor at the rear section of the cable and the head part 9 of the coaxial cable, so that an open circuit is formed between the outer conductor 7 and the head part 9 of the coaxial cable.
The length of the metal sleeve 3 is 9-13mm, and a gap of 0.5-2 mm is reserved between the metal sleeve 3 and the coaxial cable head 9 and used for transmitting microwave energy.
The first dielectric layer 4 is positioned at the front end of the metal sleeve 3, the length of the first dielectric layer is smaller than that of the metal sleeve 3, and a second dielectric layer 8, an outer conductor 7 and an insulating dielectric layer 6 are sequentially arranged between the rear end of the metal sleeve 3 and the inner conductor 5 from inside to outside.
The diameter of the metal sleeve 3 is 1.4-1.6 mm, the metal sleeve 3 is sleeved with the dielectric layer I4, and the metal sleeve 3 and the outer conductor 7 form an open circuit.
The dielectric layer 6 is made of polytetrafluoroethylene.
The operating frequency of the ablation antenna is 2450 +/-50 MHz.
The outside of the ablation needle rod 1 is coated with a high-temperature resistant anti-sticking coating.
In the specific design, the coaxial cable inner conductor 5 and the coaxial cable head 9 outer conductor are welded into a whole, the metal sleeve 3 and the dielectric layer I4 are sleeved on the coaxial cable inner conductor 5, and the insulating dielectric layer 6 is filled between the extending part of the rear part of the metal sleeve 3 and the coaxial cable outer conductor 7.
The outer side of the ablation needle rod 1 is coated with a high-temperature resistant anti-sticking coating, such as a PTFE coating, the ablation needle rod is made of polytetrafluoroethylene, and the diameter of the ablation needle rod is 1.8 mm;
the inner conductor 5 of the cable is welded with the outer conductor of the head part 9 of the coaxial cable, the welding method can adopt tin soldering, laser welding, brazing and the like, various conductive metals can be selected on the materials, such as copper, iron, aluminum, gold, silver or alloys thereof, and the like, wherein the copper and metal surface are preferably plated with copper or copper alloy materials, and the diameter of the inner conductor is 0.27 mm;
the length of the coaxial cable head part 9 is 5mm, the shape can be different according to the antenna impedance matching requirement and the processing mode, and various shapes can be adopted;
the first dielectric layer 4 and the second dielectric layer 8 are both filled with dielectric inside the cable and have high relative dielectric constants such as high-temperature-resistant microwave dielectric ceramic and the like, the first dielectric layer 4 and the second dielectric layer 8 can be formed integrally or formed separately and then spliced, wherein the first dielectric layer 4 is 6mm in length and 0.94mm in outer diameter;
the inner diameter of the metal sleeve 3 is about 1.44mm, the material is preferably copper, copper plated or copper alloy materials on the metal surface, the length can be changed according to the shape of a target tumor, usually 9-13mm, the sleeved part of the metal sleeve 3 and the dielectric layer I4 can adopt different shapes according to impedance matching and processing modes, the middle part of the metal sleeve 3 protrudes inwards, the inward protruding part is processed by other processes such as welding or riveting, and the like, and can also be directly formed integrally;
an air layer 2 with the length of about 1mm is left between the front end of the metal sleeve 3 and the front end of the first dielectric layer 4; the gap between the metal sleeve 3 and the cable outer conductor 7 with the outer diameter of 1.19mm is filled with an insulating medium layer 6, preferably a high-temperature resistant plastic material such as polytetrafluoroethylene.
After the ablation antenna is designed, the simulation result of the S parameter of the ablation antenna in the liver is shown in fig. 4, and fig. 4 can show the return loss characteristic of the antenna at 2.45GHz, wherein the parameter represents the transmission efficiency of the antenna at the frequency, and the larger the value is, the larger the energy reflected by the antenna is, so the worse the efficiency of the antenna is; the simulation result of the 2.45GHz temperature field of the 30W ablation in the liver for 10min is shown in FIG. 5, and FIG. 5 shows that the size and shape of the ablation region can be estimated according to the 2.45GHz temperature field distribution after the 30W ablation in the liver for 10 min.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (9)
1. A microwave ablation antenna based on a disconnected outer conductor structure comprises an ablation needle rod and a coaxial cable, and is characterized in that the tip of the ablation needle rod is conical, and a metal sleeve, an inner conductor, a first dielectric layer, a second dielectric layer, an outer conductor and an insulating dielectric layer are arranged in the ablation needle rod;
the coaxial cable is composed of an inner conductor, an outer conductor and a dielectric layer, the coaxial cable is divided into a front section, a middle section and a rear section, the front section inner conductor is welded with the outer conductor at the head of the coaxial cable, the middle section is disconnected with the outer conductor, a metal sleeve is sleeved on the outer side of the front section, the inner conductor composed of a metal cylinder is arranged in the rear section, a dielectric layer II, the outer conductor, an insulating dielectric layer and a metal sleeve are sequentially covered on the outer side of the inner conductor, an air layer is reserved at the front end of the metal sleeve, and the dielectric layer I is arranged between the metal sleeve and the inner conductor;
the diameter of the metal sleeve is 1.4-1.6 mm, the metal sleeve is sleeved with the dielectric layer, and the metal sleeve and the outer conductor form an open circuit.
2. A microwave ablation antenna based on a disconnected outer conductor structure according to claim 1, characterized in that the coaxial cable head is processed into a required shape based on the need of impedance matching.
3. A microwave ablation antenna based on a disconnected outer conductor structure according to claim 1, characterized in that the outer conductor and the metal sleeve are metal circular cylinders.
4. The microwave ablation antenna based on the disconnected outer conductor structure according to claim 1, wherein the outer conductor is in a disconnected structure, and a gap of 4-8 mm is disconnected backwards at a position 5mm away from the top end of the coaxial cable head, so that an open circuit is formed between the outer conductor and the coaxial cable head.
5. The microwave ablation antenna based on the disconnected outer conductor structure according to claim 1, wherein the length of the metal sleeve is 9-13mm, and a gap of 0.5-2 mm is left between the metal sleeve and the head of the coaxial cable for transmitting microwave energy.
6. The microwave ablation antenna based on the disconnected outer conductor structure according to claim 1, wherein the first dielectric layer is located at the front end of the metal sleeve, the length of the first dielectric layer is smaller than that of the metal sleeve, and the second dielectric layer, the outer conductor and the insulating dielectric layer are sequentially arranged between the rear end of the metal sleeve and the inner conductor from inside to outside.
7. The microwave ablation antenna based on the disconnected outer conductor structure according to claim 1, wherein the dielectric layer is made of polytetrafluoroethylene.
8. A disconnected outer conductor structure-based microwave ablation antenna according to claim 1, wherein the ablation antenna has an operating frequency of 2450 ± 50 MHz.
9. The microwave ablation antenna based on the disconnected outer conductor structure according to claim 1, wherein the ablation needle rod is made of polytetrafluoroethylene, and the outer side of the ablation needle rod is coated with a high-temperature resistant anti-sticking coating.
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| CN115966867B (en) * | 2022-12-23 | 2024-03-12 | 南京林业大学 | Microwave isolator suitable for medical field |
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| CN103717166A (en) * | 2011-04-08 | 2014-04-09 | 柯惠有限合伙公司 | Flexible microwave catheters for natural or artificial lumens |
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| CN110523003A (en) * | 2019-09-23 | 2019-12-03 | 南京臻泰微波科技有限公司 | A kind of tumor microwave ablation needle without water cooling |
| CN209826967U (en) * | 2019-04-25 | 2019-12-24 | 南京康友医疗科技有限公司 | Microwave ablation needle body and microwave ablation needle |
| CN111012483A (en) * | 2019-12-31 | 2020-04-17 | 华南理工大学 | Microwave ablation antenna based on spiral gap structure |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7611508B2 (en) * | 2005-08-23 | 2009-11-03 | Wisconsin Alumni Research Foundation | Floating sleeve microwave antenna for tumor ablation |
| US8556889B2 (en) * | 2009-09-29 | 2013-10-15 | Covidien Lp | Flow rate monitor for fluid cooled microwave ablation probe |
| GB2574219A (en) * | 2018-05-30 | 2019-12-04 | Creo Medical Ltd | Electrosurgical instrument |
| US20210128231A1 (en) * | 2019-11-04 | 2021-05-06 | Medwaves, Inc. | Energy transmitting therapeutic medical device |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103717166A (en) * | 2011-04-08 | 2014-04-09 | 柯惠有限合伙公司 | Flexible microwave catheters for natural or artificial lumens |
| CN209826967U (en) * | 2019-04-25 | 2019-12-24 | 南京康友医疗科技有限公司 | Microwave ablation needle body and microwave ablation needle |
| CN110507414A (en) * | 2019-09-16 | 2019-11-29 | 浙江大学 | A kind of more gap microwave melt needles |
| CN110523003A (en) * | 2019-09-23 | 2019-12-03 | 南京臻泰微波科技有限公司 | A kind of tumor microwave ablation needle without water cooling |
| CN111012483A (en) * | 2019-12-31 | 2020-04-17 | 华南理工大学 | Microwave ablation antenna based on spiral gap structure |
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