Single pump closed loop temperature and directional cooling ultrasonic ablation catheter and control method

Abstract

The application discloses a kind of single-pump closed-loop control diameter and directional cooling ultrasonic ablation catheter and control method, belong to the technical field of interventional medical instrument. Including ablation host, with the drive unit of electric connection of ablation host and the interventional catheter unit of drive unit connection, cooling liquid in first cooling flow channel directional flow along the surface of ultrasonic transducer, realize once forced convection heat exchange.The part of cooling liquid after once heat exchange is discharged into blood vessel through tip head liquid chamber, another part is driven by balloon pressure and enters second cooling flow channel through overflow structure, flows through the inside of insulating tube and carries out secondary heat exchange to the adjacent area of transducer inner wall and then is discharged.Two flow channels are unidirectional orderly flow, cooling liquid is sequentially flowed through the outer wall and inner wall of transducer by physical structure constraint, can simultaneously carry out heat exchange to outer wall and inner wall.Cooling liquid after heat exchange is directly discharged into blood vessel, absorbed by human metabolism, without extracorporeal circulation loop, to reduce the additional flow resistance of reflux pipeline, pollution risk and the number of structural components.

Description

Technical Field

[0001] This invention relates to the field of interventional medical device technology, specifically to an ultrasonic ablation catheter and control method with single-pump closed-loop diameter control and directional cooling. Background Technology

[0002] In the field of interventional ultrasound ablation catheters via the radial artery approach (TRA), a core challenge lies in achieving intelligent control of the balloon's outer diameter while compressing the catheter's outer diameter and cooling the ultrasound transducer. Existing technologies present three typical solutions, each with its own problems: Option 1: Passive flow resistance diameter control scheme, existing technology (CN109419958B). This scheme designs the inlet water channel with a cross-sectional area much larger than the return water channel, and uses the return water flow resistance to passively establish a pressure difference inside the balloon, causing the balloon to expand and change diameter.

[0003] Option 2: Mechanically variable outer diameter solution, existing technology (CN115039860B). This solution uses a fixed cooling balloon to encase the transducer, with an additional mechanically variable outer diameter structure (such as a shape memory metal woven basket) superimposed on the outer layer to achieve wall-attached ablation.

[0004] Option 3: Proximal blind convection spray solution, existing technology (CN104116514B). This solution involves creating spray holes at the proximal root of the balloon to provide non-directional scattering perfusion cooling to the balloon cavity.

[0005] In existing variable diameter implementations, when establishing a pressure difference using flow resistance and pressure buildup, the operating pressure typically needs to reach above 3 atm. Under this pressure condition, the coolant flow rate is limited, leading to a decrease in heat exchange efficiency. Simultaneously, the flow order within the balloon is reduced, potentially resulting in localized temperature gradients. Furthermore, some solutions employ an external circulation loop to maintain coolant circulation, which introduces additional flow resistance and contamination paths, and increases the number of system components. Currently, there are no publicly reported solutions using a single duct to simultaneously achieve closed-loop control of the balloon's outer diameter and cooling of the transducer's inner and outer walls under single-pump drive and operating pressures below 1 atm. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a single-pump closed-loop diameter control and directional cooling ultrasonic ablation catheter, comprising an ablation host, a drive unit electrically connected to the ablation host, and an interventional catheter unit connected to the drive unit; the drive unit is used to pump coolant into the interventional catheter unit; the interventional catheter unit includes a handle, a tube shaft connected to the handle, a balloon fixed to the distal end of the tube shaft, a tip fixed to the distal end of the balloon, and an ultrasonic transducer disposed within the balloon; the interventional catheter unit is provided with a first cooling channel, which is supplied with coolant by the drive unit through a pipeline; the coolant is used to inflate the balloon and perform initial heat exchange on the outer wall of the ultrasonic transducer; a portion of the coolant after heat exchange is discharged from the tip. It also includes a second cooling channel, where another portion of the coolant, after heat exchange in the first cooling channel, enters under the pressure of the balloon, performs secondary heat exchange on the inner wall of the ultrasonic transducer, and is then discharged from the tip.

[0007] Preferably, the first cooling channel includes a handle water inlet chamber disposed in the handle, a water inlet chamber disposed in the tube shaft, a balloon inner cavity, and a tip liquid outlet chamber disposed in the tip, which are connected in sequence. The handle water inlet chamber is connected to the drive unit through a pipeline. The drive unit drives the coolant to enter the handle water inlet chamber. After entering the inner cavity of the balloon through the water inlet chamber, a portion of the coolant is discharged from the tip liquid outlet chamber.

[0008] Preferably, the second cooling channel includes a balloon inner cavity, an overflow structure, an inner cavity of an insulating tube, and a tip center cavity disposed within the tip, which are connected in sequence. Another portion of the coolant in the second cooling channel flows from the inner cavity of the balloon through the overflow structure into the inner cavity of the insulating tube, and then is discharged from the central cavity of the tip. The other part of the coolant is the coolant that enters the second cooling channel from the inner cavity of the balloon through the overflow structure.

[0009] Preferably, the insulating tube is inserted into the tube shaft, and the distal end of the insulating tube is fixedly connected to the tip and communicates with the central cavity of the tip; a support structure is installed on the outer wall of the insulating tube located inside the balloon, and the ultrasonic transducer is fitted and fixed to the outer wall of the support structure; the overflow structure is set on the insulating tube and located between the ultrasonic transducer and the distal end of the tube shaft, and the coolant in the insulating tube is introduced through the overflow structure to exchange heat with the support structure, so as to realize secondary heat exchange of the inner wall of the ultrasonic transducer.

[0010] Preferably, the overflow structure includes a single overflow hole penetrating the wall of the insulating tube, or multiple overflow holes that are non-uniformly distributed in the circumferential direction.

[0011] Preferably, the tip is provided with an axially extending partition strip, which divides the tip cavity into two tip fluid outlet chambers and a tip central chamber arranged symmetrically in the circumferential direction. The proximal end of the tip fluid outlet chamber is connected to the balloon cavity, and the distal end is connected to a blood vessel. The proximal end of the tip central chamber is fixedly connected to and connected to an insulating tube, and the distal end is connected to a blood vessel.

[0012] Preferably, a pressure sensor electrically connected to the ablation host is provided inside the balloon, and the pressure sensor is used to detect the actual pressure inside the balloon and transmit the pressure signal to the ablation host; The balloon is a low-pressure compliant balloon. The ablation unit determines the desired pressure based on the target outer diameter and adjusts the infusion parameters of the drive unit based on the deviation between the desired pressure and the actual pressure, so that the balloon inflates and remains at the target outer diameter. The pressure sensor is a high-frequency piezoresistive miniature medical pressure sensor; the steady-state working pressure of the balloon is 0.3 to 0.9 atm; the preset safety pressure threshold set by the ablation host is 1 atm.

[0013] Preferably, the inlet of the drive unit is connected to the coolant storage device through a pipeline, and the outlet of the drive unit is connected to the handle water inlet chamber through a pipeline. The coolant in the storage device is delivered to the handle water inlet chamber through the drive unit. The drive unit is a single pump, which is selected from any one of a peristaltic pump, a plunger pump, a diaphragm pump, or a micro liquid pump.

[0014] Preferably, the tube shaft has a three-cavity structure, including a central cavity, a water inlet cavity, and a sealed conductor cavity; the conductor cavity is used to run electrical conductors to achieve isolation between the fluid channel and the electrical channel.

[0015] A single-pump closed-loop diameter control and directional cooling control method, applied to an ultrasonic ablation system, includes the following steps: Receive the target outer diameter of the target balloon and determine the desired pressure corresponding to the target outer diameter; The drive unit is controlled to deliver coolant to the interventional catheter unit. The coolant exchanges heat with the outer and inner walls of the ultrasonic transducer in the first and second cooling channels respectively before being discharged. The actual pressure inside the balloon is obtained in real time through the pressure sensor. The output of the drive unit is adjusted based on the comparison between the actual pressure and the desired pressure, so that the balloon inflates and remains at the target outer diameter; When the actual pressure reaches or exceeds a preset safety threshold, a safety cutoff strategy is triggered. The safety cutoff strategy includes controlling the drive unit to slow down, stop the pump, or enter a pressure relief mode.

[0016] The technical effects and advantages of this invention are as follows: 1. In this invention, within the interventional catheter unit, the coolant in the first cooling channel flows directionally along the surface of the ultrasonic transducer, achieving a single forced convection heat exchange. A portion of the coolant, after this initial heat exchange, is discharged into the blood vessel through the tip outlet chamber, while the remaining portion, driven by balloon pressure, flows into the second cooling channel via an overflow structure. It then flows through the interior of the insulating tube and performs a secondary heat exchange on the adjacent area of ​​the transducer's inner wall before being discharged. Both channels exhibit unidirectional, orderly flow, with the coolant, constrained by the physical structure, flowing sequentially through the outer and inner walls of the transducer, allowing for simultaneous heat exchange with both walls. The cooled coolant, after heat exchange, is directly discharged into the blood vessel for absorption by the body's metabolism, eliminating the need for an extracorporeal circulation loop. This reduces the additional flow resistance, contamination risk, and number of structural components associated with the return pipeline.

[0017] 2. The drive unit employs a single pump, serving as the system's sole primary coolant delivery power source. It delivers coolant unidirectionally to the bladder cavity via the inlet chamber within the tube shaft. This single pump handles both diameter control and cooling drive functions, eliminating the need for a secondary power source or passive flow resistors. Compared to multi-power-source solutions, the single pump reduces pump shutdown response time, and compared to dual-pump solutions, it allows for faster power output cutoff.

[0018] 3. The coolant discharged from the tip directly enters the target blood vessel area, continuously flushing and physically cooling the vascular intima and adjacent tissues affected by heat during ablation treatment. This reduces the risk of thrombosis and microchannel blockage caused by blood backflow and aspiration, thereby improving the safety of the procedure.

[0019] 4. This invention employs a single-pump drive, real-time intra-balloon pressure feedback, and a directional flow-guiding design with an overflow structure. A pressure sensor inside the balloon detects the intra-balloon pressure in real time and feeds it back to the ablation unit. The ablation unit actively and frequently adjusts the pump speed of the single pump to achieve closed-loop control of the balloon's outer diameter.

[0020] 5. An overflow structure is positioned between the ultrasonic transducer and the distal end of the tube shaft, transforming the coolant flow from disordered diffusion to unidirectional ordered flow. The coolant is forced by the physical structure to flow through the transducer's highest heat-generating area, thus achieving thermal management, directional cooling of the ultrasonic transducer, and reducing the risk of thermal damage.

[0021] 6. A three-lumen tube structure with current-electric isolation and a distal three-lumen tip structure are adopted, integrating fluid and electrical functions and reducing the overall outer diameter of the interventional catheter unit. The central lumen of the tip serves as the main channel for the guidewire and is directly connected to the internal flow channel of the insulating tube. Under the action of the overflow structure, some water flows into the insulating tube through the overflow structure driven by the pressure difference and flows out from the central lumen of the tip, continuously flushing and carrying away the heat inside the ultrasonic transducer through heat conduction. Two symmetrical tip outlet chambers are directly connected to the inner lumen of the balloon, serving as the main channel for the discharge of coolant from the balloon. When the drive unit continuously injects coolant unidirectionally into the balloon, the coolant is discharged symmetrically through the two tip outlet chambers, placing the ultrasonic transducer in a convective cooling environment. Closed-loop control of the balloon pressure is achieved through real-time feedback from pressure sensors.

[0022] 7. The balloon is made of low-hardness polymer material, making it a low-pressure compliant balloon with a working pressure range of 0.3–0.9 atm, allowing for continuous diameter variations of 4–12 mm within this pressure range. The balloon exhibits flexibility and wall-adherence at low pressure, enabling it to adapt to irregular vessel walls. Its working pressure is lower than that of high-pressure balloons, reducing the mechanical risk of balloon rupture due to overpressure.

[0023] 8. After the coolant flows into the balloon in one direction, it is directly drained into the blood vessel through the internal flushing circuit of the insulating tube (drained from the central cavity of the tip) and the balloon drainage circuit (drained from the two tip drainage chambers), eliminating the need for an extracorporeal circulation circuit. This reduces the number of system components, simplifies the overall architecture of the ablation system, and lowers manufacturing costs. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall architecture of the single-pump closed-loop diameter control and directional cooling ultrasonic ablation catheter provided in the embodiments of this application; Figure 2 This is a schematic diagram of the interventional catheter unit in the single-pump closed-loop diameter control and directional cooling ultrasonic ablation catheter provided in the embodiments of this application; Figure 3 This is a cross-sectional schematic diagram of the interventional catheter unit in the single-pump closed-loop diameter control and directional cooling ultrasonic ablation catheter provided in the embodiments of this application; Figure 4 This is a schematic diagram of the unidirectional flow channel of coolant in the interventional catheter unit of the single-pump closed-loop diameter control and directional cooling ultrasonic ablation catheter provided in the embodiments of this application; Figure 5 This is a schematic cross-sectional view of the tube axis of the ultrasonic ablation catheter with single-pump closed-loop diameter control and directional cooling provided in the embodiments of this application; Figure 6 This is a schematic cross-sectional view of the tip of the ultrasonic ablation catheter with single-pump closed-loop diameter control and directional cooling provided in the embodiments of this application; Figure 7This is a schematic cross-sectional view of the balloon inflated state in the single-pump closed-loop diameter control and directional cooling ultrasonic ablation catheter provided in the embodiments of this application; Figure 8 This is a flowchart of the control method for a single-pump closed-loop diameter control and directional cooling ultrasonic ablation catheter provided in the embodiments of this application; Figure 9 This is a block diagram illustrating the principle of the closed-loop control system for a single-pump closed-loop diameter control and directional cooling ultrasonic ablation catheter provided in this application embodiment; Figure 10 This is a flowchart of the PI / PID algorithm for a single-pump closed-loop diameter control and directional cooling ultrasonic ablation catheter provided in an embodiment of this application. Figure 11 This is a flowchart of the closed-loop control algorithm for a single-pump closed-loop diameter control and directional cooling ultrasonic ablation catheter provided in an embodiment of this application; Figure 12 This is a schematic diagram comparing the pressure and balloon diameter in a single-pump closed-loop diameter control and directional cooling ultrasonic ablation catheter provided in the embodiments of this application.

[0025] In the diagram: 100, ablation unit; 200, drive unit; 300, interventional catheter unit; 310, handle; 311, handle water inlet chamber; 320, tube shaft; 321, tube shaft central cavity; 322, water inlet chamber; 323, insulating tube; 324, wire cavity; 325, electrical wire; 330, balloon; 331, ultrasonic transducer; 332, support structure; 333, overflow structure; 334, pressure sensor; 335, temperature sensor; 340, tip; 341, separator; 342, tip liquid outlet chamber; 343, tip central cavity; 400, coolant. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

[0027] Please see Figures 1-2As shown, this embodiment provides a single-pump closed-loop diameter control and directional cooling ultrasonic ablation catheter for intravascular ultrasonic ablation of renal arteries, pulmonary arteries, peripheral arteries, or other vascular tissues. It comprises three core modules: an ablation host 100, a drive unit 200 electrically connected to the ablation host 100, and an interventional catheter unit 300 connected to the drive unit 200. The drive unit 200 pumps coolant 400 into the interventional catheter unit 300. The coolant 400 is stored in a storage device, which is connected to the drive unit 200 via a pipeline. The inlet of the drive unit 200 is connected to the coolant 400 storage device via a pipeline, and the outlet of the drive unit 200 is connected to the handle inlet chamber 311 via a pipeline. The drive unit 200 delivers the coolant 400 from the storage device to the handle inlet chamber 311.

[0028] Specifically, the drive unit 200 employs a brake-like braking method, utilizing the reverse electromagnetic torque of the motor to counteract rotational inertia. The brake-like braking is achieved by the motor driver of the drive unit 200 applying a reverse current to the motor windings after receiving a braking command from the ablation host 100, or through an integrated electromagnetic mechanical brake device. Within 35ms, the high-speed rotating pump shaft is brought to a stop, cutting off fluid power at its source. Simultaneously, the normally closed, normally powered, normally closed miniature electromagnetic pressure relief valve located on the inlet side of the near-end handle 310 is instantly de-energized and reset, opening the external physical pressure relief path. Through full-link physical testing, the total response time from the detection of the over-limit anomaly by the pressure sensor 334 to the motor stopping and initiating pressure relief is 45ms to 65ms. This verifies the design goal of completing a safe response within 100ms. By limiting the steady-state working pressure of the balloon to 0.3 to 0.9 atm (lower than the 2 to 6 atm of the prior art), and setting a preset safety pressure threshold of 1 atm and a full-link safety response mechanism of 45ms to 65ms, the mechanical risk of balloon overpressure rupture can be reduced.

[0029] The drive unit 200 is a single pump, which serves as the only power source for the delivery of the main coolant 400 in the system. It is responsible for unidirectionally delivering the coolant 400 through the water inlet chamber 322 inside the tube shaft 320 to the inner cavity of the balloon 330. Using a single pump, compared to multiple power sources, the control system of the ablation host 100 is simpler and the response time is reduced.

[0030] The drive unit 200 performs the dual functions of controlling the diameter of the balloon 330 and driving the coolant 400, without requiring a second power source or passive flow resistor.

[0031] The pressure sensor 334 installed inside the balloon of this invention allows the ablation host 100 to actively and frequently regulate the water inlet velocity of the drive unit 200. Under low pressure conditions below 1 atm, continuous outer diameter adjustment is achieved through volumetric micro-compensation, reducing the risk of mechanical damage from vascular dissection. The drive unit 200 is a single pump, serving as the sole power source for the main coolant 400. It is responsible for unidirectionally delivering the coolant 400 through the inlet chamber 322 within the tube shaft 320 to the inner cavity of the balloon 330. The single pump performs both diameter control and cooling functions, eliminating the need for a second power source or passive flow resistor. Compared to multiple power sources, the single pump reduces pump stop response time (<100ms), allowing for faster power output cutoff compared to a dual-pump solution.

[0032] Specifically, the single pump is selected from any one of peristaltic pumps, plunger pumps, diaphragm pumps, or micro liquid pumps.

[0033] Furthermore, the ablation host 100 serves as the system control center. The ablation host 100 has an embedded closed-loop control algorithm module and a monitoring module. The ablation host 100 also has an independent hard real-time monitoring module, which operates decoupled from the conventional closed-loop control loop and has the highest level of system interrupt execution priority.

[0034] Furthermore, a pressure sensor 334 is installed inside the balloon 330. The pressure sensor 334 is electrically connected to the ablation host 100. The pressure sensor 334 is used to detect the actual pressure inside the balloon 330 and transmit the pressure feedback signal to the ablation host 100. The ablation unit 100 determines the target outer diameter of the balloon 330 based on the inner diameter of the blood vessel, determines the desired pressure based on the target outer diameter, and adjusts the pump speed, flow rate or infusion volume of the drive unit 200 based on the deviation between the desired pressure and the actual pressure, so that the balloon 330 inflates and remains at the target outer diameter under a steady-state pressure below a preset safety threshold.

[0035] Specifically, the closed-loop control algorithm module receives the real-time pressure signal from the pressure sensor 334 located in the inner cavity of the balloon 330, compares it with the target pressure, and then outputs a pump speed adjustment command to the drive unit 200.

[0036] The balloon 330 is controlled by the closed-loop control algorithm of the pressure sensor 334 and the ablation host 100, so that the balloon 330 expands and adheres to the inner wall of the blood vessel under a steady-state pressure of less than 1 atm, with a diameter control accuracy of ±0.5 mm (this accuracy has been verified by in vitro animal experiments, under the following conditions: the compliant balloon is made of TPU45A material with a wall thickness of 0.060 to 0.070 mm, and the pressure inside the balloon is adjusted in real time by the closed-loop control system under vascular constraint conditions, and the measured deviation of the outer diameter of the balloon is within ±0.5 mm).

[0037] Specifically, the pressure sensor 334 is a high-frequency piezoresistive miniature medical pressure sensor (with an inherent hardware response time of ≤1ms), and its signal output terminal is connected to the 24-bit high-frequency ADC sampling circuit of the ablation host 100.

[0038] The monitoring module continuously monitors the pressure inside the balloon 330. When the pressure exceeds the safety threshold or abnormal fluctuations occur, a safety cutoff strategy is triggered.

[0039] Specifically, the signal sampling frequency of this monitoring module is set to 1kHz (i.e., capturing the intracystic pressure signal once every 1ms). When the actual intracystic pressure P_actual ≥ 1.0atm (preset absolute safety upper limit threshold) is captured in any monitoring cycle, or the rise slope of the actual pressure dP / dt ≥ 0.8atm / s in three consecutive sampling cycles (determined as acute vasospasm or accidental bend and blockage of the tubing), the system immediately triggers a hardware external interrupt (ISR). This interrupt program completes the logical decision within a 2ms software delay and forcibly pulls the stepper motor pulse enable pin of the drive unit 200 low, sending a reverse braking current to the motor drive chip.

[0040] Please see Figure 3-6 As shown, the interventional catheter unit 300 further includes a handle 310, a tube shaft 320 connected to the handle 310, a balloon 330 fixed to the distal end of the tube shaft 320, a tip 340 fixed to the distal end of the balloon 330, and an ultrasonic transducer 331 disposed in the balloon 330. The interventional catheter unit 300 is provided with a first cooling channel, which is supplied with coolant 400 by the drive unit 200 through a pipeline. The coolant 400 is used to inflate the balloon 330 and perform initial heat exchange on the outer wall of the ultrasonic transducer 331. A portion of the coolant 400 after heat exchange is discharged from the tip 340. It also includes a second cooling channel, where another portion of the coolant 400, after heat exchange in the first cooling channel, enters the channel under the pressure of the balloon 330, performs secondary heat exchange on the inner wall of the ultrasonic transducer 331, and is then discharged from the tip 340.

[0041] Specifically, the coolant 400 uses 0.9% medical saline / Ringer's solution, a crystalline liquid that is isotonic with human blood plasma. After entering the bloodstream, it only increases the extracellular fluid volume and does not change the serum sodium ion concentration gradient, thus reducing the risk of dilutional hyponatremia.

[0042] The maximum total volume for a single procedure, and the typical actual output, is 400-500 mL. 500 mL of isotonic saline is equivalent to the routine dose of a standard bag of intravenous fluid in clinical practice. Because the flow rate is low during the intervals between ablation procedures (when changing positions), this 500 mL is slowly accumulated during the 1-2 hour procedure, reducing the burden on the body's circulatory system and kidney metabolism.

[0043] The drive unit 200 pumps the coolant 400 into the first cooling channel, and then into the balloon 330. The infusion parameters of the drive unit 200 are adjusted to inflate the balloon 330. The outer diameter of the balloon 330 is continuously adjustable. The infusion parameters include pump speed, flow rate or infusion volume.

[0044] Furthermore, the first cooling channel includes a handle water inlet chamber 311 disposed in the handle 310, a water inlet chamber 322 disposed in the tube shaft 320, the inner cavity of the balloon 330, and a tip liquid outlet chamber 342 disposed in the tip 340, which are connected in sequence. The handle water inlet chamber 311 inside the handle 310 is connected to the drive unit 200 through a pipeline. The drive unit 200 drives the coolant 400 to enter the handle water inlet chamber 311 through the pipeline. After entering the inner cavity of the balloon 330 through the water inlet chamber 322, a portion of the coolant 400 is discharged into the blood vessel through the tip liquid outlet chamber 342 inside the tip 340.

[0045] Furthermore, the second cooling channel includes the inner cavity of the balloon 330, the overflow structure 333, the inner cavity of the insulating tube 323, and the tip center cavity 343 disposed in the tip 340, which are connected in sequence. Another portion of the coolant 400 in the second cooling channel is introduced from the inner cavity of the balloon 330 through the overflow structure 333 into the inner cavity of the insulating tube 323, and then discharged from the central cavity of the tip 343 to the blood vessel.

[0046] In this invention, the coolant 400 introduced into the first cooling channel of the interventional catheter unit 300 performs a first heat exchange on the surface of the ultrasonic transducer 331. A portion of the first-heat-exchanged coolant 400 is discharged into the blood vessel, while another portion of the first-heat-exchanged coolant 400 is introduced into the second cooling channel under the pressure of the balloon 330 to perform a second heat exchange on the adjacent area of ​​the inner wall of the ultrasonic transducer 331, and then discharged into the blood vessel. The coolant 400 performs two directional convection heat exchanges on the surface or adjacent area of ​​the ultrasonic transducer 331. Furthermore, the coolant 400 flows unidirectionally in both the first and second cooling channels, and after being directly discharged into the blood vessel, it is naturally absorbed by the human body through metabolism, eliminating the need for an extracorporeal circulation loop. This reduces the additional flow resistance, contamination risk, and number of structural components caused by the return pipeline in traditional solutions.

[0047] In this invention, the coolant 400 pumped into the interventional catheter unit 300 by the drive unit 200 is divided into a part and another part. The part refers to the coolant 400 that has undergone only one heat exchange and is discharged from the tip outlet cavity 342. The other part refers to the coolant 400 that has undergone one heat exchange, enters the second cooling channel for a second heat exchange, and is then discharged from the tip center cavity 343.

[0048] Specifically, the interventional catheter unit 300 is the core component for entering the body to perform ablation, including a handle 310, a tube shaft 320, a balloon 330, an ultrasonic transducer 331, an overflow structure 333, a pressure sensor 334, and a temperature sensor 335.

[0049] The handle 310 is connected to the proximal end of the tube shaft 320. The handle 310 is also connected to a one-way water inlet Luer connector. A handle water inlet chamber 311 is provided inside the handle 310. The handle water inlet chamber 311 is connected to the Luer connector. The balloon 330 is connected to the distal end of the tube shaft 320. The Luer connector is used to unidirectionally deliver coolant 400 into the handle water inlet chamber 311 inside the tube shaft 320 and into the balloon 330 through the first cooling channel.

[0050] Temperature sensor 335 is installed on the inner wall of balloon 330. Temperature sensor 335 is located between ultrasonic transducer 331 and distal end of tube shaft 320. Electrical wire 325 of temperature sensor 335 passes through the inner cavity of tube shaft 320 and connects to ablation host 100. It is sealed together with electrical wire 325 of pressure sensor 334 and passes through wire cavity 324 of tube shaft 320 to isolate electrical channel from fluid channel, thereby reducing signal crosstalk and leakage risk. The fluid channel includes tube shaft central cavity 321 and water inlet cavity 322.

[0051] Furthermore, the proximal end of the balloon 330 is fixedly connected to the distal end of the tube shaft 320, the distal end of the balloon 330 is fixedly connected to the tip 340, the balloon 330 is connected to the water inlet chamber 322 inside the tube shaft 320, and the balloon 330 is connected to the tip outlet chamber 342 inside the tip 340.

[0052] The balloon 330 is made of low-hardness thermoplastic polyurethane elastomer (preferably TPU with a hardness of Shore 45A) through precision tubing extrusion and biaxial stretching blow molding processes, with its thickness on both sides strictly controlled between 0.060 mm and 0.070 mm. Because this polymer material exhibits highly linear and reproducible elastoplastic diameter deformation characteristics in low-pressure regions below 1 atm, the outer diameter of the balloon 330 shows a strong positive correlation with the steady-state pressure inside the balloon.

[0053] Please see Figure 3-6 As shown, specifically, a single-path, unidirectional water inlet cavity 322 is formed within the tube shaft 320. The water inlet cavity 322 is configured to allow the coolant 400 to flow through the surface of the ultrasonic transducer 331 within the inner cavity of the balloon 330, in order to (see...) Figure 7The inlet chamber 322 extends axially along the tube shaft 320. After reaching the distal end from the inlet of the proximal handle 310, it flows out from the outlet on the side wall of the tube shaft 320 at the proximal end of the ultrasonic transducer 331 and enters the inner cavity of the balloon 330. The coolant 400 flows axially along the surface of the ultrasonic transducer 331. A portion of the coolant 400 is discharged into the blood vessel from the tip outlet chamber 342, and another portion of the coolant 400 is introduced into the overflow structure 333. The ultrasonic transducer 331 performs directional convection heat transfer.

[0054] The cooling fluid inside the balloon 330 flows out in two separate streams to achieve precise pressure regulation and cooling: First cooling channel: After the coolant 400 flows through the outer wall of the ultrasonic transducer 331 in the inner cavity of the balloon 330 for heat exchange, a portion of the coolant 400 in the inner cavity of the balloon 330 is discharged into the blood vessel through the tip outlet cavity 342. Second cooling channel: Another part of the coolant 400 in the inner cavity of the balloon 330 flows into the inner cavity of the insulating tube 323 through the overflow structure 333 opened on the wall of the insulating tube 323. When flowing inside the insulating tube 323, it forces the support structure 332 to be flushed and performs secondary heat exchange on the inner wall of the ultrasonic transducer 331, realizing dual cooling of the inner and outer walls of the transducer. Then, this part of the fluid is discharged to the blood vessel through the tip center cavity 343 of the tip 340 which is bonded and connected to the insulating tube 323, thereby cooperating with the drive unit 200 to achieve dynamic balance of pressure inside the balloon 330.

[0055] Furthermore, the tube shaft 320 adopts a three-cavity tube structure with fluid and electrical isolation, including a central cavity 321 located at the center of the tube shaft, and a water inlet cavity 322 and a wire cavity 324 arranged in parallel along the circumference. The wire cavity 324 is a sealed chamber and is used to run electrical wires 325 through it, thereby achieving isolation between the fluid channel and the electrical channel in the tube shaft 320 section.

[0056] An insulating tube 323 is provided inside the central cavity 321 of the tube shaft. The insulating tube 323 extends from the proximal end to the distal end of the central cavity 321, and the outer wall of the insulating tube 323 is bonded to the inner wall of the central cavity 321. The distal end of the insulating tube 323 is fixedly connected to the tip 340, and the outer wall of the insulating tube 323 is bonded to the inner wall of the tip central cavity 343. This is used for the guide wire to pass through and as a drainage return channel for flushing the inner wall of the transducer. On the one hand, it can improve the stability of the connection between the insulating tube 323 and the central cavity 321, reduce the shaking of the insulating tube 323 inside the central cavity 321, and reduce the deviation caused by the guide wire delivery. It can also reduce the shaking of the front end of the insulating tube 323 caused by the coolant 400 flushing the insulating tube 323, thereby improving the safety of the operation.

[0057] The water inlet chamber 322 is independently responsible for unidirectionally supplying coolant 400 to the inner cavity of the balloon 330; the wire guide chamber 324 is sealed with an electrical wire 325, thereby isolating the fluid channel from the electrical channel throughout the entire tube shaft 320 section.

[0058] After the coolant 400 completes heat exchange, it enters the interior of the insulating tube 323 through the overflow structure 333, flows along the insulating tube 323 to the tip center cavity 343 of the tip 340, and is discharged into the blood vessel.

[0059] Preferably, the coolant 400 is a medical fluid that can be safely metabolized by the human body, such as physiological saline, Ringer's solution, or 5% glucose solution. As a medical coolant that can be metabolized by the human body, it can be naturally absorbed by the body after being directly discharged into the bloodstream. The total amount of coolant 400 discharged into the bloodstream in a single operation ranges from 400mL to 500mL, and the discharge flow rate ranges from 25mL / min to 45mL / min. This flow rate is lower than the conventional flow rate of intravenous infusion in humans and will not affect the patient's blood volume. The above safety and feasibility have been verified through animal experiments. The experimental results show that the physiological saline coolant 400 discharged within this flow range can be normally metabolized and absorbed by the animal body, and no adverse reactions such as dilutional hyponatremia or volume overload have occurred. To ensure safety, the ablation host 100 has a built-in cumulative flow monitoring function. When the cumulative discharge volume in a single operation reaches the preset safety threshold (600mL), the system automatically issues an early warning and reduces the pump speed or stops the pump.

[0060] In one specific embodiment, the coolant 400 is formulated with 0.9% medical saline / Ringer's solution, and is selected as a crystalline liquid isotonic with human blood plasma. After entering the blood circulation, it only increases the extracellular fluid volume and does not change the serum sodium ion concentration gradient, thus reducing the risk of dilutional hyponatremia.

[0061] Its instantaneous outflow rate, including the steady-state ablation period, is 25–45 mL / min, and the non-ablation translocation period is ≤ 2 mL / min. In routine clinical emergency care, the intravenous rapid infusion rate can reach 50–100 mL / min. The maximum instantaneous flow rate of this system, at 45 mL / min, is lower than the upper limit of acute volume tolerance for cardiac preload in healthy adults. After single-point ablation (60–90 s), the system automatically switches to a maintain-flow rate, giving the patient's kidneys and vascular bed sufficient time for volume redistribution and filtration metabolism.

[0062] The maximum total volume of coolant in a single procedure is 400 mL, with a maximum software-hardened lockout threshold of ≤600 mL. The typical actual discharge volume is 400–500 mL. The ablation unit 100 incorporates a flow integral cumulative monitoring algorithm, dynamically calculating the total cumulative fluid volume discharged into the body during a single procedure by real-time monitoring of the single-pump motor speed and running time. 500 mL of isotonic saline is equivalent to the standard dose of a standard bag of intravenous fluid in clinical practice. Due to the low flow rate during the intervals between ablation procedures (when changing positions), this 500 mL is slowly accumulated over procedures lasting 1–2 hours, reducing the burden on the body's circulatory system and kidney metabolism.

[0063] Furthermore, a support structure 332 is installed on the outer wall of the insulating tube 323 located inside the balloon 330, and the ultrasonic transducer 331 is fitted and fixed to the outer wall of the support structure 332; the ultrasonic transducer 331 is bonded and fixed to the support structure 332.

[0064] The wall of the insulating tube 323 is provided with an overflow structure 333, which is located between the ultrasonic transducer 331 and the far end of the tube shaft 320, so that the coolant 400 flowing into the insulating tube 323 can exchange heat with the support structure 332 to achieve heat exchange of the inner wall of the ultrasonic transducer 331; the overflow structure 333 includes a single overflow hole or multiple overflow holes that are not uniformly distributed in the circumferential direction on the wall of the insulating tube 323, and the overflow hole is a through hole that penetrates the wall of the insulating tube 323.

[0065] In one embodiment, the distribution density of the multiple overflow holes in the circumferential direction is positively correlated with the circumferential temperature distribution gradient of the ultrasonic transducer 331.

[0066] In another embodiment, the opening areas of the multiple overflow holes in the circumferential direction are non-uniformly arranged along the circumferential direction of the ultrasonic transducer 331 to match the non-uniform heat distribution on the transducer surface.

[0067] By placing the overflow structure 333 between the ultrasonic transducer 331 and the far end of the tube shaft 320, the coolant 400 is physically forced to flow through the transducer surface to complete heat exchange before reaching the overflow structure 333. This changes the flow of the coolant 400 from disordered diffusion to unidirectional ordered flow. The coolant 400 is forced to flow through the highest heat generation area of ​​the ultrasonic transducer 331 by the physical structure, which improves the thermal management efficiency compared to the blind convection scheme. This provides directional cooling for the ultrasonic transducer 331 and reduces the risk of thermal damage.

[0068] For example, under the same input power (8W) and the same coolant flow rate of 400 (45mL / min), the surface equilibrium temperature of the ultrasonic transducer of the present invention is 42°C, while the equilibrium temperature of the control group using the prior art near-end spray hole scheme is 57°C. The transducer surface temperature drops by 15°C, and the thermal management efficiency is improved by about 3.6 times (in terms of heat transfer coefficient).

[0069] The support structure 332 is a hollow tube with open ends. The support structure 332 is fitted onto the outer wall of the insulating tube 323. After the coolant 400 enters the insulating tube 323, it can contact the inner wall of the support structure 332 and conduct heat through the tube wall of the support structure 332. It is fixed to the insulating tube 323 by adhesive bonding. The ultrasonic transducer 331 is fixed to the support structure 332 by adhesive bonding or welding. Preferably, the support structure 332 is made of stainless steel.

[0070] The directional convection path is as follows: the coolant 400 driven by the drive unit 200 enters the balloon 330 from the inlet cavity 322 of the tube shaft 320. It is then forced by the physical structure to flow laterally across the surface of the ultrasonic transducer 331, resulting in intense convection heat transfer. Subsequently, it travels to the overflow hole between the ultrasonic transducer 331 and the distal end of the tube shaft 320, enters the interior of the insulating tube 323, and then flows along the insulating tube 323 to the tip center cavity 343 of the tip 340. Finally, it is discharged into the blood vessel through the distal end of the tip center cavity 343. This design precisely constrains the flow path of the coolant 400 to "inlet channel → surface of ultrasonic transducer 331 → overflow hole → interior of insulating tube 323 → tip center cavity 343 → blood vessel", forming a complete unidirectional directional flow and discharge path.

[0071] In particular, the coolant 400 is directly discharged into the bloodstream and absorbed by the body through natural metabolism, eliminating the need for an external circulation loop. This design simplifies the system architecture and reduces the additional flow resistance, contamination risks, and number of structural components associated with return piping in traditional solutions.

[0072] The coolant 400 flows unidirectionally into the balloon 330 and then through the insulating tube 323 and the central cavity of the tip 343 to the blood vessel, eliminating the need for an extracorporeal circulation loop. This system eliminates the need for a return water pump, return water pipeline and reservoir, reducing the number of parts in the BOM list by about 30% and lowering manufacturing costs.

[0073] Please see Figure 6 As shown, the tip 340 has an axially extending partition strip 341 inside, which divides the inner cavity of the tip 340 into two tip liquid outlet chambers 342 and a tip central chamber 343 arranged symmetrically in the circumferential direction. The proximal end of the tip liquid outlet chamber 342 communicates with the inner cavity of the balloon 330, and the distal end communicates with the blood vessel. The proximal end of the tip central chamber 343 is fixedly connected to and communicates with the insulating tube 323, and the distal end communicates with the blood vessel.

[0074] Specifically, the tip liquid outlet cavity 342 is formed by the outer cavity wall of the tip center cavity 343 and the partition strip 341 arranged radially on both sides of the outer cavity wall of the tip center cavity 343, which divides the inner cavity of the tip 340 into two D-shaped through holes (the cross-section of the through holes is similar to the letter D). The two D-shaped through holes are symmetrically arranged along the circumference of the tip 340. The tip fluid outlet cavity 342 is a fluid outlet hole that extends axially along the tip 340 and penetrates through it. The proximal end of the fluid outlet hole communicates with the inner lumen of the balloon 330, and the distal end of the fluid outlet hole communicates with a blood vessel. The central cavity 343 of the tip is a central hole that extends axially along the tip 340 and passes through it. The proximal end of the central hole is fixedly connected to the insulating tube 323, and the distal end of the central hole is connected to a blood vessel.

[0075] In this invention, the liquid outlet structure of the tip 340 is not limited to two D-shaped through holes, but can also be other shapes to achieve dual-path diversion and discharge of symmetrical through holes.

[0076] The tip center cavity 343 is sealed and bonded to the distal end of the insulating tube 323. This tip center cavity 343 not only serves as the main channel for the guidewire but, more importantly, directly communicates with the internal flow channel of the insulating tube 323. Due to the overflow structure 333, some water flows through the insulating tube 323 under pressure differential and exits from the tip center cavity 343, thus flushing away and carrying away heat from the ultrasonic transducer 331 through heat conduction. Two symmetrical tip liquid outlet cavities 342 are directly connected to the inner cavity of the balloon 330, serving as the main channel for the discharge of coolant 400 from the balloon 330. When the drive unit 200 continuously injects coolant 400 unidirectionally into the balloon 330, the coolant 400 is symmetrically discharged through these two tip liquid outlet cavities 342, ensuring that the ultrasonic transducer 331 is in a convective cooling environment. The pressure inside the balloon 330 is controlled in a closed loop through real-time feedback from the pressure sensor.

[0077] The central cavity 343 of the tip is used for the insulating tube 323 to pass through or be positioned, and it is also a channel for the return of coolant 400, ensuring the symmetry of the flow field at the far end and keeping the ultrasonic transducer 331 in a cooling environment.

[0078] The design of the tube shaft 320 with its three-lumen tube structure and the distal three-lumen tip 340 integrates fluid and electrical functions within limits, reducing the overall outer diameter of the interventional catheter unit 300.

[0079] Furthermore, the balloon 330 is made of low-hardness polymer materials such as TPU (thermoplastic polyurethane), Pebax, nylon elastomer, or polyurethane, making it a low-pressure compliant balloon capable of forming a target outer diameter in the range of 4–12 mm under steady-state pressure below 1 atm. The balloon 330 exhibits flexibility and wall-adherence under low pressure, allowing it to conform to irregular blood vessel walls.

[0080] The balloon, with a continuously adjustable outer diameter of 330 mm ranging from 4 to 12 mm, covers clinical needs from the renal artery (4 to 7 mm) to large blood vessels (8 to 12 mm).

[0081] This invention is not simply a combination of components: The first layer (control innovation): Through the closed-loop logic of "pressure sensor 334 → ablation host 100 closed-loop algorithm → drive unit 200 speed active regulation", the "single pump diameter change" is upgraded from passive pressure buildup to active volume micro compensation, realizing diameter control in the low pressure domain.

[0082] The second aspect (structural innovation): Through the physical coordination of "overflow hole between ultrasonic transducer 331 and distal end of tube shaft 320 → forced crossflow through transducer → inside insulating tube 323 → central cavity → inside blood vessel", a higher flow rate and more directional cooling effect is achieved than the traditional high pressure solution at a safe low pressure of less than 1 atm.

[0083] The third aspect (architectural innovation): After the coolant 400 completes heat exchange, it is directly discharged into the blood vessels for metabolism by the human body, eliminating the need for the external circulation loop required in the traditional solution, making it possible for a single pump to perform both diameter control and cooling functions.

[0084] Please see Figure 7 As shown, in one specific embodiment, taking renal artery desympathectomy as an example, the target vessel diameter is approximately 6.0 mm. The operator inputs the target diameter of 6.0 mm into the ablation host 100, and the ablation host 100 queries the mapping table to determine the desired pressure of approximately 0.45 atm. The drive unit 200 delivers coolant 400 at an initial pump rate of 50 mL / min. The coolant 400 enters the balloon 330 through the water inlet 322 of the tube shaft 320, flows through the surface of the ultrasonic transducer 331 in the inner cavity of the balloon 330 for directional convection heat transfer, and then enters the interior of the insulating tube 323 through the overflow hole approximately 20 mm between the ultrasonic transducer 331 and the distal end of the tube shaft 320, and is discharged into the blood vessel through the central cavity 343 of the tip. Pressure sensor 334 provides real-time feedback on the internal pressure of balloon 330. Once the actual pressure reaches 0.45 atm and stabilizes, the outer diameter of balloon 330 remains at 6.0 mm ± 0.3 mm, and the surface temperature of ultrasonic transducer 331 remains below 42°C. Ultrasonic transducer 331 emits ablation energy at 8 W, with an ablation duration of 60 s and an ablation depth of 4.5 mm.

[0085] In another specific embodiment, taking the ablation of a large blood vessel lesion as an example, the target vessel diameter is approximately 9.0 mm. The operator inputs the target diameter of 9.0 mm, and the ablation host 100 queries the mapping table to determine the desired pressure of approximately 0.72 atm. The drive unit 200 delivers coolant 400 at an initial pump rate of 80 mL / min. After the pressure sensor 334 reports that the pressure has reached 0.72 atm, the outer diameter of the balloon 330 remains at 9.0 mm ± 0.3 mm. The flow rate of coolant 400 increases accordingly, and the surface temperature of the ultrasonic transducer 331 remains below 40°C. The ultrasonic transducer 331 emits ablation energy at a power of 12 W, with an ablation duration of 90 s and an ablation depth of 6.0 mm. Throughout the entire process, the pressure inside the balloon 330 does not exceed the safety threshold of 1 atm.

[0086] In another specific embodiment, taking the need for ablation at different diameter vessel sites during the same procedure as an example, the first ablation site is a renal artery branch with a target diameter of 5.0 mm, with a desired pressure of approximately 0.35 atm; the second ablation site is the main renal artery trunk with a target diameter of 7.0 mm, with a desired pressure of approximately 0.55 atm. After completing treatment at the first ablation site, the operator inputs the new target diameter of 7.0 mm, and the system automatically re-queries the mapping table and adjusts the pump speed of the drive unit 200. The balloon 330 smoothly transitions from 5.0 mm to 7.0 mm, with a transition time of approximately 3–5 seconds, and the pressure is controlled within a safe range. This embodiment verifies that the present invention can adapt to vessels of different diameters without changing the catheter.

[0087] During the ablation process, the monitoring module continuously monitors the pressure inside balloon 330. Validation was conducted under test conditions of a 2.0m tubing length, 400ml of room temperature (25°C) saline solution, and an initial pump speed of 100 r / min. When the pressure inside balloon 330 suddenly rises to 0.95 atm (close to the 1 atm threshold), the monitoring module issues a warning signal and automatically reduces the pump speed of drive unit 200. If the pressure continues to rise above 1.0 atm, a safety cutoff strategy is immediately triggered: drive unit 200 reverses and stops within 35ms, with a total response time of 45ms–65ms. The power of ultrasonic transducer 331 is simultaneously reduced to zero, and an audible and visual alarm is issued.

[0088] Temperature sensor 335 monitors the surface temperature of ultrasonic transducer 331. If the temperature exceeds 50°C, the system automatically increases the pump speed by 20% to enhance cooling. If the temperature continues to rise, the power of ultrasonic transducer 331 is reduced. Through dual temperature and pressure monitoring and interlocking, no over-temperature (55°C) or over-pressure (1 atm) events occurred under the test conditions.

[0089] Please see Figure 8 As shown, the present invention also provides a control method for single-pump closed-loop diameter control and directional cooling, comprising the following steps: Receive the target outer diameter of the target balloon 300 and determine the desired pressure corresponding to the target outer diameter; The drive unit 200 is controlled to deliver coolant 400 to the interventional catheter unit 300. The coolant 400 exchanges heat with the outer wall and inner wall of the ultrasonic transducer 331 in the first cooling channel and the second cooling channel respectively before being discharged. The actual pressure inside the balloon 300 is obtained in real time by the pressure sensor 334. The output of the drive unit 200 is adjusted according to the comparison between the actual pressure and the desired pressure, so that the balloon 300 inflates and is maintained at the target outer diameter; When the actual pressure reaches or exceeds a preset safety threshold, a safety cutoff strategy is triggered. The safety cutoff strategy includes controlling the drive unit to slow down, stop the pump, or enter a pressure relief mode, so that the drive unit 200 slows down, stops the pump, or enters a pressure relief mode.

[0090] Specifically, the control drive unit unidirectionally delivers coolant 400 to the interventional catheter unit 200. The coolant 400 flowing into the first cooling channel flows through the inner cavity of the target balloon 300 and undergoes a first heat exchange on the surface of the ultrasound transducer 331. A portion of the coolant 400 that has undergone the first heat exchange is discharged into the blood vessel, while another portion of the coolant 400 that has undergone the first heat exchange is introduced into the second cooling channel under the pressure of the target balloon 300 to perform a second heat exchange on the inner wall of the ultrasound transducer 331, and then discharged into the blood vessel.

[0091] In this invention, the pressure relief mode is a micro-positive pressure unidirectional relief mode. When the ablation host 100 triggers the pressure relief control, it controls the drive unit 200 to stop pumping fluid into the interventional catheter unit 300 in the forward direction or reduce the pumping speed, and opens the pressure relief valve located on the handle 310 or the proximal end of the tubing. This allows the coolant 400 in the inner cavity of the balloon 330 to be released into the blood vessel through the tip 340 under the positive pressure difference between the pressure inside the balloon and the pressure inside the blood vessel. The inner cavity of the balloon 330 and the fluid outlet of the tip 340 are always kept at a micro-positive pressure state not lower than the blood pressure of the target blood vessel, so as to block the blood from being drawn back into the interventional catheter unit 300.

[0092] For the one-way drainage architecture where the distal end of the interventional catheter is directly connected to the blood vessel, this system adopts a micro-positive pressure relief mechanism to prevent blood backflow in the pressure relief control: when the pressure sensor 334 detects a sudden increase in the actual pressure inside the balloon and triggers a safety cutoff, the ablation host 100 prohibits the drive unit 200 from performing negative pressure backflow, so as to avoid generating negative pressure at the outlet of the tip fluid chamber 342 and the outlet of the tip central cavity 343, which would draw blood from the blood vessel into the insulating tube 323 or the inner cavity of the balloon 330.

[0093] The specific pressure relief process is as follows: the stepper motor of the drive unit 200 executes reverse brake electronic braking to stop within 35ms, and the normally closed micro electromagnetic pressure relief valve on the inlet side of the handle 310 is instantly de-energized and reset to release, opening the physical pressure relief path to the outside. At this time, the positive pressure difference between the fluid elastic potential energy accumulated in the compliant balloon 330 under low-pressure expansion (0.3~0.9atm) and the pressure inside the target blood vessel (usually about 0.08~0.12atm) causes the coolant 400 accumulated inside the balloon to spontaneously spray outward into the blood vessel through the tip outlet chamber 342 and the internal cavity of the insulating tube 323 to relieve pressure. The ablation unit 100 locks the pressure at the end of the pressure relief within a slightly positive pressure safety range (e.g., 0.12–0.15 atm, slightly higher than the patient’s mean arterial pressure), ensuring that during the pressure relief response of the entire process from 45 ms to 65 ms, the fluid flow direction at the distal end of the catheter outlet always remains unidirectional outward drainage or pressure balance. During the pressure relief process, the outlet maintains outward drainage, and no blood backflow phenomenon was observed (in vitro simulated vascular test, verified by high-speed imaging), which can reduce the risk of flow channel blockage related to blood backflow.

[0094] In one specific embodiment, a single-pump closed-loop diameter control and directional cooling control method is applied to the above-mentioned ultrasonic ablation system. The ultrasonic ablation system includes an ablation host 100, a drive unit 200, an interventional catheter unit 300, a balloon 330, an ultrasonic transducer 331, and a pressure sensor 334.

[0095] Please see Figure 9 As shown, taking the PID control algorithm as an example, the process is as follows: The operator inputs the target blood vessel diameter D_target through the human-machine interface, and the system queries the built-in target diameter-expected pressure mapping table to determine the expected pressure P_expected corresponding to D_target.

[0096] The pressure sensor collects the actual pressure P_actual inside the balloon in real time. The error calculation module calculates the deviation e = P_expected - P_actual.

[0097] The PID controller calculates the control output u(t) = K_p·e + K_i·∫e·dt + K_d·de / dt based on the deviation e, where K_p, K_i, and K_d are pre-tuned control parameters.

[0098] The control output u(t) is converted into a pump speed command after being limited and sent to the drive unit 200. The single pump adjusts its pump speed according to the command, thereby changing the flow rate of the coolant 400 entering the balloon.

[0099] The pressure inside balloon 330 changes accordingly, and the outer diameter D_balloon of balloon 330 approaches the target diameter D_target. The pressure sensor continues to collect the actual pressure, forming a closed-loop feedback.

[0100] The monitoring module operates independently of the closed-loop control loop, continuously monitoring the pressure signal, and triggering a safety shutdown when it detects excessive or abnormal pressure.

[0101] See Figure 10-11 As shown, the ablation host 100 adopts at least one feedback control algorithm among PI control, PID control, fuzzy control, adaptive control or model predictive control. When the actual pressure detected by the pressure sensor 334 reaches or exceeds the preset pressure limit, or when the actual pressure continues to rise within a preset time, the ablation host 100 triggers a safety cutoff, causing the drive unit 200 to slow down, stop the pump or enter a pressure relief mode.

[0102] Specifically, the ablation unit 100 has a built-in fitting function model between the target diameter and the desired pressure. The ablation unit 100 receives the temperature feedback signal from the temperature sensor 335 and reduces the ultrasonic output power, reduces the pump speed, stops the pump, or stops the ultrasonic output when the temperature exceeds a preset threshold.

[0103] The polynomial fitting function model was pre-obtained using the following offline in vitro constraint calibration method: In a constant-temperature saline environment of 37°C ± 0.5°C, the distal end of the interventional catheter unit to be calibrated was placed in a set of rigid, translucent simulated vascular constraint cannulas with inner diameters ranging from 4.0 mm to 12.0 mm (in 0.5 mm steps); a high-precision micro-infusion pump was used to inject coolant 400 into the balloon 330 at a step pressure of 0.05 atm, allowing the balloon 330 to gently and adaptively adhere to the simulated vascular inner wall; a high-precision biaxial laser diameter gauge (with a measurement resolution of 0.001 mm) was used to measure and record the actual outer diameter of each main ablation segment of the balloon 330 in real time, collecting no less than 50 sets of discrete "pressure-diameter (PD)" test data points; finally, the least squares method was used in the host computer to perform multivariate nonlinear regression fitting, constructing a third-order polynomial calibration model with the target diameter D_target (unit: mm) as the independent variable and the expected pressure P_expected (unit: atm) as the dependent variable. In this embodiment, for a TPU 45A balloon with a double-layer wall thickness of 0.065 mm, the preferred model characteristic coefficients after calibration and tuning are: α=0.0015, β=-0.0312, γ=0.3125, δ=-0.5120. This fitting function is hard-coded and stored in the non-volatile memory (Flash) of the ablation host (100) in mathematical code form.

[0104] During clinical ablation procedures, the microprocessor (e.g., a 32-bit Cortex-M4 MCU) of the ablation host 100 runs a PID control algorithm at a closed-loop control frequency of 100Hz. Every 10ms, the microprocessor reads the expected pressure P_expected corresponding to the current target diameter and calculates the deviation e(t) between it and the actual pressure P_actual. During algorithm execution, the input target diameter D... target First, the desired pressure P is converted using a fitting function. expected The error calculation module calculates the deviation e(t) = Pexpected - Pactual, and its unit is uniformly pressure unit (atm), thereby ensuring the dimensional consistency of the PID controller output u(t) when converted into pump speed command.

[0105] By dynamically adjusting the pulse frequency of the stepper motor driver in the drive unit 200 in real time, active micro-compensation of the 400 ml volume of coolant inside the balloon is achieved. Combined with in vivo animal experiments, this control mechanism can automatically overcome and compensate for transient resistance drift caused by violent pulsation of the blood vessel wall, and strictly maintain the steady-state adhesion diameter control accuracy of the balloon within ±0.5 mm.

[0106] Under in vitro constraint calibration conditions (37°C physiological saline, rigid simulated blood vessels), the deviation of the balloon outer diameter after closed-loop control was ±0.5 mm (n=10, standard deviation ≤0.15 mm); in canine in vivo experiments, the dynamic deviation was ≤±0.7 mm due to the influence of respiration and heartbeat.

[0107] The experimental animals were healthy adult dogs (weighing approximately 20-25 kg). Under the same input power (8 W) and flow rate (45 mL / min), the surface equilibrium temperature of the transducer of this invention was 42°C, while that of the control group (proximal spray orifice scheme) was 57°C, with a temperature drop of 15°C and a diameter control accuracy of ±0.5 mm. Physiological saline was continuously perfused into the femoral vein at a flow rate of 45 mL / min. Central venous pressure, serum sodium ion concentration, and hourly urine output were continuously monitored. The results showed that the change in serum sodium ion concentration after perfusion did not exceed ±2 mmol / L, and the increase in central venous pressure did not exceed 3 cmH2O. The blood volume of the animals recovered to the baseline level within 24 hours after the end of perfusion, and there were no significant changes in renal function indicators (BUN, Cr).

[0108] Please see Figure 12 The figure shows a comparison between the present invention and existing technical solutions in terms of the relationship between the diameter of the balloon 330 and the working pressure.

[0109] To ensure the stable expansion of the compliant balloon 330 under low pressure (below 1.0 atm, preferably 0.3-0.9 atm, approximately 30.4-91.2 kPa) and guarantee the convective cooling effect of the transducer region; The inner diameter of the insulating tube 323 is 0.35-0.55mm (preferably 0.46mm); The axial distance between the overflow structure 333 and the support structure 332 is 10-30 mm, preferably about 20 mm; The overflow hole diameter in the overflow structure 333 is 0.08-0.30mm, preferably 0.15mm. Through fluid dynamics simulation and experimental verification, within the working pressure range of 0.3 to 0.9 atm, an overflow hole diameter of 0.15mm can achieve the optimal balance between the pressure build-up inside the balloon and the coolant flow rate. The hydraulic equivalent diameter (or single cavity radial height / lateral width) of the two tip outlet chambers 342 of the tip 340 is independently 0.08-0.30 mm, preferably 0.18 mm.

[0110] The selection of the above-mentioned dimensional parameters needs to balance the pressure build-up within the balloon 330 and the flow rate of the coolant 400. If the inner diameter of the insulating tube 323 is too large or the overflow orifice diameter is too large, the resistance of the second cooling channel will be too small, making it difficult for the pressure inside the balloon 330 to build up to the target value. Conversely, if the dimensions are too small, the flow rate of the coolant 400 will be too high, resulting in a sharp increase in pressure drop, which will not only increase the load on the drive unit 200 but may also lead to uncontrolled pressure build-up within the balloon 330. This application has successfully achieved a balance between controllable pressure and heat dissipation below 1 atm through the above-mentioned proportions.

[0111] The horizontal axis represents the internal pressure (atm) of the balloon 330, ranging from 0 to 10 atm; the vertical axis represents the outer diameter (mm) of the balloon 330, ranging from 0 to 14 mm.

[0112] The curve (solid line) of this invention shows that as the pressure increases from 0 to 1.0 atm, the outer diameter of the balloon 330 smoothly increases from approximately 3 mm (folded state) to approximately 12 mm (maximum inflated state). Within the working pressure range of 0.3 to 0.9 atm, the outer diameter of the balloon 330 covers the clinical requirement range of 4 to 12 mm.

[0113] In the traditional high-pressure scheme curve (dashed line), the outer diameter of the balloon 330 remains almost unchanged as the pressure rises from 0 to 3 atm (due to the high rigidity of the balloon material). The balloon 330 only begins to inflate after the pressure exceeds 3 atm, reaching an outer diameter range of 4 to 12 mm within the pressure range of 3 to 10 atm.

[0114] The safe pressure limit P_max = 1.0 atm is marked by a vertical dashed line in the figure. The working range of this invention is located to the left of P_max (safe zone), while the working range of the conventional solution is located to the right of P_max (high pressure danger zone).

[0115] The typical working point for renal artery ablation (D=4~7mm, P=0.3~0.6atm) is also marked in the figure with shaded areas.

[0116] In this design, the balloon operates at a pressure below 1.0 atmospheres across its entire size range. When the balloon is compressed from 4mm to 12mm, the pressure increases only gradually from 0.2 atm to 0.95 atm, a gentle increase. In contrast, existing technologies show a significant pressure difference, with pressure soaring from 2.0 atm to 6.0 atm for the same size range. The steady-state operating pressure of the balloon in this design is 0.3–0.9 atm, lower than existing high-pressure designs (3–10 atm). In vitro vascular tensile tests show that the vascular wall stress at 0.9 atm is approximately 72% lower than at 3 atm, reducing the mechanical risk of vascular dissection.

[0117] According to in vitro porcine renal artery tensile tests (n=6, specimen length 10 mm, radial loading), the circumferential stress of the vessel wall was 0.32 MPa under an internal pressure of 0.9 atm and 1.14 MPa under an internal pressure of 3 atm, with a stress ratio of 0.28 (i.e., a reduction of about 72%). This data suggests that lower pressure can reduce the mechanical risks caused by excessive expansion of the vessel wall.

[0118] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art and related fields based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described and explained in the present invention, unless otherwise specified or limited, shall be implemented according to conventional means in the art.

Claims

1. An ultrasonic ablation catheter with single-pump closed-loop diameter control and directional cooling, characterized in that, It includes an ablation host (100), a drive unit (200) electrically connected to the ablation host (100), and an interventional catheter unit (300) connected to the drive unit (200); the drive unit (200) is used to pump coolant (400) into the interventional catheter unit (300); The interventional catheter unit (300) includes a handle (310), a tube shaft (320) connected to the handle (310), a balloon (330) fixed to the distal end of the tube shaft (320), a tip (340) fixed to the distal end of the balloon (330), and an ultrasound transducer (331) disposed in the balloon (330). The interventional catheter unit (300) is provided with a first cooling channel. The first cooling channel is supplied with coolant (400) by the drive unit (200) through the pipeline. The coolant (400) is used to inflate the balloon (330) and to perform initial heat exchange on the outer wall of the ultrasonic transducer (331). A portion of the coolant (400) after heat exchange is discharged from the tip (340). It also includes a second cooling channel, where another portion of the coolant (400) after heat exchange in the first cooling channel enters the channel under the pressure of the balloon (330), and after secondary heat exchange on the inner wall of the ultrasonic transducer (331), it is discharged from the tip (340).

2. The ultrasonic ablation catheter according to claim 1, characterized in that, The first cooling channel includes a handle water inlet chamber (311) disposed in the handle (310), a water inlet chamber (322) disposed in the tube shaft (320), the inner cavity of the balloon (330), and a tip liquid outlet chamber (342) disposed in the tip (340) in sequence. The handle water inlet chamber (311) is connected to the drive unit (200) through a pipeline. The drive unit (200) drives the coolant (400) to enter the handle water inlet chamber (311). After entering the inner cavity of the balloon (330) through the water inlet chamber (322), a portion of the coolant (400) is discharged from the tip liquid outlet chamber (342).

3. The ultrasonic ablation catheter according to claim 2, characterized in that, The second cooling channel includes the inner cavity of the balloon (330), the overflow structure (333), the inner cavity of the insulating tube (323), and the tip center cavity (343) disposed in the tip (340) in sequence. Another portion of the coolant (400) in the second cooling channel flows from the inner cavity of the balloon (330) through the overflow structure (333) into the inner cavity of the insulating tube (323), and then is discharged from the central cavity of the tip (343).

4. The ultrasonic ablation catheter according to claim 3, characterized in that, The insulating tube (323) is inserted inside the tube shaft (320), and the distal end of the insulating tube (323) is fixedly connected to the tip (340) and communicates with the central cavity (343) of the tip. An insulating tube (323) located inside the balloon (330) has a support structure (332) installed on its outer wall, and the ultrasonic transducer (331) is fitted and fixed to the outer wall of the support structure (332). The overflow structure (333) is disposed on the insulating tube (323) and located between the ultrasonic transducer (331) and the far end of the tube shaft (320). The coolant (400) introduced into the insulating tube (323) through the overflow structure (333) heats the support structure (332) to achieve secondary heat exchange on the inner wall of the ultrasonic transducer (331).

5. The ultrasonic ablation catheter according to claim 4, characterized in that, The overflow structure (333) includes a single overflow hole penetrating the wall of the insulating tube (323), or multiple overflow holes that are not uniformly distributed in the circumferential direction.

6. The ultrasonic ablation catheter according to claim 3, characterized in that, The tip (340) is provided with an axially extending partition (341), which divides the inner cavity of the tip (340) into two tip liquid outlet chambers (342) and a tip central chamber (343) arranged symmetrically in the circumferential direction. The proximal end of the tip liquid outlet chamber (342) is connected to the inner cavity of the balloon (330); the proximal end of the tip central chamber (343) is fixedly connected to and connected to the insulating tube (323).

7. The ultrasonic ablation catheter according to claim 1, characterized in that, The balloon (330) is equipped with a pressure sensor (334) electrically connected to the ablation host (100). The pressure sensor (334) is used to detect the actual pressure inside the balloon (330) and transmit the pressure signal to the ablation host (100). The balloon (330) is a low-pressure compliant balloon. The ablation host (100) determines the desired pressure based on the target outer diameter and adjusts the infusion parameters of the drive unit (200) based on the deviation between the desired pressure and the actual pressure, so that the balloon (330) inflates and remains at the target outer diameter. The pressure sensor (334) is a high-frequency piezoresistive miniature medical pressure sensor; the steady-state working pressure of the balloon (330) is 0.3 to 0.9 atm; the preset safety pressure threshold set by the ablation host (100) is 1 atm.

8. The ultrasonic ablation catheter according to claim 1, characterized in that, The inlet of the drive unit (200) is connected to the storage device of coolant (400) through a pipeline, and the outlet of the drive unit (200) is connected to the handle water inlet chamber (311) through a pipeline. The drive unit (200) delivers the coolant (400) in the storage device to the handle water inlet chamber (311). The drive unit (200) is a single pump, which is selected from any one of a peristaltic pump, a plunger pump, a diaphragm pump, or a micro liquid pump.

9. The ultrasonic ablation catheter according to claim 1 or 2, characterized in that, The tube shaft (320) has a three-cavity structure, including a central cavity (321), a water inlet cavity (322), and a sealed conductor cavity (324); the conductor cavity (324) is used to run electrical conductors (325) to achieve isolation between the fluid channel and the electrical channel.

10. A control method for an ultrasonic ablation catheter with single-pump closed-loop diameter control and directional cooling as described in any one of claims 1-9, characterized in that, Includes the following steps: Receive the target outer diameter of the target balloon and determine the desired pressure corresponding to the target outer diameter; The drive unit is controlled to deliver coolant to the interventional catheter unit. The coolant exchanges heat with the outer and inner walls of the ultrasonic transducer in the first and second cooling channels respectively before being discharged. The actual pressure inside the balloon is obtained in real time through the pressure sensor. The output of the drive unit is adjusted based on the comparison between the actual pressure and the desired pressure, so that the balloon inflates and remains at the target outer diameter; When the actual pressure reaches or exceeds a preset safety threshold, a safety cutoff strategy is triggered. The safety cutoff strategy includes controlling the drive unit to slow down, stop the pump, or enter a pressure relief mode.

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