Cryogenic catheter

Abstract

Disclosed in the present application is a cryogenic catheter. The cryogenic catheter comprises a catheter body and a cryogenic unit. The proximal end of the catheter body is connected to a cold source connector. The distal end of the catheter body is connected to the proximal end of the cryogenic unit. An air inlet passage and an air return passage are arranged in the catheter body. The distal ends of the air inlet passage and the air return passage are in communication with the cryogenic unit. The proximal ends of the air inlet passage and the air return passage are in communication with the cold source connector. One or more throttling mechanisms are arranged in the air inlet passage. The cryogenic catheter effectively solves the problems that a single-stage throttling cryogenic catheter is large in diameter and difficult to operate, the cryogen pressure before and after throttling in the cryogenic unit is high, the safety risk exists, the therapeutic temperature is unstable, and the like.

Description

A freezing catheter Technical Field

[0001] The present application relates to the technical field of medical equipment, and in particular to a cryocatheter for cryotherapy. Background Art

[0002] In recent years, cryotherapy technology has made great progress in the treatment of human diseases. Low-temperature surgical instruments, such as cryotherapy equipment, can be used in different departments such as oncology, interventional medicine, orthopedics, general surgery, dermatology, thoracic surgery, otolaryngology, obstetrics and gynecology, urology, and neurology to perform low-temperature cryosurgical treatment on lesion tissues. For example, it can be used to treat certain forms of arrhythmias such as atrial fibrillation (AF), ablate tumors in cancer treatment, and be used for skin diseases, obstetric surgery, bronchial biopsy, etc. Cryotherapy technology has low trauma, few complications, and patients feel little pain during treatment. It is currently a relatively mature treatment method in clinical practice. In modern science and technology, when using cryotherapy technology to kill / extract abnormal tissue, the commonly used cooling principle is mainly the Joule-Thomson effect. Different types of cryotherapy instruments have been developed based on this principle. For example, the cryoablation method and system for treating atrial fibrillation (AF) disclosed in patent number CN 106687058 B utilizes temperature control of a heat treatment element of a medical device to maintain the temperature of the cryoablation fluid within a range of -20°C and -25°C for a period of time between 2 seconds and 40 seconds, thereby extending the melting period of the cryoablation procedure.

[0003] While this patent offers some improvements in treating atrial fibrillation by extending the fluid's thawing period compared to previous technologies, effective treatment of various diseases using this technology remains challenging in actual clinical practice. Analysis revealed that during each cryotherapy session, the refrigerant gas undergoes primary throttling within the cryotube, particularly at the tip. This evaporation absorbs heat, removes tissue heat, lowers the temperature of the target treatment area, and destroys abnormal tissue, thus achieving the cryotherapy goal. However, the primary throttling employed in existing technologies presents the following four drawbacks.

[0004] 1. It cannot provide a sufficiently low cryotherapy temperature. It is known in the art that the lower the temperature, the shorter the dwell / treatment time required, and the shorter the dwell / treatment time, the more patient-friendly it is. Due to the limitations of the refrigerant flow rate through the probe, the refrigerant properties, and especially the energy loss during the process, the lowest cryotherapy temperature that can be achieved by existing technologies is basically fixed. How to provide a sufficiently low treatment temperature to enable cryotherapy technology to be applied to a wider variety of lesions, and how to provide a sufficiently low treatment temperature to shorten the treatment time and shorten the dwell / treatment time of the device on the patient are difficult problems existing in the technology.

[0005] Second, it cannot provide a sufficiently fast cooling rate. It is known in the art that the faster the cooling rate, the better the cryonics effect on target tissue. However, the cooling rate achievable with a single-stage throttling system is limited. To improve the cryonics effect, increasing the number of freezes and freezing time or lowering the freezing temperature is generally employed. However, increasing the number of freezes and freezing time correspondingly increases the risk of cryodamage to normal tissue. Lowering the freezing temperature is, in turn, limited by the theoretical limits of a single-stage throttling system.

[0006] Third, the excessively large diameter of cryo-catheters limits the permeability of catheter-based interventional treatments. Due to the varying anatomical structures of different blood vessels, respiratory tracts, and digestive tracts, different diameters of interventional catheters are suitable. The minimum diameter of some instrument channels, such as those in the bronchi and coronary arteries, is only approximately 1 mm, placing extremely stringent requirements on the diameter of interventional cryo-catheters. Using existing technology, it has proven difficult to simultaneously provide a small cryo-catheter with sufficient cooling capacity.

[0007] Fourth, the pressure at the end of the probe entering the body is too high, posing safety risks and technical limitations. Existing technology uses single-stage throttling to maintain a high pressure differential before and after throttling, which can produce lower freezing temperatures. However, excessive refrigerant pressure entering the probe poses a significant safety risk. To address this issue, most foreign companies use high-pressure balloons. However, due to material and processing precision issues, high-pressure balloon technology is primarily monopolized by multinational corporations, temporarily limiting breakthroughs in this field for domestic medical device companies.

[0008] Fifth, a single device cannot provide a wide range of cryotherapy temperatures. Existing technologies rarely achieve multifunctionality with a single device. This is because different temperatures are suitable for treating different lesions. For example, the cryotherapy temperature range for atrial fibrillation treatment is generally -40°C to -50°C, while the cryotherapy temperature range for tumor treatment is much lower, generally -40°C to -196°C. Existing technology generally uses the same cryotherapy device for the same lesion. The fundamental reason is that the system's cryotherapy temperature cannot be precisely adjusted. This phenomenon results in a significant waste of resources and creates unnecessary difficulties for medical staff in learning how to use it.

[0009] Based on the above-mentioned deficiencies in the prior art, the problem to be solved by this application is:

[0010] 1. How to achieve lower treatment temperatures and faster cooling rates, shorten treatment time, and reduce surgical risks;

[0011] 2. How to provide a high-energy, small-diameter cryocatheter to treat lesions in special locations?

[0012] 3. How to provide a solution that can reduce the high refrigerant pressure problem in existing refrigeration units, even allowing for the use of low-pressure balloons, reducing surgical risks, and breaking through technical barriers?

[0013] 4. How to provide a wide range of adjustable cryotherapy temperatures to enable cryotherapy of different lesions with the same device. Summary of the Invention

[0014] The purpose of the present application is to provide a freezing catheter in response to the deficiencies of the prior art. The implementation scheme of the present application to solve the problems of the prior art is to adopt multi-stage throttling, with a number of throttling stages. In actual operation, by adjusting the coordination relationship between the throttling stages, the cooling capacity, working temperature and cooling rate are controlled, thereby controlling the freezing depth of the lesion tissue and minimizing the amount of refrigerant fluid required. This solution effectively reduces the diameter of the freezing catheter, reduces the internal pressure of the freezing catheter, avoids operational difficulties, and avoids high refrigerant pressure before and after throttling in the freezing unit, safety risks, unstable treatment temperature and other problems.

[0015] In order to solve the problems existing in the prior art, the purpose of this application is achieved through the following technical solutions:

[0016] A freezing catheter comprises a tube body and a freezing unit, wherein the proximal end of the tube body is connected to a cold source joint, and the distal end of the tube body is connected to the proximal end of the freezing unit; an air intake passage and an air return passage are provided in the tube body; the distal ends of the air intake passage and the air return passage are in communication with the freezing unit, and the proximal ends of the air intake passage and the air return passage are in communication with the cold source joint; and one or more throttling mechanisms are provided in the air intake passage.

[0017] The purpose of this application can be further achieved through the following technical solutions:

[0018] In one embodiment, after the refrigerant fluid in the freezing pipe passes through the throttling mechanism provided in the air inlet passage and completes the last throttling, the ratio of the cooling capacity obtained by the multi-stage throttling of the freezing pipe to the cooling capacity obtained by the traditional single-stage throttling conforms to the following formula:

[0019] in: is the cooling capacity ratio, f(P t0 ,T to ) is the energy value of the fluid after single-stage throttling of the conduit, f(P tn ,T tn ) is the energy value of the fluid after passing through the multi-stage throttling of the entire freezing pipe; f(P E ,T E ) is the energy value of the refrigerant multi-stage throttling expansion to absorb heat to saturation state, f(P F ,T F ) is the energy value of the refrigerant absorbing heat to saturation state during single-stage throttling expansion.

[0020] In one embodiment, the throttle mechanism is provided at a proximal portion of the intake passage.

[0021] In one embodiment, when the number of the throttling mechanism is one, the freezing catheter is a secondary throttling freezing catheter.

[0022] In one embodiment, when the number of the throttling mechanisms is two or more, the freezing catheter is a freezing catheter with three or more stages of throttling.

[0023] In one embodiment, the throttling mechanism is a combination of one or more of a throttling valve, a capillary tube, a reducing tube, an orifice plate or a nozzle.

[0024] In one embodiment, the number of multi-stage throttling stages of the freezing conduit is determined by the fluid state (temperature, pressure, etc.) generated after each stage of the multi-stage throttling and the total cooling capacity Q that can be generated after the multi-stage throttling. The maximum cooling capacity Q that can be generated by the fluid after the multi-stage throttling is t It can be expressed as follows:

[0025] Among them, △H is the enthalpy change of the fluid before and after each stage of throttling, f(P x ,T x ), f(P tx ,T tx ) are the energy values ​​of the fluid before and after the xth throttling respectively; T t and P t are the final fluid temperature and pressure after multi-stage throttling; T x 、T tx and P x 、P tx are the fluid temperature and pressure before and after the xth stage throttling respectively; c p is the specific heat capacity of the fluid at constant pressure, v is the specific volume of the fluid;

[0026] Final fluid temperature after multi-stage throttling T t It can be expressed as: t =Φ -1 (Q t ,P t )

[0027] When the total cooling capacity Q generated by multi-stage throttling is not less than Q t , after multi-stage throttling, the fluid temperature does not exceed T t , the throttling levels selected by the system meet the requirements.

[0028] In one embodiment, the air inlet passage of the freezing catheter is provided with one or more pre-cooling mechanisms.

[0029] In a preferred embodiment, the pre-cooling mechanism is connected to a cold supply module, and the pre-cooling temperature of the pre-cooling mechanism is adjustable.

[0030] In a preferred embodiment, the pre-cooling mechanism is a heat exchanger, and the heat exchanger includes at least one of a downstream heat exchanger, a countercurrent heat exchanger, a fin heat exchanger, a shell and tube heat exchanger, and an immersion heat exchanger.

[0031] In a preferred embodiment, the cold supply module includes at least one of a micro semiconductor refrigeration pre-cooling module, a cold storage pre-cooling module, a throttling pre-cooling module, and a phase change pre-cooling module.

[0032] In a preferred embodiment, the cooling capacity of the cooling supply module of the freezing pipe conforms to the following formula:

[0033] Among them, w is the cooling capacity supplied to the module of each stage of pre-cooling mechanism, f is the thermal efficiency of each stage of pre-cooling mechanism, and △u is the pre-cooling capacity of the refrigerant supplied by each stage of pre-cooling mechanism.

[0034] In a preferred embodiment, the number of the pre-cooling mechanisms is one more than the number of the throttling mechanisms.

[0035] In a preferred embodiment, the pre-cooling amount of the refrigerant supplied by the pre-cooling mechanism is less than the critical pre-cooling amount of the refrigerant phase change: Δu1=q m [f(P1,T1)-f(P0,T0)]<Δu0

[0036] Among them, △u1 is the pre-cooling capacity of the refrigerant supplied by the first-level pre-cooling mechanism, △u0 is the critical pre-cooling capacity of the refrigerant phase change, q m is the fluid mass flow rate, f(P1, T1) and f(P0, T0) are the energy values ​​of the refrigerant before and after passing through the first-stage precooling mechanism.

[0037] In one embodiment, the dryness of the refrigerant before and after the multi-stage throttling meets the following relationship: 0≤X(P tn , T tn )<X(P t0 , T t0 )

[0038] Where: X(P t0 , T t0 ) is the dryness of the refrigerant after throttling in the single-stage throttling refrigeration pipe, X(P tn ,T tn ) is the refrigerant dryness after throttling by the final throttling mechanism in a multi-stage (n>1) throttling refrigeration pipe. Through the rational configuration of multi-stage throttling and pre-cooling mechanisms, the refrigerant dryness after throttling by the final throttling mechanism can be significantly reduced. The resulting liquid refrigerant entering the refrigeration unit absorbs significantly more heat through vaporization, thereby increasing the refrigeration capacity of the refrigeration pipe.

[0039] In one embodiment, one or more temperature and pressure sensing elements are provided in the air inlet passage of the cryocatheter, and the temperature and pressure sensing elements are connected to the human-computer interaction module and the cryotherapy device via electrical signals so that the operator can monitor and / or control the temperature and / or pressure in the treatment area.

[0040] In one embodiment, a rewarming heating element is provided on the freezing unit of the freezing catheter.

[0041] In one embodiment, the cryocatheter is one of a cryoprobe, a cryoablation catheter, or a cryoballoon.

[0042] In one embodiment, the freezing unit is a round-head-shaped, needle-shaped, ellipsoidal-shaped, or spherical-shaped metal and / or polymer material, or a combination of these.

[0043] In one embodiment, a cold storage cavity is provided in the lumen of the freezing catheter, the cold storage cavity is sleeved outside the pre-cooling mechanism, and antifreeze cold storage liquid is filled in the cold storage cavity.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. The prior art completes a single throttling by releasing the refrigerant within the freezing unit. By evaporating and absorbing heat, the heat of the tissue is removed, the temperature of the target treatment area is lowered, and abnormal cell tissue is destroyed, thereby achieving the treatment purpose. Unlike the prior art, the embodiment of the present application adopts multi-stage throttling. One or more throttling structures are configured in the air inlet passage of the freezing catheter, and the number of throttling stages is several. The high-pressure cooling medium for cryotherapy flows through several throttling mechanisms arranged on the pipeline in sequence. Each throttling mechanism causes the high-pressure cooling medium to undergo a pressure drop and temperature drop process, achieving a step-by-step cooling and pressure reduction of the high-pressure cooling medium, completing multi-stage throttling, and finally reaching the freezing unit. The final throttling is completed in the freezing unit, and cryotherapy is achieved at a lower pressure, thereby achieving the treatment purpose. Multi-stage throttling can improve the cooling efficiency, achieve a faster cooling rate and a lower cryotherapy working temperature, and increase the cryoablation range, which greatly increases the rate of tissue or cell cryogenic killing and the effective cryoablation range.

[0046] 2. The cryotherapy catheter described in this application can select the appropriate throttling level and cryotherapy temperature based on the actual lesion treatment needs. The cryotherapy catheter of this application is also equipped with a pre-cooling mechanism. Through multi-stage throttling and pre-cooling, the enthalpy difference between the refrigerant before and after throttling of the cryotherapy unit is increased, further reducing the cryotherapy temperature. Even if the diameter of the cryotherapy catheter tube is reduced, the required temperature and cooling capacity for cryotherapy can still be achieved, which can meet the needs of cryotherapy of lesions in confined areas. At the same time, during treatment, by adjusting the coordination between the throttling levels, the cooling capacity of the refrigerant carrier and the treatment temperature at the end of the cryotherapy unit are controlled, thereby controlling the freezing depth of the lesion tissue and minimizing the amount of refrigerant fluid required. In addition, the use of multi-stage throttling can reduce the refrigerant temperature and pressure before and after throttling of the cryotherapy unit, accelerating the cooling rate and enabling the probe to be used with a low-pressure cryoballoon. This application can reduce the temperature variation at the end of the cryotherapy unit, achieve stable and accurate cryotherapy temperature control, and improve the treatment effect of the equipment and surgical safety.

[0047] 3. The present application configures several rewarming heating elements in the freezing unit of the freezing catheter, which can accelerate the rewarming rate and improve the efficiency of freezing injury. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] FIG1 is a schematic structural diagram of a first embodiment of a multi-stage throttling freezing catheter of the present application.

[0049] FIG2 is a schematic diagram showing the evolution of the medium in the pressure-enthalpy diagram during the three-stage throttling process of this application.

[0050] FIG3 is a schematic structural diagram of a second embodiment of a multi-stage throttling freezing catheter of the present application.

[0051] FIG4 is a schematic diagram showing the evolution of the refrigerant medium in the pressure-enthalpy diagram during the throttling process of the multi-stage throttling refrigerant pipe shown in FIG3 .

[0052] FIG5 is a theoretical model for calculating the temperature of the medium after throttling in the multi-stage throttling process of the present application.

[0053] FIG6 is a schematic structural diagram of a third embodiment of a multi-stage throttling freezing catheter of the present application.

[0054] FIG7 is a schematic diagram showing the evolution of the refrigerant medium in the pressure-enthalpy diagram during the throttling process of the multi-stage throttling refrigerant pipe shown in FIG6 .

[0055] FIG8 is a schematic structural diagram of a fourth embodiment of a multi-stage throttling freezing catheter of the present application. DETAILED DESCRIPTION

[0056] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the present application belongs.

[0057] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "comprising" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations;

[0058] For ease of description, the words "upper," "lower," "left," and "right" appearing in this application merely indicate the same orientation as in the accompanying drawings and do not limit the structure. These are intended solely to facilitate and simplify the description of this application and are not intended to indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting this application. The "proximal end" described in this application refers to the end closest to the operator, and the "distal end" refers to the end farther from the operator.

[0059] The following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments, and cannot be used to limit the scope of the present application.

[0060] This application absorbs heat through the evaporation of the refrigerant, takes away the heat from the tissue, rapidly reduces the temperature of the target treatment site, and destroys the abnormal cell tissue, thereby achieving the treatment purpose. Its basic treatment principle is consistent with the principle of the existing technology. The innovation of this application is the use of multi-stage throttling, and one or more throttling mechanisms are set in the air inlet passage of the freezing catheter, and the number of throttling levels is several levels. Different from the existing technology, the refrigerant gas of this application passes through several throttling mechanisms in sequence to complete multi-stage throttling, and finally reaches the freezing unit, and completes the last throttling in the freezing unit. In the multi-stage throttling process, this application can optionally configure several pre-cooling mechanisms to further supplement the energy of the cryotherapy system, so that the freezing unit can obtain the optimal cooling output and treatment effect during cryotherapy. Compared with the prior art, the present application can select the appropriate throttling level and cryotherapy temperature according to the actual needs of lesion treatment, and increase the enthalpy difference before and after the refrigerant in the freezing unit of the cryotherapy catheter is vaporized by multi-stage throttling and pre-cooling. When the freezing cooling capacity required for the lesion is certain, even if the diameter of the freezing catheter tube body is reduced, the temperature and cooling capacity required for cryotherapy can still be achieved. During the treatment procedure, by adjusting the coordination relationship between the throttling levels and controlling the cooling capacity of the refrigerant carrier, the treatment temperature at the end of the freezing unit can be controlled, thereby controlling the freezing depth of the lesion tissue and minimizing the amount of refrigerant fluid required. The present application adopts multi-stage throttling to reduce the refrigerant temperature and pressure before throttling in the freezing unit, speeding up the cooling rate, so it can be used in conjunction with a low-pressure balloon, reducing surgical risks, and breaking through the foreign technical monopoly restrictions on high-pressure balloons.

[0061] The present application is described in detail below through some embodiments of a multi-stage throttling freezing catheter.

[0062] Example 1

[0063] Referring to FIG1 , a freezing catheter comprises a tube body 302 and a freezing unit 304. The proximal end of the tube body 302 is connected to a cold source connector 301, and the distal end of the tube body 302 is connected to the proximal end of the freezing unit 304. An air inlet passage 330 and an air return passage 328 are provided in the tube body 302. The distal ends of the air inlet passage 330 and the air return passage 328 are in communication with the freezing unit 304, and the proximal end of the air inlet passage 330 is in communication with the cold source connector 301. The air return passage 328 is in communication with the freezing unit 304. A waste gas outlet 307 is provided at the proximal end of the air passage 328, and the waste gas outlet 307 is connected to the waste gas recovery system or communicated with the atmosphere. The freezing catheter is mechanically connected to the cryotherapy equipment through the cold source connector 301. A first throttling mechanism 319 is provided in the air intake passage 330. The first throttling mechanism 319 is arranged in the air intake passage 330 near the cold source connector 301. The first throttling mechanism 319 and the freezing unit 304 together constitute a two-stage throttling freezing catheter.

[0064] During cryotherapy, the air inlet passage 330 serves as the refrigerant supply lumen. The refrigerant can be one of CO2, N20, Freon, nitrogen, or argon. The refrigerant originates from the cryotherapy device and enters the cryotube through the inlet of the cold source connector 301. It flows axially along the lumen of the air inlet passage 330, sequentially passing through the first throttling mechanism 319, forming the first stage of throttling. It then flows through the gas nozzle 317 within the cryotherapy unit 304, forming the second stage of throttling. The refrigerant vaporizes within the expansion chamber of the cryotherapy unit 304, absorbing heat and completing the cryotherapy process on the target tissue. The vaporized refrigerant passes through the return air port 324 within the cryotherapy unit 304, enters the return air passage 328, and reaches the exhaust outlet 307, where it is discharged to the exhaust gas recovery system. This completes a complete cryotherapy process through the second stage of throttling within the cryotube.

[0065] In one embodiment, two or more throttling mechanisms are provided within the air inlet passage 330, forming a three-stage or multi-stage throttling cryotube. Theoretically, a greater number of throttling stages results in a better final effect for the present application. However, increasing the number of throttling stages also complicates the cryotube manufacturing process. Therefore, an appropriate number of throttling stages can be selected based on the application scenario.

[0066] After the refrigerant fluid in the freezing pipe passes through the throttling mechanism provided in the air inlet passage and completes the final throttling in the freezing unit, the ratio of the cooling capacity obtained by the multi-stage throttling of the freezing pipe to the cooling capacity obtained by the traditional single-stage throttling conforms to the following formula:

[0067] in: is the cooling capacity ratio, f(P t0 , T t0 ) is the energy value of the fluid after single-stage throttling of the conduit, f(P tn , T tn ) is the energy value of the fluid after passing through the multi-stage throttling of the entire freezing pipe; f(P E ,T E ) is the energy value of the refrigerant multi-stage throttling expansion to absorb heat to saturation state, f(P F ,T F ) is the energy value of the refrigerant when it absorbs heat to saturation during single-stage throttling expansion in the refrigeration pipe.

[0068] Referring to FIG2 , when cryoablation is performed using a conventional cryoablation catheter, ideally, the refrigerant enters the freezing unit and the state before throttling is phase point 1 (P1, T1), where P and T represent the pressure and temperature in this state, respectively. After completing the first level of throttling (i.e., from 1 to 6) in the freezing unit, the refrigerant directly reaches phase point 6 (P t0 、T t0 The present application adopts multi-stage throttling. Theoretically, the refrigerant can enter the refrigeration unit of the refrigeration pipe at any pressure lower than the phase point 1. As shown in FIG2 , in the first embodiment, the refrigerant at the phase point 1 (P1, T1) is throttled to the phase point 2 (P t1 、T t1 ), and then to the refrigeration unit to complete the secondary throttling; in the second embodiment, the refrigerant at phase point 1 (P1, T1) is throttled to phase point 3 (P t2 、T t2 ), and then to the refrigeration unit to complete the secondary throttling; in the third embodiment, the refrigerant at phase point 1 (P1, T1) is throttled to phase point 2 through the first stage, throttled to phase point 3 through the second stage, and finally to the refrigeration unit of the refrigeration pipe to complete the third stage throttling. After throttling, the refrigerant reaches phase point 4 (P t3 、T t3 ). Refer to Figure 2. Compared with the prior art, the unit cooling capacity q2 of multi-stage throttling is q2>q1 compared with the unit cooling capacity q1 of single-stage throttling. The pressure after throttling P of multi-stage throttling is E Compared with the throttle pressure P after single-stage throttling F Compared to: P E <P F The multi-stage throttling method of the present application can increase the cooling capacity of the freezing unit and reduce the refrigerant pressure before and after throttling in the freezing unit. Therefore, the cryotherapy equipment can be used in conjunction with a low-pressure cryoballoon to reduce surgical risks.

[0069] If the distance between the two stages of throttling is too small, the fluid flow may be disturbed, resulting in unstable phenomena such as eddies, fluctuations or oscillations. If the distance is too large, the pipeline may be too long, the flow resistance may be too large, resulting in serious energy loss and increasing the ineffective length of the conduit. This application determines the setting of each stage of throttling mechanism based on the fluid flow rate and the required pressure drop. According to the fluid properties and process requirements, the distance and position between adjacent throttling mechanisms are determined based on calculations and experimental verification to ensure that the fluid can smoothly transition between the two stages of throttling. By combining the Bernoulli equation and the continuity equation, the flow rate after throttling can be solved. The specific calculation process needs to be determined according to the actual operating status, including known parameters such as pressure, flow rate, cross-sectional area before throttling. It should be noted that the above calculations need to be derived under certain assumptions, such as incompressible, ideal fluid, etc. In actual applications, some correction factors need to be considered, such as the compressibility of the fluid, viscosity loss, friction, etc.

[0070] The throttling stages of the freezing conduit are based on the formula of the fluid enthalpy change before and after each stage of throttling to establish a theoretical model of multi-stage throttling. Taking any point P and T of the fluid in the freezing conduit as independent variables, the enthalpy change of the specific enthalpy H=f(P,T) is:

[0071] According to the formula, dH=Tds+vdp

[0072] It can be deduced that

[0073] According to Maxwell's relations:

[0074] And the formula,

[0075] The general expression for fluid enthalpy change is derived using the equation of state and specific heat:

[0076] Since the enthalpy of the fluid in the pipe changes to △H before and after throttling, the above expressions can be used to deduce f(P1, T1) and f(P t1 ,T t1 ) Enthalpy change:

[0077] The number of multi-stage throttling stages of the freezing pipe is determined by the fluid state (e.g., temperature, pressure, etc.) generated after each stage of throttling and the total cooling capacity Q that can be generated after the multi-stage throttling. The maximum cooling capacity Q that can be generated by the fluid after the first stage of throttling is t1 It can be expressed as follows:

[0078] Among them, △H is the enthalpy change of the fluid before and after the first stage of throttling, f(P1,T1), f(Pt1 ,T t1 ) are the energy values ​​of the fluid before and after the first stage of throttling, T1, T t1 and P1, P t1 are the fluid temperature and pressure before and after the first stage of throttling respectively; c p is the specific heat capacity of the fluid at constant pressure, and v is the specific volume of the fluid.

[0079] The maximum cooling capacity Q that can be generated by the fluid after multi-stage throttling t It can be expressed as follows:

[0080] Among them, △H is the enthalpy change of the fluid before and after each stage of throttling, f(P x ,T x ), f(P tx ,T tx ) are the energy values ​​of the fluid before and after the xth throttling respectively; T t and P t are the final fluid temperature and pressure after multi-stage throttling; T x 、T tx and P x 、P tx are the fluid temperature and pressure before and after the xth stage throttling respectively; c p is the specific heat capacity of the fluid at constant pressure, and v is the specific volume of the fluid.

[0081] Final fluid temperature after multi-stage throttling T t It can be expressed as: t =Φ- 1( Q t ,P t )

[0082] When the total cooling capacity Q generated by multi-stage throttling is not less than Q t , after multi-stage throttling, the fluid temperature does not exceed T t , the throttling levels selected by the system meet the requirements.

[0083] The number of throttling stages in the cryotube was verified using a multi-stage throttling theoretical model combined with experimental testing. Calculations and experiments have shown that when multi-stage throttling is used, the distance between the center points of the two throttling mechanisms is preferably 5-100 times the maximum diameter of the pipeline. This is correlated with the structure and installation location of the throttling mechanism. The throttling mechanism can be at least one of a throttle valve, capillary tube, reducer, orifice plate, and nozzle, preferably a throttle valve.

[0084] Referring to FIG. 1 , in one embodiment, a rewarming heating element 316 is also provided on the freezing unit 304. One or more temperature and pressure sensing elements are provided within the freezing catheter. These temperature and pressure sensing elements are connected to the human-machine interface module and the cryotherapy device via electrical signals, allowing the operator to monitor and / or control the temperature and / or pressure within the treatment area. The temperature sensing element and pressure sensing element are an integrated temperature and pressure sensor 327 and a temperature and pressure sensing element 315. The temperature and pressure sensor 327 is provided at the distal end of the first throttling mechanism 319, and the temperature and pressure sensing element 315 is provided within the freezing unit 304 to monitor the temperature and pressure within the pipeline and freezing unit, and to control the fluid pressure to prevent excessive fluid pressure. The temperature sensing element may be a K-type thermocouple, a T-type thermocouple, or a patch temperature sensor. The pressure sensing element may be a pressure, piezoresistive, piezoelectric, capacitive, or electromagnetic pressure sensor. The temperature and pressure sensor is an integrated combination of the temperature sensing element and the pressure sensing element to achieve simultaneous measurement of temperature and pressure.

[0085] In practical applications, the cryo-catheter is one of a cryoprobe, a cryoablation catheter or a cryoballoon. The outer layer of the tube body 302 of the cryo-catheter is made of a heat-insulating material such as plastic or rubber.

[0086] Example 2

[0087] 3 , the structure of this embodiment is basically the same as that of the first embodiment, comprising a freezing catheter, comprising a tube body 302 and a freezing unit 304. The proximal end of the tube body 302 is connected to a cold source connector 301, and the distal end of the tube body 302 is connected to a proximal end of the freezing unit 304. An air intake passage 330 and an air return passage 328 are provided in the tube body 302. The distal ends of the air intake passage 330 and the air return passage 328 are in communication with the freezing unit 304, and the proximal end of the air intake passage 330 is in communication with the cold source connector 301. The proximal end of the air return passage 328 is provided with an exhaust gas outlet 307 connected to the atmosphere. The freezing catheter is mechanically connected to the cryotherapy device via the cold source connector 301. The difference lies in that a first throttle mechanism 319 and a second throttle mechanism 321 are disposed within the air intake passage 330. Both the first throttle mechanism 319 and the second throttle mechanism 321 are located at the proximal end of the air intake passage 330. Together with the refrigeration unit 304, these first throttle mechanism 319 and the second throttle mechanism 321 form a three-stage throttling structure. Three precooling mechanisms are also disposed at the proximal end of the air intake passage 330: a first-stage precooling mechanism 318, a second-stage precooling mechanism 320, and a third-stage precooling mechanism 322. These three precooling mechanisms are each connected to a cooling supply module 325. In this embodiment, the number of precooling mechanisms exceeds the number of throttle mechanisms by one. Therefore, the first throttle mechanism 319 and the second throttle mechanism 321, together with the first-stage precooling mechanism 318, the second-stage precooling mechanism 320, and the third-stage precooling mechanism 322, form a three-stage throttling and three-stage precooling refrigeration conduit.

[0088] As shown in Figure 3, during cryotherapy, the air inlet passage 330 serves as the refrigerant supply lumen. The refrigerant can be one of CO2, N2O, Freon, nitrogen, or argon. The refrigerant originates from the cryotherapy device described above. It enters the cryotube through the inlet of the cold source connector 301 and flows axially along the lumen of the air inlet passage 330, sequentially passing through the first-stage precooling mechanism 318 and the first throttle mechanism 319, forming a "first-stage precooling + first-stage throttling" mechanism; the second-stage precooling mechanism 320 and the second throttle mechanism 321, forming a "second-stage precooling + second-stage throttling" mechanism; the third-stage precooling mechanism 322, forming a "third-stage precooling mechanism"; and the gas nozzle 317 within the freezing unit 304, forming a "third-stage throttling mechanism." The refrigerant gas evaporates within the expansion chamber of the freezing unit 304, absorbing heat and completing the cryotherapy process for the target tissue. The evaporated refrigerant passes through return air port 324 within refrigeration unit 304, enters return air passage 328, and reaches exhaust outlet 307, where it is discharged to the atmosphere or an exhaust gas recovery system. This completes a complete cryotherapy process through a three-stage precooling and three-stage throttling process within the cryotube.

[0089] The pre-cooling mechanism can be a heat exchanger (for example, a shell and tube heat exchanger or a spiral tube heat exchanger). In this embodiment, the first-stage pre-cooling mechanism 318, the second-stage pre-cooling mechanism 320 and the third-stage pre-cooling mechanism 322 are a countercurrent heat exchanger, the main component of which is a high-conductivity heat transfer body, which can be used independently or in combination with each other. This heat exchanger can be a wire, a belt or other longitudinal body extending in the axial direction of the air inlet passage 330 and can be constructed as a short sleeve or a ring. This longitudinal heat transfer body can also follow a spiral structure, or can be arranged to extend in the axial direction of the freezing conduit. The heat exchanger also includes a downstream heat exchanger, a fin heat exchanger, an immersed heat exchanger, etc. The first-stage pre-cooling mechanism 318, the second-stage pre-cooling mechanism 320 and the third-stage pre-cooling mechanism 322 are fixed on the outer surface of the tube wall 323 of the air inlet passage 330. The energy is transmitted through the surface heat transfer body close to the tube wall 323. The energy passes through the wall thickness of the tube wall 323 and is transmitted to the refrigerant fluid in the form of heat conduction, thereby cooling the refrigerant fluid. The heat exchange between the refrigerant fluid and the heat transfer body of the pre-cooling mechanism is countercurrent heat exchange. The material of the heat transfer body of the pre-cooling mechanism and the tube wall 323 of the air inlet passage 330 is a heat-conducting material, such as copper, silver, aluminum or steel, preferably stainless steel or carbon fiber. The cooling capacity of the first-stage pre-cooling mechanism 318, the second-stage pre-cooling mechanism 320 and the third-stage pre-cooling mechanism 322 is supplied by the cooling capacity supply module 325. The cooling capacity supply module 325 can be set in the tube body 302 of the freezing catheter, and the preferred setting point is one end close to the cold source connector 301. The cooling supply module 325 includes at least one of a micro semiconductor refrigeration pre-cooling module, a cold storage pre-cooling module, a throttling pre-cooling module, and a phase change pre-cooling module.

[0090] The first throttling mechanism 319 and the second throttling mechanism 321 can be a combination of at least one or more of a throttle valve, a capillary tube, a reducer, an orifice plate, and a nozzle. The freezing unit 304 is designed as an expansion cavity structure, providing space for the refrigerant to expand and evaporate, forming a low temperature through throttling to freeze human tissue. A gas nozzle 317 and a temperature and pressure sensing element 315 are provided in the freezing unit 304. A rewarming heating element 316 is also provided at the freezing unit 304 to accelerate the rewarming rate and shorten the operation time. The freezing unit 304 can be either a freezing probe or a balloon.

[0091] As shown in FIG4 , it is assumed that the refrigerant output from the cryotherapy device is at phase point 2 (P1, T1), where P and T represent the pressure and temperature, respectively. The refrigerant completes the multi-stage "throttling + pre-cooling" process 2-3-4-5-6-7 as follows: the refrigerant is throttled by the first throttling mechanism 319 and reaches phase point 3 (P t1 、T t1); then pre-cooled by the secondary pre-cooling mechanism 320 to phase point 4 (P2, T2); then throttled by the second throttling mechanism 321 to phase point 5 (P t2 、T t2 ); then pre-cooled by the three-stage pre-cooling mechanism 322 to phase point 6 (P3, T3), and finally completed in the freezing unit 304 three-stage throttling process, after throttling to phase point 7 (P t3 、T t3 The throttled refrigerant gas in the freezing unit 304 exchanges heat with the tissue in the freezing unit 304 of the freezing catheter. During the process from phase 7 to phase 9, after absorbing heat, the energy value of the refrigerant increases and it continues to vaporize. At the same time, the refrigerant absorbs heat through evaporation, taking away the heat of the tissue, lowering the temperature of the target treatment site to form an ice ball, destroying the abnormal cell tissue. After the refrigerant absorbs heat to saturation, it reaches phase 9 (P E 、T E ), the vaporized low-pressure refrigerant gas is discharged to the waste gas recovery system or a designated location through the exhaust outlet 307 of the return gas passage 328 of the freezing pipe. At the evaporation pressure, the heat absorbed by the refrigerant is equal to the latent heat of evaporation of the refrigerant, which is the cooling capacity of the freezing pipe. As shown in the following formula: q2=f(P E ,T E )-f(P3,T3) Where, q2 is the cooling capacity released by the unit refrigerant in the freezing pipe (phase point 7-phase point 9 process), f(P3,T3) is the energy value of the refrigerant at phase point 6, f(P E ,T E ) is the energy value of the refrigerant when it expands and absorbs heat to saturation at phase point 9.

[0092] According to the embodiment of the present application, the pressure of the refrigerant entering the refrigeration unit of the refrigeration pipe is the pressure P3 of phase 6, and the pressure after throttling in the refrigeration unit is the pressure P of phase 7. t3 , the pressure difference before and after multi-stage throttling is ΔP2.

[0093] According to the laws of thermodynamics, there is no heat or work exchanged between the refrigerant before and after throttling, so the energy value remains unchanged. As shown in Figure 4, the refrigerant enters the initial phase 2 (P1, T1) of the refrigeration pipe. According to the prior art, the refrigerant is only throttled in the refrigeration unit, that is, the refrigerant is throttled directly from phase 2 (P1, T1) to phase 8 (P t0 、T t0), the entire throttling process is carried out in the freezing unit 304, without multi-stage throttling and pre-cooling auxiliary links. As shown in Figure 4, the process of the first-stage throttling of the refrigerant in the freezing catheter is a straight line from phase point 2 to phase point 8. After throttling, the refrigerant performs heat exchange in the freezing unit 304 of the freezing catheter, and the process is from phase point 8 to phase point 10. After absorbing heat, the energy value of the refrigerant increases and it continues to vaporize. The refrigerant absorbs heat through evaporation and takes away the heat of the tissue, so that the temperature of the target treatment site is reduced to form an ice ball, and the abnormal cell tissue is destroyed. After throttling and absorbing heat to saturation, the refrigerant reaches phase point 10 (P F 、T F ).

[0094] Referring to FIG4 , the cryoablation treatment process of the prior art is a process of the first-order throttling phase point 2-8-10. Under the evaporation pressure, the heat absorption of the refrigerant is equal to the latent heat of evaporation of the refrigerant, which is equal to the cooling capacity of the cryotube. The cooling capacity of the prior art cryotube is as follows: q1=f(P F ,T F )-f(P t0 ,T t0 )

[0095] Among them, q1 is the cooling capacity released by the unit refrigerant in the freezing pipe (phase point 8-10 process), f(P t0 ,T t0 ) is the energy value of the refrigerant at phase point 8, f(P F ,T F ) is the energy value of the refrigerant when it expands and absorbs heat to saturation at phase point 10.

[0096] The pressure of the refrigerant entering the refrigeration unit of the refrigeration pipe is the pressure P1 of phase 2, and the pressure after throttling in the refrigeration unit is the pressure P of phase 8. t0 , the pressure difference before and after throttling is ΔP1.

[0097] As mentioned above, after the fluid undergoes three-stage throttling, the ratio of the cooling capacity obtained by the freezing pipe to the cooling capacity obtained by the traditional single-stage throttling conforms to the following formula:

[0098] in: is the cooling capacity ratio, f(P t0 ,T t0 ) is the energy value of the fluid after the first level of throttling using the existing technology, f(P t3 ,T t3 ) is the energy value of the fluid after three-stage throttling; f(P E ,T E ) is the energy value of the refrigerant multi-stage throttling expansion to absorb heat to saturation state, f(P F ,T F ) is the energy value of the refrigerant absorbed by the single-stage throttling expansion to the saturated state.

[0099] Compared with the prior art, the cryotherapy system provided by the embodiment of the present application has a significantly increased refrigeration capacity per unit refrigerant for cryotherapy compared with the prior art; the pressure P3 before throttling of the refrigerant when entering the freezing unit 304 is less than P1, and the pressure P t3 <P t0 , the pressure before and after the multi-stage throttling can be significantly reduced compared with the existing technology. According to thermodynamic calculations, under ideal conditions, by adopting the technical solution of the present application, under the same cooling demand, the diameter of the freezing catheter can be reduced compared with the existing technology. The reduction in the diameter of the freezing catheter can increase the application scope of cryotherapy technology in distal bronchial biopsy of the lungs, coronary artery dredging, etc. In addition, by adopting the technical solution of the present application, the pressure in the freezing unit is significantly reduced before and after throttling, which not only reduces the risk of surgery, but also makes the application of low-pressure balloons in the treatment of some lesions extremely feasible, breaking through the technical limitations of foreign countries on high-pressure balloon materials.

[0100] This application can establish a multi-stage throttling design theoretical model by monitoring the temperature and pressure of the refrigerant before and after throttling, and determine the appropriate throttling level of the freezing pipe based on the theoretical model. The specific implementation steps are as follows:

[0101] First, preset the freezing temperature T required for lesion treatment according to the purpose of the cryocatheter. tn , refrigeration unit allowable pre-throttling pressure P n , refrigeration unit design diameter D, calculate the fluid mass flow rate q m , the target phase point where the fluid is finally throttled in the conduit (P tn 、T tn );

[0102] Refer to Figure 5, the second step is to calculate the fluid initial phase point (P0, T0) and the target phase point (P tn 、T tn ) The number of pre-divided throttling stages is n (n>1);

[0103] The third step is to plan the phase point position before and after the fluid throttling. If a pre-cooling mechanism is required, the pre-throttling value phase point is planned at the phase point position after pre-cooling and before throttling. For example, if pre-cooling is performed before the first-stage throttling, the pre-throttling mechanism before the first-stage throttling is set according to the planned pre-throttling value phase point (P1, T1), and the cooling capacity Δu1 of the corresponding pre-cooling supply mechanism is calculated. The pre-cooling capacity of the refrigerant supplied by the pre-cooling module must be less than the critical pre-cooling capacity of the refrigerant phase change: Δu1 = q m [f(P1,T1)-f(P0,T0)]<Δu0

[0104] Among them, △u1 is the pre-cooling capacity of the refrigerant supplied by the first-level pre-cooling mechanism, △u0 is the critical pre-cooling capacity of the refrigerant phase change, qm is the fluid mass flow rate, f(P1, T1) and f(P0, T0) are the energy values ​​of the refrigerant before and after passing through the first-stage precooling mechanism;

[0105] According to the phase point before throttling (P1, T1), the phase point after throttling (P t1 、T t1 ), the enthalpy change of the fluid after the first stage of throttling can be expressed as follows:

[0106] Among them, △H is the enthalpy change of the fluid before and after throttling, f(P1, T1), f(P t1 , T t1 ) are the energy values ​​of the fluid before and after the first stage of throttling, T1, T t1 and P1, P t1 are the fluid temperature and pressure before and after the first stage of throttling respectively; c p is the specific heat capacity of the fluid at constant pressure, and v is the specific volume of the fluid.

[0107] The fourth step is to calculate the cooling capacity Δu2 of the second stage precooling mechanism and the fluid pressure P after the second stage throttling according to the theoretical model of the first stage precooling and the first stage throttling. t2 , the fluid temperature after the second stage throttling T t2 , and so on, the enthalpy change of the fluid after the x-th stage throttling can be expressed as follows:

[0108] Among them, △H is the enthalpy change of the fluid before and after throttling, f(P x , T x ), f(P tx , T tx ) are the energy values ​​of the fluid before and after the x-th stage throttling, T x 、T tx and P x 、P tx are the fluid temperature and pressure before and after the xth stage throttling respectively; c p is the specific heat capacity of the fluid at constant pressure, and v is the specific volume of the fluid.

[0109] The pre-cooling capacity of the refrigerant supplied by the x-th stage pre-cooling is: Δu x =q m [f(P x ,T x )-f(P t(x-1) ,T t(x-1) )]

[0110] The fluid phase point after all throttling of multi-stage throttling is completed is (P tn 、T tn ), the enthalpy change of the fluid after the last stage of throttling can be expressed as follows:

[0111] The pre-cooling capacity of the refrigerant supplied by the last stage of pre-cooling is: Δu n =q m [f(P n ,T n )-f(P t(n-1) ,T t(n-1) )]

[0112] Step 5: Analyze whether the precooling / throttling process reaches the critical pressure according to different throttling types, establish a safe and economical multi-stage throttling cryotherapy plan, and determine the final throttling and precooling stages, as well as the maximum precooling capacity of each stage;

[0113] The sixth step is to control and adjust the valve opening and the pre-cooling amount between each stage during the actual operation of the multi-stage throttling cryotherapy equipment through a microprocessor or controller using a PID or non-PID software algorithm, thereby controlling the actual phase point position of the refrigerant after each stage of throttling and pre-cooling to match the designed phase point position, thereby achieving precise control of the refrigerant temperature and pressure before and after each stage of throttling.

[0114] Based on the temperature and pressure changes during the multi-stage throttling process, as well as the target cryotherapy temperature, this model can accurately predict the pressure and temperature of different refrigerants under different modes, thus preventing the formation of solids during fluid throttling and precooling, which could cause ice blockage and affect the normal operation of the cryotherapy equipment. The control principle of multi-stage throttling cryotherapy equipment is to quickly supply sufficient cooling capacity to the cryotube's freezing unit while meeting the required cryotherapy temperature without ice blockage, minimize the diameter of the cryotube, minimize the pressure drop across the throttling mechanism, and reduce the precooling capacity, the number of throttling stages, and the number of precooling stages. Methods for calculating the precooling capacity of each stage and selecting the number of multi-stage throttling stages are also provided.

[0115] The present invention can reduce the dryness of the output refrigerant through multi-stage throttling and improve the refrigeration capacity of the freezing pipe. The dryness of the refrigerant in the freezing pipe after the traditional first-stage throttling and pre-cooling is X (P t0 ,T t0 )for:

[0116] Where: f x (P t0 ,T t0 ) is the phase point (P t0 、T t0 ) Actual energy value of refrigerant, f f (P t0 ,T t0 ) is the energy value of saturated liquid refrigerant; f s (P t0 ,T t0 ) is the energy value of saturated gaseous refrigerant.

[0117] The dryness of the refrigerant in the freezing pipe after multi-stage throttling and pre-cooling is X(P tn ,T tn )for:

[0118] Where: f x (P tn ,T tn ) is the phase point (P tn 、T tn ) Actual energy value of refrigerant, f f (P tn ,T tn ) is the energy value of saturated liquid refrigerant; f s (P tn ,T tn ) is the energy value of saturated gaseous refrigerant.

[0119] Therefore, the dryness of the refrigerant in the freezing pipe before and after the multi-stage throttling meets the following relationship: 0≤X(P tn ,T tn )<X(P t0 ,T t0 )

[0120] Where: X(P t0 , T t0 ) is the dryness of the refrigerant after throttling in the single-stage throttling refrigeration pipe, X(P tn ,T tn ) is the dryness of the refrigerant after it is throttled by the last stage throttling mechanism in the multi-stage throttling refrigeration pipe.

[0121] Since the dryness of the refrigerant after multi-stage throttling is significantly lower than that of the traditional single-stage throttling, the liquid content of the refrigerant after multi-stage throttling is significantly increased, and the cooling capacity of the freezing pipe will be significantly improved.

[0122] Example 3

[0123] Referring to Figure 6, this embodiment is a variation of Example 2. Unlike Figure 3, this embodiment allows the cold supply module for the primary pre-cooling mechanism 318, the secondary pre-cooling mechanism 320, and the tertiary pre-cooling mechanism 322 to be placed within the cryotherapy device, reducing the volume of the cryotherapy catheter and simplifying its manufacturing. Cold from the cold supply module is input through the pre-cooling cold source supply port C of the cold source connector 301, and is sequentially supplied along the cold source supply lumen 331 to the tertiary pre-cooling mechanism 322, the secondary pre-cooling mechanism 320, and the primary pre-cooling mechanism 318. The cold is then output through the pre-cooling cold source outlet D and returned to the cryotherapy device. Furthermore, in this embodiment, the air inlet passage 330 is the inner lumen of the air inlet pipe, and the return air pipe is sheathed outside the air inlet pipe. The cavity enclosed by the outer wall of the air inlet pipe and the inner wall of the return air pipe constitutes the return air passage 328.

[0124] The cold supply module is installed within the cryotherapy device and can be an independent refrigeration system. For example, a micro-semiconductor refrigeration module can also theoretically be a refrigeration source formed by another piping system branching from the air source in the cryotherapy device using the Joule-Thompson effect. The cold supply module, located outside the cryotube, can supply cold to the refrigerant in the air inlet passage 330 via a cold source connector 301, using a pipeline or thermoelectric element. Other common methods can be used to achieve cold supply, which will not be discussed here. This embodiment can further increase the cooling capacity of the refrigerant and extend the refrigerant's melting time.

[0125] The working process of the multi-stage throttling freezing catheter of this embodiment is as follows: the refrigerant enters the air inlet passage 330 through the refrigerant inlet A, is first cooled by the first-stage pre-cooling mechanism 318, and then passes through the first throttling mechanism 319 to complete the "first-stage pre-cooling + first-stage throttling"; then passes through the second-stage pre-cooling mechanism 320 to cool, and then passes through the second throttling mechanism 321 to complete the "second-stage pre-cooling + second-stage throttling"; then passes through the third-stage pre-cooling module 322 to complete the "third-stage pre-cooling", and finally reaches the freezing unit 304 through the gas nozzle 317 set at the far end of the air inlet passage 330 to complete the "third-stage throttling". The refrigerant absorbs heat through evaporation and completes the freezing of the tissue. The evaporated low-pressure refrigerant gas is discharged from the return port 324 through the return air passage 328 to the exhaust gas outlet B, completing a cryotherapy process.

[0126] In one embodiment, the first throttling mechanism 319 and the second throttling mechanism 321 are reducers. In an alternative embodiment, as shown in Figure 6, a cold storage chamber 332 is provided within the lumen 302 of the cryotube. The cold storage chamber 332 is sleeved onto the pre-cooling mechanism and contains an antifreeze cold storage liquid. The antifreeze cold storage liquid may be ethylene glycol, glycerol, diethylene glycol, silicate, etc., with a freezing point setting range of -10°C to -50°C. Before or during program execution, the antifreeze cold storage liquid in the cold storage chamber 332 can continue to supply cooling energy to the first-stage pre-cooling mechanism 318, the second-stage pre-cooling mechanism 320, and the third-stage pre-cooling mechanism 322, continuously cooling the refrigerant in the intake passage 330. The tube wall 323 of the intake passage 330 is made of a thermally conductive material, such as copper, silver, aluminum, or steel, particularly stainless steel or carbon fiber.

[0127] In another embodiment, the pre-cooling temperature of the pre-cooling mechanism is adjustable. Referring to FIG6 , a multi-stage throttling cooling structure is formed by the cooperation of the first-stage pre-cooling mechanism 318, the first throttling mechanism 319, the second-stage pre-cooling mechanism 320, the second throttling mechanism 321, and the third-stage pre-cooling mechanism 322. The power of the cooling supply module is adjusted by a PID or non-PID software algorithm to control the cooling power of the first-stage pre-cooling mechanism 318, the second-stage pre-cooling mechanism 320, and the third-stage pre-cooling mechanism 322, respectively, so that the refrigerant before and after throttling by the first throttling mechanism 319 and the second throttling mechanism 321 is always in a saturated liquid state or a gas-liquid mixed state, and the refrigerant after throttling is always in a non-solid phase region. In this embodiment, the first throttling mechanism 319 and the second throttling mechanism 321 are throttle valves, and the opening of the throttle valves can also be adjusted so that the refrigerant flowing through the throttle valves is always in a saturated liquid state or a gas-liquid mixed state before and after throttling, and the medium state after throttling is in the non-solid phase region. The matching degree between the actual phase point position of the refrigerant after each stage of throttling and pre-cooling and the target phase point position is calculated through a multi-stage throttling theoretical model. The terminal cryotherapy temperature and pressure are precisely controlled by adjusting the throttling stages, the opening of the throttle valve and the pre-cooling power.

[0128] Figure 7 shows a phase change diagram of the refrigerant during multi-stage throttling within the cryotube. The phase points of the refrigerant before and after throttling are preferably located within the shaded area shown in Figure 7. The phase point of the refrigerant before entering the freezing unit 304 is preferably located to the right of the saturated liquid line within the shaded area in Figure 7. By adjusting the cooling power of the cold supply module or pre-cooling mechanism and the throttle valve opening, a wide range of cooling capacity and temperature requirements within the freezing unit 304 can be achieved. Depending on the refrigerant supplied, the temperature adjustment range can range from +80°C to -196°C. This temperature adjustment range allows the same cryotube to be used to treat a variety of lesions. Furthermore, a temperature and pressure sensing element 315 is provided within the freezing unit 304, and a rewarming heating element 316 is provided on the freezing unit 304. The rewarming heating element 316 can also be connected to a heating power regulator to adjust the rewarming temperature, thereby achieving precise control and adjustment of the target cryotherapy temperature and rewarming time.

[0129] Example 4

[0130] Referring to Figure 8 , this embodiment differs from the second embodiment in that three throttling mechanisms are provided within the cryotube's air inlet passage 330: a first throttling mechanism 319, a second throttling mechanism 321, and a third throttling mechanism 326. A pre-cooling mechanism 318 is provided at the proximal end of the cryotube's air inlet passage 330, forming a "one-stage pre-cooling + multi-stage throttling" cryotube. This embodiment selectively controls refrigerant throttling and maintains a gas-liquid mixed state after pre-cooling. The cryotherapy temperature of the freezing unit 304 can also be adjusted by designing the throttling mechanism and selectively controlling the pre-cooling mechanism's deactivation or adjusting its cooling power. The cold supply module of this embodiment optionally includes a cold storage chamber 332 filled with an antifreeze cold storage liquid. This cold storage liquid can be selected from ethylene glycol, glycerol, diethylene glycol, silicate, and other materials, with a freezing point setting range of -10°C to -50°C. Cold storage delays the refrigerant's melting time, enhancing the freezing effect and shortening the total duration of the cryotherapy procedure.

[0131] The foregoing is merely a preferred embodiment of the present application and is not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A freezing catheter, comprising a tube body and a freezing unit, wherein the proximal end of the tube body is connected to a cold source connector, and the distal end of the tube body is connected to the proximal end of the freezing unit, an air inlet passage and an air return passage are provided in the tube body, the distal ends of the air inlet passage and the air return passage are connected to the freezing unit, and the proximal ends of the air inlet passage and the air return passage are connected to the cold source connector, characterized in that: One or more throttling mechanisms are arranged in the air intake passage, thereby forming a multi-stage throttling freezing conduit.

2. The freezing catheter according to claim 1, wherein After the refrigerant fluid in the freezing pipe passes through the throttling mechanism provided in the air inlet passage and completes the last throttling, the ratio of the cooling capacity obtained by the multi-stage throttling of the freezing pipe to the cooling capacity obtained by the traditional single-stage throttling conforms to the following formula: in: is the cooling capacity ratio, f(P t0 ,T to ) is the energy value of the fluid after single-stage throttling of the conduit, f(P tn ,T tn ) is the energy value of the fluid after passing through the multi-stage throttling of the entire freezing pipe; f(P E ,T E ) is the energy value of the refrigerant multi-stage throttling expansion to absorb heat to saturation state, f(P F ,T F ) is the energy value of the refrigerant absorbed by the single-stage throttling expansion to the saturated state.

3. The freezing catheter according to claim 1, wherein The throttle mechanism is provided at a proximal end portion of the intake passage.

4. The freezing catheter according to claim 1, wherein The throttling mechanism is a combination of one or more of a throttling valve, a capillary tube, a reducing tube, an orifice plate or a nozzle.

5. The freezing catheter according to claim 1, wherein The number of multi-stage throttling stages of the freezing conduit is determined by the fluid state generated after each stage of the multi-stage throttling and the total cooling capacity Q that can be generated after the multi-stage throttling. The maximum cooling capacity Q that can be generated by the fluid after the multi-stage throttling is t It can be expressed as follows: Where △H is the enthalpy change of the fluid before and after each stage of throttling; f(P x ,T x ), f(P tx ,T tx ) are the energy values ​​of the fluid before and after the xth throttling respectively; T t and P t are the final fluid temperature and pressure after multi-stage throttling; T x 、T tx and P x 、P tx are the fluid temperature and pressure before and after the xth stage throttling respectively; c p is the specific heat capacity of the fluid at constant pressure, v is the specific volume of the fluid; Final fluid temperature after multi-stage throttling T t It can be expressed as: T t =Φ -1 (Q t ,P t ) When the total cooling capacity Q generated by multi-stage throttling is not less than Q t , the fluid temperature after multi-stage throttling does not exceed T t , the throttling levels selected by the system meet the requirements.

6. The freezing catheter according to claim 1, wherein One or more pre-cooling mechanisms are provided in the air intake passage.

7. The freezing catheter according to claim 6, wherein The pre-cooling mechanism is connected to the cold supply module, and the pre-cooling temperature of the pre-cooling mechanism is adjustable.

8. The freezing catheter according to claim 7, wherein The cooling capacity of the cooling supply module of the freezing pipe complies with the following formula: Among them, w is the cooling capacity supplied to the module of each stage of pre-cooling mechanism, f is the thermal efficiency of each stage of pre-cooling mechanism, and △u is the pre-cooling capacity of the refrigerant supplied by each stage of pre-cooling mechanism.

9. The freezing catheter according to claim 6, wherein The pre-cooling mechanism is a heat exchanger, and the heat exchanger includes at least one of a downstream heat exchanger, a countercurrent heat exchanger, a fin heat exchanger, a shell and tube heat exchanger, and an immersion heat exchanger.

10. The freezing catheter according to claim 9, wherein The cold supply module includes at least one of a micro semiconductor refrigeration pre-cooling module, a cold storage pre-cooling module, a throttling pre-cooling module, and a phase change pre-cooling module.

11. The freezing catheter according to claim 6, wherein The number of the pre-cooling mechanisms is one more than the number of the throttling mechanisms.

12. The freezing catheter according to claim 6, wherein The pre-cooling capacity of the refrigerant supplied by the pre-cooling mechanism is less than the critical pre-cooling capacity of the refrigerant phase change: Δu1=q m [f(P1, T1)-f(P0, T0)]<Δu0 Among them, △u1 is the pre-cooling capacity of the refrigerant supplied by the first-level pre-cooling mechanism, △u0 is the critical pre-cooling capacity of the refrigerant phase change, q m is the fluid mass flow rate, f(P1, T1) and f(P0, T0) are the energy values ​​of the refrigerant before and after passing through the first-stage precooling mechanism.

13. The freezing catheter according to claim 6, wherein The dryness of the refrigerant in the freezing pipe before and after the multi-stage throttling meets the following relationship: 0≤X(P tn ,T tn )<X(P t0 ,T t0 ) Where: X(P t0 ,T t0 ) is the dryness of the refrigerant after throttling in the single-stage throttling refrigeration pipe, X(P tn ,T tn ) is the refrigerant dryness in the multi-stage throttling refrigeration pipe after the refrigerant is throttled by the last stage throttling mechanism.

14. The freezing catheter according to claim 6, wherein A cold storage cavity is provided in the lumen of the freezing conduit, the cold storage cavity is sleeved outside the pre-cooling mechanism, and antifreeze cold storage liquid is contained in the cold storage cavity.

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