Refrigeration catheter

Abstract

The freezing catheter comprises a catheter body and a freezing unit, the near end of the catheter body is connected with a cold source connector, the far end of the catheter body is connected with the near end of the freezing unit, an air inlet channel and an air return channel are arranged in the catheter body, the far end of the air inlet channel and the far end of the air return channel are communicated with the freezing unit, and the freezing unit is communicated with the freezing unit. According to the freezing conduit, the problems that a freezing conduit of single-stage throttling is large in diameter and difficult to operate, the pressure of refrigerants before and after throttling in a freezing unit is high, the pressure of the refrigerants after throttling in the freezing unit is low, and the freezing efficiency is high are effectively solved. The problems of safety risk, unstable treatment temperature and the like exist.

Description

Technical Field

[0001] The utility model relates to the technical field of medical equipment, in particular to a freezing catheter used for cryotherapy. Background Art

[0002] In recent years, cryotherapy has made great progress in the treatment of human diseases. Cryosurgical 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 cryosurgical treatment on lesions. Such as treating certain forms of arrhythmias such as atrial fibrillation (AF), ablating tumors in cancer treatment, and for skin diseases, obstetric surgery, bronchial biopsy, etc. Cryotherapy technology has little trauma, few complications, and patients feel little pain when receiving 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, and 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 No. CN 106687058 B utilizes temperature control of the heat treatment element of the medical device to maintain the temperature of the cryoablation fluid within the 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] Although, compared with previous technologies, this patent has made some improvements in the treatment of atrial fibrillation by extending the melting period of the fluid, there are still many difficulties in using this technology to effectively treat a variety of diseases in the actual clinical diagnosis and treatment process. Through analysis, it is found that in each cryotherapy of the prior art, the refrigerant gas is in the cryocatheter, especially the head end of the cryocatheter, to complete the first-level throttling, absorb heat through evaporation, take away the heat of the tissue, reduce the temperature of the target treatment site, and destroy the abnormal cell tissue, thereby achieving the purpose of cryotherapy. The prior art uses the following four main disadvantages of first-level throttling.

[0004] 1. It cannot provide a low enough cryotherapy temperature. It is known in the art that the lower the temperature, the shorter the residence / treatment time is required, and the shorter the residence / treatment time is, the friendlier it is to the patient. Due to the limitations of the refrigerant flow through the probe, the refrigerant properties, and especially the energy loss during the process, the lowest freezing temperature that can be achieved by the prior art is basically fixed. How to provide a low enough treatment temperature to enable cryotherapy technology to be applied to more types of lesions, and how to provide a low enough treatment temperature to make the treatment time shorter and shorten the residence / treatment time of the device on the patient are difficult problems in the prior art.

[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 cryonic killing effect on the target tissue. The cooling rate that can be achieved by one-stage throttling is limited. In order to improve the cryonic killing effect, it is generally achieved by increasing the number of freezing times and freezing time or reducing the freezing temperature. Increasing the number of freezing times and freezing time will correspondingly increase the risk of freezing damage to normal tissues. Lowering the freezing temperature is limited by the theoretical limit of single-stage throttling.

[0006] 3. The diameter of the cryo-catheter is too large, which limits the permeability of catheter interventional treatment. Due to the different anatomical structures of different blood vessels, respiratory tracts, digestive tracts, etc., the diameter of the applicable interventional catheter is different. The minimum diameter of the instrument channel of some bronchial and coronary vessels is only about 1mm, so the diameter requirement of the interventional cryo-catheter is extremely demanding. Using existing technology, it has been proven to be quite difficult to provide a cryo-catheter that is both small in size and has sufficient cooling capacity.

[0007] Fourth, the pressure at the end of the probe entering the human body is too high, which poses safety risks and technical limitations. According to the existing technology, the use of one-stage throttling and maintaining a high pressure difference before and after throttling can produce a lower freezing temperature. However, the refrigerant pressure entering the probe is too high, which poses a great safety risk. To solve this problem, most foreign companies use high-pressure balloons. However, due to reasons such as material and processing precision, high-pressure balloon technology is mainly monopolized by multinational companies, which has limited the breakthrough of domestic medical device companies in this field in a short period of time.

[0008] 5. A single device cannot provide a wide range of cryotherapy temperatures, and existing technologies rarely achieve multiple functions in one device. This is because different temperatures are suitable for treating different lesions. For example, the cryotherapy temperature range for treating atrial fibrillation is generally between -40°C and -50°C, while the cryotherapy temperature range for tumor treatment is much lower, generally between -40°C and -196°C. Existing technologies basically use the same cryotherapy device for the same lesion. The fundamental reason is that the system's freezing temperature cannot be accurately adjusted. This phenomenon has caused a great waste of resources and brought unnecessary troubles to medical staff's use and learning.

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

[0010] 1. How to obtain lower treatment temperature and faster cooling rate, shorten treatment time and reduce surgical risks;

[0011] 2. How to provide a high-energy, small-diameter cryocatheter to achieve treatment of lesions in special locations;

[0012] 3. How to provide a solution to reduce the problem of high refrigerant pressure in the existing freezing unit, and even apply low-pressure balloons, reduce surgical risks, and break 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 utility model is to provide a cryo-catheter in view of the deficiencies of the prior art. The implementation scheme of the utility model to solve the problems of the prior art is to adopt multi-stage throttling, and the number of throttling stages is several stages. In the actual operation process, by adjusting the coordination relationship between the throttling stages, the cold capacity, the working temperature and the cooling rate are controlled, so as to control the freezing depth of the lesion tissue and minimize the amount of refrigerant fluid required. This scheme effectively reduces the diameter of the cryo-catheter, reduces the internal pressure of the cryo-catheter, avoids operational difficulties, 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 the utility model 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 arranged in the tube body, the distal ends of the air intake passage and the air return passage are communicated with the freezing unit, and the proximal ends of the air intake passage and the air return passage are communicated with the cold source joint, and one or more throttling mechanisms are arranged in the air intake passage.

[0017] The purpose of the utility model can also be further achieved through the following technical solutions:

[0018] In one embodiment, after the refrigerant fluid of 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 meets the following formula:

[0019]

[0020] 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 multi-stage throttling of the entire freezing conduit; 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 in single-stage throttling expansion.

[0021] In one embodiment, the throttle mechanism is disposed at a proximal portion of the intake passage.

[0022] In one embodiment, when the number of the throttling mechanism is one, the cryoconduit is a two-stage throttling cryoconduit.

[0023] In one embodiment, when the number of the throttling mechanisms is two or more, the cryoconduit is a cryoconduit with three or more stages of throttling.

[0024] In one embodiment, the throttling mechanism is a combination of one or more of a throttling valve, a capillary tube, a reducer, an orifice plate or a nozzle.

[0025] 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 refrigeration capacity Q that can be generated after the multi-stage throttling. The maximum refrigeration capacity Q that can be generated by the fluid after the multi-stage throttling is t It can be expressed as follows:

[0026]

[0027] 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;

[0028] Final fluid temperature after multi-stage throttling T t It can be expressed as:

[0029] T t =Φ -1 (Q t , P t )

[0030] 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 level selected by the system meets the requirements.

[0031] In one embodiment, the air inlet passage of the cryoconduit is provided with one or more pre-cooling mechanisms.

[0032] In a preferred embodiment, the precooling mechanism is connected to a cold supply module, and the precooling temperature of the precooling mechanism is adjustable.

[0033] In a preferred embodiment, the precooling mechanism is a heat exchanger, and the heat exchanger includes at least one of a co-current heat exchanger, a counter-current heat exchanger, a fin heat exchanger, a shell and tube heat exchanger, and an immersion heat exchanger.

[0034] In a preferred embodiment, the cold supply module includes at least one of a micro semiconductor refrigeration precooling module, a cold storage precooling module, a throttling precooling module, and a phase change precooling module.

[0035] In a preferred embodiment, the cooling capacity of the cooling supply module of the freezing pipe meets the following formula:

[0036]

[0037] Among them, w is the cooling capacity supplied to the module by each stage of precooling mechanism, f is the thermal efficiency of each stage of precooling mechanism, and △u is the precooling capacity of refrigerant supplied by each stage of precooling mechanism.

[0038] In a preferred embodiment, the number of the precooling mechanisms is one greater than the number of the throttling mechanisms.

[0039] In a preferred embodiment, the precooling amount of the refrigerant supplied by the precooling mechanism is less than the critical precooling amount of the refrigerant phase change:

[0040] Δu1=q m [f(P1, T1)-f(P0, T0)]<Δu0

[0041] Among them, △u1 is the precooling amount of refrigerant supplied by the first-level precooling mechanism, △u0 is the critical precooling amount of 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 primary precooling mechanism.

[0042] In one embodiment, the dryness of the refrigerant before and after multi-stage throttling meets the following relationship:

[0043] 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 of the refrigerant in the multi-stage (n>1) throttling freezing pipe after the refrigerant is throttled by the last stage throttling mechanism. Through the reasonable configuration of the multi-stage throttling and pre-cooling mechanism, the dryness of the refrigerant after the throttling of the last stage throttling mechanism can be significantly reduced, and the amount of heat absorbed by the liquid refrigerant generated after throttling entering the refrigeration unit for vaporization and heat absorption is significantly increased, thereby increasing the refrigeration capacity of the freezing pipe.

[0044] In one embodiment, one or more temperature and pressure sensing elements are arranged in the air inlet passage of the cryotherapy catheter, and the temperature and pressure sensing elements are connected to the human-computer interaction module and the cryotherapy equipment through electrical signals, so that the operator can monitor and / or control the temperature and / or pressure in the treatment area.

[0045] In one embodiment, a rewarming heating element is provided on the freezing unit of the freezing catheter.

[0046] In one embodiment, the cryocatheter is one of a cryoprobe, a cryoablation catheter, or a cryoballoon.

[0047] In one embodiment, the freezing unit is a round-head-shaped, needle-shaped, ellipsoid-shaped, or spherical-shaped metal and / or polymer material, or a combination of several of them.

[0048] In one embodiment, a cold storage cavity is provided in the lumen of the freezing conduit, the cold storage cavity is sleeved outside the precooling mechanism, and antifreeze cold storage liquid is filled in the cold storage cavity.

[0049] Compared with the prior art, the beneficial effects of the utility model are as follows:

[0050] 1. The prior art completes a throttling by releasing the refrigerant in the freezing unit, absorbs heat through evaporation, takes away the heat of the tissue, reduces the temperature of the target treatment site, and destroys the abnormal cell tissue, thereby achieving the purpose of treatment. Different from the prior art, the implementation scheme of the utility model adopts multi-stage throttling. One or more throttling structures are arranged in the air inlet passage of the freezing catheter, and the throttling stages are several stages. The high-pressure cooling medium of the cryotherapy flows through several throttling mechanisms arranged on the pipeline in sequence. Each throttling mechanism will make the high-pressure cooling medium experience a pressure drop and temperature drop process, realize the step-by-step cooling and pressure reduction of the high-pressure cooling medium, complete multi-stage throttling, and finally reach the freezing unit. The last throttling is completed in the freezing unit, and the cryotherapy is realized at a lower pressure, thereby achieving the purpose of treatment. Multi-stage throttling can improve the cooling efficiency, achieve a faster cooling rate and a lower working temperature of cryotherapy, and increase the range of cryoablation, which greatly increases the rate of tissue or cell low-temperature killing and the effective low-temperature damage range.

[0051] 2. The cryo-catheter described in the utility model can select the appropriate throttling level and cryotherapy temperature according to the actual needs of lesion treatment. The cryo-catheter of the utility model is also provided with a pre-cooling mechanism. By multi-stage throttling and pre-cooling, the enthalpy difference of the refrigerant before and after the throttling of the freezing unit is increased, and the cryotherapy temperature is further reduced. Even if the diameter of the freezing catheter tube body is reduced, the temperature and cold capacity required for cryotherapy can still be achieved, which can meet the needs of cryotherapy of lesions in narrow areas. At the same time, during the treatment, by adjusting the coordination relationship between the throttling of each level, the cold capacity of the refrigerant carrier and the treatment temperature at the end of the freezing 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 the throttling of the freezing unit, accelerate the cooling speed, and enable the probe to be used in conjunction with a low-pressure freezing balloon. The utility model can reduce the temperature variation range at the end of the freezing unit, achieve stable and accurate control of the cryotherapy temperature, and improve the treatment effect of the equipment and the safety of the operation.

[0052] 3. The utility model configures a plurality of 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

[0053] Figure 1 It is a schematic structural diagram of the first embodiment of the multi-stage throttling freezing catheter of the utility model.

[0054] Figure 2 It is a schematic diagram of the evolution law of the medium in the pressure-enthalpy diagram during the three-stage throttling process of the utility model.

[0055] Figure 3 It is a schematic structural diagram of a second embodiment of the multi-stage throttling freezing catheter of the utility model.

[0056] Figure 4 for Figure 3 The diagram shown is a schematic diagram of the evolution law of the refrigerant medium in the pressure-enthalpy diagram during the throttling process of the multi-stage throttling refrigerant pipe.

[0057] Figure 5 It is a theoretical model for calculating the temperature of the medium after throttling in the multi-stage throttling process of the utility model.

[0058] Figure 6 It is a structural schematic diagram of the third embodiment of the multi-stage throttling freezing catheter of the utility model.

[0059] Figure 7 for Figure 6 The diagram shown is a schematic diagram of the evolution law of the refrigerant medium in the pressure-enthalpy diagram during the throttling process of the multi-stage throttling refrigerant pipe.

[0060] Figure 8It is a structural schematic diagram of the fourth embodiment of the multi-stage throttling freezing catheter of the utility model. DETAILED DESCRIPTION

[0061] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0062] 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 utility model. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or their combinations;

[0063] For the convenience of description, if the words "upper", "lower", "left" and "right" appear in the present invention, they only indicate that they are consistent with the upper, lower, left and right directions of the drawings themselves, and do not limit the structure. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the equipment or components referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. The "proximal end" described in the present invention refers to the end close to the surgical operator, and the "distal end" described refers to the end away from the surgical operator.

[0064] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and cannot be used to limit the scope of the present invention.

[0065] The utility model 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 prior art. The innovation of the utility model is the use of multi-stage throttling, in which one or more throttling mechanisms are arranged in the air inlet passage of the freezing catheter, and the number of throttling stages is several. Different from the prior art, the refrigerant gas of the utility model passes through several throttling mechanisms in sequence to complete multi-stage throttling, and finally reaches the freezing unit to complete the last throttling in the freezing unit. In the multi-stage throttling process, the utility model 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 cold output and treatment effect during cryotherapy. Compared with the prior art, the utility model 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 lesion requires a certain amount of freezing refrigeration, even if the diameter of the freezing catheter tube body is reduced, the temperature and cold capacity required for cryotherapy can still be achieved. During the treatment procedure, by adjusting the coordination relationship between the throttling levels and controlling the cold 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 utility model adopts multi-stage throttling to reduce the refrigerant temperature and pressure before throttling in the freezing unit, speeding up the cooling speed, so it can be used in conjunction with a low-pressure balloon, reducing surgical risks, and breaking through the technical monopoly restrictions of foreign countries on high-pressure balloons.

[0066] The present invention is described in detail below through some embodiments of a multi-stage throttling freezing catheter.

[0067] Embodiment 1

[0068] See also Figure 1A freezing catheter comprises a tube body 302 and a freezing unit 304, wherein the proximal end of the tube body 302 is connected to a cold source joint 301, and the distal end of the tube body 302 is connected to the proximal end of the freezing unit 304, and an air intake passage 330 and an air return passage 328 are arranged in the tube body 302, wherein the distal ends of the air intake passage 330 and the air return passage 328 are connected to the freezing unit 304, and the proximal end of the air intake passage 330 is connected to the cold source joint 301, and the air return passage 328 is connected to the cold source joint 301. A waste gas outlet 307 is provided at the proximal end of the path 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, and 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.

[0069] During the cryotherapy process, the air inlet passage 330 is a refrigerant supply lumen for cryotherapy. The refrigerant can be one of CO2, N20, Freon refrigerant, nitrogen, and argon. The refrigerant comes from the cryotherapy device. The refrigerant output from the cryotherapy device enters the cryotube through the inlet of the cold source joint 301, and flows through the first throttling mechanism 319 in the axial direction of the inner cavity of the air inlet passage 330 in sequence, forming the first stage of throttling; then flows through the gas nozzle 317 in the freezing unit 304, forming the "second stage of throttling". The refrigerant gas evaporates and absorbs heat in the expansion chamber of the freezing unit 304, completing the cryotherapy process for the target tissue. The evaporated and gasified refrigerant passes through the return air port 324 set in the freezing unit 304, enters the return air passage 328, reaches the exhaust gas outlet 307, and is discharged to the exhaust gas recovery system. At this point, the refrigerant completes a complete cryotherapy process in the freezing catheter through the "secondary throttling".

[0070] In one embodiment, two or more throttling mechanisms are provided in the air intake passage 330, forming a three-stage throttling or multi-stage throttling freezing conduit. Theoretically, the more throttling levels there are, the better the final effect of the present invention will be. However, as the throttling levels increase, the processing steps of the freezing conduit will also become more complicated. Therefore, the appropriate throttling levels can be selected according to the application scenario.

[0071] After the refrigerating fluid of the refrigerating pipe passes through the throttling mechanism provided in the air inlet passage and completes the last throttling in the refrigerating unit, the ratio of the cooling capacity obtained by the multi-stage throttling of the refrigerating pipe to the cooling capacity obtained by the traditional single-stage throttling meets the following formula:

[0072]

[0073] 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 multi-stage throttling of the entire freezing conduit; 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 in the refrigeration pipe when it absorbs heat to the saturated state in a single-stage throttling expansion.

[0074] See also Figure 2 When using the prior art 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., the process from 1 to 6) in the freezing unit, the refrigerant directly reaches phase point 6 (P t0 、T t0 The utility model 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, such as Figure 2 As shown, in the first embodiment, the refrigerant at phase point 1 (P1, T1) is throttled to 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 primary throttling, to phase point 3 through the secondary throttling, and finally to the refrigeration unit of the refrigeration pipe to complete the tertiary throttling. After throttling, the refrigerant reaches phase point 4 (P t3 、T t3 ). Figure 2 Compared with the existing technology, 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 P after throttling of multi-stage throttling is E Compared with the post-throttling pressure P of single-stage throttling F Compared to: P E <P F The multi-stage throttling method of the utility model can increase the refrigeration 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.

[0075] If the distance between the two stages of throttling is too small, the fluid flow may be disturbed, resulting in unstable phenomena such as eddy currents, fluctuations or oscillations. If the distance is too large, the pipeline may be too long, the flow resistance may be too large, causing serious energy loss and increasing the ineffective length of the conduit. The utility model determines the setting of each stage of throttling mechanism according to 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 state, including known parameters such as pressure, flow rate, cross-sectional area before throttling. It should be noted that the above calculation needs to be derived under certain assumptions, such as incompressible, ideal fluid, etc. In practical applications, some correction factors need to be considered, such as the compressibility of the fluid, viscosity loss, friction, etc.

[0076] The throttling stages of the freezing conduit are based on the fluid enthalpy change formula 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:

[0077]

[0078] By the formula,

[0079] dH=Tds+vdp

[0080] It can be deduced that

[0081]

[0082] According to Maxwell's relations:

[0083]

[0084] And the formula,

[0085]

[0086] The general expression for fluid enthalpy change is derived using the equation of state and specific heat:

[0087]

[0088] Since the enthalpy of the fluid in the pipe changes to △H before and after throttling, the above expression can be used to deduce f(P1, T1) and f(P t1 , T t1 )Enthalpy change:

[0089]

[0090] The number of multi-stage throttling of the freezing pipe is determined by the fluid state (e.g., temperature, pressure, etc.) generated after each stage of the multi-stage throttling and the total refrigeration capacity Q that can be generated after the multi-stage throttling. The maximum refrigeration capacity Q that can be generated by the fluid after the first stage of throttling is t1 It can be expressed as follows:

[0091]

[0092] Among them, △H is the enthalpy change of the fluid before and after the first stage of 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.

[0093] The maximum cooling capacity Q that can be generated by the fluid after multi-stage throttling t It can be expressed as follows:

[0094]

[0095] 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.

[0096] Final fluid temperature after multi-stage throttling T t It can be expressed as:

[0097] T t =Φ -1 (Q t , P t )

[0098] 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 level selected by the system meets the requirements.

[0099] The throttling level of the freezing catheter is verified by a multi-stage throttling theoretical model combined with experimental tests. After calculation and experiment, when multi-stage throttling is adopted, the distance between the center points of the two-stage throttling mechanism is preferably 5-100 times the maximum diameter of the pipeline, which is related to the structural form and installation position of the adopted throttling mechanism. The throttling mechanism can be at least one of a throttling valve, a capillary tube, a reducer, an orifice plate, and a nozzle, preferably a throttling valve.

[0100] See also Figure 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 in the freezing catheter, and the temperature and pressure sensing elements are connected to the human-machine interaction module and the cryotherapy device through electrical signals so that the operator can monitor and / or control the temperature and / or pressure in the treatment area. The temperature sensing element and the 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 in the freezing unit 304 to monitor the temperature and pressure in the pipeline and the freezing unit, and control the pressure of the fluid to prevent the fluid pressure from being too high. The temperature sensing element can be a K-type thermocouple, a T-type thermocouple, or a patch temperature sensor. The pressure sensing element can be a pressure-type, piezoresistive, piezoelectric, capacitive, or electromagnetic pressure sensor. The temperature and pressure sensor is an integrated temperature sensing element and a pressure sensing element to achieve simultaneous measurement of temperature and pressure.

[0101] In practical applications, the cryo-catheter is one of a cryoprobe, a cryoablation catheter or a cryo-balloon. The outer layer of the tube body 302 of the cryo-catheter is made of a heat-insulating material such as plastic or rubber.

[0102] Embodiment 2

[0103] See also Figure 3The structure of this embodiment is basically the same as that of the first embodiment. A freezing catheter includes 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 intake passage 330 and an air return passage 328 are arranged in the tube body 302. The distal ends of the air intake passage 330 and the air return passage 328 are connected to the freezing unit 304, and the proximal ends of the air intake passage 330 are connected to 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 through the cold source connector 301. The difference is that: a first throttling mechanism 319 and a second throttling mechanism 321 are arranged in the air intake passage 330, and the first throttling mechanism 319 and the second throttling mechanism 321 are both arranged at the proximal part of the air intake passage 330, and the first throttling mechanism 319 and the second throttling mechanism 321 together with the freezing unit 304 form a three-stage throttling structure. Three precooling mechanisms are also arranged at the proximal part of the air intake passage 330, namely, a first-stage precooling mechanism 318, a second-stage precooling mechanism 320, and a third-stage precooling mechanism 322, and these three precooling mechanisms are respectively connected to the cold supply module 325. In this embodiment, the number of the precooling mechanisms is one more than the number of the throttling mechanisms, so the first throttling mechanism 319 and the second throttling mechanism 321 together with the first-stage precooling mechanism 318, the second-stage precooling mechanism 320, and the third-stage precooling mechanism 322 constitute a three-stage throttling and three-stage precooling freezing conduit.

[0104] like Figure 3As shown, during the cryotherapy process, the air inlet passage 330 is a refrigerant supply lumen for cryotherapy. The refrigerant can be one of CO2, N2O, Freon refrigerant, nitrogen, and argon. The refrigerant comes from the above-mentioned cryotherapy equipment. The refrigerant output from the cryotherapy equipment enters the cryotube through the inlet of the cold source joint 301, and flows through the first-level precooling mechanism 318 and the first throttling mechanism 319 in the axial direction of the inner cavity of the air inlet passage 330 in sequence, forming a "first-level precooling + first-level throttling" mechanism; flows through the second-level precooling mechanism 320 and the second throttling mechanism 321, forming a "second-level precooling + second-level throttling" mechanism; flows through the third-level precooling mechanism 322, forming a "third-level precooling mechanism"; flows through the gas nozzle 317 in the freezing unit 304, forming a "third-level throttling mechanism". The refrigerant gas evaporates and absorbs heat in the expansion chamber of the freezing unit 304, completing the cryotherapy process for the target tissue. The evaporated refrigerant passes through the return air port 324 provided in the freezing unit 304, enters the return air passage 328, reaches the exhaust gas outlet 307, and is discharged to the atmosphere or the exhaust gas recovery system. At this point, the refrigerant completes a complete cryotherapy process through "three-stage precooling + three-stage throttling" in the freezing catheter.

[0105] The precooling 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 precooling mechanism 318, the second-stage precooling mechanism 320 and the third-stage precooling mechanism 322 are a countercurrent heat exchanger, the main component material 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 that extends and is arranged in the axial direction of the air intake passage 330 and can be configured 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 precooling mechanism 318, the second-stage precooling mechanism 320 and the third-stage precooling mechanism 322 are fixed on the outer surface of the tube wall 323 of the air inlet passage 330, and their 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 to cool the refrigerant fluid. The heat exchange between the refrigerant fluid and the heat transfer body of the precooling mechanism is countercurrent heat exchange. The material of the heat transfer body of the precooling 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 precooling mechanism 318, the second-stage precooling mechanism 320 and the third-stage precooling 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 joint 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.

[0106] The first throttling mechanism 319 and the second throttling mechanism 321 can be a combination of at least one or more of a throttling valve, a capillary, a reducer, an orifice plate, and a nozzle. The freezing unit 304 is designed as an expansion cavity structure, which provides space for the expansion and evaporation of the refrigerant, forms a low temperature by throttling, and freezes the human tissue. A gas nozzle 317 and a temperature and pressure sensing element 315 are arranged in the freezing unit 304. A rewarming heating element 316 is also arranged at the freezing unit 304 to speed up the rewarming rate and shorten the operation time. The freezing unit 304 can be any one of a freezing probe or a balloon.

[0107] like Figure 4 As shown, it is assumed that the refrigerant state of the gas source output of the cryotherapy device is at phase point 2 (P1, T1), where P and T represent the pressure and temperature in this state respectively. The refrigerant completes the multi-stage "throttling + precooling" 2-3-4-5-6-7 process as follows: the refrigerant is throttled by the first throttling mechanism 319 to phase point 3 (P t1 、T t1); then precooled by the secondary precooling 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 precooled by the three-stage precooling mechanism 322 to phase point 6 (P3, T3), and finally completed the three-stage throttling process in the refrigeration unit 304, after throttling to phase point 7 (P t3 、T t3 The refrigerant gas after throttling in the freezing unit 304 exchanges heat with the tissue in the freezing unit 304 of the freezing catheter, and the process phase point 7-phase point 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, takes away the heat of the tissue, and lowers the temperature of the target treatment site to form an ice ball, and the abnormal cell tissue is destroyed. After the refrigerant throttles and absorbs heat to a saturated state, it reaches phase point 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 waste gas outlet 307 of the return gas passage 328 of the freezing pipe. Under the evaporation pressure, the heat absorbed by the refrigerant is equal to the latent heat of evaporation of the refrigerant, which is the refrigeration capacity of the freezing pipe. As shown in the following formula:

[0108] q2=f(P E , T E )-f(P3,T3)

[0109] Among them, 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, and f(P E , T E ) is the energy value of the refrigerant when it expands and absorbs heat to the saturated state at phase point 9.

[0110] According to the embodiment of the utility model, the pressure of the refrigerant entering the freezing unit of the freezing pipe is the pressure P3 of phase point 6, and the pressure after throttling in the freezing unit is the pressure P of phase point 7. t3 , the pressure difference before and after multi-stage throttling is ΔP2.

[0111] According to the laws of thermodynamics, there is no heat or work exchange between the refrigerant before and after throttling, so the energy value remains unchanged. Figure 4 As shown, the initial phase point 2 (P1, T1) of the refrigerant entering 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 the phase point 2 (P1, T1) to the phase point 8 (P t0 、T t0 ), the entire throttling process is carried out in the refrigeration unit 304, without multi-stage throttling and pre-cooling auxiliary links, such as Figure 4As shown, the process of primary throttling of the refrigerant in the cryotube is a straight line from phase point 2 to phase point 8. After throttling, the refrigerant performs heat exchange in the cryotube freezing unit 304, and the process is from phase point 8 to phase point 10. After absorbing heat, the energy value of the refrigerant increases and it is continuously vaporized. 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 a saturated state, the refrigerant reaches phase point 10 (P F 、T F ).

[0112] See also Figure 4 The cryoablation treatment process of the prior art is a process of the first-order throttling phase point 2-8-10. The heat absorption of the refrigerant and the latent heat of evaporation of the refrigerant under the evaporation pressure are equal, which is equal to the refrigeration capacity of the cryocatheter. The refrigeration capacity of the cryocatheter of the prior art is shown as follows:

[0113] q1=f(P F , T F )-f(P t0 , T t0 )

[0114] 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 the saturated state at the phase point 10.

[0115] 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.

[0116] As mentioned above, after the fluid passes through the 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:

[0117]

[0118] 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 absorbing heat to saturation state during single-stage throttling expansion.

[0119] Compared with the prior art, the cryotherapy system provided by the present invention has a significantly increased refrigeration capacity per unit of refrigerant for cryotherapy compared with the prior art; the pressure P3 before throttling of the refrigerant when it enters 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, the technical solution of the utility model can reduce the diameter of the cryo-catheter relative to the existing technology under the same cooling demand. The reduction in the diameter of the cryo-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 utility model, 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.

[0120] The utility model can establish a multi-stage throttling design theoretical model by monitoring the temperature and pressure of the refrigerant before and after throttling, and confirm the appropriate throttling level of the freezing pipe according to the theoretical model. The specific implementation steps are as follows:

[0121] 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 fluid mass flow rate q m , the target phase point (P tn 、T tn );

[0122] See also Figure 5 In the second step, according to the 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);

[0123] The third step is to plan the phase point position before and after the fluid throttling. If a precooling mechanism is required, plan the pre-throttling value phase point at the phase point position after precooling and before throttling. For example, if precooling is performed before the first-level throttling, the precooling mechanism before the first-level throttling is set according to the planned pre-throttling value phase point (P1, T1), and calculate the cooling capacity Δu1 of the corresponding precooling supply mechanism. The precooling capacity of the refrigerant supplied by the precooling module must be less than the critical precooling capacity of the phase change of the refrigerant:

[0124] Δu1=q m [f(P1, T1)-f(P0, T0)]<Δu0

[0125] Among them, △u1 is the precooling amount of refrigerant supplied by the first-level precooling mechanism, △u0 is the critical precooling amount of 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 primary precooling mechanism;

[0126] 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:

[0127]

[0128] 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.

[0129] 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 is T t2 , and so on, the enthalpy change of the fluid after the xth stage of throttling can be expressed as follows:

[0130]

[0131] 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 xth stage of 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.

[0132] The precooling capacity of the refrigerant supplied by the x-stage precooling is:

[0133] Δu x =q m [f(P x , T x )-f(Pt(x-1 ), T t(x-1) )] 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:

[0134]

[0135] The precooling capacity of the refrigerant supplied by the last stage of precooling is:

[0136] Δu n =q m [f(P n , T n )-f(P t(n-1) , T t(n-1) )]

[0137] The fifth step is to analyze whether the precooling / throttling process reaches the critical pressure according to different throttling types, establish a safe and economical multi-stage throttling cryotherapy program, and determine the final throttling level and precooling level, and the maximum precooling capacity of each level;

[0138] 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 through 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.

[0139] According to the temperature change, pressure change, target temperature of cryotherapy in the multi-stage throttling process, etc., this model can accurately predict the pressure and temperature of different refrigerants in different modes, avoid the formation of solid state in the process of fluid throttling and precooling, cause ice blockage, and affect the normal operation of cryotherapy equipment. The control principle of multi-stage throttling cryotherapy equipment is to supply enough cold capacity to the freezing unit of the cryotube as soon as possible, minimize the diameter of the cryotube, minimize the pressure drop before and after the throttling mechanism, reduce the precooling amount, reduce the number of throttling stages, and the number of precooling stages, and give the calculation method of each stage of precooling amount and the selection method of multi-stage throttling stages.

[0140] The utility model 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 precooling is X(P t0 , T t0 )for:

[0141]

[0142] Where: fx (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.

[0143] The dryness of the refrigerant in the refrigeration pipe after multi-stage throttling and precooling is X(P tn , T tn )for:

[0144]

[0145] 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.

[0146] Therefore, the dryness of the refrigerant in the freezing pipe before and after multi-stage throttling meets the following relationship:

[0147] 0≤X(P tn , T tn )<X(P t0 , T t0 )

[0148] 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 throttling by the last stage throttling mechanism in the multi-stage throttling refrigeration pipe.

[0149] 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 refrigeration capacity of the freezing pipe will be significantly improved.

[0150] Embodiment 3

[0151] See also Figure 6This embodiment is a variation of the second embodiment. Figure 3 Differently, in this embodiment, the cold supply module of the first-stage precooling mechanism 318, the second-stage precooling mechanism 320 and the third-stage precooling mechanism 322 can be placed in the cryotherapy device to reduce the volume of the cryotherapy catheter and simplify the processing difficulty. The cold supply module is input through the precooling cold source supply port C of the cold source connector 301, and is supplied to the third-stage precooling mechanism 322, the second-stage precooling mechanism 320, and the first-stage precooling mechanism 318 in sequence along the cold source supply lumen 331, and then output through the outlet D of the precooling cold source and return to the cryotherapy device. In addition, the air intake passage 330 of this embodiment is the inner cavity of the air intake pipe, and the return air pipe is sleeved outside the air intake pipe. The cavity surrounded by the outer wall of the air intake pipe and the inner wall of the return air pipe is the return air passage 328.

[0152] The cold supply module is installed in the cryotherapy device and can be an independent refrigeration system. For example, a micro semiconductor refrigeration module can theoretically also be a refrigeration source formed by another pipeline system of the gas source branch in the cryotherapy device using the Joule-Thompson effect. The cold supply module arranged outside the freezing catheter can supply cold to the refrigerant in the air intake passage 330 through the cold source connector 301 using a pipeline or a thermoelectric element. Other common means can be used to achieve the supply of cold, which will not be repeated here. This embodiment can further increase the coldness of the refrigerant and extend the melting time of the refrigerant.

[0153] The working process of the multi-stage throttling cryo-catheter of this embodiment is as follows: the refrigerant passes through the refrigerant inlet A, enters the air inlet passage 330, first passes through the first-stage pre-cooling mechanism 318 to cool down, 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 down, 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, and 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.

[0154] In one embodiment, the first throttling mechanism 319 and the second throttling mechanism 321 are reducers. Figure 6As shown, a cold storage cavity 332 is provided in the tube cavity 302 of the freezing conduit, and the cold storage cavity 332 is sleeved outside the precooling mechanism. Antifreeze cold storage liquid is filled in the cold storage cavity 332. The antifreeze cold storage liquid can be ethylene glycol, propylene glycol, diethylene glycol, silicate, etc., and the freezing point temperature is set in the range of -10°C to -50°C. Before or during the program operation, the antifreeze cold storage liquid in the cold storage cavity 332 can continue to supply the coldness of the first-stage precooling mechanism 318, the second-stage precooling mechanism 320 and the third-stage precooling mechanism 322, and continuously cool the refrigerant in the air intake passage 330. The tube wall 323 of the air intake passage 330 is made of a heat-conducting material, such as copper, silver, aluminum or steel, in particular stainless steel or carbon fiber.

[0155] In another embodiment, the precooling temperature of the precooling mechanism is adjustable. Figure 6 , a multi-stage throttling cooling structure is formed by the cooperation of the first-stage precooling mechanism 318, the first throttling mechanism 319, the second-stage precooling mechanism 320, the second throttling mechanism 321, and the third-stage precooling mechanism 322, and the power of the cooling supply module is adjusted by the PID or non-PID software algorithm to control the cooling power of the first-stage precooling mechanism 318, the second-stage precooling mechanism 320, and the third-stage precooling 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 throttling valves, and the opening of the throttling valve can also be adjusted so that the refrigerant flowing through the throttling valve 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 a non-solid phase region. The matching degree between the actual phase position of the refrigerant after each stage of throttling and precooling and the target phase position is calculated through a multi-stage throttling theoretical model. The terminal cryotherapy temperature and pressure are precisely controlled by adjusting the throttling stage, the opening of the throttling valve and the precooling power.

[0156] like Figure 7 As shown, the phase change diagram of the refrigerant in the multi-stage throttling in the freezing pipe. The phase point of the refrigerant before and after throttling is preferably Figure 7 The shaded area shown in FIG. 1 shows that the phase point of the refrigerant before entering the refrigeration unit 304 is preferably Figure 7The area to the right of the saturated liquid line in the shaded area. By adjusting the cooling power of the cold supply module or the pre-cooling mechanism and the throttle valve opening, a wider range of cold capacity and temperature requirements in the freezing unit 304 can be achieved. Depending on the refrigerant supplied, the temperature adjustment range can be between +80°C and -196°C. The temperature adjustment range allows the same freezing catheter to be adapted to the treatment of a variety of lesions. In addition, a temperature and pressure sensing element 315 is provided in 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, so as to achieve the adjustment and precise control of the target cryotherapy temperature and the freezing rewarming time.

[0157] Embodiment 4

[0158] See also Figure 8 , the difference between this embodiment and the second embodiment is that: three throttling mechanisms are set in the air inlet passage 330 of the cryotube, namely the first throttling mechanism 319, the second throttling mechanism 321 and the third throttling mechanism 326, and a precooling mechanism 318 is set at the proximal end of the air inlet passage 330 of the cryotube, forming a "first-stage precooling + multi-stage throttling" cryotube. In this embodiment, the cryotherapy device can selectively control the refrigerant throttling and precooling to always be in a gas-liquid mixed state, and can also adjust the cryotherapy temperature of the freezing unit 304 by designing the structure of the throttling mechanism and selectively controlling the closing of the precooling mechanism or adjusting its refrigeration power. The cold supply module of this embodiment can select a cold storage cavity 332 filled with antifreeze cold storage liquid, and the antifreeze cold storage liquid can be selected from ethylene glycol, glycerol, diethylene glycol, silicate, etc., and the freezing point temperature setting range is -10°C to -50°C. Cold storage can delay the melting time of the refrigerant, enhance the freezing effect, and shorten the total time of the cryotherapy operation.

[0159] The above description is only the preferred embodiment of the utility model and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

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 joint, 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 arranged in the tube body, the distal ends of the air intake passage and the air return passage are connected to the freezing unit, and the proximal ends of the air intake passage and the air return passage are connected to the cold source joint, 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 cryo-catheter according to claim 1, characterized in that: After the refrigerant fluid of 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 meets 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 multi-stage throttling of the entire freezing conduit; 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.

3. The cryocatheter according to claim 1, characterized in that: The throttle mechanism is provided at a proximal end portion of the intake passage.

4. The cryocatheter according to claim 1, characterized in that: The throttling mechanism is a combination of one or more of a throttling valve, a capillary tube, a reducer, an orifice plate or a nozzle.

5. The cryocatheter according to claim 1, characterized in that: 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 refrigeration capacity Q that can be generated after the multi-stage throttling. The maximum refrigeration 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 that can be generated after multi-stage throttling is not less than Q t , after multi-stage throttling, the fluid temperature does not exceed T t , the throttling level selected by the system meets the requirements.

6. The cryocatheter according to claim 1, characterized in that: One or more pre-cooling mechanisms are arranged in the air intake passage.

7. The cryocatheter according to claim 6, characterized in that: The precooling mechanism is connected to the cold supply module, and the precooling temperature of the precooling mechanism is adjustable.

8. The cryocatheter according to claim 7, characterized in that: The cooling capacity of the cooling supply module of the freezing pipe meets the following formula: Among them, w is the cooling capacity supplied to the module by each stage of precooling mechanism, f is the thermal efficiency of each stage of precooling mechanism, and △u is the precooling capacity of refrigerant supplied by each stage of precooling mechanism.

9. The cryocatheter according to claim 7, characterized in that: The precooling 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 immersed heat exchanger.

10. The cryocatheter according to claim 9, characterized in that: The cold supply module includes at least one of a micro semiconductor refrigeration precooling module, a cold storage precooling module, a throttling precooling module, and a phase change precooling module.

11. The cryocatheter according to claim 6, characterized in that: The number of the precooling mechanisms is one more than the number of the throttling mechanisms.

12. The cryocatheter according to claim 6, characterized in that: The precooling amount of the refrigerant supplied by the precooling mechanism is less than the critical precooling amount of the refrigerant phase change: Δu1=q m [f(P1,T1)-f(P0,T0)]<Δu0 Among them, △u1 is the precooling amount of refrigerant supplied by the first-level precooling mechanism, △u0 is the critical precooling amount of refrigerant phase change, q m is the fluid mass flow rate, f(P1, T1) and fP0, T0) are the energy values ​​of the refrigerant before and after passing through the first-stage precooling mechanism.

13. The cryocatheter according to claim 6, characterized in that: The dryness of the refrigerant in the freezing pipe before and after 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 dryness of the refrigerant in the multi-stage throttling refrigeration pipe after being throttled by the last stage throttling mechanism.

14. The cryocatheter according to claim 6, characterized in that: A cold storage cavity is arranged in the tube cavity of the freezing conduit, the cold storage cavity is sleeved outside the precooling mechanism, and antifreeze cold storage liquid is filled in the cold storage cavity.

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