Ultrasonic scalpel energy control method based on vascular tissue model

Abstract

The invention belongs to the technical field of ultrasonic scalpel energy control, and particularly relates to an ultrasonic scalpel energy control method based on a vascular tissue model. According to the method, the blood vessel layering model is established, the mechanical property change of the blood vessel tissue is monitored in real time, the real-time energy loss is accurately calculated, and the real-time output power of the ultrasonic knife system is adjusted in real time according to the real-time loss angle. According to the method, the cavitation, curing and disjunction stages can be judged according to the real-time state of the vascular tissue, energy output is accurately controlled, it is ensured that the large-diameter blood vessel is fully cured, the bursting pressure is increased, and meanwhile thermal damage caused by excessive curing of the small-diameter blood vessel is avoided. The problems that a traditional ultrasonic scalpel system is inaccurate in energy control and poor in adaptability to blood vessels with different diameters can be effectively solved, the heat injury and postoperative bleeding risks in the blood vessel cutting process are remarkably reduced, the operation efficiency is improved, and postoperative recovery of a patient is better facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of ultrasonic surgical knives, and in particular relates to an ultrasonic surgical knives energy control method based on a vascular tissue model. Background Art

[0002] The field of ultrasonic scalpel technology has developed rapidly in recent years and has become an indispensable part of modern surgery. Ultrasonic scalpels use high-frequency ultrasonic vibrations to cut and coagulate tissues through cavitation and thermal effects. When the ultrasonic blade vibrates at a high frequency, microbubbles are generated in the tissue. These bubbles expand and contract rapidly, generating huge energy, thereby cutting the tissue. At the same time, ultrasonic vibrations also generate heat, which coagulates the tissue and reduces bleeding.

[0003] The invention patent with publication number CN113491562B discloses a method for dynamically adjusting the output energy of an ultrasonic scalpel and an ultrasonic surgical scalpel system, wherein the method for dynamically adjusting the output energy of an ultrasonic scalpel mainly includes the following steps: T1 determines the current working mode: the system pre-sets a variety of working modes, such as cutting, coagulation, advanced coagulation, etc.; T2 receives a start signal: when the operator starts the ultrasonic scalpel, the system receives the start signal and enters the corresponding energy output control process according to the current working mode; T3 controls the ultrasonic scalpel to output corresponding ultrasonic energy over time according to the corresponding relationship between the preset energy adjustment ratio and the working time: the system presets different energy adjustment ratios and associates them with the working time. In different time periods, the system controls the output energy of the ultrasonic scalpel according to the preset ratio.

[0004] This method mainly relies on the correspondence between the preset energy adjustment ratio and the working time to achieve dynamic control of the ultrasonic knife energy output. The system outputs different energies in different time periods according to different working modes and preset energy adjustment ratios, avoiding surgical risks caused by the operator's inaccurate grasp of the coagulation time of biological tissues and blood vessels. At the same time, when performing surgery on large blood vessels with a diameter of more than 3 mm or large bleeding sites, it can ensure that the ultrasonic knife can safely and reliably coagulate blood vessels and tissues, improve surgical quality, and reduce surgical risks.

[0005] However, the energy regulation ratio of this method is pre-set and cannot be dynamically adjusted according to the real-time state of the vascular tissue. In addition, no vascular tissue model is established, and energy output cannot be controlled according to the specific parameters of the vascular tissue, resulting in poor adaptability to blood vessels of different diameters.

[0006] Therefore, it is urgent to design a new method to control the output energy of ultrasonic knife. Summary of the invention

[0007] The present invention overcomes the deficiencies of the prior art and provides an ultrasonic surgical knife energy control method based on a vascular tissue model to improve the accuracy of energy output of the ultrasonic surgical knife system and the adaptability to blood vessels of different diameters.

[0008] To achieve the above object, the technical solution adopted by the present invention is: an ultrasonic surgical knife energy control method based on a vascular tissue model, comprising the following steps:

[0009] S1. Establish a vascular layered model; by applying simple harmonic shear stress to different vascular tissues in the model, simulate the impedance Z, viscosity coefficient η and elastic coefficient E of the blood vessels, and establish a vascular tissue parameter lookup table LUT ref ;

[0010] S2. Through actual cutting tests on vascular tissues with different diameters, the clamping force F of the vascular tissue under the ultrasonic knife is obtained. clamp The initial impedance Z0 under the action, the maximum cavitation impedance Z cav_max , minimum cavitation impedance Z cav_min , viscosity coefficient η0 and elastic coefficient E0, for the vascular tissue parameter lookup table LUT in S1 ref Correction is performed to obtain the vascular tissue parameter lookup table LUT real ;

[0011] S3, the ultrasonic knife system outputs energy, drives the ultrasonic knife head to vibrate at high frequency, applies simple harmonic shear stress σ to the blood vessel, and according to the real-time feedback voltage effective value U rms And the effective value of current I rms Calculate the initial impedance Z0 of the blood vessel and the maximum cavitation impedance Z cav_max , minimum cavitation impedance Z cav_min , refer to the vascular tissue parameter lookup table LUT in S2 real The corresponding viscosity coefficient η0 and elastic coefficient E0 are obtained, and the vascular creep model is established;

[0012] S4, according to the vascular creep model established in S3, calculating the tissue deformation γ and strain phase angle δ of the blood vessel under the action of the simple harmonic force σ(t) of the ultrasonic knife head;

[0013] S5, according to the real-time feedback voltage effective value U in S3 rms And the effective value of current I rms , calculate the real-time impedance Z, viscosity coefficient η and elastic coefficient E, establish a piecewise function, and determine the cavitation, maturation and severance stages of the vascular tissue;

[0014] S6, fitting impedance transformation rate and viscoelastic ratio Change rate, calculate the real-time loss angle δ i, calculate the real-time output power W of the real-time ultrasonic knife system total ;

[0015] S7, by real-time adjustment of the real-time output voltage U of the ultrasonic knife system i , adjust the system real-time output power W total .

[0016] Furthermore, in step S3,

[0017] The shear stress formula is: σ(t) = σ0sinωt; the impedance Z calculation formula is Z = U rms / I rms ;

[0018] Where: σ0 is the stress amplitude of the ultrasonic cutter head; ω is the circular vibration frequency of the ultrasonic cutter head, which is consistent with the output frequency of the ultrasonic generator, ω = 2πf.

[0019] Furthermore, in step S3,

[0020] The vascular creep model equation is:

[0021] Where: η0 is the tissue viscosity coefficient, which is a measured value; E0 is the tissue elastic modulus, which is a measured value; γ is the tissue deformation; σ is the stress on the tissue.

[0022] Furthermore, in step S4,

[0023] The calculation formula of the tissue deformation γ is γ(t) = γ0sin(ωt-δ); the calculation formula of the strain phase angle δ is

[0024] Wherein: γ0 is the strain amplitude of the blood vessel; δ is the phase angle of the stress after the strain, which is related to the circular frequency ω of the ultrasonic blade vibration, and the value range of δ is 0<δ<π / 2.

[0025] Furthermore, in step S5,

[0026] After normalizing the viscosity coefficient η and the elastic coefficient E, the obtained piecewise function is:

[0027]

[0028] in: is the real-time impedance change rate of blood vessels with different diameters; is the first threshold of the real-time impedance change rate of blood vessels with different diameters, that is, the impedance change rate threshold at the end of cavitation; is the second threshold of the real-time impedance change rate of blood vessels with different diameters, that is, the impedance change rate threshold at the end of maturation; τ is the ratio of the viscosity coefficient to the elastic coefficient of blood vessels with different diameters, referred to as the viscoelastic ratio, τ = η / E; τth_up is the upper limit of the viscoelastic ratio threshold; τ th_down is the lower limit of the viscoelastic ratio threshold; stage.1, stage.2, and stage.3 correspond to the cavitation, maturation, and severance stages of the vascular tissue, respectively.

[0029] Furthermore, in step 6,

[0030] According to the impedance transformation rate and viscoelastic ratio The rate of change is fitted by curve fitting, and we get and The mapping relationship is

[0031] Where: α is the weighting coefficient of the combined curve.

[0032] Furthermore, in step S6,

[0033] Calculate real-time loss angle δ i The formula is

[0034] Where: N is the number of samples; f i is the real-time operating frequency; τ i is the real-time viscoelastic ratio.

[0035] Furthermore, in step S6,

[0036] pass and The mapping relationship is obtained in real time Thus, the real-time loss angle δ is calculated. The calculation formula of the loss angle δ is:

[0037] Where: τ0 = η0 / E0, which is obtained from the measured values ​​η0 and E0 and stored in the vascular tissue model lookup table LUT real middle.

[0038] Furthermore, in step S6,

[0039] Ultrasonic system real-time output power W total The calculation formula is: total =W cut +W loss +ΔW、W total =(1+cotδ i )(πσ0+F clamp )γ0sinδ i +ΔW、W cut =W loss cotδ i , W loss =∮ S σdγ=(πσ0+Fp )γ0sinδ i ;

[0040] Where: i is the real-time loss angle; F clamp is the measured value of the clamping force; ΔW is the fixed transmission loss; W loss is the energy loss; W cut For cutting energy.

[0041] Furthermore, in step S7,

[0042] The formula for adjusting the output voltage is U i =W total / I;

[0043] Among them: U i is the real-time voltage; I is the constant current at different ultrasonic gears.

[0044] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0045] (1) The present invention establishes a vascular tissue model, monitors the changes in the mechanical properties of vascular tissue in real time, calculates real-time energy loss, and accurately controls the energy output of the ultrasonic scalpel, thereby effectively reducing thermal damage, increasing the vascular bursting pressure, ensuring surgical safety, and facilitating the patient's postoperative recovery.

[0046] (2) By establishing a vascular creep model, calculating the stress and strain phase angles, and obtaining the real-time loss angle, the system output power is calculated and adjusted according to the real-time loss angle to accurately control the energy output and avoid thermal damage caused by excessive energy output. Compared with the existing method that uses a fixed output power and cannot adjust the energy output according to the real-time state of the vascular tissue, which is prone to thermal damage, the present invention ensures accurate energy output by real-time monitoring of the vascular state and avoids incomplete vascular closure.

[0047] (3) According to the real-time monitoring of the blood vessel status, the energy output is adjusted. By judging the cavitation, maturation and severance stage of the blood vessel tissue, the energy output is adjusted in real time to ensure that large-diameter blood vessels are fully matured, while avoiding over-maturation of small-diameter blood vessels, improving the adaptability to blood vessels of different diameters, and avoiding over-maturation or incomplete maturation. Compared with the existing method of using the same method for blood vessels of different diameters, which cannot meet the characteristics of different blood vessels and cause thermal damage or insufficient bursting pressure, the present invention improves the efficiency of blood vessel closure, promotes blood vessel healing, and is beneficial to postoperative recovery.

[0048] (4) The present invention establishes a vascular tissue model and monitors the changes in the mechanical properties of vascular tissue in real time, accurately controls the energy output of the ultrasonic scalpel, effectively reduces thermal damage, increases the vascular bursting pressure, and ensures surgical safety. This technology can effectively solve the problems of inaccurate energy control and poor adaptability to blood vessels of different diameters in traditional ultrasonic scalpel systems. In surgical operations, it can significantly reduce the risk of thermal damage and postoperative bleeding during vascular cutting, improve surgical efficiency, and be more conducive to the patient's postoperative recovery. It has broad application prospects, provides new ideas for the development of ultrasonic scalpel technology, and promotes its wider application in the medical field. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0050] Figure 1 is a flow chart of an ultrasonic surgical knife energy control method based on a vascular tissue model;

[0051] Figure 2 It is a schematic diagram of the structure of the vascular layered model;

[0052] Figure 3 It is a schematic diagram of the structure of the collagen fiber network of blood vessels;

[0053] Figure 4 is a schematic diagram of the impedance curve of the blood vessel cavitation stage under the clamping force;

[0054] Figure 5 is a schematic diagram of the dynamic viscoelastic coefficient curve of the blood vessel under the clamping force;

[0055] Figure 6 It is a schematic diagram of the vascular impedance curve during cutting;

[0056] Figure 7 is a schematic diagram of the dynamic viscoelastic ratio curve of blood vessels under the clamping force;

[0057] Figure 8 It is a schematic diagram of the curve of the change rate of vascular impedance during cutting;

[0058] Fig. 9 It is a schematic diagram of the working frequency curve during the blood vessel cutting process;

[0059] Fig.10 It is a schematic diagram of the curves of the change rate of the vascular dynamic viscoelastic ratio and the impedance change rate;

[0060] Fig.11 It is a schematic diagram of the dynamic stress-strain hysteresis energy curve of the blood vessel under the clamping force. DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0063] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, "multiple" means two or more.

[0064] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0065] The necessary terms and parameters mentioned in the present invention are described below:

[0066] Vascular tissue parameter lookup table: In the field of ultrasonic scalpels, the vascular tissue parameter lookup table is a database that stores the physical parameter information of different types of vascular tissues, mainly including impedance, viscosity coefficient and elastic coefficient, as well as some minor parameter information (not discussed in this invention). The vascular tissue parameter lookup table can help engineers establish vascular tissue models, perform simulations, determine initial model parameters, and calibrate model parameters through actual measurement data to ensure that the model parameters are consistent with the actual situation and adapt to the characteristics of different types of blood vessels.

[0067] Vascular creep model: Vascular tissue is a viscoelastic material, which means that it has both the elasticity of solid materials and the viscosity of liquid materials. When the ultrasonic blade applies a simple harmonic force, the vascular tissue will deform. This deformation is not instantaneous, but gradually increases over time and eventually reaches a stable state. This phenomenon of gradual increase in deformation over time is called "creep". The vascular creep model is based on the viscoelasticity of vascular tissue and describes this deformation behavior through mathematical formulas. The model usually contains two main parameters, namely the viscosity coefficient and the elasticity coefficient. The viscosity coefficient reflects the viscosity of vascular tissue, that is, the ability to resist deformation. The higher the viscosity coefficient, the more difficult it is for vascular tissue to deform; the elasticity coefficient reflects the elasticity of vascular tissue, that is, the ability to recover deformation. The higher the elasticity coefficient, the stronger the ability of vascular tissue to recover deformation. The vascular creep model can predict the degree of deformation of vascular tissue based on the simple harmonic force applied by the ultrasonic blade, and determine whether the vascular tissue is in the cavitation, maturation or severance stage.

[0068] Vascular bursting pressure: refers to the pressure that the blood vessel can withstand after closure. The higher the bursting pressure, the more secure the blood vessel closure and the lower the risk of postoperative bleeding.

[0069] Cavitation, maturation, and severance: These three stages describe the process of ultrasonic knife cutting vascular tissue, and describe the way ultrasonic energy acts on vascular tissue: Cavitation stage: ultrasound forms bubbles in vascular tissue, and the bubble ruptures to produce shock waves, destroying the tissue structure; Maturing stage: The water and protein in the tissue are destroyed by ultrasonic energy, and the tissue gradually becomes solidified; Severance stage: The tissue is completely cut off.

[0070] During the process of cutting blood vessels with an ultrasonic scalpel, the vascular tissue will go through two stages: coagulation and severance. These two stages correspond to different states of the vascular tissue and describe the changes in the final state of the vascular tissue:

[0071] Closure stage: The vascular tissue is completed in the maturation stage, which refers to the process in which changes occur inside the vascular tissue, the vascular wall hardens, and the vascular cavity closes.

[0072] Severance stage: The vascular tissue is completed in the severed stage, which refers to the process in which the vascular tissue is cut off and the vascular lumen is completely disconnected.

[0073] Z: Impedance, which reflects the resistance of vascular tissue to ultrasound.

[0074] η: Viscosity coefficient, reflects the viscosity of vascular tissue.

[0075] E: Elastic coefficient, reflects the elasticity of vascular tissue.

[0076] σ: Shear stress, which is the force exerted by the ultrasonic blade on the vascular tissue.

[0077] ω: Circular frequency, which is the frequency of the ultrasonic blade vibration.

[0078] f: frequency, which is the frequency output by the ultrasonic generator.

[0079] γ: Tissue deformation, which describes the degree of deformation of vascular tissue under the action of ultrasonic knife.

[0080] δ: strain phase angle, which describes the delay of tissue deformation relative to ultrasonic vibration.

[0081] τ: Viscoelastic ratio, which is the ratio of viscosity coefficient to elastic coefficient, reflects the viscoelastic properties of tissue.

[0082] The ultrasonic scalpel energy control method based on the vascular tissue model of the present invention can accurately control energy output, reduce thermal damage, and increase vascular bursting pressure. Therefore, it is suitable for various surgical operations requiring vascular cutting, especially in complex, minimally invasive, high-risk or scenes requiring rapid hemostasis. It can significantly improve surgical efficiency and safety and promote postoperative recovery of patients, including:

[0083] Complex vascular surgery: For complex vascular surgery that requires delicate manipulation and avoids thermal damage and bleeding, such as coronary artery bypass grafting in heart surgery and cerebrovascular surgery, the present invention can provide more precise and safer energy control and improve the success rate of the surgery.

[0084] Minimally invasive surgery: Minimally invasive surgery requires delicate operations in a small space. The precise energy control of the present invention can effectively reduce thermal damage to surrounding tissues and improve surgical safety.

[0085] High-risk surgery: For some high-risk surgeries, such as liver resection, splenectomy, etc., the present invention can effectively reduce the risk of postoperative bleeding and improve patient safety.

[0086] Surgery requiring rapid hemostasis: For some surgeries requiring rapid hemostasis, such as trauma surgery, the present invention can quickly complete blood vessel cutting and improve hemostasis efficiency.

[0087] like Figure 1As shown, the present invention provides an ultrasonic surgical knife energy control method based on a vascular tissue model, characterized in that it includes the following steps:

[0088] S1. Establish a vascular layered model; by applying simple harmonic shear stress to different vascular tissues in the model, simulate the impedance Z, viscosity coefficient η and elastic coefficient E of the blood vessels, and establish a vascular tissue parameter lookup table LUT ref ;

[0089] S2. Through actual cutting tests on vascular tissues with different diameters, the clamping force F of the vascular tissue under the ultrasonic knife is obtained. clamp The initial impedance Z0 under the action, the maximum cavitation impedance Z cav_max , minimum cavitation impedance Z cav_min , viscosity coefficient η0 and elastic coefficient E0, for the vascular tissue parameter lookup table LUT in S1 ref Correction is performed to obtain the vascular tissue parameter lookup table LUT real ;

[0090] S3, the ultrasonic knife system outputs energy, drives the ultrasonic knife head to vibrate at high frequency, applies simple harmonic shear stress σ to the blood vessel, and according to the real-time feedback voltage effective value U rms And the effective value of current I rms Calculate the initial impedance Z0 of the blood vessel and the maximum cavitation impedance Z cav_max , minimum cavitation impedance Z cav_min , refer to the vascular tissue parameter lookup table LUT in S2 real The corresponding viscosity coefficient η0 and elastic coefficient E0 are obtained, and the vascular creep model is established;

[0091] S4, according to the vascular creep model established in S3, calculating the tissue deformation γ and strain phase angle δ of the blood vessel under the action of the simple harmonic force σ(t) of the ultrasonic knife head;

[0092] S5, according to the real-time feedback voltage effective value U in S3 rms And the effective value of current I rms , calculate the real-time impedance Z, viscosity coefficient η and elastic coefficient E, establish a piecewise function, and determine the cavitation, maturation and severance stages of the vascular tissue;

[0093] S6, fitting impedance transformation rate and viscoelastic ratio Change rate, calculate the real-time loss angle δ i , calculate the real-time output power W of the real-time ultrasonic knife system total ;

[0094] S7, by real-time adjustment of the real-time output voltage U of the ultrasonic knife system i , adjust the system real-time output power W total.

[0095] The following is a detailed description of the steps of the ultrasonic surgical knife energy control method based on the vascular tissue model:

[0096] The vascular layered model established in step S1 is as follows: Figure 2 As shown in the figure, the blood vessel is divided into a layered cylindrical tube with a media and an adventitia. The media of the blood vessel contains a large number of elastic fibers and a small number of smooth muscle fibers. It is the main area that determines the elasticity of the blood vessel. The media layer is also the thickest part of the blood vessel wall. The adventitia of the blood vessel is mainly composed of loose connective tissue. Between the intima and the media, and between the media and the adventitia, there is an internal elastic membrane and an external elastic membrane composed of elastic fibers, which serve as the boundary of each membrane layer and play a connecting role.

[0097] The collagen fiber network of blood vessels Figure 3 As shown, simple harmonic shear stress is applied to the blood vessel model to simulate the change curves of blood vessel impedance Z, viscosity coefficient η and elastic coefficient E during blood vessel cutting, which are stored in the blood vessel parameter lookup table LUT ref In the figure, reference values ​​are provided for the fitting curves of the real-time impedance Z, viscosity coefficient η and elastic coefficient E obtained in actual blood vessel cutting.

[0098] In step S2, the clamping force F of the vascular tissue under the ultrasonic knife is obtained by performing actual cutting tests on vascular tissues with different diameters. clamp The initial impedance Z0 under the action, the maximum cavitation impedance Z cav_max , minimum cavitation impedance Z cav_min , viscosity coefficient η0 and elastic coefficient E0, for the vascular tissue parameter lookup table LUT in S1 ref Correction is performed to obtain the vascular tissue parameter lookup table LUT real .

[0099] In step S3, the ultrasonic knife system outputs energy to drive the ultrasonic knife head to vibrate at high frequency, applying simple harmonic shear stress σ to the blood vessel. The shear stress formula is: σ(t)=σ0sinωt;

[0100] Where: σ0 is the stress amplitude of the ultrasonic cutter head; ω is the circular vibration frequency of the ultrasonic cutter head, which is consistent with the output frequency of the ultrasonic generator, ω = 2πf.

[0101] The ultrasonic system uses real-time feedback of the voltage RMS value U rms And the effective value of current I rms Calculate the initial impedance Z0 and maximum cavitation impedance Z of the blood vessel cav_max and the minimum cavitation impedance Z cav_min , the calculation formula of impedance Z is Z=U rms / I rms .

[0102] Initial impedance Z0, maximum cavitation impedance Z cav_max and the minimum cavitation impedance Z cav_min The fitting curve is obtained within the initial 0.8 seconds of the ultrasonic system excitation energy output. Figure 4 shown.

[0103] According to Z0, Z cav_max and Z cav_min In the vascular tissue parameter lookup table LUT real The corresponding viscosity coefficient η0 and elastic coefficient E0 are obtained.

[0104] The vascular creep model is established based on the viscosity coefficient η0 and elastic coefficient E0 of vascular tissue. When the blood vessel is tightened by the clamp, the clamping force F clamp This causes the blood vessels to deform. At this time, the blood vessels are deformed into multi-layer viscoelastic tissues, and the creep model equation is:

[0105] Where: η0 is the tissue viscosity coefficient, which is a measured value; E0 is the tissue elastic modulus, which is a measured value; γ is the tissue deformation; σ is the stress on the tissue.

[0106] In step S4, according to the vascular creep model established in S3, the tissue deformation and strain phase angle δ of the blood vessel under the action of the ultrasonic blade simple harmonic force σ(t) are calculated. The calculation formula for the tissue deformation γ generated by the clamped blood vessel under the action of the sinusoidal alternating stress is γ(t)=γ0sin(ωt-δ); the calculation formula for the strain phase angle δ is

[0107] Wherein: γ0 is the strain amplitude of the blood vessel; δ is the phase angle of the stress after the strain, which is related to the circular frequency ω of the ultrasonic blade vibration, and the value range of δ is 0<δ<π / 2.

[0108] In step S5, according to the effective value U of the voltage fed back by the ultrasonic knife rms And the effective value of current I rms The real-time impedance Z, viscosity coefficient η and elastic coefficient E are calculated, and a piecewise function is established to determine the cavitation, maturation and severance stages of the vascular tissue.

[0109] like Figure 5 As shown in the figure, during the cutting of vascular tissue, the decrease in tissue moisture and the increase in tissue temperature cause the tissue viscosity coefficient η to continue to decrease, and the tissue elasticity coefficient E to continue to increase. The curve of vascular impedance Z is as shown in Figure 6 shown.

[0110] By studying the changing rules of viscosity coefficient η and elastic coefficient E during the cutting process of blood vessels with different diameters, such as Figure 7 As shown, combined with the rate of change of vascular impedance like Figure 8As shown in Figure 2, the three time-related stages of cavitation, maturation and severance in the process of blood vessel cutting can be accurately judged. After normalizing the viscosity coefficient η and the elastic coefficient E, the obtained piecewise function is:

[0111] in: is the real-time impedance change rate of blood vessels with different diameters; is the first threshold of the real-time impedance change rate of blood vessels with different diameters, that is, the impedance change rate threshold at the end of cavitation; is the second threshold of the real-time impedance change rate of blood vessels with different diameters, that is, the impedance change rate threshold at the end of maturation; τ is the ratio of the viscosity coefficient to the elastic coefficient of blood vessels with different diameters, referred to as the viscoelastic ratio, τ = η / E; τ th_up is the upper limit of the viscoelastic ratio threshold; τ th_down is the lower limit of the viscoelastic ratio threshold; stage.1, stage.2, and stage.3 correspond to the cavitation, maturation, and severance stages of the vascular tissue, respectively.

[0112] In step S6, according to the impedance transformation rate and viscoelastic ratio When the loss angle δ remains unchanged, the output power W of the ultrasonic knife system can be adjusted. total The output size is only related to the system frequency f. The operating frequency curve is as follows: Fig. 9 As shown. In the actual blood vessel cutting process, the loss angle δ changes with the system frequency f and the viscoelastic ratio τ. Curves and viscoelastic ratio The rate of change curve, such as Fig.10 As shown, and Perform fitting and obtain and The mapping relationship is

[0113] Wherein: α is the weighting coefficient of the combined curve, and in the present invention, α=0.874.

[0114] In step S6, according to the real-time operating frequency f i and real-time viscoelastic ratio τ i , calculate the real-time loss angle δ i In order to reduce the impact of δ on the accuracy due to real-time sampling error, the real-time working frequency f i and real-time viscoelastic ratio τ i The summed average value is used to calculate the loss angle δ. The specific formula is:

[0115] Where: N is the number of samples, in the present invention, N=10; f i is the real-time operating frequency; τ i is the real-time viscoelastic ratio.

[0116] pass and The mapping relationship is obtained in real time Thus, the real-time loss angle δ can be calculated. The calculation formula of the loss angle δ is:

[0117] Where: τ0 = η0 / E0, which is obtained from the measured values ​​η0 and E0 and stored in the vascular tissue model lookup table LUT real middle.

[0118] According to the real-time loss angle δ i , calculate the real-time output power W of the real-time ultrasonic knife system total In each vibration cycle of the ultrasonic scalpel, the sinusoidal alternating stress of the ultrasonic scalpel causes the vascular tissue to deform and the temperature to rise very quickly. clamp When , the tissue is compressed and hardened, and the hysteresis closed curve drifts to the right due to the pressure load.

[0119] The area of ​​the hysteresis closed curve is the energy W lost by the vascular tissue in the form of heat during each vibration cycle. loss The specific formula is W loss =∮ S σdγ=(πσ0+F p )γ0sinδ i .

[0120] The hysteresis energy lost by blood vessels in the form of heat in each vibration cycle is as follows: Fig.11 shown.

[0121] The material modulus G of the blood vessel is the ratio of stress to strain. in: is the storage modulus; is the loss modulus.

[0122] The cutting of tissue by ultrasonic surgical knife can be understood as the high-frequency vibration of the blade causing the cells in the tissue to vibrate at high frequencies, breaking the hydrogen chains of the protein molecules in the tissue cells, and the tissue is cut after solidification. Therefore, the cutting energy corresponding to its storage modulus is W cut It is positively correlated with the coagulation and cutting of tissue, while the loss modulus is reflected as thermal energy W loss It acts on the blade tip and tissue surface and does not have a major impact on cutting; therefore, W cut =W loss cotδ i .

[0123] The ultrasonic scalpel system adjusts the output power W in real time and accurately during the tissue cutting process total , and in this process, the system energy transfer loss ΔW is fixed, W total , W cut , W loss The relationship between the three is as follows: total =W cut +W loss +ΔW、W total =(1+cotδ i )(πσ0+F clamp )γ0sinδ i +ΔW.

[0124] Where: i is the real-time loss angle; F clamp is the measured value of the clamping force; ΔW is the fixed transmission loss.

[0125] In step S7, according to the real-time output power W obtained in step S6, total , real-time adjustment of the ultrasonic knife system real-time output voltage U i , so that the system output power W total The power required for coagulation and severance of vascular tissue is close to that required to avoid thermal damage caused by excessive energy.

[0126] The ultrasonic knife system is a constant current system, and the current remains unchanged during the cutting process. According to the formula U i =W total / I, adjust the output voltage U i Control output power W total Real-time changes;

[0127] Among them: U i is the real-time voltage; I is the constant current at different ultrasonic gears.

[0128] When the present invention is working, first, a vascular layered model is established to simulate the mechanical properties of the blood vessels. This step involves applying simple harmonic shear stress to different vascular tissues in the model, obtaining the impedance, viscosity coefficient and elastic coefficient of the blood vessels through simulation, and establishing a vascular tissue parameter lookup table, which provides the basic parameters of the vascular tissue for subsequent steps.

[0129] Secondly, actual cutting tests were conducted to obtain the initial impedance, maximum cavitation impedance, minimum cavitation impedance, viscosity coefficient, and elastic coefficient of vascular tissues with different diameters under the clamping force of the ultrasonic knife. These parameters will be used to correct and improve the vascular tissue parameter lookup table established in the first step to ensure its accuracy and practicality.

[0130] Next, the ultrasonic scalpel system outputs energy to drive the ultrasonic scalpel head to vibrate at high frequency, applying simple harmonic shear stress to the blood vessels. The system calculates the initial impedance, maximum cavitation impedance, and minimum cavitation impedance of the blood vessels based on the real-time feedback of the effective value of voltage and current, and obtains the corresponding viscosity coefficient and elastic coefficient by referring to the corrected vascular tissue parameter lookup table to establish a vascular creep model. This model is the key to understanding the behavior of blood vessels under the action of the ultrasonic scalpel, and provides a scientific basis for subsequent energy control.

[0131] Subsequently, based on the established vascular creep model, the deformation and strain phase angle of vascular tissue under the simple harmonic force of the ultrasonic scalpel were calculated. This helps to understand the specific response of blood vessels under the action of the ultrasonic scalpel and provides important information for determining the cutting stage of vascular tissue.

[0132] Furthermore, based on the real-time feedback of voltage and current, the real-time impedance, viscosity coefficient and elastic coefficient are calculated, and a piecewise function is established to determine the cavitation, maturation and severance stages of the vascular tissue. This step is the core of achieving precise energy control, and the suitability of energy output is ensured by real-time monitoring of the vascular state.

[0133] Based on the fitting impedance transformation rate and viscoelastic ratio change rate, the real-time loss angle is calculated, and the real-time output power of the real-time ultrasonic knife system is calculated accordingly. This process involves precise control and real-time response to the state of the blood vessels, ensuring that the energy output matches the coagulation and severance requirements of the vascular tissue.

[0134] Finally, the output voltage of the ultrasonic knife system is adjusted in real time to ensure that the system output power meets the power required for coagulation and severance of vascular tissue. This adjustment is achieved through a constant current system, which controls the real-time change of output power by adjusting the output voltage, thereby avoiding thermal damage caused by excessive energy output.

[0135] The entire workflow is a continuous process that is logically connected. From the establishment of the vascular model to the real-time adjustment of energy output, each step provides the necessary information and parameters for achieving more accurate and safer ultrasonic scalpel energy control. Through this process, the present invention can effectively reduce the risk of thermal damage, improve surgical efficiency, and promote postoperative recovery of patients.

[0136] The above is based on the ideal embodiment of the present invention. Through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. An ultrasonic surgical knife energy control method based on a vascular tissue model, characterized in that: The following steps are involved: S1. Establish a vascular layered model; by applying simple harmonic shear stress to different vascular tissues in the model, simulate the impedance Z, viscosity coefficient η and elastic coefficient E of the blood vessels, and establish a vascular tissue parameter lookup table LUT ref ; S2. Through actual cutting tests on vascular tissues with different diameters, the clamping force F of the vascular tissue under the ultrasonic knife is obtained. clamp The initial impedance Z0 under the action, the maximum cavitation impedance Z cav_max , minimum cavitation impedance Z cav_min , viscosity coefficient η0 and elastic coefficient E0, for the vascular tissue parameter lookup table LUT in S1 ref Correction is performed to obtain the vascular tissue parameter lookup table LUT real ; S3, the ultrasonic knife system outputs energy, drives the ultrasonic knife head to vibrate at high frequency, applies simple harmonic shear stress σ to the blood vessel, and according to the real-time feedback voltage effective value U rms And the effective value of current I rms Calculate the initial impedance Z0 of the blood vessel and the maximum cavitation impedance Z cav_max , minimum cavitation impedance Z cav_min , refer to the vascular tissue parameter lookup table LUT in S2 real The corresponding viscosity coefficient η0 and elastic coefficient E0 are obtained, and the vascular creep model is established; S4, according to the vascular creep model established in S3, calculating the tissue deformation γ and strain phase angle δ of the blood vessel under the action of the simple harmonic force σ(t) of the ultrasonic knife head; S5, according to the real-time feedback voltage effective value U in S3 rms And the effective value of current I rms , calculate the real-time impedance Z, viscosity coefficient η and elastic coefficient E, establish a piecewise function, and determine the cavitation, maturation and severance stages of the vascular tissue; S6, fitting impedance transformation rate and viscoelastic ratio Change rate, calculate the real-time loss angle δ i , calculate the real-time output power W of the real-time ultrasonic knife system total ; S7, by real-time adjustment of the real-time output voltage U of the ultrasonic knife system i , adjust the system real-time output power W total .

2. The ultrasonic surgical knife energy control method based on the vascular tissue model according to claim 1 is characterized in that: In step S3, The shear stress formula is: σ(t) = σ0sinωt; the impedance Z calculation formula is Z = U rms / I rms ; Where: σ0 is the stress amplitude of the ultrasonic cutter head; ω is the circular vibration frequency of the ultrasonic cutter head, which is consistent with the output frequency of the ultrasonic generator, ω = 2πf.

3. The ultrasonic surgical knife energy control method based on the vascular tissue model according to claim 2 is characterized in that: In step S3, The vascular creep model equation is: Where: η0 is the tissue viscosity coefficient, which is a measured value; E0 is the tissue elastic modulus, which is a measured value; γ is the tissue deformation; σ is the stress on the tissue.

4. The ultrasonic surgical knife energy control method based on the vascular tissue model according to claim 3 is characterized in that: In step S4, The calculation formula of the tissue deformation γ is γ(t) = γ0sin(ωt-δ); the calculation formula of the strain phase angle δ is Wherein: γ0 is the strain amplitude of the blood vessel; δ is the phase angle of stress after strain, which is related to the circular frequency ω of the ultrasonic blade vibration, and the value range of δ is 0<δ<π / 2.

5. The ultrasonic surgical knife energy control method based on the vascular tissue model according to claim 4, characterized in that: In step S5, After normalizing the viscosity coefficient η and the elastic coefficient E, the obtained piecewise function is: in: is the real-time impedance change rate of blood vessels with different diameters; is the first threshold of the real-time impedance change rate of blood vessels with different diameters, that is, the impedance change rate threshold at the end of cavitation; is the second threshold of the real-time impedance change rate of blood vessels with different diameters, that is, the impedance change rate threshold at the end of maturation; τ is the ratio of the viscosity coefficient to the elastic coefficient of blood vessels with different diameters, referred to as the viscoelastic ratio, τ = η / E; τ th_up is the upper limit of the viscoelastic ratio threshold; τ th_down is the lower limit of the viscoelastic ratio threshold; stage.1, stage.2, and stage.3 correspond to the cavitation, maturation, and severance stages of the vascular tissue, respectively.

6. The ultrasonic surgical knife energy control method based on the vascular tissue model according to claim 5, characterized in that: In step S6, According to the impedance transformation rate and viscoelastic ratio The rate of change is fitted by curve fitting, and we get and The mapping relationship is Where: α is the weighting coefficient of the combined curve.

7. The ultrasonic surgical knife energy control method based on the vascular tissue model according to claim 6, characterized in that: In step S6, Calculate real-time loss angle δ i The formula is Where: N is the number of samples; f i is the real-time operating frequency; τ i is the real-time viscoelastic ratio.

8. The ultrasonic surgical knife energy control method based on the vascular tissue model according to claim 7, characterized in that: In step S6, pass and The mapping relationship is obtained in real time Thus, the real-time loss angle δ is calculated. The calculation formula of the loss angle δ is: Where: τ0 = η0 / E0, which is obtained from the measured values ​​η0 and E0 and stored in the vascular tissue model lookup table LUT real middle.

9. The ultrasonic surgical knife energy control method based on the vascular tissue model according to claim 8, characterized in that: In step S6, Ultrasonic system real-time output power W total The calculation formula is: total =W cut +W loss +ΔW、W total =(1+cotδ i )(πσ0+F clamp )γ0sinδ i +ΔW、W cut =W loss cotδ i , W loss =∮ S σdγ=(πσ0+F p )γ0sinδ i ; Where: i is the real-time loss angle; F clamp is the measured value of the clamping force; ΔW is the fixed transmission loss; W loss is the energy loss; W cut For cutting energy.

10. The ultrasonic surgical knife energy control method based on the vascular tissue model according to claim 9, characterized in that: In step S7, The formula for adjusting the output voltage is U i =W total / I; Among them: U i is the real-time voltage; I is the constant current at different ultrasonic gears.

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