A virtual TIPS calculation method

Abstract

The present invention discloses a virtual TIPS calculation method, which relates to the field of medical technology, including obtaining CTA image data and ultrasound data of patients; completing three-dimensional reconstruction of the portal vein system based on the image data; virtually implanting a stent to obtain a "virtual TIPS" postoperative model; estimating the portal vein flow after TIPS surgery according to a linear model; completing a "virtual TIPS" numerical simulation, analyzing hemodynamic data, and guiding the clinic to select the best treatment method. The present invention realizes the numerical simulation of "virtual TIPS" and analyzes the TIPS effects of different surgical plans, which can provide clinicians with more abundant decision support information before surgery. By calculating the hemodynamic data of patients before TIPS surgery, the portal vein blood flow after the patient's stent is implanted can be obtained. By completing the computer numerical simulation of the virtual TIPS surgery, the relevant hemodynamic parameters of the patient after the virtual stent is implanted can be obtained, guiding the clinic to select a suitable stent and an appropriate implantation method.

Description

Technical Field

[0001] The present invention relates to the field of medical technology, and in particular to a virtual TIPS calculation method. Background Art

[0002] The efficacy of TIPS (transjugular intrahepatic portosystemic shunt) surgery is closely related to the changes in hemodynamics of the liver circulation after TIPS surgery. The shunt channel and shunt volume are the key factors that determine the postoperative efficacy. If the shunt volume is too small, it cannot effectively reduce the portal vein pressure and is prone to thrombosis and blockage in the stent (studies have shown that the thickness of the thrombus layer on the inner wall of the artificial blood vessel is closely related to the blood flow), affecting the long-term patency of the stent. If the shunt volume is too large, it is easy to cause insufficient blood supply to the liver and lead to hepatic encephalopathy. Therefore, the appropriate shunt volume, that is, optimizing the shunt volume of the TIPS stent, is the key to avoiding complications of the shunt channel after TIPS surgery.

[0003] However, so far, clinicians have used stents of uniform specifications in most cases and selected the location of stent placement based on personal experience, but the portal vein pressure varies significantly among patients with portal hypertension. In addition, the vascular configuration, diameter, and angle between vessels of patients with portal hypertension vary significantly, and the significant difference in geometric configuration will inevitably lead to significant differences in the hemodynamic environment of the portal vein after the implantation of stents of the same specifications. Therefore, it is crucial to select the appropriate stent and its implantation location for specific patients before surgery to achieve precise blood pressure reduction, which is crucial to reduce various complications after TIPS surgery and improve the long-term quality of life of patients.

[0004] With the advancement of science and technology, numerical simulation has been widely used as an auxiliary tool in the field of clinical treatment. In particular, the "virtual surgical planning" technology uses numerical simulation software and various medical imaging data to reconstruct the patient's postoperative hemodynamic environment in the computer, helping doctors to formulate personalized optimal treatment plans based on the simulation results. This technology has shown its advantages in the treatment of cardiovascular diseases. For example, before congenital heart disease surgery, virtual surgery can be used to design the most suitable geometry of transplanted organs; researchers such as Li Mou even used virtual surgery to determine the optimal treatment strategy for patients with pancreaticoduodenal artery aneurysms. However, in the treatment of portal vein system diseases, related research has rarely been reported, which may be related to the complex boundary conditions of the portal vein system that restrict the in-depth research. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a virtual TIPS calculation method.

[0006] The objective of the present invention is achieved through the following technical solutions: The present invention discloses a virtual TIPS calculation method, comprising the following steps: S1. Obtain the patient's CTA imaging data and ultrasound data; S2, complete the three-dimensional reconstruction of the portal vein system based on the imaging data; S3, virtual stent implantation to obtain a "virtual TIPS" postoperative model; S4. Estimation of portal vein flow after TIPS based on linear model; S5. Complete the numerical simulation of "virtual TIPS", analyze the hemodynamic data, and guide the clinician to select the best treatment method.

[0007] Further, step S2 specifically includes: obtaining geometric parameters of extrahepatic blood vessels and intrahepatic blood vessels, including diameter and length, according to CTA image data, and then dividing the intrahepatic blood vessels into portal vein branch veins, venous vessels, capillaries, hepatic sinusoidal vessels, hepatic venous vessels and hepatic veins; using the formula Calculate the vascular resistance R of each blood vessel segment using the formula Calculate the blood inertia force of each blood vessel , through the formula Calculate the vascular compliance of each vessel segment ,in Represents the density of blood, is the length of each blood vessel segment, r is the radius of each blood vessel segment, is the pulse velocity, The dynamic viscosity coefficient of blood is expressed; a zero-dimensional mathematical model of the liver circulation system before TIPS surgery is obtained; a circuit path is created between the portal vein branch veins and the hepatic veins to obtain a zero-dimensional mathematical model of the liver circulation system after TIPS surgery.

[0008] Preferably, step S3 specifically includes: converting the circuit of the intrahepatic blood vessels, including the portal vein network, hepatic sinusoids, hepatic vein network and hepatic vein branches, into a RCLR parameter model through circuit theory, and obtaining the exit boundary R parameter value, wherein the TIPS stent is connected from the portal vein branch to the hepatic vein trunk; connecting the distal end of the portal vein branch in the three-dimensional model reconstructed before or after TIPS surgery to the RCLR parameter model, and then merging into the hepatic vein; setting the pressure at the TIPS outlet to zero to directly reflect the value of PCG; in the virtual model after TIPS surgery, establishing a TIPS stent, with its two ends respectively connected to the right branch of the portal vein and the hepatic vein trunk, to obtain a multi-scale coupling model.

[0009] Preferably, step S3 further comprises: performing numerical simulation on the multi-scale model to obtain hemodynamic parameters , and then through the actual clinical measurement data With formula Calculation parameters ; If the parameter <0.05, it is considered that there is no significant difference between the numerical simulation results and the clinical measurement data, that is, the obtained export boundary R parameter value is reasonable, and it is applied to the "virtual TIPS" numerical simulation; represents the flow rate of the left portal vein, represents the flow rate of the right portal vein, Represents PCG, used to calibrate parameters and parameters The value of .

[0010] Preferably, step S4 specifically includes: changing the patient's portal vein flow rate and using it as the inlet boundary condition after TIPS surgery to perform a preliminary "virtual TIPS" numerical simulation, using the formula Calculate the portal vein flow after TIPS surgery, where is the postoperative portal vein flow, Indicates the influence of preoperative portal vein flow on postoperative portal vein flow assessment, represents the preoperative portal vein flow, Indicates the effect of total intrahepatic resistance on portal vein flow assessment after TIPS surgery. represents the preoperative portal vein pressure gradient, To show the effect of implanted stent resistance on portal vein flow assessment after TIPS surgery.

[0011] Preferably, step S5 specifically includes: using the formula and the continuity equation A "virtual TIPS" numerical simulation was performed, in which represents the velocity vector of the fluid, represents the pressure of the fluid, Represents the density of blood, is a vector differential operator; by the formula Calculate the dynamic viscosity of blood ,in represents the shear rate, λ=3.313s, n=0.3568, , .

[0012] The beneficial effects of the present invention are: 1) The present invention proposes a method for estimating the portal vein flow of patients after TIPS surgery before TIPS surgery, realizes the numerical simulation of "virtual TIPS", and analyzes the TIPS effects of different surgical plans, which can provide clinicians with more abundant decision support information before surgery.

[0013] 2) The present invention can obtain the portal vein blood flow of patients after stent implantation by calculating the hemodynamic data of patients before TIPS surgery.

[0014] 3) The present invention can obtain relevant hemodynamic parameters (pressure, flow distribution, etc.) of patients after stent implantation by realizing computer numerical simulation of virtual TIPS surgery, thereby guiding the clinical selection of appropriate stents and appropriate implantation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of a virtual TIPS calculation method according to an embodiment of the present invention; Figure 2 A schematic diagram of a liver circulation lumped parameter model of a virtual TIPS calculation method according to an embodiment of the present invention; Figure 3 A schematic diagram of a lumped parameter model of liver circulation with a TIPS channel in a virtual TIPS calculation method according to an embodiment of the present invention; Figure 4 A simplified lumped model schematic diagram with RCLR parameters of a virtual TIPS calculation method according to an embodiment of the present invention; Figure 5 A schematic diagram of a simplified RCLR parameter model with a TIPS channel in a virtual TIPS calculation method according to an embodiment of the present invention; Figure 6 A schematic diagram of a multi-scale model of liver circulation in a virtual TIPS calculation method according to an embodiment of the present invention; Figure 7 A schematic diagram of a multi-scale model of liver circulation with a TIPS channel in a virtual TIPS calculation method according to an embodiment of the present invention; Figure 8 Schematic diagram of the correlation between PCG and clinical measurement results after the “virtual TIPS” surgery in an embodiment of the present invention, wherein (a) is a schematic diagram of the PCG results of the virtual TIPS at 1.5 times the preoperative blood flow, (b) is a schematic diagram of the PCG results of the virtual TIPS at 1.8 times the preoperative blood flow, and (c) is a schematic diagram of the PCG results of the virtual TIPS at 2.1 times the preoperative blood flow; Fig. 9 This is a schematic diagram of the correlation analysis between PCG and clinical invasive measurement results after the "virtual TIPS" surgery according to an embodiment of the present invention; Fig.10 This is a schematic diagram of the effects on PCG when the implantation distance is 1 cm and the stent diameters are 6 mm, 8 mm, and 10 mm, and when the stent diameter is 8 mm and the implantation distances are 2 cm and 3 cm, respectively, according to an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0017] The present invention discloses a virtual TIPS calculation method, in which the flow of blood in the vascular system constitutes a macroscopic fluid system. From the perspective of fluid mechanics, in the cardiovascular system, the heart and blood vessels have a certain degree of elasticity. When the blood flows, the blood vessels show a certain compliance, while the blood shows the characteristics of viscosity and inertia. In view of the complexity of the systemic vascular system, it is impractical to perform a complete finite element mechanical modeling of it. Therefore, drawing on the work of previous researchers, circuit elements are used to effectively replace the corresponding characteristics of blood vessels and blood: blood pressure is analogized to voltage, blood flow is analogized to current, the viscous resistance of blood is analogized to resistance, the inertia of blood flow is analogized to inductance, and the compliance of blood vessels is analogized to capacitance. Based on such a theoretical framework, an analog circuit numerical simulation model composed of circuit elements is constructed, which can use mature circuit analysis technology to study fluid dynamics problems in the cardiovascular system. The flow chart of the present invention is shown as follows. Figure 1 As shown, the specific steps include: S1. Obtain the patient's CTA imaging data and ultrasound data; S2, complete the three-dimensional reconstruction of the portal vein system based on the imaging data; S3, virtual stent implantation to obtain a "virtual TIPS" postoperative model; S4. Estimation of portal vein flow after TIPS based on linear model; S5. Complete the numerical simulation of "virtual TIPS", analyze the hemodynamic data, and guide the clinician to select the best treatment method.

[0018] Exemplarily, step S2 specifically includes: establishing a zero-dimensional mathematical model of liver circulation, obtaining geometric parameters of extrahepatic blood vessels and intrahepatic blood vessels, such as diameter and length, based on CTA image data, and then dividing the intrahepatic blood vessels into portal vein branch veins, venous vessels, capillaries, hepatic sinusoidal vessels, hepatic venous vessels and hepatic veins; using the formula Calculate the vascular resistance R of each blood vessel segment using the formula Calculate the blood inertia force of each blood vessel , through the formula Calculate the vascular compliance of each vessel segment ,in Represents the density of blood, is the length of each blood vessel segment, r is the radius of each blood vessel segment (according to calculus theory, any blood vessel can be infinitely divided into a finite number of small circular tubes with equal diameters), is the pulse velocity, represents the dynamic viscosity coefficient of blood. In this embodiment =0.004Pa∙s, and a zero-dimensional mathematical model of the liver circulation system before TIPS surgery was obtained. Its structural diagram is shown in Figure 2 As shown, is the hepatic venous flow, is the portal vein flow; the TIPS surgical treatment plan is to create a shunt channel between the portal vein branch and the hepatic vein branch, while other blood vessels are not treated. Therefore, it is assumed that after the TIPS operation, the anatomical characteristics of all blood vessels in the hepatic circulatory system have not changed, and a circuit pathway is created between the portal vein branch vein vessels and the hepatic vein vessels. In this method, the TIPS stent is connected to the right branch of the portal vein and the main trunk of the hepatic vein, respectively, to obtain a zero-dimensional mathematical model of the hepatic circulatory system after the TIPS operation, and its structural schematic diagram is shown in the figure. Figure 3 shown.

[0019] Exemplarily, step S3 specifically includes: establishing a "virtual TIPS" multi-scale coupling model, converting the circuit of the intrahepatic blood vessels, including the portal vein network, hepatic sinusoids, hepatic vein network and hepatic vein branches, into an RCLR parameter model through circuit theory, and obtaining the R parameter value of the outlet boundary. The schematic diagram of the simplified lumped model with RCLR parameters is shown in FIG. Figure 4 The simplified RCLR parameter model with TIPS channel is shown in Figure 5 As shown, C is the capacitor, L is the inductor, and the TIPS stent is connected from the portal vein branch to the main trunk of the hepatic vein; in order to incorporate the anatomical structure of the portal vein system into this method, a three-dimensional model is established, and the distal end of the portal vein branch in the TIPS pre-operative (or post-operative) model is connected to the RCLR parameter model, which simulates the resistance of intrahepatic blood flow, vascular compliance and blood flow inertia, and then flows into the hepatic vein; the pressure at the TIPS outlet is set to zero, so that the portal vein pressure value obtained by three-dimensional numerical simulation directly reflects the value of PCG; in the virtual model after TIPS surgery, the TIPS stent is established by mimics software (established as a round straight tube in this method), and its two ends are connected to the right branch of the portal vein and the main trunk of the hepatic vein respectively (the specific form of its connection with the hepatic vein is not shown in this method). Based on the above settings, a multi-scale coupling model is constructed. The schematic diagram of the multi-scale model of liver circulation is shown in the figure. Figure 6 The schematic diagram of the multiscale model of liver circulation with TIPS channel is shown in Figure 7 As shown, is the splenic vein flow, is the flow rate of the superior mesenteric vein.

[0020] Specifically, step S3 also includes: obtaining the R parameter value of the outlet boundary condition according to the hemodynamic parameters before TIPS surgery, firstly performing numerical simulation on the multi-scale model to obtain the hemodynamic parameters ,in sim To simulate the results, we used actual clinical measurement data With formula Calculation parameters ,in meas is the actual measurement result; if the parameter <0.05 (required to ensure Maintained at a sufficiently low level), it is considered that there is no significant difference between the numerical simulation results and the clinical measurement data, that is, the obtained export boundary R parameter value is reasonable, and it is applied to the "virtual TIPS" numerical simulation; represents the flow rate of the left portal vein, represents the flow rate of the right portal vein, Represents PCG, PCG is the portal caval pressure gradient, used to correct parameters (include Figures 4 to 7 In ) and parameters (include Figures 4 to 7 In ) value; <0.05, and these parameter values ​​are used in the “virtual TIPS” numerical simulation.

[0021] Specifically, step S4 includes: after TIPS surgery, due to the implantation of the stent into the liver circulation, the blood flow velocity of the portal vein will increase to varying degrees, and obtaining accurate post-TIPS flow is the key to accurately predict PCG. Therefore, firstly, the portal vein flow of all patients was changed to varying degrees according to the literature, and it was used as the inlet boundary condition after TIPS surgery to perform a preliminary "virtual TIPS" numerical simulation. Then, through the formula Calculate the portal vein flow after TIPS surgery, where is the postoperative portal vein flow, Indicates the influence of preoperative portal vein flow on postoperative portal vein flow assessment, represents the preoperative portal vein flow, Indicates the effect of total intrahepatic resistance on portal vein flow assessment after TIPS surgery. represents the preoperative portal vein pressure gradient, The effect of the resistance of the implanted stent on the assessment of portal vein flow after TIPS surgery is shown. This model can estimate the portal vein flow after TIPS surgery based on the patient's hemodynamic parameters before TIPS surgery. According to the principle of circuit theory, after adding a parallel resistor to the original circuit, the change in the total current is related to the total current before the parallel resistor is added, the total resistance, and the newly added parallel resistor. In this method, these three correspond to the portal vein flow before TIPS surgery, the total intrahepatic resistance, and the resistance of the implanted stent.

[0022] Preferably, step S5 specifically includes: using the formula and the continuity equation A "virtual TIPS" numerical simulation was performed, in which represents the velocity vector of the fluid, represents the pressure of the fluid, Represents the density of blood, is a vector differential operator; by the formula Calculate the dynamic viscosity of blood ,in represents the shear rate, λ=3.313s, n=0.3568, , .

[0023] For example, after implantation of the TIPS stent, the portal vein flow rate will increase to varying degrees. The preoperative portal vein flow rate of all patients was enlarged by 1.5 times, 1.8 times, and 2.1 times respectively as the inlet boundary conditions of the "virtual TIPS" numerical simulation. The PCG results are as follows: Figure 8 As shown, (a) is a schematic diagram of the PCG results of the virtual TIPS under the condition of 1.5 times the preoperative blood flow, (b) is a schematic diagram of the PCG results of the virtual TIPS under the condition of 1.8 times the preoperative blood flow, and (c) is a schematic diagram of the PCG results of the virtual TIPS under the condition of 2.1 times the preoperative blood flow; as the flow rate increases, the PCG also gradually increases, but no matter how many times it is magnified, a more accurate PCG cannot be obtained. This shows that for PH patients, there are also personalized differences in the portal vein flow after TIPS. Therefore, in this embodiment, 27 patients were randomly selected from 42 patients, and a linear model was developed. The model can estimate the portal vein flow after TIPS based on the hemodynamic parameters of the patients before TIPS surgery. According to the principle of circuit science, after adding a parallel resistor to the original circuit, the change in the total current is related to the total current, total resistance and newly added parallel resistor before the addition of the parallel resistor. These three correspond to the portal vein flow before TIPS surgery, the total intrahepatic resistance and the resistance of the implanted stent. Then, through the formula Calculate the portal vein flow after TIPS surgery, where is the postoperative portal vein flow, Indicates the influence of preoperative portal vein flow on postoperative portal vein flow assessment, represents the preoperative portal vein flow, Indicates the effect of total intrahepatic resistance on portal vein flow assessment after TIPS surgery. represents the preoperative portal vein pressure gradient, The effect of the resistance of the implanted stent on the evaluation of portal vein flow after TIPS surgery is shown in the figure. The correlation analysis results of PCG after "virtual TIPS" surgery and clinical invasive measurement results are shown in the figure. Fig. 9 As shown, The value of was obtained by linear fitting the data of the above 27 patients. .

[0024] For example, when the implantation distance is 1 cm, the stent diameters are 6 mm, 8 mm, and 10 mm respectively; when the stent diameter is 8 mm, the effect on PCG at the implantation distances of 2 cm and 3 cm respectively is shown in the figure. Fig.10 As shown in the figure, the horizontal axis P1-P5 represents the cases. The analysis results show that the larger the distance, the higher the PCG value, which means the less obvious the antihypertensive effect. Taking case P2 as an example, when using an 8 mm diameter stent, when the implantation position was 1 cm, 2 cm, and 3 cm away from the portal vein bifurcation, the PCG dropped to 5.40 mmHg, 6.71 mmHg, and 8.80 mmHg, respectively. Except for case P3, the different implantation positions of the remaining patients led to significant differences in PCG after TIPS surgery.

[0025] Finally, Table 1 also shows the effect of implanting 8 mm equal diameter stents in different portal vein branches on PCG and the results of the minimum stent diameter required to reduce blood pressure to clinical requirements. The results show that for case P3, the PCG after stent implantation in the left portal vein was slightly lower than that in the right portal vein, while in other cases, when the stent was located in the left portal vein, the PCG was significantly higher than that in the right portal vein, with an average difference of more than 32%.

[0026] Table 1: Effects of 8 mm equal diameter stents implanted into different portal vein branches on PCG and the minimum stent diameter required to reduce blood pressure to clinical requirements The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A virtual TIPS calculation method, characterized in that: The following steps are involved: S1. Obtain the patient's CTA imaging data and ultrasound data; S2, complete the three-dimensional reconstruction of the portal vein system based on the imaging data; S3, virtual stent implantation to obtain a "virtual TIPS" postoperative model; S4. Estimation of portal vein flow after TIPS based on linear model; S5. Complete the "virtual TIPS" numerical simulation, analyze the hemodynamic data, and guide the clinician to select the best treatment method.

2. A virtual TIPS calculation method according to claim 1, characterized in that: Step S2 specifically includes: obtaining geometric parameters of extrahepatic and intrahepatic blood vessels, including diameter and length, based on CTA image data, and then dividing the intrahepatic blood vessels into portal vein branch veins, venules, capillaries, hepatic sinusoids, hepatic venules and hepatic veins; using the formula Calculate the vascular resistance R of each blood vessel segment using the formula Calculate the blood inertia force of each blood vessel segment , through the formula Calculate the vascular compliance of each vessel segment ,in Represents the density of blood, is the length of each blood vessel segment, r is the radius of each blood vessel segment, is the pulse velocity, The dynamic viscosity coefficient of blood is expressed; a zero-dimensional mathematical model of the liver circulation system before TIPS surgery is obtained; a circuit path is created between the portal vein branch veins and the hepatic veins to obtain a zero-dimensional mathematical model of the liver circulation system after TIPS surgery.

3. A virtual TIPS calculation method according to claim 2, characterized in that: Step S3 specifically includes: converting the circuit of the intrahepatic blood vessels, including the portal vein network, hepatic sinusoids, hepatic vein network and hepatic vein branches, into a RCLR parameter model through circuit theory, and obtaining the exit boundary R parameter value, wherein the TIPS stent is connected from the portal vein branch to the hepatic vein trunk; connecting the distal end of the portal vein branch in the three-dimensional model reconstructed before or after TIPS surgery to the RCLR parameter model, and then merging into the hepatic vein; setting the pressure at the TIPS outlet to zero to directly reflect the value of PCG; in the virtual model after TIPS surgery, establishing a TIPS stent, with its two ends respectively connected to the right branch of the portal vein and the hepatic vein trunk, to obtain a multi-scale coupling model.

4. A virtual TIPS calculation method according to claim 3, characterized in that: Step S3 also includes: performing numerical simulation on the multi-scale model to obtain hemodynamic parameters , and then through the actual clinical measurement data With the formula Calculation parameters ; If the parameter <0.05, it is considered that there is no significant difference between the numerical simulation results and the clinical measurement data, that is, the obtained export boundary R parameter value is reasonable, and it is applied to the "virtual TIPS" numerical simulation; represents the flow rate of the left portal vein, represents the flow rate of the right portal vein, Represents PCG, used to calibrate parameters and parameters The value of .

5. A virtual TIPS calculation method according to claim 4, characterized in that: Step S4 specifically includes: changing the patient's portal vein flow rate and using it as the inlet boundary condition after TIPS surgery to perform a preliminary "virtual TIPS" numerical simulation, using the formula Calculate the portal vein flow after TIPS surgery, where is the postoperative portal vein flow, Indicates the influence of preoperative portal vein flow on postoperative portal vein flow assessment, represents the preoperative portal vein flow, Indicates the effect of total intrahepatic resistance on portal vein flow assessment after TIPS surgery. represents the preoperative portal vein pressure gradient, To show the effect of implanted stent resistance on portal vein flow assessment after TIPS surgery.

6. A virtual TIPS calculation method according to claim 5, characterized in that: Step S5 specifically includes: and the continuity equation Perform a "virtual TIPS" numerical simulation, where represents the velocity vector of the fluid, represents the pressure of the fluid, Represents the density of blood, is a vector differential operator; by the formula Calculate the dynamic viscosity of blood ,in represents the shear rate, λ=3.313s, n=0.3568, , .

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