SMV blood distribution calculation method and postoperative hepatic encephalopathy risk assessment method

Abstract

The invention discloses an SMV blood distribution calculation method and a postoperative hepatic encephalopathy risk assessment method, and relates to the technical field of medicines.The method comprises the steps that S1, CTA image data and ultrasonic data of a patient are obtained; s2, performing three-dimensional reconstruction on portal vein system dissection and a TIPS stent; s3, numerical simulation is completed; s4, quantitatively analyzing SMV blood distribution characteristics; s5, SMV blood distribution characteristics are obtained through SMV blood distribution calculation before the TIPS operation, the proportion of SMV blood flowing to the left portal vein branch and the right portal vein branch is analyzed, the position where the stent is implanted is selected, the proportion of SMV blood entering the TIPS stent after the operation is reduced, and the risk of hepatic encephalopathy of the patient after the TIPS operation is evaluated. According to the invention, the flow rule of the SMV blood in the portal vein system can be analyzed, and the volume ratio (percentage) of the SMV blood at any position can be obtained; the'blood ammonia hypothesis' is verified, and the estimation accuracy of the hepatic encephalopathy is improved.

Description

Technical Field

[0001] The present invention relates to the field of medical technology, and in particular to a method for calculating SMV blood distribution and a method for assessing the risk of postoperative hepatic encephalopathy. Background Art

[0002] Portal hypertension, i.e. abnormally high pressure in the portal venous system, is a major consequence of liver cirrhosis. It can lead to serious complications such as bleeding from esophageal and gastric varicose veins and refractory pleural effusions and ascites. Transjugular intrahepatic portosystemic shunt (TIPS) is a minimally invasive procedure performed under angiographic guidance. The goal of the procedure is to implant a covered stent in the left branch, right branch or trunk of the portal vein to create a shunt channel from the portal vein to the hepatic vein. In this way, part of the portal vein blood can directly enter the hepatic vein and then flow into the inferior vena cava, thereby reducing the pressure in the portal vein.

[0003] TIPS (transjugular intrahepatic portosystemic shunt) is a minimally invasive and precise surgery that can significantly relieve portal hypertension and has become the most widely used treatment method in clinical practice. However, within one year after TIPS stent implantation, up to 35%-55% of patients will develop hepatic encephalopathy (HE). Hepatic encephalopathy, also known as hepatic coma, is a syndrome characterized by dysfunction of the central nervous system. Its main symptoms include decreased level of consciousness, abnormal behavior, and coma. If effective treatment is not carried out in time, the condition may worsen, leading to dysfunction of multiple systems such as the patient's nervous, digestive, blood, and endocrine systems, seriously affecting the patient's quality of life. Therefore, for patients with cirrhosis and portal hypertension, preventing hepatic encephalopathy after TIPS surgery is a key factor in maintaining their long-term quality of life.

[0004] Although the exact mechanism of hepatic encephalopathy after TIPS surgery has not been fully clarified, it is generally believed that it is closely related to changes in the hemodynamics of the portal vein system after surgery. The portal vein blood flow is formed by the convergence of the superior mesenteric vein and the splenic vein. The splenic vein is rich in hormones that promote hepatocyte proliferation, such as insulin and glucagon; while the superior mesenteric vein carries nutrients and harmful substances absorbed from the intestine, such as blood ammonia. Under normal physiological conditions, this blood flows into the liver through the left and right portal veins, and blood ammonia is biotransformed by synthesizing urea and glutamine. However, TIPS surgery causes part of the portal vein blood flow to bypass the liver and directly enter the hepatic vein. In particular, the blood in the superior mesenteric vein rich in blood ammonia flows into the systemic circulation without being processed by the liver, and eventually reaches the brain, destroying the blood-brain barrier, which is considered to be the main cause of hepatic encephalopathy. Therefore, in-depth exploration of the changes in the hemodynamics of the portal vein system before and after TIPS surgery, especially the distribution characteristics of the blood in the superior mesenteric vein, is of vital significance for preventing hepatic encephalopathy after TIPS surgery.

[0005] At present, ultrasound and portal vein angiography are mainly used clinically to analyze the blood flow pattern of the portal vein system and the blood distribution characteristics of the superior mesenteric vein. These methods provide important support for optimizing the TIPS technical scheme, significantly improve the success rate and safety of TIPS surgery, and help effectively reduce the risk of hepatic encephalopathy in patients. However, ultrasound examination may be limited by factors such as patient body size and intestinal gas interference, and portal vein angiography, as an invasive examination, has certain risks and potential complications. More importantly, whether it is ultrasound or portal vein angiography, they can only qualitatively analyze the flow distribution of SMV and SV in the portal vein, and cannot accurately quantify the specific distribution of SMV in the left and right portal veins. Therefore, in order to more accurately evaluate the hemodynamic changes before and after TIPS surgery, especially the quantitative distribution characteristics of SMV in the portal vein system, more accurate and safe evaluation methods are urgently needed. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a method for calculating SMV blood distribution and a method for assessing the risk of postoperative hepatic encephalopathy.

[0007] The objective of the present invention is achieved through the following technical solutions: In a first aspect, the present invention discloses a method for calculating SMV blood distribution, comprising the following steps: S1. Obtain the patient's CTA imaging data and ultrasound data; S2, 3D reconstruction of the portal venous system anatomy and TIPS stent; S3, complete the numerical simulation; S4. Quantitative analysis of SMV blood distribution characteristics.

[0008] Based on the first aspect, step S2 specifically includes: reconstructing the three-dimensional anatomical model before and after TIPS surgery based on the patient's CTA data, including the portal vein trunk, the left branch of the portal vein, the right branch of the portal vein, the superior mesenteric vein and the splenic vein. The three-dimensional anatomical model after TIPS surgery also includes a TIPS stent; all entrances and exits on the model are extended by 10 times their diameters, meshed by Ansys ICEM software, selecting the unstructured mesh type, and setting the mesh size to 1 / 15 of the portal vein diameter; the mesh near the blood vessel wall is encrypted, and 6 boundary layers are set, with a total thickness of 1 / 10 of the model outlet size and a growth rate of 1.2.

[0009] Based on the first aspect, step S3 specifically includes: using the NS equation and the continuity equation A numerical simulation is 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, , , , ,The inlet boundary conditions of the numerical simulation are obtained according to the ,transformation of actual clinical ultrasound data, and the outlet is set as the ,resistance boundary conditions, which are calculated by the portal vein pressure and ,flow.

[0010] Based on the first aspect, step S3 also includes: setting the convergence criteria of the numerical simulation, including the residuals of the mass equation and the momentum equation are both less than 10 -5 .

[0011] Based on the first aspect, step S3 further includes: dividing the results of the numerical simulation into before TIPS surgery and after TIPS surgery; Before TIPS surgery, the ratio of SMV blood in the left portal vein was: R LPV =Q LPV-SMV / Q SMV , Q LPV-SMV =Q LPV *R LPV-SMV , where R LPV is the proportion of SMV blood in the left branch of the portal vein, Q LPV-SMV is the flow rate of SMV blood in the left branch of the portal vein, Q SMV is the total blood flow of the portal venous system SMV, Q LPV is the total blood flow of the left portal vein, R LPV-SMV is the ratio of SMV blood to total blood in the left branch of the portal vein; The proportion of SMV blood in the right branch of the portal vein is: R RPV =Q RPV-SMV / Q SMV , Q RPV-SMV =Q RPV *R RPV-SMV , where R RPV is the proportion of SMV blood in the right portal vein, Q RPV-SMV is the flow rate of SMV blood in the right branch of the portal vein, Q RPV is the total blood flow of the right branch of the portal vein, R RPV-SMV is the ratio of SMV blood to total blood in the right branch of the portal vein; After TIPS surgery, the ratio of SMV blood in the stent is: R Stent =Q Stent-SMV / Q SMV , Q Stent-SMV=Q Stent *R Stent-SMV , where R Stent is the proportion of SMV blood in the TIPS stent, Q Stent-SMV is the blood flow rate of the SMV in the TIPS stent, Q Stent is the total blood flow of the TIPS stent, R Stent-SMV It is the ratio of SMV blood to total blood in the TIPS stent.

[0012] Based on the first aspect, step S4 specifically includes: incorporating a liquid-liquid two-phase flow module to analyze the quantitative distribution characteristics of SMV blood in the portal vein; Phase volume Defined as ,in For the The volume fraction of the phase is given by , No. The effective density of the phase is ,in It is The physical density of the phase; The continuity equation of the phase is , combined volume fraction The equation of the next phase and the continuity equation of the next phase are used to calculate the The volume fraction of the phase, For the Phase speed; The momentum equation for the phase is: ;in is the acceleration due to gravity, It is The stress-strain tensor of the phase is defined as ,in It is The shear viscosity of the phase, It is The bulk viscosity of the phase, T represents the transposition, is the identity matrix, It is the external effect The body force of the phase, It is the external effect The internal lift of the phase, is applied to the The virtual mass force of the phase, It is The drag force of the phase is given by the formula Calculate the drag force, where represents the discrete phase, represents the continuous phase, Continuous phase The drag force, For discrete phase The drag force, For discrete phase The volume fraction of Continuous phase The volume fraction of For discrete phase The physical density of For discrete phase speed, Continuous phase speed, is the particle surface relaxation parameter time, which is calculated as follows: ,in Represents discrete phase The diameter of the droplet, Represents discrete phase Shear viscosity, drag function The calculation method is ,in is the drag coefficient, is the relative Reynolds number, the drag coefficient The calculation method is , relative Reynolds number The calculation method is ,in Continuous phase The physical density of Continuous phase Shear viscosity.

[0013] In a second aspect, the present invention further discloses a method for assessing the risk of postoperative hepatic encephalopathy based on SMV blood distribution calculation, the method comprising the steps of: S5, assessing the risk of hepatic encephalopathy in patients after TIPS surgery by calculating the SMV blood distribution before TIPS surgery; the SMV blood distribution calculation specifically adopts the SMV blood distribution calculation method described above.

[0014] Based on the second aspect, step S5 includes: calculating the SMV blood distribution characteristics before TIPS surgery, analyzing the proportion of SMV blood flowing to the left branch of the portal vein and the right branch of the portal vein, so as to select the location for stent implantation and reduce the proportion of SMV blood entering the TIPS stent after surgery, which is used to evaluate the risk of hepatic encephalopathy in patients after TIPS surgery.

[0015] The beneficial effects of the present invention are: 1) The present invention can quantitatively analyze the distribution characteristics of SMV blood and preliminarily verify the "blood ammonia hypothesis", thereby improving the accuracy of prediction of hepatic encephalopathy.

[0016] 2) The present invention can analyze the flow pattern of SMV blood in the portal vein system and can obtain the volume proportion (i.e. percentage) of SMV blood at any position; by analyzing the ratio of SMV blood flowing to the left branch of the portal vein and the right branch of the portal vein before TIPS surgery, the appropriate position can be selected to implant the stent, thereby reducing the ratio of SMV blood entering the TIPS stent after surgery and evaluating the risk of hepatic encephalopathy in patients after TIPS surgery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of a flow chart of an embodiment of the present invention; Figure 2 A schematic diagram of the results of the SMV blood ratio in the stent after TIPS surgery in the hepatic encephalopathy group and the non-hepatic encephalopathy group according to an embodiment of the present invention; Figure 3 Schematic diagram of a three-dimensional model reconstruction process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] 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.

[0019] The present invention discloses a method for calculating SMV blood distribution, comprising the following steps: S1. Obtain the patient's CTA imaging data and ultrasound data; S2, 3D reconstruction of the portal venous system anatomy and TIPS stent; S3, complete the numerical simulation; S4. Quantitative analysis of SMV blood distribution characteristics.

[0020] Specifically, step S2 specifically includes: reconstructing the three-dimensional anatomical model before and after TIPS surgery based on the patient's CTA data, including the portal vein trunk, the left branch of the portal vein, the right branch of the portal vein, the superior mesenteric vein and the splenic vein. The three-dimensional anatomical model after TIPS surgery also includes a TIPS stent; for the needs of simulation, all inlets and outlets are extended by 10 times their diameters to ensure that the viscous fluid at the inlet can be fully developed and the influence of the recirculation zone is reduced at the outlet. Meshing is performed using Ansys ICEM software, the unstructured mesh type is selected, and the mesh size is set to 1 / 15 of the portal vein diameter; considering the boundary layer effect, the mesh near the blood vessel wall is encrypted, and 6 layers of boundary layers are set, with a total thickness of approximately 1 / 10 of the model outlet size and a growth rate of 1.2. The schematic diagram of the three-dimensional model reconstruction process is shown in FIG. Figure 3As shown in the figure, PV indicates portal vein, SMV indicates superior mesenteric vein, SV indicates splenic vein, LGV indicates left gastric vein, LPV indicates left portal vein, RPV indicates right portal vein, Stent indicates stent, Q SMV is the total blood flow of the portal venous system SMV, R R represents the right portal vein resistance, R L represents the left portal vein resistance, Q SV Represents splenic vein flow.

[0021] Specifically, step S3 specifically includes: in the venous system, the pulsation characteristics of blood flow are not obvious, and in the process of collecting the flow of portal vein by ultrasound examination, it can be found that the blood flow of portal vein is relatively stable; assuming that blood is a continuous homogeneous incompressible non-Newtonian fluid, its dynamic viscosity coefficient Referring to the Carreau-Yasuda model in non-Newtonian fluids, the NS equations and the continuity equation A numerical simulation is performed, in which represents the velocity vector of the fluid, represents the pressure of the fluid, Indicates the density of blood, set to 1050kg / m3, is a vector differential operator; by the formula Calculate the dynamic viscosity of blood , using the Carreau model to describe the dynamic viscosity of blood With shear rate The change of λ=3.313s, n=0.3568, , ,The inlet boundary conditions of the numerical simulation are obtained according to the ,transformation of actual clinical ultrasound data, and the outlet is set as the ,resistance boundary conditions, which are calculated by the portal vein pressure and ,flow.

[0022] Specifically, step S3 also includes: the numerical simulation of hemodynamics is completed in the computational fluid dynamics (CFD) software Ansys Fluent. All calculation processes use the software's default segregated solver, that is, the pressure-based solver. The convergence standard is set to the residuals of the mass and momentum equations are both less than 10-5.

[0023] Specifically, step S3 also includes: dividing the results of numerical simulation into before TIPS surgery and after TIPS surgery for discussion; before TIPS surgery, the SMV blood ratio of the left branch of the portal vein is: R LPV =QLPV-SMV / Q SMV , Q LPV-SMV =Q LPV *R LPV-SMV , where R LPV is the proportion of SMV blood in the left branch of the portal vein, Q LPV-SMV is the flow rate of SMV blood in the left branch of the portal vein, Q SMV is the total flow of SMV blood in the portal vein system (i.e., the total flow of SMV blood in the right and left branches of the portal vein), Q LPV is the total blood flow of the left portal vein, R LPV-SMV The ratio of SMV blood to total blood in the left branch of the portal vein is: R RPV =Q RPV-SMV / Q SMV , Q RPV-SMV =Q RPV *R RPV-SMV , where R RPV is the proportion of SMV blood in the right portal vein, Q RPV-SMV is the flow rate of SMV blood in the right branch of the portal vein, Q RPV is the total blood flow of the right branch of the portal vein, R RPV-SMV It is the ratio of SMV blood to total blood in the right branch of the portal vein. After TIPS surgery, the ratio of SMV blood in the stent is: R Stent =Q Stent-SMV / Q SMV , Q Stent-SMV =Q Stent *R Stent-SMV , where R Stent is the proportion of SMV blood in the TIPS stent, Q Stent-SMV is the blood flow rate of the SMV in the TIPS stent, Q Stent is the total blood flow of the TIPS stent, R Stent-SMV It is the ratio of SMV blood to total blood in the TIPS stent.

[0024] Specifically, step S4 specifically includes: In order to explore the quantitative distribution characteristics of SMV blood in the portal vein, a liquid-liquid two-phase flow module is incorporated. The Eulerian method is used in the model to calculate each phase separately, and the simultaneous equations of mass and momentum conservation are solved, which can provide high-precision simulation results. In order to more effectively apply the Euler two-fluid model to the liquid-liquid two-phase flow problem of the portal vein system, the calculation model is moderately simplified. In this process, the continuity and momentum conservation equations of each phase are solved independently; all phases share the same pressure field; there is no mass and energy exchange between phases; the droplet diameter is fixed, etc. These simplifications help reduce the complexity of the model while maintaining sufficient accuracy to capture the key fluid dynamics characteristics within the portal vein system.

[0025] Specifically, the volume fraction equation and the concept of phase volume fraction are one of the characteristics of the Euler two-fluid model. In this model framework, each phase must ensure that the laws of conservation of mass and momentum are satisfied, ensuring an accurate description of the behavior of each phase in multiphase flow. Phase volume Defined as ,in For the The volume fraction of the phase is given by , No. The effective density of the phase is ,in It is The physical density of the phase.

[0026] Specifically, the continuity equation, The continuity equation of the phase is , combined volume fraction The equation of the next phase and the continuity equation of the next phase are used to calculate the The volume fraction of the phase, For the Phase speed.

[0027] Specifically, the momentum equation, The momentum equation for the phase is: ;in is the acceleration due to gravity, It is The stress-strain tensor of the phase is defined as ,in It is The shear viscosity of the phase, It is The bulk viscosity of the phase, T represents the transposition, is the identity matrix, It is the external effect The body force of the phase, It is the external effect The internal lift of the phase, is applied to the The virtual mass force of the phase, It is The drag of the phase. Since the present invention adopts a liquid-liquid two-phase flow module, the flow in the blood vessel does not need to consider the external volume force. The lift is a very small amount relative to the drag, so it can also be ignored. In addition, the present invention assumes that the blood flowing in from the SMV is the first blood, and the blood flowing in from the splenic vein is the second blood, wherein the material properties of the first blood and the second blood are set to be consistent, the first blood is the first phase, and the second blood is the second phase. The material properties (density and viscosity) of the two phases are set to be the same, so the virtual mass force can also be ignored. Finally, only the influence of the drag needs to be considered.

[0028] Specifically, through the formula Calculate the drag force, where represents the discrete phase, represents the continuous phase, Continuous phase The drag force, For discrete phase The drag force, For discrete phase The volume fraction of Continuous phase The volume fraction of For discrete phase The physical density of For discrete phase speed, Continuous phase speed, is the particle surface relaxation parameter time, which is calculated as follows: ;in Represents discrete phase The diameter of the droplet, Represents discrete phase Shear viscosity, drag function There are some differences in different models, but they all contain a relative Reynolds number , using the Schiller model, the drag function The calculation method is ,in is the drag coefficient, is the relative Reynolds number, the drag coefficient The calculation method is , relative Reynolds number The calculation method is ,in Continuous phase The physical density of Continuous phase Shear viscosity.

[0029] The present invention also discloses a method for assessing the risk of postoperative hepatic encephalopathy based on SMV blood distribution calculation, and a schematic flow chart of the steps is shown in FIG. Figure 1 As shown, the method includes the steps: S5, by calculating the SMV blood distribution before TIPS surgery, assessing the risk of hepatic encephalopathy in patients after TIPS surgery; the SMV blood distribution calculation specifically adopts the SMV blood distribution calculation method described above. Specifically, it includes: calculating the SMV blood distribution before TIPS surgery to obtain the SMV blood distribution characteristics, analyzing the proportion of SMV blood flowing to the left branch of the portal vein and the right branch of the portal vein, so as to select the location for implanting the stent, reduce the proportion of SMV blood entering the TIPS stent after surgery, and assess the risk of hepatic encephalopathy in patients after TIPS surgery.

[0030] Illustratively, the present invention can quantitatively analyze the distribution characteristics of SMV blood and preliminarily verify the "blood ammonia hypothesis", which states that after a large amount of blood ammonia enters the cerebral circulation, it can pass through the blood-brain barrier and be synthesized and processed in the brain. This process consumes a lot of energy, thereby affecting other normal brain functions and ultimately causing hepatic encephalopathy. Multiple animal experiments have confirmed that the blood ammonia concentration in SMV blood is significantly higher than that in other blood vessels. Therefore, excessive SMV blood flows directly into the systemic circulation without liver detoxification, which may be an important cause of the high incidence of hepatic encephalopathy. The results of the proportion of SMV blood in the stent after TIPS surgery in the hepatic encephalopathy group (HE, 33 cases) and the non-hepatic encephalopathy group (N-HE, 12 cases) are shown in the figure below. Figure 2 As shown. It can be seen that after TIPS surgery, the proportion of SMV blood in the stent of patients in the hepatic encephalopathy group was significantly higher than that in the non-hepatic encephalopathy group, and the difference was statistically significant (P<0.001). This result shows that a large amount of SMV blood rich in blood ammonia bypasses the liver's detoxification process and directly enters the systemic circulation, which is likely to be an important mechanism leading to postoperative hepatic encephalopathy. If the proportion of SMV blood directly entering the stent can be reduced, allowing more SMV blood to flow into the liver for detoxification and eliminate blood ammonia, it may help reduce the occurrence of hepatic encephalopathy after TIPS surgery.

[0031] Exemplarily, the present invention can select a suitable position to implant a stent by analyzing the ratio of SMV blood flowing to the left and right branches of the portal vein before TIPS surgery, thereby reducing the ratio of SMV blood entering the TIPS stent after surgery and evaluating the probability of hepatic encephalopathy in patients after TIPS surgery. In patients A and B, the portal vein pressure gradient (PCG) before and after TIPS surgery remained consistent. However, the ratio of SMV blood flowing to the left and right portal veins before surgery was 74.14% and 25.86% (patient A), and 36.08% and 63.92% (patient B), respectively, showing significant differences. After both patients implanted a TIPS stent with a diameter of 8 mm into the right portal vein, the ratio of SMV blood flowing to the stent was observed to be 45.83% (patient A) and 80.54% (patient B), respectively. It is worth noting that patient A did not experience any postoperative complications during the 989-day follow-up period; in contrast, patient B developed hepatic encephalopathy only 27 days after surgery. This indicates that in cases like patient B, if the TIPS stent is placed on the left portal vein branch with less SMV blood, it may help reduce the risk of hepatic encephalopathy. According to the simulation results of the present invention, if the patient adopts this method, the proportion of SMV blood flowing into the stent after surgery can be reduced to 63.56%.

[0032] 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 method for calculating SMV blood distribution, characterized in that: The following steps are involved: S1. Obtain the patient's CTA imaging data and ultrasound data; S2, 3D reconstruction of the portal venous system anatomy and TIPS stent; S3, complete the numerical simulation; S4. Quantitative analysis of SMV blood distribution characteristics.

2. A method for calculating SMV blood distribution according to claim 1, characterized in that: Step S2 specifically includes: reconstructing the three-dimensional anatomical model before and after TIPS surgery based on the patient's CTA data, including the portal vein trunk, the left branch of the portal vein, the right branch of the portal vein, the superior mesenteric vein and the splenic vein. The three-dimensional anatomical model after TIPS surgery also includes the TIPS stent; all entrances and exits on the model are extended by 10 times their diameters, meshed by Ansys ICEM software, selecting the unstructured mesh type, and setting the mesh size to 1 / 15 of the portal vein diameter; the mesh near the blood vessel wall is encrypted, and 6 boundary layers are set, with a total thickness of 1 / 10 of the model outlet size and a growth rate of 1.

2.

3. A method for calculating SMV blood distribution according to claim 2, characterized in that: Step S3 specifically includes: using the NS equation and the continuity equation A numerical simulation is 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, , ,The inlet boundary conditions of the numerical simulation are obtained according to the ,transformation of actual clinical ultrasound data, and the outlet is set as the ,resistance boundary conditions, which are calculated by the portal vein pressure and ,flow.

4. A method for calculating SMV blood distribution according to claim 3, characterized in that: Step S3 also includes: setting the convergence criteria of the numerical simulation, including the residuals of the mass equation and the momentum equation being less than 10 -5 .

5. A method for calculating SMV blood distribution according to claim 4, characterized in that: Step S3 also includes: dividing the results of the numerical simulation into before TIPS surgery and after TIPS surgery; Before TIPS surgery, the ratio of SMV blood in the left portal vein was: R LPV =Q LPV-SMV / Q SMV , Q LPV-SMV =Q LPV *R LPV-SMV , where R LPV is the proportion of SMV blood in the left branch of the portal vein, Q LPV-SMV is the flow rate of SMV blood in the left branch of the portal vein, Q SMV is the total blood flow of the portal venous system SMV, Q LPV is the total blood flow of the left portal vein, R LPV-SMV is the ratio of SMV blood to total blood in the left branch of the portal vein; The proportion of SMV blood in the right branch of the portal vein is: R RPV =Q RPV-SMV / Q SMV , Q RPV-SMV =Q RPV *R RPV-SMV , where R RPV is the proportion of SMV blood in the right portal vein, Q RPV-SMV is the flow rate of SMV blood in the right branch of the portal vein, Q RPV is the total blood flow of the right branch of the portal vein, R RPV-SMV is the ratio of SMV blood to total blood in the right branch of the portal vein; After TIPS surgery, the ratio of SMV blood in the stent is: R Stent =Q Stent-SMV / Q SMV , Q Stent-SMV =Q Stent *R Stent-SMV , where R Stent is the proportion of SMV blood in the TIPS stent, Q Stent-SMV is the blood flow rate of the SMV in the TIPS stent, Q Stent is the total blood flow of the TIPS stent, R Stent-SMV It is the ratio of SMV blood to total blood in the TIPS stent.

6. A method for calculating SMV blood distribution according to claim 5, characterized in that: Step S4 specifically includes: incorporating a liquid-liquid two-phase flow module to analyze the quantitative distribution characteristics of SMV blood in the portal vein; Phase volume Defined as ,in For the The volume fraction of the phase is given by , No. The effective density of the phase is ,in It is The physical density of the phase; The continuity equation of the phase is , combined volume fraction The equation of the next phase and the continuity equation of the next phase are used to calculate the The volume fraction of the phase, For the Phase speed; The momentum equation for the phase is: ;in is the acceleration due to gravity, It is The stress-strain tensor of the phase is defined as ,in It is The shear viscosity of the phase, It is The bulk viscosity of the phase, T represents the transposition, is the identity matrix, It is the external effect The body force of the phase, It is the external effect The internal lift of the phase, is applied to the The virtual mass force of the phase, It is The drag force of the phase is given by the formula Calculate the drag force, where represents the discrete phase, represents the continuous phase, Continuous phase The drag force, For discrete phase The drag force, For discrete phase The volume fraction of Continuous phase The volume fraction of For discrete phase The physical density of For discrete phase speed, Continuous phase speed, is the particle surface relaxation parameter time, which is calculated as follows: ,in Represents discrete phase The diameter of the droplet, Represents discrete phase Shear viscosity, drag function The calculation method is ,in is the drag coefficient, is the relative Reynolds number, the drag coefficient The calculation method is , relative Reynolds number The calculation method is ,in Continuous phase The physical density of Continuous phase Shear viscosity.

7. A method for assessing the risk of postoperative hepatic encephalopathy based on SMV blood distribution calculation, characterized in that: The method comprises the steps of: S5, evaluating the risk of hepatic encephalopathy of patients after TIPS surgery by calculating the SMV blood distribution before TIPS surgery; the SMV blood distribution calculation specifically adopts the SMV blood distribution calculation method as described in any one of claims 1-6.

8. A method for assessing the risk of postoperative hepatic encephalopathy according to claim 7, characterized in that: Step S5 includes: calculating the SMV blood distribution characteristics before TIPS surgery, analyzing the proportion of SMV blood flowing to the left branch of the portal vein and the right branch of the portal vein, so as to select the location for stent implantation and reduce the proportion of SMV blood entering the TIPS stent after surgery, which is used to evaluate the risk of hepatic encephalopathy in patients after TIPS surgery.

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