Blood mixing degree calculation method and postoperative hepatic encephalopathy prediction method

Abstract

The invention discloses a blood mixing degree calculation method and a postoperative hepatic encephalopathy prediction method, and belongs to the technical field of medicines.The method comprises the following 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 the portal vein blood mixing degree; and S5, calculating the blood mixing degree of the patient before the TIPS operation to obtain a portal vein blood mixing degree characteristic which is used for predicting the occurrence risk of hepatic encephalopathy after the TIPS operation so as to assist in clinical decision making. According to the method, the mixing degree of the blood in the portal vein can be quantitatively analyzed, the method is more accurate compared with a traditional qualitative method which depends on portal vein radiography for observation and judgment, the postoperative hepatic encephalopathy risk is estimated by analyzing the mixing degree of the portal vein blood before the TIPS operation, and then TIPS operation treatment of a patient with the high hepatic encephalopathy risk is avoided.

Description

Technical Field

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

[0002] The portal vein is a unique vein in the human body that collects blood from the SMV and splenic vein and delivers it to the liver. It is the main source of blood supply to the liver (accounting for 70% to 80%). A 4Dflow MRI scan was performed on 10 healthy volunteers. The results showed that some subjects had significant spiral flow characteristics in the portal vein; and some subjects had two blood flows in the portal vein that showed a flow pattern of adherent flow. Further quantitative analysis found that the blood from the splenic vein and SMV of healthy volunteers did not mix when they flowed into the portal vein. In previous studies, it was found that patients with portal hypertension also had obvious spiral flow phenomena, and blood from different sources had different distribution trends in different patients. In previous animal studies, some scholars pointed out that the portal veins of some animals have spiral folds. Such fold structures help mix blood and thus make blood perfusion in various parts of the liver uniform. The human portal vein does not have such a spiral structure. Therefore, how the blood in the human portal vein flows, its flow pattern, and whether the blood is mixed are of great significance for future exploration of portal vein system diseases, especially the different effects of blood components of the superior mesenteric vein and splenic vein on the liver. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a method for calculating the degree of blood mixing and a method for predicting the risk of postoperative hepatic encephalopathy.

[0004] 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 the degree of blood mixing, 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 the mixing degree of portal vein blood.

[0005] 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.

[0006] 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, 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.

[0007] 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 .

[0008] 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.

[0009] Based on the first aspect, step S4 further includes: when the SMV blood volume fraction in the unit blood volume is R V_SMV <0.01, the portal vein blood is pure splenic vein blood; when the SMV blood volume fraction per unit blood volume is 0.01≤R V_SMV When the SMV blood volume fraction per unit blood volume is R V_SMV When >0.99, the portal vein blood is pure SMV blood; the calculation method of SMV blood volume fraction is R V_SMV =V SMV / V E , where V SMV is the volume of SMV per unit of blood, V E is the unit blood volume; through the formula Quantitatively obtain the blood mixing degree of the portal vein ,in represents the volume of blood in the portal vein that mixes with the blood in the SMV and splenic veins. Represents the total volume of portal vein blood.

[0010] In a second aspect, the present invention discloses a method for predicting the risk of postoperative hepatic encephalopathy based on a blood mixing degree calculation method, the method comprising the steps of: S5, calculating the blood mixing degree of the patient before TIPS surgery to obtain the portal vein blood mixing degree characteristics, which is used to predict the risk of hepatic encephalopathy after TIPS surgery to assist clinical decision-making; wherein the blood mixing degree calculation specifically adopts the blood mixing degree calculation method described above.

[0011] Based on the second aspect, predicting the risk of hepatic encephalopathy after TIPS surgery through the characteristics of portal vein blood mixing degree includes: before TIPS surgery, selecting patients with high blood mixing degree to undergo TIPS surgery.

[0012] The beneficial effects of the present invention are: 1) The present invention can quantitatively analyze the degree of blood mixing in the portal vein, which is more accurate than the traditional qualitative method relying on portal vein angiography observation and judgment, and can also perform risk analysis on the risk of disease occurrence, thereby improving the clinical treatment effect.

[0013] 2) The present invention estimates the risk of postoperative hepatic encephalopathy by analyzing the degree of portal vein blood mixing before TIPS surgery, thereby avoiding TIPS surgery for patients with high risk of hepatic encephalopathy. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of a process flow of an embodiment of the present invention; Figure 2 This is a schematic diagram of the distribution trend of the degree of blood mixing in the main trunk of the portal vein of each patient before TIPS surgery according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the distribution trend of the degree of blood mixing in the main trunk of the portal vein of each patient after TIPS surgery according to an embodiment of the present invention; Figure 4 is a schematic diagram of a cross section of an embodiment of the present invention; Figure 5 This is a schematic diagram of a prediction curve of the degree of portal vein blood mixing before TIPS surgery for hepatic encephalopathy after TIPS surgery according to an embodiment of the present invention; Figure 6 Schematic diagram of a three-dimensional model reconstruction process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0015] 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.

[0016] The present invention discloses a method for calculating the degree of blood mixing, 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 the mixing degree of portal vein blood.

[0017] Specifically, step S2 specifically includes: reconstructing the three-dimensional anatomical model before and after TIPS surgery based on the patient's CTA data, including vascular pathways such as 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 diameter to ensure that the viscous fluid at the inlet can fully develop and reduce the impact of the recirculation zone at the outlet. The meshing was completed using Ansys ICEM software, and the unstructured mesh type was selected, and the mesh size was set to approximately 1 / 15 of the portal vein diameter. Taking into account the boundary layer effect, the mesh near the blood vessel wall was encrypted, and 6 layers of boundary layers were set. The total thickness was approximately 1 / 10 of the model outlet size, and the growth rate was 1.2. The schematic diagram of the three-dimensional model reconstruction process is shown in the figure. Figure 6As shown in the figure, PV represents portal vein, SMV represents superior mesenteric vein, SV represents splenic vein, LGV represents left gastric vein, LPV represents left portal vein, RPV represents right portal vein, and Stent represents stent. represents the flow rate of the superior mesenteric vein, represents the splenic vein flow, represents the right portal vein resistance, Represents the left portal vein resistance.

[0018] 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 the blood is a continuous homogeneous incompressible non-Newtonian fluid, its dynamic viscosity μ refers to the Carreau-Yasuda model in non-Newtonian fluid, and through 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, Indicates the density of blood, set to 1050 kg / m 3 , is a vector differential operator; the Carreau model is used to describe the hemodynamic viscosity coefficient With shear rate The change of 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 were obtained by transforming the actual clinical ultrasound data, and the outlet was set as the resistance boundary condition, which was calculated by portal vein pressure and flow. The numerical simulation of hemodynamics was completed in the computational fluid dynamics (CFD) software AnsysFluent. All calculations used the software's default segregated solver (SegregatedSolver), which is a pressure-based solver. The convergence criteria for the numerical simulation were set, including the residuals of the mass equation and momentum equation were all less than 10 -5 .

[0019] Based on the first aspect, step S4 specifically includes: assuming that the blood flowing from the SMV is the first blood, and the blood flowing 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. A liquid-liquid two-phase flow module is incorporated to study the quantitative distribution characteristics of SMV blood in the portal vein. In the model, the Eulerian method is used 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, this study moderately simplifies the calculation model. 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 in the portal vein system.

[0020] 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.

[0021] 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.

[0022] 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 first and second phases is set to the same. Finally, only the influence of drag force needs to be considered. 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 There are some differences in different models, but they all contain a relative Reynolds number The present invention adopts 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.

[0023] Specifically, step S4 also includes: Since the blood in different veins comes from different organs, has different functions and metabolites, their blood components naturally have some differences. Exploring the distribution characteristics of splenic vein and SMV blood in the portal vein system is of great significance for the mechanism of portal vein-related diseases. When the SMV blood volume fraction in a unit blood volume is R V_SMV <0.01, the portal vein blood is pure splenic vein blood; when the SMV blood volume fraction per unit blood volume is 0.01≤R V_SMV When the SMV blood volume fraction per unit blood volume is R V_SMV When >0.99, the portal vein blood is pure SMV blood; the calculation method of SMV blood volume fraction is R V_SMV =V SMV / V E , where V SMV is the volume of SMV per unit of blood, V E is the unit blood volume; through the formula Quantitatively obtain the blood mixing degree of the portal vein ,in represents the volume of blood mixed with the splenic vein in the portal vein (i.e., volume fraction R V_SMV between 0.01 and 0.99 of the blood volume), Represents the total volume of portal vein blood. The higher the value, the higher the blood mixing degree in the portal vein, and vice versa. The distribution trend of the blood mixing degree in the portal vein trunk of each patient before TIPS surgery is shown in the figure. Figure 2 As shown in the figure, the distribution trend of blood mixing degree in the main portal vein of each patient after TIPS surgery is shown in the figure. Figure 3 The schematic diagram of the cross-section segmentation is shown in Figure 4 shown.

[0024] The present invention discloses a method for predicting the risk of postoperative hepatic encephalopathy based on a method for calculating the degree of blood mixing, and a schematic diagram of the steps is shown in FIG. Figure 1 As shown, the method includes the steps of: S5, by calculating the blood mixing degree of the patient before TIPS surgery, obtaining the portal vein blood mixing degree characteristics, which is used to predict the risk of hepatic encephalopathy after TIPS surgery to assist clinical decision-making; wherein the blood mixing degree calculation specifically adopts the blood mixing degree calculation method described above. Predicting the risk of hepatic encephalopathy after TIPS surgery by using the portal vein blood mixing degree characteristics includes: before performing TIPS surgery, selecting patients with high blood mixing degrees to perform TIPS surgery, so as to reduce the probability of hepatic encephalopathy after TIPS surgery.

[0025] For example, splenic vein blood is rich in hormones that can stimulate liver cell proliferation, such as insulin and glucagon, while SMV blood carries nutrients absorbed by the intestine and toxic substances including blood ammonia, and is often called "dirty blood". For a long time, the academic community generally believed that in a healthy portal vein system, SMV blood and SV blood flow independently after merging into the portal vein without mixing (i.e., the "portal vein streamline effect"). Specifically, SMV blood mainly flows into the right portal vein to supply blood to the right liver lobe, while SV blood mainly flows to the left portal vein to nourish the left liver lobe. Based on this theoretical framework, some researchers suggest implanting a transjugular intrahepatic portosystemic shunt (TIPS) stent into the left portal vein to reduce the incidence of postoperative hepatic encephalopathy. In addition, ultrasound and portal vein angiography are currently used clinically to observe and analyze the blood flow pattern of the portal vein system and the blood distribution characteristics of the superior mesenteric vein, and the conclusion of the portal vein "streamline phenomenon" has been drawn. The present invention found through preoperative numerical simulation of patients with portal hypertension that in most cases, there is significant mixing of SMV and SV blood after they flow into the portal vein. This is the first time that evidence of blood mixing has been found in the portal vein of patients with liver disease, and a quantitative parameter C is proposed to calculate the degree of blood mixing. This is more accurate than the traditional qualitative method that relies on portal vein angiography observation and judgment, and can also perform risk analysis on the risk of disease occurrence, thereby improving clinical treatment effects.

[0026] For example, there is a certain correlation between the degree of blood mixing of patients before TIPS surgery and the incidence of hepatic encephalopathy after TIPS surgery. The higher the degree of blood mixing, the lower the incidence of hepatic encephalopathy after surgery. Therefore, the relationship between the degree of blood mixing between SMV and splenic vein in the portal vein before TIPS surgery and hepatic encephalopathy was further analyzed. The schematic diagram of the prediction curve of the degree of blood mixing in the portal vein before TIPS surgery for hepatic encephalopathy after TIPS surgery is shown in Figure 5 As shown, the dotted line is the reference line, and the solid line is AUC equal to 0.0674 (AUC is used to evaluate the ability of blood tests to distinguish diseases); the degree of portal vein blood mixing before TIPS surgery has a certain predictive value for hepatic encephalopathy in patients after TIPS surgery. This shows that before TIPS surgery, patients suitable for TIPS treatment can be selected based on the degree of blood mixing of the patients, thereby reducing the complications of hepatic encephalopathy after TIPS surgery.

[0027] 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 the degree of blood mixing, 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 the mixing degree of portal vein blood.

2. A method for calculating the degree of blood mixing 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 the degree of blood mixing 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 the degree of blood mixing 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 the degree of blood mixing according to claim 4, 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 is the volume fraction of the continuous phase c, For discrete phase The physical density of is the velocity of the discrete phase d, is the velocity of the continuous phase c, is the particle surface relaxation parameter time, which is calculated as follows: ,in represents the diameter of the discrete phase d droplet, represents the shear viscosity of the discrete phase d, 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 is the physical density of the continuous phase c, is the shear viscosity of the continuous phase c.

6. A method for calculating the degree of blood mixing according to claim 5, characterized in that: Step S4 also includes: when the SMV blood volume fraction in the unit blood volume is R V_SMV <0.01, the portal vein blood is pure splenic vein blood; when the SMV blood volume fraction per unit blood volume is 0.01≤R V_SMV When the SMV blood volume fraction per unit blood volume is R V_SMV When >0.99, the portal vein blood is pure SMV blood; the calculation method of SMV blood volume fraction is R V_SMV =V SMV / V E , where V SMV is the volume of SMV per unit of blood, V E is the unit blood volume; through the formula Quantitatively obtain the blood mixing degree of the portal vein ,in represents the volume of blood in the portal vein that mixes with the blood in the SMV and splenic veins. Represents the total volume of portal vein blood.

7. A method for predicting the risk of postoperative hepatic encephalopathy based on a blood mixing degree calculation method, characterized in that: The method comprises the steps of: S5, calculating the blood mixing degree of the patient before TIPS surgery to obtain the portal vein blood mixing degree characteristics, which is used to predict the risk of hepatic encephalopathy after TIPS surgery to assist clinical decision-making; The blood mixing degree is calculated by using the blood mixing degree calculation method as described in any one of claims 1-6.

8. The method for predicting the risk of postoperative hepatic encephalopathy based on the blood mixing degree calculation method according to claim 7, characterized in that: Predicting the risk of hepatic encephalopathy after TIPS surgery by using the characteristics of portal vein blood mixing degree includes: before TIPS surgery, selecting patients with high blood mixing degree to undergo TIPS surgery.

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