Method for calculating vascular blood flow

Abstract

The present disclosure describes a method for calculating blood flow in a blood vessel, which includes: obtaining a medical image of the blood vessel, extracting a two-dimensional trunk parameter of the blood vessel and a two-dimensional branch parameter of the blood vessel from the medical image; dividing the two-dimensional trunk into a plurality of two-dimensional trunk segments based on the two-dimensional trunk parameter and the two-dimensional branch parameter; calculating a trunk reference diameter of the plurality of two-dimensional trunk segments and a branch reference diameter of the two-dimensional branch; causing a contrast agent to flow through the trunk of the blood vessel and calculating a time for the contrast agent to flow through the trunk of the blood vessel; and calculating a trunk flow of each of the plurality of two-dimensional trunk segments and a branch flow of the two-dimensional branch based on the trunk reference diameter of the plurality of two-dimensional trunk segments, the branch reference diameter of the two-dimensional branch, and the time for the contrast agent to flow through the trunk of the blood vessel. According to the present disclosure, a method for accurately calculating blood flow in a blood vessel can be provided.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of data processing of medical images, and in particular to a method for calculating blood flow of blood vessels. BACKGROUND

[0002] Conventional cardiovascular imaging techniques such as coronary X-ray angiography, coronary CT angiography, and intraluminal imaging techniques can image the coronary artery, display the damaged site and range of the blood vessel, but there are certain limitations in determining whether the damage causes ischemia and locating the culprit vessel. Fractional flow reserve (FFR) can make up for the shortcomings of the above imaging techniques, optimize the diagnosis of ischemic heart disease and the selection of culprit vessels, reduce unnecessary stent implantation, and improve the long-term treatment efficacy of patients, and has become the gold standard for evaluating ischemic heart disease in clinical practice.

[0003] FFR can be obtained by dividing the maximum myocardial blood flow in the presence of epicardial coronary stenosis by the maximum blood flow in the normal blood vessel. Under maximum hyperemia, the ratio of blood flow can be replaced by pressure value, therefore, using a pressure-sensitive coronary catheter, FFR can be calculated by comparing the pressure at the distal end of the coronary stenosis (Pd) and the large artery pressure (Pa) obtained by the hemodynamic pressure sensor under maximum hyperemia. Pressure wire guided FFR is an important hemodynamic indicator of coronary stenosis, but has some limitations, such as invasiveness diagnosis which can cause certain harm to patients, or some patients have an adverse reaction when adenosine is injected, and the cost of pressure wire is too high.

[0004] With the development of technology and research level, especially the development of medical image imaging and reconstruction technology and high-performance computing technology, the application of computational fluid dynamics (CFD) to calculate FFR is becoming a rapidly developing frontier. Compared with traditional FFR, the application of CFD to calculate FFR is non-invasive. According to the comparison of clinical trials, CFD calculated FFR has very high ability in the diagnosis of myocardial ischemia in terms of accuracy, sensitivity, and specificity at the individual vascular level of the patient, and is superior to the method evaluated by imaging.

[0005] In order to ensure the accuracy of the CFD calculation, the flow boundary condition required for the calculation is usually obtained through coronary angiography. In the traditional flow calculation method, the following problems are usually encountered: 1. In the traditional TIMI Frame Count algorithm, the average flow rate is calculated instead of the flow rate. In the CFD calculation, the cross-sectional area of the blood vessel inlet is uncertain, so the use of the flow rate boundary condition will affect the simulation result; 2. The traditional TIMI Frame Count assumes that the flow rate is the same at any position in the coronary system, while in the actual situation, the flow rate is affected by the diameter of the blood vessel, and this setting actually simplifies the influence of the branch on the blood flow distribution. SUMMARY

[0006] The present disclosure is proposed in view of the above-mentioned prior art, and aims to provide a calculation method capable of accurately calculating the blood flow of a blood vessel.

[0007] The present disclosure provides a calculation method for blood flow of a blood vessel, which comprises: obtaining a medical image of a blood vessel, extracting a two-dimensional trunk parameter of the blood vessel and a two-dimensional branch parameter of the blood vessel according to the medical image; dividing a two-dimensional trunk into a plurality of two-dimensional trunk segments based on the two-dimensional trunk parameter and the two-dimensional branch parameter; calculating a trunk reference diameter and a length of each of the plurality of two-dimensional trunk segments and a branch reference diameter of a two-dimensional branch; making a contrast agent flow through a trunk of the blood vessel, and calculating a time for the contrast agent to flow through the trunk of the blood vessel; and calculating a trunk flow of each of the plurality of two-dimensional trunk segments and a branch flow of the two-dimensional branch based on the trunk reference diameter and the length of each of the plurality of two-dimensional trunk segments, the branch reference diameter of the two-dimensional branch, and the time for the contrast agent to flow through the trunk of the blood vessel. In the present disclosure, the two-dimensional trunk parameter and the two-dimensional branch parameter extracted from the medical image can divide the two-dimensional trunk into a plurality of two-dimensional trunk segments, further calculate the trunk reference diameter of each of the two-dimensional trunk segments and the branch reference diameter of the two-dimensional branch, and calculate the trunk flow of each of the two-dimensional trunk segments and the branch flow of the two-dimensional branch based on the trunk reference diameter of each of the plurality of two-dimensional trunk segments, the branch reference diameter of the two-dimensional branch, and the time for the contrast agent to flow through the trunk of the blood vessel, so as to conveniently calculate the blood flow of the blood vessel.

[0008] In addition, in the calculation method of the present disclosure, the two-dimensional trunk parameter comprises a two-dimensional trunk center line and a two-dimensional trunk contour line, and the two-dimensional branch parameter comprises a two-dimensional branch contour line. Thus, the two-dimensional trunk parameter and the two-dimensional branch parameter can be conveniently determined.

[0009] In addition, in the calculation method disclosed in the present disclosure, optionally, the two-dimensional branch profile line is extended in the direction of the two-dimensional trunk, and a midpoint of two intersection points of the two-dimensional branch profile line and the two-dimensional trunk center line is the starting point of the two-dimensional branch; and the two-dimensional trunk is divided into a plurality of two-dimensional trunk segments based on the starting point of the two-dimensional branch. In this way, the starting point of the two-dimensional branch can be conveniently determined, and the two-dimensional trunk can be conveniently divided into a plurality of two-dimensional trunk segments according to the starting point of the two-dimensional branch.

[0010] In addition, in the calculation method disclosed in the present disclosure, optionally, a three-dimensional trunk center line of the blood vessel is constructed based on the two-dimensional trunk center lines of the plurality of medical images, and a three-dimensional trunk model of the blood vessel is reconstructed according to the two-dimensional trunk profile line of the blood vessel and the three-dimensional trunk center line of the blood vessel. In this way, the three-dimensional trunk center line of the blood vessel can be conveniently constructed, and the three-dimensional trunk model of the blood vessel can be conveniently constructed according to the three-dimensional trunk center line of the blood vessel and the two-dimensional trunk profile line of the blood vessel.

[0011] In addition, in the calculation method disclosed in the present disclosure, optionally, the two-dimensional trunk center line and the three-dimensional trunk center line are corresponded, and the three-dimensional trunk model is divided into a plurality of three-dimensional trunk segments. In this way, by corresponding the two-dimensional trunk center line and the three-dimensional trunk center line, the three-dimensional trunk model can be conveniently divided into a plurality of three-dimensional trunk segments.

[0012] In addition, in the calculation method disclosed in the present disclosure, optionally, the trunk reference diameter is the maximum diameter in each two-dimensional trunk segment, and the branch reference diameter is the maximum diameter of the blood vessel branch closest to the blood vessel trunk. In this way, the trunk reference diameter and the branch reference diameter can be conveniently determined.

[0013] In addition, in the calculation method disclosed in the present disclosure, optionally, each three-dimensional trunk segment is line integrated in a three-dimensional space to obtain the length of each three-dimensional trunk segment as the length of each two-dimensional trunk segment. In this way, the length of each two-dimensional trunk segment can be conveniently obtained.

[0014] In addition, in the calculation method disclosed in the present disclosure, optionally, the frame number f1 of the contrast image taken at the entrance of the blood vessel trunk where the contrast agent appears, the frame number f2 of the contrast image taken at the exit of the blood vessel trunk where the contrast agent appears, and the time interval I between each two contrast images are recorded, and the expression of the time t of the contrast agent flowing through the blood vessel trunk is: t=(f2-f1)×I. In this way, the time t of the contrast agent flowing through the blood vessel trunk can be conveniently calculated.

[0015] In addition, in the calculation method involved in the present disclosure, optionally, the two-dimensional trunk includes a first two-dimensional trunk segment, a second two-dimensional trunk segment,..., an Nth two-dimensional trunk segment, and a first two-dimensional branch, a second two-dimensional branch,..., and an N-1th two-dimensional branch, a trunk reference diameter of the first two-dimensional trunk segment is d0, a flow of blood flowing into the first two-dimensional trunk segment is Q0, a trunk reference diameter of the second two-dimensional trunk segment is d1, a flow of blood flowing into the second two-dimensional trunk segment is Q1, a branch reference diameter of the first two-dimensional branch is d1 * , a flow of blood flowing into the first two-dimensional branch is Q1 * * , a branch reference diameter of the second two-dimensional branch is d2 * N-1 , a flow of blood flowing into the second two-dimensional branch is Q2 N-1 N-1 * , a branch reference diameter of the N-1th two-dimensional branch is d N-1 * , and a flow of blood flowing into the N-1th two-dimensional branch is Q n n , according to Murray's law: d0 n n n n n n n n n n n n N-1 n N-1 n , wherein n is a Murray coefficient, and n ranges from 2 to 3, and the flow distribution relationship is: Q1=(d1 / d0) n ×Q0, Q1*=(d1* / d0) n ×Q0, Q2=(d2 / d1) n ×Q1, Q2*=(d2* / d1) n ×Q1, Q3=(d3 / d2) n ×Q2, Q3*=(d3* / d2) n ×Q2,..., Q N-1 ​​​​​​​​​​​​​​​​​​=(d N-1 / d N-2 ) n ×Q N-2 Q N-1 *=(d N-1 / d N-2 ) n ×Q N-2 Therefore, it is possible to easily construct the relationship between the reference diameter and flow rate of each two-dimensional trunk segment, and the reference diameter and flow rate of each branch of the blood vessel.

[0016] Additionally, in the calculation method disclosed herein, optionally, the length of the first two-dimensional backbone segment is L0, the length of the second two-dimensional backbone segment is L1, ..., and the length of the Nth two-dimensional backbone segment is L... N-1 The time it takes for the contrast agent to flow through the first two-dimensional trunk segment is t0, the time it takes for the contrast agent to flow through the second two-dimensional trunk segment is t1, ..., the time it takes for the contrast agent to flow through the Nth two-dimensional trunk segment is t. N-1 Then we have: t0=L0×π×d0 2 / 8Q0, t1=L1×π×d1 2 / 8Q1,……,t N-1 =L N-1 ×π×d N-1 2 / 8Q N-1 Where π is the mathematical constant pi. This allows for the convenient calculation of the time it takes for the contrast agent to flow through each segment of the two-dimensional trunk.

[0017] Additionally, in the calculation method disclosed herein, optionally, the time t for the contrast agent to flow through the main blood vessel is considered, resulting in t = t0 + t1 + ... + t N-1 t0 = L0 × π × d0 2 / 8Q0, t1=L1×π×d1 2 / 8Q1,……,t N-1 =L N-1 ×π×d N-1 2 / 8Q N-1 Substitute these values ​​to obtain the flow rate Q0 of the first two-dimensional backbone segment, the flow rate Q1 of the second two-dimensional backbone segment, ..., the flow rate Q of the Nth two-dimensional backbone segment. N-1 and the flow rate Q1 of the first two-dimensional branch. * The flow rate Q2 of the second two-dimensional branch * The flow rate of the (N-1)th two-dimensional branch is Q. N-1 * The value of is thus easily obtained. Therefore, the blood flow rate into each segment of the main blood vessel and the blood flow rate into each two-dimensional branch can be readily calculated.

[0018] According to the present disclosure, a calculation method capable of accurately calculating blood flow in a blood vessel can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0019] The present disclosure will now be explained in further detail by way of example only with reference to the accompanying drawings.

[0020] Figure 1 is a flowchart illustrating one example of a blood flow calculation method according to the present disclosure.

[0021] Figure 2 is a structural diagram illustrating a two-dimensional blood vessel according to the present disclosure.

[0022] Figure 3 is a structural diagram illustrating a two-dimensional trunk centerline and contour line and a two-dimensional branch contour line according to the present disclosure.

[0023] Figure 4 is a structural diagram illustrating Figure 3 is an enlarged diagram of the A region in FIG.

[0024] Figure 5 is a flowchart illustrating another example of a blood flow calculation method according to the present disclosure. DETAILED DESCRIPTION

[0025] Hereinafter, a preferred embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, the same parts are given the same reference numerals, and overlapping descriptions will be omitted. In addition, the drawings are merely schematic diagrams, and the proportions of the sizes of the components with respect to each other or the shapes of the components, etc. can be different from the actual ones.

[0026] Note that the terms "comprise" and "have" and any variations thereof, such as a process, method, apparatus, product, or device including or having a series of steps or units, in the present disclosure are not necessarily limited to those clearly listed steps or units, but can include or have other steps or units not clearly listed or inherent to such processes, methods, products, or devices.

[0027] In addition, the subheadings and the like involved in the following description of the present disclosure are not intended to limit the content or scope of the present disclosure, but merely serve as a reading aid. Such subheadings should not be understood as dividing the content of the article, nor should the content under the subheadings be limited only within the scope of the subheadings.

[0028] The blood vessel involved in the present embodiment can be a coronary artery vessel, and the blood flow calculation method involved in the present embodiment can also be referred to as a coronary artery vessel flow calculation method or simply a calculation method. Compared with general methods for evaluating blood flow rate in a blood vessel, the blood flow calculation method involved in the present disclosure calculates the flow rate, and the presence of branches is considered in the calculation process. Further, by applying the flow distribution method of Murray's Law, the flow distribution of each section of the blood vessel can be conveniently calculated.

[0029] In the following, the blood vessel blood flow calculation method involved in the present embodiment will be described in detail with reference to the accompanying drawings.

[0030] Figure 1 is a flowchart showing one example of the blood vessel blood flow calculation method involved in the present disclosure.

[0031] Referring to Figure 1 In the present embodiment, the blood vessel blood flow calculation method can include the following steps:

[0032] Step S100, acquiring a medical image of a blood vessel 10;

[0033] Step S200, extracting two-dimensional trunk parameters of the blood vessel 10 and two-dimensional branch parameters of the blood vessel 10 from the medical image;

[0034] Step S300, based on the two-dimensional trunk parameters and the two-dimensional branch parameters, the two-dimensional trunk can be divided into a plurality of two-dimensional trunk sections;

[0035] Step S400, calculating the trunk reference diameter of the plurality of two-dimensional trunk sections and the branch reference diameter of the two-dimensional branches;

[0036] Step S500, flowing a contrast agent through the blood vessel trunk and calculating the time for the contrast agent to flow through the blood vessel trunk;

[0037] Step S600, based on the trunk reference diameter of the plurality of two-dimensional trunk sections, the branch reference diameter of the two-dimensional branches, and the time for the contrast agent to flow through the blood vessel trunk, calculating the trunk flow rate of each two-dimensional trunk section and the branch flow rate of the two-dimensional branches.

[0038] In the present disclosure, the two-dimensional trunk parameters and the two-dimensional branch parameters extracted from the medical image can divide the two-dimensional trunk into a plurality of blood vessel sections, further calculate the trunk reference diameter of each two-dimensional trunk section and the branch reference diameter of the two-dimensional branches, and based on the trunk reference diameter of the plurality of two-dimensional trunk sections, the branch reference diameter of the two-dimensional branches, and the time for the contrast agent to flow through the blood vessel trunk, the trunk flow rate of each two-dimensional trunk section and the branch flow rate of the two-dimensional branches can be calculated, thereby the blood flow rate of the blood vessel can be conveniently calculated.

[0039] It can be understood that in some examples, the execution order of step S400 is not strictly required, which can be executed simultaneously with step S500, or can be executed prior to any one of steps S100 to S300.

[0040] In some examples, the two-dimensional trunk parameter and the two-dimensional branch parameter can be collectively referred to as a two-dimensional blood vessel parameter or a coronary blood vessel parameter.

[0041] In some examples, in step S100, a medical image related to a heart can be acquired.

[0042] In some examples, the medical image related to the heart can be a two-dimensional image, a three-dimensional image or other forms of images capable of representing the characteristics of coronary artery lesions, such as X-ray contrast images, CT contrast images, MRI contrast images, etc. In the present embodiment, preferably, two-dimensional medical images can be used, and the medical image related to the present disclosure can be a coronary angiography image.

[0043] Figure 2 is a structural schematic diagram illustrating a two-dimensional blood vessel related to the present disclosure. Figure 3 is a structural schematic diagram illustrating a two-dimensional trunk center line and a contour line and a two-dimensional branch contour line related to the present disclosure. Figure 4 is a structural schematic diagram illustrating Figure 3 is an enlarged schematic diagram of the A area in Figure 5 is a flowchart illustrating another example of a calculation method of a blood flow of a blood vessel related to the present disclosure.

[0044] Referring to Figure 2 In some examples, the blood vessel 10( Figure 2 is a two-dimensional blood vessel 10) can generally include a two-dimensional blood vessel trunk 110 and a two-dimensional blood vessel branch 120 (or referred to as a two-dimensional trunk 110 and a two-dimensional branch 120). In the present disclosure, the two-dimensional blood vessel trunk 110 and the blood vessel trunk can be slightly distinguished, and the blood vessel trunk represents the blood vessel trunk of an entity or a three-dimensional blood vessel trunk.

[0045] In some examples, referring to Figure 2 The blood vessel 10 can have one two-dimensional trunk 110 and several two-dimensional branches 120 sprouting from the two-dimensional trunk 110. In some examples, the two-dimensional branches 120 can include a first two-dimensional branch 121, a second two-dimensional branch 122 and a third two-dimensional branch 123.

[0046] Referring to Figure 3 In some examples, the two-dimensional trunk parameter can include a two-dimensional trunk center line 101 and a two-dimensional trunk contour line 102. In some examples, the two-dimensional branch parameter can include a two-dimensional branch contour line 103.

[0047] Referring to Figure 5 In some examples, the method for calculating the blood flow of the blood vessel can further include step 210: a three-dimensional trunk centerline of the blood vessel can be constructed based on the two-dimensional trunk centerlines of the multiple medical images. Thus, the three-dimensional trunk centerline of the blood vessel 10 can be conveniently constructed.

[0048] In some examples, a three-dimensional trunk model of the blood vessel 10 can be reconstructed by using spatial coordinate transformation according to the two-dimensional trunk profile line 102 of the blood vessel 10 and the three-dimensional trunk centerline of the blood vessel 10. Thus, the three-dimensional trunk model of the blood vessel 10 can be conveniently reconstructed.

[0049] In some examples, the three-dimensional trunk centerline of the blood vessel 10 can be constructed by using spatial coordinate transformation based on the two-dimensional trunk centerline 101. In some examples, the three-dimensional trunk centerline of the blood vessel 10 can be constructed based on spatial coordinate transformation according to the two-dimensional trunk centerline 101 of the blood vessel 10 in the two medical images.

[0050] In some examples, when constructing the three-dimensional trunk centerline of the blood vessel 10, the points on the two-dimensional trunk centerline 101 of the two medical images can be one-to-one corresponding, and the three-dimensional coordinates of each point can be calculated based on spatial coordinate transformation.

[0051] In some examples, the two medical images used for constructing the three-dimensional trunk centerline of the blood vessel 10 can have a predetermined included angle, in other words, when the target blood vessel is photographed, the photographing angle can have a predetermined included angle, which can facilitate the use of the two medical images for spatial coordinate transformation to construct the three-dimensional trunk centerline of the blood vessel 10. In this case, by having a predetermined included angle between the two images, the three-dimensional trunk centerline of the blood vessel 10 can be conveniently constructed.

[0052] In some examples, the value range of the predetermined included angle can be 20° to 60°.

[0053] In some examples, the trunk reference diameter can be the maximum diameter in each two-dimensional trunk segment. In some examples, the branch reference diameter can be the maximum diameter at the position closest to the trunk of the blood vessel branch. Thus, the trunk reference diameter and the branch reference diameter can be conveniently determined.

[0054] Referring to Figure 4In some examples, the two-dimensional branch profile line 103 can be extended in the direction of the two-dimensional trunk 110 (i.e., the two-dimensional branch profile line 103a, 103b is extended), and the midpoint C of the two intersection points of the two-dimensional branch profile line 103a, 103b and the two-dimensional trunk center line 101 can be taken as the starting point of the two-dimensional branch 120. In some examples, based on the starting point C of the two-dimensional branch 120, the two-dimensional trunk can be divided into a plurality of two-dimensional trunk segments. In this way, the starting point C of the two-dimensional branch 120 can be conveniently constructed, and the two-dimensional trunk can be divided into a plurality of two-dimensional trunk segments according to the starting point C of the two-dimensional branch 120.

[0055] Referring to Figure 5 In some examples, after step S250 and step S210, the blood vessel blood pressure flow calculation method can further include step 260: the two-dimensional trunk center line 101 and the three-dimensional trunk center line can be corresponded, for example, the two-dimensional trunk center line 101 and the three-dimensional trunk center line can be corresponded in spatial coordinates. And in combination with the starting point of the two-dimensional branch obtained in step S250, the three-dimensional trunk model is divided into a plurality of three-dimensional trunk segments.

[0056] In some examples, the three-dimensional trunk center line can also be divided, that is, based on step S260, the three-dimensional trunk center line can be divided into a plurality of three-dimensional trunk center line segments.

[0057] In some examples, after step S360, the blood vessel blood pressure flow calculation method can further include step 5600: each three-dimensional trunk segment can be line integrated in three-dimensional space to obtain the length of each three-dimensional trunk segment, and the length of each three-dimensional trunk segment can be taken as the length of each two-dimensional trunk segment. In this case, since the blood vessel is a blood vessel in three-dimensional space, that is, the blood vessel is tortuous and sprawling in three-dimensional space, by considering the position of the blood vessel in three-dimensional space, the length of each two-dimensional trunk segment can be accurately obtained.

[0058] In some examples, the plurality of three-dimensional trunk center line segments can be line integrated in three-dimensional space to obtain the length of each three-dimensional trunk center line segment, and the length of each three-dimensional trunk center line segment can be taken as the length of each two-dimensional trunk segment.

[0059] In combination Figures 2 to 5 In some examples, based on the plurality of branches (such as the first two-dimensional branch 121, the second two-dimensional branch 122, and the third two-dimensional branch 123) on the two-dimensional trunk 110, the above method can be used to divide the two-dimensional trunk 110 into the first two-dimensional trunk 111, the second two-dimensional trunk 112, the third two-dimensional trunk 113, and the fourth two-dimensional trunk 114.

[0060] In some examples, the trunk reference diameter can be the maximum diameter in each two-dimensional trunk segment. In some examples, since the diameter of the blood vessel trunk has a tendency to gradually decrease along the direction of blood flow, the diameter at the starting position of each two-dimensional trunk segment can be taken as the trunk reference diameter.

[0061] In some examples, the branch reference diameter can be the maximum diameter of the blood vessel branch (or two-dimensional branch 120) at the position closest to the blood vessel trunk. That is, the branch reference diameter can be the diameter at the starting position of the blood vessel branch when the two-dimensional trunk 110 extends out. In this way, the trunk reference diameter of each two-dimensional trunk segment and the branch reference diameter of each blood vessel branch (or two-dimensional branch) can be conveniently selected.

[0062] In some examples, the trunk reference diameter and the branch reference diameter can be directly measured when steps S200 and S300 are performed. That is, the numerical values of the two-dimensional trunk parameters and the two-dimensional branch parameters can be directly measured on the images or pictures in the process of extracting the two-dimensional trunk parameters and the two-dimensional branch parameters from the medical images and dividing the two-dimensional trunk 110 into multiple two-dimensional trunk segments.

[0063] In some examples, the contrast agent can be allowed to flow through the blood vessel trunk, and the flow of the contrast agent can be photographed. The frame number f1 of the contrast image photographed when the contrast agent appears at the entrance of the blood vessel trunk, and the frame number f2 of the contrast image photographed when the contrast agent appears at the exit of the blood vessel trunk can be recorded. The time interval between every two contrast images is I. The expression of the time t of the contrast agent flowing through the blood vessel trunk is:

[0064] t = (f2-f1) x I …… Equation (1)

[0065] In this way, the time t of the contrast agent flowing through the blood vessel trunk can be conveniently calculated. For example, the photographing can be started in advance before the contrast agent enters the blood vessel or the target blood vessel to be measured. When the contrast agent appears at the entrance of the blood vessel trunk, the frame number of the contrast image photographed is 4 (i.e., the 4th frame image is photographed). When the contrast agent appears at the exit of the blood vessel trunk, the frame number of the contrast image photographed is 14 (i.e., the 14th frame image is photographed). Assuming that the time interval between every two contrast images is 0.1 s, the time t of the contrast agent flowing through the blood vessel trunk is: t = (14-4) x 0.1 = 1 s.

[0066] In some examples, the two-dimensional blood vessel trunk 110 can include a first two-dimensional trunk segment 111, a second two-dimensional trunk segment 112, …, an Nth two-dimensional trunk segment, and a first two-dimensional branch 121, a second two-dimensional branch 122, …, and an N-1th two-dimensional branch.

[0067] The trunk reference diameter of the first two-dimensional trunk segment 111 is d0, the flow rate of blood flowing through the first two-dimensional trunk segment 111 is Q0 (the flow rate Q0 can be the flow rate at the inlet of the two-dimensional blood vessel trunk 110), the trunk reference diameter of the second two-dimensional trunk segment 112 is d1, the flow rate of blood flowing through the second two-dimensional trunk segment 112 is Q1, the branch reference diameter of the first two-dimensional branch is d1 * , the flow rate of blood flowing through the first two-dimensional branch is Q1 * , the branch reference diameter of the second two-dimensional branch is d2 * , the flow rate of blood flowing through the second two-dimensional branch is Q2 * , …, the trunk reference diameter of the Nth two-dimensional trunk segment is d N-1 , the flow rate of blood flowing through the Nth two-dimensional trunk segment is Q N-1 , the branch reference diameter of the (N-1)th two-dimensional branch is d N-1 * , the flow rate of blood flowing through the (N-1)th two-dimensional branch is Q N-1 * .

[0068] According to Murray's law, we have:

[0069] d0 n = d1 n + (d1 n )= (d1 n ) + (d2 n ) + d2 n = (d1 n ) + (d2 n ) + (d3 n ) + d3 n = (d1 n ) + (d2 n ) + (d3 n ) + (d4 n ) …… + (d N-1 ) + d n N-1 n ……Equation (2)

[0070] wherein n is the Murray coefficient, and n can be in the range of 2 to 3.

[0071] The flow rate distribution relationship is:

[0072] Q1 = (d1 / d0) n × Q0, … Equation (3-1)

[0073] Q1* = (d1* / d0) n × Q0, … Equation (3-1')

[0074] Q2 = (d2 / d1) n × Q1, …… equation (3-2)

[0075] Q2* = (d2* / d1) n × Q1, …… equation (3-2')

[0076] Q3 = (d3 / d2) n × Q2, …… equation (3-3)

[0077] Q3* = (d3* / d2) × Q2, …… equation (3-3')

[0078] ……,

[0079] Q N-1 = (d N-1 / d N-2 ) n × Q N-2 , …… equation (3-N-1)

[0080] Q N-1 * = (d N-1 * / d N-2 ) n × Q N-2 …… equation (3-N-1')

[0081] Thus, the relationship between the trunk reference diameter and flow of each two-dimensional trunk segment and the branch reference diameter and flow of each blood vessel branch can be conveniently constructed.

[0082] In some examples, the above-mentioned flow can be the flow of blood flowing into the inlet of the corresponding two-dimensional trunk segment or blood vessel branch.

[0083] In some examples, the length of the first two-dimensional trunk segment is L0, the length of the second two-dimensional trunk segment is L1, …, and the length of the Nth two-dimensional trunk segment is LN. N-1 The time for the contrast agent to flow through the first two-dimensional trunk segment is t0, the time for the contrast agent to flow through the second two-dimensional trunk segment is t1, …, and the time for the contrast agent to flow through the Nth two-dimensional trunk segment is tN. N-1 According to the above relationship, we have:

[0084] t0 = L0 × π × d0 2 / 8Q0, …… equation (4-0)

[0085] t1 = L1 × π × d1 2 / 8Q1, …… equation (4-1)

[0086] ……,

[0087] t N-1= L N-1 x π x d N-1 2 / 8Q N-1 , …… Equation (4-n)

[0088] wherein π is a circle constant. Thus, an expression of the time for the contrast agent to flow through each two-dimensional trunk segment, or more specifically, a relationship between the time for the contrast agent to flow through each two-dimensional trunk segment and the flow rate of blood through the corresponding two-dimensional trunk segment, can be conveniently constructed.

[0089] In some examples, as described in the aforementioned step S560, the length of the three-dimensional centerline or the length of the three-dimensional trunk can be taken as the length of the two-dimensional trunk, and the length of the three-dimensional trunk segment can be taken as the length of the two-dimensional trunk segment. In this case, since the length of the two-dimensional trunk or the two-dimensional trunk segment needs to be calculated in combination with its position in the three-dimensional space, the accuracy of the length calculation of the two-dimensional trunk or the two-dimensional trunk segment can be improved.

[0090] Specifically, taking the first two-dimensional trunk segment as an example, the flow rate Q0 of the contrast agent flowing through the first two-dimensional trunk segment is:

[0091] Q0 = π x (d0 / 2) 2 x v, …… Equation (5)

[0092] wherein v represents the average flow velocity of the contrast agent in the blood vessel.

[0093] and 2v = L0 / t0, …… Equation (6)

[0094] wherein 2v represents the maximum flow velocity of the contrast agent in the blood vessel, i.e., the flow velocity of the contrast agent in the center of the blood vessel.

[0095] By combining the aforementioned Equation (5) and Equation (6), Equation (4-0) can be obtained, i.e., t0 = L0 x π x d0 2 / 8Q0.

[0096] In some examples, each two-dimensional trunk segment can be line integrated in the three-dimensional space to obtain the length of each two-dimensional trunk segment. In this case, since the blood vessel is a blood vessel in the three-dimensional space, i.e., the blood vessel is tortuous and sprawling in the three-dimensional space, by considering the position of the blood vessel in the three-dimensional space, the length of each two-dimensional trunk segment can be accurately obtained.

[0097] In some examples, in combination with the time t for the contrast agent to flow through the blood vessel trunk, there is:

[0098] t = t0 + t1 + … + t N-1 …… Equation (7)

[0099] The formula (4-0) to formula (4-n) (i.e., t0=L0x pxd0 2 / 8Q0, t1=L1x pxd1 2 / 8Q1, …, t N-1 =L N-1 x pxd N-1 2 / 8Q N-1 ) are substituted into the formula (7), and combined with the formula (3-1) to formula (3-N-1’), the flow rate Q0 of the first two-dimensional main trunk section, the flow rate Q1 of the second two-dimensional main trunk section, …, the flow rate QN-1 of the N-1th two-dimensional main trunk section, and the flow rate Q1 of the first two-dimensional branch, the flow rate Q2 of the second two-dimensional branch, …, the flow rate QN-1 of the N-1th two-dimensional branch can be obtained. N-1 * * N-1 * Thus, the flow rate of each section of the blood vessel main trunk and each section of the blood vessel branch can be conveniently obtained.

[0100] In the present disclosure, by using the two-dimensional main trunk parameters and two-dimensional branch parameters extracted from the medical image, the two-dimensional main trunk can be divided into multiple sections of the blood vessel, and the main trunk reference diameter and length of each section of the two-dimensional main trunk, and the branch reference diameter of the two-dimensional branch can be calculated. Based on the main trunk reference diameter and length of each section of the two-dimensional main trunk, the branch reference diameter of the two-dimensional branch, and the time of the contrast agent flowing through the blood vessel main trunk, the main trunk flow rate of each section of the two-dimensional main trunk and the branch flow rate of the two-dimensional branch can be calculated. Thus, the blood flow rate of the blood vessel can be conveniently calculated. Compared with the general method for evaluating the blood flow rate of the blood vessel, the calculation result of the blood flow rate calculation method of the present disclosure is the flow rate, and the existence of the blood vessel branch is considered in the calculation process. Further, by using the flow rate distribution mode of Murray’s Law, the flow rate distribution of each section of the blood vessel can be calculated.

[0101] Although the present disclosure is specifically described above in combination with the drawings and examples, it should be understood that the above description does not limit the present disclosure in any form. Those skilled in the art can modify and change the present disclosure as needed without departing from the spirit and scope of the present disclosure, and such modifications and changes fall within the scope of the present disclosure.​​​

Claims

1.A method for calculating blood flow in a blood vessel, comprising: obtaining two-dimensional medical images of the blood vessel, extracting two-dimensional trunk parameters of the blood vessel and two-dimensional branch parameters of the blood vessel from the two-dimensional medical images; dividing a two-dimensional trunk into a plurality of two-dimensional trunk segments based on the two-dimensional trunk parameters and the two-dimensional branch parameters, wherein the two-dimensional trunk is divided into the plurality of two-dimensional trunk segments based on the starting points of the two-dimensional branches; calculating trunk reference diameters of the plurality of two-dimensional trunk segments and branch reference diameters of the two-dimensional branches; causing a contrast agent to flow through a trunk of the blood vessel, and calculating a time for the contrast agent to flow through the trunk of the blood vessel between an inlet and an outlet of the trunk of the blood vessel; and calculating trunk flow of each of the plurality of two-dimensional trunk segments and branch flow of the two-dimensional branches based on the trunk reference diameters of the plurality of two-dimensional trunk segments, the branch reference diameters of the two-dimensional branches, and the time for the contrast agent to flow through the trunk of the blood vessel. 2.The method of claim 1, wherein the two-dimensional trunk parameters comprise a two-dimensional trunk centerline and a two-dimensional trunk profile, and the two-dimensional branch parameters comprise a two-dimensional branch profile. 3.The method of claim 2, wherein the two-dimensional branch profile is extended towards the two-dimensional trunk, and a midpoint of two intersection points of the two-dimensional branch profile and the two-dimensional trunk centerline is a starting point of the two-dimensional branch. 4.The method of claim 3, wherein a three-dimensional trunk centerline of the blood vessel is constructed based on the two-dimensional trunk centerlines of a plurality of the medical images, and a three-dimensional trunk model of the blood vessel is reconstructed based on the two-dimensional trunk profile of the blood vessel and the three-dimensional trunk centerline of the blood vessel. 5.The method of claim 4, wherein the two-dimensional trunk centerline and the three-dimensional trunk centerline are corresponded, and the three-dimensional trunk model is divided into a plurality of three-dimensional trunk segments. 6.The method of claim 5, wherein each of the plurality of three-dimensional trunk segments is line integrated in a three-dimensional space to obtain a length of each of the plurality of three-dimensional trunk segments as a length of each of the plurality of two-dimensional trunk segments. 7.The method of claim 6, wherein a frame number f1 of a contrast image in which the contrast agent appears at the inlet of the trunk of the blood vessel, a frame number f2 of the contrast image in which the contrast agent appears at the outlet of the trunk of the blood vessel, and a time interval I between two of the contrast images are recorded, and an expression of a time t for the contrast agent to flow through the trunk of the blood vessel is t=(f2-f1)×I. 8.The method of claim 7, wherein the two-dimensional trunk comprises a first two-dimensional trunk segment, a second two-dimensional trunk segment, …, an Nth two-dimensional trunk segment, a first two-dimensional branch, a second two-dimensional branch, …, and an N-1th two-dimensional branch. 9.The method of claim 8, wherein the first two-dimensional trunk segment is divided into a first two-dimensional trunk subsegment, a second two-dimensional trunk subsegment, …, and an Nth two-dimensional trunk subsegment, and the first two-dimensional branch is divided into a first two-dimensional branch subsegment, a second two-dimensional branch subsegment, …, and an Nth two-dimensional branch subsegment. 10.The method of claim 9, wherein the first two-dimensional trunk subsegment is divided into a first two-dimensional trunk subsegment, a second two-dimensional trunk subsegment, …, and an Nth two-dimensional trunk subsegment, and the first two-dimensional branch subsegment is divided into a first two-dimensional branch subsegment, a second two-dimensional branch subsegment, …, and an Nth two-dimensional branch subsegment. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ the trunk reference diameter of the first two-dimensional trunk section is d0, the flow rate of blood flowing into the first two-dimensional trunk section is Q0, the trunk reference diameter of the second two-dimensional trunk section is d1, the flow rate of blood flowing into the second two-dimensional trunk section is Q1, the branch reference diameter of the first two-dimensional branch is d1 * , the flow rate of blood flowing into the first two-dimensional branch is Q1 * , the branch reference diameter of the second two-dimensional branch is d2 * , the flow rate of blood flowing into the second two-dimensional branch is Q2 * , …, the trunk reference diameter of the Nth two-dimensional trunk section is d N-1 , the flow rate of blood flowing into the Nth two-dimensional trunk section is Q N-1 , the branch reference diameter of the (N-1)th two-dimensional branch is d N-1 * , the flow rate of blood flowing into the (N-1)th two-dimensional branch is Q N-1 * , According to the Murray's law, there is: d0 n = d1 n + (d1 n )= (d1 n ) + (d2 n ) + d2 n = (d1 n ) + (d2 n ) + (d3 n ) + d3 n = (d1 n ) + (d2 n ) + (d3 n ) + (d4 n ) +... + (d N-1 ) + d n N-1 n , where n is the Murray coefficient, and n is in the range of 2-3, The flow distribution relationship is: Q1 = (d1 / d0) n ×Q0, Q1* = (d1* / d0) n ×Q0, Q2 = (d2 / d1) n ×Q1, Q2* = (d2* / d1) n ×Q1, Q3 = (d3 / d2) n ×Q2, Q3* = (d3* / d2) n ×Q2, …, Q N-1 = (d N-1 / d N-2 ) n ×Q N-2 , Q N-1 * = (d N-1 * / d N-2 ) n ×Q N-2 . ​ The length of the first two-dimensional trunk segment is L0, the length of the second two-dimensional trunk segment is L1,..., and the length of the Nth two-dimensional trunk segment is LN N-1 The time for the contrast agent to flow through the first two-dimensional trunk segment is t0, the time for the contrast agent to flow through the second two-dimensional trunk segment is t1,..., and the time for the contrast agent to flow through the Nth two-dimensional trunk segment is tN N-1 Then, t0=L0xπxd0 / 8Q0, t1=L1xπxd1 / 8Q1,..., and tN=LNxπxdN / 8QN 2 2 N-1 N-1 N-1 2 N-1 wherein π is a circular constant.​​​​​ ​ combining the time t for the passage of the contrast agent through the vessel trunk, there is t = t0+ t1+... + t N-1 , with t0= L0x π x d0 2 / 8Q0, t1= L1x π x d1 2 / 8Q1,..., t N-1 = LN x π x d N-1 / 8QN N-1 2 / 8Q N-1 , the flow rate Q0of the first two-dimensional trunk section, the flow rate Q1of the second two-dimensional trunk section,..., the flow rate Q N-1 of the Nth two-dimensional trunk section, and the flow rate Q1 * of the first two-dimensional branch, the flow rate Q2 * of the second two-dimensional branch,..., the flow rate Q N-1 of the Nth-1 two-dimensional branch, are obtained. *

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