CN107411767B - Narrow focus blood flow resistance calculation method based on coronary artery CT angiography - Google Patents
Narrow focus blood flow resistance calculation method based on coronary artery CT angiography Download PDFInfo
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- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/50—Clinical applications
- A61B6/507—Clinical applications involving determination of haemodynamic parameters, e.g. perfusion CT
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/02—Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
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- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
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- G—PHYSICS
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- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/30—Subject of image; Context of image processing
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- G06T2207/30101—Blood vessel; Artery; Vein; Vascular
- G06T2207/30104—Vascular flow; Blood flow; Perfusion
Abstract
The invention aims at a coronary artery CT angiography (cCTA) image, combines a Computational Fluid Dynamics (CFD) method to carry out hemodynamic simulation analysis, and calculates the blood flow resistance of a stenotic lesion. The invention comprises the following steps: (1) performing coronary artery three-dimensional reconstruction based on the cCTA image, and extracting a 3D model of a stenotic lesion; (2) constructing 7 groups of boundary conditions under different total blood flow conditions; (3) applying 7 groups of boundary conditions obtained in the step 2 to the 3D model obtained in the step 1, and respectively simulating and calculating the steady-state blood flow distribution condition by using a CFD method; (4) and extracting pressure drop-blood flow curves and parameters for characterizing the curves from the results of the 7 times of simulation to evaluate the blood flow resistance. The invention provides a novel method for calculating blood flow resistance parameters by combining cCTA and CFD. The method takes parameters of a fitted pressure-blood flow quadratic curve as parameters for describing the resistance characteristic of blood flow so as to accurately represent the relation between pressure drop and blood flow.
Description
Technical Field
The invention relates to a coronary artery CT angiography (cCTA) image and establishes a stenosis focus blood flow resistance calculation method based on the coronary artery CT angiography, belongs to the field of auxiliary diagnosis based on medical images, and mainly relates to a blood flow dynamics simulation analysis method based on the cCTA.
Background
Coronary atherosclerotic heart disease (coronary heart disease) is a serious disease endangering human health, Percutaneous Coronary Intervention (PCI) is an effective means for clinically treating the coronary heart disease, and 454505 PCI cases are completed in 2013 all over the country. The premise for rational treatment is accurate assessment of functional significance of coronary stenotic lesions, but unfortunately, anatomical morphological stenosis does not directly correspond to hemodynamic functional stenosis, and simple Coronary Angiography (CAG) does not accurately assess functional stenosis, which may result in unnecessary intervention of non-functional stenotic lesions or loss of optimal treatment timing for stenotic lesions with functional significance. Therefore, the assessment and research on the functional significance of coronary artery stenosis focus is increasingly emphasized by the academic circles at home and abroad, and becomes a hot spot and a leading topic of the research of the international academic circles.
Existing "gold standard" Fractional Flow Reserve (FFR) medicineThe ratio of the pressure at the far end of the stenosis focus to the pressure at the root of the aorta under the myocardial hyperemia state is measured to evaluate the coronary artery stenosis, and the influence of the stenosis focus on the blood supply function can be truly reflected. However, it is an invasive detection means, and needs to be measured in a state of drug-induced coronary hyperemia, which is expensive and has certain risks, and these all greatly limit the clinical application of FFR. With the development of Computational Fluid Dynamics (CFD), researchers have combined CFD with medical imaging to provide a non-invasive FFR evaluation methodCT. The method utilizes a cCTA image to accurately reconstruct a 3D model of the coronary artery, calculates and obtains blood flow and pressure distribution in the coronary artery in a hyperemia state by constructing a personalized 0D-3D coupling CFD simulation model, and calculates the pressure ratio of the far end and the near end of a stenotic lesion according to the definition of FFR, namely FFRCT. The biggest problems of the method are that: the method needs to accurately acquire the distribution of blood flow resistance in the maximum hyperemia state corresponding to the patient, but the current method adopts a series of physiological models (empirical formulas) and indirectly estimates the blood flow resistance distribution in the maximum hyperemia state through a cCTA image, so that the individualized differences of different patients cannot be fully considered, and the accuracy of the method is greatly limited by the estimation of the blood flow resistance distribution.
Based on the research background, the invention combines the cCTA and the CFD to provide a new method for calculating the blood flow resistance parameter. The method uses a quadratic curve to model corresponding keys of blood flow and pressure drop, extracts two parameters of the quadratic curve through simulation as parameters for describing resistance characteristics of blood flow, and accurately represents the relation between the pressure drop and the blood flow.
Disclosure of Invention
The invention provides a new method for calculating blood flow resistance parameters, which is based on a cCTA image, utilizes a numerical simulation technology to model the corresponding relation between blood flow and pressure drop, and extracts corresponding parameters. The technical scheme is as follows:
1. performing coronary artery three-dimensional reconstruction based on the cCTA image, and extracting a 3D model of a stenotic lesion;
2. constructing a boundary condition: applying pressure boundary conditions to the extracted 3D models of the stenotic lesions at inlets, and coupling lumped parameter models only comprising one resistance unit at each outlet; respectively setting 7 groups of different outlet blood flow resistance values to obtain 7 groups of boundary conditions corresponding to different total blood flow conditions;
3. corresponding to the set 7 different outlet blood flow resistance values, respectively simulating and calculating the steady-state blood flow distribution condition under the condition of 7 by utilizing a CFD (computational fluid dynamics) method;
4. and (4) respectively extracting corresponding pressure drop and blood flow of the stenotic lesion from the results of the 7 times of simulation calculation, and fitting a pressure drop-blood flow curve by using a quadratic curve to obtain fitting parameters, namely blood flow resistance parameters.
Drawings
FIG. 1 is a general flow chart of a method for assessing blood flow resistance of a stenotic lesion based on coronary CT angiography.
Fig. 2 three-dimensional reconstruction was performed based on the cta image, and only the stenotic lesion and its nearby branch vessels were retained.
FIG. 3 is a schematic diagram of boundary conditions.
Fig. 4.20 cases (three groups according to different stenosis degrees) were simulated to obtain pressure drop-blood flow values (punctate data) and curves (curves) obtained after regression according to the formula (1).
Detailed Description
The present invention will be described in further detail below with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto.
Fig. 1 shows an overall flowchart of a method for calculating blood flow resistance of a stenotic lesion based on coronary CT angiography. The following detailed description will be made with reference to fig. 1.
1. Three-dimensional reconstruction based on cCTA images
Firstly, a 3D model of the coronary artery is extracted semi-automatically by using a region growing algorithm, and for parts which are failed or unsatisfied in the extraction of the blood vessel boundary of the algorithm, the blood vessel boundary can be extracted by adopting a manual drawing mode, so that the 3D model of the coronary artery is reconstructed; then, as shown in fig. 2, only the stenotic lesion and the branch vessels near the stenotic lesion are retained, and the remaining vessel branches far away from the lesion are removed, so as to reduce the CFD simulation calculation area.
2. Construction of boundary conditions
a. As shown in fig. 3, the inlet applies a pressure boundary condition with the pressure value set to the patient's blood pressure (88 mmHg if not available); each outlet is coupled with a lumped parameter model containing a resistance unit;
b. the total blood flow resistance of the outlet branch vessel is initially set to 240(mmHg s/cm)3) Distributing the total blood flow resistance to each branch outlet according to the rule that the blood flow resistance is inversely proportional to the blood vessel radius power;
c. and (c) sequentially reducing the total blood flow resistance of the outlet branch vessels to 87.5%, 75.0%, 62.5%, 50.0%, 37.5% and 25.0% of the initial value, and repeating the process b to obtain a series of boundary conditions (the total blood flow resistance of each outlet branch vessel corresponds to a group of boundary conditions).
CFD simulation calculation
Applying 7 groups of boundary conditions obtained in the step 2 to the 3D model of the stenotic lesion obtained in the step 1; and calculating the steady-state blood flow distribution condition corresponding to each boundary condition by using CFD simulation. The simulation calculation can be performed by adopting open source CFD platforms such as OpenFOAM and the like, and can also be performed by adopting commercial CFD calculation software such as Fluent and CFX.
4. Parameter extraction and blood flow resistance assessment
a. Respectively extracting blood pressure values at the front end and the rear end of the stenotic lesion and blood flow flowing through the stenotic lesion from the results of the 7 times of simulation calculation; the blood pressure difference between the front end and the rear end of the stenotic lesion is the pressure drop under the corresponding condition of the stenotic lesion; so that 7 groups of pressure drop-blood flow values can be obtained;
b. the 7 groups of pressure drop-blood flow values form a pressure drop-blood flow curve, and nonlinear regression analysis is carried out on the pressure drop-blood flow curve according to the following formula to obtain parameters f and s:
wherein
In order to be able to reduce the pressure drop,
the blood flow is shown, and f and s are parameters to be regressed; as shown in fig. 4, the values of pressure drop-blood flow (dotted data) obtained by simulation of 20 cases (three groups according to different stenosis degrees) and the curves (curves) obtained after regression according to the formula (1) are shown.
c. For the two obtained parameters, the area under the pressure drop-blood flow curve is respectively calculated according to the following formula:
respectively taking q as 1ml/S and 2ml/S, and calculating two area values S1And S2；
According to the invention, two parameters f and S directly related to the blood flow resistance are calculated based on the cCTA and the CFD, and two parameters S1 and S2 indirectly related to the blood flow resistance are further obtained based on the f and the S, so that the physical significance of each parameter is clear, and the calculation of related parameters which can be used for representing the inherent physical characteristics of the blood flow resistance based on the cCTA image is realized.
Claims (1)
1. The narrow focus blood flow resistance calculation method based on coronary artery CT angiography comprises the following steps:
(1) performing coronary artery three-dimensional reconstruction based on the cCTA image, and extracting a 3D model of a stenotic lesion;
(2) 7 sets of boundary conditions were constructed for different total blood flow conditions: (a) the total blood flow resistance of the outlet branch vessel is initially set to 240(mmHg s/cm)3) Distributing the total blood flow resistance to each branch outlet according to the rule that the blood flow resistance is inversely proportional to the blood vessel radius power; (b) reducing the total blood flow resistance of the outlet branch blood vessel to 87.5%, 75.0%, 62.5%, 50.0%, 37.5% and 25.0% of the initial value in sequence, and repeating the process b to obtain a series of boundary conditions;
(3) applying 7 groups of boundary conditions obtained in the step 2 to the 3D model of the stenotic lesion obtained in the step (1), and simulating and calculating corresponding steady-state blood flow distribution conditions under each boundary condition by using a Computational Fluid Dynamics (CFD) method;
(4) extracting a pressure drop-blood flow curve from the 7 times simulation result, carrying out nonlinear regression analysis on the curve according to the following formula, and solving parameters f and s:
wherein
In order to be able to reduce the pressure drop,
the blood flow is shown, and f and s are parameters to be regressed; for the two extracted parameters f and s, the area under the pressure drop-blood flow curve is respectively calculated according to the following formula:
respectively taking q as 1ml/S and 2ml/S, and calculating two area values S1And S2；
(5) f, S, S1 and S2 are the blood flow resistance parameters obtained by calculation.
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| CN109770930B (en) * | 2019-01-29 | 2021-03-09 | 浙江大学 | Method and device for determining coronary artery microcirculation resistance |
| CN110916640B (en) * | 2019-11-06 | 2023-04-14 | 唯智医疗科技(佛山)有限公司 | FFR-based coronary artery stenosis functional ischemia detection method and device |
| CN112535466A (en) * | 2020-12-16 | 2021-03-23 | 成都全景恒升科技有限公司 | Blood flow reserve fraction calculation method based on blood vessel image |
| CN113017667A (en) * | 2021-02-05 | 2021-06-25 | 上海市第六人民医院 | Method, device and equipment for quantifying vascular stenosis and readable storage medium |
| CN113693579A (en) * | 2021-07-23 | 2021-11-26 | 西北工业大学 | Normalized coronary artery microcirculation resistance index calculation method |
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