Physical modeling method of ablation catheter

Abstract

The invention provides a physical modeling method for an ablation catheter, and the method comprises the steps: enabling the ablation catheter to be regarded as a continuous spiral structure, carrying out the discretization processing, obtaining a plurality of segments of sub-models, and describing the spatial pose of each segment of sub-model through a mass center position and a rotation quaternion; determining constraint conditions of the kinematic model based on description of the spatial pose, describing the kinematic model through a Lagrangian multiplier method with the constraint conditions to obtain a motion representation equation of the ablation catheter, and solving the equation to obtain a motion simulation result of the catheter; based on a motion simulation result, tracking the tail end position of the ablation catheter through an X-ray image; and estimating the shape of the ablation catheter in real time through an inverse kinematics algorithm by utilizing the tail end position of the ablation catheter obtained through tracking. According to the method, the shape of the catheter is estimated in real time through catheter tail end position tracking, the accuracy and convenience of ablation catheter modeling are improved, and the modeling efficiency is improved.

Description

Technical Field

[0001] The present application relates to the technical field of physical simulation of medical equipment, and in particular to a physical modeling method of an ablation catheter. Background Art

[0002] Radiofrequency catheter ablation is a widely used, minimally invasive procedure used to treat cardiac arrhythmias when medications have failed to restore normal heart rhythm. During the procedure, a steerable catheter is inserted into the heart and uses radiofrequency energy (RF) to ablate the target area, blocking abnormal electrical signals.

[0003] Among them, the physical modeling of the ablation catheter is a key factor in catheter ablation simulation and surgical navigation based on it. However, the process of constructing a physical model using the modeling method in the related art is relatively cumbersome, and the computational cost of modeling is relatively high. For example, the empirical rigid connection model can cope with situations where the curvature is variable, but the model parameters need to be experimentally adjusted according to different catheters and bending configurations, and the modeling process and model parameters are relatively complex. For another example, the model constructed by the large deflection modeling method for flexible bodies can cope with variable curvature under large deflections. However, the prediction from external force to shape deflection requires numerical integration, which has a high computational cost and is not convenient for practical application. Summary of the invention

[0004] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0005] To this end, the first purpose of the present application is to propose a physical modeling method for an ablation catheter, which utilizes catheter tip position tracking to estimate the catheter shape in real time, thereby improving the accuracy and convenience of ablation catheter modeling and improving modeling efficiency.

[0006] The second objective of the present application is to provide a physical modeling device for an ablation catheter.

[0007] A third object of the present application is to provide a non-transitory computer-readable storage medium.

[0008] To achieve the above-mentioned purpose, a first aspect of the present application provides a physical modeling method for an ablation catheter, comprising the following steps:

[0009] The kinematic model of the ablation catheter is regarded as a continuous spiral structure, and the continuous spiral structure is discretized to obtain a multi-segment sub-model, and the spatial position of each segment sub-model is described by the bending and torsion deformation rate, center of mass position and rotation quaternion of each segment sub-model;

[0010] Determine the constraints of the kinematic model based on the description of the spatial posture, describe the kinematic model by the Lagrange multiplier method with the constraints, obtain the motion representation equation of the ablation catheter, and solve the motion representation equation to obtain the motion simulation result of the ablation catheter;

[0011] Based on the motion simulation results, position tracking of the ablation catheter tip is performed through an X-ray image of a C-arm imaging system;

[0012] The position of the ablation catheter end obtained by tracking is used to estimate the shape of the ablation catheter in real time through an inverse kinematics algorithm to construct a three-dimensional physical model of the ablation catheter.

[0013] Optionally, in one embodiment of the present application, the spatial posture of each sub-model is described by the bending and torsion deformation rate, center of mass position and rotation quaternion of each sub-model, including: for any sub-model, determining the curve expression of the center line of the model; determining the right-handed orthogonal coordinate system corresponding to the point on the center line, and calculating the spatial derivative of the coordinate axis direction of the right-handed orthogonal coordinate system; determining the Darboux vector according to the spatial derivative and the coordinate axis direction, and determining the bending deformation rate and the torsion deformation rate based on the Darboux vector.

[0014] Optionally, in one embodiment of the present application, the spatial posture of each sub-model is described by the deformation rate of bending and torsion, the center of mass position and the rotation quaternion of each sub-model, and also includes: dividing the center line into multiple discrete spatial control points, and constructing a center line element according to two adjacent spatial control points; for any center line element, the direction of the center line element is represented by a rotation quaternion to describe the bending or rotation of any center line element.

[0015] Optionally, in one embodiment of the present application, determining the constraint conditions of the kinematic model based on the description of the spatial posture includes:

[0016] The first coordinate axis direction of the right-handed orthogonal coordinate system is parallel to the tangent direction of the center line as a first integrity constraint condition, wherein the first integrity constraint condition is expressed by the following formula:

[0017]

[0018] Among them, r′ represents the spatial derivative of the center line, and d1 represents the direction of the first coordinate axis;

[0019] The rotation quaternion is normalized to generate a second integrity constraint condition, wherein the second integrity constraint condition is expressed by the following formula:

[0020] C q=||q||-1=0

[0021] Where q represents the rotation quaternion.

[0022] Optionally, in one embodiment of the present application, the motion representation equation of the ablation catheter is expressed by the following formula:

[0023]

[0024] Among them, T represents kinetic energy, V represents potential energy, D represents dissipated energy, and F e is the total external torque, g i ∈{r x ,r y ,r z ,q1,q2,q3,q4} represent generalized coordinates, Yes i The time derivative of , λ and μ represent different constraint coefficients respectively.

[0025] Optionally, in one embodiment of the present application, the real-time estimation of the shape of the ablation catheter by an inverse kinematics algorithm includes:

[0026] Constructing a forward dynamics model of the ablation catheter, wherein in the forward dynamics model, the center of mass positions and rotation states of all sub-models jointly determine the coordinates of the end of the ablation catheter;

[0027] The forward dynamics model is reversely deduced, and the position of the end of the ablation catheter obtained by tracking is substituted into the inverse kinematics algorithm to solve the center of mass position and rotation quaternion parameters of each sub-model of the ablation catheter, wherein the optimization objective function in the inverse kinematics algorithm is expressed by the following formula:

[0028]

[0029] Wherein, q is the tracked position of the end of the ablation catheter, f(θ) is the current position estimate of the end of the ablation catheter, and θ is the rotation angle parameter, which is obtained by inverse motion solution.

[0030] To achieve the above-mentioned purpose, the second embodiment of the present application proposes a physical modeling device based on an ablation catheter of the present invention, comprising the following modules:

[0031] A discrete module is used to regard the kinematic model of the ablation catheter as a continuous spiral structure, discretize the continuous spiral structure, obtain multiple sub-models, and describe the spatial position of each sub-model through the bending and torsion deformation rate, center of mass position and rotation quaternion of each sub-model;

[0032] A constraint module, used for determining the constraint conditions of the kinematic model based on the description of the spatial posture, describing the kinematic model by a Lagrange multiplier method with the constraint conditions, obtaining the motion representation equation of the ablation catheter, and solving the motion representation equation to obtain the motion simulation result of the ablation catheter;

[0033] A position tracking module, used for tracking the position of the ablation catheter tip through an X-ray image of a C-arm imaging system based on the motion simulation result;

[0034] The construction module is used to use the tracking obtained ablation catheter end position to estimate the shape of the ablation catheter in real time through an inverse kinematics algorithm to construct a three-dimensional physical model of the ablation catheter.

[0035] To achieve the above objectives, the third aspect of the present application further proposes a non-temporary computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the physical modeling method of the ablation catheter in the above embodiment is implemented.

[0036] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects: the present application first regards the ablation catheter as a continuous spiral structure, discretizes the structure, and the spatial pose of each segment of the model is described by the center of mass position and the rotation quaternion. Then, after the ablation catheter is segmented, a constraint relationship between the segments is established. The position of the catheter end is then estimated from the X-ray image. Finally, the catheter end position tracking is used to estimate the ablation catheter shape parameters in real time, thereby obtaining the ablation catheter shape. Therefore, the present application can use the catheter end position tracking to estimate the ablation catheter shape in real time. On the basis of ensuring the accuracy of the constructed physical model, it reduces the complexity of the ablation catheter physical modeling process, improves the modeling efficiency, reduces the computing resources consumed by the modeling, is easy to implement in practical applications, and provides technical support for catheter ablation simulation and surgical navigation based on this.

[0037] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0039] Figure 1 A flow chart of a physical modeling method for an ablation catheter proposed in an embodiment of the present application;

[0040] Figure 2 A schematic diagram of a multi-segment kinematic model of an ablation catheter proposed in an embodiment of the present application;

[0041] Figure 3 A schematic diagram of a discretized spiral structure proposed in an embodiment of the present application;

[0042] Figure 4 A schematic diagram of extracting a sub-model of a discretized spiral structure proposed in an embodiment of the present application;

[0043] Figure 5 A schematic diagram of a certain sub-model proposed in an embodiment of the present application;

[0044] Figure 6 A schematic diagram of the spatial posture description of a discretized spiral structure proposed in an embodiment of the present application;

[0045] Figure 7 A schematic diagram of a three-dimensional physical model of an ablation catheter located in an atrium proposed in an embodiment of the present application;

[0046] Figure 8 A schematic diagram of the structure of a physical modeling device for an ablation catheter proposed in an embodiment of the present application. DETAILED DESCRIPTION

[0047] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0048] A physical modeling method and device for an ablation catheter according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0049] Figure 1 This is a flow chart of a physical modeling method for an ablation catheter proposed in an embodiment of the present application, such as Figure 1 As shown, the method comprises the following steps:

[0050] Step S101, the kinematic model of the ablation catheter is regarded as a continuous spiral structure, the continuous spiral structure is discretized to obtain multiple sub-models, and the spatial position of each sub-model is described by the bending and torsion deformation rate, center of mass position and rotation quaternion of each sub-model.

[0051] Specifically, the ablation catheter of the material model to be established is regarded as a continuous spiral structure, the structure is discretized, and the spatial posture of each segment of the model is described by the center of mass position and rotation quaternion of the model.

[0052] For example, Figure 2A schematic diagram of a multi-section kinematic model of an ablation catheter is proposed for the embodiment of the present application. The multi-section model assumes that the bending of a single section is located in a single two-dimensional plane, and the rotation combination of multiple two-dimensional planes represents the three-dimensional shape of the catheter. Further, after the continuous helical structure is discretized, as shown in FIG. Figure 3 As shown in Figure 2, for the kinematic model of a single-section spiral structure, the continuous spiral structure is discretized into various sub-models, namely Figure 3 The segments in the spiral structure are represented by different grayscales, and the spatial position of each sub-model is described by the center of mass position and rotation quaternion. The spiral structure realizes the flexibility and variable stiffness of the ablation catheter through compression.

[0053] The following is a detailed description of the process by which the spatial pose of each sub-model is described by the center of mass position and rotation quaternion of the sub-model.

[0054] In one embodiment of the present application, the spatial position of each sub-model is described by the bending and torsional deformation rate, center of mass position and rotation quaternion of each sub-model, including: for any sub-model, determining the curve expression of the center line of the model; determining the right-handed orthogonal coordinate system corresponding to the point on the center line, and calculating the spatial derivative of the coordinate axis direction of the right-handed orthogonal coordinate system; determining the Darboux vector according to the spatial derivative and the coordinate axis direction, and determining the bending deformation rate and the torsional deformation rate based on the Darboux vector.

[0055] Specifically, in this embodiment, if Figure 4 As shown, in the discretized spiral structure, any segment ( Figure 4 The spatial position description process of the sub-model is illustrated by way of example. Assuming that the structure of the selected segment is as follows Figure 5 As shown, first determine the center line of the segment and regard it as a smooth curve: r(σ) = (r x (σ),r y (σ),r z (σ) T , determine the curve expression as r(σ):[0,1]→R 3 , where R is a real number representing the spatial coordinate value, that is, the curve expression specifies a spatial position r(σ) for each line element value σ∈[0,1] on the center line of the elastic thin rod.

[0056] like Figure 5 As shown, there is a right-handed orthogonal coordinate system at each point on the center line of the elastic thin rod. The coordinate axis directions of this coordinate system are d1(σ), d2(σ) and d3(σ), and the three coordinate axis directions are perpendicular to each other. k ,k=1,2,3 spatial derivative dk ' represents the degree of spatial bending and twisting of the segment.

[0057] Furthermore, the spatial derivative d k ′ can be expressed by the following formula: k ′=u×d k , k = 1, 2, 3. Among them, vector u is the Darboux vector. The Darboux vector can express the bending deformation rate and torsional deformation rate through the following formula:

[0058] u k =u·d k ,k=1,2,3

[0059] Among them, the values ​​of u1 and u2 represent the deformation rates in the two bending directions, and the value of u3 measures the torsional deformation rate.

[0060] Furthermore, in the present embodiment, the spatial posture of each sub-model is described by the deformation rate of bending and torsion, the center of mass position and the rotation quaternion of each sub-model, and also includes: dividing the center line into multiple discrete spatial control points, and constructing a center line element according to two adjacent spatial control points; for any center line element, the direction of the center line element is represented by a rotation quaternion to describe the bending or rotation of any center line element.

[0061] Specifically, the center line in the above embodiment is divided into N discrete spatial control points r i , the spatial control point can be expressed by the following formula: i = r(σ i ,t)∈R 3 ,i∈[1,N]. Then, r i r i+1 As a unit on the center line of the spiral structure, it is called a center line element. Then the direction of each center line element is expressed by its quaternion q j ,j∈[1,N-1] indicates that, quaternion is used to represent three-dimensional rotation. In this embodiment, the bending or rotation of this section of the structure is described by the rotation quaternion of the center line element. When determining the rotation quaternion, the center of mass position is determined.

[0062] Therefore, after describing the discretized spiral structure according to the above embodiment, the following can be obtained: Figure 6 This step realizes the method of determining the center of mass position and rotation quaternion representation of each sub-model.

[0063] Step S102, based on the description of the spatial posture, the constraints of the kinematic model are determined, the kinematic model is described by the Lagrange multiplier method with constraints, the motion representation equation of the ablation catheter is obtained, and the motion representation equation is solved to obtain the motion simulation result of the ablation catheter.

[0064] Specifically, after the ablation catheter is segmented in the manner of the previous step, a constraint relationship between the segments is established, and the motion simulation result of the ablation catheter is determined based on the constraint relationship. That is, the motion model of the catheter is described by the Lagrangian motion equation with constraint conditions, wherein the constraint conditions are determined according to the spatial posture description of the previous step.

[0065] In one embodiment of the present application, the constraints of the kinematic model are determined based on the description of the spatial posture, including: making the direction of the first coordinate axis of the right-handed orthogonal coordinate system parallel to the direction of the center line tangent as a first integrity constraint; and normalizing the rotation quaternion to generate a second integrity constraint.

[0066] Specifically, based on the description of the spatial posture of each sub-model in the embodiment of the previous step, its motion model needs to have two integrity constraints.

[0067] The first one is that d1(σ) is parallel to the tangent direction of the center line, thus forming the first integrity constraint, which is expressed by the following formula:

[0068]

[0069] Among them, r′ represents the spatial derivative of the center line, and d1 represents the direction of the first coordinate axis.

[0070] This constraint couples the position of the particle on the centerline of the catheter and the direction of the centerline element.

[0071] The second type is that since the normalized quaternion can simply represent the rotation, the second integrity constraint is formed. The constraint is expressed by the following formula:

[0072] C q =||q||-1=0

[0073] Where q represents the rotation quaternion.

[0074] This constraint is to ensure that the quaternion represents the correct rotation.

[0075] Furthermore, by introducing the above constraints into the motion of the ablation catheter and using the Lagrange multiplier method, the following formula can be obtained to express the motion equation of the ablation catheter:

[0076]

[0077] Among them, T represents kinetic energy, V represents potential energy, D represents dissipated energy, and F e is the total external torque, g i ∈{r x ,r y ,r z ,q1,q2,q3,q4} represent generalized coordinates, Yes i The time derivative of , λ and μ represent different constraint coefficients respectively.

[0078] Then, by solving the equation, the catheter motion state and displacement update can be obtained, and the catheter motion simulation result can be obtained.

[0079] Step S103 : Based on the motion simulation result, the position of the ablation catheter tip is tracked through the X-ray image of the C-arm imaging system.

[0080] Among them, the C-arm imaging system is a digital imaging system designed specifically for the medical field. It uses full digital imaging technology and integrates image acquisition, processing, transmission, storage and display functions.

[0081] Specifically, since catheter ablation is usually performed under the X-ray guidance of a C-arm imaging system, the present application is based on the existing detection method and measurement method of the C-arm imaging system in the related art, and then uses the ablation catheter motion simulation result obtained in step S102 to continuously track the terminal position of the ablation catheter.

[0082] As a possible implementation, estimating the position of the catheter tip from an X-ray image includes the following steps: First, the catheter tip is detected in two dimensions on a single projection of the X-ray image by image filtering and template matching methods. Second, the deformable three-dimensional catheter model is adjusted using the projection geometry and two-dimensional similarity measurement method provided by the C-arm system to achieve position tracking of the catheter tip.

[0083] It should be noted that in the above-mentioned implementation method of end position tracking, the ablation catheter motion simulation result obtained in step S102 is used as a restriction. During the position tracking process, the end position of the three-dimensional catheter model is estimated by expressing the catheter motion equation with constraints. This not only can estimate the end position of the tail segment sub-model of the three-dimensional catheter model, but also based on the constraints in the motion simulation results, it can help to estimate the end position of each segment in the catheter model, thereby improving the accuracy and robustness of the ablation catheter end position tracking.

[0084] Step S104: using the tracked position of the ablation catheter tip, the shape of the ablation catheter is estimated in real time through an inverse kinematics algorithm to construct a three-dimensional physical model of the ablation catheter.

[0085] Specifically, the inverse kinematics method is used to track the position of the catheter end to estimate the shape parameters of the ablation catheter in real time, thereby obtaining the shape of the ablation catheter and modeling a three-dimensional physical model of the ablation catheter.

[0086] In one embodiment of the present application, the shape of the ablation catheter is estimated in real time by an inverse kinematics algorithm, including the following steps: first, a forward dynamics model of the ablation catheter is constructed, wherein in the forward dynamics model, the center of mass position and rotation state of all sub-models jointly determine the coordinates of the end of the ablation catheter.

[0087] Specifically, the centroid positions and rotation states of all segments of the ablation catheter comprehensively determine the coordinates of the end of the ablation catheter, that is, x=f(θ), where x is the coordinate of the end of the ablation catheter, θ=(θ1,…,θ n ) T Represents the rotation angle parameter of each segment of the ablation catheter. Assuming that the ablation catheter has n segments, that is, n sub-models, the forward dynamics model of the ablation catheter is thus constructed.

[0088] Then, the forward dynamics model is reversely deduced, and the position of the end of the ablation catheter obtained by tracking is substituted into the inverse kinematics algorithm to solve the center of mass position and rotation quaternion parameters of each sub-model of the ablation catheter. The optimization objective function in the inverse kinematics algorithm is expressed by the following formula:

[0089]

[0090] Wherein, q is the tracked position of the end of the ablation catheter, f(θ) is the current position estimate of the end of the ablation catheter, and θ is the rotation angle parameter, which is obtained by inverse motion solution.

[0091] Specifically, according to the position of the ablation catheter tip obtained by position tracking, the center of mass position and rotation quaternion parameters of all segments of the catheter can be solved using the inverse kinematics method. Since the representation method of the spatial posture of each segment has been determined in step S101, after solving the center of mass position and rotation quaternion parameters of each segment, the spatial posture of each segment of the catheter solved by inverse dynamics is realized, and the posture of each segment is integrated to construct a physical model.

[0092] In the solution process, the optimization target is set as shown in the above function, where q in the formula is the position of the ablation catheter end tracked in step S103, and f(θ) is the current real-time position estimate of the ablation catheter end obtained by solving the inverse kinematics algorithm.

[0093] It should be noted that the process of solving the center of mass position and rotation quaternion parameters through the inverse kinematics algorithm can refer to the inverse kinematics solution algorithm in the relevant technology. The present application does not limit the implementation process of solving using inverse kinematics. The following is only an illustrative description of one possible implementation method.

[0094] As an example, when calculating the current position estimate of the end of the ablation catheter, the gradient descent method is used to calculate the gradient Consider the rotation angle θ of the end position of the ablation catheter to a certain segment i i The gradient (θ i is the three-dimensional Euler angle), the rotation angle θ i Disassemble it into three angles rotating around the x-axis, y-axis and z-axis, let it be θ i,j This joint can be regarded as a combination of three small joints, each of which can only rotate around one axis, so it is only necessary to calculate the partial derivative of the rotation angle of each small joint by the following formula:

[0095]

[0096] Among them, r i,j is the unit vector of the rotation axis of the i-th segment in the world coordinate system, o i is the coordinate of the i-th segment in the world coordinate system.

[0097] Thus, the rotation angle of segment i can be calculated, and the other segments in the ablation catheter can be calculated in the same manner as above, thereby the shape parameters of each segment of the ablation catheter can be estimated in real time, thereby constructing a physical model.

[0098] For example, taking the corresponding left atrium 3D model reconstructed from the fused other modality images as an example, the shape of the ablation catheter is estimated in real time according to the tracking end position, and the 3D physical model of the ablation catheter inserted into the atrium is constructed as follows: Figure 7 As shown in FIG. 1 , RSPV, RIPV and LIPV represent the right superior pulmonary vein, right inferior pulmonary vein and left inferior pulmonary vein in the atrium, respectively, and different grayscales are used to represent different regions in the three-dimensional model. Figure 7 It can be seen that based on the modeling method in the above embodiment, the real-time shape of the ablation catheter inserted into the atrium can be constructed. In addition, the real-time bipolar potential map corresponding to the catheter can also be determined as needed.

[0099] In summary, the physical modeling method of the ablation catheter of the embodiment of the present application first regards the ablation catheter as a continuous spiral structure, discretizes the structure, and the spatial pose of each segment of the model is described by the center of mass position and the rotation quaternion. Then, after the ablation catheter is segmented, a constraint relationship between the segments is established. The position of the catheter end is then estimated from the X-ray image. Finally, the catheter end position tracking is used to estimate the shape parameters of the ablation catheter in real time, thereby obtaining the shape of the ablation catheter. Therefore, this method can use the catheter end position tracking to estimate the shape of the ablation catheter in real time. On the basis of ensuring the accuracy of the constructed physical model, it reduces the complexity of the ablation catheter physical modeling process, improves the modeling efficiency, reduces the computing resources consumed by the modeling, is easy to implement in practical applications, and provides technical support for catheter ablation simulation and surgical navigation based on this.

[0100] In order to implement the above embodiment, the present application also proposes a physical modeling device for an ablation catheter. Figure 8 A schematic diagram of the structure of a physical modeling device for an ablation catheter proposed in an embodiment of the present application.

[0101] like Figure 8 As shown, the apparatus includes a discrete module 100 , a constraint module 200 , a position tracking module 300 and a construction module 400 .

[0102] Among them, the discrete module 100 is used to regard the kinematic model of the ablation catheter as a continuous spiral structure, discretize the continuous spiral structure, obtain multiple sub-models, and describe the spatial posture of each sub-model through the bending and torsion deformation rate, center of mass position and rotation quaternion of each sub-model.

[0103] The constraint module 200 is used to determine the constraint conditions of the kinematic model based on the description of the spatial posture, describe the kinematic model through the Lagrange multiplier method with constraint conditions, obtain the motion representation equation of the ablation catheter, and solve the motion representation equation to obtain the motion simulation result of the ablation catheter.

[0104] The position tracking module 300 is used to track the position of the end of the ablation catheter through the X-ray image of the C-arm imaging system based on the motion simulation result.

[0105] The construction module 400 is used to estimate the shape of the ablation catheter in real time by using the position of the end of the ablation catheter obtained by tracking through an inverse kinematics algorithm, so as to construct a three-dimensional physical model of the ablation catheter.

[0106] Optionally, in one embodiment of the present application, the discrete module 100 is specifically used to: for any sub-model, determine the curve expression of the center line of the model; determine the right-handed orthogonal coordinate system corresponding to the point on the center line, and calculate the spatial derivative of the coordinate axis direction of the right-handed orthogonal coordinate system; determine the Darboux vector according to the spatial derivative and the coordinate axis direction, and determine the bending deformation rate and the torsional deformation rate based on the Darboux vector.

[0107] Optionally, in one embodiment of the present application, the discrete module 100 is also used to: divide the center line into multiple discrete spatial control points, and construct a center line element based on two adjacent spatial control points; for any center line element, represent the direction of the center line element by a rotation quaternion to describe the bending or rotation of any center line element.

[0108] Optionally, in one embodiment of the present application, the constraint module 200 is specifically used to: make the direction of the first coordinate axis of the right-handed orthogonal coordinate system parallel to the direction of the center line tangent as a first integrity constraint condition; and normalize the rotation quaternion to generate a second integrity constraint condition.

[0109] Optionally, in one embodiment of the present application, the construction module 400 is specifically used to: construct a forward dynamics model of the ablation catheter, wherein, in the forward dynamics model, the center of mass position and rotation state of all sub-models jointly determine the coordinates of the end of the ablation catheter; reversely derive the forward dynamics model, substitute the tracked position of the end of the ablation catheter into the inverse kinematics algorithm, and solve the center of mass position and rotation quaternion parameters of each sub-model of the ablation catheter.

[0110] It should be noted that the description of the above embodiment of the physical modeling method for the ablation catheter is also applicable to the device of this embodiment, and the implementation principle is similar, which will not be repeated here.

[0111] In summary, the physical modeling device of the ablation catheter in the embodiment of the present application can use the catheter end position tracking to estimate the shape of the ablation catheter in real time. On the basis of ensuring the accuracy of the constructed physical model, it reduces the complexity of the ablation catheter physical modeling process, improves the modeling efficiency, reduces the computing resources consumed by the modeling, is easy to implement in practical applications, and provides technical support for catheter ablation simulation and surgical navigation based on this.

[0112] In order to implement the above embodiments, the present invention further proposes a non-temporary computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the physical modeling method of an ablation catheter described in the first aspect of the present application is implemented.

[0113] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0114] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0115] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0116] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute the instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0117] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0118] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0119] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0120] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A physical modeling method for an ablation catheter, characterized in that: The following steps are involved: The kinematic model of the ablation catheter is regarded as a continuous spiral structure, and the continuous spiral structure is discretized to obtain a multi-segment sub-model, and the spatial position of each segment sub-model is described by the bending and torsion deformation rate, center of mass position and rotation quaternion of each segment sub-model; Determine the constraints of the kinematic model based on the description of the spatial posture, describe the kinematic model by the Lagrange multiplier method with the constraints, obtain the motion representation equation of the ablation catheter, and solve the motion representation equation to obtain the motion simulation result of the ablation catheter; Based on the motion simulation results, position tracking of the ablation catheter tip is performed through an X-ray image of a C-arm imaging system; The position of the ablation catheter end obtained by tracking is used to estimate the shape of the ablation catheter in real time through an inverse kinematics algorithm to construct a three-dimensional physical model of the ablation catheter.

2. The physical modeling method of the ablation catheter according to claim 1, characterized in that: The spatial position of each sub-model is described by the bending and torsion deformation rate, center of mass position and rotation quaternion of each sub-model, including: For any sub-model, determine the curve expression of the center line of the model; Determine a right-handed orthogonal coordinate system corresponding to the point on the center line, and calculate the spatial derivative of the right-handed orthogonal coordinate system in the direction of the coordinate axis; A Darboux vector is determined according to the spatial derivative and the coordinate axis direction, and a bending deformation rate and a torsional deformation rate are determined based on the Darboux vector.

3. The physical modeling method of the ablation catheter according to claim 2, characterized in that: The method of describing the spatial position of each sub-model by bending and twisting deformation rate, center of mass position and rotation quaternion of each sub-model also includes: Dividing the center line into a plurality of discrete spatial control points, and constructing a center line element according to two adjacent spatial control points; For any centerline element, the direction of the centerline element is represented by a rotation quaternion to describe the bending or rotation of the centerline element.

4. The physical modeling method of the ablation catheter according to claim 2, characterized in that: The constraint conditions of the kinematic model are determined based on the description of the spatial posture, including: The first coordinate axis direction of the right-handed orthogonal coordinate system is parallel to the tangent direction of the center line as a first integrity constraint condition, wherein the first integrity constraint condition is expressed by the following formula: Among them, r′ represents the spatial derivative of the center line, and d1 represents the direction of the first coordinate axis; The rotation quaternion is normalized to generate a second integrity constraint condition, wherein the second integrity constraint condition is expressed by the following formula: C q =||q||-1=0 Where q represents the rotation quaternion.

5. The physical modeling method of the ablation catheter according to claim 4, characterized in that: The motion equation of the ablation catheter is expressed by the following formula: Among them, T represents kinetic energy, V represents potential energy, D represents dissipated energy, and F e is the total external torque, g i ∈{r x ,r y ,r z ,q1,q2,q3,q4} represent generalized coordinates, Yes i The time derivative of , λ and μ represent different constraint coefficients respectively.

6. The physical modeling method of the ablation catheter according to claim 1, characterized in that: The real-time estimation of the shape of the ablation catheter by using an inverse kinematics algorithm comprises: Constructing a forward dynamics model of the ablation catheter, wherein, in the forward dynamics model, the center of mass positions and rotation states of all sub-models jointly determine the coordinates of the end of the ablation catheter; The forward dynamics model is reversely deduced, and the position of the end of the ablation catheter obtained by tracking is substituted into the inverse kinematics algorithm to solve the center of mass position and rotation quaternion parameters of each sub-model of the ablation catheter, wherein the optimization objective function in the inverse kinematics algorithm is expressed by the following formula: Wherein, q is the tracked position of the end of the ablation catheter, f(θ) is the current position estimate of the end of the ablation catheter, and θ is the rotation angle parameter, which is obtained by inverse motion solution.

7. A physical modeling device for an ablation catheter, characterized in that: include: A discrete module is used to regard the kinematic model of the ablation catheter as a continuous spiral structure, discretize the continuous spiral structure, obtain multiple sub-models, and describe the spatial position of each sub-model through the bending and torsion deformation rate, center of mass position and rotation quaternion of each sub-model; A constraint module, used for determining the constraint conditions of the kinematic model based on the description of the spatial posture, describing the kinematic model by a Lagrange multiplier method with the constraint conditions, obtaining the motion representation equation of the ablation catheter, and solving the motion representation equation to obtain the motion simulation result of the ablation catheter; A position tracking module, used for tracking the position of the ablation catheter tip through an X-ray image of a C-arm imaging system based on the motion simulation result; The construction module is used to use the tracking obtained ablation catheter end position to estimate the shape of the ablation catheter in real time through an inverse kinematics algorithm to construct a three-dimensional physical model of the ablation catheter.

8. The physical modeling device for an ablation catheter according to claim 7, characterized in that: The discrete modules are specifically used for: For any sub-model, determine the curve expression of the center line of the model; Determine a right-handed orthogonal coordinate system corresponding to the point on the center line, and calculate the spatial derivative of the right-handed orthogonal coordinate system in the direction of the coordinate axis; A Darboux vector is determined according to the spatial derivative and the coordinate axis direction, and a bending deformation rate and a torsional deformation rate are determined based on the Darboux vector.

9. The physical modeling device for an ablation catheter according to claim 7, characterized in that: The discrete module is also used for: Dividing the center line into a plurality of discrete spatial control points, and constructing a center line element according to two adjacent spatial control points; For any centerline element, the direction of the centerline element is represented by a rotation quaternion to describe the bending or rotation of the centerline element.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the physical modeling method of the ablation catheter as claimed in any one of claims 1 to 6 is implemented.

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