CN106709902A - Real-time motion simulation method for guide wire under effects of blood flow in minimally invasive vascular interventional surgery - Google Patents

Abstract

The invention relates to a real-time motion simulation method for a guide wire under effects of a blood flow in a minimally invasive vascular interventional surgery. The method comprises steps: 1, data of a vessel part are segmented in advance, and a triangular surface mesh is adopted to model the vessel; 2, the central line of the vessel mesh is solved, a continuous vessel mesh model is discretized to express a combination of a small group of cylindrical small vessels according to the central line, and a directed graph is abstracted; 3, a fluid model is built for each section of small vessel; 4, a fluid calculation matrix is built for the vessel model abstracted as the directed graph on the whole, and the flow and the pressure distribution in the vessel are calculated; 5, a guide wire is modeled, the acting force of the blood flow on the guide wire is calculated and the acting force is applied to a simulation model for the guide wire according to the relative position of the guide wire in the vessel, and the shape of the guide wire is updated; and 6, three-dimensional rendering is carried out on the guide wire. Compared with the prior art, the method of the invention has the advantages of stable calculation, good real-time performance, strong realistic feeling and flexible application and the like.

Description

Real time kinematics emulation mode of the seal wire by blood flow effect in interventional surgery

Technical field

The present invention relates to a kind of analogy method of virtual operation, particularly with regard to being led in a kind of interventional surgery Real time kinematics emulation mode of the silk by blood flow effect.

Background technology

With the high speed development of science and technology, the application of virtual operation is increasing for the modernization of medical treatment is provided to be helped Help.Virtual minimally-invasive vascular operative training system can fast and effeciently help intern to improve surgical skills, allow more Patients with Cardiovascular/Cerebrovascular Diseases can receive Minimally Interventional Therapy.The real time kinematics emulation of seal wire is interventional surgery system A most important part, is also the problem of numerous scholar's research.

In the research process of seal wire real time kinematics emulation, the scholar of early stage is limited to the calculated level use of hardware at that time The geometrical model of non-physical, such as B-spline curves, this non-physical model describe seal wire form from geometric angle, although calculate Speed is fast, but have ignored the physical characteristic of seal wire completely, the stressing conditions of seal wire cannot be also described, so the sense of reality compares Difference；Also other scholars are built to the motion simulation of seal wire using Mass-spring Model, model of elastic rod based on physics etc. Mould, this class physical model considers the physical characteristic of seal wire, and is easy to carry out physics to interacting between seal wire and blood vessel to build Mould, can also reach the requirement of real-time calculating after level of hardware is continued to develop, and compared to non-physical model, in the sense of reality On have than larger lifting, be widely adopted, the scholar such as such as Basdogan exists《Virtual Environments for Medical Training:Graphical and Haptic Simulation of Laparoscopic Common Bile Duct Exploration》The scholars such as the Mass-spring Model, the Tang that are used in one text exist《A realistic elastic rodmodel for real-time simulation of minimally invasive vascular interventions》Model of elastic rod used in one text etc..

But, although seal wire is moved in blood flow in operation, and Most scholars all do not account for seal wire but in blood flow Blood flow effect manual during middle motion；Interventional surgery training system to provide the user one height reduction have The virtual training environment of feeling of immersion, this requires that the seal wire of emulation has physics confidence level very high, therefore is considering seal wire sheet On the basis of the physical attribute of body, in addition it is also necessary to which endovascular blood flow is calculated, the blood flow that analysis seal wire is received during exercise Operative condition.

Will the challenge main to the seal wire real-time simulation that is acted on by blood flow have it is following some：

1) complexity due to flow equation, fluid calculation in itself generally calculates complicated and needs to consume the substantial amounts of time；

2) blood vessel is irregular threedimensional model, and it is relatively difficult to set up fluid model in irregular model, and meeting Increase the complexity of fluid calculation；

3) the physical simulation requirement of seal wire real-time higher, integrating fluid calculation necessarily causes the reduction of simulation efficiency, Even it is difficult to reach in real time；

The content of the invention

The purpose of the present invention is exactly the defect in order to overcome above-mentioned prior art to exist, by simplifying flow equation, not advising Then blood vessel discretization description, using the means such as hardware-accelerated, there is provided one kind calculate stabilization, good real-time, strong sense of reality, answer The real time kinematics emulation mode acted on by blood flow with seal wire in flexible interventional surgery.

The purpose of the present invention can be achieved through the following technical solutions：

The real time kinematics emulation mode that seal wire is acted on by blood flow in a kind of interventional surgery, including following step Suddenly：

The first step, the CT scan image according to patient is partitioned into the data of vascular site in advance, using triangle table veil Lattice are modeled to blood vessel；

Second step, asks for rete vasculosum center of a lattice line, represents continuous blood vessel grid model discretization according to center line It is one group of combination of cylindrical shape thin vessels, and abstract is a digraph；

Each section of thin vessels are set up fluid model by the 3rd step according to Poisson leaf rule, for describing each section of thin vessels The middle flow relation poor with pressure at two ends；

4th step, according to the position relationship between thin vessels, turnover flow one make peace thin vessels two ends pressure differential this A little conditions, fluid calculation matrix is integrally set up to the abstract vascular pattern for digraph, calculates flow and pressure point in blood vessel Cloth；

5th step, is modeled using model of elastic rod to seal wire, and the relative position according to seal wire in the blood vessel, calculates blood flow Active force to seal wire is simultaneously applied on the simulation model of seal wire, updates the form of seal wire；

6th step, three-dimensional rendering is carried out to seal wire.

Continuous grid model discretization is expressed as by one group of set of pipe according to center line, and abstract is one oriented Figure, is expressed as G (N_n, N_e), wherein containing N_nIndividual node and N_eBar side, node is discrete point, while being pipe.

It is as follows to the fluid modeling in each section of thin vessels of cylindrical shape according to Poisson leaf rule in 3rd step：

Wherein, Q represents the flow in this section of blood vessel, and Δ p represents the pressure differential at blood vessel two ends, and L represents this section of length of blood vessel Degree, r represents the radius of blood vessel, and η represents the viscosity coefficient of blood, and R represents this section of resistance of blood vessel, is described by L, r, η；

Described the 4th step medium vessels entirety fluid calculating process is as follows:

41) topological structure of node-abstract blood vessel for after digraph of side matrix description is used：

Wherein, if j-th strip side is from i-th node, A_i,j=1, if j-th strip side is terminated to i-th node, Then A_i,j=-1；

42) due to each node-flow inbound traffics with outflow flow be equal, be therefore indicated as

AQ=0

Wherein Q represents the flow in this section of blood vessel, and A is the node-side matrix for describing vessel topology；

43) and because each section of thin vessels all in fluid have model shown in 3 kinds, the overall fluid meter of whole blood vessel It is expressed as：

CQ=Δs P

Wherein, C is diagonal matrixR_iRepresent i-th section of resistance of blood vessel, wherein i=1n, Δ P It is a column vector, includes the pressure differential of every a line；

44) change p of the blood pressure of heart output between systolic pressure and diastolic pressure is represented using a SIN function_source (t)

Wherein, P₁And P₂Respectively systolic pressure and diastolic pressure, ω are used for the cycle of controlled output pressure；

45) equation listed earlier is integrated, whole blood vessel entirety blood flow calculates procedural representation and is：

Wherein,It is a sparse invertible matrix, P represents the pressure of heart output, and the solution mode of equation is such as Under

Because the value of matrix K is only relevant with the topological structure of blood vessel, and the structure of blood vessel is changeless, therefore K It is inverse to be asked in advance before emulation is started, to improve the speed of emulation.

The step of blood flow is calculated in the 5th described step to the active force of seal wire and the simulation model of seal wire is applied to is as follows：

51) seal wire particle relative position in the blood vessel is searched, the thin vessels belonging to it are determined；The blood vessel of discretization is retouched It is V to state_1~n, all of seal wire particle is described as m_1~n, it is not all for the search of each particle for the speed for accelerating to search Blood vessel, and only to first particle m₁Search for all of blood vessel and find corresponding blood vessel V_1′, and it is any one for follow-up Individual particle m_i, it is only necessary to search for the blood vessel V belonging to a particle_(i-1)′A neighborhood V_(i-1)′±n, that is, it is quickly found out each matter Blood vessel where point；The speed of emulation is effectively improved using this lookup method；

52) position according to particle in the blood vessel, asks for active force of the blood flow on particle, is expressed as follows

X represents distance of the particle in blood vessel axial direction, and d represents distance of the particle in blood vessel radial direction, and Q represents this section Flow in blood vessel, Δ P represents the pressure differential at blood vessel two ends, and r represents the radius of blood vessel, and η represents the viscosity coefficient of blood；

53) effect of blood flow is integrated into the physical simulation of seal wire, the meter of each frame of the seal wire based on model of elastic rod Calculate as follows

Wherein, Δ x and Δ v represent position and the velocity variations of each particle respectively, and Δ t is time interval, and f represents each The Jacobian matrix of the stressing conditions of particle, including the power of push-and-pull, rotation and collision that seal wire is subject to, M is to rely on seal wire One diagonal matrix of the positional information of each particle, v_t,x_tIt is illustrated respectively in speed and the position of t particle；

Add the effect of blood flow as follows on each particle, obtain the seal wire simulation calculation mould by blood flow function influence Type：

Compared with prior art, be integrated into the active force of blood flow in the motion simulation of seal wire by the present invention, with calculating Stabilization, good real-time, strong sense of reality, using it is flexible the advantages of.

Brief description of the drawings

Fig. 1 is flow chart of the invention.

Specific embodiment

The present invention is described in detail with specific embodiment below in conjunction with the accompanying drawings.

Embodiment

The present embodiment realizes that CPU is Intel to strong E3-1230 on a PC, and internal memory 4G, video card reaches for tall and handsome GTX760, implementation is realized for C++ programming languages.

The implementing procedure of the present embodiment is as shown in Figure 1.

The first step, the CT scan image according to patient, is increased using region plus the method for manual setting is partitioned into blood vessel portion The data of position, are modeled using triangle table surface grids by Marching Cubes algorithms to blood vessel；

Second step, asks for rete vasculosum center of a lattice line, represents continuous blood vessel grid model discretization according to center line It is one group of combination of cylindrical shape thin vessels, the small blood of a total of 2477 cylindrical shapes after the blood vessel discretization in the present embodiment Pipe, then uses a digraph abstractdesription；

Each section of thin vessels are set up fluid model by the 3rd step according to Poisson leaf rule, are flowed in each section of thin vessels of description The amount relation poor with pressure at two ends；

4th step, according to the position relationship between thin vessels, turnover flow one make peace thin vessels two ends pressure differential this A little conditions, fluid calculation matrix is integrally set up to the abstract vascular pattern for digraph, calculates flow and pressure point in blood vessel Cloth；Blood flow is accelerated to calculate using Intel's mathematics its main operational storehouse (Intel MKL).

5th step, according to seal wire relative position in the blood vessel, calculates blood flow to the active force of seal wire and is applied to seal wire Simulation model on；

6th step, three-dimensional rendering is carried out using OpenGL to seal wire.

Claims (5)

1. the real time kinematics emulation mode that seal wire is acted on by blood flow in a kind of interventional surgery, including following step Suddenly：

The first step, the CT scan image according to patient is partitioned into the data of vascular site in advance, using triangle table surface grids pair Blood vessel is modeled；

Second step, asks for rete vasculosum center of a lattice line, and continuous blood vessel grid model discretization is expressed as into one according to center line The combination of group cylindrical shape thin vessels, and abstract is a digraph；

Each section of thin vessels are set up fluid model by the 3rd step according to Poisson leaf rule, for describing to be flowed in each section of thin vessels The amount relation poor with pressure at two ends；

4th step, according to the position relationship between thin vessels, turnover flow one make peace thin vessels two ends pressure differential these Part, fluid calculation matrix is integrally set up to the abstract vascular pattern for digraph, calculates flow and pressure distribution in blood vessel；

5th step, is modeled using model of elastic rod to seal wire, and the relative position according to seal wire in the blood vessel, calculates blood flow to leading The active force of silk is simultaneously applied on the simulation model of seal wire, updates the form of seal wire；

6th step, three-dimensional rendering is carried out to seal wire.

2. the real time kinematics emulation side that seal wire is acted on by blood flow in a kind of interventional surgery according to claim 1 Method, it is characterised in that continuous grid model discretization is expressed as by one group of set of pipe according to center line, and abstract is one Individual digraph, is expressed as G (N_n, N_e), wherein containing N_nIndividual node and N_eBar side, node is discrete point, while being pipe.

3. the real time kinematics emulation side that seal wire is acted on by blood flow in a kind of interventional surgery according to claim 1 Method, it is characterised in that according to Poisson leaf rule to the fluid modeling in each section of thin vessels of cylindrical shape in the 3rd step It is as follows：

$Q=\frac{\mathrm{\Δ}p}{R}withR=\frac{8\mathrm{\η}L}{{\mathrm{\πr}}^4}$

Wherein, Q represents the flow in this section of blood vessel, and Δ p represents the pressure differential at blood vessel two ends, and L represents this section of length of blood vessel, r The radius of blood vessel is represented, η represents the viscosity coefficient of blood, and R represents this section of resistance of blood vessel, described by L, r, η.

4. the real time kinematics emulation side that seal wire is acted on by blood flow in a kind of interventional surgery according to claim 1 Method, it is characterised in that described the 4th step medium vessels entirety fluid calculating process is as follows:

41) topological structure of node-abstract blood vessel for after digraph of side matrix description is used：

Wherein, if j-th strip side is from i-th node, A_i,j=1, if j-th strip side is terminated to i-th node, A_i,j =-1；

42) due to each node-flow inbound traffics with outflow flow be equal, be therefore indicated as

AQ=0

Wherein Q represents the flow in this section of blood vessel, and A is the node-side matrix for describing vessel topology；

43) and because each section of thin vessels all in fluid have model shown in 3 kinds, the overall fluid computational chart of whole blood vessel It is shown as：

CQ=Δs P

Wherein, C is diagonal matrixR_iI-th section of resistance of blood vessel is represented, wherein i=1 ... n, Δ P are a row Vector, includes the pressure differential of every a line；

44) change P of the blood pressure of heart output between systolic pressure and diastolic pressure is represented using a SIN function_source(t)

$p_{source}\left(t\right)=\frac{P_1-P_2}{2}\sin \left(\mathrm{\ω}t\right)+\frac{P_1+P_2}{2}$

Wherein, P₁And P₂Respectively systolic pressure and diastolic pressure, ω are used for the cycle of controlled output pressure；

45) equation listed earlier is integrated, whole blood vessel entirety blood flow calculates procedural representation and is：

$\left(\begin{array}{cc}A& 0\\ C& A^T\end{array}\right)\left(\begin{array}{c}Q\\ P\end{array}\right)=\left(\begin{array}{c}0\\ p_{source}\left(t\right)\end{array}\right)$

Wherein,It is a sparse invertible matrix, P represents the pressure of heart output, and the solution mode of equation is as follows

$\left(\begin{array}{c}Q\\ P\end{array}\right)=K^{-1}\left(\begin{array}{c}0\\ p_{source}\left(t\right)\end{array}\right)withK=\left(\begin{array}{cc}A& 0\\ C& A^T\end{array}\right)$

Because the value of matrix K is only relevant with the topological structure of blood vessel, and the structure of blood vessel is changeless, thus K it is inverse Start to be asked in advance before emulation, to improve the speed of emulation.

5. the real time kinematics emulation side that seal wire is acted on by blood flow in a kind of interventional surgery according to claim 1 Method, it is characterised in that blood flow is calculated in the 5th described step to the active force of seal wire and the step of the simulation model for being applied to seal wire It is rapid as follows：

51) seal wire particle relative position in the blood vessel is searched, the thin vessels belonging to it are determined；The blood vessel of discretization is described as V_1~n, all of seal wire particle is described as m_1~n, for the speed for accelerating to search, do not search for all of blood for each particle Pipe, and only to first particle m₁Search for all of blood vessel and find corresponding blood vessel V_1′, and for any one follow-up matter Point m_i, it is only necessary to search for the blood vessel V belonging to a particle_(i-1)′A neighborhood V_(i-1)′±n, that is, it is quickly found out each particle institute Blood vessel；The speed of emulation is effectively improved using this lookup method；

52) position according to particle in the blood vessel, asks for active force of the blood flow on particle, is expressed as follows

$u(x,d)=\frac{1}{4\mathrm{\η}}\frac{\mathrm{\Δ}P}{x}(r^2-d^2)=\frac{2}{{\mathrm{\πr}}^2}Q(1-\frac{d^2}{r^2})$

X represents distance of the particle in blood vessel axial direction, and d represents distance of the particle in blood vessel radial direction, and Q represents this section of blood vessel In flow, Δ P represents the pressure differential at blood vessel two ends, and r represents the radius of blood vessel, and η represents the viscosity coefficient of blood；

53) effect of blood flow is integrated into the physical simulation of seal wire, the calculating of each frame of the seal wire based on model of elastic rod is such as Under

$\left[\begin{array}{c}\mathrm{\Δ}x\\ \mathrm{\Δ}v\end{array}\right]=\mathrm{\Δ}t\left[\begin{array}{c}{v}_t+\mathrm{\Δ}v\\ M^{-1}f(x_t+\mathrm{\Δ}x,v_t+\mathrm{\Δ}v)\end{array}\right]$

Wherein, Δ x and Δ v represent position and the velocity variations of each particle respectively, and Δ t is time interval, and f represents each particle Stressing conditions Jacobian matrix, including seal wire be subject to push-and-pull, rotation and collision power, M be to rely on seal wire each One diagonal matrix of the positional information of particle, v_t,x_tIt is illustrated respectively in speed and the position of t particle；

Add the effect of blood flow as follows on each particle, obtain the seal wire Simulation Calculation by blood flow function influence：

$\left[\begin{array}{c}\mathrm{\Δ}x\\ \mathrm{\Δ}v\end{array}\right]=\mathrm{\Δ}t\left[\begin{array}{c}{v}_t+\mathrm{\Δ}v\\ M^{-1}f(x_t+\mathrm{\Δ}x,v_t+\mathrm{\Δ}v)\end{array}\right]+\left[\begin{array}{c}0\\ u\end{array}\right].$