Three-Dimensional Finite-Element Code for Electerosurgery and Thermal Ablation Simulations

• US 20090070090A1
• Filed: 09/11/2008
• Published: 03/12/2009
• Est. Priority Date: 12/23/2004
• Status: Active Grant

• Current Assignee: Covidien AG (Medtronic Plc)
• Original Assignee: Covidien AG (Medtronic Plc)
• Inventors: Rick, Kyle R., Schechter, David A., Goldberg, Nahum, Humphries, Stanley
• Granted Patent: US 7,702,495 B2
• Time in Patent Office: Days
• US Class Current: 703/11
• CPC Class Codes: G09B 23/30 Anatomical models G09B23/281 - G09B23/288 take precedence

Abstract

A method for performing a simulation of an electrosurgical procedure is provided. The method includes the step of generating a three-dimensional model of a medium comprising one or more material regions representing a physical object or a region of the tissue. The method also includes the step of calculating one of an electrical energy solution and a thermal transport solution based on one of a mathematical model and finite element method. The method further includes the step of updating one or more property values of the material region in response to temperature changes based on an empirically derived value, wherein one of the electrical energy solution and the thermal transport solution is updated as a function of the updated property value.

Claims

1. A method for performing a simulation of an electrosurgical procedure, the method comprising the steps of:

generating a three-dimensional model of a medium including at least one material region representing at least one of a physical object and a region of the tissue;

calculating at least one of an electrical energy solution and a thermal transport solution based on at least one mathematical model and finite element method; and

updating at least one property value of the at least one material region at least once in response to temperature changes based on an empirically derived value, wherein at least one of the electrical energy solution and the thermal transport solution is updated as a function of the at least one property value.

4. The method according to claim 1, wherein the step of calculating the electrical energy solution further comprises a step of solving equations 1 and 2:

$\begin{array}{cc}\nabla <br><br>·<br><br>\left[\left({\mathrm{\varepsilon <br><br>}}_r-\frac{\mathrm{j\sigma <br><br>}}{{\mathrm{\varepsilon <br><br>}}_0<br><br>\mathrm{\omega <br><br>}}\right)<br><br>\nabla <br><br>\mathrm{\phi <br><br>}\right]=0& \left(1\right)\\ E=-\nabla <br><br>\mathrm{\phi <br><br>}& \left(2\right)\end{array}$

wherein ∈

_r is a relative dielectric constant, and σ

is electrical conductivity of each of the elements, j is an imaginary number, ∈

₀ is vacuum permittivity, ω

is angular frequency, φ

is a quasi-static potential, which is a complex number, and E is amplitude and phase of electric field.

5. The method according to claim 4, wherein the step of calculating the thermal transport solution further comprises a step of solving equations 3 and 4:

$\begin{array}{cc}{q}_e=\mathrm{\sigma <br><br>}<br><br><br><br>E·<br><br>E*/2& \left(3\right)\\ {\mathrm{pC}}_p<br><br>\frac{\partial <br><br>T}{\partial <br><br>t}=\nabla <br><br>·<br><br>\left(k<br><br>\nabla <br><br>T\right)+q_e+q_m+W_b<br><br>\left(T_b-T\right)& \left(4\right)\end{array}$

wherein ρ

is density of the medium, Cρ

is specific heat, k is thermal conductivity, qm is heat generated by metabolism, qe is resistive source, and Wb(Tb−

T) represents thermal variations caused by blood flow.

6. The method according to claim 1, wherein the at least one property value is representative of at least one physical property selected from the group consisting of relative dielectric constant, electrical conductivity, specific heat, thermal conductivity and blood flow.

7. The method according to claim 6, wherein the at least one physical property is temperature-dependent.

8. The method according to claim 6, wherein a tabular function stores a plurality of temperature-dependent values for the at least one physical property.

2. The method according to claim 2, further comprising the steps of:

dividing the model of the medium into a plurality of hexahedron elements to generate a three-dimensional conformal mesh;

assigning each element to a corresponding at least one material region; and

calculating at least one of an electrical energy solution and a thermal transport solution based on at least one mathematical model, the plurality of hexahedron elements and finite element method.

3. The method according to claim 2, further comprising the step of:

generating and displaying at least one graphical representation representing at least one form of the electrical energy solution and one form of the thermal transport solution on a output device.

9. The method according to claim 2, wherein the plurality of elements are ordered in the three-dimensional mesh according to cubic logic.

10. The method according to claim 2, wherein the graphical representation is a three-dimensional plot and the at least one form of the thermal solution is an isothermal surface of the medium.

11. The method according to claim 2, wherein the graphical representation is a two dimensional slice plot and the at least one form of the electrical solution is electrical conductivity of the medium.

12. A system for performing a simulation of an electrosurgical procedure on tissue, the system comprising:

at least one processor coupled to a computer-readable media configured to store a set of instructions capable of being executed by the at least one processor, the instructions including the steps of;

generating a three-dimensional model of a medium including at least one material region representing at least one of a physical object and a region of the tissue;

calculating at least one of an electrical energy solution and a thermal transport solution based on at least one mathematical model and finite element method; and

updating at least one property value of the at least one material region at least once in response to temperature changes based on an empirically derived value, wherein at least one of the electrical energy solution and the thermal transport solution is updated as a function of the at least one property value.

13. The system according to claim 12, wherein the instructions further comprise the steps of:

dividing the model of the medium into a plurality of hexahedron elements to generate a three-dimensional conformal mesh;

assigning each element to a corresponding at least one material region; and

calculating at least one of an electrical energy solution and a thermal transport solution based on at least one mathematical model, the plurality of hexahedron elements and finite element method.

14. The system according to claim 12, further comprising:

an output device configured to output at least one graphical representation representing at least one form of the electrical energy solution and one form of the thermal transport solution.

15. The system according to claim 12, wherein the at least one property value is representative of at least one physical property selected from the group consisting of relative dielectric constant, electrical conductivity, specific heat, thermal conductivity and blood flow.

16. The system according to claim 15, wherein the at least one physical property is temperature-dependent.

17. The system according to claim 15 wherein a tabular function stores a plurality of temperature-dependent values for the at least one physical property.

18. A computer-readable storage medium storing a set of computer-executable instructions for performing a simulation of an electrosurgical procedure, the computer-executable instructions comprising the steps of:

generating a three-dimensional model of a medium including at least one material region representing at least one of a physical object and a region of the tissue;

calculating at least one of an electrical energy solution and a thermal transport solution based on at least one mathematical model and finite element method; and

updating at least one property value of the at least one material region at least once in response to temperature changes based on an empirically derived value, wherein at least one of the electrical energy solution and the thermal transport solution is updated as a function of the at least one property value.

19. The computer-readable storage medium according to claim 18, wherein the computer-executable instructions further include the steps of:

dividing the model of the medium into a plurality of hexahedron elements to generate a three-dimensional conformal mesh;

assigning each element to a corresponding at least one material region; and

calculating at least one of an electrical energy solution and a thermal transport solution based on at least one mathematical model, the plurality of hexahedron elements and finite element method.

20. The computer-readable storage medium according to claim 18, wherein the computer-executable instructions further include the step of:

generating and displaying at least one graphical representation representing at least one form of the electrical energy solution and one form of the thermal transport solution on a output device.