Virtual prototyping and testing for medical device development

• US 7,840,393 B1
• Filed: 10/04/2000
• Issued: 11/23/2010
• Est. Priority Date: 10/04/2000
• Status: Active Grant

• Current Assignee: Endologix
• Original Assignee: Trivascular Incorporated
• Inventors: Chobotov, Michael V., Whirley, Robert G.
• Primary Examiner(s): PROCTOR, JASON SCOTT
• Application Number:
  US09/679,725
• Time in Patent Office: 3,702 Days
• Field of Search: 345/419, 345/619, 700/98, 700/118, 700/182, 702/19, 703/6, 703/2, 703/11, 703/1, 703/7, 706/919, 706/920, 706/924, 600/416, 600/36, 623/1.1, 623/1.13, 623/1.14, 623/901, 434/266, 434/268, 434/272
• US Class Current: 703/7
• CPC Class Codes: A61F 2/82 Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents stent-grafts for tubular structures of the body other than blood vessels A61F2/04; stent-grafts for blood vessels A61F2/07; instruments specially adapted for placement or removal of stents or stent-grafts A61F2/95; for closing wounds, or holding wounds closed A61B17/04 - A61B17/115; dilators A61M29/00
• CPC Class Codes: G06F 30/00 Computer-aided design [CAD]
• CPC Class Codes: G06G 7/48 Analogue computers for specific processes, systems or devices, e.g. simulators
• CPC Class Codes: G09B 23/28 for medicine

Abstract

A system and method of developing better-designed medical devices, particularly cardiovascular stents and endovascular grafts. The system comprises a geometry generator, a mesh generator, a stress/strain/deformation analyzer, and a visualization tool. In one embodiment, the geometry generator receives three-dimensional volumetric data of an anatomical feature and generates a geometric model. The mesh generator then receives such geometric model of an anatomical feature or an in vitro model and a geometric model of a candidate medical device. In another embodiment, the mesh generator only receives a geometric model of the candidate medical device. Using the geometric model(s) received, the mesh generator creates or generates a mesh or a finite element model. The stress/strain/deformation analyzer then receives the mesh, and the material models and loads of that mesh. Using analysis, preferably non-linear analysis, the stress/strain/deformation analyzer determines the predicted stresses, strains, and deformations on the candidate medical device. Such stresses, strains, and deformations may optionally be simulated visually using a visualization tool.

Claims

1. A computer system including at least one processor and memory for analyzing medical devices comprising:

a geometry generator that receives three-dimensional volumetric data of at least one anatomical feature(s) of at least one vascular system and generates a geometric model of said anatomical feature(s);

a mesh generator that receives said geometric model of said anatomical feature(s) and a geometric model of a medical device, and generates a finite element model representing both of said geometric model of said anatomical feature(s) and said geometric model of said medical device; and

a stress/strain/deformation analyzer that receives said finite element model, material properties of said anatomical feature(s) and said medical device, load data on said anatomical feature(s) and/or said medical device and simulates an interaction between said anatomical feature(s) and said medical device over at least one dynamic expansion and contraction cycle of the anatomical feature(s) to determine the predicted stresses, strains, and deformations of said medical device due to the interaction of the medical device with the anatomical feature(s).

2. The system of claim 1 wherein said geometric model of said anatomical feature(s) is an idealized geometric model.

3. The system of claim 1 wherein said three-dimensional volumetric data are acquired via CT scan.

4. The system of claim 1 wherein said three-dimensional volumetric data are acquired via MRI.

5. The system of claim 1 wherein said medical device is an endovascular prosthesis.

6. The system of claim 5 wherein said endovascular prosthesis is a stent graft.

7. The system of claim 5 wherein said endovascular prosthesis is a cardiovascular stent.

8. The system of claim 1 wherein said geometry generator is a software application which generates surface points from the three-dimensional volumetric data, which are then converted into stereolithography, slice files, IGES files or a combination thereof.

9. The system of claim 1 wherein said mesh generator includes three-dimensional finite modeling software.

10. The system of claim 1 wherein said stress/strain/deformation analyzer is a non-linear finite element modeling software application.

11. The system of claim 9 wherein said three dimensional finite modeling software tessellates a geometric model into hexahedron brick elements and quadrilateral shell elements to create the model.

12. The system of claim 10 wherein said non-linear finite element modeling software application is configured to accommodate a strain energy density of the form:

W=a₁₀(I₁−

3)+a₀₁(I₂−

3)+a₂₀(I₁−

3)²+a₁₁(I₁−

3)(I₂−

3)+a₀₂(I₂−

3)²+a₃₀(I₁−

3)+a₂₁(I₁−

3)²(I₂−

3)+a₁₂(I₁−

3)(I₂−

3)²+a₀₃(I₂−

3)³+½

K(I₃−

1)²

with K=2(a₁₀+a₀₁)/(1−

2v) where

a_ij are material parameters;

v is Poisson'"'"'s ratio;

K is the bulk modulus given as a function of Poisson'"'"'s ratio; and

I₁, I₂, and I₃ are the first, second, and third invariants of the right Cauchy-Green strain tensor, respectively.

13. The system of claim 1 further comprising a visualization tool that receives said simulated stresses, strains, and deformations of said medical device from said stress/strain/deformation analyzer and displays one or more of said stresses, strains, and deformations of said medical device via visual representation.

14. The system of claim 13 wherein said visualization tool includes interactive software for visualizing finite element analysis results of three-dimensional grids.

15. The system of claim 1 wherein said stress/strain/deformation analyzer uses a non-linear finite element analysis tool to simulate said stresses, strains, and deformations of said medical device.

16. The system of claim 1 wherein said simulated stresses, strains, and deformations imposed on said medical device comprise dynamic or quasi-static stresses, strains, and deformations.

17. A computer system including at least one processor and memory for analyzing a medical device comprising:

a geometry generator that receives three-dimensional volumetric data of at least one anatomical feature of a vascular system of a particular individual and generates a geometric model of said anatomical feature(s);

a mesh generator that receives said geometric model of said anatomical feature(s) and a geometric model of a medical device, and generates a finite element model representing both said geometric model of said anatomical feature(s) and said geometric model of said medical device; and

a stress/strain/deformation analyzer that receives said finite element model, material properties of said anatomical feature(s) and said medical device, load data on said anatomical feature(s) and/or said medical device and simulates an interaction between said anatomical feature(s) and said medical device over at least one dynamic expansion and contraction cycle of the anatomical feature(s) to determine the predicted stresses, strains, and deformation of said medical device due to the interaction of the medical device with the anatomical feature.

18. The system of claim 17 wherein said geometric model of said anatomical feature(s) is an idealized geometric model.

19. The system of claim 17 wherein said three dimensional volumetric data are acquired via CT scan.

20. The system of claim 17 wherein said three dimensional volumetric data are acquired via MRI.

21. The system of claim 17 wherein said medical device is an endovascular prosthesis.

22. The system of claim 21 wherein said endovascular prosthesis is a stent graft.

23. The system of claim 21 wherein said endovascular prosthesis is a cardiovascular stent.

24. The system of claim 17 wherein said geometry generator is a software application which generates surface points from the three-dimensional volumetric data, which are then converted into stereolithography, slice files, IGES files or a combination thereof.

25. The system of claim 17 wherein said mesh generator includes three-dimensional finite modeling software.

26. The system of claim 25 wherein said three dimensional finite modeling software tessellates a geometric model into hexahedron brick elements and quadrilateral shell elements to create the model.

27. The system of claim 17 wherein said stress/strain/deformation analyzer is a non-linear finite element modeling software application.

28. The system of claim 27 wherein said non-linear finite element modeling software application is configured to accommodate a strain energy density of the form:

W=a₁₀(I₁−

3)+a₀₁(I₂−

3)+a₂₀(I₁−

3)²+a₁₁(I₁−

3)(I₂−

3)+a₀₂(I₂−

3)²+a₃₀(I₁−

3)+a₂₁(I₁−

3)²(I₂−

3)+a₁₂(I₁−

3)(I₂−

3)²+a₀₃(I₂−

3)³+½

K(I₃−

1)²

with K=2(a₁₀+a₀₁)/(1−

2v) where

a_ij are material parameters;

v is Poisson'"'"'s ratio;

K is the bulk modulus given as a function of Poisson'"'"'s ratio; and

I₁, I₂, and I₃ are the first, second, and third invariants of the right Cauchy-Green strain tensor, respectively.

29. The system of claim 17 further comprising a visualization tool that receives said simulated stresses, strains, and deformations of said medical device from said stress/strain/deformation analyzer and displays one or more of said stresses, strains, and deformations of said medical device via visual representation.

30. The system of claim 29 wherein said visualization tool includes interactive software for visualizing finite element analysis results of three-dimensional grids.

31. The system of claim 17 wherein said stress/strain/deformation analyzer uses a non-linear finite element analysis tool to simulate stresses, strains, and deformations of said medical device.

32. The system of claim 17 wherein said simulated stresses, strains, and deformations imposed on said medical device comprise dynamic or quasi-static stresses, strains, and deformations.

33. A computer system including at least one processor and memory for analyzing a medical device comprising:

a mesh generator that receives a geometric model of an in vitro anatomical feature of a vascular system and a geometric model of a medical device, and generates a finite element model representing both said geometric model of said in vitro anatomical feature and said geometric model of said medical device; and

;

a stress/strain/deformation analyzer that receives said finite element model, material properties of said in vitro anatomical feature and said medical device, load data on said in vitro anatomical feature and/or said medical device and simulates an interaction between said in vitro anatomical feature and said medical device over at least one dynamic expansion and contraction cycle of the anatomical feature(s) to determine the predicted stresses, strains, and deformations of said medical device due to the interaction of the medical device with the anatomical feature.

34. The system of claim 33 wherein said in vitro anatomical feature is idealized.

35. The system of claim 33 wherein said medical device is an endovascular prosthesis.

36. The system of claim 35 wherein said endovascular prosthesis is a stent graft.

37. The system of claim 35 wherein said endovascular prosthesis is a cardiovascular stent.

38. The system of claim 33 wherein said mesh generator includes three-dimensional finite modeling software.

39. The system of claim 38 wherein said three dimensional finite modeling software tessellates a geometric model into hexahedron brick elements and quadrilateral shell elements to create the model.

40. The system of claim 33 wherein said stress/strain/deformation analyzer is a non-linear finite element modeling software application.

41. The system of claim 40 wherein said non-linear finite element modeling software application is configured to accommodate a strain energy density of the form:

W=a₁₀(I₁−

3)+a₀₁(I₂−

3)+a₂₀(I₁−

3)²+a₁₁(I₁−

3)(I₂−

3)+a₀₂(I₂−

3)²+a₃₀(I₁−

3)+a₂₁(I₁−

3)²(I₂−

3)+a₁₂(I₁−

3)(I₂−

3)²+a₀₃(I₂−

3)³+½

K(I₃−

1)²

with K=2(a₁₀+a₀₁)/(1−

2v) where

a_ij are material parameters;

v is Poisson'"'"'s ratio;

K is the bulk modulus given as a function of Poisson'"'"'s ratio; and

I₁, I₂, and I₃ are the first, second, and third invariants of the right Cauchy-Green strain tensor, respectively.

42. The system of claim 33 further comprising a visualization tool that receives said simulated stresses, strains, and deformations of, said medical device from said stress/strain/deformation analyzer and displays one or more of said stresses, strains, and deformations of said medical device via visual representation.

43. The system of claim 42 wherein said visualization tool includes interactive software for visualizing finite element analysis results of three-dimensional grids.

44. The system of claim 33 wherein said stress/strain/deformation analyzer uses a non-linear finite element analysis tool to simulate stresses, strains, and deformations of said medical device.

45. The system of claim 33 wherein said simulated stresses, strains, and deformations imposed on said medical device comprise dynamic or quasi-static stresses, strains, and deformations.

46. A computer implemented method for analyzing a medical device comprising:

acquiring three-dimensional volumetric data of at least one anatomical feature of a vascular system;

generating a geometric model of said anatomical feature(s);

receiving data representing a geometric model of a candidate medical device design;

receiving said geometric model of said anatomical feature(s);

generating a finite element model representing both said geometric model of said anatomical feature(s) and said geometric model of said candidate medical device design with a mesh generator;

receiving material properties of said anatomical feature(s) and said candidate medical device design;

receiving load data imposed on said candidate medical device design and said anatomical feature(s); and

simulating an interaction between said anatomical feature(s) and said candidate medical device design over at least one dynamic expansion and contraction cycle of the anatomical feature(s) with a stress/strain/deformation analyzer to determine the predicted stresses, strains, and deformation of said candidate medical device design by said load data.

47. The method of claim 46 wherein the step of simulating stresses, strains, and deformations is performed to a point of failure of said candidate medical device design.

48. The method of claim 46 wherein where said three-dimensional volumetric data are acquired via CT scan.

49. The method of claim 46 wherein said three-dimensional volumetric data are acquired via MRI.

50. The method of claim 46 wherein said candidate medical device design is for an endovascular prosthesis.

51. The method of claim 50 wherein said endovascular prosthesis is a stent graft.

52. The method of claim 50 wherein said endovascular prosthesis is a cardiovascular stent.

53. The method of claim 46 wherein said geometric model for said anatomical feature(s) is generated by a software application which generates surface points from the three-dimensional volumetric data, which are then converted into stereolithography, slice files, IGES files or a combination thereof.

54. The method of claim 46 wherein said step of generating a finite element model is performed by using includes three-dimensional finite modeling software.

55. The method of claim 54 wherein said three dimensional finite modeling software tessellates a geometric model into hexahedron brick elements and quadrilateral shell elements to create the model.

56. The method of claim 46 wherein said stresses, strains, and deformations are simulated by a non-linear finite element modeling software application.

57. The method of claim 56 wherein said non-linear finite element modeling software application is configured to accommodate a strain energy density of the form:

W=a₁₀(I₁−

3)+a₀₁(I₂−

3)+a₂₀(I₁−

3)²+a₁₁(I₁−

3)(I₂−

3)+a₀₂(I₂−

3)²+a₃₀(I₁−

3)+a₂₁(I₁−

3)²(I₂−

3)+a₁₂(I₁−

3)(I₂−

3)²+a₀₃(I₂−

3)³+½

K(I₃−

1)²

with K=2(a₁₀+a₀₁)/(1−

2v) where

a_ij are material parameters;

v is Poisson'"'"'s ratio;

K is the bulk modulus given as a function of Poisson'"'"'s ratio; and

I₁, I₂, and I₃ are the first, second, and third invariants of the right Cauchy-Green strain tensor, respectively.

58. The method of claim 46 wherein said stress/strain/deformation analysis is performed using a non-linear finite element analysis tool.

59. The method of claim 46 further comprising receiving results of said stress, strain, and deformation analysis into a visualization tool and wherein said visualization tool visually presents one or more of said strains, stresses, and deformations of said medical device.

60. The method of claim 59 wherein said visualization tool includes interactive software for visualizing finite element analysis results of three-dimensional grids.

61. The method of claim 46 wherein said simulated stresses, strains, and deformations imposed on said medical device design comprise dynamic or quasi-static stresses, strains, and deformations.

62. A computer implemented method for analyzing a medical device comprising:

acquiring three-dimensional volumetric data of at least one anatomical feature of a vascular system of a particular individual with a geometry generator;

generating a geometric model of said anatomical feature(s);

receiving a geometric model of a candidate medical device with a mesh generator;

receiving said geometric model of said anatomical feature(s) with a mesh generator;

generating a finite element model representing both said geometric model of said anatomical feature(s) and said geometric model of said candidate medical device;

receiving material properties of said anatomical feature(s) and said candidate medical device;

receiving load data imposed on said anatomical feature(s) and said candidate medical device; and

simulating an interaction between said anatomical feature(s) and said candidate medical device with a stress/strain/deformation analyzer that simulates an interaction between the anatomical feature(s) and said medical device over at least one dynamic expansion and contraction cycle of the anatomical feature(s) to determine the predicted dynamic or quasi-static stresses, strains, and deformations of said candidate medical device due to the interaction of the medical device with the anatomical feature.

63. The method of claim 62 wherein the step of simulating stresses, strains, and deformations is performed to a point of failure of said candidate medical device.

64. The method of claim 62 wherein where said three-dimensional volumetric data are acquired via CT scan.

65. The method of claim 62 wherein said three-dimensional volumetric data are acquired via MRI.

66. The method of claim 62 wherein said candidate medical device is an endovascular prosthesis.

67. The method of claim 66 wherein said endovascular prosthesis is a stent graft.

68. The method of claim 66 wherein said endovascular prosthesis is a cardiovascular stent.

69. The method of claim 62 wherein said step of generating the geometric model of said anatomical feature(s) is performed by using a software application which generates surface points from the three-dimensional volumetric data, which are then converted into stereolithography, slice files, IGES files or a combination thereof.

70. The method of claim 62 wherein said step of generating said model is performed by using includes three-dimensional finite modeling software.

71. The method of claim 70 wherein said three dimensional finite modeling software tessellates a geometric model into hexahedron brick elements and quadrilateral shell elements to create the model.

72. The method of claim 62 wherein said step of simulating dynamic or quasi-static stresses/strains/deformations is performed by using a non-linear finite element modeling software application.

73. The method of claim 72 wherein said non-linear finite element modeling software application is configured to accommodate a strain energy density of the form:

W=a₁₀(I₁−

3)+a₀₁(I₂−

3)+a₂₀(I₁−

3)²+a₁₁(I₁−

3)(I₂−

3)+a₀₂(I₂−

3)²+a₃₀(I₁−

3)+a₂₁(I₁−

3)²(I₂−

3)+a₁₂(I₁−

3)(I₂−

3)²+a₀₃(I₂−

3)³+½

K(I₃−

1)²

with K=2(a₁₀+a₀₁)/(1−

2v) where

a_ij are material parameters;

v is Poisson'"'"'s ratio;

K is the bulk modulus given as a function of Poisson'"'"'s ratio; and

I₁, I₂, and I₃ are the first, second, and third invariants of the right Cauchy-Green strain tensor, respectively.

74. The method of claim 62 wherein said stress/strain/deformation analysis is performed using a non-linear finite element analysis tool.

75. The method of claim 62 further comprising receiving results of said stress, strain, and deformation analysis into a visualization tool and wherein said visualization tool visually presents one or more of said strains, stresses, and deformations of said medical device.

76. The method of claim 75 wherein said visualization tool includes interactive software for visualizing finite element analysis results of three-dimensional grids.

77. The method of claim 62 further comprising long term structural integrity testing of said medical device by recreating a plurality of dynamic expansion and contraction cycles of the vascular system.

78. The method of claim 77 wherein the plurality of dynamic expansion and contraction cycles of the vascular system comprise an amount of cycles that would meet or exceed the amount of cycles that would be expected in a lifetime of the particular individual.

79. A computer implemented method for analyzing a medical device comprising:

receiving data representing a geometric model of at least one in vitro anatomical feature of a vascular system and a geometric model of a candidate medical device design;

generating a finite element model representing both said geometric model of said in vitro anatomical feature(s) and said geometric model of said candidate medical device design with a mesh generator;

receiving material properties of said in vitro anatomical feature(s) and said candidate medical device design;

receiving load data imposed on said in vitro anatomical feature(s) and said candidate medical device design; and

simulating an interaction between said in vitro anatomical feature(s) and said candidate medical device with a stress/strain/deformation analyzer that simulates an interaction between the anatomical feature(s) and said medical device over at least one dynamic expansion and contraction cycle of the anatomical feature(s) to determine the predicted stresses, strains, and deformations of said candidate medical device design by said load data.

80. The method of claim 79 wherein the step of simulating stresses, strains, and deformations is performed to a point of failure of said candidate medical device design.

81. The method of claim 79 wherein said geometric model of said candidate medical device design is for an endovascular prosthesis.

82. The method of claim 81 wherein said endovascular prosthesis is a stent graft.

83. The method of claim 81 wherein said endovascular prosthesis is a cardiovascular stent.

84. The method of claim 79 wherein said step of generating said model is performed by using includes three-dimensional finite modeling software.

85. The method of claim 84 wherein said three dimensional finite modeling software tessellates a geometric model into hexahedron brick elements and quadrilateral shell elements to create the model.

86. The method of claim 79 wherein said step of simulating stresses, strains, and deformations is performed by using a non-linear finite element modeling software application.

87. The method of claim 86 wherein said non-linear finite element modeling software application is configured to accommodate a strain energy density of the form:

W=a₁₀(I₁−

3)+a₀₁(I₂−

3)+a₂₀(I₁−

3)²+a₁₁(I₁−

3)(I₂−

3)+a₀₂(I₂−

3)²+a₃₀(I₁−

3)+a₂₁(I₁−

3)²(I₂−

3)+a₁₂(I₁−

3)(I₂−

3)²+a₀₃(I₂−

3)³+½

K(I₃−

1)²

with K=2(a₁₀+a₀₁)/(1−

2v) where

a_ij are material parameters;

v is Poisson'"'"'s ratio;

K is the bulk modulus given as a function of Poisson'"'"'s ratio; and

I₁, I₂, and I₃ are the first, second, and third invariants of the right Cauchy-Green strain tensor, respectively.

88. The method of claim 79 wherein said stress/strain/deformation analysis is performed using a non-linear finite element analysis tool.

89. The method of claim 79 further comprising the step of receiving results of said stress, strain, and deformation analysis into a visualization tool and wherein said visualization tool visually presents one or more of said strains, stresses, and deformations of said candidate medical device design.

90. The method of claim 89 wherein said visualization tool includes interactive software for visualizing finite element analysis results of three-dimensional grids.

91. The method of claim 79 wherein said simulated stresses, strains, and deformations imposed on said candidate medical device design comprise dynamic or quasi-static stresses, strains, and deformations.

92. The method of claim 79 further comprising receiving data representing a geometric model for use in an in vitro failure mode test.

93. The method of claim 92 wherein said step of simulating comprises simulating stresses, strains, and deformations imposed on said candidate medical device design by said load data in said in vitro failure mode test.

94. The method of claim 92 further comprising varying one or more in vitro failure mode test parameters based on an additional step of comparing:

simulation data generated by said step of simulating stresses, strains, and deformations imposed on said candidate medical device design by said load data representing said anatomical feature; and

additional simulation data generated by said step of simulating stresses, strains, and deformations imposed on said candidate medical device design by said load data in said in vitro failure mode test.

95. The method of claim 94 wherein said one or more in vitro failure mode test parameters further comprises test frequency.