LEMwas that it removed the influence of the nonuniform thickness of the samples to the quantitative measure of the deformation resistance of the tissue. The results from these studies will
serve as building blocks to develop a computationally efficient
finite element model for surgery simulation. It is envisioned that
this model can realistically reproduce the cutting forces characteristics through a haptic (sense of touch) feedback device.
In the literature, most modeling efforts are focused towards
assuming the mechanical properties and developing methods to
efficiently solve the tissue simulation problemfor robot-assisted
surgery/training [3], [4]. Some of the models in the literature
use the spring mass model [5] or hybrid elastic model [3] which
require low computation time, while trading off its complexities
and realism.
Properties of soft tissue has been extensively researched in
compression or tension experiments [6], [7]. Specifically for
porcine liver tissue, the Poisson’s ratio was determined based
on combined compression and elongation experiments [8]. Constitutive models were established for soft tissue or abdominal organ based on experimental data [9]–[11]. However, there has
been very little work on modeling the cutting process based
on observed experimental data [12]. Scissor cutting of animal
tissue has been explored and preliminary models to study the
process have been developed [13]–[15]. With regard to fracture
characteristics in cutting of soft tissue,Mai and Atkins [16] performed guillotine cutting to studymechanics during cuttingwith blade. Mahvash and Hayward [17], [18] analyzed the cutting
of deformable solids for haptics rendering. They were the first
to propose a computational model of cutting using an energy
approach of fracture mechanics in the framework of a deformation/rupture/cutting three-mode
tool-sample interaction hypothesis. A collaborating colleague conducted experiments of
cutting samples of potato (triangular and rectangular prisms)
and calf liver (rectangular prism) using a razor blade clamped to
a robotic manipulator to perform cutting in a direction orthogonal to the axes of the prisms
with a cutting speed of 1 mm/s. It was concluded that themeasurements supported the three-mode
tool-sample interaction hypothesis [17].While reasonably accurate methods for ex vivo studies have been developed, there is much required research in modeling soft-tissue cutting through
in vivo studies. With regard to computational simulation of surgery, the
key concern is to reduce the computational intensiveness of
the model while retaining model fidelity. Various methods
had been explored to reduce the order (size) of the models
while retaining fidelity. Finite element method (FEM) [19]
had been used in soft tissue simulation. Bro-Nilsen and Cotin
et al. [3], [20] used 3-D volumetric finite element model for
surgery simulation. To render the 3-D continuum FE model
of tetrahedral elements capable for real time simulation, they
reduced the order of the model by statically condensing out
the internal degree of freedom (dof) while keeping only the
degrees of freedom associated with surface nodes. James and
Pai [21] used boundary integral formulation and discretized the
geometry with boundary element method (BEM) in real-time
simulation of the deformation of linear elastic objects. For
linear elastic deformation, the solution can be attained by the
superposition of predetermined response of unit loading and
implemented with a low order updating algorithm. Zhuang
and Canny [22] proposed finite element models to speed up
LEMwas that it removed the influence of the nonuniform thickness of the samples to the quantitative measure of the deformation resistance of the tissue. The results from these studies will
serve as building blocks to develop a computationally efficient
finite element model for surgery simulation. It is envisioned that
this model can realistically reproduce the cutting forces characteristics through a haptic (sense of touch) feedback device.
In the literature, most modeling efforts are focused towards
assuming the mechanical properties and developing methods to
efficiently solve the tissue simulation problemfor robot-assisted
surgery/training [3], [4]. Some of the models in the literature
use the spring mass model [5] or hybrid elastic model [3] which
require low computation time, while trading off its complexities
and realism.
Properties of soft tissue has been extensively researched in
compression or tension experiments [6], [7]. Specifically for
porcine liver tissue, the Poisson’s ratio was determined based
on combined compression and elongation experiments [8]. Constitutive models were established for soft tissue or abdominal organ based on experimental data [9]–[11]. However, there has
been very little work on modeling the cutting process based
on observed experimental data [12]. Scissor cutting of animal
tissue has been explored and preliminary models to study the
process have been developed [13]–[15]. With regard to fracture
characteristics in cutting of soft tissue,Mai and Atkins [16] performed guillotine cutting to studymechanics during cuttingwith blade. Mahvash and Hayward [17], [18] analyzed the cutting
of deformable solids for haptics rendering. They were the first
to propose a computational model of cutting using an energy
approach of fracture mechanics in the framework of a deformation/rupture/cutting three-mode
tool-sample interaction hypothesis. A collaborating colleague conducted experiments of
cutting samples of potato (triangular and rectangular prisms)
and calf liver (rectangular prism) using a razor blade clamped to
a robotic manipulator to perform cutting in a direction orthogonal to the axes of the prisms
with a cutting speed of 1 mm/s. It was concluded that themeasurements supported the three-mode
tool-sample interaction hypothesis [17].While reasonably accurate methods for ex vivo studies have been developed, there is much required research in modeling soft-tissue cutting through
in vivo studies. With regard to computational simulation of surgery, the
key concern is to reduce the computational intensiveness of
the model while retaining model fidelity. Various methods
had been explored to reduce the order (size) of the models
while retaining fidelity. Finite element method (FEM) [19]
had been used in soft tissue simulation. Bro-Nilsen and Cotin
et al. [3], [20] used 3-D volumetric finite element model for
surgery simulation. To render the 3-D continuum FE model
of tetrahedral elements capable for real time simulation, they
reduced the order of the model by statically condensing out
the internal degree of freedom (dof) while keeping only the
degrees of freedom associated with surface nodes. James and
Pai [21] used boundary integral formulation and discretized the
geometry with boundary element method (BEM) in real-time
simulation of the deformation of linear elastic objects. For
linear elastic deformation, the solution can be attained by the
superposition of predetermined response of unit loading and
implemented with a low order updating algorithm. Zhuang
and Canny [22] proposed finite element models to speed up
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