17,728 research outputs found
A 3D discrete model of the diaphragm and human trunk
In this paper, a 3D discrete model is presented to model the movements of the
trunk during breathing. In this model, objects are represented by physical
particles on their contours. A simple notion of force generated by a linear
actuator allows the model to create forces on each particle by way of a
geometrical attractor. Tissue elasticity and contractility are modeled by local
shape memory and muscular fibers attractors. A specific dynamic MRI study was
used to build a simple trunk model comprised of by three compartments: lungs,
diaphragm and abdomen. This model was registered on the real geometry.
Simulation results were compared qualitatively as well as quantitatively to the
experimental data, in terms of volume and geometry. A good correlation was
obtained between the model and the real data. Thanks to this model, pathology
such as hemidiaphragm paralysis can also be simulated.Comment: published in: "Lung Modelling", France (2006
Using CamiTK for rapid prototyping of interactive Computer Assisted Medical Intervention applications
Computer Assisted Medical Intervention (CAMI hereafter) is a complex
multi-disciplinary field. CAMI research requires the collaboration of experts
in several fields as diverse as medicine, computer science, mathematics,
instrumentation, signal processing, mechanics, modeling, automatics, optics,
etc
NOViSE: a virtual natural orifice transluminal endoscopic surgery simulator
Purpose: Natural Orifice Transluminal Endoscopic Surgery (NOTES) is a novel technique in minimally invasive surgery whereby a flexible endoscope is inserted via a natural orifice to gain access to the abdominal cavity, leaving no external scars. This innovative use of flexible endoscopy creates many new challenges and is associated with a steep learning curve for clinicians. Methods: We developed NOViSE - the first force-feedback enabled virtual reality simulator for NOTES training supporting a flexible endoscope. The haptic device is custom built and the behaviour of the virtual flexible endoscope is based on an established theoretical framework – the Cosserat Theory of Elastic Rods. Results: We present the application of NOViSE to the simulation of a hybrid trans-gastric cholecystectomy procedure. Preliminary results of face, content and construct validation have previously shown that NOViSE delivers the required level of realism for training of endoscopic manipulation skills specific to NOTES Conclusions: VR simulation of NOTES procedures can contribute to surgical training and improve the educational experience without putting patients at risk, raising ethical issues or requiring expensive animal or cadaver facilities. In the context of an experimental technique, NOViSE could potentially facilitate NOTES development and contribute to its wider use by keeping practitioners up to date with this novel surgical technique. NOViSE is a first prototype and the initial results indicate that it provides promising foundations for further development
Constrained Soft Tissue Simulation for Virtual Surgical Simulation
yesMost of surgical simulators employ a linear elastic
model to simulate soft tissue material properties due to its computational
efficiency and the simplicity. However, soft tissues often
have elaborate nonlinearmaterial characteristics. Most prominently,
soft tissues are soft and compliant to small strains, but after
initial deformations they are very resistant to further deformations
even under large forces. Such material characteristic is referred as
the nonlinear material incompliant which is computationally expensive
and numerically difficult to simulate. This paper presents a
constraint-based finite-element algorithm to simulate the nonlinear
incompliant tissue materials efficiently for interactive simulation
applications such as virtual surgery. Firstly, the proposed algorithm
models the material stiffness behavior of soft tissues with a
set of 3-D strain limit constraints on deformation strain tensors.
By enforcing a large number of geometric constraints to achieve
the material stiffness, the algorithm reduces the task of solving
stiff equations of motion with a general numerical solver to iteratively
resolving a set of constraints with a nonlinear Gauss–Seidel
iterative process. Secondly, as a Gauss–Seidel method processes
constraints individually, in order to speed up the global convergence
of the large constrained system, a multiresolution hierarchy
structure is also used to accelerate the computation significantly,
making interactive simulations possible at a high level of details .
Finally, this paper also presents a simple-to-build data acquisition
system to validate simulation results with ex vivo tissue measurements.
An interactive virtual reality-based simulation system is
also demonstrated
Animating Human Muscle Structure
Graphical simulations of human muscle motion and deformation are of great interest to
medical education. In this article, the authors present a technique for simulating muscle
deformations by combining physically and geometrically based computations to reduce
computation cost and produce fast, accurate simulations
Phenomenological model of diffuse global and regional atrophy using finite-element methods
The main goal of this work is the generation of ground-truth data for the validation of atrophy measurement techniques, commonly used in the study of neurodegenerative diseases such as dementia. Several techniques have been used to measure atrophy in cross-sectional and longitudinal studies, but it is extremely difficult to compare their performance since they have been applied to different patient populations. Furthermore, assessment of performance based on phantom measurements or simple scaled images overestimates these techniques' ability to capture the complexity of neurodegeneration of the human brain. We propose a method for atrophy simulation in structural magnetic resonance (MR) images based on finite-element methods. The method produces cohorts of brain images with known change that is physically and clinically plausible, providing data for objective evaluation of atrophy measurement techniques. Atrophy is simulated in different tissue compartments or in different neuroanatomical structures with a phenomenological model. This model of diffuse global and regional atrophy is based on volumetric measurements such as the brain or the hippocampus, from patients with known disease and guided by clinical knowledge of the relative pathological involvement of regions and tissues. The consequent biomechanical readjustment of structures is modelled using conventional physics-based techniques based on biomechanical tissue properties and simulating plausible tissue deformations with finite-element methods. A thermoelastic model of tissue deformation is employed, controlling the rate of progression of atrophy by means of a set of thermal coefficients, each one corresponding to a different type of tissue. Tissue characterization is performed by means of the meshing of a labelled brain atlas, creating a reference volumetric mesh that will be introduced to a finite-element solver to create the simulated deformations. Preliminary work on the simulation of acquisition artefa- - cts is also presented. Cross-sectional and
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