1,177 research outputs found
Real-time Error Control for Surgical Simulation
Objective: To present the first real-time a posteriori error-driven adaptive
finite element approach for real-time simulation and to demonstrate the method
on a needle insertion problem. Methods: We use corotational elasticity and a
frictional needle/tissue interaction model. The problem is solved using finite
elements within SOFA. The refinement strategy relies upon a hexahedron-based
finite element method, combined with a posteriori error estimation driven local
-refinement, for simulating soft tissue deformation. Results: We control the
local and global error level in the mechanical fields (e.g. displacement or
stresses) during the simulation. We show the convergence of the algorithm on
academic examples, and demonstrate its practical usability on a percutaneous
procedure involving needle insertion in a liver. For the latter case, we
compare the force displacement curves obtained from the proposed adaptive
algorithm with that obtained from a uniform refinement approach. Conclusions:
Error control guarantees that a tolerable error level is not exceeded during
the simulations. Local mesh refinement accelerates simulations. Significance:
Our work provides a first step to discriminate between discretization error and
modeling error by providing a robust quantification of discretization error
during simulations.Comment: 12 pages, 16 figures, change of the title, submitted to IEEE TBM
Progressive tearing and cutting of soft-bodies in high-performance virtual reality
We present an algorithm that allows a user within a virtual environment to
perform real-time unconstrained cuts or consecutive tears, i.e., progressive,
continuous fractures on a deformable rigged and soft-body mesh model in
high-performance 10ms. In order to recreate realistic results for different
physically-principled materials such as sponges, hard or soft tissues, we
incorporate a novel soft-body deformation, via a particle system layered on-top
of a linear-blend skinning model. Our framework allows the simulation of
realistic, surgical-grade cuts and continuous tears, especially valuable in the
context of medical VR training. In order to achieve high performance in VR, our
algorithms are based on Euclidean geometric predicates on the rigged mesh,
without requiring any specific model pre-processing. The contribution of this
work lies on the fact that current frameworks supporting similar kinds of model
tearing, either do not operate in high-performance real-time or only apply to
predefined tears. The framework presented allows the user to freely cut or tear
a 3D mesh model in a consecutive way, under 10ms, while preserving its
soft-body behaviour and/or allowing further animation.Comment: 9 pages, 11 figures, 3 tables, submitted to "International Conference
on Artificial Reality and Telexistence, Eurographics Symposium on Virtual
Environments 2022
Adaptive Resolution for Topology Modifications in Physically-based Animation
This paper shows the interest of basing a mechanical mesh upon an efficient topological model in order to give any simulation the ability to refine this mesh locally and apply topological modifications such as cutting, tear and matter destruction.Refinement and modifications can indeed be combined in order to get a more precise result.The powerful combinatorial map model provides the mathematical background which ensures that the quasi-manifold property is guaranteed for the mesh after any topological modification.The obtained results offer the versatility and time efficiency that are expected in applications such as surgical simulation
Planning Framework for Robotic Pizza Dough Stretching with a Rolling Pin
Stretching a pizza dough with a rolling pin is a nonprehensile manipulation. Since the object is deformable, force closure cannot be established, and the manipulation is carried out in a nonprehensile way. The framework of this pizza dough stretching application that is explained in this chapter consists of four sub-procedures: (i) recognition of the pizza dough on a plate, (ii) planning the necessary steps to shape the pizza dough to the desired form, (iii) path generation for a rolling pin to execute the output of the pizza dough planner, and (iv) inverse kinematics for the bi-manual robot to grasp and control the rolling pin properly. Using the deformable object model described in Chap. 3, each sub-procedure of the proposed framework is explained sequentially
Biomechanically-Regularized Deformable Image Registration for Head and Neck Adaptive Radiation Therapy
Radiation treatment (RT), one of the best treatments available for head and neck (HN) cancer, may fail to accurately target tumors and spare surrounding healthy tissue that change in shape and location during 5-7 weeks of RT. This anatomical change can be monitored by calculating deformation maps from planning computed tomography (CT) image (taken prior to the start of RT) to treatment CT images (taken at every treatment fractions for patient setup) via deformable image registration (DIR). In response to the deformations estimated by DIR, initial radiation treatment plan established on the planning CT can be adjusted to deliver sufficient radiation dose to the tumors while sparing healthy tissue.
However, since DIR is formulated as an optimization problem to find a deformation map that simply maximizes a similarity metric between two images, it may result in physically unreasonable deformations, such as bone warping. Moreover, DIR accuracy of HN soft tissue region is limited and parameter-dependent as reported in previous studies. Finally, previous studies have evaluated DIR accuracy with a limited number of landmarks, with which accuracy of volumetric deformation cannot be rigorously evaluated.
The objective of this dissertation is 1) to improve registration accuracy of HN CT images by introducing penalty terms (from biomechanical principles) into B-spline DIR, in which deformation is represented using a linear combinations of B-spline functions, and 2) to develop an improved evaluation method for DIR accuracy based on finite element model (FE) model of HN region. First, a penalty for prevent the bone warping was developed to preserve inter-voxel distances within each of rigid regions. Second, a penalty that prevents resultant deformations from violating the static equilibrium equations of linear elastic material was used for the B-spline DIR of muscle in HN region. Third, a FE HN model was developed to generate deformation maps similar to those seen in patients that can be used as ground-truth for the evaluation of registration accuracy.
The outcome of the dissertation would support research/development in RT of HN cancer by enabling the accurate estimation of deformations of healthy tissue surrounding tumor and the rigorous assessment of registration accuracy.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113532/1/jihun_1.pd
Real-time hybrid cutting with dynamic fluid visualization for virtual surgery
It is widely accepted that a reform in medical teaching must be made to meet today's high volume training requirements. Virtual simulation offers a potential method of providing such trainings and some current medical training simulations integrate haptic and visual feedback to enhance procedure learning. The purpose of this project is to explore the capability of Virtual Reality (VR) technology to develop a training simulator for surgical cutting and bleeding in a general surgery
Adaptive Physically Based Models in Computer Graphics
International audienceOne of the major challenges in physically-based modeling is making simulations efficient. Adaptive models provide an essential solution to these efficiency goals. These models are able to self-adapt in space and time, attempting to provide the best possible compromise between accuracy and speed. This survey reviews the adaptive solutions proposed so far in computer graphics. Models are classified according to the strategy they use for adaptation, from time-stepping and freezing techniques to geometric adaptivity in the form of structured grids, meshes, and particles. Applications range from fluids, through deformable bodies, to articulated solids
Real-time simulation of surgery by Proper Generalized Decomposition techniques
La simulación quirúrgica por ordenador en tiempo real se ha convertido en una alternativa muy atractiva a los simuladores quirúrgicos tradicionales. Entre otras ventajas, los simuladores por ordenador consiguen ahorros importantes de tiempo y de costes de mantenimiento, y permiten que los estudiantes practiquen sus habilidades quirúrgicas en un entorno seguro tantas veces como sea necesario. Sin embargo, a pesar de las capacidades de los ordenadores actuales, la cirugÃa computacional sigue siendo un campo de investigación exigente. Uno de sus mayores retos es la alta velocidad a la que se tienen que resolver complejos problemas de mecánica de medios continuos para que los interfaces hápticos puedan proporcionar un sentido del tacto realista (en general, se necesitan velocidades de respuesta de 500-1000 Hz).Esta tesis presenta algunos métodos numéricos novedosos para la simulación interactiva de dos procedimientos quirúrgicos habituales: el corte y el rasgado (o desgarro) de tejidos blandos. El marco común de los métodos presentados es el uso de la Descomposición Propia Generalizada (PGD en inglés) para la generación de vademécums computacionales, esto es, metasoluciones generales de problemas paramétricos de altas dimensiones que se pueden evaluar a velocidades de respuesta compatibles con entornos hápticos.En el caso del corte, los vademécums computacionales se utilizan de forma conjunta con técnicas basadas en XFEM, mientras que la carga de cálculo se distribuye entre una etapa off-line (previa a la ejecución interactiva) y otra on-line (en tiempo de ejecución). Durante la fase off-line, para el órgano en cuestión se precalculan tanto un vademécum computacional para cualquier posición de una carga, como los desplazamientos producidos por un conjunto de cortes. AsÃ, durante la etapa on-line, los resultados precalculados se combinan de la forma más adecuada para obtener en tiempo real la respuesta a las acciones dirigidas por el usuario. En cuanto al rasgado, a partir de una ecuación paramétrica basada en mecánica del daño continuo, se obtiene un vademécum computacional. La complejidad del modelo se reduce mediante técnicas de Descomposición Ortogonal Propia (POD en inglés), y el vademécum se incorpora a una formulación incremental explÃcita que se puede interpretar como una especie de integrador temporal.A modo de ejemplo, el método para el corte se aplica a la simulación de un procedimiento quirúrgico refractivo de la córnea conocido como queratotomÃa radial, mientras que el método para el rasgado se centra en la simulación de la colecistectomÃa laparoscópica (la extirpación de la vesÃcula biliar mediante laparoscopia). En ambos casos, los métodos implementados ofrecen excelentes resultados en términos de velocidades de respuesta y producen simulaciones muy realistas desde los puntos de vista visual y háptico.The real-time computer-based simulation of surgery has proven to be an appealing alternative to traditional surgical simulators. Amongst other advantages, computer-based simulators provide considerable savings on time and maintenance costs, and allow trainees to practice their surgical skills in a safe environment as often as necessary. However, in spite of the current computer capabilities, computational surgery continues to be a challenging field of research. One of its major issues is the high speed at which complex problems in continuum mechanics have to be solved so that haptic interfaces can render a realistic sense of touch (generally, feedback rates of 500–1 000 Hz are required). This thesis introduces some novel numerical methods for the interactive simulation of two usual surgical procedures: cutting and tearing of soft tissues. The common framework of the presented methods is the use of the Proper Generalised Decomposition (PGD) for the generation of computational vademecums, i. e. general meta-solutions of parametric high-dimensional problems that can be evaluated at feedback rates compatible with haptic environments. In the case of cutting, computational vademecums are used jointly with XFEM-based techniques, and the computing workload is distributed into an off-line and an on-line stage. During the off-line stage, both a computational vademecum for any position of a load and the displacements produced by a set of cuts are pre-computed for the organ under consideration. Thus, during the on-line stage, the pre-computed results are properly combined together to obtain in real-time the response to the actions driven by the user. Concerning tearing, a computational vademecum is obtained from a parametric equation based on continuum damage mechanics. The complexity of the model is reduced by Proper Orthogonal Decomposition (POD) techniques, and the vademecum is incorporated into an explicit incremental formulation that can be viewed as a sort of time integrator. By way of example, the cutting method is applied to the simulation of a corneal refractive surgical procedure known as radial keratotomy, whereas the tearing method focuses on the simulation of laparoscopic cholecystectomy (i. e. the removal of the gallbladder). In both cases, the implemented methods offer excellent performances in terms of feedback rates, and produce.<br /
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