In Situ Measurement and Modeling of Human Cadaveric Soft Tissue Mechanical Properties for Use in Real Time Surgical Simulation

2008 ◽  
Author(s):  
Yi-Je Lim ◽  
Dhannanjay Deo ◽  
Suvranu De
Keyword(s):  
Mechanical Properties ◽  
Real Time ◽  
Soft Tissues ◽  
Force Feedback ◽  
Mechanical Response ◽  
Surgical Simulation ◽  
Physical Models ◽  
Nonlinear Viscoelastic ◽  
External Forces ◽  
Surgery Simulator

Development of a realistic surgery simulator that delivers high fidelity visual and haptic (force) feedback, based on the physical models of soft tissues, requires the use of empirical data on the mechanical behavior of intra-abdominal organs under the action of external forces. Measurement of mechanical properties of soft tissues on live human patients presents significant risks, making the use of cadavers a logical alternative. In this paper we present techniques of measuring and modeling the mechanical response of human cadaveric tissue for the purpose of developing a “virtual cadaver” model. The major contribution of this paper is the development of physics-based models of soft tissues that range from linear elastic models to nonlinear viscoelastic models which are efficient for application within the framework of a real time surgery simulator.

scholarly journals Real-Time Numerical Simulation for Accurate Soft Tissues Modeling during Haptic Interaction

Actuators ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 17
Author(s):  
Paolo Tripicchio ◽  
Salvatore D’Avella ◽  
Emanuele Ruffaldi
Keyword(s):  
Mechanical Properties ◽  
Real Time ◽  
Soft Tissues ◽  
Small Deformation ◽  
Physical Models ◽  
Frame Rate ◽  
Haptic Interaction ◽  
Simulation Accuracy ◽  
Fabric Hand ◽  
Time Interaction

The simulation of fabrics physics and its interaction with the human body has been largely studied in recent years to provide realistic-looking garments and wears specifically in the entertainment business. When the purpose of the simulation is to obtain scientific measures and detailed mechanical properties of the interaction, the underlying physical models should be enhanced to obtain better simulation accuracy increasing the modeling complexity and relaxing the simulation timing constraints to properly solve the set of equations under analysis. However, in the specific field of haptic interaction, the desiderata are to have both physical consistency and high frame rate to display stable and coherent stimuli as feedback to the user requiring a tradeoff between accuracy and real-time interaction. This work introduces a haptic system for the evaluation of the fabric hand of specific garments either existing or yet to be produced in a virtual reality simulation. The modeling is based on the co-rotational Finite Element approach that allows for large displacements but the small deformation of the elements. The proposed system can be beneficial for the fabrics industry both in the design phase or in the presentation phase, where a virtual fabric portfolio can be shown to customers around the world. Results exhibit the feasibility of high-frequency real-time simulation for haptic interaction with virtual garments employing realistic mechanical properties of the fabric materials.

Nonlinear Dynamic Viscoelastic Model for Osteoarthritic Cartilage Indentation Force

2011 ◽  
Author(s):  
A. Vidal-Lesso ◽  
E. Ledesma-Orozco ◽  
R. Lesso-Arroyo ◽  
L. Daza-Benitez
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Indentation Test ◽  
Maxwell Model ◽  
Relaxation Curve ◽  
Geometrical Parameters ◽  
Osteoarthritic Cartilage

Biomechanical properties and dynamic response of soft tissues as articular cartilage remains issues for attention. Currently, linear isotropic models are still used for cartilage analysis in spite of its viscoelastic nature. Therefore, the aim of this study was to propose a nonlinear viscoelastic model for cartilage indentation that combines the geometrical parameters and velocity of the indentation test with the thickness of the sample as well as the mechanical properties of the tissue changing over time due to its viscoelastic behavior. Parameters of the indentation test and mechanical properties as a function of time were performed in Laplace space where the constitutive equation for viscoelasticity and the convolution theorem was applied in addition with the Maxwell model and Hayes et al. model for instantaneous elastic modulus. Results of the models were compared with experimental data of indentation tests on osteoarthritic cartilage of a unicompartmental osteoarthritis cases. The models showed a strong fit for the axial indentation nonlinear force in the loading curve (R2 = 0.992) and a good fit for unloading (R2 = 0.987), while an acceptable fit was observed in the relaxation curve (R2 = 0.967). These models may be used to study the mechanical response of osteoarthritic cartilage to several dynamical and geometrical test conditions.

Real-Time FEM of Soft Tissues for Virtual Surgery

2009 ◽  
Author(s):  
Christian Willberg ◽  
Harald Berger ◽  
Ulrich Gabbert
Keyword(s):  
Real Time ◽  
Soft Tissues ◽  
Force Feedback ◽  
Surgical Instruments ◽  
Virtual Surgery ◽  
Continuous Training ◽  
Endoscopic Techniques ◽  
Organ Models ◽  
Small Perforation ◽  
High Level

Endoscopic techniques require small perforation holes only as entries for optical and surgical instruments; such enabling the treatment of injuries with a minimized damage of the surrounding health tissue. But the surgeon has to operate in a 3D domain by looking at a distorted 2D image at the screen. It is well known, that a good surgeon needs a continuous training to perform such operations reliable in a top quality. To overcome the high costs and tight ethical restrictions of animal based education and training has result in an increasing development and application of virtual surgery simulators [1]. One of the main issues of surgery simulators is to ensure simultaneously the real time performance of the device, the high-level image representation and an acceptable force-feedback behavior. The basics of such simulators are mathematical models of the involved soft tissues, which have to perform in a realistic physical manner, with dynamic nonlinear large deformations, including the interaction of the different constituents (instrument/organ, organ/organ, organ by itself, cutting, bleeding etc). In the paper the focus is on realistic organ models and the realization of a fast contact search and reaction algorithm.

scholarly journals Soft-Tissue-Mimicking Using Hydrogels for the Development of Phantoms

Gels ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 40
Author(s):  
Aitor Tejo-Otero ◽  
Felip Fenollosa-Artés ◽  
Isabel Achaerandio ◽  
Sergi Rey-Vinolas ◽  
Irene Buj-Corral ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Viscoelastic Behavior ◽  
Linear Elastic ◽  
Lack Of Information ◽  
Wide Range ◽  
Significant Difference ◽  
Promising Solution ◽  
Living Tissues

With the currently available materials and technologies it is difficult to mimic the mechanical properties of soft living tissues. Additionally, another significant problem is the lack of information about the mechanical properties of these tissues. Alternatively, the use of phantoms offers a promising solution to simulate biological bodies. For this reason, to advance in the state-of-the-art a wide range of organs (e.g., liver, heart, kidney as well as brain) and hydrogels (e.g., agarose, polyvinyl alcohol –PVA–, Phytagel –PHY– and methacrylate gelatine –GelMA–) were tested regarding their mechanical properties. For that, viscoelastic behavior, hardness, as well as a non-linear elastic mechanical response were measured. It was seen that there was a significant difference among the results for the different mentioned soft tissues. Some of them appear to be more elastic than viscous as well as being softer or harder. With all this information in mind, a correlation between the mechanical properties of the organs and the different materials was performed. The next conclusions were drawn: (1) to mimic the liver, the best material is 1% wt agarose; (2) to mimic the heart, the best material is 2% wt agarose; (3) to mimic the kidney, the best material is 4% wt GelMA; and (4) to mimic the brain, the best materials are 4% wt GelMA and 1% wt agarose. Neither PVA nor PHY was selected to mimic any of the studied tissues.

Real-Time Finite Element Modelling With Haptic Support

1999 ◽  
Author(s):  
Jeffrey Berkley ◽  
Mark Ganter ◽  
Suzanne Weghorst ◽  
Hayes Gladstone ◽  
Gregory Raugi ◽  
...  
Keyword(s):  
Finite Element ◽  
Real Time ◽  
Force Feedback ◽  
Design Tool ◽  
Element Analysis ◽  
Human Interface ◽  
Element System ◽  
Skin Surgery ◽  
Surgery Simulator ◽  
The University

Abstract This paper presents the preliminary results of a new real-time finite element system which supports haptic (i.e. force) feedback to the user. The methodology of the system is based on linear finite-element analysis. Further, this system was originally developed as part of a real-time skin surgery simulator with the Human Interface Technology Lab and, the Division of Dermatology at the University of Washington Medical School. We are currently exploring its use and development as a new engineering design tool.

Finite Element Based Nonlinear Normalization of Human Lumbar Intervertebral Disc Stiffness to Account for Its Morphology

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Ghislain Maquer ◽  
Marc Laurent ◽  
Vaclav Brandejsky ◽  
Michael L. Pretterklieber ◽  
Philippe K. Zysset
Keyword(s):  
Mechanical Properties ◽  
Intervertebral Disc ◽  
Material Properties ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Parameter Study ◽  
Nonlinear Normalization ◽  
Highly Nonlinear ◽  
Flexion Extension ◽  
Linear And Nonlinear

Disc degeneration, usually associated with low back pain and changes of intervertebral stiffness, represents a major health issue. As the intervertebral disc (IVD) morphology influences its stiffness, the link between mechanical properties and degenerative grade is partially lost without an efficient normalization of the stiffness with respect to the morphology. Moreover, although the behavior of soft tissues is highly nonlinear, only linear normalization protocols have been defined so far for the disc stiffness. Thus, the aim of this work is to propose a nonlinear normalization based on finite elements (FE) simulations and evaluate its impact on the stiffness of human anatomical specimens of lumbar IVD. First, a parameter study involving simulations of biomechanical tests (compression, flexion/extension, bilateral torsion and bending) on 20 FE models of IVDs with various dimensions was carried out to evaluate the effect of the disc's geometry on its compliance and establish stiffness/morphology relations necessary to the nonlinear normalization. The computed stiffness was then normalized by height (H), cross-sectional area (CSA), polar moment of inertia (J) or moments of inertia (Ixx, Iyy) to quantify the effect of both linear and nonlinear normalizations. In the second part of the study, T1-weighted MRI images were acquired to determine H, CSA, J, Ixx and Iyy of 14 human lumbar IVDs. Based on the measured morphology and pre-established relation with stiffness, linear and nonlinear normalization routines were then applied to the compliance of the specimens for each quasi-static biomechanical test. The variability of the stiffness prior to and after normalization was assessed via coefficient of variation (CV). The FE study confirmed that larger and thinner IVDs were stiffer while the normalization strongly attenuated the effect of the disc geometry on its stiffness. Yet, notwithstanding the results of the FE study, the experimental stiffness showed consistently higher CV after normalization. Assuming that geometry and material properties affect the mechanical response, they can also compensate for one another. Therefore, the larger CV after normalization can be interpreted as a strong variability of the material properties, previously hidden by the geometry's own influence. In conclusion, a new normalization protocol for the intervertebral disc stiffness in compression, flexion, extension, bilateral torsion and bending was proposed, with the possible use of MRI and FE to acquire the discs' anatomy and determine the nonlinear relations between stiffness and morphology. Such protocol may be useful to relate the disc's mechanical properties to its degree of degeneration.

scholarly journals A Systematic Review of Real-Time Medical Simulations with Soft-Tissue Deformation: Computational Approaches, Interaction Devices, System Architectures, and Clinical Validations

2020 ◽  
Vol 2020 ◽  
pp. 1-30 ◽  
Author(s):  
Tan-Nhu Nguyen ◽  
Marie-Christine Ho Ba Tho ◽  
Tien-Tuan Dao
Keyword(s):  
Systematic Review ◽  
Soft Tissue ◽  
Real Time ◽  
Review Process ◽  
Soft Tissues ◽  
Force Feedback ◽  
Surgical Instruments ◽  
Assessment Procedure ◽  
System Architectures ◽  
Computational Approaches

Simulating deformations of soft tissues is a complex engineering task, and it is even more difficult when facing the constraint between computation speed and system accuracy. However, literature lacks of a holistic review of all necessary aspects (computational approaches, interaction devices, system architectures, and clinical validations) for developing an effective system of soft-tissue simulations. This paper summarizes and analyses recent achievements of resolving these issues to estimate general trends and weakness for future developments. A systematic review process was conducted using the PRISMA protocol with three reliable scientific search engines (ScienceDirect, PubMed, and IEEE). Fifty-five relevant papers were finally selected and included into the review process, and a quality assessment procedure was also performed on them. The computational approaches were categorized into mesh, meshfree, and hybrid approaches. The interaction devices concerned about combination between virtual surgical instruments and force-feedback devices, 3D scanners, biomechanical sensors, human interface devices, 3D viewers, and 2D/3D optical cameras. System architectures were analysed based on the concepts of system execution schemes and system frameworks. In particular, system execution schemes included distribution-based, multithread-based, and multimodel-based executions. System frameworks are grouped into the input and output interaction frameworks, the graphic interaction frameworks, the modelling frameworks, and the hybrid frameworks. Clinical validation procedures are ordered as three levels: geometrical validation, model behavior validation, and user acceptability/safety validation. The present review paper provides useful information to characterize how real-time medical simulation systems with soft-tissue deformations have been developed. By clearly analysing advantages and drawbacks in each system development aspect, this review can be used as a reference guideline for developing systems of soft-tissue simulations.

Discrete Deformation Models for Real-Time Computation of Compliant Mechanisms

2013 ◽  
Author(s):  
Jingjing Ji ◽  
Kok-Meng Lee
Keyword(s):  
Real Time ◽  
Force Feedback ◽  
Compliant Mechanisms ◽  
Simulated Data ◽  
Operating Conditions ◽  
Practical Implementation ◽  
Computation Method ◽  
Beam Model ◽  
Path Lengths ◽  
External Forces

This paper presents the formulation of a reduced-order linear discrete–path approximation in state space and its solution as a function of path lengths for a 3D curvature-based beam model (CBM). Solutions to both forward and inverse problems are discussed; the former is essential for real-time deformed shape visualization whereas the latter is much needed for haptic force feedback. The method is illustrated with an application example where a 2D beam is characterized by a 6th order CBM. Practical implementation shows that when external forces as system input are expressed in global coordinates, the CBM can be decoupled into two 2nd order systems enabling parallel computing of the deformed shape and the orientation and moment, and effectively reducing the table size for storing the operating conditions. The proposed real-time computation method has been validated by verifying results against published experimental and MSM simulated data.

Constitutive Formulation of the Mechanical Properties of Synthetic Hydrogels

2004 ◽  
Author(s):  
Alexander Rachev ◽  
Tarek ElShazly ◽  
David N. Ku
Keyword(s):  
Mechanical Properties ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Uniaxial Extension ◽  
Strain Energy Density Function ◽  
Strain Invariant ◽  
Synthetic Hydrogels ◽  
Constitutive Formulation

This study attempts to define a universal description of the constitutive formulation of mechanical properties of synthetic hydrogels that can be manufactured as load-bearing structures to replace diseased or damaged soft tissues. While the strain energy density function (SEF) describing the elastic properties of a soft tissue generally depends on two invariants, we propose a SEF that depends on only the first strain invariant. This allows quantifying the SEF from data of a uniaxial extension test. The single invariant SEF was used to predict the mechanical response of a thick-walled tube inflated by an internal pressure. The results show excellent concordance with recorded experimental data, indicating that the mechanical properties of elastic hydrogels can be accurately represented by a SEF that is an exponential function of the first strain invariant with two material constants.

scholarly journals Modeling of Tool-Tissue Interactions for Computer-Based Surgical Simulation: A Literature Review

2008 ◽  
Vol 17 (5) ◽  
pp. 463-491 ◽  
Author(s):  
Sarthak Misra ◽  
K. T. Ramesh ◽  
Allison M. Okamura
Keyword(s):  
Real Time ◽  
Force Feedback ◽  
Surgical Simulation ◽  
Surgical Instruments ◽  
Future Research ◽  
Surgical Simulators ◽  
Organ Deformation ◽  
Tissue Interactions ◽  
Operative Planning

Surgical simulators present a safe and potentially effective method for surgical training, and can also be used in robot-assisted surgery for pre- and intra-operative planning. Accurate modeling of the interaction between surgical instruments and organs has been recognized as a key requirement in the development of high-fidelity surgical simulators. Researchers have attempted to model tool-tissue interactions in a wide variety of ways, which can be broadly classified as (1) linear elasticity-based, (2) nonlinear (hyperelastic) elasticity-based finite element (FE) methods, and (3) other techniques not based on FE methods or continuum mechanics. Realistic modeling of organ deformation requires populating the model with real tissue data (which are difficult to acquire in vivo) and simulating organ response in real time (which is computationally expensive). Further, it is challenging to account for connective tissue supporting the organ, friction, and topological changes resulting from tool-tissue interactions during invasive surgical procedures. Overcoming such obstacles will not only help us to model tool-tissue interactions in real time, but also enable realistic force feedback to the user during surgical simulation. This review paper classifies the existing research on tool-tissue interactions for surgical simulators specifically based on the modeling techniques employed and the kind of surgical operation being simulated, in order to inform and motivate future research on improved tool-tissue interaction models.

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