There are a large number of materials with mild stiffness, which are not as soft as tissues and not as strong as metals. These semihard materials include energetic materials, molecular crystals, layered materials, and van der Waals... more
There are a large number of materials with mild stiffness, which are not as soft as tissues and not as strong as metals. These semihard materials include energetic materials, molecular crystals, layered materials, and van der Waals crystals. The integrity and mechanical stability are mainly determined by the interactions between instantaneously induced dipoles, the so called London dispersion force or van der Waals force. It is challenging to accurately model the structural and mechanical properties of these semihard materials in the frame of density functional theory where the non-local correlation functionals are not well known. Here, we propose a van der Waals density functional named vdW-DFq to accurately model the density and geometry of semihard materials. Using β-cyclotetramethylene tetranitramine as a prototype, we adjust the enhancement factor of the exchange energy functional with generalized gradient approximations. We find this method to be simple and robust over a wide tuning range when calibrating the functional on-demand with experimental data. With a calibrated value q = 1.05, the proposed vdW-DFq method shows good performance in predicting the geometries of 11 common energetic material molecular crystals and three typical layered van der Waals crystals. This success could be attributed to the similar electronic charge density gradients, suggesting a wide use in modeling semihard materials. This method could be useful in developing non-empirical density functional theories for semihard and soft materials.
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Natural orifice translumenal endoscopic surgery (NOTES) is a minimally invasive procedure, which utilizes the body's natural orifices to gain access to the peritoneal cavity. The VTEST(©) is a virtual reality NOTES simulator developed... more
Natural orifice translumenal endoscopic surgery (NOTES) is a minimally invasive procedure, which utilizes the body's natural orifices to gain access to the peritoneal cavity. The VTEST(©) is a virtual reality NOTES simulator developed at the CeMSIM at RPI to train surgeons in NOTES. A novel 2 DOF decoupled haptic device was designed and built for this simulator. The haptic device can render 5.62 N and 190.05 N-mm of continuous force and torque respectively. In this work we have evaluated the haptic interface and developed a model to accurately describe the system behavior, to further incorporate into an impedance type controller for realistic haptic rendering in the VTEST(©).
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We investigate the equation of states of the $\beta$-polymorph of cyclotetramethylene tetranitramine (HMX) energetic molecular crystal using DFT-D2, a first-principles calculation based on density functional theory (DFT) with van der... more
We investigate the equation of states of the $\beta$-polymorph of cyclotetramethylene tetranitramine (HMX) energetic molecular crystal using DFT-D2, a first-principles calculation based on density functional theory (DFT) with van der Waals (vdW) corrections. The atomic structures and equation of states under hydrostatic compressions are studied for pressures up to 100 GPa. We found that the N-N bonds along the minor axis of the ring are more sensitive to the variation of pressure, which indicates that they are potential "weak spots" in atomic level within a single molecule of $\beta$-HMX. Our study suggested that the van der Waals interactions are critically important in modeling this molecular crystal.
In the current work we present a computational investigation of high speed penetration response of 3D orthogonal woven fiber composites (3D OWC) utilizing sub-unit cell, meso-level partitioned damage mechanics with the specific aim of... more
In the current work we present a computational investigation of high speed penetration response of 3D orthogonal woven fiber composites (3D OWC) utilizing sub-unit cell, meso-level partitioned damage mechanics with the specific aim of understanding the role of Z-fibers in the mechanical response. In our model, two primary sources of nonlinearities have been addressed – one resulting from the strain rate dependence and large deformation of the composite constituents and the other from evolving failure. We reduce a number of arbitrary parameters typically present in high speed models by taking advantage of specific geometrical properties of 3D OWC which prevent extensive delamination. This property allows us to partition the structure into resin impregnated fibers assumed to be wholly responsible for the progressive damage behavior and bulk resin which is identified as the source of visco-plasticity and strain rate dependence. The fibers are modeled as anisotropic linear elastic with ...
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ANFO (ammonium nitrate/fuel oil) is a widely used bulk industrial explosive mixture that is considered to be highly “non-ideal” with long reaction zones, low detonation energies, and large failure diameters. Thus, its detonation poses... more
ANFO (ammonium nitrate/fuel oil) is a widely used bulk industrial explosive mixture that is considered to be highly “non-ideal” with long reaction zones, low detonation energies, and large failure diameters. Thus, its detonation poses great challenge for accurate numerical modeling. Herein, we present a numerical model to simulate ANFO based on improved smoothed particle hydrodynamics (SPH) method, which is a mesh-free Lagrangian method performing well in simulating situations consist of moving interface and large deformation, as happened in high-velocity impact and explosion. The improved three-dimensional SPH method incorporated with JWL++ model is used to simulate the detonation of ANFO. Good agreement is observed between simulation and experiment, which indicates that the proposed method performs well in prediction of behavior of ANFO.
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Silicane is a fully hydrogenated silicene–a counterpart of graphene–having promising applications in hydrogen storage with capacities larger than 6 wt%. Knowledge of its elastic limit is critical in its applications as well as tailoring... more
Silicane is a fully hydrogenated silicene–a counterpart of graphene–having promising applications in hydrogen storage with capacities larger than 6 wt%. Knowledge of its elastic limit is critical in its applications as well as tailoring its electronic properties by strain. Here we investigate the mechanical response of silicane to various strains using first-principles calculations based on density functional theory. We illustrate that non-linear elastic behavior is prominent in the two-dimensional nanomaterials as opposed to bulk materials. The elastic limits defined by ultimate tensile strains are 0.22, 0.28, and 0.25 along armchair, zigzag, and biaxial directions, respectively, an increase of 29%, 33%, and 24% respectively in reference to silicene. The in-plane stiffness and Poisson ratio are reduced by a factor of 16% and 26%, respectively. However, hydrogenation/dehydrogenation has little effect on its ultimate tensile strengths. We obtained high order elastic constants for a r...
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The FLS training tool box has now been adopted by the Society of Gastrointestinal Endoscopic Surgeons (SAGES) as an official training tool for minimally invasive procedures. To overcome the limitations of the physical FLS training tool... more
The FLS training tool box has now been adopted by the Society of Gastrointestinal Endoscopic Surgeons (SAGES) as an official training tool for minimally invasive procedures. To overcome the limitations of the physical FLS training tool box, we have developed a Virtual Basic Laparoscopic Skill Trainer (VBLaSTTM) system, which is a 3D simulator that will allow trainees to acquire basic laparoscopic skill. The outcome of this work is the development of an integrated visio-haptic workstation environment including force feedback devices and a stereo display interface whereby trainees can practice on virtual versions of the FLS. Realistic graphical rendering and high fidelity haptic interactions are achieved. Surgical skill training is a long and tedious process of acquiring fine motor skills. It is expected that residents would start on trainers such as VBLaSTTM and after reaching a certain level of competence would progress to the more complex trainers for training on specific surgical ...
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In this paper we present a general FEM (finite element method) solution that enables fast dynamic deformation simulation on the newly available GPU (graphics processing unit) hardware with compute unified device architecture (CUDA) from... more
In this paper we present a general FEM (finite element method) solution that enables fast dynamic deformation simulation on the newly available GPU (graphics processing unit) hardware with compute unified device architecture (CUDA) from NVIDIA. CUDA-enabled GPUs harness the power of 128 processors which allow data parallel computations. Compared to the previous GPGPU, it is significantly more flexible with a C language interface. We not only implement FEM deformation computation algorithms with CUDA but also analyze the performance in detail. Our test results indicate that the GPU with CUDA enables about 4 times speedup for FEM deformation computation on an Intel(R) Core 2 Quad 2.0 GHz machine with GeForce 8800 GTX.
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In this paper we present a general software platform that enables real time surgery simulation on the newly available compute unified device architecture (CUDA)from NVIDIA. CUDA-enabled GPUs harness the power of 128 processors which allow... more
In this paper we present a general software platform that enables real time surgery simulation on the newly available compute unified device architecture (CUDA)from NVIDIA. CUDA-enabled GPUs harness the power of 128 processors which allow data parallel computations. Compared to the previous GPGPU, it is significantly more flexible with a C language interface. We report implementation of both collision detection and consequent deformation computation algorithms. Our test results indicate that the CUDA enables a twenty times speedup for collision detection and about fifteen times speedup for deformation computation on an Intel Core 2 Quad 2.66 GHz machine with GeForce 8800 GTX.
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... SIGGRAPH 2001, ACM Transactions on Graphics, 21(3), pp. 582-585, 2002. [6] G. Ranzuglia, P. Cignoni, F. Ganovelli and R. Scopigno. “Implementing mesh-based approaches for deformableobjects on GPU”, Fourth Eurographics Italian Chapter... more
... SIGGRAPH 2001, ACM Transactions on Graphics, 21(3), pp. 582-585, 2002. [6] G. Ranzuglia, P. Cignoni, F. Ganovelli and R. Scopigno. “Implementing mesh-based approaches for deformableobjects on GPU”, Fourth Eurographics Italian Chapter 2006, pp. 213-218, 2006. ...
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To conduct a review of the state of virtual reality (VR) simulation technology, to identify areas of surgical education that have the greatest potential to benefit from it, and to identify challenges to implementation. Simulation is an... more
To conduct a review of the state of virtual reality (VR) simulation technology, to identify areas of surgical education that have the greatest potential to benefit from it, and to identify challenges to implementation. Simulation is an increasingly important part of surgical training. VR is a developing platform for using simulation to teach technical skills, behavioral skills, and entire procedures to trainees and practicing surgeons worldwide. Questions exist regarding the science behind the technology and most effective usage of VR simulation. A symposium was held to address these issues. Engineers, educators, and surgeons held a conference in November 2013 both to review the background science behind simulation technology and to create guidelines for its use in teaching and credentialing trainees and surgeons in practice. Several technologic challenges were identified that must be overcome in order for VR simulation to be useful in surgery. Specific areas of student, resident, a...
We investigate the performance of van der Waals (vdW) functions in predicting the elastic constants of β cyclotetramethylene tetranitramine (HMX) energetic molecular crystals using density functional theory (DFT) calculations. We confirm... more
We investigate the performance of van der Waals (vdW) functions in predicting the elastic constants of β cyclotetramethylene tetranitramine (HMX) energetic molecular crystals using density functional theory (DFT) calculations. We confirm that the accuracy of the elastic constants is significantly improved using the vdW corrections with environment-dependent C6 together with PBE and revised PBE exchange-correlation functionals. The elastic constants obtained using PBE-D3(0) calculations yield the most accurate mechanical response of β-HMX when compared with experimental stress-strain data. Our results suggest that PBE-D3 calculations are reliable in predicting the elastic constants of this material.
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We present a novel real-time technique for cutting during electrocautery procedures in surgical training. Our algorithm is based on cauterizing the part of the tissue that exceeds the critical vaporization temperature. The resulting... more
We present a novel real-time technique for cutting during electrocautery procedures in surgical training. Our algorithm is based on cauterizing the part of the tissue that exceeds the critical vaporization temperature. The resulting topology changes due to cutting are accounted for in real-time. Results presented for the overall electrocautery cutting algorithm show that the real-time costs are minimal and thus allow interactive simulation.
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We report the hydrostatic compression studies of the β-polymorph of a cyclotetramethylene tetranitramine (HMX) energetic molecular crystal using DFT-D2, a first-principles calculation based on density functional theory (DFT) with van der... more
We report the hydrostatic compression studies of the β-polymorph of a cyclotetramethylene tetranitramine (HMX) energetic molecular crystal using DFT-D2, a first-principles calculation based on density functional theory (DFT) with van der Waals (vdW) corrections. The molecular structure, mechanical properties, electronic properties, and equations of state of β-HMX are investigated. For the first time, we predict the elastic constants of β-HMX using DFT-D2 studies. The equations of state under hydrostatic compression are studied for pressures up to 100 GPa. We found that the N-N bonds along the minor axis are responsible for the sensitivity of β-HMX. The analysis of the charge distribution shows that the electronic charge is transferred from hydrogen atoms to nitro groups with the amount of 0.131 and 0.064e for the nitro groups along the minor axis and major axis, respectively, when pressure changes from 0 GPa to 100 GPa. The electronic energy band gap changes from direct at a pressur...
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Multigrid algorithms are gaining popularity in virtual reality simulations as they have a theoretically optimal performance that scales linearly with the number of degrees of freedom of the simulation system. We propose a multilevel... more
Multigrid algorithms are gaining popularity in virtual reality simulations as they have a theoretically optimal performance that scales linearly with the number of degrees of freedom of the simulation system. We propose a multilevel approach that combines the efficiency of the multigrid algorithms with the ability to resolve multi-body constraints during interactive simulations. First, we develop a single level modified block Gauss-Seidel (MBGS) smoother that can incorporate constraints. This is subsequently incorporated in a standard multigrid V-cycle with corrections for constraints to form the modified multigrid V-cycle (MMgV). Numerical results show that the solver can resolve constraints while achieving the theoretical performance of multigrid schemes.
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We propose a principled approach to the design of a computer-based, virtual reality simulator specifically for electrosurgical training. The design builds on the Fundamental Use of Surgical Energy (FUSE) program's didactic curriculum... more
We propose a principled approach to the design of a computer-based, virtual reality simulator specifically for electrosurgical training. The design builds on the Fundamental Use of Surgical Energy (FUSE) program's didactic curriculum and the results of a survey of domain experts on the roles of cognitive knowledge and hands-on training for a selection of electrosurgery tasks. The resulting design focuses narrowly on the tissue effects caused during electrosurgery and the identified physician-controllable factors causing those effects.
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This work presents a pWeb - a new language and compiler for parallelization of client-side compute intensive web applications such as surgical simulations. The recently introduced HTML5 standard has enabled creating unprecedented... more
This work presents a pWeb - a new language and compiler for parallelization of client-side compute intensive web applications such as surgical simulations. The recently introduced HTML5 standard has enabled creating unprecedented applications on the web. Low performance of the web browser, however, remains the bottleneck of computationally intensive applications including visualization of complex scenes, real time physical simulations and image processing compared to native ones. The new proposed language is built upon web workers for multithreaded programming in HTML5. The language provides fundamental functionalities of parallel programming languages as well as the fork/join parallel model which is not supported by web workers. The language compiler automatically generates an equivalent parallel script that complies with the HTML5 standard. A case study on realistic rendering for surgical simulations demonstrates enhanced performance with a compact set of instructions.
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This work introduces, for the first time, a meshless modeling technique, the method of finite spheres, for physically based, real time rendering of soft tissues in medical simulations. The technique is conceptually similar to the... more
This work introduces, for the first time, a meshless modeling technique, the method of finite spheres, for physically based, real time rendering of soft tissues in medical simulations. The technique is conceptually similar to the traditional finite element techniques. However, while the finite element techniques requires a slow mesh generation process, this new technique has significant potential for multimodal medical simulations of the future since it does not use a mesh. Several examples are presented showing the effectiveness of the scheme.
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The lack of data on in-vivo material properties of soft tissues has been a significant impediment in the development of virtual reality based surgical simulators that can provide the user with realistic visual and haptic feedback. As a... more
The lack of data on in-vivo material properties of soft tissues has been a significant impediment in the development of virtual reality based surgical simulators that can provide the user with realistic visual and haptic feedback. As a first step towards characterizing the mechanical behavior of organs, this work presents in-vivo force response of the liver and lower esophagus of pigs when subjected to ramp and hold, and sinusoidal indentations delivered using a haptic feedback device, Phantom, employed as a mechanical stimulator. The results show that pulse significantly affects the reaction forces and that the lower esophagus is 2 to 2.5 times stiffer than the liver.
Research Interests: Health Studies, Computer assisted orthopaedic surgery, Library and Information Studies, Humans, Computer Simulation, and 12 moreLiver, Touch, Computer Assisted Instruction, Animals, Connective tissue, Feedback, Computer User Interface Design, Esophagus, Public health systems and services research, Swine, Abdomen, and Biomechanical Phenomena
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ABSTRACT Modified preconditioned Conjugate Gradient (MpCG) [Baraff and Witkin 1998] is a well known single level solver to implicitly handle linear projection constraints. In this work we propose a novel multilevel framework to implicitly... more
ABSTRACT Modified preconditioned Conjugate Gradient (MpCG) [Baraff and Witkin 1998] is a well known single level solver to implicitly handle linear projection constraints. In this work we propose a novel multilevel framework to implicitly handle linear projection constraints. Our method has multiple advantages: (a) faster (and guaranteed) convergence compared to MpCG (b) ease of integration into existing multilevel codes and (c) minimal overhead cost to incorporate constraints. Linear projection constraints are used in many aspects of the simulation such as internal articulation constraints, external Dirichlet boundary conditions [Arikatla and De 2013], initial projection during collision handling and interactive user manipulation.
Suturing is currently one of the most common procedures in minimally invasive surgery (MIS). We present a suturing simulation paradigm with pre-computed finite element models which include detailed needle-tissue and thread-tissue... more
Suturing is currently one of the most common procedures in minimally invasive surgery (MIS). We present a suturing simulation paradigm with pre-computed finite element models which include detailed needle-tissue and thread-tissue interaction. The interaction forces are derived through a reanalysis technique for haptic feedback. Besides providing deformation updates and high fidelity forces, our simulation is computationally less costly.
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Robotic surgery is preferred over other traditional methods due to reduced complications and improved ergonomics for the operating surgeon. They are also a perfect platform for telesurgery. Automated surgery in which the robot is allowed... more
Robotic surgery is preferred over other traditional methods due to reduced complications and improved ergonomics for the operating surgeon. They are also a perfect platform for telesurgery. Automated surgery in which the robot is allowed to do various surgical tasks with minimal intervention is getting wider attention recently. In this paper, we introduce a simulation framework that can realistically simulate tool tissue interactions in robotic surgery, which can be used to design and test various control methodologies for automated surgical tasks. We present preliminary results from simulating a simple model of a surgical robot interacting with a volumetric model while performing a grasping and hold task.
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Natural orifice translumenal endoscopic surgery is an emerging procedure. High fidelity virtual reality-based simulators allow development of new surgical procedures and tools and train medical personnel without risk to human patients. As... more
Natural orifice translumenal endoscopic surgery is an emerging procedure. High fidelity virtual reality-based simulators allow development of new surgical procedures and tools and train medical personnel without risk to human patients. As part of a project funded by the National Institutes of Health, we are developing a Virtual Transluminal Endoscopic Surgery Trainer (VTEST TM) for this purpose. In this work, objective performance measures derived from motion tracking sensors attached to an endoscope was tested for the transgastric NOTES appendectomy procedure performed with ex-vivo pig organs using the EASIE-R(TM) trainer box. Results from our study shows that both completion time and economy of motion parameters were able to differentiate between expert and novice NOTES surgeons with p value of 0.039 and 0.02 respectively. Jerk computed on sensor 2 data also showed significant results (p = 0.02). We plan to incorporate these objective performance measures in VTEST(TM).
Research Interests: Educational Measurement, Computer assisted orthopaedic surgery, Library and Information Studies, Humans, Transducers, and 8 moreComputer Assisted Instruction, Motion, Computer User Interface Design, Public health systems and services research, Professional Competence, Equipment Design, Equipment Failure Analysis, and Motor Skills
Natural orifice translumenal endoscopic surgery (NOTES) is a minimally invasive procedure, known for its scar-less nature and short post operative recovery periods. A critical skill necessary for a NOTES procedure is the surgeon's... more
Natural orifice translumenal endoscopic surgery (NOTES) is a minimally invasive procedure, known for its scar-less nature and short post operative recovery periods. A critical skill necessary for a NOTES procedure is the surgeon's ability to navigate and gain visualization of the target organ, which is done by moving the endoscope tip using the dials on the handle. We have developed an accurate and high resolution optical encoder based system to measure that dial manipulations, as part of a larger project to develop a VR-NOTES surgical simulator.
Research Interests: Computer assisted orthopaedic surgery, Library and Information Studies, Humans, Transducers, Computer Assisted Instruction, and 7 moreThree Dimensional Imaging, Optical devices, Computer User Interface Design, Public health systems and services research, Equipment Design, Equipment Failure Analysis, and Man–machine Systems
Virtual surgical skills trainers are proving to be very useful for the medical training community. With efforts to increase patient safety and surgeon expertise, the need for surgical skills trainers that provide training in an operating... more
Virtual surgical skills trainers are proving to be very useful for the medical training community. With efforts to increase patient safety and surgeon expertise, the need for surgical skills trainers that provide training in an operating room (OR) like condition is now more pressing. To allow for virtual surgery simulators to be instructed in an OR-like setting we have created a large display based immersive surgical simulation environment. Using the Microsoft Kinect we have created a real-time simulation environment that tracks the test user and appropriately adjust the perspective of the virtual OR for an immersive virtual experience.
Research Interests: Computer assisted orthopaedic surgery, Library and Information Studies, Humans, Transducers, Computer Assisted Instruction, and 8 moreThree Dimensional Imaging, Computer User Interface Design, Head Movements, Ecosystem, Public health systems and services research, Equipment Design, Cooperative Behavior, and Equipment Failure Analysis
Natural Orifice Translumenal Endoscopic Surgery is an emerging procedure that requires training and adoption to be successful. Currently no objective performance metrics exist for evaluating skills for NOTES. In this work, we have... more
Natural Orifice Translumenal Endoscopic Surgery is an emerging procedure that requires training and adoption to be successful. Currently no objective performance metrics exist for evaluating skills for NOTES. In this work, we have improved upon our previous study on objective performance metrics using kinematic measures by introducing two new measures, the flex and the roll and recruiting more subjects to increase the statistical power. The measures were evaluated in a transgastric NOTES appendectomy procedure performed with ex-vivo organs using the EASIE-R<sup>TM</sup> trainer box. Four motion tracking sensors attached to an endoscope were used to measure the scope position and orientation to compute the kinematic measures. Results from our study showed that completion time, economy of motion, jerk and roll of the scope are valid kinematic measures to differentiate between expert and novice NOTES surgeons.
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Providing cognitive feedback in a virtual reality simulator during training is essential for subjects to correct and learn proper techniques. In this work, we have developed a framework to identify key skills and cognitive knowledge... more
Providing cognitive feedback in a virtual reality simulator during training is essential for subjects to correct and learn proper techniques. In this work, we have developed a framework to identify key skills and cognitive knowledge required to perform a task and methods to provide to the user. The framework was verified by implementing a test case scenario with the peg transfer task of the FLS.
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The Fundamentals of Laparoscopic Surgery (FLS) trainer is currently the standard for training and evaluating basic laparoscopic skills. However, its manual scoring system is time-consuming and subjective. The Virtual Basic Laparoscopic... more
The Fundamentals of Laparoscopic Surgery (FLS) trainer is currently the standard for training and evaluating basic laparoscopic skills. However, its manual scoring system is time-consuming and subjective. The Virtual Basic Laparoscopic Skill Trainer (VBLaST(©)) is the virtual version of the FLS trainer which allows automatic and real time assessment of skill performance, as well as force feedback. In this study, the VBLaST(©) pattern cutting (VBLaST-PC(©)) and ligating loop (VBLaST-LL(©)) tasks were evaluated as part of a validation study. We hypothesized that performance would be similar on the FLS and VBLaST(©) trainers, and that subjects with more experience would perform better than those with less experience on both trainers. Fifty-five subjects with varying surgical experience were recruited at the Learning Center during the 2013 SAGES annual meeting and were divided into two groups: experts (PGY 5, surgical fellows and surgical attendings) and novices (PGY 1-4). They were ask...
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We have developed an instrumented endoscope grip handle equipped with a 6-axis load cell and measured forces and torques during a simulated transgastric NOTES appendectomy procedure performed in an EASIE-R© ex vivo simulator. The data... more
We have developed an instrumented endoscope grip handle equipped with a 6-axis load cell and measured forces and torques during a simulated transgastric NOTES appendectomy procedure performed in an EASIE-R© ex vivo simulator. The data were collected from 10 participating surgeons of varying degrees of expertise which was analyzed to compute a set of 6 force and torque parameters for each coordinate axis for each of the nine tasks of the appendectomy procedure. The mean push/pull force was found to be 3.64 N (σ=3.54 N) in the push direction and the mean torque was 3.3 N-mm (σ=38.6 N-mm) in the counter-clockwise direction about the push/pull axis. Most interestingly, the force and torque data about the non-dominant x and z axes showed a statistically significant difference (p<0.05) between the expert and novice groups for five of the nine tasks. This data may be useful in developing surgical platforms especially new haptic devices and simulation systems for emerging natural orifice...
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Research Interests:
With ever growing attention of medical community on the usage of surgical simulators as effective training means, development of robust and cost-effective haptic tool interfaces is very much necessary. We have developed such tool... more
With ever growing attention of medical community on the usage of surgical simulators as effective training means, development of robust and cost-effective haptic tool interfaces is very much necessary. We have developed such tool interfaces that can be easily plugged to PHANTOM Omni. Besides simulating actual tools in operating room, they are cost-effective and are easy to build.
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The first virtual-reality-based simulator for Natural Orifice Translumenal Endoscopic Surgery (NOTES) is developed called the Virtual Translumenal Endoscopic Surgery Trainer (VTEST<sup>TM</sup>). VTEST<sup>TM</sup>... more
The first virtual-reality-based simulator for Natural Orifice Translumenal Endoscopic Surgery (NOTES) is developed called the Virtual Translumenal Endoscopic Surgery Trainer (VTEST<sup>TM</sup>). VTEST<sup>TM</sup> aims to simulate hybrid NOTES cholecystectomy procedure using a rigid scope inserted through the vaginal port. The hardware interface is designed for accurate motion tracking of the scope and laparoscopic instruments to reproduce the unique hand-eye coordination. The haptic-enabled multimodal interactive simulation includes exposing the Calot's triangle and detaching the gall bladder while performing electrosurgery. The developed VTEST<sup>TM</sup> was demonstrated and validated at NOSCAR 2013.
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This paper presents the development of extracorporeal suturing simulation in Virtual Basic Laparoscopic Skill Trainer (VBLaST<sup>©</sup>). A novel hardware interface is designed to allow the user to perform the physical... more
This paper presents the development of extracorporeal suturing simulation in Virtual Basic Laparoscopic Skill Trainer (VBLaST<sup>©</sup>). A novel hardware interface is designed to allow the user to perform the physical action of trying a knot and seamlessly integrate the knot into the virtual simulation.
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The self-interstitial atoms (SIAs) mediate the evolution of micro-structures which is crucial in understanding the instabilities of hexagonal close packed (HCP) structures. Taking zirconium as a prototype, we investigate the pressure... more
The self-interstitial atoms (SIAs) mediate the evolution of micro-structures which is crucial in understanding the instabilities of hexagonal close packed (HCP) structures. Taking zirconium as a prototype, we investigate the pressure effect on the stabilities of SIAs using first-principles calculations based on density-functional theory. We found that the pressure greatly affects the stability of the SIAs. The SIAs in basal planes are more stable under pressure. The SIA configuration of the lowest formation energy changes from basal octahedral (BO) to octahedral (O) at a pressure of 21 GPa. The lowest formation enthalpy configuration switches from BO to S (split-dumbbell) at the pressure of 30 GPa. The formation volumes of SIAs decrease monotonically in response to an increase in pressure. Our results reveal that it is important to take pressure effects into account when predicting the micro-structural evolution of HCP structures.
This study investigates the sensitivity of fiber placement positioning for the purpose of prefrontal cortex imaging using functional near-infrared spectroscopy (fNIRS). Results indicate that our proposed optode placement has higher... more
This study investigates the sensitivity of fiber placement positioning for the purpose of prefrontal cortex imaging using functional near-infrared spectroscopy (fNIRS). Results indicate that our proposed optode placement has higher scaled-absorption sensitivity than the traditional International 10-20 system for optode placement based on Monte Carlo simulations.
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Studies on a virtual reality simulator have demonstrated that sleep-deprived residents make more errors. Work-hour restrictions were implemented, among other reasons, to ensure enough sleep time for residents. The objective of this study... more
Studies on a virtual reality simulator have demonstrated that sleep-deprived residents make more errors. Work-hour restrictions were implemented, among other reasons, to ensure enough sleep time for residents. The objective of this study was to assess the effects of sleep time, perceived fatigue, and experience on surgical performance. We hypothesized that performance would decrease with less sleep and fatigue, and that experienced surgeons would perform better than less experienced surgeons despite sleep deprivation and fatigue. Twenty-two surgical residents and attendings performed a peg transfer task on two simulators: the Fundamentals of Laparoscopic Skills (FLS) trainer and the Virtual Basic Laparoscopic Surgical Trainer (VBLaST©), a virtual version of the FLS. Participants also completed questionnaires to assess their fatigue level and recent sleep hours. Each subject performed ten trials on each simulator in a counterbalanced order. Performance was measured using the FLS normalized scores and analyzed using a multiple regression model. The multiple regression analysis showed that sleep hours and perceived fatigue were not covariates. No correlation was found between experience level and sleep hours or fatigue. Sleep hours and fatigue did not appear to affect performance. Expertise level was the only significant determinant of performance in both FLS and VBLaST©. Restricting resident work hours was expected to result in less fatigue and better clinical performance. In our study, peg transfer task performance was not affected by sleep hours. Experience level was a significant indicator of performance. Further examination of the complex relationship between sleep hour, fatigue, and clinical performance is needed to support the practice of work-hour restriction for surgical residents.
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The Fundamentals of Laparoscopic Surgery (FLS) trainer box is now established as a standard for evaluating minimally invasive surgical skills. A particularly simple task in this trainer box is the peg transfer task which is aimed at... more
The Fundamentals of Laparoscopic Surgery (FLS) trainer box is now established as a standard for evaluating minimally invasive surgical skills. A particularly simple task in this trainer box is the peg transfer task which is aimed at testing the surgeon&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s bimanual dexterity, hand-eye coordination, speed, and precision. The Virtual Basic Laparoscopic Skill Trainer (VBLaST) is a virtual version of the FLS tasks which allows automatic scoring and real-time, subjective quantification of performance without the need of a human proctor. In this article we report validation studies of the VBLaST peg transfer (VBLaST-PT) simulator. Thirty-five subjects with medical background were divided into two groups: experts (PGY 4-5, fellows, and practicing surgeons) and novices (PGY 1-3). The subjects were asked to perform the peg transfer task on both the FLS trainer box and the VBLaST-PT simulator; their performance was evaluated based on established metrics of error and time. A new length of trajectory (LOT) metric has also been introduced for offline analysis. A questionnaire was used to rate the realism of the virtual system on a 5-point Likert scale. Preliminary face validation of the VBLaST-PT with 34 subjects rated on a 5-point Likert scale questionnaire revealed high scores for all aspects of simulation, with 3.53 being the lowest mean score across all questions. A two-tailed Mann-Whitney test performed on the total scores showed significant (p = 0.001) difference between the groups. A similar test performed on the task time (p = 0.002) and the LOT (p = 0.004) separately showed statistically significant differences between the experts and the novices (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). The experts appear to be traversing shorter overall trajectories in less time than the novices. VBLaST-PT showed both face and construct validity and has promise as a substitute for the FLS for training peg transfer skills.
Research Interests:
Development of a laparoscopic 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... more
Development of a laparoscopic 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. As experiments on live human patients present significant risks, the use of cadavers presents an alternative. We present techniques of measuring and modeling the mechanical response of human cadaveric tissue for the purpose of developing a realistic 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. To investigate the in situ mechanical, static, and dynamic properties of intra-abdominal organs, we have developed a high-precision instrument by retrofitting a robotic device from Sensable Technologies (position resolution of 0.03 mm) with a six-axis Nano 17 force-torque sensor from ATI Industrial Automation (force resolution of 1/1,280 N along each axis), and used it to apply precise displacement stimuli and record the force response of liver and stomach of ten fresh human cadavers. The mean elastic modulus of liver and stomach is estimated as 5.9359 kPa and 1.9119 kPa, respectively over the range of indentation depths tested. We have also obtained the parameters of a quasilinear viscoelastic (QLV) model to represent the nonlinear viscoelastic behavior of the cadaver stomach and liver over a range of indentation depths and speeds. The models are found to have an excellent goodness of fit (with R (2) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 0.99). The data and models presented in this paper together with additional ones based on the principles presented in this paper would result in realistic physics-based surgical simulators.