Computational Analysis of Surgical Tool-Brain Tissue Interaction

This paper presents new surgical tool-brain tissue interactions models in three directional format considering the linear elastic, hyperelastic and viscoelastic properties of a brain tissue which are characterized by conducting stress-strain simulation on brain model. Brain tissues properties like a Neo-Hookean, Mooney-Rivlin Model and Prony Series are considered. Effects of adopting non-linear properties are discussed. After optimizing models in COMSOL Muiltiphysics 4.0, the models show that the brain tissues contain non-linear characteristic and the coefficients of the models are available to Open Inventor in order to initiate a visio-haptic simulation which will be used for doctors and surgical operation manipulators

Force Measurement Methods in Telerobotic Surgery: Implications for End-Effector Manufacture

Haptic feedback in telesurgical applications refers to the relaying of position and force information from a remote surgical site to the surgeon in real-time during a surgical procedure. This feedback, coupled with visual information via microscopic cameras, has the potential to provide the surgeon with additional ‘feel’ for the manipulations being performed at the instrument-biological tissue interface. This increased sensitivity has many associated benefits which include, but are not limited to; minimal tissue damage, reduced recuperation periods, and less patient trauma. The inclusion of haptic feedback leads to reduction in surgeon fatigue which contributes to enhanced performance during operation. Commercially available Minimally Invasive Robotic Surgical (MIRS) systems are being widely used, the best-known examples being from the daVinci® by Intuitive Surgical Inc. However, currently these systems do not possess force feedback capability which therefore restricts their use during many delicate and complex procedures. The ideal system would consist of a multi-degree-of-freedom framework which includes end-effector instruments with embedded force sensing included. A force sensing characterisation platform has been developed by this group which facilitates the evaluation of force sensing technologies. Surgical scissors have been chosen as the instrument and biological tissue phantom specimens have been used during testing. This test-bed provides accurate, repeatable measurements of the forces produced at the interface between the tissue and the scissor blades during cutting using conventional sensing technologies. The primary focus of this paper is to provide a review of the traditional and developing force sensing technologies with a view to establishing the most appropriate solution for this application. The impact that an appropriate sensing technology has on the manufacturability of the instrument end-effector is considered. Particular attention is given to the issues of embedding the force sensing transducer into the instrument tip

Force Feedback is Noticeably Different for Linear versus Nonlinear Elastic Tissue Models

Realistic modeling of the interaction between surgical instruments and human organs has been recognized as a key requirement in the development of high-fidelity surgical simulators. Primarily due to computational considerations, most of the past simulation research within the haptics community has assumed linear elastic behavior for modeling tissues, even though human soft tissues generally possess nonlinear viscoelastic properties. Hence, this paper quantitatively compares linear and nonlinear elasticity-based models. It is demonstrated that, for a nonlinear model, the well-known Poynting effect developed during shearing of the tissue results in normal forces not seen in a linear elastic model. The difference in force magnitude and force direction for linear and nonlinear models are larger than the just noticeable difference for contact force and forcedirection discrimination thresholds published in the psychophysics literature, respectively. This work applies a proposed framework for examining the effect of tool-tissue interaction modeling techniques on human perception of surgical simulators with haptic feedback. 1

Large Deformation Object Modeling Using Finite Element Method And Proper Orthogonal Decomposition For Haptic Robots

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2008Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2008Bu çalışmada, hissedici arabirimler ve bu arabirimlerde kullanılan hesaplama metotları incelenmiştir. Bu amaçla doğrultusunda, yüksek deformasyon özelliğine sahip doğrusal olmayan bir kirişin modeli sonlu elemanlar metodu kullanılarak elde edilmiştir ve bu model gerçek zamalı olarak PHANTOM® Premium 6 DOF hissedici arabirimi ile etkileşime geçirilmiştir. Etkileşimi elde etmek amacıyla, kiriş modeli OpenGL kütüphanesi kullanılarak görselleştirilmiştir ve cihaza OpenHaptics kütüphanesinin HDAPI fonksiyonları kullanılarak hükmedilmiştir. Hissedici cihazların ihtiyaç duyduğu yüksek hesaplama hızlarını elde edebilmek amacıyla uygun ortogonal ayrıştırma metodunu kullanarak düşük mertebeli model elde edilmiştir. Her iki modelin davranışı incelendiginde uygun orthogonal ayrıştırma metodunun, orjinal model davranışı gösterdiği saptanmış ve hesaplama zamanlarının büyük oranda azaldığı görülmüştür.In this study, haptic systems are introduced with investigation of haptic interfaces and haptic rendering. To this end, a large deformation real time beam model is developed and integrated with the PHANTOM® Premium 6 DOF haptic robot. OpenGL library is used as a visualization tool of the model and the haptic robot is manipulated using libraries of OpenHaptics named as HDAPI. In order to obtain high computational demands of the haptic systems, Proper Orthogonal Decomposition method is used to obtain a low order model. Investigations of both models have revealed that lower order model behaves exactly in a similar manner as the original model with reduced computational effort.Yüksek LisansM.Sc

Force Sensing Surgical Scissor Blades using Fibre Bragg Grating Sensors

This thesis considers the development and analysis of unique sensorised surgical scissor blades for application in minimally invasive robotic surgery (MIRS). The lack of haptic (force and tactile) feedback to the user is currently an unresolved issue with modern MIRS systems. This thesis presents details on smart sensing scissor blades which enable the measurement of instrument-tissue interaction forces for the purpose of force reflection and tissue property identification. A review of current literature established that there exists a need for small compact, biocompatible, sterilisable and robust sensors which meet the demands of current MIRS instruments. Therefore, the sensorised blades exploit the strain sensing capabilities of a single fibre Bragg grating (FBG) sensor bonded to their surface. The nature and magnitude of the strain likely to be experienced by the blades, and consequently the FBG sensor, while cutting soft tissue samples were characterised through the use of an application specific test-bed. Using the sensorised blades to estimate fracture properties is proposed, hence two methods of extracting fracture toughness information from the test samples are assessed and compared. Investigations were carried out on the factors affecting the transfer of strain from the blade material to the core of the FBG sensor for surface mounted or partially embedded arrangements. Results show that adhesive bond length, thickness and stiffness need to be carefully specified when bonding FBG sensors to ensure effective strain transfer. Calibration and dynamic cutting experiments were carried out using the characterisation test-bed. The complex nature of the blade interaction forces were modelled, primarily for the purpose of decoupling the direct, lateral, friction and fracture strains experienced by the bonded FBG sensor during cutting. The modelled and experimental results show that the approach taken in sensorising the blade enables detailed cutting force data to be obtained and consequently leads to a unique method in estimating the kinetic friction coefficient for the blades. The forces measured using the FBG are validated against a commercial load cell used in the test-bed. This research work demonstrates that this unique approach of placing a single optical fibre onto the scissor blades can, in an unobtrusive manner, measure interblade friction forces and material fracture properties occurring at the blade-tissue interface