Force measurement capability for robotic assisted minimally invasive surgery systems

An automated laparoscopic instrument capable of non-invasive measurement of tip/tissue interaction forces for direct application in robotic assisted minimally invasive surgery systems_ is introduced in this paper. It has the capability to measure normal grasping forces as well as lateral interaction forces without any sensor mounted on the tip jaws. Further to non-invasive actuation of the tip, the proposed instrument is also able to change the grasping direction during surgical operation. Modular design of the instrument allows conversion between surgical modalities (e.g., grasping, cutting, and dissecting). The main focus of this paper is on evaluation of the grasping force capability of the proposed instrument. The mathematical formulation of fenestrated insert is presented and its non-linear behaviour is studied. In order to measure the stiffness of soft tissues, a device was developed that is also described in this paper. Tissue characterisation experiments were conducted and results are presented and analysed here. The experimental results verify the capability of the proposed instrument in accurately measuring grasping forces and in characterising artificial tissue samples of varying stiffness.<br /

Mechanics of fragmentation of crocodile skin and other thin films

Fragmentation of thin layers of materials is mediated by a network of cracks on its surface. It is commonly seen in dehydrated paintings or asphalt pavements and even in graphene or other two-dimensional materials, but is also observed in the characteristic polygonal pattern on a crocodile’s head. Here, we build a simple mechanical model of a thin film and investigate the generation and development of fragmentation patterns as the material is exposed to various modes of deformation. We find that the characteristic size of fragmentation, defined by the mean diameter of polygons, is strictly governed by mechanical properties of the film material. Our result demonstrates that skin fragmentation on the head of crocodiles is dominated by that it features a small ratio between the fracture energy and Young’s modulus, and the patterns agree well with experimental observations. Understanding this mechanics-driven process could be applied to improve the lifetime and reliability of thin film coatings by mimicking crocodile skin

Deep Reinforcement Learning in Surgical Robotics: Enhancing the Automation Level

Surgical robotics is a rapidly evolving field that is transforming the landscape of surgeries. Surgical robots have been shown to enhance precision, minimize invasiveness, and alleviate surgeon fatigue. One promising area of research in surgical robotics is the use of reinforcement learning to enhance the automation level. Reinforcement learning is a type of machine learning that involves training an agent to make decisions based on rewards and punishments. This literature review aims to comprehensively analyze existing research on reinforcement learning in surgical robotics. The review identified various applications of reinforcement learning in surgical robotics, including pre-operative, intra-body, and percutaneous procedures, listed the typical studies, and compared their methodologies and results. The findings show that reinforcement learning has great potential to improve the autonomy of surgical robots. Reinforcement learning can teach robots to perform complex surgical tasks, such as suturing and tissue manipulation. It can also improve the accuracy and precision of surgical robots, making them more effective at performing surgeries

The role of flute morphology in mechanical behaviour of corrugated fibreboard : a numerical, analytical and empirical study : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Palmerston North, New Zealand

Corrugated fibreboard (CFB) packaging is designed to protect its contents during the shipping and storage of goods – a role threatened by damage to the CFB. Damaged goods will not only make the customers unhappy but also cause significant loss to the suppliers. As different goods require different design of CFB box, there is no one solution fits all to overcome this issue. This thesis was focused on understanding the fundamentals of CFB damage, relating the damage with the strength loss, and including the damage in strength predictive tools such as finite element (FE) and analytical models to allow for faster design of CFB boxes and the possibility of finding optimal solutions for different requirements. The type of CFB damage that the research narrowed down into was changes to the flute profile that could arise. Such flute damage could be unintentional (crushing and indentation at any stage during the shelf life of the packaging) or intentional (accompanying perforation for instance – a design option to provide secondary functionality such as in shelf ready applications). There is currently no systematic way of observing and quantifying the structure of the flute profile to allow for a proper understanding of the morphology of the flute. Typically, this is done either through measuring the change in calliper or direct observation on the profiles at the edge of CFB blanks which suffers additional physical damage due indentation from the cutting process. A new technique was presented to be able to do this by laser cutting the samples and digitalising the flutes. The method also includes a statistical tool that can compare different flutes and quantify the change in morphology through a variable called the ‘Similarity Factor’. The technique was demonstrated for flute profiles with different extents of crushing, and also allowed for transferring the digitalised profile for FE modelling purposes. Developing a full box compression strength (BCT) FE model with the micro-geometry of the fluting structure can be very time consuming as it will involve a huge number of mesh element and result in a long simulation time. So to overcome this, smaller component models like the bending and crushing tests that have been shown to be the largest factor affecting the BCT were developed with micro-geometry structure that allowed for significantly less computation time and better understanding of the effect of flute profile. A new finding identified through the application of the bending model was that the orientation of the sample can be rotated to find an optimal orientation angle that gives the best bending stiffness and maximum bending force performance. Analytical models were also assembled, and their performance compared with the FE models. These provided accurate outcomes for bending but were limited in cases such as inability to predict the maximum bending force and determining the locus of failure. Global damage to the CFB was simulated through deliberately crushing samples to different extents experimentally. The effect of different levels of crushing on flute morphology and mechanical performance was measured through image analysis, torsional, compressive and bending tests. These tests showed that the torsional behaviour of CFB had the highest sensitivity to crushing at low levels. Since the flute morphology measurements showed negligible changes (the original flute geometry was recovered after crushing), it is suggested that the crushing could affect other localised damage to CFB components such as to the fibres in the constituent papers. Further investigation of the extent and nature of this damage could be an interesting extension to find out its relation to the BCT. On the other hand, the reduction in bending strength and edge crush test followed a similar tend to change in flute morphology with increasing crush levels. This shows that some of the loss in strength could be attributed to the change in flute geometry as well as the reduction in calliper (beyond a threshold where morphology was recoverable after compression). By combining the new tool to characterise the flute structure and with models of varying complexity, their ability to predict the strength of CFB at different extents of crushing could be compared (simulating unintentional damage). These models consisted of an actual flute geometry, idealized flute geometry and an equivalent flute geometry FE models along with analytical solution models. This comparison showed that the use of an actual flute geometry was useful to predict mechanical performance but that the dominant effect on bending strength is the calliper and the flute morphology is a secondary influence. The utility of the FE model was further demonstrated with inclusion of an intentional localised damage through perforation. The model accurately predicted the drop in the experimentally measured apparent bending stiffness. The findings of the localised perforation study also demonstrated that the bending force of the CFB can be significantly improved by avoiding punching through the peaks that rest on the compressive side of the liner. The key new contribution of this research was the development of new a way to accurately measure and describe the actual flute profile within CFB exposed to pre-test damage. The profile allowed geometric damage to be quantified and for the true profile to be included in detailed finite element modelling of mechanical behavior. The effect of flute damage on the mechanical behavior of CFB could therefore be determined and predicted and allowed the potential effects on the strength of CFB packages to be inferred

Recent Advances in Soft Biological Tissue Manipulating Technologies

Biological soft tissues manipulation, including conventional (mechanical) and nonconventional (laser, waterjet and ultrasonic) processes, is critically required in most surgical innervations. However, the soft tissues, with their nature of anisotropic and viscoelastic mechanical properties, and high biological and heat sensitivities, are difficult to manipulated. Moreover, the mechanical and thermal induced damage on the surface and surrounding tissue during the surgery can impair the proliferative phase of healing. Thus, understanding the manipulation mechanism and the resulted surface damage is of importance to the community. In recent years, more and more scholars carried out researches on soft biological tissue cutting in order to improve the cutting performance of surgical instruments and reduce the surgery induced tissue damage. However, there is a lack of compressive review that focused on the recent advances in soft biological tissue manipulating technologies. Hence, this review paper attempts to provide an informative literature survey of the state-of-the-art of soft tissue manipulation processes in surgery. This is achieved by exploring and recollecting the different soft tissue manipulation techniques currently used, including mechanical, laser, waterjet and ultrasonic cutting and advanced anastomosis and reconstruction processes, with highlighting their governing removal mechanisms as well as the surface and subsurface damages

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

Realistic tool-tissue interaction models for surgical simulation and planning

Surgical simulators present a safe and potentially effective method for surgical training, and can also be used in pre- and intra-operative surgical planning. Realistic modeling of medical interventions involving tool-tissue interactions has been considered to be a key requirement in the development of high-fidelity simulators and planners. The soft-tissue constitutive laws, organ geometry and boundary conditions imposed by the connective tissues surrounding the organ, and the shape of the surgical tool interacting with the organ are some of the factors that govern the accuracy of medical intervention planning.\ud \ud This thesis is divided into three parts. First, we compare the accuracy of linear and nonlinear constitutive laws for tissue. An important consequence of nonlinear models is the Poynting effect, in which shearing of tissue results in normal force; this effect is not seen in a linear elastic model. The magnitude of the normal force for myocardial tissue is shown to be larger than the human contact force discrimination threshold. Further, in order to investigate and quantify the role of the Poynting effect on material discrimination, we perform a multidimensional scaling study. Second, we consider the effects of organ geometry and boundary constraints in needle path planning. Using medical images and tissue mechanical properties, we develop a model of the prostate and surrounding organs. We show that, for needle procedures such as biopsy or brachytherapy, organ geometry and boundary constraints have more impact on target motion than tissue material parameters. Finally, we investigate the effects surgical tool shape on the accuracy of medical intervention planning. We consider the specific case of robotic needle steering, in which asymmetry of a bevel-tip needle results in the needle naturally bending when it is inserted into soft tissue. We present an analytical and finite element (FE) model for the loads developed at the bevel tip during needle-tissue interaction. The analytical model explains trends observed in the experiments. We incorporated physical parameters (rupture toughness and nonlinear material elasticity) into the FE model that included both contact and cohesive zone models to simulate tissue cleavage. The model shows that the tip forces are sensitive to the rupture toughness. In order to model the mechanics of deflection of the needle, we use an energy-based formulation that incorporates tissue-specific parameters such as rupture toughness, nonlinear material elasticity, and interaction stiffness, and needle geometric and material properties. Simulation results follow similar trends (deflection and radius of curvature) to those observed in macroscopic experimental studies of a robot-driven needle interacting with gels

Variational methods for modeling and simulation of tool-tissue interaction

Ph.DDOCTOR OF PHILOSOPH

Smart knives: controlled cutting schemes to enable advanced endoscopic surgery

With the backdrop of the rapidly developing research in Natural Orifice Transluminal Endoscopic Surgery (NOTES), analysis of the literature supported the view that inventing new, controlled tissue dissection methods for flexible endoscopic surgery may be necessary. The literature also confirmed that white space exists for research into and the development of new cutting tools. The strategy of “deconstructing dissection” proposed in this thesis may provide dissection control benefits, which may help address the unique manoeuvring challenges for tissue dissection at flexible endoscopy. This assertion was supported by investigating six embodiments of the strategy which provided varying degrees of enhanced tissue dissection control. Seven additional concepts employing the strategy which were not prototyped also were offered as potential solutions that eventually might contribute evidence in defence of the strategy. One concept for selective ablation — dye-mediated laser ablation — was explored in-depth by theoretical analysis, experimentation and computation. The ablation process was found to behave relatively similar to unmediated laser ablation, but also to depend on cyclic carbonisation for sustained ablation once the dye had disappeared. An Arrhenius model of carbonisation based on the pyrolysis and combustion of wood cellulose was used in a tissue ablation model, which produced reasonable results. Qualitative results from four methods for dye application and speculation on three methods for dye removal complete the framework by which dye-mediated laser ablation might deliver on the promise offered by “deconstructing dissection”. Overall, this work provided the “deconstructing dissection” strategic framework for controlled cutting schemes and offered plausible evidence that the strategy could work by investigating embodiments of the scheme. In particular, dye-mediated laser ablation can provide selective ablation of tissue, and a theoretical model for the method of operation was offered. However, some practical hurdles need to be overcome before it can be useful in a clinical setting