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 /

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

The Next-Generation Surgical Robots

The chronicle of surgical robots is short but remarkable. Within 20 years since the regulatory approval of the first surgical robot, more than 3,000 units were installed worldwide, and more than half a million robotic surgical procedures were carried out in the past year alone. The exceptionally high speeds of market penetration and expansion to new surgical areas had raised technical, clinical, and ethical concerns. However, from a technological perspective, surgical robots today are far from perfect, with a list of improvements expected for the next-generation systems. On the other hand, robotic technologies are flourishing at ever-faster paces. Without the inherent conservation and safety requirements in medicine, general robotic research could be substantially more agile and explorative. As a result, various technical innovations in robotics developed in recent years could potentially be grafted into surgical applications and ignite the next major advancement in robotic surgery. In this article, the current generation of surgical robots is reviewed from a technological point of view, including three of possibly the most debated technical topics in surgical robotics: vision, haptics, and accessibility. Further to that, several emerging robotic technologies are highlighted for their potential applications in next-generation robotic surgery

Analysis of Strain Transfer to FBG’s for Sensorized Telerobotic End-effector Applications

Sensorized instruments which cater for the measurement of interaction forces during surgical procedures are not available on current commercial Minimally Invasive Robotic Surgical (MIRS) systems. This paper investigates the ef-fectiveness of advanced optical sensing technology (Fiber Bragg Grating) as sur-gical end effector strain/force sensors. The effects of adhesive bonding layer thickness and length are specifically addressed owing to their importance for ef-fective strain transfer and ensuring compactness of the resulting sensing arrange-ment. The strain transfer characteristics of the compound sensing arrangement are evaluated by the examination of shear transfer through the fiber coating and adhe-sive layers. Detailed analysis of the sensing scheme is facilitated through the use of FEA. Validation of the resulting models is achieved through experimentation carried out on an application-specific evaluation platform. Results show that strain values from an FBG are comparable to that of an electrical strain gauge sensor

The Design and Development of an Intelligent Atraumatic Laparoscopic Grasper

A key tool in laparoscopic surgery is the grasper, which is the surgeon’s main means of manipulating tissue within the body. However inappropriate use may lead to tissue damage and poor surgical outcomes. This thesis presents a novel approach to the assessment and prevention of tissue damage caused by laparoscopic graspers. The research focusses on establishing typical grasping characteristics used in surgery and thus developing a model of mechanically induced tissue trauma. A review explored the state-of-the-art in devices for measuring surgical grasping, tissue mechanics, and damage quantification to inform the research. An instrumented grasper was developed to characterise typical surgical tasks, enabling the grasping force and jaw displacement to be measured. This device was then used to quantitatively characterise grasper use in an in-vivo porcine model where the device was used to perform organ retraction and manipulation tasks. From this work, the range of forces and the grasping times used in certain tasks were determined and this information was used to guide the rest of the study. The in-vivo investigation highlighted a need for grasping in a controlled environment where the tissue’s mechanical properties could be studied. A grasper test rig was designed and developed to provide automated controlled grasping of ex-vivo tissue. This allowed the mechanical properties of tissue to be determined and analysed for indications of tissue damage. A series of experimental studies were conducted with this system which showed how the mechanical response of tissue varies depending on the applied grasping force characteristics, and how this is indicative of tissue damage through comparison to histological analysis. These data were then used to develop a model which predicts the likelihood and severity of tissue damage during grasping, based on the input conditions of grasping force and time. The model was integrated into the instrumented grasper system to provide a tool which could enable real-time grading and feedback of grasping during surgery, or be used to inform best practice in training scenarios

Cable-driven parallel mechanisms for minimally invasive robotic surgery

Minimally invasive surgery (MIS) has revolutionised surgery by providing faster recovery times, less post-operative complications, improved cosmesis and reduced pain for the patient. Surgical robotics are used to further decrease the invasiveness of procedures, by using yet smaller and fewer incisions or using natural orifices as entry point. However, many robotic systems still suffer from technical challenges such as sufficient instrument dexterity and payloads, leading to limited adoption in clinical practice. Cable-driven parallel mechanisms (CDPMs) have unique properties, which can be used to overcome existing challenges in surgical robotics. These beneficial properties include high end-effector payloads, efficient force transmission and a large configurable instrument workspace. However, the use of CDPMs in MIS is largely unexplored. This research presents the first structured exploration of CDPMs for MIS and demonstrates the potential of this type of mechanism through the development of multiple prototypes: the ESD CYCLOPS, CDAQS, SIMPLE, neuroCYCLOPS and microCYCLOPS. One key challenge for MIS is the access method used to introduce CDPMs into the body. Three different access methods are presented by the prototypes. By focusing on the minimally invasive access method in which CDPMs are introduced into the body, the thesis provides a framework, which can be used by researchers, engineers and clinicians to identify future opportunities of CDPMs in MIS. Additionally, through user studies and pre-clinical studies, these prototypes demonstrate that this type of mechanism has several key advantages for surgical applications in which haptic feedback, safe automation or a high payload are required. These advantages, combined with the different access methods, demonstrate that CDPMs can have a key role in the advancement of MIS technology.Open Acces

Incipient slip detection and grasping automation for robotic surgery

Robotic minimally invasive surgery provides multiple improvements over traditional laparoscopic procedures, but one significant issue still encountered is their limited force control during the grasping and retraction of tissue, as the surgeon is separated from the instrument, and therefore denuded of their sense of touch and the applied forces. Prior solutions have largely looked towards haptic feedback to resolve this issue, but an alternative approach is to detect and monitor the occurrence of tissue slip events. This would allow the force to be automatically adjusted to prevent slip, minimising the clamp force used to maintain control, thus reducing the probability of tissue trauma. The aim of this work is to develop a method for the early detection and mitigation of tissue slip during robotic surgical manipulation tasks, helping to reduce tissue trauma and minimise tissue slip events. Initial investigations into literature, and evaluation of the slip mechanics when grasping soft, lubricated, deformable materials, indicated that small localised slips occur before the onset of macro slip. Two phenomena were identified in the slip mechanics investigation that could be employed to induce these slip in a measurable and repeatable manner. Firstly through using the tissue's deformable properties to create slip differentials between the front and rear of the grasper face, and secondly through using a curved surface to create a variation in the normal force, and thus frictional force, across the surface. Two instrumented grasper faces were developed, based on each of these phenomena, that were capable of monitoring the occurrence of localised tissue slip through monitoring the displacement of a series of independent movable islands that made up the grasper face. These were then demonstrated to be capable of automatically detecting slip events for a range of test conditions with tissue simulants, before being utilised to automatically control the grasping forces during a tissue retraction task. Both sensor systems provided similar levels of tissue control to one which utilised the maximum clamp force throughout the task, whilst applying lower forces during the early stages of retraction, reducing the probability of tissue damage. In addition the normal force based method, with the curved grasper face, was demonstrated to be effective for the early detection of slip when grasping porcine liver tissue, successfully detecting incipient slip in 77% of cases. This work provides a strong basis for further development of incipient slip sensing for surgical applications. It provides novel contributions in the understanding of slip mechanics of soft tissues, as well as presenting two separate novel sensing approaches for the automatic detection and mitigation of slip events, offering an opportunity for reducing the occurrence of tissue slip events whilst minimising tissue trauma, as well as surgeon fatigue

A Sensorized Instrument for Minimally Invasive Surgery for the Measurement of Forces during Training and Surgery: Development and Applications

The reduced access conditions present in Minimally Invasive Surgery (MIS) affect the feel of interaction forces between the instruments and the tissue being treated. This loss of haptic information compromises the safety of the procedure and must be overcome through training. Haptics in MIS is the subject of extensive research, focused on establishing force feedback mechanisms and developing appropriate sensors. This latter task is complicated by the need to place the sensors as close as possible to the instrument tip, as the measurement of forces outside of the patient\u27s body does not represent the true tool--tissue interaction. Many force sensors have been proposed, but none are yet available for surgery. The objectives of this thesis were to develop a set of instruments capable of measuring tool--tissue force information in MIS, and to evaluate the usefulness of force information during surgery and for training and skills assessment. To address these objectives, a set of laparoscopic instruments was developed that can measure instrument position and tool--tissue interaction forces in multiple degrees of freedom. Different design iterations and the work performed towards the development of a sterilizable instrument are presented. Several experiments were performed using these instruments to establish the usefulness of force information in surgery and training. The results showed that the combination of force and position information can be used in the development of realistic tissue models or haptic interfaces specifically designed for MIS. This information is also valuable in order to create tactile maps to assist in the identification of areas of different stiffness. The real-time measurement of forces allows visual force feedback to be presented to the surgeon. When applied to training scenarios, the results show that experience level correlates better with force-based metrics than those currently used in training simulators. The proposed metrics can be automatically computed, are completely objective, and measure important aspects of performance. The primary contribution of this thesis is the design and development of highly versatile instruments capable of measuring force and position during surgery. A second contribution establishes the importance and usefulness of force data during skills assessment, training and surgery