Alastair Barrow

Design and development of a haptic dental training system: hapTEL

This paper presents a novel design of a virtual dental training system (hapTEL) using haptic technology. The system allows dental students to learn and practice procedures such as dental drilling, caries removal and cavity preparation for tooth restoration. This paper focuses on the hardware design, development and evaluation aspects in relation to the dental training and educational requirements. Detailed discussions on how the system offers dental students a natural operational position are documented. An innovative design of measuring and connecting the dental tools to the haptic device is also shown. Evaluation of the impact on teaching and learning is discussed.

Perceptual cues for orientation in a two finger haptic grasp task

Single-point interaction haptic devices do not provide the natural grasp and manipulations found in the real world, as afforded by multi-fingered haptics. The present study investigates a two-fingered grasp manipulation involving rotation with and without force feedback. There were three visual cue conditions: monocular, binocular and projective lighting. Performance metrics of time and positional accuracy were assessed. The results indicate that adding haptics to an object manipulation task increases the positional accuracy but slightly increases the overall time taken.

A smoothed particle hydrodynamics algorithm for haptic rendering of dental filling materials

Using haptic interfaces to assist the training of skills in the curriculum of undergraduate dentists provides a unique opportunity to advance rendering algorithms and engineering of haptic devices. In this paper we use the dental context to explore a rendering technique called smoothed particle hydrodynamics (SPH) as a potential method to train the insertion of filling material into a previously prepared (virtual) dental cavity. The paper also considers how problems of haptic rendering might be implemented on a Graphical Processing Unit (GPU) that operates in the haptics control loop. The filling simulation used 3000 particles to represent the cavity boundary and filling material, running at an average of 447Hz. Novel smoothing function in SPH was developed and its flexibility is presented.

Validation of NOViSE A Novel Natural Orifice Virtual Surgery Simulator

The goal of this study was to establish face, content, and construct validity of NOViSE—the first force-feedback enabled virtual reality (VR) simulator for natural orifice transluminal endoscopic surgery (NOTES). Fourteen surgeons and surgical trainees performed 3 simulated hybrid transgastric cholecystectomies using a flexible endoscope on NOViSE. Four of them were classified as “NOTES experts” who had independently performed 10 or more simulated or human NOTES procedures. Seven participants were classified as “Novices” and 3 as “Gastroenterologists” with no or minimal NOTES experience. A standardized 5-point Likert-type scale questionnaire was administered to assess the face and content validity. NOViSE showed good overall face and content validity. In 14 out of 15 statements pertaining to face validity (graphical appearance, endoscope and tissue behavior, overall realism), ≥50% of responses were “agree” or “strongly agree.” In terms of content validity, 85.7% of participants agreed or strongly agreed that NOViSE is a useful training tool for NOTES and 71.4% that they would recommend it to others. Construct validity was established by comparing a number of performance metrics such as task completion times, path lengths, applied forces, and so on. NOViSE demonstrated early signs of construct validity. Experts were faster and used a shorter endoscopic path length than novices in all but one task. The results indicate that NOViSE authentically recreates a transgastric hybrid cholecystectomy and sets promising foundations for the further development of a VR training curriculum for NOTES without compromising patient safety or requiring expensive animal facilities.

Thimble End Effector for Palpation Skills Training

Interaction with force feedback haptic devices is often non-intuitive, obtrusive and unrealistic, particularly for the simulation of palpation skills training where a thimble is commonly found as an end-effector. A user will typically use two hands to steady the device and push one or more thimbles onto their fingers. New designs of thimbles, responsible for fastening the end effector of a haptic device onto the finger of the user have been explored, but do not solve the issue of introducing elements that are not present in the task being simulated. We introduce a number of design techniques, with early evaluation results for improving the way users engage, maintain connection and then disengage with thimble-connected haptic interfaces. The designs of the thimbles presented in this paper include rings and different opening shapes, which aim at creating a vacuum effect, as well as a mechanical grip around the finger of the user in order to hold it. Thimble effectiveness, as a function of low impedance on insertion and high impedance on removal, was assessed through a study which highlighted that the relationship between thimble opening size and finger circumference is a critical factor. We present results about the impact of the size of the rings on the insertion and extraction force, followed by a reflection on an improved experimental protocol.

Multi-finger Grasps in a Dynamic Environment

Most current state-of-the-art haptic devices render only a single force, however almost all human grasps are characterised by multiple forces and torques applied by the fingers and palms of the hand to the object. In this chapter we will begin by considering the different types of grasp and then consider the physics of rigid objects that will be needed for correct haptic rendering. We then describe an algorithm to represent the forces associated with grasp in a natural manner. The power of the algorithm is that it considers only the capabilities of the haptic device and requires no model of the hand, thus applies to most practical grasp types. The technique is sufficiently general that it would also apply to multi-hand interactions, and hence to collaborative interactions where several people interact with the same rigid object. Key concepts in friction and rigid body dynamics are discussed and applied to the problem of rendering multiple forces to allow the person to choose their grasp on a virtual object and perceive the resulting movement via the forces in a natural way. The algorithm also generalises well to support computation of multi-body physics

A Novel Haptic Interface for Navigation in Large Volume Environments

Haptic interfaces can provide highly realistic interaction with objects within their workspace, but the task of interacting with objects over large areas or volumes is made difficult by the limits of interface travel. This paper details the development of a custom haptic interface for navigating a large virtual environment (a simulated supermarket), and investigation into different control methods which allow for haptic interaction over extremely large workspaces

NOViSE: a virtual natural orifice transluminal endoscopic surgery simulator

PurposeNatural orifice transluminal endoscopic surgery (NOTES) is a novel technique in minimally invasive surgery whereby a flexible endoscope is inserted via a natural orifice to gain access to the abdominal cavity, leaving no external scars. This innovative use of flexible endoscopy creates many new challenges and is associated with a steep learning curve for clinicians.MethodsWe developed NOViSE—the first force-feedback-enabled virtual reality simulator for NOTES training supporting a flexible endoscope. The haptic device is custom-built, and the behaviour of the virtual flexible endoscope is based on an established theoretical framework—the Cosserat theory of elastic rods.ResultsWe present the application of NOViSE to the simulation of a hybrid trans-gastric cholecystectomy procedure. Preliminary results of face, content and construct validation have previously shown that NOViSE delivers the required level of realism for training of endoscopic manipulation skills specific to NOTES.ConclusionsVR simulation of NOTES procedures can contribute to surgical training and improve the educational experience without putting patients at risk, raising ethical issues or requiring expensive animal or cadaver facilities. In the context of an experimental technique, NOViSE could potentially facilitate NOTES development and contribute to its wider use by keeping practitioners up to date with this novel surgical technique. NOViSE is a first prototype, and the initial results indicate that it provides promising foundations for further development.

Relax and Tighten—A Haptics-based Approach to Simulate Sphincter Tone Assessment

Digital Rectal Examination (DRE) is a physical examination performed by clinicians to diagnose anorectal and prostate abnormalities. Amongst these, sphincter tone assessment is a crucial task where a clinician asks the patient to relax or squeeze, whilst measuring its function by the amount of pressure felt on the examining finger. DRE is difficult to learn and current models fail to reproduce the dynamic function of anorectal abnormalities. We propose a haptics-based approach to incorporate sphincter tone into our current simulator by motor-controlled pulling and releasing of cables that are coiled around a silicone model of the sphincters. A range of healthy and abnormal sphincter tone cases can be modelled by controlling the motors symmetrically and asymmetrically.