Ravikiran B. Singapogu

Salient haptic skills trainer: initial validation of a novel simulator for training force-based laparoscopic surgical skills.

BackgroundThere is an increasing need for efficient training simulators to teach advanced laparoscopic skills beyond those imparted by a box trainer. In particular, force-based or haptic skills must be addressed in simulators, especially because a large percentage of surgical errors are caused by the over-application of force. In this work, the efficacy of a novel, salient haptic skills simulator is tested as a training tool for force-based laparoscopic skills.MethodsThirty novices with no previous laparoscopic experience trained on the simulator using a pre-test–feedback–post-test experiment model. Ten participants were randomly assigned to each of the three salient haptic skills—grasping, probing, and sweeping—on the simulator. Performance was assessed by comparing force performance metrics before and after training on the simulator.ResultsData analysis indicated that absolute error decreased significantly for all three salient skills after training. Participants also generally decreased applied forces after training, especially at lower force levels. Overall, standard deviations also decreased after training, suggesting that participants improved their variability of applied forces.ConclusionsThe novel, salient haptic skills simulator improved the precision and accuracy of participants when applying forces with the simulator. These results suggest that the simulator may be a viable tool for laparoscopic force skill training. However, further work must be undertaken to establish full validity. Nevertheless, this work presents important results toward addressing simulator-based force-skills training specifically and surgical skills training in general.

Objective Differentiation of Force-Based Laparoscopic Skills Using a Novel Haptic Simulator

BACKGROUNDnThere is a growing need for effective surgical simulators to train the novice resident with a core skill set that can be later used in advanced operating room training. The most common simulator-based laparoscopic skills curriculum, the Fundamentals of Laparoscopic Skills (FLS), has been demonstrated to effectively teach basic surgical skills; however, a key deficiency in current surgical simulators is lack of validated training for force-based or haptic skills. In this study, a novel haptic simulator was examined for construct validity by determining its ability to differentiate between the force skills of surgeons and novices.nnnMETHODSnA total of 34 participants enrolled in the study and were divided into two groups: novices, with no previous surgical experience and surgeons, with some level of surgical experience (including upper level residents and attendings). All participants performed a force-based task using grasping, probing, or sweeping motions with laparoscopic tools on the simulator. In the first session, participants were given 3 trials to learn specific forces associated with locations on a graphic; after this, they were asked to reproduce forces at each of the locations in random order. A force-based metric (score) was used to record performance.nnnRESULTSnOn probing and grasping tasks, novices applied significantly greater overall forces than surgeons. When analyzed by force levels, novices applied greater forces on the probing task at lower and mid-range forces, for grasping at low-range forces ranges and, for sweeping at high-range forces.nnnCONCLUSIONSnThe haptic simulator successfully differentiated between novice and surgeon force skill level at specific ranges for all 3 salient haptic tasks, establishing initial construct validity of the haptic simulator. Based on these results, force-based simulator metrics may be used to objectively measure haptic skill level and potentially train residents. Haptic simulator development should focus on the 3 salient haptic skills (grasping, probing, and sweeping) where precise force application is necessary for successful task outcomes.

Haptic virtual manipulatives for enhancing K-12 special education

The novel idea of haptic virtual manipulatives as learning aids for learning disabled K-12 students will be presented. The need for innovative, specialized tools to enhance learning, especially for students with learning disabilities, is presented as motivation for this work. We discuss virtual manipulatives for math education and the proposition that it would be beneficial to augment these manipulatives with a sense of touch through a haptic interface. The design of haptic virtual manipulatives is discussed as well as suitable haptic interfaces. A discussion of future directions of this research concludes the presentation.

Perceptually salient haptic rendering for enhancing kinesthetic perception in virtual environments

Kinesthetic or dynamic touch involves the use of muscle sensitivity to perceive mechanical properties of objects that are gripped in the hand and wielded in space. Many previous studies with real objects have investigated the mechanical properties that underlie human haptic perception. Few virtual environments, however, have systematically incorporated the relevant mechanical parameters underlying kinesthetic perception. In this study, the ability of a haptic device to render kinesthetic information regarding the inertial properties of virtual objects was tested. Results suggest that users were able to perceive length of rendered virtual objects via the haptic device. Further, users can be trained using the haptic device to increase sensitivity to specific mechanical parameters (like inertia) that are perceptually salient in perceiving properties of rendered objects. The primary implication of this finding is that rendering kinesthetic parameters and employing feedback in a systematic manner may increase the realism of virtual environments and also improve haptic perception.

Simulator-Based Assessment of Haptic Surgical Skill A Comparative Study

The aim of this study was to examine if the forces applied by users of a haptic simulator could be used to distinguish expert surgeons from novices. Seven surgeons with significant operating room expertise and 9 novices with no surgical experience participated in this study. The experimental task comprised exploring 4 virtual materials with the haptic device and learning the precise forces required to compress the materials to various depths. The virtual materials differed in their stiffness and force-displacement profiles. The results revealed that for nonlinear virtual materials, surgeons applied significantly greater magnitudes of force than novices. Furthermore, for the softer nonlinear and linear materials, surgeons were significantly more accurate in reproducing forces than novices. The results of this study suggest that the magnitudes of force measured using haptic simulators may be used to objectively differentiate experts’ haptic skill from that of novices. This knowledge can inform the design of virtual reality surgical simulators and lead to the future incorporation of haptic skills training in medical school curricula.

Surgeon’s Perception of Soft Tissue Constraints and Distance-to-Break in a Simulated Minimally Invasive Surgery Task

Accurately perceiving biomechanical properties of tissues is imperative for minimizing tissue trauma and preventable injuries in minimally invasive surgery (MIS). Research has demonstrated that novice observers are able to perceive and use the higher-order mechanical information in compliant, deformable materials which denotes the point at which the material will fail, or break, known as Distance -to-Break (DTB). The present study explored the effect of experience on the perception of DTB. Specifically, this study investigated whether surgeons are able to perceive and utilize DTB in compliant tissue materials more precisely than novices. Using a simulated probing task, results demonstrated that surgeons were more sensitive to DTB, were more accurate at estimating the point at which materials would fail, and were more accurate at applying force onto materials without breaking them. Findings underscore the importance of haptic invariants such as DTB in surgical tasks and the efficacy of using simulators to train haptic skills.

A Five DOF haptic rendering algorithm using multiple contact points

With the proliferation of haptic devices, there has been significant research toward realistic haptic rendering of virtual environments. Currently, the majority of haptic devices provide only three degrees-of freedom (3 DOF), but 5 and 6 DOF devices are becoming more common. This paper presents a method of using existing 3 DOF rendering techniques to produce forces for a 5 or 6 DOF device when true 6 DOF rendering is unavailable. Point-force 3 DOF rendering that is most commonly used in commercial haptic applications is simple and fast for basic haptic rendering; however, this creates unrealistic haptic effects when an avatar other than a point is considered. As a solution, a 6 DOF force and torque algorithm is presented based on multiple contact points. Using the multi-point torque rendering approach, forces are rendered in three linear dimensions using existing 3 DOF algorithms, and up to three additional torque degrees-of freedom are calculated based on the forces on multiple points. This capability enhances haptic realism without modifying the legacy rendering. Finally, this algorithm is demonstrated using a 5 DOF haptic interface. The results from test observations suggest that the 5 DOF rendering algorithm functions as expected.

Towards quantifying surgical suturing skill with force, motion and image sensor data

This work contributes towards the vision of a suture platform that is able to objectively quantify suturing skill by integrating data from multiple sensing modalities. A first step towards such a platform is the synchronization of data from multiple sensor streams and perhaps even multiple systems. We present the design of a novel suture platform with force and motion sensors as well as video capture for recording hand motion. Software methods to synchronize these data, as well as a Graphical User Interface (GUI) that extracts suture cycle data is created. Results indicate that sensor data was successfully synchronized using time-offset calculation. Sensor data was extracted for individual suture cycles for all participants including average force, peak force, average acceleration, peak acceleration and time to complete suture. Our results indicate the viability of the system to synchronize sensor data, enabling its use to provide objective feedback to trainees regarding their suturing skills.

Development of computer vision algorithm towards assessment of suturing skill

In this paper, we present a computer vision algorithm to extract key information pertinent to assessing surgical suturing. This algorithm uses an instrumented platform designed to quantify suturing skill. As subjects performed suturing on the platform, the vision algorithm computes the time and the location of suture needles entry and exit, stitch length, needle trace, and hesitation time, which were identified as potential metrics to assess suturing skill. Preliminary experimental data from a study with 14 subjects with minimal suturing experience are presented. The results demonstrate that the algorithm is feasible for use in quantifying suturing expertise.

Perceiving the lengths of real and virtual objects using kinesthetic touch

Humans use their kinesthetic haptic sense for a variety of day-to-day tasks. While manipulating objects using this sensory channel, which corresponds to signals arising in the muscles and joints, it has been shown that humans can perceive several characteristics of the objects that are being held or wielded. For example, the length of a baseball bat can be estimated without but the aid of vision by wielding it. There have been over a hundred studies that have sought to understand the perceptual basis of these judgments. Seminal work conducted by [7] and [8] has suggested that the haptic perception of length during wielding is related to the Inertia tensor of the wielded object. Studies have shown high correlations between the inertia tensor and various haptic properties like length [1], height [9, 10], orientation of the object [3] and the position of the hand grasp [4, 5]. All of these studies have shown the central role of the inertia tensor as the perceptual basis for making haptic judgments of object properties.