Saurabh Dargar

Characterization of Force and Torque Interactions During a Simulated Transgastric Appendectomy Procedure

We have developed an instrumented endoscope grip handle equipped with a six-axis load cell and measured forces and torques during a simulated transgastric natural orifice translumenal endoscopic surgery appendectomy procedure performed in an EASIE-R ex vivo simulator. The data were collected from ten participating surgeons of varying degrees of expertise which was analyzed to compute a set of six force and torque parameters for each coordinate axis for each of the nine tasks of the appendectomy procedure. The mean push/pull force was found to be 3.64 N (σ = 3.54 N) in the push direction and the mean torque was 3.3 N · mm (σ = 38.6 N · mm) in the counterclockwise direction about the push/pull axis. Most interestingly, the force and torque data about the nondominant x and z axes showed a statistically significant difference (p <; 0.05) between the expert and novice groups for five of the nine tasks. These data may be useful in developing surgical platforms especially new haptic devices and simulation systems for emerging natural orifice procedures.

Haptic interactions during natural orifice translumenal endoscopic surgery

Natural orifice translumenal endoscopic surgery (NOTES) is viewed as an emerging surgical technique with significant potential to perform surgical interventions with minimal external scarring and reduced patient trauma. However, this technique uses an endoscope to perform surgical operations which require application of substantial forces and torques for insertion and maneuvering. We have, for the first time, developed an instrumented tool handle with a 6 axis load cell to measure the forces and torques applied during NOTES procedures and used it to make actual measurements during the performance of NOTES techniques by surgeons using an ex-vivo simulator. Data were collected for 10 subjects with varying experience levels at the annual SAGES meeting. We observed that the typical forces were about 10 N with peaks up to 25 N in the push/pull direction. A nominal torque of 50 N-mm with peaks up to 200 N-mm in the clockwise and counter-clockwise directions was observed about the push/pull axis. In comparison, the interaction forces in traditional laparoscopic surgery are in the range of 0-10 N. The data are useful not only in understanding the level of force and torque applied during actual NOTES procedures, but also in developing specifications for a custom haptic feedback system for a virtual reality-based NOTES simulator designed to train the next generation of NOTES surgeons.

Graphic and haptic simulation for transvaginal cholecystectomy training in NOTES

BACKGROUND Natural Orifice Transluminal Endoscopic Surgery (NOTES) provides an emerging surgical technique which usually needs a long learning curve for surgeons. Virtual reality (VR) medical simulators with vision and haptic feedback can usually offer an efficient and cost-effective alternative without risk to the traditional training approaches. Under this motivation, we developed the first virtual reality simulator for transvaginal cholecystectomy in NOTES (VTEST™). METHODS This VR-based surgical simulator aims to simulate the hybrid NOTES of cholecystectomy. We use a 6DOF haptic device and a tracking sensor to construct the core hardware component of simulator. For software, an innovative approach based on the inner-spheres is presented to deform the organs in real time. To handle the frequent collision between soft tissue and surgical instruments, an adaptive collision detection method based on GPU is designed and implemented. To give a realistic visual performance of gallbladder fat tissue removal by cautery hook, a multi-layer hexahedral model is presented to simulate the electric dissection of fat tissue. RESULTS From the experimental results, trainees can operate in real time with high degree of stability and fidelity. A preliminary study was also performed to evaluate the realism and the usefulness of this hybrid NOTES simulator. CONCLUSIONS This prototyped simulation system has been verified by surgeons through a pilot study. Some items of its visual performance and the utility were rated fairly high by the participants during testing. It exhibits the potential to improve the surgical skills of trainee and effectively shorten their learning curve.

Development of a Haptic Interface for Natural Orifice Translumenal Endoscopic Surgery Simulation

Natural orifice translumenal endoscopic surgery (NOTES) is a minimally invasive procedure, which utilizes the bodys natural orifices to gain access to the peritoneal cavity. The NOTES procedure is designed to minimize external scarring and patient trauma, however flexible endoscopy based pure NOTES procedures require critical scope handling skills. The delicate nature of the NOTES procedure requires extensive training. Thus, to improve access to training while reducing risk to patients, we have designed and developed the VTEST, a virtual reality NOTES simulator. As part of the simulator, a novel decoupled 2-DOF haptic device was developed to provide realistic force feedback to the user in training. A series of experiments were performed to determine the behavioral characteristics of the device. The device was found capable of rendering up to 5.62N and 0.190 Nm of continuous force and torque in the translational and rotational DOF, respectively. The device possesses 18.1 and 5.7 Hz of force bandwidth in the translational and rotational DOF, respectively. A feedforward friction compensator was also successfully implemented to minimize the negative impact of friction during the interaction with the device. In this work, we have presented the detailed development and evaluation of the haptic device for the VTEST.

Towards immersive virtual reality (iVR): a route to surgical expertise.

Surgery is characterized by complex tasks performed in stressful environments. To enhance patient safety and reduce errors, surgeons must be trained in environments that mimic the actual clinical setting. Rasmussen’s model of human behavior indicates that errors in surgical procedures may be skill-, rule-, or knowledge-based. While skill-based behavior and some rule-based behavior may be taught using box trainers and ex vivo or in vivo animal models, we posit that multimodal immersive virtual reality (iVR) that includes high-fidelity visual as well as other sensory feedback in a seamless fashion provides the only means of achieving true surgical expertise by addressing all three levels of human behavior. While the field of virtual reality is not new, realization of the goals of complete immersion is challenging and has been recognized as a Grand Challenge by the National Academy of Engineering. Recent technological advances in both interface and computational hardware have generated significant enthusiasm in this field. In this paper, we discuss convergence of some of these technologies and possible evolution of the field in the near term.

Ultrasound elastography reliably identifies altered mechanical properties of burned soft tissues

Although burn injury to the skin and subcutaneous tissues is common in both civilian and military scenarios, a significant knowledge gap exists in quantifying changes in tissue properties as a result of burns. In this study, we present a noninvasive technique based on ultrasound elastography which can reliably assess altered nonlinear mechanical properties of a burned tissue. In particular, ex vivo porcine skin tissues have been exposed to four different burn conditions: (i) 200°F for 10s, (ii) 200°F for 30s, (iii) 450°F for 10s, and (iv) 450°F for 30s. A custom-developed instrument including a robotically controlled ultrasound probe and force sensors has been used to compress the tissue samples to compute two parameters (C10 and C20) of a reduced second-order polynomial hyperelastic material model. The results indicate that while the linear model parameter (C10) does not show a statistically significant difference between the test conditions, the nonlinear model parameter (C20) reliably identifies three (ii-iv) of the four cases (p<0.05) when comparing burned with unburned tissues with a classification accuracy of 60-87%. Additionally, softening of the tissue is observed because of the change in structure of the collagen fibers. The ultrasound elastography-based technique has potential for application under in vivo conditions, which is left for future work.

Retraction notice to Graphic and haptic simulation for transvaginal cholecystectomy training in NOTES J. Biomed. Inform. 60 (2016) 410-421

http://dx.doi.org/10.1016/j.jbi.2016.08.013 DOI of original article: http://dx.doi.org/10.1016/j.jbi.2016.03.005 ⇑ Corresponding author at: State Key Laboratory of Virtual Reality Technology and Systems, Beihang University, Beijing, China. Tel.: +86 10 82316329; fax 82339909. Jun J. Pan a,b,⇑, Woojin Ahn , Saurabh Dargar , Tansel Halic , Bai C. Li , Ganesh Sankaranarayanan , Kurt Roberts , Steven Schwaitzberg , Suvranu De b

System characterization of a novel haptic interface for natural orifice translumenal endoscopic surgery simulation.

Natural orifice translumenal endoscopic surgery (NOTES) is a minimally invasive procedure, which utilizes the bodys natural orifices to gain access to the peritoneal cavity. The VTEST© is a virtual reality NOTES simulator developed at the CeMSIM at RPI to train surgeons in NOTES. A novel 2 DOF decoupled haptic device was designed and built for this simulator. The haptic device can render 5.62 N and 190.05 N-mm of continuous force and torque respectively. In this work we have evaluated the haptic interface and developed a model to accurately describe the system behavior, to further incorporate into an impedance type controller for realistic haptic rendering in the VTEST©.