M. S. Raghu Prasad

Bio: M. S. Raghu Prasad is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topic(s): Haptic technology & Fitts's law. The author has an hindex of 5, co-authored 6 publication(s) receiving 59 citation(s).

Objective Assessment of Laparoscopic Force and Psychomotor Skills in a Novel Virtual Reality-Based Haptic Simulator.

Abstract: Background Most of the commercially available virtual reality-based laparoscopic simulators do not effectively evaluate combined psychomotor and force-based laparoscopic skills. Consequently, the lack of training on these critical skills leads to intraoperative errors. Objectives To assess the effectiveness of the novel virtual reality-based simulator, this study analyzed the combined psychomotor (i.e., motion or movement) and force skills of residents and expert surgeons. The study also examined the effectiveness of real-time visual force feedback and tool motion during training. Design Bimanual fundamental (i.e., probing, pulling, sweeping, grasping, and twisting) and complex tasks (i.e., tissue dissection) were evaluated. In both tasks, visual feedback on applied force and tool motion were provided. The skills of the participants while performing the early tasks were assessed with and without visual feedback. Participants performed 5 repetitions of fundamental and complex tasks. Reaction force and instrument acceleration were used as metrics. Setting Surgical Gastroenterology, Government Stanley Medical College and Hospital; Institute of Surgical Gastroenterology, Madras Medical College and Rajiv Gandhi Government General Hospital. Participants Residents ( N = 25; postgraduates and surgeons with N = 25; surgeons with >4 and ≤10 years of laparoscopic surgery). Results Residents applied large forces compared with expert surgeons and performed abrupt tool movements (p Conclusions Modern day curriculum-based training should evaluate the skills of residents with robust force and psychomotor-based exercises for proficient laparoscopy. Visual feedback on force and motion during training has the potential to enhance the learning curve of residents.

Effects of laparoscopic instrument and finger on force perception: a first step towards laparoscopic force-skills training

Abstract: In laparoscopic surgery, no external feedback on the magnitude of the force exerted is available. Hence, surgeons and residents tend to exert excessive force, which leads to tissue trauma. Ability of surgeons and residents to perceive their own force output without external feedback is a critical factor in laparoscopic force-skills training. Additionally, existing methods of laparoscopic training do not effectively train residents and novices on force-skills. Hence, there is growing need for the development of force-based training curriculum. As a first step towards force-based laparoscopic skills training, this study analysed force perception difference between laparoscopic instrument and finger in contralateral bimanual passive probing task. The study compared the isometric force matching performance of novices, residents and surgeons with finger and laparoscopic instrument. Contralateral force matching paradigm was employed to analyse the force perception capability in terms of relative (accuracy), and constant errors in force matching. Force perception of experts was found to be better than novices and residents. Interestingly, laparoscopic instrument was more accurate in discriminating the forces than finger. The dominant hand attempted to match the forces accurately, whereas non-dominant hand (NH) overestimated the forces. Further, the NH of experts was found to be most accurate. Furthermore, excessive forces were applied at lower force levels and at very high force levels. Due to misperception of force, novices and residents applied excessive forces. However, experts had good control over force with both dominant and NHs. These findings suggest that force-based training curricula should not only have proprioception tasks, but should also include bimanual force-skills training exercises in order to improve force perception ability and hand skills of novices and residents. The results can be used as a performance metric in both box and virtual reality based force-skills training.

Force JND for Right Index Finger Using Contra Lateral Force Matching Paradigm

Abstract: The paper aims at deriving the Just Noticeable Difference (JND) for force magnitude recognition between left and right index finger of human hand The experiment involves establishment of an internal reference stimulus, using the left index fingers of the hand, by the subject, which is perceived and matched under contra-lateral force matching paradigm A combination of virtual environment and a force sensor was used to derive the just noticeable difference for index-finger force application Six voluntary healthy young adult subjects in the age group of 22–30 years were instructed to produce reference forces by left index finger and to reproduce the same amount of force by the right index finger, when the subjects were confident enough of matching same amount of force, the force values of the both the left and right index finger were recorded simultaneously for 5 s at 10 Hz Five different trials were conducted for different force levels ranging from 2 to 5 N The percentage real JND and absolute JND were derived for all the subjects It was found that the Force-JND obtained was approximately 10 % across all subjects Results also show that subjects tend to underestimate force at high force levels and overestimate at low force levels The results obtained can be used as basic building block for the calibration of virtual reality based minimally invasive surgery related tasks and force based virtual user interfaces ranging from touch pad to assistive tools

Comparison of Force Matching Performance in Conventional and Laparoscopic Force-Based Task

Abstract: Laparoscopic instruments have limited haptics feedback. Hence, novices tend to exert excessive force which leads to tissue trauma. In laparoscopic surgery, no external information is available on the magnitude of excessive force. Therefore, novices should be trained to accurately perceive their own force output. This study analyzed the force perception of 18 novices in the absence of external information, by comparing the isometric force matching performance of index finger (i.e. used in conventional procedures) in extended arm posture with that of laparoscopic instrument in a force-based probing task. The study also examined the effect of handedness on force perception. A contra-lateral force matching paradigm was employed to analyze the matching performance of the novice subjects. Interestingly, matching error was found to be lower for laparoscopic instrument. An effect of handedness was visible for laparoscopic instrument only. The dominant hand overestimated the forces of non-dominant hand. The result...

Modeling of Human Hand Force Based Tasks Using Fitts's Law

Abstract: Conventional Fitts’s model for human movement task finds a common application in modern day interactive computer systems and ergonomics design. According to Fitts’s law the time required to rapidly move to a target area is a function of the distance to the target and the size of the target. This paper describes experimental process for prediction of minimum movement time, in a force-variation based human performance task involving right index finger. In this study we have made an attempt to extend the applicability of the conventional Fitts’s model for a force based virtual movement task, without taking position into account and evaluate human performance metrics for such tasks. An experiment was conducted in which 6 healthy young adult subject’s in the age group of 22–30 years performed force based movement tasks. During each trial, subjects were asked to reach an initial force bar of given thickness W Newtons, corresponding to allowable tolerance. Once the subject’s had reached initial level, they were instructed to reach out the target force bar of same thickness W as quickly as possible and bring it back to the initial force level bar, thereby completing 1 iteration. Time required for 10 such iteration was noted for each subject. The results from the experiment show that the relationship between movement time and index of difficulty for force tasks are well described by Fitts’s law in visual guided, force-based virtual movement task.

What is a device bend gesture really good for

Abstract: Device deformation allows new types of gestures to be used in interaction. We identify that the gesture/use-case pairings proposed by interaction designers are often driven by factors relating improved tangibility, spatial directionality and strong metaphorical bonds. With this starting point, we argue that some of the designs may not make use of the full potential of deformation gestures as continuous, bipolar input techniques. In two user studies, we revisited the basics of deformation input by taking a new systematic look at the question of matching gestures with use cases. We observed comparable levels of UX when using bend input in different continuous bipolar interactions, irrespective of the choice of tangibility, directionality and metaphor. We concluded that device bend gestures use their full potential when used to control continuous bipolar parameters, and when quick reactions are needed. From our studies, we also identify relative strengths of absolute and relative mappings, and report a Fitts' law study for device bending input.

Haptic Feedback, Force Feedback, and Force-Sensing in Simulation Training for Laparoscopy: A Systematic Overview

Abstract: OBJECTIVES To provide a systematic overview of the literature assessing the value of haptic and force feedback in current simulators teaching laparoscopic surgical skills. DATA SOURCES The databases of Pubmed, Cochrane, Embase, Web of Science, and Google Scholar were searched to retrieve relevant studies published until January 31st, 2017. The search included laparoscopic surgery, simulation, and haptic or force feedback and all relevant synonyms. METHODS Duplicates were removed, and titles and abstracts screened. The remaining articles were subsequently screened full text and included in this review if they followed the inclusion criteria. A total of 2 types of feedback have been analyzed and will be discussed separately: haptic- and force feedback. RESULTS A total of 4023 articles were found, of which 87 could be used in this review. A descriptive analysis of the data is provided. Results of the added value of haptic interface devices in virtual reality are variable. Haptic feedback is most important for more complex tasks. The interface devices do not require the highest level of fidelity. Haptic feedback leads to a shorter learning curve with a steadier upward trend. Concerning force feedback, force parameters are measured through force sensing systems in the instrument and/or the environment. These parameters, especially in combination with motion parameters, provide box trainers with an objective evaluation of laparoscopic skills. Feedback of force-use both real time and postpractice has been shown to improve training. CONCLUSIONS Haptic feedback is added to virtual reality simulators to increase the fidelity and thereby improve training effect. Variable results have been found from adding haptic feedback. It is most important for more complex tasks, but results in only minor improvements for novice surgeons. Force parameters and force feedback in box trainers have been shown to improve training results.

Objective Assessment of Laparoscopic Force and Psychomotor Skills in a Novel Virtual Reality-Based Haptic Simulator.

Abstract: Background Most of the commercially available virtual reality-based laparoscopic simulators do not effectively evaluate combined psychomotor and force-based laparoscopic skills. Consequently, the lack of training on these critical skills leads to intraoperative errors. Objectives To assess the effectiveness of the novel virtual reality-based simulator, this study analyzed the combined psychomotor (i.e., motion or movement) and force skills of residents and expert surgeons. The study also examined the effectiveness of real-time visual force feedback and tool motion during training. Design Bimanual fundamental (i.e., probing, pulling, sweeping, grasping, and twisting) and complex tasks (i.e., tissue dissection) were evaluated. In both tasks, visual feedback on applied force and tool motion were provided. The skills of the participants while performing the early tasks were assessed with and without visual feedback. Participants performed 5 repetitions of fundamental and complex tasks. Reaction force and instrument acceleration were used as metrics. Setting Surgical Gastroenterology, Government Stanley Medical College and Hospital; Institute of Surgical Gastroenterology, Madras Medical College and Rajiv Gandhi Government General Hospital. Participants Residents ( N = 25; postgraduates and surgeons with N = 25; surgeons with >4 and ≤10 years of laparoscopic surgery). Results Residents applied large forces compared with expert surgeons and performed abrupt tool movements (p Conclusions Modern day curriculum-based training should evaluate the skills of residents with robust force and psychomotor-based exercises for proficient laparoscopy. Visual feedback on force and motion during training has the potential to enhance the learning curve of residents.

Development of a Laparoscopic Box Trainer Based on Open Source Hardware and Artificial Intelligence for Objective Assessment of Surgical Psychomotor Skills

Abstract: Background. A trainer for online laparoscopic surgical skills assessment based on the performance of experts and nonexperts is presented. The system uses computer vision, augmented reality, and art...

The effects of laparoscopic graspers with enhanced haptic feedback on applied forces: a randomized comparison with conventional graspers.

Abstract: Haptic feedback, which enables surgeons to perceive information on interaction forces between instrument and tissue, is deficient in laparoscopic surgery. This information, however, is essential for accurate tissue manipulation and recognition of tissue consistencies. To this end, a laparoscopic grasper with enhanced haptic feedback has been developed: the force reflecting operation instrument (FROI). This study tested the effects of enhanced haptic feedback on force control, tissue consistency interpretation, and the associated surgeons’ level of confidence through a randomized controlled crossover experiment. A randomized three-period crossover trial was conducted, in which seven surgical residents and 13 medical students participated. The setup involved a box trainer in which slices of porcine organs (lung, small intestine, or liver) were presented. Participants performed three series of blinded palpation tasks involving three different graspers: the conventional grasper, the FROI with enhanced haptic feedback activated, and the FROI with enhanced haptic feedback deactivated. In each series, nine pairs of organ tissues were palpated to compare consistencies. The orders of presenting both instruments and tissues were randomized. The force applied during tissue palpation significantly decreased, by a mean factor of 3.1 with enhanced haptic feedback. Tissue consistency interpretation was significantly improved with more correct assessments and participants answered with significantly more confidence when enhanced haptic feedback was available. The availability of enhanced haptic feedback enabled participants to operate with significantly reduced interaction force between instrument and tissues. This observation is expected to have multiple important clinical implications, such as less tissue damage, fewer complications, shorter operation times, and improved ergonomics.