Psychophysic Evaluation of Kinesthetic and Haptic Information and Force Feedback for Minimally Invasive Surgery

Abstract

Endoscopic graspers are usually manipulated by a human. This situation raises the question regarding the psychophysical aspects of the Force Feedback endoscopic Grasper (FREG) performance. The experimental protocol was designed to examine the operator ability to rank a group of materials, with similar biomechanical characteristics of soft tissue, according to their stiffness using three tools: (i) the FREG in a force feedback bi-lateral mode (ii) a regular endoscopic grasper, commonly used in MIS, and (iii) touching the materials with the hand (with a latex glove) as traditionally done in open surgery. The same Babcock tool was used by the FREG and the regular grasper during the subjective experiment.

Ten test operators divided into two groups (surgeon group and control group) were asked to rank eight materials according to their stiffness using three tools. The surgeon group included experienced general surgeons specialized in minimally invasive surgery. The control group included engineers without any medical background. The two groups included subjects with the same gender (male) and similar average age.

The statistical null hypothesis (H0) was that all the tools (standard endoscopic grasper, FREG, and hand) are equal in their performance for ranking material stiffness. The index of performances was calculated as the Mean Squared Error (MSE) of the estimated ranking (ER) relative to the correct ranking (CR). For the six materials (n=6) used in the subjective experiment, the MSE value has a range of < 0, 11.66 >. When a test operator ranks the materials exactly according to their correct stiffness order the MSE has a value of 0. The upper boundary of MSE value of 11.6 can be achieved when the test operator ranks the material in the opposite manner. Two way analysis of variance (2D ANOVA) was used to analyze the differences between instruments within group - 3 levels (Regular endoscopic grasper, FREG, and hand) and between groups - 2 levels (surgeon group and control group).

The two-way ANOVA statistical test showed a significant difference between the performance obtained by the three tools. The best performance in ranking the materials according to their stiffness was achieved by using the hand (MSE=0.25), whereas the worst performance was obtained by the standard endoscopic grasper (MSE=3.15). The performance of the FREG (MSE=1.07) was between the previous two, and closer to the performance of the hand than the grasper. The analysis suggests that there is no significant difference between the two operator groups (Surgeons and Control) that were tested. From the results above, the null hypothesis (H0) may be rejected. There is a significant difference between the performances of the three tools in ranking the materials according to their stiffness.

Force Reflective Endoscopic Grasper (FREG)

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[122]
J. Rosen, B. Hannaford, M. MacFarlane, M. Sinanan, 'Force Controlled and Teleoperated Endoscopic Grasper for Minimally Invasive Surgery - Experimental Performance Evaluation,' IEEE Transactions on Biomedical Engineering, vol. 46, pp. 1212-1221, October 1999.