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Research Papers

A Sensorized Instrument for Skills Assessment and Training in Minimally Invasive Surgery

[+] Author and Article Information
A. L. Trejos

Canadian Surgical Technologies and Advanced Robotics, Lawson Health Research Institute, 339 Windermere Road; Department of Electrical and Computer Engineering, Faculty of Engineering, 1151 Richmond Street North; The University of Western Ontario, London, Ontario N6A 5A5, Canadaanaluisa.trejos@lhsc.on.ca

R. V. Patel

Canadian Surgical Technologies and Advanced Robotics, Lawson Health Research Institute, 339 Windermere Road; Department of Electrical and Computer Engineering, Faculty of Engineering, 1151 Richmond Street North; Department of Surgery, Schulich School of Medicine and Dentistry; The University of Western Ontario, London, Ontario N6A 5A5, Canadarvpatel@uwo.ca

M. D. Naish

Canadian Surgical Technologies and Advanced Robotics, Lawson Health Research Institute, 339 Windermere Road; Department of Mechanical and Materials Engineering, Department of Electrical and Computer Engineering, Faculty of Engineering, 1151 Richmond Street North; The University of Western Ontario, London, Ontario N6A 5A5, Canadanaish@eng.uwo.ca

A. C. Lyle

Canadian Surgical Technologies and Advanced Robotics, Lawson Health Research Institute, 339 Windermere Road, London, ON, N6A 5A5, Canadaandrewlyle@gmail.com

C. M. Schlachta

Canadian Surgical Technologies and Advanced Robotics, Lawson Health Research Institute, 339 Windermere Road, London, ON, N6A 5A5, Canada; Department of Surgery, Schulich School of Medicine and Dentistry; The University of Western Ontario, London, Ontario N6A 5A5, Canadachristopher.schlachta@lhsc.on.ca

J. Med. Devices 3(4), 041002 (Nov 19, 2009) (12 pages) doi:10.1115/1.4000421 History: Received April 11, 2008; Revised September 29, 2009; Published November 19, 2009; Online November 19, 2009

Minimally invasive surgery (MIS) is carried out using long, narrow instruments and significantly reduces trauma to the body, postoperative pain, and recovery time. Unfortunately, the restricted access conditions, limited instrument motion, and degraded sense of touch inherent in MIS result in new perceptual-motor relationships, which are unfamiliar to the surgeon and require training to overcome. Current training methods do not adequately address the needs of surgeons interested in acquiring these skills. Although a significant amount of research has been focused on the development of sensorized systems for surgery, there is still a need for a system that can be used in any training scenario (laparoscopic trainer, animal laboratories, or real surgery) for the purpose of skills assessment and training. A sensorized laparoscopic instrument has been designed that is capable of noninvasively measuring its interaction with tissue in the form of forces or torques acting in all five degrees-of-freedom (DOFs) available during MIS. Strain gauges attached to concentric shafts within the instrument allow the forces acting in different directions to be isolated. An electromagnetic tracking system is used for position tracking. Two prototypes of the sensorized instrument were constructed. Position calibration shows a maximum root mean square (RMS) error of 1.3 mm. The results of the force calibration show a maximum RMS error of 0.35 N for the actuation force, 0.07 N in the x and y directions, and 1.5Nmm for the torque calibration with good repeatability and low hysteresis. Axial measurements were significantly affected by drift, noise, and coupling leading to high errors in the readings. Novel sensorized instruments for skills assessment and training have been developed and a patent has been filed for the design and operation. The instruments measure forces and torques acting at the tip of the instrument corresponding to all five DOFs available during MIS and provide position feedback in six DOFs. The instruments are similar in shape, size, and weight to traditional laparoscopic instruments allowing them to be used in any training environment. Furthermore, replaceable tips and handles allow the instruments to be used for a variety of different tasks.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Instrument design with needle driver handle and tip (top) and with traditional handle and gripper attachment (bottom)

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Figure 2

Detail of the instrument design showing o-ring location for attachment of the outer shaft. The rotating wheel shown in the top image allows the user to rotate the distal end of the instrument in order to reorient the tip with respect to the handle.

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Figure 3

Coordinate frame associated with the instrument

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Figure 4

Type III full Wheatstone bridge (left) and the corresponding placement of gauges on the inner shaft (right)

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Figure 5

Type II half Wheatstone bridge (left); placement of the gauges measuring bending moment (gauges labeled A1 and B1 are wired together while A2 and B2 form the other half bridge) (center) and stress concentration caused by a 3 N force acting at the tip of the instrument (right)

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Figure 6

Type I quarter Wheatstone bridge (left); placement of the two-element rosettes measuring torsion and axial forces (each element is wired independently to a quarter bridge) (center) and stress concentration for a compression force of 5 N in the axial direction (right)

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Figure 7

Examples of interchangeable tips and handles that can be attached to the instrument

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Figure 8

Placement of gauges on the middle (a) and inner (b) shafts

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Figure 9

Cable wiring to allow the inner shaft to slide inside the middle shaft in order to accommodate the different tips

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Figure 10

Experimental setup

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Figure 11

Customized software interface including (a) real-time plots and (b) the calibration interface

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Figure 12

Instrument placement for calibration for: (a) x and y moments, (b) axial; and (c) torsion. (d) Shows a close up of the gimbal designed for the application of axial forces. Note that in these pictures, the stainless steel outer shaft was replaced by an ABS plastic shaft. Photo credit: Meg Woodhouse.

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Figure 13

(a) Calibration grid used for position assessment and (b) results of the position accuracy evaluation. The x’s show the actual grid position while the o’s represent the computed location based on the sensor measurement and calibration assessment.

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Figure 14

Signal drift observed in the five measured directions

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Figure 15

Sample image of the instrument compressing a spring for calibration validation

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Figure 16

Comparison of the measured forces by a force sensor and by the strain gauges on the sensorized instrument

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