A Surgical Training Module for Angled Laparoscopic Lens Navigation.

Randy Haluck, M.D.1, Roger Webster, Ph.D.2, Betty Mohler 2,

1Department of Minimally Invasive Surgery
Penn State University College of Medicine
Milton S. Hershey Medical Center
Hershey, PA USA 17033

2Department of Computer Science

H. Justin Roddy Science and Technology Complex
D&E Communications Wing
Millersville University
Millersville, PA. USA 17551

 

Abstract. This virtual reality trainer was designed to familiarize students and surgeons with surgical navigation using an angled laparoscopic lens and camera system. Previous laparoscopic trainers have been devoted to task or procedure training. Our system is exclusively devoted to laparoscope manipulation and navigation. The intent is to provide a method of instruction for efficient manipulation of a laparoscope during minimally invasive surgery.  This simulator may provide for improved navigation in the operating room and become a useful tool for residents and practicing surgeons.
 

1. Introduction.

All surgical procedures require some degree of visual navigation within an operative field.  Altered visuospatial skills however, are required for navigation with a laparoscopic lens within the complex three-dimensional environment of a body cavity [1].  In traditional open surgery, our eyes track and focus without higher cognitive input. In video-endoscopic or laparoscopic surgery, the vision; of the operation must be directed manually, clearly requiring a different set of skills and possibly higher cognitive function. At least theoretically, training with this system outside of the operating room would lead to more efficient use in the operating room.

Most commercially available angled laparoscopic lens systems consist of a long slender lens that allows change in direction of view through rotation of the lens itself. This is coupled to an independently rotating video camera. The camera and lens system must be simultaneously rotated, or not rotated, in order to achieve the desired angle of view while maintaining correct right-side-up orientation. The function, orientation, and manipulation of an angled laparoscopic lens in combination with an independently rotating camera system may not be intuitive.

Several simulators have been developed for training endoscopic surgery, but most focus on task or part-task trainers, designed to provide instruction in the motor component required for laparoscopic surgery [2-7].  These simulators can be used for preoperative visual inspection of the patient's anatomy, procedure rehearsals, and location of tumors using distances to landmarks or vessel diameters. The applications of these simulators include guiding a trans-bronchialneedle biopsy, guiding stent placement, monitoring the observed organ, and catheter insertion into vasculature.  One such computer-based trainer is the MIST VR, which was designed to train in the special hand-eye coordinated movements that are basic to laparoscopic surgery[8]. Our simulator is concerned with the visuospatial issues of manipulating a laparoscope during advanced laparoscopic surgery, where an angled lens system may be required.  To date, no simulator has been developed for instruction in laparoscopic navigation.

Often, the duty of directing the eyes of the operation or driving the camera is delegated to an assistant or a junior member of the team while the operating surgeon performs the procedure.  In this arrangement, the camera / lens operator must serve as the eyes for the entire surgical team.  A facile understanding of the function, operation, and manipulation of the laparoscope is essential.  While stationary and robotic camera-positioning devices are available, the surgeon must still have a fluid understanding of the manipulation of the laparoscope. A computer-based simulator designed to replicate the maneuvers necessary and provide instruction in angled laparoscopic lens driving in a controlled setting would theoretically provide for a better understanding of the camera lens system and more efficient navigation in the operating room.

The purpose of this project was to develop a computer-based training system that would provide instruction to relative novices at laparoscopic navigation using an angled lens.  The software was designed to challenge the participants so that a wide variety of angular and rotational maneuvers would be required to identify visual targets. Additionally, the system was designed to require the learner to maintain right-side-up orientation while finding the targets.  A method of scoring speed, efficiency, and errors was to be included in the trainer for assessment of skill, improvement, and skill acquisition.

2. Hardware Platform.

The Virtual Laparoscopic Interface (VLI) (Immersion Corporation, San Jose, CA), was utilized as the input device as it provides a fast, effective means of tracking simulated laparoscopic motion.  The VLI is a human computer interface tool designed for virtual reality (VR) simulations of laparoscopic and endoscopic surgical procedures. The frame unit acts as a sensored trocar that is connected via a serial port on a Windows  workstation with dual Pentium processors and OpenGL graphics.  Different surgical tool handles can be attached to the sensory unit.  The VLI tracks the motion of a pair of laparoscopic surgical instruments, each moving in 5 degrees of freedom.  The VLI system provides an effective means of tracking laparoscopic and endoscopic surgical procedures.

Figure 1. Dr. Randy Haluck at the endotower laparoscopic surgical simulator.

3. Storyboard, Modeling and Software.

The storyboard for the laparoscopic surgical training session entails identifying randomly placed arrows in what we call the "endotower". The endotower is 3D block tower with holes drilled out within the various arms of the tower. In the simulator colored 3D arrows are randomly placed inside the cylindrical cutouts. Due to the 3D nature of the endotower and the cylindrical cutouts, identifying all the arrows entails manipulating the laparoscope to many different and challenging orientations and positions, thereby testing the dexterity and skill efficiency of the user. A timer keeps track of how long it takes the user to correctly identify each of the arrows.

To operate the simulator, the practicing surgeon holds the laparoscopic camera, which simulates the angled lens laparoscope. In the virtual world, the user's viewpoint is placed at the tip of the laparoscopic tool. The user manipulates the laparoscope and then steps on a foot pedal which cycles through an onscreen list of arrow colors and orientations (see figure 2). The user holds the foot pedal down to enable the software check to see if the answer is correct. The user's score goes up for each arrow correctly identified. Also, any collision with the 3D endotower object causes the scope to become fuzzy with 'red out', simulating touching the scope to an organ (see figure 4). This causes the user's score to go down. The scoring mechanism measures and tracks the performance of the user and is displayed on screen during the training session. The scoring mechanism keeps track of: the amount of time it took to correctly identify the color and orientation of each arrow, the number of times the users dirties  the camera lens (hits the endotower causing red-out), and the rotational efficiency. It also records the amount of time to complete the entire training procedure. A numeric score is displayed for the user during the simulation.

The three dimensional (3D) models of the virtual laparoscopic tool and endotower model were built in 3D Studio Max and are stored as 3ds files. These models are loaded into the graphics simulation. The graphics software modules make calls to OpenGL calls. Another software module records the motions of the user. This is accomplished by continuously recording the positions and orientation of the endoscope and the lens rotations. Thus, 3D graphics are used to replay the technique, showing the medical student what he/she did during the training session. The replay can be done either from the laparoscopic viewpoint or from a bystander viewpoint. This can help the user see what positions and orientations were used during the training session.


 Figure 2. The endoscopic surgical training session entails identifying the randomly placed arrows inside the "endotower".

Figure 3. Close up of  endoscope looking into the holes of the endotower.

Figure 4. If the user touches the endotower with the laparoscope, redout occurs simulating smearing the lens with blood.

4. Conclusion.

This paper has described the development of a surgical simulator designed to teach the visuospatial skills required to navigate with an angled laparoscopic lens and camera system. Our system is exclusively devoted to laparoscope manipulation and navigation. The intent is to provide a method to learn how to efficiently manipulate a laparoscope during minimally invasive surgery by measuring surgical skills in a simulator. Initial work and results with the visuospatial laparoscopic surgical simulator are encouraging. Actual laparoscopic instruments are held by the practicing surgeon (the VLI tools) as the viewpoint of the camera lens is displayed and updated in real-time.  The scoring mechanism measures and tracks the performance of the user and is displayed on screen during the training session. This mechanism keeps track of: the amount of time it took to correctly identify the orientation of each arrow, the number of times the users dirties the camera lens  (hits the endotower causing red-out), and rotational efficiency. It also records the amount of time to complete the entire training procedure. A numeric score is displayed for the user during the simulation. Ongoing development is focused upon providing users more feedback and adding functions to output and analyze motion metrics. This may provide for more efficient navigation in the operating room as well as a useful tool in the education of medical students.

5. Future Work.

This software-training module may also be able to measure the skills of expert surgeons against novice surgeons in endoscopic surgery by analyzing various motion metrics captured by the simulator.


Figure 5. Betty Mohler - M.U. computer science student and software developer.

Acknowledgments.

This project was funded, in part, by the National Science Foundation under grant numbers EIA-00116616, DUE 9950742 and DUE 9651237, a Penn State College of Medicine Department of Surgery Feasibility Grant, the Eberly Medical Research Innovation Fund, the Millersville University Neimeyer-Hodgson Grants Program, and by the Faculty Grants Committee of Millersville University.

References/Literature.

[1] Medina M.  Image rotation and reversal major obstacles in learning intracorporeal suturing and knot-tying.  J Soc Laparoendosc Surg 1997;1:331-6.

[2] Morten Bro-Nielsen, J. Tasto, R. Cunningham, G. Merril, "PREOP Endoscopic Simulator: A PC-Based Immersive Training System for Bronchoscopy", Medicine Meets Virtual Reality 7, San Francisco,CA, January 20-23,1999,  IOS Press, pps. 76-82.

[3] Markus Kukuk, B. Geiger, "Registration of real and virtual endoscopy - a model and image based approach", Medicine Meets Virtual Reality 2000, Newport Beach, CA, January 20-24,2000, IOS Press, pps. 168-174.

[4] L.M. Auer,  "Virtual endoscopy for planning and simulation of minimally invasive neurosurgery", In CVRMed-MRCAS '97, Lecture Notes in Computer Science - 1205, pps. 315-318, March 1997.

[5] Joseph Tasto, K. Verstreken, J. M.Brown, J. Bauer, "PreOp Endoscopy Simulator: From Bronchoscopy to Ureteroscopy" , Medicine Meets Virtual Reality 2000, Newport Beach, CA, January 20-24,2000, IOS Press, pps. 344-349.

[6] D.P. Jang, M. Han, S. Kim, "Virtual Endoscopy using Surface Rendering and Perspective Volume Rendering", Medicine Meets Virtual Reality 7, San Francisco, CA, January 20-23,1999, IOS Press, pps. 161-166.

[7] C. Baur, D. Guzzoni, O. Georg, "VIRGY: A Virtual Reality and Force Feedback Based  Endoscopic Surgery Simulator" ,Medicine Meets Virtual Reality 6, San Diego, CA, January 28-31,1998,  IOS Press, pps. 110-116. 

[8] Christopher Sutton, R. McCloy, A. Middlebrook, P. Chater, M. Wilson, R. Stone, "MIST - A Laparoscopic Surgery Procedures Trainer and Evaluator", Medicine Meets Virtual Reality 1997, IOS Press, 1997, pps. 598-607.

 

[9] "Virtual Laparoscopic Interface User's Guide and Programming Reference", Rev. 1.0,  Immersion Inc., San Jose, CA., Dec. 1994.

Other information:

Video1.avi

 

**NOTE: Verefi Technologies Inc now owns this software and its Intellectual Property.

EndoTower™ is a commercially available product, additional Information can be found at the Verefi website:  http://www.verefi.com/

 

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All rights reserved
Millersville University
Last modified 02-20-2003

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