Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Mechanical and Materials Engineering

Supervisor

Ferreira, Louis M.

Abstract

Although the use of surgical robots in hospitals is growing every year, adoption rates are still low. Robots tend to be large and designed specifically for one operation. Tracking systems also take up space and are difficult to incorporate into the operating room. As a result, there is a gap in the surgical robot field for one that is small, versatile for several procedures, and has its own compact tracking system.

This work outlines the development of a new surgical robotic system designed for a variety of procedures along with a novel reaction load-based navigation system referred to as “force-space navigation”. The robot was first tested by performing ear reconstruction. Following high accuracy and fast results, a second larger, faster robot accomplished similar results in a nasal reconstruction test. This demonstrated the speed, accuracy, and versatility of this system.

Along with the ear reconstruction test, reaction loads were measured pre-operatively and during operation. Close load agreement showed promise for use as navigation. During the nose reconstruction tests, meshless finite element (FE) software was utilized to calculate pre-operative loads and compared them to measured loads during operation. The meshless FE loads were also used in navigation tests showing good accuracy. These results allowed for the elimination of the physical calibration process that is currently needed for force-space navigation where loads are pre-operatively measured.

The last major hurdle for force-space navigation is developing a methodology for transforming the loads. First, load transformation based on a material change was investigated. A system that utilized sampling points for curving fitting and interpolation was able to transform the loads. These transformed loads were then used for navigation resulting in low positional errors. Next, this transformation methodology was refined reducing the number of sample points needed and generalizing the transformation for both a material change and a position/orientation misalignment. The transformed loads yielded low position and orientation errors when utilized for navigation.

Collectively, this dissertation demonstrated a fast, compact, versatile, and highly accurate surgical robotic system with a more complete navigation system eliminating the need for calibration with the ability to make a load-based coordinate transformation.

Summary for Lay Audience

Surgical robots have the potential to reduce operating times and improve surgical outcomes. While the adoption of robots into hospitals is growing year over year, robots still face several challenges limiting their usage in operating rooms. Firstly, these robots tend to be designed for a single surgical operation, limiting their usefulness. Secondly, surgical robots tend to be very large, taking up a lot of valuable operating room space. Tracking systems, typically optical or electromagnetic tracking, are also required, which can be difficult to incorporate into an operating room. This dissertation explores the development and testing of a novel surgical robot and tracking system that addresses these challenges.

The robot was tested for its accuracy and versatility by performing ear and nose reconstruction procedures. Rib cartilage was carved by the robot into both an ear shape and nostril shape very accurately and faster than by hand by a surgeon. Next, the novel tracking system was analyzed. This tracking system was built onto the robot and uses flexible components that bend and twist as the robot moves transmitting unique loads that are measured. The loads were used as targets for the robot as it navigated, allowing it to “feel” its way around. Previously, target loads needed to be measured by moving the robot through the desired cutting path by visiting the known Cartesian positions. To eliminate this, computer simulations were used to estimate the loads the robot would need to navigate to complete the desired surgical outcome. Also, techniques were developed to transform the loads if the material of the flexible strips was changed and/or if the initial position/orientation of the robot was different than what was pre-operatively planned. Together, this work demonstrated a complete surgical system with a small, versatile robot and a compact, novel tracking system with the hope it can be incorporated more easily into an operating room and improve surgical outcomes.

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