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UBC Theses and Dissertations

Feasibility study of a moving hand support for surgery on the beating heart Trejos, Ana Luisa

Abstract

A method for performing coronary bypass surgery on the beating heart is proposed, and entails the use of a heart-tracking support to move the hands of the surgeon in synchrony with the heart motion. This method eliminates the damaging effects associated with stopping or stabilizing the heart, while preserving the surgeon's dexterity and accuracy. First, a feasibility study was performed in order to compare the accuracy attained and the completion time required to perform accurate tasks on stable and moving targets, both with and without a motion tracking support. The results demonstrate that the negative effects of the target motion, namely, decreased accuracy and increased task completion time, are considerably reduced with the use of the support. The use of both monocular and stereo vision systems that provide a stable view of the work space was shown to limit the increase in task completion time; however, the accuracy was not improved due to the low resolution of the vision systems used. A solution to the design of the moving hand support consists of a three degree of freedom mechanism with prismatic joints. For this mechanism to accurately track the heart, it is necessary to measure the motion of the surgical area in real-time and to generate a suitable control strategy. After comparing several sensors that could be used to measure the heart motion, a mechanical sensor was designed and built. Despite the measurement error present in this particular prototype, it is believed that the design features of the sensor make it a suitable solution to the heart tracking problem. In order to address the problem of motion control, the moving support system was simulated using SIMULINK® and implemented on an experimental setup with PID and computed torque control. Furthermore, an additional control strategy is proposed that facilitates tracking of quasiperiodic, quantized inputs. Results show that it is possible for the mechanism to accurately follow the trajectory of the heart surface, since the maximum tracking error is approximately 0.15 mm.

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