UBC Theses and Dissertations

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UBC Theses and Dissertations

A clinical C-arm base-tracking system using computer vision for intraoperative guidance Haliburton, Luke


Mobile C-arm X-ray machines are commonly used for imaging during orthopaedic surgeries to visualize internal anatomy during procedures. However, there is evidence indicating that excess operating time and radiation exposure result from the use of scouting images to aid C-arm positioning during surgery. Additionally, C-arms are currently used primarily as a qualitative tool. Several techniques have been proposed to improve positioning, reduce radiation exposure, and increase quantitative utility, but they require accurate C-arm position tracking. There have been attempts by other research groups to develop C-arm tracking systems, but there are currently no solutions suitable for use in an operating room. The objective of this thesis is therefore to present the development and verification of a real-time C-arm base-tracking system called OPTIX (On-board Position Tracking for Intraoperative X-rays). The proposed tracking system uses a single floor-facing camera mounted to the base of a C-arm. A computer vision algorithm was developed that tracks motion relative to the operating room floor. This system is capable of relative motion tracking as well as absolute position recovery for previous positions. The accuracy of the system was evaluated on a real C-arm in a simulated operating room. The experimental results demonstrated that the relative tracking algorithm can measure C-arm translation with errors of less than 0.75% of the total distance travelled, and orientation with errors better than 5% of the cumulative rotation. With the incorporated loop closure step, OPTIX can be used to achieve C-arm repositioning with translation errors of less than 1.10±0.07 mm and rotation errors of less than 0.17 ±0.02°. These results are well within the desired system requirements of 5 mm and 3.1°. The system has shown promising results for use as a C-arm base-tracking system. The system has clinically acceptable accuracies and should lead to a reduced need for scouting images when re-obtaining a previous position. The base-tracking system can be integrated with a C-arm joint tracking system, or implemented on its own for steering guidance. When implemented in an operating room, OPTIX has the potential to lead to a reduction in operating time and harmful radiation exposure to surgical staff.

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