Restriction lift date: 2036-12-31
Intelligent electronics design in magnetic tracking for image-guided surgery
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Date
2025
Authors
Crowley, Daragh
Journal Title
Journal ISSN
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Publisher
University College Cork
Published Version
Abstract
This thesis presents the design, development, and evaluation of intelligent electronic systems for electromagnetic tracking in image-guided surgery, validated through laboratory experiments, a pre-clinical study, and a clinical investigation. Electromagnetic tracking provides a safe, accurate, and minimally invasive method of navigating without line-of-sight inside the body. The work addresses long-standing challenges in electromagnetic tracking, including wireless sensor design, system distortion, scalable tracking volumes, and integration into clinical workflows.
The thesis begins with a comprehensive literature review of surgical navigation technologies, with a focus on electromagnetic tracking and the state of the art in wireless tracking. This provides the foundation for a series of technical and translational contributions. While much of the work in this thesis is targeted towards cardiothoracic interventions, the technologies developed apply to a wide range of surgical navigation requirements.
A clinical study was carried out to assess the accuracy and feasibility of using six electromagnetic tracking sensors on the patient's chest to accomplish dynamic CT-to-body registration during electromagnetic navigation bronchoscopy. The study involved eleven patients undergoing routine bronchoscopy and showed dynamic registration errors ranging from 11 to 34 mm, compared to pre-procedure CT imaging. The challenges encountered during the clinical study provided rationale for the subsequent work in this thesis.
While effective for registration purposes, the presence of multiple wired sensors on the patient was found to complicate the operating area and obstruct movement around the patient. In direct response to this problem, a range of wireless electromagnetic tracking sensors were developed. Both frequency-modulated radio and Bluetooth low-energy were investigated to develop these sensors. Bluetooth low-energy was shown to be more suitable, with the wireless sensors achieving accuracy comparable to existing wired sensors with positional errors on the order of one millimetre, battery life of at least one hour, and reliable system performance. Readiness for clinical use was demonstrated in extensive laboratory testing as well as a pre-clinical evaluation in a porcine lung model to show their ability to track under realistic clinical conditions.
To address the challenge of conductive metal distorting the magnetic field, the effect of field frequency was examined in theory, simulation, and experimentation. A dual-frequency band tracking system was prototyped using the open-source Anser EMT platform and achieved a 46% error reduction in the presence of distortion caused by a large piece of aluminium, while increasing the tracking update rate from 5 Hz to 100 Hz.
Finally, the limited working volume of current electromagnetic tracking systems was addressed by developing a novel magnetic field generation technique using code division multiplexing. The theoretical foundation of the new field modulation technique is presented with both mathematical analysis and simulation. A new system control unit, together with a new field generator design and accompanying data-driven magnetic model, demonstrates the feasibility of using code division multiplexing for tracking systems with many field emitter sources.
Together, these contributions advance the state of the art in electromagnetic tracking across sensing, wireless communication, field generation, and clinical application. Through the integration of rigorous theoretical analysis, hardware development, pre-clinical validation, and clinical translation, the work highlights its potential to meaningfully improve surgical navigation. The thesis establishes a pathway toward next-generation electromagnetic tracking systems that are wireless, scalable, and clinically viable, with immediate applications in cardiothoracic surgery and broad relevance to other surgical navigation domains.
Description
Keywords
Surgical navigation , Image-guided surgery , Electromagnetic tracking , Sensors , Wireless communications , Bluetooth
Citation
Crowley, D 2025. Intelligent electronics design in magnetic tracking for image-guided surgery. PhD Thesis, University College Cork.