Electromagnetic Tracking System Assessment

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Dr. Haidegger Tamás Péter
Department of Control Engineering and Information Technology

Medical technology and devices have shown an incredible development in the past three decades. New trends have evolved for the patient’s more effective care supported by technical instruments and technology. The aim of the Minimally Invasive Surgery is to reduce side effects and collateral damage to healthy tissue. With this technique, the bloodloss and thereby the recovery time is highly reduced, along with furthermore the risk of complication and infection is diminished.

Image-Guided Surgery allows the real time tracking of surgical tools during operation and the visualization of their movement on the patient’s 3D model, created based on pre-operative images. The optical tracking systems are the most frequently used in the operating room, but electromagnetic tracking is also getting more and more popular because they do not require the line of sight. The position and orientation of tiny sensors can be determined with sub-millimeter accuracy in the electromagnetic field created by a generator, even within the human body. Their first and most prominent application are the catheter-based cardiac procedures and more recently, they have been applied to bronchoscopy and interventional radiology procedures.

One of the major barriers to the wider spread of electromagnetic tracking solutions is their susceptibility to ferromagnetic materials and external electromagnetic distortions. These result that the accuracy and the reliability of the system is reduced. The research community has long been engaged with the topic to find engineering solutions to increase measurement reliability and accuracy. For the realization of this, finding and modeling of the errors of the tracking systems is necessary.

This diploma thesis gives a comprehensive overview of electromagnetic tracking technology, its typical accuracy and errors. I introduce the experimental methods and their feasibility for detecting the errors. I go into details discussing the measurement protocol used in the electromagnetic tracking systems’ static analysis. Furthermore, I present a new measurement and modeling technique, which is able to describe the distortion of the position. I refer to the brachytherapy platform applied in the dynamic analysis of the sensor. Finally, I describe the measurement and the results of the distortions by the presence of the surgical instruments. The main principal of my work was to give a precise description of the errors of the electromagnetic tracking systems and therefore to make my results applicable for error compensation in the operating room.


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