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Proceedings Paper

Hybrid tracking system for flexible endoscopes
Author(s): Johann Hummel; Michael Figl; Wolfgang Birkfellner; Christopher Ede; Rudolf Seemann; Helmar Bergmann
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Paper Abstract

With the miniaturization of electromagnetic tracking systems (EMTS) the range of possible applications in image guided therapy was extending. A diameter smaller than 1 mm allows for mounting these sensors into the working channel of flexible endoscopes for navigation within the body. Knowing the exact position of the instrument with respect to the patient’s position preoperative CT or MR images can simplify and ease navigation during various interventions. The Aurora EMTS seems to be an ideal choice for this purpose. However, using this system exhibits an important limitation: the sensor offers just 5 degrees of freedom (DOF) which means that rotations round the axis of the sensor cannot be measured. To overcome this restriction we used an additional optical tracking system (OTS) which is calibrated to deliver the missing DOF. To evaluate the suitability of our new navigation system we measured the Fiducial Registration Error (FRE) of the diverse registrations and the Target Registration Error (TRE) for the complete transformation from the US space to the CT space. The FRE for the ultrasound calibration amounted to 3.2 mm±2.2 mm, resulting from 10 calibration procedures. For the transformation from the OTS reference system to the EMTS emitter space we found an average FRE of 0.8 mm±0.2 mm. The FRE for the CT registration was 1.0 mm±0.3 mm. The TRE was found to be 5.5 mm± 3.2 mm.

Paper Details

Date Published: 5 May 2004
PDF: 6 pages
Proc. SPIE 5367, Medical Imaging 2004: Visualization, Image-Guided Procedures, and Display, (5 May 2004); doi: 10.1117/12.534002
Show Author Affiliations
Johann Hummel, Vienna General Hospital (Austria)
Ludwig-Boltzmann Institute of Nuclear Medicine (Austria)
Michael Figl, Vienna General Hospital (Austria)
Wolfgang Birkfellner, Vienna General Hospital (Austria)
Christopher Ede, Vienna General Hospital (Austria)
Rudolf Seemann, Vienna General Hospital (Austria)
Helmar Bergmann, Vienna General Hospital (Austria)
Ludwig-Boltzmann Institute of Nuclear Medicine (Austria)

Published in SPIE Proceedings Vol. 5367:
Medical Imaging 2004: Visualization, Image-Guided Procedures, and Display
Robert L. Galloway, Editor(s)

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