8 March 2013 Image guidance system for flexible endoscopes considering tissue deformation
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Abstract
This paper describes a navigation system for flexible endoscopes equipped with ultrasound scan heads. In contrast to similar systems additional abdominal 3D ultrasound images are used to achieve the required image fusion. An abdominal 3D US image has to be taken preoperatively before the CT scan. The CT is calibrated by means of the optical tracking system (OTS) and the transformation between CT and the calibrated 3D US can be calculated without image registration. Immediately before intervention takes place, a pre-interventional 3D US tracked with an electromagnetic tracking system (EMTS) is acquired and registered intra-modal to the preoperative US. Therefore, we can replace a direct 2D/3D registration from the endoscopic US to the pre-operative CT by an intra-modal USUS registration and tracker calibrations. To consider tissue deformation we implemented an approach using leading points. First, the US images were pre-processed by calculating importance images. The whole information of the image is then reduced to a set of expressive leading points calculated from the importance image. Once the vector field of corresponding leading points is found, a deformation field can be calculated. We found a target registration error for the whole transformation chain from a US pixel to a CT voxel of 4:34 ± 2:56mm (ten targets) on a phantom without deformation.
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Rainer Hoffmann, Rainer Hoffmann, Michael Figl, Michael Figl, Amar Bhatia, Amar Bhatia, Marcus Kaar, Marcus Kaar, Wolfgang Birkfellner, Wolfgang Birkfellner, Andreas Püspök, Andreas Püspök, Alfred Kratochwil, Alfred Kratochwil, Johann B. Hummel, Johann B. Hummel, } "Image guidance system for flexible endoscopes considering tissue deformation", Proc. SPIE 8671, Medical Imaging 2013: Image-Guided Procedures, Robotic Interventions, and Modeling, 867104 (8 March 2013); doi: 10.1117/12.2007410; https://doi.org/10.1117/12.2007410
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