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23 February 2010 Active self-calibration of thoracoscopic images for assisted minimally invasive spinal surgery
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Registration of thoracoscopic images to a preoperative 3D model of the spine is a prerequisite for minimally invasive surgical guidance. We propose an active self-calibration method of thoracoscopic image sequences acquired by an angled monocular endoscope with varying focal length during minimally invasive surgery of the spine. The extrinsic parameters are updated in real time by a motion tracking system while the intrinsic parameters are determined from a set of geometrical primitives extracted from the image of the surgical instrument tracked throughout the thoracoscopic sequence. A particle filter was used for the tracking of the instrument on the image sequence that was preprocessed to detect and correct reflexions due to the light source. The proposed method requires undertaking a pure rotation of the endoscope to update the focal length and exploits the inherent temporal rigid motion of the instrument through consecutive frames. A pure rotation is achievable by undertaking a rotation of the scope cylinder with respect to the head of the camera. Therefore, the surgeon may take full advantage of an angled endoscope by adjusting focus and zoom during surgery. Simulation experiments have assessed the accuracy of the obtained parameters and the optimal number of geometrical primitives required for an active self-calibration of the angled monocular endoscope. Finally, an in vitro experiment demonstrated that 3D reconstruction of rigid structures tracked throughout a monocular thoracoscopic image sequence is feasible and its accuracy is adequate for the registration of thoracoscopic images to a preoperative MRI 3D model of the spine.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Fantin Girard, Fouzi Benboujja, Stefan Parent, and Farida Cheriet "Active self-calibration of thoracoscopic images for assisted minimally invasive spinal surgery", Proc. SPIE 7625, Medical Imaging 2010: Visualization, Image-Guided Procedures, and Modeling, 76250Q (23 February 2010);


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