Electromagnetic tracking for abdominal interventions in computer aided surgery

Abstract

Electromagnetic tracking has great potential for assisting physicians in precision placement of instruments during minimally invasive interventions in the abdomen, since electromagnetic tracking is not limited by the line-of-sight restrictions of optical tracking. A new generation of electromagnetic tracking has recently become available, with sensors small enough to be included in the tips of instruments. To fully exploit the potential of this technology, our research group has been developing a computer aided, image-guided system that uses electromagnetic tracking for visualization of the internal anatomy during abdominal interventions. As registration is a critical component in developing an accurate image-guided system, we present three registration techniques: 1) enhanced paired-point registration (time-stamp match registration and dynamic registration); 2) orientation-based registration; and 3) needle shape-based registration. Respiration compensation is another important issue, particularly in the abdomen, where respiratory motion can make precise targeting difficult. To address this problem, we propose reference tracking and affine transformation methods. Finally, we present our prototype navigation system, which integrates the registration, segmentation, path-planning and navigation functions to provide realtime image guidance in the clinical environment. The methods presented here have been tested with a respiratory phantom specially designed by our group and in swine animal studies under approved protocols. Based on these tests, we conclude that our system can provide quick and accurate localization of tracked instruments in abdominal interventions, and that it offers a user friendly display for the physician.

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Quantitative evaluation for accumulative calibration error and video-CT registration errors in electromagnetic-tracked endoscopy

“…1 EM-tracked endoscopy involves tracking the tip of the endoscope using an EM position sensor in order to associate the location of the endoscope with pre-operative CT images. Performing video-CT registration is equivalent to finding two transformation matrices: the matrix between EM and CT coordinates; and the matrix between EM and video coordinates procedures [1][2][3]. It can provide accurate tracking without the line-of-sight limitations of optical trackers [4][5][6][7][8].…”

New real-time MR image-guided surgical robotic system for minimally invasive precision surgery

“…Zhang et al used an electromagnetic tracking system instead of optical tracking; they consider that electromagnetic tracking has great potential for assisting physicians in the precise placement of instruments during minimally invasive interventions in the abdomen, as electromagnetic tracking is not limited by the line-of-sight restrictions of optical tracking [13][14][15][16]. The optical tracking system is limited by the line-of-sight restrictions caused by the MR gantry and staff present during intervention.…”