Endoscopic navigation system using 2D/3D registration

摘要

The paper describes a computer-aided navigation system using image fusion to support endoscopic intervention like accurate collection of biopsy specimen. In particular, an endoscope which provides the physician with real time ultrasound (US) and a video image, is equipped with an electromagnetic tracking sensor. An image slice that corresponds to the actual image of the US scan head is derived from a preoperative computed tomography (CT) volume data set by means of oblique reformatting. Both views are displayed side by side. The position of the image acquired by the US scanhead is determined by the miniatured electromagnetic tracking system (EMTS) after applying a calibration to the endoscope's scanhead. The relative orientation between the patient coordinate system and a preoperative dataset (such CT or magnetic resonance (MR) image) is derived from a 2D/3D registration. This was achieved by calibrating an interventional CT slice by means of an optical tracking system (OTS) using the same algorithm as for the US calibration. Then the interventional CT slice is used for a 2D/3D registration into the coordinate system of the preoperative CT. The fiducial registration error (FRE) for the US calibration amounted to 3.6 mm +/- 2.0 mm. For the interventional CT we found a FRE of 0.36 +/-0.12 mm. The error for the 2D/3D registration was 2.3 +/- 0.5 mm. The point-to-point registration between to OTS and the EMTS was accomplished with an FRE of 0.6 mm.