Modality-integrated magnetic catheter tracking for x-ray vascular interventions.

A novel setup for the integration of a magnetic tracking system (MTS) into a catheter laboratory environment by attaching the field generator of the MTS to the C-arm of the x-ray system was investigated. The metal interference of the x-ray system with the MTS then becomes static and can be calibrated. The registration of a tracked catheter to 2D live x-ray images with high and well-defined accuracy is thus possible for arbitrary C-arm positions. Interference with imaging by blocking the field of view is avoided. Real-time registration methods to maintain the registration of the catheter also to static 2D or 3D images (roadmaps), regardless of the C-arm rotation during catheter tracking, were investigated. Residual registration errors of the tracked catheter with respect to the static roadmaps (2D and 3D) were reduced by using the vessel geometry and shape information. The algorithms potentially allow for motion correction (e.g. due to respiration). Using the shape-based correction algorithms the average registration accuracies to static roadmaps for different C-arm angulations and catheter positions were determined to be 3.3-4.2 mm. The magnetic registration of the C-arm was furthermore allowed to compute the imaging geometry (position of the C-arm) and to produce virtual angiographic preview images before contrast injection and x-ray dose application. Thus, optimal projection geometries and collimator settings for the target region can be chosen in an 'off line' fashion. The proposed MTS-supported navigation setup on both 3D (static) and 2D (live and static) roadmaps merges the high resolution and real-time feedback of 2D x-ray images with the navigation support from 3D static images.