Abstract

Objectives: Surgical navigation guides surgery without radiation by mapping instrument locations onto preoperative CT (pCT). Adoption to vascular surgery remains novel. Feasibility of spatially-tracked ultrasound (US) for surgical registration and wire localization relative to pCT is demonstrated. Methods: pCT was taken (0.6mm) of a carotid artery phantom and a CT artery model (CTM) segmented. An US probe (Philips L17-5), was rigidly attached to an optical tracker and swept along the artery (1000 images). A navigation system (Medtronic StealthStation) acquired the tracker and 2D US image's positions via a spatial calibration (1.6mm accuracy). The artery in each image was segmented and tracking data combined to reconstruct a 3D US artery model (USM) (Fig. 1). The CTM and USM were registered via an iterative closest point algorithm. A Rosen wire (0.035in) was inserted into the artery. Acquiring an US sweep of the wire (500 images), it was segmented in each image via thresholding. Segmentations and tracking were combined into a 3D US wire-model (USWM). Its position was overlaid onto pCT via the USM-CTM registration. Another CT was acquired, registered via a fiducial point-based registration (0.86 mm accuracy), and the ground truth wire position segmented (Fig. 2). A tip-to-tip distance was measured between the USWM and CT wire positions. Results: CTM-to-USM registration error was 0.93 mm (RMSE) between artery point clouds. The tip-to-tip distance between CT and USWM wire models was 0.2 (longitudinal) and 1.4 (radial) mm. Conclusions: A vascular navigation framework capable of patient registration and highly accurate instrument localization is provided using tracked iUS.