A novel marker for estimating the pose of a CT-guided robotic device using a single slice

Automatic robot / Computed Tomography (CT) scanner registration is an important feature for robot-assisted percutaneous needle placement under CT-scanner. This registration can be done using 3D images, but for fast, low X-ray radiation it is interesting to be able to perform the registration with a single slice. In this paper, a new marker is proposed, which allows to estimate the pose of a device using a single slice. This marker, called ZCM, consists of three circles or ellipses arranged in a Z-shape configuration. It is shown that it provides a larger workspace (i.e. a larger set of visible configurations) for pose measurement than the standard Brown-Roberts-Wells, while maintaining a good accuracy. A closed-form method is proposed for solving the pose estimation with this marker. Simulations and experimental tests using a mock-up patient-mounted robot are presented and confirm the theoretical analysis.