Real-time surgical tool tracking and pose estimation using a hybrid cylindrical marker

Abstract

PurposeTo provide an integrated visualisation of intraoperative ultrasound and endoscopic images to facilitate intraoperative guidance, real-time tracking of the ultrasound probe is required. State-of-the-art methods are suitable for planar targets while most of the laparoscopic ultrasound probes are cylindrical objects. A tracking framework for cylindrical objects with a large work space will improve the usability of the intraoperative ultrasound guidance.MethodsA hybrid marker design that combines circular dots and chessboard vertices is proposed for facilitating tracking cylindrical tools. The circular dots placed over the curved surface are used for pose estimation. The chessboard vertices are employed to provide additional information for resolving the ambiguous pose problem due to the use of planar model points under a monocular camera. Furthermore, temporal information between consecutive images is considered to minimise tracking failures with real-time computational performance.ResultsDetailed validation confirms that our hybrid marker provides a large working space for different tool sizes (6–14 mm in diameter). The tracking framework allows translational movements between 40 and 185 mm along the depth direction and rotational motion around three local orthogonal axes up to pm 80^circ . Comparative studies with the current state of the art confirm that our approach outperforms existing methods by providing nearly 100% detection rates and accurate pose estimation with mean errors of 2.8 mm and 0.72^circ . The tracking algorithm runs at 20 frames per second for 960times 540 image resolution videos.ConclusionExperiments show that the proposed hybrid marker can be applied to a wide range of surgical tools with superior detection rates and pose estimation accuracies. Both the qualitative and quantitative results demonstrate that our framework can be used not only for assisting intraoperative ultrasound guidance but also for tracking general surgical tools in MIS.