A Dual-Modal Fiducial Marker with Single-View X-ray Pose Recoverability for MR-Guided Surgical Navigation

Abstract

Abstract Traditional surgical navigation markers rely on a fixed external reference frame. However, in mixed reality (MR) surgical navigation, the tracking camera moves with the surgeon's head, making conventional markers unsuitable for this application. This study proposes that markers for MR navigation must satisfy three design constraints: omnidirectional recognizability, X-ray recognizability, and multimodal registration.Based on these constraints, this study designs a marker structure consisting of a central cube and four cylindrical axes with varying diameters. Through mathematical analysis, it is proven that the marker’s 6 degrees of freedom can be determined from a single X-ray image under a known X-ray projection system. A pose estimation algorithm combining geometric optimization and deep learning-based feature extraction was used to validate the marker’s X-ray and optical poses.In the validation performed on 100 sets of X-ray images and 194 sets of optical images, the X-ray recognition error was measured as a coronal plane deviation of 1.584 ± 1.256° and a sagittal plane deviation of 1.898 ± 1.502°. The optical recognition success rate reached 90.2%, with an overall angular error of 1.521 ± 0.976°. The error distribution across modalities was symmetrically zero-centered, and the redundancy of the four cylindrical axes maintained solvability even under extreme viewing angles. The results indicate that this design methodology can serve as a reference for the development of MR surgical navigation markers.