Registration-free workflow for electromagnetic and optical navigation in orbital and craniofacial surgery

R Schreurs,L Dubois,P E M H Habets,F Baan,L F M Beenen,T J J Maal,A G Becking,C Klop

doi:10.1038/s41598-021-97706-5

Abstract

The accuracy of intra-operative navigation is largely dependent on the intra-operative registration procedure. Next to accuracy, important factors to consider for the registration procedure are invasiveness, time consumption, logistical demands, user-dependency, compatibility and radiation exposure. In this study, a workflow is presented that eliminates the need for a registration procedure altogether: registration-free navigation. In the workflow, the maxillary dental model is fused to the pre-operative imaging data using commercially available virtual planning software. A virtual Dynamic Reference Frame on a splint is designed on the patient’s fused maxillary dentition: during surgery, the splint containing the reference frame is positioned on the patient’s dentition. This alleviates the need for any registration procedure, since the position of the reference frame is known from the design. The accuracy of the workflow was evaluated in a cadaver set-up, and compared to bone-anchored fiducial, virtual splint and surface-based registration. The results showed that accuracy of the workflow was greatly dependent on tracking technique used: the workflow was the most accurate with electromagnetic tracking, but the least accurate with optical tracking. Although this method offers a time-efficient, non-invasive, radiation-free automatic alternative for registration, clinical implementation is hampered by the unexplained differences in accuracy between tracking techniques.

Highlights

The accuracy of intra-operative navigation is largely dependent on the intra-operative registration procedure
Automatic Image Registration overcomes the user-dependency issue: intra-operative imaging is acquired with the Dynamic Reference Frame (DRF) in place[7,10,12]
The fixated cadaver heads were equipped with five titanium screws (1.5 × 5.0 mm maxDrive screws, KLS Martin, Tuttlingen, Germany) on the maxilla for bone-anchored fiducial registration, and fourteen Poly-Ether-Ether-Ketone (PEEK) Allen screws to serve as target positions at the following anatomical landmarks: orbital rim, zygomatic prominence, lateral orbital wall, porion, nasion, frontal bone, cranium and occipital bone

Summary

Introduction

The accuracy of intra-operative navigation is largely dependent on the intra-operative registration procedure. The results showed that accuracy of the workflow was greatly dependent on tracking technique used: the workflow was the most accurate with electromagnetic tracking, but the least accurate with optical tracking This method offers a time-efficient, non-invasive, radiation-free automatic alternative for registration, clinical implementation is hampered by the unexplained differences in accuracy between tracking techniques. The ideal registration method would be non-invasive, little time consuming, not logistically challenging, automatic and not user dependent, usable in every patient, compatible with each tracking technique (optical and electromagnetic (EM)), not exposing the patient to additional radiation and, most of all, accurate. A registration-free dental splint-based method is proposed that eliminates user dependency and does not require acquisition of additional intra-operative imaging. Navigation is outlined and the accuracy is compared to bone-anchored maxillary fiducials (optical and EM) and surface-based registration (EM)

Methods

Results

Discussion

Conclusion