Highly precise navigation at the lateral skull base by the combination of flat-panel volume CT and electromagnetic navigation

Abstract

This study aimed to evaluate the feasibility and accuracy of electromagnetic navigation at the lateral skull base in combination with flat panel volume computed tomography (fpVCT) datasets. A mastoidectomy and a posterior tympanotomy were performed on 10 samples of fresh frozen temporal bones. For registration, four self-drilling titanium screws were applied as fiducial markers. Multi-slice computed tomography (MSCT; 600 µm), conventional flat panel volume computed tomography (fpVCT; 466 µm), micro-fpVCT (197 µm) and secondary reconstructed fpVCT (100 µM) scans were performed and data were loaded into the navigation system. The resulting fiducial registration error (FRE) was analysed, and control of the navigation accuracy was performed. The registration process was very quick and reliable with the screws as fiducials. Compared to using the MSCT data, the micro-fpVCT data led to significantly lower FRE values, whereas conventional fpVCT and secondary reconstructed fpVCT data had no advantage in terms of accuracy. For all imaging modalities, there was no relevant visual deviation when targeting defined anatomical points with a navigation probe. fpVCT data are very well suited for electromagnetic navigation at the lateral skull base. The use of titanium screws as fiducial markers turned out to be ideal for comparing different imaging methods. A further evaluation of this approach by a clinical trial is required.

Mean projection image application to the automatic rotation axis alignment in cone-beam CT

“…The marker-based methods involve tracking the trajectory of reference markers, such as small gold beads or silica balls, which are either mounted on a sample container (such as a capillary) or placed directly into or on the sample [10]. Despite the high accuracy [11], the methods based on the use of fiducial markers have got a significant disadvantage: they require high costs for more complex sample preparation. The possibility of the markers displacements during the observation of the sample cannot be ruled out [12].…”

Skull-Base Surgery—A Narrative Review on Current Approaches and Future Developments in Surgical Navigation

“…Optical tracking is based on an infrared stereo-camera, which detects the position of a probe with regards to an optical reference, marked with reflective spheres or light-emitting diodes [ 26 ]. It is still debated which system provides better performances in terms of accuracy and ergonomics; however, both approaches may show an error range within a few millimeters [ 3 , 27 , 28 , 29 , 30 ]. In terms of potential pitfalls, interruptions in the line of sight between the stereo-camera and the reference and/or probe may result in a disturbance in the anatomical location in optical systems [ 25 ].…”

“…In trans-sphenoidal approaches without well pneumatized sinuses or revisions, navigation was particularly useful in confirming the position of the internal carotid artery or in locating major neural structures, such as the optic nerve [ 35 , 36 , 37 ]. Despite moderate use of navigation technology in lateral skull-base surgery [ 30 , 38 , 39 ], reports have demonstrated operative time reduction, optimized exposure for surgical corridors, and increased safety in difficult cases [ 39 ]. Other skull-base surgery series, albeit with small samples, showed the advantage of the navigation system in the perioperative outcomes [ 11 , 40 , 41 , 42 , 43 , 44 ].…”