The endonasal patient reference tracker: a novel solution for accurate noninvasive electromagnetic neuronavigation

Abstract

OBJECTIVEElectromagnetic (EM) navigation provides the advantages of continuous guidance and tip-tracking of instruments. The current solutions for patient reference trackers are suboptimal, as they are either invasively screwed to the bone or less accurate if attached to the skin. The authors present a novel EM reference method with the tracker rigidly but not invasively positioned inside the nasal cavity.METHODSThe nasal tracker (NT) consists of the EM coil array of the AxiEM tracker plugged into a nasal tamponade, which is then inserted into the inferior nasal meatus. Initially, a proof-of-concept study was performed on two cadaveric skull bases. The stability of the NT was assessed in simulated surgical situations, for example, prone, supine, and lateral patient positioning and skin traction. A deviation ≤ 2 mm was judged sufficiently accurate for clinical trial. Thus, a feasibility study was performed in the clinical setting. Positional changes of the NT and a standard skin-adhesive tracker (ST) relative to a ground-truth reference tracker were recorded throughout routine surgical procedures. The accuracy of the NT and ST was compared at different stages of surgery.RESULTSEx vivo, the NT proved to be highly stable in all simulated surgical situations (median deviation 0.4 mm, range 0.0–2.0 mm). In 13 routine clinical cases, the NT was significantly more stable than the ST (median deviation at procedure end 1.3 mm, range 0.5–3.0 mm vs 4.0 mm, range 1.2–11.2 mm, p = 0.002). The loss of accuracy of the ST was highest during draping and flap fixation.CONCLUSIONSApplication of the EM endonasal patient tracker was found to be feasible with high procedural stability ex vivo as well as in the clinical setting. This innovation combines the advantages of high precision and noninvasiveness and may, in the future, enhance EM navigation for neurosurgery.

Novel microscope-based visual display and nasopharyngeal registration for auditory brainstem implantation: a feasibility study in an ex vivo model

“…We report a maximum (intrasurgical) dislocation of the spherical marker, < 1.72 mm, which is in agreement with a recent endonasal magnetic tracker (< 2 mm) [28]. As reported in the clinical setting, this is better than a skin adhesive tracker (< 3 mm) [28]. The mean±standard deviation TRE measured on the implanted screw targets (2.71 ± 0.99 mm) is higher compared to registration with screws (< 1.0 mm [29]); approximately equal to adhesive marker registration (2.49 ± 0.86 mm [31]); and lower than surface matching-based registration (5.35 ± 1.64 mm [31]) as observed in clinical setup.…”

“…We report a maximum (intrasurgical) dislocation of the spherical marker, < 1.72 mm, which is in agreement with a recent endonasal magnetic tracker (< 2 mm) [28]. As reported in the clinical setting, this is better than a skin adhesive tracker (< 3 mm) [28].…”

“…In fact, in many other medical procedures, less invasiveness, accurate target localization, and reduced risk of complications were reported by physicians when using neuronavigation (or image-guided surgery) systems [ 26 – 28 ]. We hypothesize that these systems might offer solutions to surgeons confronting challenges during the conventional ABI approach, including more predictable and consistent surgical and audiological outcomes.…”

A Patient-Specific Reference Tracker for Noninvasive Electromagnetic Navigation of Endoscopic Skull Base Surgery

“…The deviation from a baseline of 0 distance between the RT (which served as the gold standard) and each of the 2 test trackers (ST, OT, Figure 2) was used, as described previously. 22…”

“…The deviation from a baseline of 0 distance between the RT (which served as the gold standard) and each of the 2 test trackers (ST, OT, Figure 2) was used, as described previously. 22 The software reads coordinates of the tip and hind regions in the 2 observed frames and logs this information in a user-defined frequency in standard comma-separated values format.…”