Anso, Juan

Bell, Brett

Caversaccio, Marco

Gavaghan, K

Gerber, Nicolas

Weber, Stefan

Williamson, Tom

English

Bern Open Repository and Information System (BORIS)

source: https://doi.org/10.48350/68421 | downloaded: 1.8.2022trajectory. Postoperative CBCT data was registered to preoperativeplanning data to determine the final accuracy of the drilled tunnel.ResultsThe mean error at the entrance and target was found to be0.06 ± 0.04 mm and 0.28 ± 0.09 mm (N = 3) respectively. Withinthe postoperative images, it was observed that all vital anatomy waspreserved (refer to Fig. 2).ConclusionWithin this work we proposed a surgical planning software tool for arobotically performed DCA that enables safe trajectory planning andsufficiently accurate patient-to-image registration. The proposedplanning software tool enabled an effective DCA to be drilled withpreservation of all structures during the initial cadaver evaluation,demonstrating that the 1 mm safety margin to the facial nerveinclusive of TRE was sufficient.Feasibility of detection of the facial nerve using EMGduring robotic direct cochlear accessJ. Anso1, B. Bell1, N. Gerber1, T. Williamson1, K. Gavaghan1,M. Caversaccio2, S. Weber11ARTORG Center for Biomedical Engineering, University of Bern,Switzerland2Department of ENT, Head and Neck Surgery, Inselspital,University of Bern, SwitzerlandKeywords Facial nerve  EMG Direct cochlear access  Image guidedtherapyPurposeDirect cochlear access (DCA) is an image-guided minimally invasivesurgical procedure which creates a small diameter tunnel to themiddle ear cavity and thereby foregoes the necessity of the traditionalmastoidectomy. High accuracy image and mechanical guidance arenecessary to avoid several risk structures in the region of the DCA [1].Several such navigation systems have been reported to date includingstereotactic frames [2] and industrial [3] or use-specific robot systems[4]. Although several of these works have produced clinicallyacceptable levels of technical accuracy, errors which remain unde-tected at any of the various stages of the workflow can compromisethe safety and efficacy of the intervention. Thus, a need exists forintraoperative error detection.The facial nerve (FN) is the key structure at risk during the DCAprocess. Electroneurography (ENG) was targeted as a possiblemethod of ensuring the safety of the FN during the drilling procedure.In short, electroneurography utilizes electromyography (EMG) todetect muscle contraction in response to a stimulation of a motornerve by a current injected through a suitable probe in close prox-imity. As the stimulatory response is directly dependent on currentdensity, the proximity of the probe to the nerve could potentially beestimated. Bernardeschi et al. tested the ability of a drill-integratedENG system to give an early warning of impending contact with theFN [5]. Drilling was stopped immediately following a warning fromthe system, and the remaining thickness of the bony canal surroundingthe nerve was evaluated in postoperative CT analysis. This analysisshowed that the sensitivity of the system was to low (zero bonethickness in several instances) to be useful for DCA.In this work we present the initial results of a live animal studywhere an ENG enabled drill was used in conjunction with a surgicalrobot system to accurately correlate the distance to the FN with theEMG stimulation intensity.Materials and methodsThe main components of the integrated system are a 5 DOF serialkinematic surgical robot, controlled by a surgical navigation system andwhich is connected to an ENG stimulation drill and monitor (Stimbur/NIM 3.0, Medtronic, USA). A data interface (DAQ-NI 6215, NationalInstruments, USA) between the stimulation monitor and the navigationsystem allows exchange of stimulation and EMG signals which are thencorrelated with the tool position in the navigation system.EMG data was collected from live animal surgeries which closelymimic the image-guided and robot assisted DCA procedure inhumans. This surgical workflow includes: High resolution imaging,computer assisted planning of the intervention, patient-image regis-tration, and finally the robotic assisted intervention where a smalldiameter tunnel is drilled to the middle ear cavity. Four surgeries onsheep were conducted following the proposed image guided workflowunder the approval of the local animal protection commission(approval number 56/10). An appropriate anaesthetic protocol wasdesigned to minimize pain in the subjects yet maintain muscle activity(for premedication diazepam 0.1 mg/kg and Butorphanol 0.1 mg/kgIV; general anaesthesia with thiopental 2.5 % IV; maintenance ofanaesthesia with Isoflurane in 100 % oxygen; ringers Lactate Solutionat a rate of 10 ml/kg/h). After gaining surgical access to the mastoidregion four 1.5 9 3 mm titanium screws (M-5220.03, Medartis,Switzerland) were inserted in the temporal bone for later imageregistration. The temporal bone was imaged at 0.75 9 0.5 9 0.5 mm3using a 16-slice scanner (Brilliance, Philips AG). Using a purposebuilt software planning tool, up to 9 parallel trajectories were plannedat varying distances (0, 0.5 and 1 mm) from the facial nerve andtransferred to the robot system.After imaging, the animal was placed on the OR table with thesurgical robot mounted. After fixing a reference tracker and the EMGelectrodes (Orbicularis Oris and Oculi or Auricularis) the head wasregistered by localizing the implanted fiducial screws. Finally, theplanned trajectories were drilled using a standard surgical 1.6 mmtwist drill while simultaneously stimulating at a rate of 4 Hz with thestimulation intensity ramping from 1.5 to 2.5 mA (0.5 mA steps) andback continually throughout the drilling.Postoperatively, the recorded EMG signals were mapped inrespect to distances from the drill bit to the facial nerve using theactual position of the drilled trajectory from postopterative cone beamFig. 1 Trajectory definition (left). Minimum distances to structures(right)Fig. 2 DCA drilling result with drilled trajectory segmented withAmira and overlayed on the preoperative plan created with theproposed planning software toolInt J CARS (2013) 8 (Suppl 1):S101–S107 S105123CT scans (ProMax, Planmeca Oy, Finland) with a final isometricvoxel size of (0.15 mm)3.ResultsFour different subjects were drilled in this pilot study. Three of thempresented acceptable levels of EMG signal to noise ratio (subjects 1,3, 4), whereas one was too noisy due to a technical malfunction(subject 2). A high registration error appeared in subject 3 (laterdetermined to be an imaging artifact) affecting the accuracy of thetunnels. A total of 11 trajectories were pre-selected for further eval-uation. Distances to first EMG response was evaluated for thesetrajectories (see Table 1). In Fig. 1, an example of an EMG mapping(subject 1) versus distance to FN is presented for the different stim-ulation intensities. An offset value representing the lateral distancefrom the center of the FN to the center of the trajectory is alsorepresented.ConclusionsInterestingly, trajectories intersecting the FN (shortest offsets) did notproduce an early response in most cases. Additionally, stimulationcurrents at 1.5 were not sensitive enough to produce EMG response inmost of the cases. Only the stimulations at 2.5 and 2.0 mA producedearly responses in some more cases. These results showed that thelevel of sensitivity and specificity is not enough to ensure safetyduring robotic direct cochlear access with the current stimulation anddrill bit tools. The future work will evaluate new drilling tools toincrease stimulation sensitivity and specificity.References[1] Schipper J, Aschendorff A, Arapakis I, Klenzner T, Teszler CB,Ridder GJ, Laszig R (2004) Navigation as a quality managementtool in cochlear implant surgery. J Laryngol Otol 118(10):764–770[2] Labadie RF, Chodhury P, Cetinkaya E, Balachandran R, HaynesDS, Fenlon MR, Jusczyzck AS, Fitzpatrick JM (2005) Mini-mally invasive, image-guided, facial-recess approach to themiddle ear: demonstration of the concept of percutaneouscochlear access in vitro. Otol Neurotol 26(4):557–562[3] Majdani O, Bartling SH, Leinung M, Stöver T, Lenarz M, DullinC, Lenarz T (2008) A true minimally invasive approach forcochlear implantation: high accuracy in cranial base navigationthrough flat-panel-based volume computed tomography. OtolNeurotol 29(2):120–123[4] Bell B, Stieger C, Gerber N, Arnold A, Nauer C, Hamacher V,Kompis M, Nolte L, Caversaccio M, Weber S (2012) A self-developed and constructed robot for minimally invasivecochlear implantation. Acta Otolaryngol, pp 1–6[5] Bernardeschi D, Meskine N, Al Otaibi N, Ablonczy R,Kalamarides M, Grayeli AB, Sterkers O (2011) Continuousfacial nerve stimulating burr for otologic surgeries. OtolNeurotol 32(8):1347–1351Newly developed endoscopic surgical navigator demonstratingthe position of the center in an endoscopic viewS. Yamamoto1, H. Mineta21Hamamatsu University School of Medicine, Medical PhotonicsResearch Center, Hamamatsu, Japan2Hamamatsu University School of Medicine, Departmentof Otorhinolaryngology, Hamamatsu, JapanKeywords Frameless navigator  Markerless navigator  Endoscopicsinus surgery  White light ScannerPurposeWhile endoscopic sinus surgery (ESS) has been widely used for thepatients with sinusitis, nasal polyps, and tumors, some complicationsincluding blindness, double vision, and massive bleeding remainserious. To avoid them, surgical navigation during surgery is veryuseful. However, the available navigators for ESS remain to bedeveloped, because they require the spherical markers on the surgicalinstruments. These markers may disturb the surgical procedures, sincethe spaces for ESS are narrow and are crowded with surgeons’ handsand instruments. To resolve this problem, we have developed a newsurgical navigator that demonstrates the position not of the instru-ments but of the center in endoscopic view on the computedtomography (CT) images.MethodsTo acquire the 3D data for registering patients’ images and trackinginstruments, a white light surface scanner, Fscan (Pulstec IndustrialCo., Ltd., Hamamatsu, Japan) was used. Projecting modulated stripedpattern using a white light of xenon lamp, this scanner provides thesurface 3D data within 0.6 s with high resolution (0.1 mm in theZ-axis and 0.6 mm in the X- and Y-axes) and with high accuracyTable 1 Summary of distances to FN at first EMG response for thethree different evaluated intensitiesSubject Trajectory Offset (mm)a Distance at first EMG response(mm)b1.5 mA 2.0 mA 2.5 mA1 1 2.5 NR 1.4 1.92 2.2 NR 1.0 1.03 0.1 NR NR 0.43 4 1.6 2.1 0.1 0.0c5 0.9 NR 0.0c 0.0c6 0.9 NR 0.0c 0.0c4 7 1.7 0.0 0.0c 0.58 1.5 NR NR NR9 0.4 NR 0.0c 0.0c10 0.3 0.0 0.0c 0.0c11 0.1 NR NR NRNR no responsea Shortest distance from the axis of the drilled tunnel to the centre ofFNb Shortest distance from the drill bit surface to the FN surface at firstEMG responsec Penetration of the FN at first EMG responseFig. 1 3D representation of the EMG data recorded for Subject 1 foreach of the 3 drilled trajectories. The postoperative calibrateddistances from the drill bit to the facial nerve surface are labeled asdistance to FN. The shortest distances from the drill bit axis to thecenter of the FN are labeled as offset. In the 3D scene, the plannedtunnels, the postop segmented trajectories (orange, green and purple)and the FN are representedS106 Int J CARS (2013) 8 (Suppl 1):S101–S107123

Feasibility of detection of the facial nerve using EMG during robotic direct cochlear access

https://boris.unibe.ch/68421/1/2013_Article_ComputerAssistedENTSurgery_pp105_Anso.pdf

Feasibility of detection of the facial nerve using EMG during robotic direct cochlear access

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