In-Vivo Electrical Impedance Measurement in Mastoid Bone
- 322 Downloads
Nerve monitoring is a safety mechanism to detect the proximity between surgical instruments and important nerves during surgical bone preparation. In temporal bone, this technique is highly specific and sensitive at distances below 0.1 mm, but remains unreliable for distances above this threshold. A deeper understanding of the patient-specific bone electric properties is required to improve this range of detection. A sheep animal model has been used to characterize bone properties in vivo. Impedance measurements have been performed at low frequencies (<1 kHz) between two electrodes placed inside holes drilled into the sheep mastoid bone. An electric circuit composed of a resistor and a Fricke constant phase element was able to accurately describe the experimental measurements. Bone resistivity was shown to be linearly dependent on the inter-electrode distance and the local bone density. Based on this model, the amount of bone material between the electrodes could be predicted with an error of 0.7 mm. Our results indicate that bone could be described as an ideal resistor while the electrochemical processes at the electrode-tissue interface are characterized by a constant phase element. These results should help increasing the safety of surgical drilling procedures by better predicting the distance to critical nerve structures.
KeywordsFacial nerve monitoring Resistivity Cochlear implant Nerve preservation
This work is part of the HearRestore project, scientifically evaluated by the SNF, financed by the Swiss Confederation, and funded by Nano-Tera.ch.
- 1.Ansó, J., C. Dür, K. Gavaghan, H. Rohrbach, N. Gerber, T. Williamson, E. M. Calvo, T. W. Balmer, C. Precht, D. Ferrario, M. S. Dettmer, K. M. Rösler, M. D. Caversaccio, B. Bell, and S. Weber. A neuromonitoring approach to facial nerve preservation during image-guided robotic cochlear implantation. Otol. Neurotol. 37:89–98, 2016.CrossRefPubMedGoogle Scholar
- 21.Labadie, R. F., R. Balachandran, J. H. Noble, G. S. Blachon, J. E. Mitchell, F. A. Reda, B. M. Dawant, and J. M. Fitzpatrick. Minimally invasive image-guided cochlear implantation surgery: first report of clinical implementation. Laryngoscope 124:1915–1922, 2014.CrossRefPubMedPubMedCentralGoogle Scholar
- 25.Prass, R., and H. Lüders. Constant-current versus constant-voltage stimulation. Neurosurgery 62:622–623, 1985.Google Scholar
- 36.Wanna, G. B., R. Balachandran, O. Majdani, J. Mitchell, and R. F. Labadie. Percutaneous access to the petrous apex in vitro using customized micro-stereotactic frames based on image-guided surgical technology. Acta Otolaryngol. 1–6, 2009.Google Scholar