title: Optical coherence tomography guided laser cochleostomy: towards the accuracy on tens of micrometer scale.
abstract: Lasers have been proven to be precise tools for bone ablation. Applying no mechanical stress to the patient, they are potentially very suitable for microsurgery on fragile structures such as the inner ear. However, it remains challenging to control the laser-bone ablation without injuring embedded soft tissue. In this work, we demonstrate a closed-loop control of a short-pulsed CO2 laser to perform laser cochleostomy under the monitoring of an optical coherence tomography (OCT) system. A foresighted detection of the bone-endosteum-perilymph boundary several hundred micrometers before its exposure has been realized. Position and duration of the laser pulses are planned based on the residual bone thickness distribution. OCT itself is also used as a highly accurate tracking system for motion compensation between the target area and the optics. During ex vivo experimental evaluation on fresh porcine cochleae, the ablation process terminated automatically when the thickness of the residual tissue layer uniformly reached a predefined value. The shape of the resulting channel bottom converged to the natural curvature of the endosteal layer without injuring the critical structure. Preliminary measurements in OCT scans indicated that the mean absolute accuracy of the shape approximation was only around 20 μm.
authors.affiliation: Institute for Anthropomatics and Robotics (IAR)-Intelligent Process Control and Robotics (IPR), KIT, Engler-Bunte-Ring 8, 76131 Karlsruhe, Germany.
authors.forename: Yaokun
authors.identifier: 0000-0001-7206-0916
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Ludwig-Maximilians-University, Oettingenstraße 67, 80538 Munich, Germany.
authors.forename: Tom
authors.identifier: 0000-0001-7791-1126
authors.initials: T
authors.lastname: Pfeiffer
authors.affiliation: Department of Otorhinolaryngology, Düsseldorf University Hospital, Moorenstraße 5, 40225 Düsseldorf, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Weller
authors.affiliation: Ludwig-Maximilians-University, Oettingenstraße 67, 80538 Munich, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wieser
authors.affiliation: Institute for Biomedical Optics, University of Lübeck, Gebäude 81, Raum R 67, Peter-Monnik-Weg 4, 23562 Lübeck, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Huber
authors.affiliation: Institute for Anthropomatics and Robotics (IAR)-Intelligent Process Control and Robotics (IPR), KIT, Engler-Bunte-Ring 8, 76131 Karlsruhe, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Raczkowsky
authors.affiliation: Department of Otorhinolaryngology, Düsseldorf University Hospital, Moorenstraße 5, 40225 Düsseldorf, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Schipper
authors.affiliation: Institute for Anthropomatics and Robotics (IAR)-Intelligent Process Control and Robotics (IPR), KIT, Engler-Bunte-Ring 8, 76131 Karlsruhe, Germany.
authors.forename: Heinz
authors.initials: H
authors.lastname: Wörn
authors.affiliation: Department of Otorhinolaryngology, Düsseldorf University Hospital, Moorenstraße 5, 40225 Düsseldorf, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Klenzner
mesh_terms: D000818:Animals; D003051:Cochlea / Q000473:pathology / Q000601:surgery*; D006801:Humans; D053685:Laser Therapy / Q000379:methods*; D054020:Lasers, Gas; D013552:Swine; D041623:Tomography, Optical Coherence / Q000379:methods*