title: Does Laser Surgery Interfere with Optical Nerve Identification in Maxillofacial Hard and Soft Tissue?--An Experimental Ex Vivo Study.
abstract: The protection of sensitive structures (e.g., nerves) from iatrogenic damage is of major importance when performing laser surgical procedures. Especially in the head and neck area both function and esthetics can be affected to a great extent. Despite its many benefits, the surgical utilization of a laser is therefore still limited to superficial tissue ablation. A remote feedback system which guides the laser in a tissue-specific way would provide a remedy. In this context, it has been shown that nerval structures can be specifically recognized by their optical diffuse reflectance spectra both before and after laser ablation. However, for a translation of these findings to the actual laser ablation process, a nerve protection within the laser pulse is of utmost significance. Thus, it was the aim of the study to evaluate, if the process of Er:YAG laser surgery--which comes with spray water cooling, angulation of the probe (60°) and optical process emissions--interferes with optical tissue differentiation. For the first time, no stable conditions but the ongoing process of laser tissue ablation was examined. Therefore, six different tissue types (nerve, skin, muscle, fat, cortical and cancellous bone) were acquired from 15 pig heads. Measurements were performed during Er:YAG laser ablation. Diffuse reflectance spectra (4500, wavelength range: 350-650 nm) where acquired. Principal component analysis (PCA) and quadratic discriminant analysis (QDA) were calculated for classification purposes. The clinical highly relevant differentiation between nerve and bone was performed correctly with an AUC of 95.3% (cortial bone) respectively 92.4% (cancellous bone). The identification of nerve tissue against the biological very similar fat tissue yielded good results with an AUC value of 83.4% (sensitivity: 72.3%, specificity: of 82.3%). This clearly demonstrates that nerve identification by diffuse reflectance spectroscopy works reliably in the ongoing process of laser ablation in spite of the laser beam, spray water cooling and the tissue alterations entailed by tissue laser ablation. This is an essential step towards a clinical utilization.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany. bastian.bergauer@uk-erlangen.de.
authors.forename: Bastian
authors.initials: B
authors.lastname: Bergauer
authors.affiliation: Department of Oral and Maxillofacial Surgery, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany. christian.knipfer@fau.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Knipfer
authors.affiliation: Department of Oral and Maxillofacial Surgery, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany. andi.nbg@hotmail.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Amann
authors.affiliation: Department of Oral and Maxillofacial Surgery, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany. maximilian.rohde@fau.de.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Rohde
authors.affiliation: Bavarian Laser Center GmbH (blz), Erlangen 91054, Germany. k.tangermann@blz.org.|SAOT-Graduate School in Advanced Optical Technologies, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany. k.tangermann@blz.org.
authors.forename: Katja
authors.initials: K
authors.lastname: Tangermann-Gerk
authors.affiliation: Department of Medical Informatics, Biometry and Epidemiology, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany. werner.adler@imbe.med.uni-erlangen.de.
authors.forename: Werner
authors.initials: W
authors.lastname: Adler
authors.affiliation: Bavarian Laser Center GmbH (blz), Erlangen 91054, Germany. michael.schmidt@lpt.uni-erlangen.de.|SAOT-Graduate School in Advanced Optical Technologies, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany. michael.schmidt@lpt.uni-erlangen.de.|Chair of Photonic Technologies, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany. michael.schmidt@lpt.uni-erlangen.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Schmidt
authors.affiliation: Department of Oral and Maxillofacial Surgery, Medical University of Vienna, Vienna 1090, Austria. emeka.nkenke@meduniwien.ac.at.
authors.forename: Emeka
authors.initials: E
authors.lastname: Nkenke
authors.affiliation: Department of Oral and Maxillofacial Surgery, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany. florian.stelzle@fau.de.|SAOT-Graduate School in Advanced Optical Technologies, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Erlangen 91054, Germany. florian.stelzle@fau.de.
authors.forename: Florian
authors.initials: F
authors.lastname: Stelzle
mesh_terms: D000818:Animals; D003238:Connective Tissue / Q000294:innervation* / Q000473:pathology / Q000601:surgery; D005147:Facial Bones / Q000294:innervation / Q000473:pathology; D005152:Facial Muscles / Q000294:innervation / Q000473:pathology / Q000601:surgery; D005154:Facial Nerve / Q000473:pathology* / Q000601:surgery*; D053685:Laser Therapy / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D053844:Lasers, Solid-State; D055620:Optical Phenomena; D019647:Oral Surgical Procedures / Q000009:adverse effects / Q000379:methods; D012680:Sensitivity and Specificity; D012867:Skin / Q000294:innervation / Q000473:pathology; D013552:Swine
keywords: diffuse reflectance spectroscopy; laser ablation; laser surgery guidance; optical nerve identification; remote optical measurement; remote surgical methods; spectra analysis