Autofluorescence spectroscopy for nerve-sparing laser surgery of the head and neck—the influence of laser-tissue interaction
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The use of remote optical feedback systems represents a promising approach for minimally invasive, nerve-sparing laser surgery. Autofluorescence properties can be exploited for a fast, robust identification of nervous tissue. With regard to the crucial step towards clinical application, the impact of laser ablation on optical properties in the vicinity of structures of the head and neck has not been investigated up to now. We acquired 24,298 autofluorescence spectra from 135 tissue samples (nine ex vivo tissue types from 15 bisected pig heads) both before and after ER:YAG laser ablation. Sensitivities, specificities, and area under curve(AUC) values for each tissue pair as well as the confusion matrix were statistically calculated for pre-ablation and post-ablation autofluorescence spectra using principal component analysis (PCA), quadratic discriminant analysis (QDA), and receiver operating characteristics (ROC). The confusion matrix indicated a highly successful tissue discrimination rate before laser exposure, with an average classification error of 5.2%. The clinically relevant tissue pairs nerve/cancellous bone and nerve/salivary gland yielded an AUC of 100% each. After laser ablation, tissue discrimination was feasible with an average classification accuracy of 92.1% (average classification error 7.9%). The identification of nerve versus cancellous bone and salivary gland performed very well with an AUC of 100 and 99%, respectively. Nerve-sparing laser surgery in the area of the head and neck by means of an autofluorescence-based feedback system is feasible even after ER-YAG laser-tissue interactions. These results represent a crucial step for the development of a clinically applicable feedback tool for laser surgery interventions in the oral and maxillofacial region.
KeywordsLaser surgery Autofluorescence Laser-tissue interaction Tissue discrimination Remote feedback Optical sensor
The authors gratefully acknowledge the funding by the ELAN-Funds, University of Erlangen-Nuremberg (AZ:07.03.06.1), and the Erlangen Graduate School in Advanced Optical Technologies (SAOT) by the German National Science Foundation (DFG; AZ: STE 1877/2-1) as part of the Excellence Initiative.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
The experiments presented in the manuscript do not contain studies with human participants or live animals performed by any of the authors. The studies were performed on meat samples taken from the local slaughterhouse. The welfare of animals has not been affected in any kind of way. Neither animal keeping nor intervention on live animals has been conducted. No animals were sacrificed for the sole purpose of this study. All procedures performed in the present study were in accordance with the 1964 Helsinki Declaration and its later amendments. Informed consent was obtained from all authors.
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