Optical nerve identification in head and neck surgery after Er:YAG laser ablation

Abstract

Facial nerve function may be hampered by iatrogenic damage during head and neck laser surgery procedures. Optical techniques can serve as a basis for feedback-controlled tissue-specific laser surgery on the jaw bone and the parotid gland. In order to preserve nerve tissue during laser surgery, the alteration of optical tissue properties through laser-tissue interactions have to be taken into account. It was the aim of this study to evaluate the viability of optical tissue differentiation through diffuse reflectance spectroscopy after exposure to laser light as a basis for a feedback system for tissue-specific laser surgery. Spectra of diffuse reflectance (wavelength, 350-650 nm) of nerves, salivary glands, and cortical and cancellous bone of the midfacial region (ex vivo domestic pig heads) were acquired before/after Er:YAG laser (wavelength, 2.94 μm) ablation (each 16,800 spectra). Principal component analysis was computed followed by quadratic discriminant analysis. The tissue classification performance as well as area under the curve (AUC) sensitivity and specificity for tissue differentiation was assessed before and after laser-tissue exposure. A high classification performance was observed before laser ablation (total error, 7.74%). Nerve tissue was differentiated from bone and salivary glands with results greater than 0.96 in AUC, sensitivity and specificity. After laser exposure, a total classification error of 18.61% was observed. The differentiation of nerve tissue was reduced with an AUC of >0.94, sensitivity of >0.95, and specificity >0.87. Er:YAG laser ablation only slightly reduces the differentiation performance through diffuse reflectance in the investigated tissue types. The results show the general viability of diffuse reflectance spectroscopy in identifying neural structures in the vicinity of salivary glands and bone as a basis for nerve preservation during feedback-controlled laser surgery.

Nerve detection using optical spectroscopy, an evaluation in four different models: In human and swine, in‐vivo, and post mortem

“…The potential of optical techniques to identify nervous tissue was demonstrated by several authors . Nerve tissue was discriminated between several surrounding tissue including bone and glandular tissue , muscle and adipose tissue , and blood vessel . All these studies show good classification results, but none of them reaches perfect (100%) tissue identification.…”

“…Both the quantified absorbers and the scattering parameters are used for further tissue identification. A number of studies show the potential of nerve identification using diffuse reflectance spectroscopy . Two in vivo human studies are published but both were performed with a small number of measurements .…”

Investigation of the differentiation ofex vivonerve and fat tissues using laser-induced breakdown spectroscopy (LIBS): Prospects for tissue-specific laser surgery

“…Here, the identification and preservation of nerve tissue is perhaps the most critical challenge. In previous studies, our group has investigated the differentiation between several tissue types, at times specifically highlighting the nerve recognition and nerve-fat pair differentiation performance [23][24][25][26][27][28][29]. The challenge posed by this particular pair results from the peripheral nerve fiber's myelin cover.…”

Does Laser Surgery Interfere with Optical Nerve Identification in Maxillofacial Hard and Soft Tissue?—An Experimental Ex Vivo Study

“…In this part of the project, the general feasibility of optical tissue differentiation by diffuse reflectance spectroscopy (DRS) was demonstrated on five different tissue types in an ex vivo setting [ 31 ]. Additionally, it was shown that DRS is an adequate technique for nerve identification in the vicinity of bone and salivary gland [ 32 , 33 ]. In a second step, the viability of tissue identification was proven after the tissue was altered by laser ablation, focusing on nerve detection [ 33 , 34 ].…”

“…Additionally, it was shown that DRS is an adequate technique for nerve identification in the vicinity of bone and salivary gland [ 32 , 33 ]. In a second step, the viability of tissue identification was proven after the tissue was altered by laser ablation, focusing on nerve detection [ 33 , 34 ]. In a third step, the promising ex vivo results could be successfully transferred to an in vivo setup in rats [ 35 ].…”