Tissue Discrimination by Uncorrected Autofluorescence Spectra: A Proof-of-Principle Study for Tissue-Specific Laser Surgery

Abstract

Laser surgery provides a number of advantages over conventional surgery. However, it implies large risks for sensitive tissue structures due to its characteristic non-tissue-specific ablation. The present study investigates the discrimination of nine different ex vivo tissue types by using uncorrected (raw) autofluorescence spectra for the development of a remote feedback control system for tissue-selective laser surgery. Autofluorescence spectra (excitation wavelength 377 ± 50 nm) were measured from nine different ex vivo tissue types, obtained from 15 domestic pig cadavers. For data analysis, a wavelength range between 450 nm and 650 nm was investigated. Principal Component Analysis (PCA) and Quadratic Discriminant Analysis (QDA) were used to discriminate the tissue types. ROC analysis showed that PCA, followed by QDA, could differentiate all investigated tissue types with AUC results between 1.00 and 0.97. Sensitivity reached values between 93% and 100% and specificity values between 94% and 100%. This ex vivo study shows a high differentiation potential for physiological tissue types when performing autofluorescence spectroscopy followed by PCA and QDA. The uncorrected autofluorescence spectra are suitable for reliable tissue discrimination and have a high potential to meet the challenges necessary for an optical feedback system for tissue-specific laser surgery.

Machine learning classification of human joint tissue from diffuse reflectance spectroscopy data

“…The classification accuracy was above 99% using this technique. This accuracy is similar to that achieved by Stelzle et al [38] where Principle Component Analysis (PCA) and Quadratic Discriminant Analysis (QDA) were used to achieve 94.8% accuracy on 12,150 pig tissue measurements. However, our method learned a comparable level of accuracy from approximately 4 times fewer measurements.…”

Compatibility of CO2 laser surgery and fluorescence detection in head and neck cancer cells

“…However, the in vivo fluorescent signal from an oral tumor targeted with BIWA‐IRDye800CW was approximately 10 4 times higher as the caused autofluorescence detected in tumor‐free skin after laser exposure (Figure B). Because autofluorescence is tissue specific, autofluorescence originating from the floor‐of‐mouth was also tested and compared to the signal intensity reached by BIWA‐IRDye800CW. Single treatment of the floor‐of‐mouth with 2 W for 0.5 seconds did not cause detectable autofluorescence using the detection settings used for the oral tumor (Figure B) Differences in the autofluorescence signals from the mouse skin and the floor‐of‐mouth are likely due to variations in tissue structure .…”

“…Because autofluorescence is tissue specific, autofluorescence originating from the floor‐of‐mouth was also tested and compared to the signal intensity reached by BIWA‐IRDye800CW. Single treatment of the floor‐of‐mouth with 2 W for 0.5 seconds did not cause detectable autofluorescence using the detection settings used for the oral tumor (Figure B) Differences in the autofluorescence signals from the mouse skin and the floor‐of‐mouth are likely due to variations in tissue structure . In conclusion, CO 2 laser‐dependent autofluorescence is unlikely to interfere with strong NIR signals, but weak NIR signals may be obscured, as described …”

Combined Nd:YAG and Er:YAG lasers for real-time closed-loop tissue-specific laser osteotomy

“…In order to preserve the adjacent soft tissue, several approaches to such differentiation have been developed using the optical properties of the ablated tissues. These methods include optical coherence tomography (OCT) [12,13], Raman spectroscopy [14][15][16][17], autofluorescence spectroscopy [18,19], diffuse reflectance spectroscopy (DRS) [20][21][22][23], ablative optoacoustic techniques [24][25][26][27][28][29], random lasing [30], laser-induced breakdown spectroscopy (LIBS) [31][32][33][34][35][36][37][38][39][40][41][42], and combustion/pyrolysis light analysis [43,44]. However, many of these methods have not been tested in combination with an ablating laser; studies have focused on tissue differentiation only.…”