Characterizing biochemical and morphological variations of clinically relevant anatomical locations of oral tissue in vivo with hybrid Raman spectroscopy and optical coherence tomography technique

Abstract

This study aims to characterize biochemical and morphological variations of the clinically relevant anatomical locations of in vivo oral tissue (ie, alveolar process, lateral tongue and floor of the mouth) by using hybrid Raman spectroscopy (RS) and optical coherence tomography (OCT) technique. A total of 1049 in vivo fingerprint (FP: 800-1800 cm ) and high wavenumber (HW: 2800-3600 cm ) Raman spectra were acquired from different oral tissue (alveolar process = 331, lateral tongue = 339 and floor of mouth = 379) of 26 normal subjects in the oral cavity under the OCT imaging guidance. The total Raman dataset were split into 2 parts: 80% for training and 20% for testing. Tissue optical attenuation coefficients of alveolar process, lateral tongue and the floor of the mouth were derived from OCT images, revealing the inter-anatomical morphological differences; while RS uncovers subtle FP/HW Raman spectral differences among different oral tissues that can be attributed to the differences in inter- and intra-cellular proteins, lipids, DNA and water structures and conformations, enlightening biochemical variability of different oral tissues at the molecular level. Partial least squares-discriminant analysis implemented on the training dataset show that the integrated tissue optical attenuation coefficients and FP/HW Raman spectra provide diagnostic sensitivities of 99.6%, 82.3%, 50.2%, and specificities of 97.0%, 75.1%, 92.1%, respectively, which are superior to using either RS (sensitivities of 90.2%, 77.5%, 48.8%, and specificities of 95.8%, 72.1%, 88.8%) or optical attenuation coefficients derived from OCT (sensitivities of 75.0%, 78.2%, 47.2%, and specificities of 96.2%, 67.7%, 85.0%) for the differentiation among alveolar process, lateral tongue and the floor of the mouth. Furthermore, the diagnostic algorithms applied to the independent testing dataset based on hybrid RS-OCT technique gives predictive diagnostic sensitivities of 100%, 76.5%, 51.3%, and specificities of 95.1%, 77.6%, 89.6%, respectively, for the classifications among alveolar process, lateral tongue and the floor of the mouth, which performs much better than either RS or optical attenuation coefficient derived from OCT imaging. This work suggests that inter-anatomical morphological and biochemical variability are significant which should be considered as an important parameter in the interpretation and rendering of hybrid RS-OCT technique for oral tissue diagnosis and characterization.

Assessment of the preventive effects of Nd:YAG laser associated with fluoride on enamel caries using optical coherence tomography and FTIR spectroscopy

“…Another optical technique of interest is the Fourier transformed infrared (FTIR) spectroscopy, which may provide qualitative information about the chemical composition of tissues in a non-invasive way at a molecular level, allowing the analysis of structural and chemical changes caused by pathologies, like neoplasia and osteoporosis, aging, and radiation [22]. This optical technique was also successfully used to detect the changes promoted by laser irradiation in hard tissues and to monitor caries and erosion lesions [11,14,23,24].…”

In-vivo Raman spectroscopy: from basics to applications

“…However, the overall probe size of 10.2 × 12.7 × 20.3 cm makes it mainly suitable for skin applications. A side-view hybrid probe for in-vivo real-time measurements was developed, 102,103 making use of the complementary information provided by OCT and Raman spectroscopy. The handheld OCT/RS probe has a length of ∼120 mm with a probe head size of ∼13 mm × 8 mm, making it suitable for in-vivo tissue measurements on human organs, such as the oral cavity, cervix, and skin, or for intraoperative monitoring, e.g., brain surgeries.…”

“…101 In Ref. 103, it was demonstrated that the diagnostic strength of the combination is improved in comparison with Raman spectroscopy or OCT alone. To address the issue of obtaining both morphological and molecular information at depth, a hybrid approach integrating OCT with wavelength modulated spatially offset Raman spectroscopy (WM-SORS) was introduced.…”

“…The authors performed unsupervised classification to identify anatomical differences of the measured sites, whereby the anatomical clustering yielded an overall accuracy of 95%. 197 Wang et al 103 characterized biochemical and morphological changes of clinically relevant locations of oral tissue, i.e., alveolar process, the floor of the mouth, and lateral tongue in vivo by combining Raman spectroscopy with optical coherence tomography (RS-OCT). The study was carried out on 26 healthy volunteers with 1049 Raman spectra acquired from alveolar process (31%), lateral tongue (33%), and floor of mouth (36%).…”

Nonresonant Raman spectroscopy of isolated human retina samples complying with laser safety regulations for in vivo measurements

“…For example, different biomarkers have been identified for monitoring retinal inflammation, 15 and retinal changes occurring in glaucoma were investigated. 16 The combination of morphologically sensitive methods, such as OCT with Raman spectroscopy has been successfully demonstrated on various biological tissues 17 – 20 and could have profound implications for ophthalmology. Initial combinations of those modalities have readily been performed on ex vivo porcine and human retina tissue.…”