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Raman spectroscopy for optical diagnosis in head and neck tissue Lau, David Pang Cheng

Abstract

Background and Aims: Raman spectroscopy (RS) uses light to detect vibrational characteristics of molecules and can distinguish different molecular structures. Extrapolating this to a medical setting, it was hypothesized that RS could be used to make a tissue diagnosis if it could detect molecular changes associated with tissue pathology. The main aims of this study were to determine whether: 1. Raman spectra could be obtained rapidly in-vitro from head and neck tissue, and 2. Differences could be detected between benign and malignant tissue in various sites in the head and neck. Methodology: A Raman spectrometer with 785nm excitation laser and a charge-coupled device detector was used to acquire spectra in-vitro from nasopharyngeal, laryngeal and thyroid tissue. Spectral acquisition times ranging from 1 to 30 seconds were studied. Spectra from benign and malignant tissue in the different sites were compared using statistical techniques, with histopathology as the "gold-standard" for diagnosis. Results: Good quality spectra were acquired within 5 seconds. Paired analysis of nasopharyngeal specimens (n=6) showed significant differences between benign and malignant tissue at 1297-1305, 1377-1381, 1436-1442, 1541-1555, and 1614-1626cm⁻¹. Paired thyroid tissue analysis (n=5) showed differences at 1264-1266 and 1477cm⁻¹. Unpaired analysis using multivariate statistical techniques showed sensitivity and specificity values in differentiating benign and malignant tissue of 83.3% and 72.7% for nasopharynx (n=23), 69.2% and 94.1% for larynx (n=47), and 86.7% and 70.0% for thyroid (n=65). In addition in the larynx, squamous papilloma could be distinguished from normal tissue and carcinoma with sensitivity and specificity of 87.5% and 93.5% respectively. Conclusions: The system could acquire spectra rapidly in-vitro and has potential for in-vivo application in the head and neck, although specialized probes will need to be developed for this purpose. Spectral differences were detected between benign and malignant tissue in the nasopharynx, larynx and thyroid. Although diagnostic sensitivity and specificity are currently lower than histopathology, they are sufficiently high to warrant further study of this technique as a means of achieving non-invasive tissue diagnosis. Other areas requiring further development include evaluation of wider spectral ranges and characterization of spectra at cellular and biochemical levels.

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