Espectroscopia micro-Raman aplicada para o diagnóstico do melanoma cutâneo

• Ano de defesa: 2009
• Autor(a) principal: Bitar, Renata Andrade [UNIFESP]
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de São Paulo (UNIFESP)
• Palavras-chave em Português: Análise espectral Raman; Melanoma; Biometria; Técnicas e procedimentos de laboratório; Diagnóstico por imagem
• Link de acesso: http://repositorio.unifesp.br/handle/11600/9475

Introduction: Pigmented skin lesions evaluation for primary melanoma early diagnosis is based on macro and microscopical analysis by means of preestablished standard histopathology morphological models. However, diagnostic sensitivity and specificity depend on the specialists experiences. Facing this problem, studies concerning about the diagnostic methods automation are being discussed. Optical Biopsy is a experimental technique, which main advantage is that biological samples biochemical characteristics are extracted in a reproducible way, whose interpretation will depend on mathematical algorithms developed exclusively for this purpose. Raman spectroscopy is one of Optical Biopsy techniques, known to be highly compatible for biological systems studies. Raman spectroscopy has been used in the last 10 years in the evaluation of neoplastic lesions to promote diagnosis. Objective: To evaluate the feasibility of preprocessing algorithms for Micro-Raman spectra of normal skin epidermis and cutaneous melanoma classification. Methods: Seven samples of normal skin and six samples of cutaneous melanoma in native were sectioned using a cryostat with 16 μm thick section per sample and distributed on CaF2 slides for Micro-Raman spectral acquisition. A Micro-Raman spectrometer was built with a excitation laser @780 nm, optical circuit composed by lenses, filters, mirrors, optical inverted microscope, and a CCD detector. It was collected 168 spectra of normal skin and 150 of cutaneous melanoma. The classification of the Normal Skin and Melanoma subgroups was performed using Principal Components Analysis and Cluster Analysis, and the diagnostic classification was performed applying Principal Components Analysis and Linear Discriminant Analysis. Results: Vibrational modes assignment was referred to the Raman spectral region from 1200 to 1800 cm-1. Especially at 1260, 1300, 1380, 1440, 1550, 1650 cm-1, the vibrational modes were attributed to nucleic acids, Amide III and lipids, aromatic ring C=C breathing bands of melanin, symmetric CH stretch of lipids and proteins and C=O stretching of proteins and lipids from C=C. The spectral classification and cell allocation was possible for the two groups. For normal skin it was possible find the spectral feature for: corneal layer, keratinocytes, melanocytes and collagen; for melanoma, spectral features were attributed to acral melanoma (keratin), melanoma with high melanocytic pigmentation, hemosiderin pigmentation, inflammatory, necrotic and fibrous tissues. Diagnostic classification was possible with sensitivity between 39.1 % and 100 % and specificity between 54.8 % to 100 %, depending on the subgroups confronted. Conclusion: Spectra aquisition, pre-processing and classification algorithms mehods were viable for histological types diagnosis of cutaneous melanoma.