In vivo Raman spectroscopic characterization of papillary thyroid carcinoma

Abstract

The increasing incidence of lesions in the thyroid gland requires great attention due to the difficulty of diagnosis in some cases, which often leads to inadequate treatments. The diagnosis is commonly based on clinical perceptions and ultrasonography-guided fine needle aspiration (FNAB), often presenting inconclusive results which may indicate surgery as the main treatment for these cases. Therefore, the need to biochemically characterize the thyroid gland during surgery is extremely important. In this context, Raman spectroscopy is considered as a potential technique for the characterization of structures and identification of neoplasms. This study aimed at structuring and implementing a Raman system for the differentiation between normal and altered tissues in the thyroid gland in vivo. We used a HOLOSPEC f/1.8i system coupled to a laser of 785 nm wavelength and 70 mW power as an excitation source, and a 100 μm optical fiber. The spectra were collected during the surgical procedure under the supervision of the responsible physician, from 8 patients who were diagnosed with papillary thyroid cancer (PTC). Spectral analysis revealed several peaks characteristic of cancer, such as 834, 947, 1255, 1451 and 1601 cm−1. A high similarity was observed between ex vivo and in vivo spectra of papillary carcinomas, confirming the efficacy of the technique in the biochemical identification of the analyzed tissue. In this first phase of study, besides observing that in vivo PTC spectra are compatible with ex vivo PTC obtained in previous studies, it was possible to establish a calibration protocol for the in vivo analysis process. In this way, we conclude that the use of Raman spectroscopy in vivo can aid in the diagnosis of thyroid pathologies, as well as assist the physician during surgical procedures.