Seminar Date:
Mon, 04/08/2013 - 12:00pm - 1:00pm
Presenter: Aditya Pandaya, MSc Candidate
Supervisors: Dr. Alexandre Douplik & Dr. Carl Kumaradas
Abstract:
Raman spectroscopy provides a biochemical fingerprint of a tissue sample under interrogation utilizing the interaction of light with molecules. The incident photon changes the state of an electron to a virtual excited state following which, the electron falls back to a higher or lower vibrational energy level releasing a new photon. The frequency shift caused by this energy transfer is proportional to a specific vibrational mode of the molecule. Raman spectra can detect individual molecules, are independent of excitation wavelength, and the frequency/energy shifts are denoted in relative wavenumbers (1/wavelength). The probability of Raman process occurring is very miniscule (as low as 1 in a billion). Hence, the traditional challenges of Raman scattering include an inherently weak signal that involve long acquisition times (over tens of seconds or minutes), backgrounds signals arising from fluorescence, sample medium and instrumental differences. Such a long data acquisition time makes application of this accurate technique questionable for diagnostics in upper GI (esophagus and stomach) where high tissue motility leads to severe motion artifacts.
Raman spectroscopy is very sensitive towards small molecular changes that are associated with cancer, such as an increased nucleustocytoplasm ratio, disordered chromatin, higher metabolic activity, and changes in lipid and protein levels. Clinically, Raman spectroscopy has been applied towards diagnosing cancers in the skin, breast, gastrointestinal tract, cervix and others with high sensitivities/specificities (90-99/
89-100). Surface Enhanced Raman Spectroscopy (SERS) is a mechanism proposed in order to enhance the Raman signal intensity. In close proximity to a metallic nanostructure, an enhancement of several orders of magnitude (higher than 10 orders of magnitudes has been reported in the literature) can be achieved. A combination of theoretical simulations and experiments is proposed to design and evaluate a clinically feasible SERS endoscopic architecture. Applying SERS would decrease the time of
acquisition and would make realtime monitoring possible while minimizing the effects of motion artifacts (resulting from peristaltic motion, heart beats, and respiration). Single fiber and multi fiber scanning mechanisms can be employed towards detecting variations in the esophageal and gastric lining. These variations can be characterized and segregated to emphasize malignant and nonmalignant regions even with a background of inflammation or Barrett esophagus metaplasia. Moreover, the wealth of
information contained in the SERS characterization would lead to novel detection techniques which would provide valuable qualitative and quantitative data sets for better diagnosis and improved prognosis based on molecular diagnostics without external labeling.
