A study of spectral domain optical coherence tomography and photoacoustic microscopy for biometric and biomedical applications

Abstract

Optical coherence tomography (OCT) has been widely used in biomedical imaging ever since its introduction. However, the application of OCT for biometrics is relatively new. This thesis demonstrates the feasibility of applying a spectral domain optical coherence tomography (SD-OCT) system to fingertip biometric information retrieval. The results show that SD-OCT is capable of retrieving Level 3 fingertip information. Combined with traditional Level 1 and 2 fingerprint information, which can also be easily acquired by SD-OCT, the proposed application shows potential for ultra-secure scenarios. Photoacoustic microscopy (PAM) is another imaging modality gaining considerable interest in the past decade. Different than OCT, it employs ultrasound detection for optically induced thermal expansion in tissue. Bovine articulate cartilage samples are imaged with a single wavelength PAM system using India ink as a contrast agent. The same samples were also imaged with SD-OCT. Image analysis shows that PAM produces excellent contrast between intact and fibrillated regions in cartilage while SD-OCT visualizes topological changes with fine spatial resolution. A spectroscopic PAM system is also developed using a tunable source based on supercontinuum generation in a photonic crystal fiber. Imaging experiments of tissue phantoms demonstrate the ability to differentiate various chromophores with unique absorption characteristics. Another spectroscopic PAM system is currently being developed, where the tunable source is based on stimulated Raman scattering. This new system is being studied and some preliminary results are given to demonstrate its advantages over the supercontinuum approach.