Low-coherence enhanced backscattering (LEBS) for bioimaging.

• Main Author: Lim, Noreen Yixuan.
• Other Authors: Lee Kijoon
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Bioengineering; DRNTU::Science::Medicine::Optical instruments
• Online Access: http://hdl.handle.net/10356/50210
• Institution: Nanyang Technological University

Coherent backscattering of light (CBS) is a well-established phenomenon in optics. Conventionally, CBS method is used in fields like astronomy and studies of crystalline structures. CBS phenomenon is observable experimentally as a distinct sharp peak superimposed on a diffused background in the backscattering direction. One key obstacle of using CBS method to probe biological tissues is its extremely narrow cone width. It was observed that replacing the highly coherent laser source in CBS with a broadband light source offers many critical improvements: cone width broadening, depth selective probing, spectroscopic analysis and speckle-reduction. This is due to the spatially finite coherence property of the source illumination. Such a setup is termed low-coherence enhanced backscattering (LEBS). These improvements not only alleviate the limitations of observing CBS, they may also uncover more optical characteristics of the probed tissues. This study focuses on observing the change of LEBS cone width under varying spatial coherent length, Lsc. We first established that increasing cone width at full width half maximum corresponds to increasing transport mean free path length, l* in CBS. A comparison showed that LEBS data displayed a similar trend. Interestingly, we observed that probing of double-layered samples showed the depth-selective nature of LEBS. When data collected is plotted as function of Lsc, the curves reflected the transition of penetration depth from the more highly scattering bottom layer to the less-scattering top layer. These results indicated the potential of using LEBS cone width as a means of tissue diagnostics and can prove useful in detection of field carcinogenesis.