Frequency domain coherent backscattering for depth : sensitive tissue measurement.

• Main Author: Wong, Junn Munn.
• Other Authors: Lee Kijoon
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Science::Medicine::Optical instruments
• Online Access: http://hdl.handle.net/10356/50062
• Institution: Nanyang Technological University

Optical phenomenon is studied in bio-imaging field for cancer tissue diagnosis. One potential non-invasive optical method is Coherent Backscattering (CBS). A sharp peak intensity cone which is created through photon self-interference effect in CBS provides us the optical properties such as transport mean-free-path length (ℓ*) of the medium. However, utilization of CBS in biological media faced some limitations in probing multi-layered stratified biological tissue. This project is aimed to carry out the research on application of frequency modulation of laser light as diffuse photon density wave in CBS phenomenon to achieve depth-selective tissue measurement. The gain-modulated image intensifier coupled with charge-coupled device (CCD) camera is the important optical instrument allowing frequency modulation and image acquisition. Experiment using intralipid as sample at different concentrations and thickness shows the frequency dependent change in CBS. This project verifies that 10 MHz modulated light possesses longer penetration wavelength of density wave as compared to 100 MHz and its maximum penetration depth is 6mm and 200μm for liquid and solid intralipid respectively. Frequency-Domain CBS approach exhibits a potential to measure epithelial layer where cancers usually proliferates, by choosing proper modulation frequency. The success of depth-selective Frequency-Domain CBS measurement can be further improved by using tissue-like sample or real biological tissue in the future.