In vivo Raman spectroscopy has been utilized for non-invasive, nondestructive assessment of tissue pathology or physiological state in a variety of applications largely through the continued development of fiber optic probes to interface with samples of interest. Fiber optic probes can be designed to optimize collection of Raman-scattered photons from application-dependent depths, and this critical consideration should be addressed when planning a study. Herein we investigate four unique probe geometries for sensitivity to superficial and deep signals through a Monte Carlo model that incorporates Raman scattering and fluorescence for the first time. Experimental validation was conducted using biological tissues and TiO2 and polytetrafluoroethylene (PTFE) phantoms, with the intention of more accurately recapitulating in vivo performance scenarios. The behavior of each probe design evaluated (unmodified collection, Gaser, superficially focused micro lens, and deep focused micro lens) was modeled and demonstrated strong correlation with experimental results obtained through biological tissue and phantom testing. Testing in biological tissues revealed that superficially focused micro lens and Gaser designs had superior performance at shallow depths (< 1 mm), whereas the deep focused design yielded the highest signals deep within tissue. The probes demonstrated similar performance for TiO2 and PTFE experiments at all depths investigated. The contrast in results between the TiO2/PTFE and biological tissues underscores the importance of incorporating the optical properties of a given application when designing a fiber optic probe, as the high reduced scattering coefficients of the synthetic phantoms negated the benefits of beveling and lenses that were originally optimized for use in air. The model presented here can be easily extended for optimization of entirely novel probe designs prior to fabrication, reducing time and cost while improving data quality.
|Advisor:||Mahadevan Jansen, Anita|
|Commitee:||Herline, Alan J., Jansen, E. Duco, Mahadevan-Jansen, Anita, Shyr, Yu, Wilson, Keith T.|
|School Location:||United States -- Tennessee|
|Source:||DAI-B 80/08(E), Dissertation Abstracts International|
|Keywords:||Inflammatory bowl disease, Medical devices, Monte Carlo model, Raman spectroscopy, Tissue characterization, Tissue diagnostics|
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