title: Influence of illumination-collection geometry on fluorescence spectroscopy in multilayer tissue.
abstract: Device-tissue interface geometry influences both the intensity of detected fluorescence and the extent of tissue sampled. Previous modelling studies have often investigated fluorescent light propagation using generalised tissue and illumination-collection geometries. However, the implementation of approaches that incorporate a greater degree of realism may provide more accurate estimates of light propagation. In this study, Monte Carlo modelling was performed to predict how illumination-collection parameters affect signal detection in multilayer tissue. Using the geometry and optical properties of normal and atherosclerotic aortas, results for realistic probe designs and a semi-infinite source-detection scheme were generated and compared. As illumination-collection parameters, including single-fibre probe diameter and fibre separation distance in multifibre probes, were varied, the signal origin deviated significantly from that predicted using the semi-infinite geometry, The semi-infinite case under-predicted the fraction of fluorescence originating from the superficial layer by up to 23% for a 0.2mm diameter single-fibre probe and over-predicted by 10% for a multifibre probe. These results demonstrate the importance of specifying realistic illumination-collection parameters in theoretical studies and indicate that targeting of specific tissue regions may be achievable through customisation of the illumination-collection interface. The device- and tissue-specific approach presented has the potential to facilitate the optimisation of minimally invasive optical systems for a wide variety of applications.
authors.affiliation: Center for Devices & Radiological Health, US Food & Drug Administration, Rockville, Maryland, USA. tdp@cdrh.fda.gov
authors.forename: T J
authors.initials: TJ
authors.lastname: Pfefer
authors.forename: L S
authors.initials: LS
authors.lastname: Matchette
authors.forename: R
authors.initials: R
authors.lastname: Drezek
mesh_terms: D001024:Aortic Valve Stenosis / Q000175:diagnosis*; D004867:Equipment Design; D005336:Fiber Optic Technology / Q000295:instrumentation; D006801:Humans; D008029:Lighting / Q000379:methods*; D009010:Monte Carlo Method; D013050:Spectrometry, Fluorescence / Q000295:instrumentation*