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Fluorescence Measurements for Noninvasive Skin Assessment and Diagnosis

Haishan Zeng, MD University of British Columbia, Vancouver, BC

Autofluorescence properties of tissues can be exploited for non-invasive dermatology diagnosis and for skin tissue characterization. Past studies have concentrated on tissue autofluorescence excited by UV and short wavelength visible (VIS) light. We have recently found interesting fluorescence properties from melanin, a skin chromophore responsible for UV protection and for skin color.
Melanin exhibits strong fluorescence emission in the near infrared (NIR) wavelength bands when excited by 785 nm NIR light, while in the VIS band melanin fluorescence is weak. The NIR fluorescence behavior of melanin is also confirmed in healthy and diseased skin.
These observations lead to this proposal to build a new device to study skin autofluorescence properties in the longer wavelength VIS and NIR bands. This optical device is called VIS/NIR fluorescence EEM spectroscopy system.
Previous EEM devices working in the UV/VIS bands and need a few minutes to obtain a complete spectral set. Such a long measurement time causes patient discomfort and motional artifacts to data collection.
We will build a fast EEM device not only working in the VIS/NIR bands but also with a data acquisition time of less than a second by utilizing a fast electronic tunable band pass filter called AOTF. This new device may be particularly beneficial to the diagnosis of pigmented skin lesions including melanoma because melanin in these lesions will be lighted up by red/NIR fluorescence, while at UV and short wavelength VIS range, melanin acts like a photon absorbing "black hole" masking out any useful fluorescence or reflectance signatures.

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