Oblique-Incidence Reflectometry and Spectroscopy

Using an optical-fiber reflectometer composed of a light source and an optical fiber bundle we have been able to measure tissue optical properties and detect skin cancers ("optical biopsy") in vivo non-invasively and quickly. In vivo experimental evidence has shown that cancerous skin lesions have different optical properties from non-cancerous lesions or normal skin. Therefore, cancerous skin lesions may be differentiated from non-cancerous skin lesions by comparing the optical properties of the skin lesions with those of the surrounding normal skin sites. The optical properties of the normal skin sites are used to account for different types of skin or different areas of skin.

Skin cancer is the most frequently occurring cancer. Each year over 500,000 new cases of skin cancer are detected. For a high percentage of skin cancers, fatalities can be all but eliminated and morbidity reduced if the cancer is detected early and treated properly. These skin lesions are distinguished generally by subjective visual inspection, and their definitive diagnosis requires time-consuming histopathological evaluation of excisional or incisional biopsies. The devices we have developed, which improve the abilities of the physician's eye, can facilitate early screening and detection of skin cancers to maximize cure and reduce or even avoid unnecessary biopsies. Furthermore, these devices are portable and relatively inexpensive. Therefore, they can be used in remote rural areas, and the diagnostic results can be easily transferred to metropolitan diagnostic centers for expert prognosis if needed.

In the optical-fiber reflectometer, an optical beam is delivered to the skin surface through a source optical fiber, and the light reflectance pattern is transmitted via modems or even via the information superhighway in the near future (telemedicine) through a fiber bundle to a computer. The computer will deduce the reduced scattering coefficient and absorption coefficient of the skin area quickly at multiple wavelengths, based on our patented oblique incidence reflectometry technique. The optical-fiber reflectometer is easy to use, inexpensive, and has the potential to be used with endoscopes for gastrointestinal applications.

The following graph shows the anisotropy in the optical properties of chicken breast tissue, measured using oblique incidence reflectometry.

1. Garcia-Uribe, A.; Balareddy, K. C.; Zou, J.; Wang, L. V.; "Micromachined fiber optical sensor for in vivo measurement of optical properties of human skin," IEEE Sensors 8(10) 1698-1703 (2008) [PDF]
   
2. Garcia-Uribe, A.; Kehtarnavaz, N.; Marquez, G.; Prieto, V.; Duvic, M.; Wang, L. V.; "Skin cancer detection by spectroscopic oblique-incidence reflectometry: classification and physiological origins," Applied Optics 43(13) 2643-2650 (2004) [PDF]
   
3. Mehrubeoglu, M.; Kehtarnavaz, N.; Marquez, G.; Duvic, M.; Wang, L. V.; "Skin lesion classification using oblique-incidence diffuse reflectance spectroscopic imaging," Applied Optics 41(1) 182-192 (2002) [PDF]
   
4. Marquez, G.; Wang, L. V.; "White light oblique incidence reflectometer for measuring absorption and reduced scattering spectra of tissue-like turbid media," Optics Express 1(13) 454-460 (1997) [PDF]
   
5. Lin, S. P.; Wang, L. V.; Jacques, S. L.; Tittel, F. K.; "Measurement of tissue optical properties by the use of oblique-incidence optical fiber reflectometry," Applied Optics 36(1) 136-143 (1997) [PDF]
   
6. Wang, L. V.; Jacques, S. L.; "Use of a laser beam with an oblique angle of incidence to measure the reduced scattering coefficient of a turbid medium," Applied Optics 34(13) 2362-2366 (1995) [PDF]