Single fiber reflectance spectroscopy calibration (Conference Presentation)

Broadband fiberoptic spectroscopy is investigated for diagnostic applications, based on its ability to noninvasively determine tissue scattering and absorption properties. Spectroscopic instrumentation requires a calibration to account for wavelength dependent factors that may vary, such as the output of the light source, fiberoptic coupling efficiency, ambient light, fiber transmission and detector sensitivity. For techniques such as Diffuse Reflectance Spectroscopy (DRS), a relative calibration of the reflectance is sufficient. For Single Fiber Reflectance spectroscopy (SFR), however, the measured absolute reflectance, R is related to the sample optical properties. Consequently, in order to extract tissue optical properties using SFR, an absolute calibration of the reflectance is required. We investigated two novel SFR calibration methods, using a calibrated mirror and using the Fresnel reflection at the measurement fiber tip as a reference. We compared these to commonly used calibration methods, using either Intralipid-20% in combination with Monte Carlo simulations or Spectralon as a reference. The Fresnel reflection method demonstrated the best reproducibility and yielded the most reliable result. We therefore recommend the Fresnel reflection method for the absolute reflectance calibration of SFR.