Performance evaluation of fiber optic probes for tissue lifetime fluorescence spectroscopy

The design of fiber-optic probes plays an important role in optical spectroscopic studies, including fluorescence spectroscopy of biological tissues. It can affect the light delivery and propagation into the tissue, the collection efficiency (total number of photons collected vs. total number of photons launched) and the origin of collected light. This in turn affects the signal to noise ratio (SNR) and the extend of tissue interrogation, thus influencing the diagnostic value of such techniques. Three specific fiber-optic probe designs were tested both experimentally and computationally via Monte Carlo simulations. In particular, the effects of probe architecture (single-fiber vs. two bifurcated multifiber probes), probe-to-target distance (PTD), and source-to-detector separation (SDS) were investigated on the collected diffuse reflectance of a Lambertian target and an agar-based tissue phantom. This study demonstrated that probe architecture, PTD, and SDS are closely intertwined and considerably affect the light collection efficiency, the extend of target illumination, and the origin of the collected reflected light. Our findings can be applied towards optimization of fiber-optic probe designs for quantitative fluorescence spectroscopy of diseased tissues.