Coherent backscattering spectroscopy: A new technique for probing short transport paths in living tissues and early precancer detection

Coherent backscattering (CBS) is a photon weak-localization phenomenon that gives rise to an enhanced backscattering of light by random media. Although this effect has been previously studied in nonbiological media, there have been only few attempts to use CBS for diagnosis and characterization in living tissue. Here we report spectroscopic CBS measurements - low-coherence CBS spectroscopy - by combining broadband illumination and low-coherence detection. We demonstrate that low-coherence CBS spectroscopy substantially simplifies CBS measurements in biological tissue and enables depth-resolved spectroscopic analysis of CBS. Low-coherence CBS spectroscopy may find important applications in probing biological tissue where depth-selective measurements are crucial. As an example of the potential of CBS for tissue diagnosis, we show that low-coherence CBS spectroscopy can be used to detect the earliest, previously undetectable, preadenomatous stages of colorectal carcinogenesis.