Low-coherent backscattering spectroscopy for tissue characterization.

Although the phenomenon of coherent backscattering (CBS) in nonbiological media has generated substantial research interest, observing CBS in biological tissue has been extremely difficult. Here we show that the combination of low-spatial-coherence, broadband illumination, and low-temporal-coherence, spectrally resolved detection significantly facilitates CBS observation in biological tissue and other random media with long-transport mean-free path lengths, which have been previously beyond the reach of conventional CBS investigations. Furthermore, we demonstrate that depth-selective, speckle-free, low-coherent backscattering spectroscopy has the potential to diagnose the earliest, previously undetectable, precancerous alterations in the colon by means of probing short light paths.