Phase-Sensitive Intracellular Doppler Fluctuation Spectroscopy

Dynamic light scattering from three-dimensional intracellular motions in living tissues or biopsies creates dynamic speckle due to broadband Doppler shifts that are recorded as broadband spectra obtained from speckle fluctuation spectroscopy. Doppler frequency shifts from active intracellular motion extend across three orders of magnitude from 10 mHz to 10 Hz. Biodynamic imaging is a full-field optical coherence tomography technique performed with low-coherence digital holography. The holographic reconstruction allows phase recovery, but mechanical stability limitations favor homodyne detection over heterodyne detection because homodyne is relatively insensitive to phase drift. However, by obtaining phase-displacement distributions from consecutive frames, the phase excursions form a robust probability distribution. The phase-probability density function of the phase-displacement distribution captures average phase displacements over time and is used to reconstruct stable heterodyne spectra. Phase-sensitive biodynamic imaging is applied to detect Levy-stable distributions from living tissue that may reflect heavy-tailed anomalous transport within intracellular media.