Optical scatter imaging: subcellular morphometry in situ with Fourier filtering

We demonstrate a quantitative optical scatter imaging (OSI) technique, base d on Fourier filtering, for detecting alterations in the size of particles with wavelength-scale dimensions. We generate our scatter image by taking t he ratio of images collected at high and low numerical aperture in central dark-field microscopy. Such an image spatially encodes the ratio of wide to narrow angle scatter and hence provides a measure of local particle size. We validated OSI on sphere suspensions and live cells. In live cells, OSI r evealed biochemically induced morphological changes that were not apparent in unprocessed differential interference contrast images. Unlike high-resol ution imaging methods, OSI can provide size information for particles small er than the camera's spatial resolution. (C) 2001 Optical Society of Americ a.