Biomedical subjects

Changhuei Yang

Publications and source records attributed to Changhuei Yang.

4 recordsLinked to original sources

PubMed2003

Fourier-domain low-coherence interferometry for light-scattering spectroscopy.

We present a novel method for obtaining depth-resolved spectra for determining scatterer size through elastic-scattering properties. Depth resolution is achieved with a white-light source in a Michelson interferometer with the mixed signal and reference fields dispersed by a spectrograph. The spectrum is Fourier transformed to yield the axial spatial cross correlation between the signal and reference fields with near 1-microm depth resolution. Spectral information is obtained by windowing to yield the scattering amplitude as a function of wave number. The technique is demonstrated by determination of the size of polystyrene microspheres in a subsurface layer with subwavelength accuracy. Application of the technique to probing the size of cell nuclei in living epithelial tissues is discussed.

Fourier Analysis↗

PubMed2003

In situ detection of neoplastic transformation and chemopreventive effects in rat esophagus epithelium using angle-resolved low-coherence interferometry.

We present a quantitative study of the nuclear morphometry of epithelial cells in an animal model of esophageal carcinogenesis. Changes in the size and texture of cell nuclei as a result of neoplastic transformation and chemopreventive action are observed in situ using a new optical technique, angle-resolved low-coherence interferometry (a/LCI). The capabilities of a/LCI are demonstrated via quantitative in situ measurements of the nuclear morphometry of basal epithelial cells, approximately 50-100 microm beneath the tissue surface without the need for exogenous contrast agents or tissue fixation. The measurements quantify changes in nuclear size, characterized by average diameter, and nuclear texture, characterized by fractal dimension of the subcellular structures. Using this technique, we observed changes in the morphometry of rat esophageal epithelial cells in response to treatment with the carcinogen N-nitrosomethylbenzylamine. In addition, morphometric changes were observed in the esophagi of rats treated with N-nitrosomethylbenzylamine and two chemopreventive agents, difluoromethylornithine and perillyl alcohol. These agents induced either apoptosis in the basal epithelium (difluoromethylornithine) or both apoptosis and vacuolation of basal epithelial cells (perillyl alcohol). Vacuolation was associated with cellular toxicity. The light-scattering measurements were compared with histological images of the same tissues. The potential of a/LCI as a noninvasive means to investigate the development of epithelial neoplasia and for tracking the efficacy of chemopreventive agents appears high. This technique also may provide a new screening tool for intraepithelial neoplasia.

Animals↗

PubMed2002

Cellular organization and substructure measured using angle-resolved low-coherence interferometry.

We measure the organization and substructure of HT29 epithelial cells in a monolayer using angle-resolved low-coherence interferometry. This new technique probes cellular structure by measuring scattered light, as in flow cytometry, but offers an advantage in that the structure can be examined in situ, avoiding the need to disrupt the cell monolayer. We determine the size distribution of the cell nuclei by fitting measured light-scattering spectra to the predictions of Mie theory. In addition, we obtain information about the cellular organization and substructure by examining the spatial correlations within the monolayer. A remarkable finding is that the spatial correlations over small length scales take the form of an inverse power law, indicating the fractal nature of the packing of the subcellular structures. We also identify spatial correlations on a scale large compared with the size of a cell, indicating an overlying order within the monolayer.

Biophysics↗

PubMed2002

Determination of particle size by using the angular distribution of backscattered light as measured with low-coherence interferometry.

We employ a novel interferometer to measure the angular distribution of light backscattered by a turbid medium. Through comparison of the measured data with the predictions of Mie theory, we are able to determine the size of the scatterers comprising the medium with subwavelength precision. As the technique is based on low-coherence interferometry, we are able to examine the evolution of the angular distribution of scattered light as it propagates into the medium. The effects of multiple scattering as a function of penetration depth in the medium are analyzed. We also present various considerations for extending this technique to determining structural information in biological tissues, such as the effects of a distribution of particle sizes and the need to average out speckle contributions.

Interferometry↗