Application of Mie theory to determine the structure of spheroidal scatterers in biological materials

We present here the results of a numerical study on light scattering from nonspherical particles with relevance to detecting precancerous states in epithelial tissues. In previous studies of epithelial cell nuclei, the experimental light scattering data have been analyzed by comparison with Mie theory. However, given the spheroidal shape of many cell nuclei, the validity of this assumption demands a thorough investigation. We investigate this assumption by using the T-matrix method to model light scattered from spheroids with parameters relevant to epithelial cell nuclei. In our previous studies, we have developed a data analysis procedure that extracts the oscillatory component of the angular-scattering distribution for an ensemble of epithelial cell nuclei for comparison with Mie theory. We demonstrate that application of our analysis procedure to the predictions of the T-matrix method for spheroids, oriented such that their axis of symmetry is aligned with the incident light propagation direction, generally yields the spheroid dimension that is transverse to the incident light propagation direction with subwavelength accuracy.     

Fourier-domain angle-resolved low coherence interferometry through an endoscopic fiber bundle for light-scattering spectroscopy

We present a novel endoscopic fiber bundle probe incorporated in a Fourier-domain angle-resolved low coherence interferometry system for the measurement of depth-resolved angular scattering distributions to permit the determination of scatterer size via elastic scattering properties. Depth resolution is achieved with a superluminescent diode via a Mach-Zehnder interferometer. The sample is illuminated with a collimated beam, and a Fourier plane image of the backscattered light is collected by a coherent fiber bundle. The angular scattering distribution relayed by the fiber bundle is mixed with the reference field and made to coincide with the input slit of an imaging spectrograph. The data collected are processed in real time, producing a depth-resolved angular scattering distribution in 0.37 s. The data are used to determine the sizes of polystyrene microspheres with subwavelength precision and accuracy.     

Application of the T-matrix method to determine the structure of spheroidal cell nuclei with angle-resolved light scattering

We demonstrate an inverse light-scattering analysis procedure based on using the T-matrix method as a light-scattering model. We measure light scattered by in vitro cell monolayers using angle-resolved low-coherence interferometry (a/LCI) and compare the data to predictions of the T-matrix theory. The comparison yields measurements of the equal volume diameter and aspect ratio of the spheroid cell nuclei with accuracy comparable to quantitative image analysis of fixed and stained samples. These improvements represent a significant upgrade for the a/LCI technique, expanding both the range of tissue in which it is applicable and potentially increasing its value as a diagnostic tool.