T-matrix based inverse light scattering analysis using angle resolved low coherence interferometry
Inverse light scattering methods have been applied by several groups as a means to probe cellular structure in both clinical and scientific applications with sub-wavelength accuracy. These methods determine the geometric properties of tissue scatterers based on far field scattering patterns. Generally, structure is determined by measuring scattering over some range of angles, wavelengths, or polarizations and then fitting the observed data to a database of simulated scattering selected from a range of probable geometries. We have developed new light scattering software based on the T-matrix method that creates databases of scattering from spheroidal objects, representing a substantial improvement over Mie theory, a method limited to simulating scattering from spheres. The computational cost of the T-matrix method is addressed through a simple but massively parallel program that concurrently simulates scattering across hundreds of PCs. We are exploring the use of these T-matrix databases in inverting interferometric measurements of angle-resolved scattering from spheroidal cell nuclei using a technique called angle-resolved low coherence interferometry (a/LCI). With a/LCI, we have previously distinguished between healthy and dysplastic tissue in both cell cultures and in ex vivo rat and hamster tissue using Mie theory to measure nuclear diameter. We now present nuclear volume and spheroidal aspect ratio measurements of unstained, living MCF7 cells using the improved T-matrix database to analyze a/LCI data. We achieve measurement accuracy equivalent to conventional image analysis of stained samples. We will further validate the approach by comparing experimental measurements of scattering from polystyrene microspheroids, and show that the T-matrix is a suitable replacement for Mie theory in ex vivo tissue samples. © 2009 PIE.
