Light scattering methods for assessing structural properties of cells and tissues quantitatively measure
morphometric parameters directly without the need for staining. We demonstrate an optical scattering filtering method
used in a biological setting that is sensitive to quantifying object orientation and aspect ratio. These parameters are
measured in cells both sensitive to and resistant to mitochondrial-mediated apoptosis, the latter having been
demonstrated to have shorter mitochondria than apoptosis competent cells. The implementation of the digital
micromirror device (DMD) allows for robust filtering of the scatter data, which we implement with Gabor-like filters
chosen for their ability to intelligently confine the filter response both in the image and in the scatter regimes. By
strategically applying Gabor-like filters to the specific frequencies and orientations in the scatter data, relative changes in
object size, orientation and aspect ratio may be derived. Furthermore, using a DMD and filtering the optical scatter data
in analog allows us to decouple image resolution from frequency resolution and measure these parameters with high
sensitivity for objects within the resolution of the optical system despite an undersampled, lower resolution digital
image. As a result, this measurement may be made at lower magnifications with higher throughput and ultimately on a
larger population of living and unstained cells imaged simultaneously.
Optical scatter imaging (OSI) was developed to non-invasively track real-time changes in particle morphology with submicron
sensitivity in situ without exogenous labeling, cell fixing, or organelle isolation. For spherical particles, the
intensity ratio of wide-to-narrow angle scatter (OSIR, Optical Scatter Image Ratio) was shown to decrease monotonically
with diameter and agree with Mie theory. In living cells, we recently reported this technique is able to detect
mitochondrial morphological alterations, which were mediated by the Bcl-xL transmembrane domain, and could not be
observed by fluorescence or differential interference contrast images. Here we further extend the ability of morphology
assessment by adopting a digital micromirror device (DMD) for Fourier filtering. When placed in the Fourier plane the
DMD can be used to select scattering intensities at desired combination of scattering angles. We designed an optical
filter bank consisting of Gabor-like filters with various scales and rotations based on Gabor filters, which have been
widely used for localization of spatial and frequency information in digital images and texture analysis. Using a model
system consisting of mixtures of polystyrene spheres and bacteria, we show how this system can be used to sort particles
on a microscopic slide based on their size, orientation and aspect ratio. We are currently applying this technique to
characterize the morphology of subcellular organelles to help understand fundamental biological processes.
In this paper we present a robust method for segmenting and tracking cardiac contours and tags in 4D cardiac MRI tagged images via spatio-temporal propagation. Our method is based on two main techniques: the Metamorphs Segmentation for robust boundary estimation, and the tunable Gabor filter bank for tagging lines enhancement, removal and myocardium tracking. We have developed a prototype system based on the integration of these two techniques, and achieved efficient, robust segmentation and tracking with minimal human interaction.
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