Real-time Interferometric Synthetic Aperture Microscopy:
Inverse Scattering for Optical Coherence Tomography
Dr. Tyler S. Ralston, University of Illinois at Urbana-Champaign
Abstract:
State-of-the-art methods in high-resolution three-dimensional (3-D)
optical microscopy require that the focus be scanned through the entire
region of interest. It is believed that features outside of the focus
are inherently unresolvable. Here, a novel computational image-formation
technique called interferometric synthetic aperture microscopy (ISAM)
is described and demonstrated. A mathematical model is developed
connecting the experimentally acquired signal with the three-dimensional
object structure, taking into account the finite beam width, diffraction
and defocus effects. Using this model, the analytic solution to the
inverse scattering problem for coherence microscopy is derived. Through
implementation, resolution produced by conventional coherence microscopy
at the focus can be achieved for all planes outside of the focus.
Explicitly, the structure of an object is determined using all the data
collected from the illuminated volume. Numerical simulations show that
scatterers can be resolved outside of the confocal volume. Verification
with a tissue phantom and human breast tissue demonstrate spatially
invariant resolution. These results improve the high-resolution
cross-sectional imaging capabilities for 3-D microscopy. Furthermore,
the reconstruction algorithm may be implemented for either
cross-sectional images or full 3-D volumes, and because of the modest
computational complexity of this technique, ISAM is amenable to real-time
imaging.
Bio:
Dr. Tyler S. Ralston was born in Dayton, Ohio, in 1977. He received
his Bachelors from the Electrical and Computer Engineering Department
at the University of Dayton in 2000. Following his degree, he worked
in the medical products sector at Battelle Memorial Institute in
Columbus, Ohio, earning a Key Contributor award for production of a
medical instrument. He received his Masters and Ph.D. from the
Electrical and Computer Engineering Department at the University of
Illinois at Urbana-Champaign. During his PhD, he held a fellowship at
the Beckman Institute for Advanced Science and Technology. He now is
a postdoctoral research associate at the same institution. His
research interests include both signal processing and inverse problems
for optical biomedical imaging.
Dr. Ralston has served on the board for the University of Illinois
chapters of the IEEE and the OSA as president, vice president, and
treasurer.