“Spatial light interference microscopy and tomography”
Friday, April 16, 2010
Department of Electrical and Computer Engineering Beckman Institute for Advanced Science and Technology University of Illinois at Urbana-Champaign
Quantifying optical path-length shifts across specimens offers a new dimension to imaging, which reports on both the refractive index and thickness distribution with very high accuracy. Here we present spatial light interference microscopy (SLIM), a new optical method, capable of measuring optical path-length changes of 0.3 nm spatially (i.e. point to point change) and 0.03 nm temporally (i.e. frame to frame change). SLIM combines two classic ideas in light imaging: Zernike’s phase contrast microscopy and Gabor’s holography. The resulting topographic accuracy is comparable to that of atomic force microscopy, while the acquisition speed is 1,000 times higher. Due to the micron-scale coherence length of the illuminating field, SLIM provides high axial resolution optical sectioning. Using a 3D complex field deconvolution operation, we render tomographic refractive index distributions of live, unstained cells. We illustrate the novel insight into cell functioning to be gained using SLIM by experiments on dynamics of primary brain cells, i.e. neurons, glial and microglial cells. In an exciting new development, we showed that scattering parameters of tissues, i.e. mean free path and anisotropy factor, respectively, can be extracted from the variance and gradient of the phase associated with a thin tissue slice. We believe that SLIM may become an important method not only for basic research of cell function but also for clinical applications, including label-free blood screening and cancer detection.
Gabriel Popescu received the B.S. and M.S. in Physics from University of Bucharest, in 1995 and 1996, respectively. He obtained his M.S. in Optics in 1999 and the Ph.D. in Optics in 2002 from the School of Optics/ CREOL (now the College of Optics and Photonics), University of Central Florida. Dr. Popescu continued his training with the G. R.
Harrison Spectroscopy Laboratory at M.I.T., working as a postdoctoral associate. He joined UIUC in August 2007. He is an Assistant Professor in the Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign and holds a full faculty appointment with the Beckman Institute for Advance Science and Technology. He is also an affiliate faculty in the Bioengineering Department.
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Dr. Aristide Dogariu