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Title:Tissue Spectroscopy and Tomography Using Quantitative Phase Imaging
Author(s):Zhu, Ruoyu
Contributor(s):Popescu, Gabriel
medical imaging
tissue imaging
tissue spectroscopy
quantitative phase imaging
Abstract:In quantitative phase imaging (QPI), we measure the optical pathlength map associated with a transparent specimen which relates to useful structure and dynamics information of cells and tissues. Using this capability of QPI, we studied the correlation-induced spectral changes, i.e. the Wolf effect, in human tissue, which can affect any spectroscopy measurements. This spectral shift in tissue is due to elastic scattering whereby different wavelengths are scattered with different strength depending on the scattering angles. Our result shows that the overall spectral shift is to the red and the mean wavelength is shifted up to 10% and more. Thus, these significant spectral shifts can confuse the data generated by common (chemical) spectroscopy. Therefore, simultaneous morphology and spectral measurements are required for accurate spectroscopic measurements. We also show that in addition to the change of spectral mean wavelength, the temporal coherence of the propagated field also changes along different scattering angles. As an extension of this project, we applied QPI for tomographic reconstruction of transparent specimens such as live cells. Current methods such as confocal microscopy and deconvolution microscopy render significant results but are invasive because they require fluorophores to be attached to the structure of interest. Thus, we propose a QPI-based method that uses a stack of two-dimensional images, acquired from a scan in axial direction with same sampling as transverse direction, and reconstruct via the Helmholtz equation. Out method, Helmholtz phase tomography (HPT), allows 4D imaging of cells (3D in space, 1D in time) over arbitrary time scales, which is currently impossible.
Issue Date:2012-05
Publication Status:unpublished
Peer Reviewed:not peer reviewed
Date Available in IDEALS:2014-01-09

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