Chrysanthe Preza, D.Sc.Research Associate in the Electronic Systems and Signals Research Laboratory (ESSRL). Affiliated with the Three Dimensional Microscopy Laboratory. Degrees: B.S. (cum laude) in Electrical Engineering and Computer Science (1987), M.S. in Electrical Engineering (1990), M.S. in Computer Science (1991), D.Sc. in Electrical Engineering (1998), Washington University, St. Louis, MO. Curriculum Vitae: [PS file] [PDF file]
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Research Interests:
Research interests include imaging science and estimation theory with applications in:
Hyperspectral Imaging Differential Interference
Contrast (DIC) microscopy Computational
Optical Sectioning Microscopy Fluorescence Microscopy XCOSM
- free software package for processing images acquired with fluorescence
microscopy
Depth-variant maximum-likelihood restoration for three-dimensional fluorescence microscopy,
[PS file]
[PDF file]
Image estimation accounting for point-spread function depth variation in three-dimensional fluorescence microscopy,
[PS file]
[PDF file]
Authors: C. Preza, J.A. Conchello
Presented at 3D and Multidimensional Microscopy: Image Acquisition
and Processing X, Proc. SPIE, volume 4964, No. 27, 2003.
Spectrum Estimation from Quantum-Limited Interferograms,
[PS file]
[PDF file]
Authors:D.R. Fuhrmann, C. Preza, J.A. O'Sullivan, D.L. Snyder, W.H. Smith
IEEE Transactions on Signal Processing, accepted for publication (2003)
Biological Image Restoration in Optical-Sectioning Microscopy Using Prototype Image Constraints,
[PDF file]
Authors: M.R.P. Homem, N.D.A. Mascarenhas, L.F. Costa, and C. Preza,
Real-Time Imaging, Vol. 8, pp. 475-490, (2002)
Rotational-diversity phase
estimation from differential-interference-contrast microscopy images,
[PS file]
Authors: C. Preza,
JOSA A, Vol. 17, No. 3, 415-424 (2000)
Theoretical development
and experimental evaluation of imaging models for differential-interference-contrast
microscopy, [PS
file][PDF
file]
Authors: C. Preza, D. L. Snyder, J.-A. Conchello
JOSA A, Vo. 16, No. 9, 2185-2199 (1999)
Phase Estimation Using
Rotational Diversity For Differential Interference Contrast Microscopy,
[PS
file][PDF
file]
Author: C. Preza
Date: August 1998
Length: 213 Pages
D.Sc. thesis, Washington University, Sever Institute of Technology,
St. Louis, MO, August, 1998
Determination of Direction-Independent
Optical Path-Length Distribution of Cells Using Rotational Diversity
Transmitted-Light Differential Interference Contrast (DIC) Images,
[PS
file][PDF file]
Authors: C. Preza, E. B. van Munster, J. A. Aten, D.
L. Snyder, F. U. Rosenberger,
Date: January 1998
Length: 11 Pages
Presented at 3D and Multidimensional Microscopy: Image Acquisition
and Processing V, Proc. SPIE, volume 3261, 60-70, 1998
Phase Estimation From
Transmitted-Light DIC Images Using Rotational Diversity, [PS
file][PDF
file]
Authors: C. Preza,
D. L. Snyder, F. U. Rosenberger,J.
Markham,
J.-A. Conchello
Date: July 1997
Length: 11 Pages
Presented at Image Reconstruction and Restoration II, Proc. SPIE, volume
3170,97-107,1997
Image Reconstruction for
Three-Dimensional Transmitted-Light DIC Microscopy, [PS
file][PDF file]
Authors: C. Preza,
D. L. Snyder, J.-A. Conchello
Date: February 1997
Length: 13 Pages
SPIE proceedings from Symposium on BiOS97; 3D Microscopy, volume 2655-24,
1997
Abstract: The derivation of an iterative method for phase reconstruction from Differential-Interference-Contrast (DIC) images is presented here. Because DIC imaging is direction sensitive, in our approach we estimate a specimen's phase function using multiple DIC images obtained by rotating the specimen. Results obtained from testing the method via two-dimensional simulations demonstrate that the use of multiple DIC images at different specimen rotations yield phase reconstructions that more closely resemble the phase function of phantoms than the unprocessed DIC images. Improvement in resolution was also achieved: two points separated by half the Rayleigh resolution limit for coherent illumination not resolved in the unprocessed DIC image, were successfully resolved in the reconstructed phase images. Our results show that phase reconstructions are quantitatively better and resolution is improved when two or more DIC images are used in the reconstruction.
Imaging Models for Three-Dimensional
Transmitted-Light DIC Microscopy, [PS
file][PDF file]
Authors: C. Preza,
D. L. Snyder, J-A Conchello
Date: February 1996
Length: 13 Pages
SPIE proceedings from Symposium on Electronic Imaging, volume 2655,
pp 245-257, 1996
Abstract: Nomarski Differential-Interference-Contrast (DIC) microscopy is a widely used method for imaging transparent specimens that are not visible with ordinary light microscopy. DIC microscopy enhances contrast in the images of such specimens by converting differential phase changes to intensity variations via the method of light interference. These phase changes are introduced in light as it passes through regions of different refractive index within a specimen. In this paper, the development of an imaging model that describes three-dimensional DIC imaging under partially-coherent illumination is presented. Our approach in deriving the model involves the derivation of a two-dimensional model and its extension to three dimensions, assuming weak optical interactions within the specimen. The coherent limit of our two-dimensional model coincides with existing DIC models. Model predictions generated with the coherent limit of the three-dimensional model are compared to real DIC images acquired from imaging phantom specimens. It is shown that the model predictions resemble the real images obtained with the condenser aperture closed better than the images obtained with the aperture open. This result confirms the need for the general model that we have derived.
Tutorial
- Image Restoration for 3-D Microscopy
Instructors: J. G. McNally,J-A
Conchello, F. U. Rosenberger,C.
Preza, J.
Markham
Date: April 26-27, 1996
IBC, Washington University, St. Louis, MO
Artifacts in Computational
Optical-sectioning Microscopy
authors: J. G. McNally,
C. Preza, J-A Conchello,
L. J. Thomas, Jr.
Date: March 1994
Length: 12 Pages
Journal of the Optical Society of America A, 11(3), pp1056-1067, 1994
Abstract: We tested the most complete optical model available for computational optical-sectioning microscopy and obtained four main results. First, we observed good agreement between experimental and theoretical point-spread functions (PSF's) under a variety of imaging conditions. Second, using these PSF;s, we found that a linear restoration method yielded reconstructed images of a well-defined phantom object (a 10-micron m-diameter fluorescent bead) that closely resembled the theoretically determined, best-possible linear reconstruction of the object. Third, this best linear reconstruction suffered from a (to our knowledge) previously undescribed artifactual axial elongation whose principal cause was not increased axial blur but rather the conical shape of the null space intrinsic to nonconfocal three-dimensional (3D) microscopy. Fourth, when 10-micron m phantom beads were embedded at different depths in a transparent medium, reconstructed bead images were progressively degraded with depth unless they were reconstructed with use of a PSF determined at the bead's depth. We conclude that (1) the optical model for optical sectioning is reasonably accurate; (2) if PSF shift variance cannot be avoided by adjustment of the optics, then reconstruction methods must be modified to account for this effect; and (3) alternative microscopical or nonlinear algorithmic approaches are required for overcoming artifacts imposed by the missing cone of frequencies that is intrinsic to nonconfocal 3D microscopy.
Image Reconstruction for
3-D Light Microscopy with a Regularized Linear Method Incorporating a Smoothness
Prior, [PS file][PS
figures]
Authors: C. Preza,
M. I. Miller, J.-A. Conchello
Date: February 1993
Length: 11 Pages
in Biomedical image processing and biomedical visualization. R. S.
Acharya and D. B. Goldgof, Editors Proceedings of the IS&T/SPIE symposium
on Electronic Imaging, Science and Technology, pp. 129-139 (1993)
Abstract: We have shown in [1] that the linear least-squares (LLS) estimate of the intensities of a 3-D object obtained from a set of optical sections is unstable due to the inversion of small and zero-valued eigenvalues of the point-spread function (PSF) operator. The LLS solution was regularized by constraining it to lie in a subspace spanned by the eigenvectors corresponding to a selected number of the largest eigenvalues. In this paper we extend the regularized LLS solution to a maximum a posteriori (MAP) solution induced by a prior formed from a ``Good's like" smoothness penalty [2]. This approach also yields a regularized linear estimator which reduces noise as well as edge artifacts in the reconstruction. The advantage of the linear MAP (LMAP) estimate over the current regularized LLS (RLLS) is its ability to regularize the inverse problem by smoothly penalizing components in the image associated with small eigenvalues. Computer simulations were performed using a theoretical PSF and a simple phantom to compare the two regularization techniques. It is shown that the reconstructions using the smoothness prior, give superior variance and bias results compared to the RLLS reconstructions. Encouraging reconstructions obtained with the LMAP method from real microscopical images of a 10um fluorescent bead, and a four-cell Volvox embryo are shown.
Regularized Linear Method
for Reconstruction of Three-Dimensional Microscopic Objects from Optical
Sections
Authors: C. Preza,
M. I. Miller, L. J. Thomas, Jr., J.
G. McNally
Date: March 1992
Length: 10 Pages
Journal of the Optical Society of America A, Vol. 9, No. 2, pp. 219-228
Abstract: The inverse problem involving the determination of a three-dimensional biological structure from images obtained by means of optical-sectioning microscopy is ill posed. Although the linear least-squares solution can be obtained rapidly by inverse filtering, we show here that it is unstable because of the inversion of small eigenvalues of the microscope's point- spread-function operator. We have regularized the problem by application of the linear-precision-gauge formalism of Joyce and Root [J. Opt. Soc. Am. A 1:149 (1984)]. In our method the solution is regularized by being constrained to lie in a subspace spanned by the eigenvectors corresponding to a selected number of large eigenvalues. The trade-off between the variance and the regularization error determines the number of eigenvalues inverted in the estimation. The resulting linear method is a one-step algorithm that yields, in a few seconds, solutions that are optimal in the mean-square sense when the correct number of eigenvalues are inverted. Results from sensitivity studies show that the proposed method is robust to noise and to underestimation of the width of the point-spread function. The method proposed here is particularly useful for applications in which processing speed is critical, such as studies of living specimens and time-lapse analyses. For these applications existing iterative methods are impractical without expensive and/or specially designed hardware.
Point-Spread Sensitivity
Analysis for Computational Optical-Sectioning Microscopy
Authors: C. Preza, J. M. Ollinger, J. G. McNally, L. J. Thomas,
Jr.
Date: March 1992
Length: 12 Pages
Micron and Microscopica Acta, volume 23, number 4, p. 501-513.
Abstract: Experimentally determined point-spread functions (PSF) have been used routinely for reconstructions of three-dimensional (3-D) microscopic objects from optical sections (Agard et al., 1989, Meth. Cel Biol., 30:353-377; Fay et al., 1986, Opt. Meth. Cell Physiol., 40:51-63). The microscope's PSF is usually measured by imaging a small fluorescent bead. There is a tradeoff in this measurement: very small beads are dim and bleach rapidly, while larger beads are a poorer approximation to a point source. We have simulated the effect of the bead's size on the shape of the PSF by convolving a theoretically determined PSF (of a 40 X 1.0 N.A. oil-immersion lens) with spheres of varying diameters. Simulated data were generated with a 3-D phantom and the theoretical PSF, which is defined to be the `true' PSF for the simulation. Reconstructions of the phantom were obtained with each of the theoretical PSFs obtained from the beads using a regularized linear lease-squares method (Preza et al., 1992, J. Opt. Soc. Am., 9:219-228). Results show a significant drop (more than 50%) in the signal-to-noise ratio of the reconstructions for beads with diameter large than 0.22 micron m. These results suggest that the bead used in the PSF measurement should have a diameter less than 30% of the diameter of the first dark ring of the infocus two-dimensional (2-D) PSF. This study quantifies the tradeoff between the quality of the reconstructions and the bead size used in the PSF measurement.
A Regularized Linear Reconstruction
Method for Optical-Sectioning Microscopy
Authors: C. Preza
Date: August 1990
Length: 100 Pages
Master's Thesis (Sever Institute of Technology, Washington University,
St. Louis, MO, 1990).
Abstract: This thesis studies the problem involving the determination
of a three-dimensional specimen from images obtained via optical-sectioning
microscopy, which is an ill-posed linear-inversion problem. The linear
least-squares solution is shown to be unstable, and thus, the linear precision
gauge LPG formalism of Joyce and Root is studied and used to regularize
the problem. The resulting method yields the optimal linear solution, and
it is shown to be accurate and robust.
This page last updated by C. Preza on September 12, 2000