All Research Areas

Modeling Light Propagation

We study dynamic light scattering using numerical techniques such as Monte Carlo and finite-difference time-domain (FDTD). These methods leverage recent advances in computational power to directly model dynamic light scattering in arbitrary three dimensional voxelized geometries. These approaches do not require assumptions about the degree of multiple scattering or the form of the autocorrelation function and are capable of rapidly evaluating the effects of changes in particle motion. We obtain depth-resolved vascular geometries using our two-photon microscope and assign each voxel location-appropriate optical properties. These simulations have been used to better understand the depth dependence of measured fluorescence signals and to quantify the effects of multiple scattering events on laser speckle contrast imaging (LSCI).

Relevant Publications

Sensitivity of laser speckle contrast imaging to flow perturbations in the cortex

M. A. Davis, L. Gagnon, D. A. Boas, and A. K. Dunn, Biomedical Optics Express (2016)

Dynamic light scattering Monte Carlo: a method for simulating time-varying dynamics for ordered motion in heterogeneous media

M. A. Davis and A. K. Dunn, Optics Express (2015)

Flux or speed? Examining speckle contrast imaging of vascular flows

S. M. S. Kazmi, E. Faraji, M. A. Davis, Y. Huang, X. J. Zhang, and A. K. Dunn, Biomedical Optics Express (2015)

Imaging depth and multiple scattering in laser speckle contrast imaging

M. A. Davis, S. M. S. Kazmi, A. K. Dunn, Journal of Biomedical Optics (2014)

Rapid computation of the amplitude and phase of tightly focused optical fields distorted by scattering particles

J. C. Ranasinghesagara, C. K. Hayakawa, M. A. Davis, A. K. Dunn, E. O. Potma, V. Venugopalan, Journal of the Optical Society of America A (2014)

Focusing light within turbid media with weakly discriminating filters

J. W. Tom and A. K. Dunn, Journal of the Optical Society of America B (2014)

Depth dependence of vascular fluorescence imaging

M. A. Davis, S. M. S. Kazmi, A. Ponticorvo, and A. K. Dunn, Biomedical Optics Express (2011)

Far-field superposition method for three-dimensional computation of light scattering from multiple cells

M. S. Starosta and A. K. Dunn, Journal of Biomedical Optics (2010)

Three-dimensional computation of focused beam propagation through multiple biological cells

M. S. Starosta and A. K. Dunn, Optics Express (2009)

Computational microscopy in embryo imaging

J. L. Hollmann, A. K. Dunn, and C. A. Dimarzio, Optics Letters (2004)

Three dimensional Monte Carlo code for photon migration through complex heterogeneous media including the adult human head

D. A. Boas, J. P. Culver, J. J. Stott, and A. K. Dunn, Optics Express (2002)

Perturbation Monte Carlo methods to solve inverse photon migration problems in heterogeneous tissues

C. K. Hayakawa, J. Spanier, F. Bevilacqua, A. K. Dunn, J. S. You, B. J. Tromberg, and V. Venugopalan, Optics Letters (2001)

A pulsed finite-difference time-domain (FDTD) method for calculating light scattering from biological cells over broad wavelength ranges

R. Drezek, A. K. Dunn, and R. Richards-Kortum, Optics Express (2000)

Light scattering from cells: finite-difference time-domain simulations and goniometric measurements

R. Drezek, A. K. Dunn, and R. Richards-Kortum, Applied Optics (1999)

Optical model for light distribution during transscleral cyclophotocoagulation

B. Nemati, A. K. Dunn, A. J. Welch, and H. G. Rylander, Applied Optics (1998)

Finite-difference time-domain simulation of light scattering from single cells

A. K. Dunn, C. Smithpeter, A. J. Welch, and R. Richards-Kortum, Journal of Biomedical Optics (1997)

Three-dimensional computation of light scattering from cells

A. K. Dunn and R. Richards-Kortum, IEEE Journal of Special Topics in Quantum Electronics (1996)

Sources of contrast in confocal reflectance imaging

A. K. Dunn, C. Smithpeter, R. Richards-Kortum, and A. J. Welch, Applied Optics (1996)

Efficient computation of time-resolved transfer functions for imaging in turbid media

A. K. Dunn and C. DiMarzio, Journal of the Optical Society of America A (1996)
Origin of Fluorescence

3D render of fluorescent signal distribution imaged with a camera-like detector overlaid on vascular geometry. When a large area on the surface is illuminated, the collected fluorescence signal can originate not only from deeper in the tissue under the detector area but also from areas near the surface that are not under the detector. (Davis, et al., 2011)

Intravascular Scattering Events

The dynamics of photons scattered within blood vessels are relevant to understanding LSCI. Photons detected by a sensor (top image) localized over microvasculature originate from a larger area and larger number of vessels than photons detected by a sensor (bottom image) directly over an arteriole. (Davis, et al., 2014)