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E E
E E
Linear Circular
Elliptical Unpolarized
Polarized Light
• Electromagnetic wave
• Fields have orientation
• Orientation of electric field is polarization
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Polarized Light in Tissue
Scatteringcells, organelles, nucleus Linear Birefringence
structural proteins (collagen, elastin)
ne
no
δ - Retardance
Optical activity(Circular Birefringence)
proteins, glucose
Δ - Depolarization
α - Optical Rotation
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Myocardial Regeneration
Control Stem Cell
Retardance Imaging• Retardance images, decreased retardance in infarct
• Histology: muscle in red, collagen in blue (Masson’s trichrome)
• Healthy muscle, increased collagen in scar
• Higher retardance in stem cell treated infarct (increasedorganization)
Wood et al, J. Biomedical Optics (2010).
rad
rad
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Polarized Light Mathematics
êx
êy
Ey
Ex
Beam intensity
0° and 90°
±45°
Circular (right/left)
Polarization expressed by Stokes vector
Polarization effects applied by Mueller matrix
incident polarization
output polarization
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Modeling Polarized Light in Tissue
Statistical Method• Sample known probability distributions for interactions
Scattering
Reflections
Absorption
IncidentLight
• Track many photon paths (>108)
• Alter polarization (apply Mueller matrix)
• Record statistics
• Calculate average properties
• Gives macroscopic properties
Calculate macroscopic propertiesfrom many individual interactions
Combining polarization effects in model(Mueller matrices non-commutative AB ≠ BA)
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Mueller Matrix Decomposition
But Mueller matrix contains all effects
M
MΔ MR MD
Measured Matrix
Decomposed Matrices
Decomposed MatricesMΔ: Depolarization Matrix (scattering)
MR: Retardance Matrix (optical activity and birefringence)
MD: Diattenuation Matrix (dichroic absorption)
Ghosh, Wood, and Vitkin, J. Biomedical Optics (2008).
Polar Decomposition
We want to measure polarization effects of tissue(depolarization, birefringence,optical activity, etc)
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Acknowledgments
• Supervisor: Dr. Alex Vitkin
• Polarimetry Group: Dr. Xinxin Guo, Dr. Nirmalya Ghosh, Marika Wallenburg,Shannon Dang, Nasit Vurgun, Manzoor Ahmad, and Sanaz Alali
• Collaborators: Dr. Ren-Ki Li, Shu-Hong Li, and Dr. Dick Weisel (McEwen Centre forRegenerative Medicine)
• Vitkin Lab and Wilson Group
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