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Am I Blue? 30 January 2011 (v. 2.0) Brian C. Madden, Ph.D. Department of Dermatology University of Rochester
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Interaction of Light and Tissue Physics of light Optics of skin Models of light transport in skin Perceptual influences Example: The appearance of veins in vivo
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Physics of Light Wave nature Particle nature
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The Particle Nature of Light
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The Wave Nature of Light
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Optical Effects Transmission Reflection Absorption Scattering
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Transmission (Refraction)
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Reflection
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Bidirectional Reflectance Distribution Function
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Surface Effects on the BRDF Geometry of normals Multiple reflections Total internal reflection
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Polarization Circular Linear
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Fresnel Reflection
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Absorption Beer’s Law
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Chromophores of the Skin
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Measured Hemoglobin Spectra
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Scattering Tyndall Rayleigh Mie Thomson
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Structural Blue
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Other Sources of Blue
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Mammalian Blue
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Blue Lesions
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3D Models of the Skin Uniform slab Serial reconstruction Wellman Lab (Anderson & Parrish, 1981) Hokkaido (Matsumura et al 1999) Yale (Braverman et al, 1986) UC Irvine (Smithies et al, 1997)
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The Neapolitan Model of Skin
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Models of Light Transport Kubelka-Munk diffusion Monte Carlo simulation Every model is the embodiment of a trade between computational convenience and reality
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Kubelka - Munk Diffusion
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Monte Carlo Simulation
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3D Models of the Skin Uniform slab Serial reconstruction Wellman Lab (Parrish & Anderson, 1981) Hokkaido (Matsumura et al 1999) Yale (Braverman et al, 1986) UC Irvine (Smithies et al, 1997)
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Cherry Angioma Model
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3D Models of the Skin Uniform slab Serial reconstruction Wellman Lab (Parrish & Anderson, 1981) Hokkaido (Matsumura et al 1999) Yale (Braverman et al, 1986) UC Irvine (Smithies et al, 1997)
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Port Wine Stain Model (0.8 MB)
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3D Models of the Skin Uniform slab Serial reconstruction Wellman Lab (Parrish & Anderson, 1981) Hokkaido (Matsumura et al 1999) Yale (Braverman et al, 1986) UC Irvine (Smithies et al, 1997) (0,6MB) (0.4MB) (1.4MB)
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Optical/Biological/Psychological Influences Absorption Scattering Anatomy Physiology Perception
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What is physically different about blue veins? Vein depth in dermis diffuses borders Vein depth in dermis supports accumulation of superimposed scatter Vein diameters are sufficiently large to concentrate hemoglobin Hemoglobin absorption in veins is sufficient to visibly reduce total backscatter at the surface
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Perceptual Influences Chromatic sensitivity Spatial Contrast sensitivity HVS nonlinearities Simultaneous brightness contrast Simultaneous color contrast
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Perceptual Examples
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Skin Tones
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Skin and Edges
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Sample image Do you trust what you see?
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Macro view Should you?
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p
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Skin Reflectance Samples 1 2 3 1 2 3 H S B area 22 37 84 1 24 38 86 2 21 33 79 3 21 38 85
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Reflectance Differences S B B S
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Simultaneous Contrast Distribution
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Unresolved Issues Contributions of hematocrit and oxygenation Pressure and flow related sedimentation and clustering Erythrocyte scattering model Dermatoglyphic patterns and surface hydration Fresnel reflection and backscatter contribution Diffuse vein segmentation Structure of dermal vasculature
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Sample image Is this the same image you viewed 11 slides ago?
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Sample image redux Do you still trust what you see?
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Sample image redux Do you still trust what you see?
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Sample image redux Do you still trust what you see?
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Sample image redux Do you still trust what you see?
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Sample image redux Do you still trust what you see?
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Sample image redux Do you still trust what you see?
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Sample image redux Do you still trust what you see?
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Sample image redux Do you still trust what you see?
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Sample image redux Do you still trust what you see?
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Sample image redux Do you still trust what you see?
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Sample image redux Do you still trust what you see?
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Summary and Conclusions Differential absorption leads to simultaneous contrast Differential scatter leads to desaturation Vein depth leads to a diffuse surface profile Taken together they promote a color contrast effect Expectation transforms a collection of weak effects into a substantial perceptual change
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Interpreting a diagnostic image How much should you trust your vision when you need to be right?
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So … am I blue?
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