Am I Blue? 30 January 2011 (v. 2.0) Brian C. Madden, Ph.D. Department of Dermatology University of Rochester
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
Physics of Light Wave nature Particle nature
The Particle Nature of Light
The Wave Nature of Light
Optical Effects Transmission Reflection Absorption Scattering
Transmission (Refraction)
Reflection
Bidirectional Reflectance Distribution Function
Surface Effects on the BRDF Geometry of normals Multiple reflections Total internal reflection
Polarization Circular Linear
Fresnel Reflection
Absorption Beer’s Law
Chromophores of the Skin
Measured Hemoglobin Spectra
Scattering Tyndall Rayleigh Mie Thomson
Structural Blue
Other Sources of Blue
Mammalian Blue
Blue Lesions
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)
The Neapolitan Model of Skin
Models of Light Transport Kubelka-Munk diffusion Monte Carlo simulation Every model is the embodiment of a trade between computational convenience and reality
Kubelka - Munk Diffusion
Monte Carlo Simulation
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)
Cherry Angioma Model
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)
Port Wine Stain Model (0.8 MB)
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)
Optical/Biological/Psychological Influences Absorption Scattering Anatomy Physiology Perception
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
Perceptual Influences Chromatic sensitivity Spatial Contrast sensitivity HVS nonlinearities Simultaneous brightness contrast Simultaneous color contrast
Perceptual Examples
Skin Tones
Skin and Edges
Sample image Do you trust what you see?
Macro view Should you?
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Skin Reflectance Samples H S B area
Reflectance Differences S B B S
Simultaneous Contrast Distribution
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
Sample image Is this the same image you viewed 11 slides ago?
Sample image redux Do you still trust what you see?
Sample image redux Do you still trust what you see?
Sample image redux Do you still trust what you see?
Sample image redux Do you still trust what you see?
Sample image redux Do you still trust what you see?
Sample image redux Do you still trust what you see?
Sample image redux Do you still trust what you see?
Sample image redux Do you still trust what you see?
Sample image redux Do you still trust what you see?
Sample image redux Do you still trust what you see?
Sample image redux Do you still trust what you see?
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
Interpreting a diagnostic image How much should you trust your vision when you need to be right?
So … am I blue?