Optical Effects on Skin: Understanding the Appearance of Blue Veins

1. Am I Blue?30 January 2011 (v. 2.0) Brian C. Madden, Ph.D. Department of Dermatology University of Rochester

2. 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

3. Particle nature • Wave nature Physics of Light

4. The Particle Nature of Light

5. The Wave Nature of Light

6. Optical Effects • Transmission • Reflection • Absorption • Scattering

7. Transmission (Refraction)

8. Reflection

9. Bidirectional Reflectance Distribution Function

10. Surface Effects on the BRDF • Geometry of normals • Multiple reflections • Total internal reflection

11. Polarization Linear Circular

12. Fresnel Reflection

13. Absorption Beer’s Law

14. Chromophores of the Skin

15. Measured Hemoglobin Spectra

16. Scattering • Tyndall • Rayleigh • Mie • Thomson

17. Structural Blue

18. Other Sources of Blue

19. Mammalian Blue

20. Blue Lesions

21. 3D Models of the Skin • Uniform slab • Serial reconstruction Wellman Lab (Anderson & Parrish, 1981) Yale (Braverman et al, 1986) UC Irvine (Smithies et al, 1997) Hokkaido (Matsumura et al 1999)

22. The Neapolitan Model of Skin

23. Models of Light Transport • Kubelka-Munk diffusion • Monte Carlo simulation Every model is the embodiment of a trade between computational convenience and reality

24. Kubelka - Munk Diffusion

25. Monte Carlo Simulation

26. 3D Models of the Skin • Uniform slab • Serial reconstruction Wellman Lab (Parrish & Anderson, 1981) Yale (Braverman et al, 1986) UC Irvine (Smithies et al, 1997) Hokkaido (Matsumura et al 1999)

27. Cherry Angioma Model

28. 3D Models of the Skin • Uniform slab • Serial reconstruction Wellman Lab (Parrish & Anderson, 1981) Yale (Braverman et al, 1986) UC Irvine (Smithies et al, 1997) Hokkaido (Matsumura et al 1999)

29. Port Wine Stain Model (0.8 MB)

30. 3D Models of the Skin • Uniform slab • Serial reconstruction Wellman Lab (Parrish & Anderson, 1981) Yale (Braverman et al, 1986) UC Irvine (Smithies et al, 1997) Hokkaido (Matsumura et al 1999) (0,6MB) (1.4MB) (0.4MB)

31. Optical/Biological/Psychological Influences • Absorption • Scattering • Anatomy • Physiology • Perception

32. 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

33. Perceptual Influences • Chromatic sensitivity • Spatial Contrast sensitivity • HVS nonlinearities • Simultaneous brightness contrast • Simultaneous color contrast

34. Perceptual Examples

35. Skin Tones

36. Skin and Edges

37. Sample image Do you trust what you see?

38. Macro view Should you?

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42. Skin Reflectance Samples H S B area 22 37 84 1 24 38 86 2 21 33 79 3 21 38 85 1 1 2 3 2 3

43. Reflectance Differences B S S B

45. Simultaneous Contrast Distribution

46. 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

47. Sample image Is this the same image you viewed 11 slides ago?

48. Sample image redux Do you still trust what you see?

49. Sample image redux Do you still trust what you see?

50. Sample image redux Do you still trust what you see?