large data sets workshop university of nottingham 13 th april 2006 polarized light imaging for skin...
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Large Data Sets WorkshopUniversity of Nottingham
13th April 2006
Polarized Light Imaging for Skin Cancer Diagnosis
James HousleySchool of Electrical and Electronic Engineering
University of Nottingham
eexjh1@nottingham.ac.uk
Overview
Skin and polarized light Data so far Analysis methods so far Ideal data What can we do with it? Conclusion
Skin is permeable to light
Surface Reflections
Superficial Visitation
Deep Visitation
Light In
(Not to scale)
Skin is permeable to light
Light In Light Out
Polarized Light
Linear Polarization Circular Polarization
Co-polar and Cross-polar
Co-polar Cross-polar
Cross-polarCo-polarReference
Linear:
Reference
Circular:
How is polarization useful?
More collisions, less polarization maintained Deeper visitation, more collisions
Deeper visitation = less polarization maintained
Linearly polarized light on skin
Co-polar
Co-polar
Random (Co-polar + Cross-polar)
Linearly Polarized Light In
How can we use that?
Detect co-polar and cross-polar light separately
Channel 1 – channel 2:surface + superficial + deep – deep = surface + superficial
Channel Light Configuration Skin Information
1 Linear Co-polar Surface Reflections & Superficial Layers & Deep Layers
2 Linear Cross-polar Deep Layers
Linear vs. circular
Surface reflections are cross-polar in circular polarization compared to co-polar in linear polarization
For circularly polarized light, the direction of polarization is maintained, but the
direction of the light is reversed. Therefore circular polarization is ‘flipped in helicity’
by reflections
Linearly polarized light stays polarized in the same plane after reflection
Light
Polarization
Circularly polarized light on skin
Cross-polar (cf. co-polar for linear polarization)
Co-polar
Random (Co-polar + Cross-polar)
Circularly Polarized Light In
Any better?
Channel 3 – channel 2:superficial + deep – deep = superficial
Channel Light Configuration Skin Information
1 Linear Co-polar Surface Reflections & Superficial Layers & Deep Layers
2 Linear Cross-polar Deep Layers
3 Circular Co-polar Superficial Layers & Deep Layers
4 Circular Cross-polar Surface Reflections & Deep Layers
A demonstration
Channel 1 Channel 3 Channel 4Channel 2
Channel 1 – 2 Channel 3 – 2
What next?
Extract information from imagesMalignant LesionsBenign Lesions
Comparing ChannelsScattergraph - every point represents the
intensity of a pixel in two different channels
Comparing channels
Principal components analysis
Method of reducing dimensions in data Four images = four dimensions 1st principal component is an image which
contains the most possible information from all four images
Represents the best possible way of reducing the four dimensional data down to one dimension
Principal components analysis
Principal components analysis
Ideal data
4 channels 4 light sources
16 images per skin sample
Or, for superficial skin layers only
4 images per skin sample
(1 per light source)
What can we do with this data?
Principal components analysis Segmentation Neural networks
Conclusion
?
Acknowledgements
Dr. Steve Morgan Dr. John Crowe Dr. Ian Stockford
Any questions?
Channel 1 Channel 3 Channel 4Channel 2
Channel 1 – 2 Channel 3 – 2
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