Biological Tissue
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tarix
13.11.2017
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489 b.
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Biological Tissue
Biological Tissue
Diagnostics
of cancerous tissue
Radiation therapy
Water and Air
Atmospheric studies and oceanography
Communications
Remote sensing
Pollution studies
Earth
Geological studies
Propagation of pressure waves
Electromagnetic &
acoustic probing
How does light interact with a diffusive random medium like a tissue?
How does light interact with a diffusive random medium like a tissue?
Tumors are hidden inside the tissue
Index of refraction n(r) characterizes any medium
Index of refraction n(r) characterizes any medium
Homogeneous
media Inhomogeneous media
Continuous n(r) Discontinuous n(r)
It can damage the cells
It can damage the cells
It only creates a shadowgram
CAT scan,
PET are again invasive
Existing non-invasive techniques
Existing non-invasive techniques
Magnetic resonance imaging
Bulky
and Expensive
Photodynamic therapy
Requires tumor seeking photosensitive dyes
Ultrasound methods
Cannot detect tumors of size < 1 cm
Problem: Resolution
Solution:
Infrared light
Advantages
Advantages
Noninvasive laser-tissue interaction
High resolution
Propagates very far in tissue
Rugged
and cheap sources available
Reliable detectors
But problems in theoretical modeling ...
No coherent effects like interference
No polarization
Inaccurate
at low penetration depth
Near-field effects are neglected
need a more complete theory
Initial pulse satisfies :
Initial pulse satisfies :
E
= 0 and
B
= 0
Time evolution given by :
E ⁄
t = 1/n2
B
and
B ⁄
t =
–
E
First tests : Snell’s law and Fresnel coefficients
Exact solution of the Maxwell’s
equations
Exact solution of the Maxwell’s equations
Model a tissue as a collection of spheroids of random refractive indices
Systematically test the
conventional
diffusion approximation
Understand near-field effects
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