Optical Tomography

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Optical Tomography

• Medical Imaging
• Instructor Dr. Lei Ying
• Mohammad Habibi

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WHAT IS OPTICAL TOMOGRAPHY?

• Imaging modality based on tissue property for
  physical phenomena, PET,CT, MRI, US
• Flashlight experiment
• tissue illuminated by near infrared light and in
  the other side detector measures light
• First experiment 1929 to detect breast cancer
• human tissue has a relative transparency to
  infrared light in the region 700-1000nm

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laser pulse propagation through scattering medium
spreading
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Why Optical tomography?

• PET gt expensive, limited time, radioactive
• MRIgt expensive, complex, skilled operator, metal
• CT gt ionizing radiation, limited contrast, not
  able to detect small lesion , no functional
  imaging value
• Ultrasoundgt skillful operator, skillful
  interpreter, not able to take image form every
  where.
• OT low cast , non-invasive, portable,Good
  temporal resolution, able to detect OxyHb and
  DeoxyHb simultaneously

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Optical Tomography applications

• Breast imaging ( tumor has different light
  absorption coefficient)
• Functional imaging of the brain
• Detect and diagnostic stroke (Ischemic ,
  hemorrhagic)
• Brain monitoring during surgery

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Challenges in OT

• the inverse problem is ill-posed. That means that
  relatively large changes in the parameters of
  tissue tend to result in relatively small changes
  in the measurements
• nonlinear relationship between the observed
  field amplitude, phase or timing and the
  absorption/scattering coefficients
• Because of scattering, so we have small strength
• define forward problem, geometric model of the
  optical parameters, background parameters, and
  sources and detectors locations and functionality

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Forward and Inverse Problems
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Image formation
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Some examples
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Optical Tomography instrumentation

• Ultra short laser pulse (time domain)
• Rf-Modulated light source (frequency domain)
• Low frequency modulated CW

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Ultra short laser pulse (time domain)
here
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Breast Imaging
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Brain Imaging
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Summary

• OT is based on optical property of the tissue
• Low cast, non-invasive , portable
• Image formation is much difficult than others
• Low spatial and high temporal resolution
• Breast imaging, functional imaging, brain imaging

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References

• 1- Imaging the body with diffuse optical
  tomography Boas, D.A. Brooks, D.H. Miller,
  E.L. DiMarzio, C.A. Kilmer, M. Gaudette, R.J.
  Quan Zhang Signal Processing Magazine, IEEE
• 2- Optical tomography in medical imaging SR
  Arridge. Department of Computer Science,
  University College London,
• 3- www.cs.ucl.ac.uk/staff/S.Arridge/ToastOvervie
  w.html
• 4- www.medphys.ucl.ac.uk/research/borg/images/an
  imations/animation.avi

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• Thats all folks
• Thank you
• Any Question?