Optics 1&2- Biomedical imaging

  1. Give the ways that light can interact with tissuescat
    Specular reflection, absorption, fluorescence, scattering
  2. How does Diffuse optical tomography work in breast scans? DRAW THE DIAGRAM TOO
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    • The breast is surrounded by optical sources and sensors
    • High levels of scattering results in banana shaped sensing volumes
    • Tomographic reconstruction is still possible and may detect the absorbers in the blood
    • You can sense lesions in the breast by detecting increased haemoglobin
  3. How does Near infrared spectroscopy of brain activation work
    • Light does not penetrate through tissue but some may be scattered back to the surface
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    Can also study brain activation by detecting absorption at two different wavelengths to detect blood volume
  4. Why does scattering occur and give some examples of sources of scattering
    • Occurs due to changes in refractive index eg:
    • Collagen fibrils
    • Maromolecular aggregates
    • Lysosomes
    • Mittochondira Nuclei
    • Cells
  5. Draw the jablonsky diagram
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  6. What is formula for reduced scattering coefficient?
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  7. What are the types of scattering?
    Rayleigh scattering 

    Mie scattering
  8. When does Rayleigh scattering happen? What does the scattering cross section (probaility of scattering) depend on
    When the wavelength of light is Much larger than the size of particles

    • scattering cross section σ is dependent on λ
    •  σ = 1/ λ4
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  9. What is the condition of Mie scattering?
    • when wavelength of light is roughly the same as the size of particles
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  10. What is the formula for mean free path?
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  11. What is the application of super scattered light like this
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    • NIRS brain imaging
    • Breast imaging
  12. What is the optical transmission window, and what do you do with it
    • 600-1100nm where haemoglobin absorption is low
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    • With this you can take measruements at two wavelengths to see the relative conc of oxy and deoxy haemoglobin

    Problem: scattering of liight makes accurate measurement difficult
  13. What is the application of slightly scattered light like here?
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    Optical tomography but only for thin samples (<10mm).

    Otherwise not a particularly realistic scenario
  14. What is the use for moderately scattered light? (level 3)
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    • Useful for photoplethysmography (pulse oximeter)
    • Diffuse optical tomography
  15. How does pulse oximetry work
    Absorption varies depending on the concentration of oxy and deoxy haemoglobin

    Monitor wavelength at two wavelengths eg 650 and 900nm

    • Since blood volume changes from heartbeat you can filter out the AC component etc
    • Could use it to monitor heartbeat actually.
  16. Draw the quantised energy level diagram
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    • Also the print is small so the y axis numbers are:
    • 15000
    • 5000
    • 1000
    • Then the ones towards the right go down in factors of ten
    • It goes Electronic,vibrational,Rotational,Translational
  17. What kind of light interactions do endoscopes take advantage of?
    Specular and diffuse reflection
  18. Draw a hopkins rod lens endoscope
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    • High res
    • Wide field of view (100 deg)
    • Wide working range of distances
    • Not too much chromatic aberration
  19. What is narrow band imaging and how does it work?
    Use narrow bands light instead of full white light spectrum
  20. What is formula for quantum efficiency
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    • gamma is radiative decay rate
    • K is non radiative decay rate
  21. What is formula for fluorescent lifetime
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    • gamma is raidative decay rate
    • K is non radiative decay rate
  22. What general methods are there to use endoscopes to contrast tissue?
    • White light illumination
    • Narrow and illumination
    • Fluorescence
Card Set
Optics 1&2- Biomedical imaging
optics and shit