Unit 8 Medical Physics
Paul Kane
Radiographer
Aims for this Session
• Understand the production of and uses for
thermographic images
• Understand X-Ray production
• Und...
The Electromagnetic Spectrum
Thermography
• Infrared detectors
pick up IR radiation
• Amount of radiation
varies with
temperature
• Computer algorithms...
Why is this useful?
• Certain pathologies will cause temperature
differentials
• Thermography detects these with high
sens...
What sort of diagnoses?
• Sports Injuries
• Ca Breast screening
• Monitoring of post operative infection
X-Rays
X-Rays
• Discovered in 1895
by Roentgen
• “X” Rays because he
didn’t know what they
were!
• An ionising radiation
at a hig...
XRAY TUBE
X-Ray Production
Rotating Anode Tube
XRAY TUBE
X-Rays, the risks and dangers
• Ionising Radiation – potentially damaging
• Damage is influenced by:
• Amount of body tiss...
X-Ray Effects
• Stochastic – no threshold for damage
• Non Stochastic – a quantifiable threshold
• Effects can take place ...
How are effects measured?
• Sievert is unit of measurement –
equivalent to a deposit of 1 joule of energy
per kilogram mas...
Precautionary Measures
• Legislation
1. Ionising Radiation Regulations
2. IR(ME)R 2000
• In practice we use
1. Radiation P...
Image Production
• Basic form uses
photographic film
• Denser structures
attenuate the x-rays
• When film is exposed to x
...
Variations in Contrast
Computerised Tomography
CT Explained
• Tomography
• Tomos – slice
• Graphia – describing
• “where digital geometry processing is
used to generate ...
CT in practice
• Data is obtained digitally
• Algorithms allow
manipulation of data
• Windowing is process of
using a vari...
CT versus MR
• Principles of data
collection are the
same
• MR is NON IONISING
• Better at imaging
softer tissue
Which Modality to Use?
• What are you attempting to image?
• What level of information do you wish to
obtain?
• How do you...
Radiation
What is Radioactivity?
• Certain elements have isotopes which are
unstable
• The unstable atoms emit particles or
energy
•...
Radiation Types
• Alpha – helium nuclei
stopped by paper!
• Beta – electron, can
be stopped by light
metal
• Gamma – EM ph...
Half Life
• The time taken for half of the atoms of a
given sample to decay.
• Stays the same for a given isotope
regardle...
Uses for Radioisotopes
• Nuclear Medicine
• Branch of imaging
science which uses
unsealed radioactive
sources
• Gamma sour...
How does it work?
• Radioactive isotopes are labelled with
pharmaceuticals
• Now known as radiopharmaceuticals
• Introduce...
Gamma Camera
Why do we use Nuclear Medicine?
• Radiopharmaceuticals do not cause much
harm in proportion to benefit derived
• Body will...
Production
• Most useful isotopes
are not natural
• Must be produced by
reactors
• Side product of used
nuclear fuel
• “Mi...
Production Cont’d
• Used uranium fuel has a content of
molybdenum99
• Easily extracted
• Technetium99 is daughter product
...
Precautions
• Unsealed source
• Main protection for
staff is time, distance
and shielding
• Patients only need
worry about...
Time Distance Shielding
Detectors
• Scintillation Counters – uses materials
which fluoresce when irradiated
• Geiger Counters – uses a gas which
b...
Film Badge
• Piece of wrapped
photographic film
• Film holder - a plastic
holder containing
various metal and
plastic filt...
Experimenting with Radiation
• Any experiments must be properly
regulated and kept safe – radiation brings
other considera...
QUESTIONS?
X-Rays, Thermography
X-Rays, Thermography
X-Rays, Thermography
X-Rays, Thermography
X-Rays, Thermography
X-Rays, Thermography
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X-Rays, Thermography

  1. 1. Unit 8 Medical Physics Paul Kane Radiographer
  2. 2. Aims for this Session • Understand the production of and uses for thermographic images • Understand X-Ray production • Understand how X-Rays are used to produce images • Understand the dangers of X-Rays • Evaluate the use of both modalities • Understand Radiation, its uses and dangers
  3. 3. The Electromagnetic Spectrum
  4. 4. Thermography • Infrared detectors pick up IR radiation • Amount of radiation varies with temperature • Computer algorithms used to interpret data and produce a usable image
  5. 5. Why is this useful? • Certain pathologies will cause temperature differentials • Thermography detects these with high sensitivity and accuracy • Non – Invasive • No ionising radiation used
  6. 6. What sort of diagnoses? • Sports Injuries • Ca Breast screening • Monitoring of post operative infection
  7. 7. X-Rays
  8. 8. X-Rays • Discovered in 1895 by Roentgen • “X” Rays because he didn’t know what they were! • An ionising radiation at a higher level on EM spectrum • Higher frequency or shorter wavelength
  9. 9. XRAY TUBE
  10. 10. X-Ray Production
  11. 11. Rotating Anode Tube
  12. 12. XRAY TUBE
  13. 13. X-Rays, the risks and dangers • Ionising Radiation – potentially damaging • Damage is influenced by: • Amount of body tissue irradiated • Type of body tissue irradiated • Dose Received • Dose Rate • Risk minimised using “ALARA” principle
  14. 14. X-Ray Effects • Stochastic – no threshold for damage • Non Stochastic – a quantifiable threshold • Effects can take place in somatic cells or be passed on (hereditary)
  15. 15. How are effects measured? • Sievert is unit of measurement – equivalent to a deposit of 1 joule of energy per kilogram mass of tissue • Relates dose absorbed in tissue to biological damage caused – “effective” dose • This will depend on the type of radiation • Typical background radiation results in an effective dose of 2.4 mSv/year
  16. 16. Precautionary Measures • Legislation 1. Ionising Radiation Regulations 2. IR(ME)R 2000 • In practice we use 1. Radiation Protection 2. ALARA principle
  17. 17. Image Production • Basic form uses photographic film • Denser structures attenuate the x-rays • When film is exposed to x rays it turns black • Image is contrast between two • Contrast can be manipulated using exposure factors and other aids such as contrast media
  18. 18. Variations in Contrast
  19. 19. Computerised Tomography
  20. 20. CT Explained • Tomography • Tomos – slice • Graphia – describing • “where digital geometry processing is used to generate a three-dimensional image of the internals of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation “
  21. 21. CT in practice • Data is obtained digitally • Algorithms allow manipulation of data • Windowing is process of using a variety of Hounsfield Units • Setting a top and bottom of range allows various tissue types to be imaged • Can “get rid” of that which does not interest you
  22. 22. CT versus MR • Principles of data collection are the same • MR is NON IONISING • Better at imaging softer tissue
  23. 23. Which Modality to Use? • What are you attempting to image? • What level of information do you wish to obtain? • How do you wish to manipulate it? • What protection measures need to be considered?
  24. 24. Radiation
  25. 25. What is Radioactivity? • Certain elements have isotopes which are unstable • The unstable atoms emit particles or energy • The particles or energy are radiation • The process is unpredictable • It is measured in Bequerels – 1 Bq is one “decay” event per second
  26. 26. Radiation Types • Alpha – helium nuclei stopped by paper! • Beta – electron, can be stopped by light metal • Gamma – EM photon, requires dense material to absorb
  27. 27. Half Life • The time taken for half of the atoms of a given sample to decay. • Stays the same for a given isotope regardless of the actual quantity • Expressed as a unit of time • Can be validated using experimentation and computer modelling
  28. 28. Uses for Radioisotopes • Nuclear Medicine • Branch of imaging science which uses unsealed radioactive sources • Gamma sources are those of choice
  29. 29. How does it work? • Radioactive isotopes are labelled with pharmaceuticals • Now known as radiopharmaceuticals • Introduced into the body • Pharmaceuticals influence tissue type which aborbs isotope • Gamma emission is detected by a gamma camera • Image is digitally produced
  30. 30. Gamma Camera
  31. 31. Why do we use Nuclear Medicine? • Radiopharmaceuticals do not cause much harm in proportion to benefit derived • Body will excrete material • Radioactivity is short lived – matter of hours • Can be used to image anatomy and physiology • Can be integrated with other modalities (PET)
  32. 32. Production • Most useful isotopes are not natural • Must be produced by reactors • Side product of used nuclear fuel • “Milking a cow”
  33. 33. Production Cont’d • Used uranium fuel has a content of molybdenum99 • Easily extracted • Technetium99 is daughter product • A few micrograms of molybdenum99 will produce enough technetium99 to image approx 10,000 patients
  34. 34. Precautions • Unsealed source • Main protection for staff is time, distance and shielding • Patients only need worry about the period immediately around scan
  35. 35. Time Distance Shielding
  36. 36. Detectors • Scintillation Counters – uses materials which fluoresce when irradiated • Geiger Counters – uses a gas which becomes a conductor if irradiated • Film Badges – uses photographic film
  37. 37. Film Badge • Piece of wrapped photographic film • Film holder - a plastic holder containing various metal and plastic filters • Tin, Cadmium, Lead Indium, plastic of differing densities.
  38. 38. Experimenting with Radiation • Any experiments must be properly regulated and kept safe – radiation brings other considerations • Strict international regulations • Adequate protection measures must be in place • QA vital • Participants monitored
  39. 39. QUESTIONS?

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