CAT scanners and gamma cameras

1
CAT scanners and gamma cameras

• Unit 16
• Waves

2
Learning objectives

• Describe how CAT scanners can produce a much more
  detailed image than conventional X-rays
• Describe the principle of the ?-camera used to
  image radioactive tracers administered to the body

3
Computerised axial Tomographic Scanner or CAT
4
Gamma Camera

• Is used to produce an image of the body based on
  the ?-rays coming from radionuclides inside the
  body

5
Associated circuitry
Many electrons
electrons
photocathode
Visible photons
scintillator
?
collimator
?-rays
patient
6
Radionuclide imaging

• Displays body functions
• The gamma camera maps ?-rays from radioactive
  tracers in the body.
• A lead collimator defines where the radiation is
  coming from
• A scintillating crystal NaI(Tl) converts the
  incoming ?-radiation into visible radiation
  (scintillations)

7

• An array of photomultiplier tubes transforms the
  visible radiation into amplified electric pulses
• Electronic circuits analyse and display the data
  as a final image
• Image quality may be improved by imaging over a
  narrow energy range, using fine collimators,
  giving the patient higher-activity tracers,
  increasing the number of photomultiplier tubes

8
Tasks

1. Draw a flow chart to show how a CAT scanner
   works.
2. List the uses of a CAT scanner
3. List the advantages and disadvantages of a CAT
   scanner