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 γ-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 γ-rays coming from radionuclides inside the body

5. Associated circuitry photocathode electrons Many electrons Visible photons scintillator γ collimator γ -rays patient

6. Radionuclide imaging Displays body functions The gamma camera maps γ-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 γ-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