CAT scanners and gamma cameras Unit 16 Waves

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

Computerised axial Tomographic Scanner or CAT

Gamma Camera Is used to produce an image of the body based on the γ-rays coming from radionuclides inside the body

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

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)

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

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