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13-Nuclear Medicine (x-ray (relies on absorption by different parts of the…

- - - - computer integrates multiple 2D projections in construct cross sectional view
      - can use multiple detectors
      - internal or external source
      - dose <20mSv
      - good for organs and bones
    - - more advanced CT
      - able to provide 3d info
      - moniters level of biological activity, e.g. blood flow
      - detectors are collimated
      - less efficient
- - - - finely segmented scntillator
    - - dense detector material
    - - to minimised pulse pile up, give high confidence timing and high live time
  - - - enrgy deposited from crystal causes excitation of the molecules, which relax by emission of scintillation photons
    - - Sodium iodide doped with thallium (NaI(Tl))
        
        less dense, so less efficient as stopping photons
      - Bismuth germinate
      - leutetium
      - gadolinium orthocilicate
      - chance of photoelectric interaction increases rapidly with with Z, proportional to z^3
      - compton scattering more likely in denser material
    - - records the scintillation photons
      - photons enter, electrons are emitted into the vaccum and multiplied due to high fields between dynodes
      - large pulse is outputted
    - - also lowers dose