Nuclear Medicine Viva Questions


Gamma camera


  • Explain how a gamma camera works.
  • Draw the head of a gamma camera and explain the function of each component.
  • Describe the operation of a gamma camera with respect to the image quality.
  • What are the units of camera sensitivity, and how would you measure it?


  • What is a collimator
  • Have you actually seen one!?
  • What shape are the holes?
  • What are the advantages of using hexagonal or triangular septa, as opposed to circular holes drilled in lead?
  • How many holes are there?
  • What types of collimators are there?
  • What are the approximate energy ranges of the high, medium and low E colls?
  • What isotope are low energy ones used for?
  • What energy is that [Tc]?
  • How do medium energy collimators differ?
  • What sort of increase in thickness of the septa is needed?
  • What is full width half maximum? Describe it.
  • What is the relationship between resolution and sensitivity?
  • How does the collimator affect sensitivity?
  • What is the definition of resolution and sensitivity wrt collimation?
  • What are the factors that affect image quality with respect to the collimator?
  • How are sensitvity and spatial resolution related?
  • How are resolution & sensitivity of camera related to distance etc.?
  • Give typical values for Ri and Rc and hence what is Rs
    (R for resolution, i=intrinsic, c=collimator, s=system)


  • What are the most important properties in a scintillation crystal?
  • Why is NaI(Tl) the primary choice for crystal material?
  • What is the gamma radiation range of NaI(Tl)?
  • What physical process happens in the scintillation crystal?
  • What is the average dead time of the crystal?
  • Give a typical thickness of a crystal.
  • Why is the crystal thickness important?
  • How efficient is the crystal at stopping a gamma ray which has passed through the collimator septa?


  • How many PM tubes are used? What is a typical PM tube diameter?
  • Why does the number of detectors matter?
  • Describe the operation of the PM Tube, what accelerating voltages are used?
  • What is an approximate yield of electrons at the final dynode?

    Electronics, etc:

  • Describe briefly the pre-amp, amp and pulse height analyser.
  • What corrections may be applied to the camera (5)?
  • How are the x, y, z position signals generated?
  • At what point are signals from a gamma camera digitised?
  • How is an energy spectrum obtained?
  • How is the energy resolution determined from such a spectrum?


  • Draw a typical gamma energy spectrum. Describe the main features and what processes give rise to them.
  • What are the considerations necessary when setting up a service to use a new isotope for clinical use?
  • What isotpe is typically used for investigations?

    Quality assurance


    Other equipment:


    Clinical applications

    Trainees usually need to be prepared to comment on the appearance of normal anatomy and pathology on common diagnostic images, e.g. bone scans, as shown to them by the examiner.







    Radiation Protection/Legislation