How to calculate reference doses

• CTDIvol = nCTDIvol x mAs (per rotation)

  • nCTDIw : measured on head or body Perspex phantom at appropriate kV and slice width & corrected for pitch
  • CTDIvol = nCTDIw x effective mAs

• DLP = nCTDIw x nT x total mAs

  • = (CTDIw /pitch) x scan length
  • = CTDIvol x scan length

• where nT = nominal irradiated width