Scan protocol optimisation : helical pitch

• Higher pitch gives proportionally lower patient dose

  • At the expense of slice width and contrast with single slice
  • At the expense of noise or/and slice width in multi-slice
    • Some manufacturers increase mA to compensate for pitch ‘effective mAs’ or ‘mAs per slice’

• Higher pitch generally gives more helical artefacts

  • But also leads to faster scan times

• Compromise is necessary

  • Priorities depend on application