Pitch

• The distance in mm that the CT table moves during one revolution of the x-ray tube.
  • Pitch is used to calculate pitch ratio.

Pitch = Distance table travels during one revolution / Slice thickness or beam collimation

• When the distance the table travels during one revolution of the x-ray tube equals the slice thickness or beam collimation, the pitch ratio is 1:1.
  • A pitch of 1 results in the best image quality.
  • Pitch can be increased to extend the area of coverage and decrease scan time.
    • A pitch of less than 1 means there is overlapping of slices, which results in higher patient dose.
  • A pitch of greater than 1 means there are gaps between slices, which results in lower patient dose.
    • This is only true if the pitch changes, but all other factors remain constant.