Table 1:

Formulas for CTDI and its variations

Dose IndexFormulaNotes
CTDIT is the nominal width of a section and D(z) is the dose at point z parallel to the z-axis
CTDI measured >100 mmN is the number of acquired sections per scan, T is the nominal width of each acquired section, and D(z) is the dose at point z parallel to the z-axis
Weighted CTDICTDI100,center is the CTDI100 measured at the center of the standard CTDI phantom and CTDI100,periphery is the CTDI100 measured at the periphery of the phantom
CTDIvolPitch is table travel distance per rotation divided by nominal beam width