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Table 1: Formulas for CTDI and its variations
Dose Index Formula Notes
CTDI T is the nominal width of a section and D(z) is the dose at point z parallel to the z-axis
CTDI measured >100 mm N 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 CTDI CTDI_100,center is the CTDI₁₀₀ measured at the center of the standard CTDI phantom and CTDI_{100,periphery} is the CTDI₁₀₀ measured at the periphery of the phantom
CTDIvol Pitch is table travel distance per rotation divided by nominal beam width

Dose Index	Formula	Notes
CTDI	$\text{[math]}$	T is the nominal width of a section and D(z) is the dose at point z parallel to the z-axis
CTDI measured >100 mm	$\text{[math]}$	N 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 CTDI	$\text{[math]}$	CTDI_100,center is the CTDI₁₀₀ measured at the center of the standard CTDI phantom and CTDI_{100,periphery} is the CTDI₁₀₀ measured at the periphery of the phantom
CTDIvol	$\text{[math]}$	Pitch is table travel distance per rotation divided by nominal beam width