. 2008 May 19;35(6):2356–2365. doi: 10.1118/1.2921131

Table 1.

The formalism used to calculate the metrics M, Σ and σ, where Δ is the displacement between the beam and target at a given time, and Δ(P_j,F_l) is the set of displacements for a given fraction F_i for patient P_j (see Ref. 41) (M: mean; SD: standard deviation; RMS: root mean square).

	Patient 1	Patient 2	…
Fraction 1	Δ(P₁,F₁)	Δ(P₂,F₂)
Fraction 2	Δ(P₁,F₂)	Δ(P₂,F₂)
…
			↗	$M = \bar{Δ (P_{1} \dots P_{M}, F_{1} \dots F_{N})}$
Mean	$\bar{Δ (P_{1}, F_{1} \dots F_{N})}$	$\bar{Δ (P_{2}, F_{1} \dots F_{N})}$	→	Σ=SD(Δ(P₁…P_M,F₁…F_N))
SD	SD(Δ(P₁,F₁…F_N))	SD(Δ(P₂,F₁…F_N))	→	σ=RMS(Δ(P₁…P_M,F₁…F_N))