Evaluation of inter-fraction and intra-fraction errors during volumetric modulated arc therapy in nasopharyngeal carcinoma patients

Table 2 Summary of inter-fraction and intra-fraction translational error and rotational error in each dimension

Translational error (mm)
	Initial inter-fraction error			Residual inter-fraction error			Intra-fraction error
	ML	SI	AP	ML	SI	AP	ML	SI	AP
M	−0.3	−0.9	0.8	0	−0.4	0.2	0	−0.2	−0.3
SD	1.5	1.3	1.2	0.7	0.8	0.8	0.5	0.7	0.7
Minimum	−5.2	−4.8	−2.9	−2.0	−2.0	−1.9	−1.5	−2.4	−2.8
Maximum	5.0	2.0	4.2	1.8	2.0	2.0	2.1	1.8	0.7
Σ	1.4	1.0	1.0	0.4	0.5	0.4	0.2	0.4	0.4
σ	0.8	0.8	0.7	0.6	0.7	0.7	0.5	0.6	0.6
Rotational error (°)
	Initial inter-fraction error			Residual inter-fraction error			Intra-fraction error
	pitch	roll	yaw	pitch	roll	yaw	pitch	roll	yaw
M	−0.7	−0.2	−0.2	−0.7	−0.1	−0.1	−0.1	0.1	0
SD	0.9	1.4	1.0	0.9	1.4	0.9	0.5	0.5	0.4
Minimum	−3.5	−4.4	−4.0	−3.0	−3.0	−3.0	−2.8	−1.2	−1.5
Maximum	2.1	2.9	2.8	1.8	2.9	2.7	1.4	1.5	0.9
Σ	0.7	1.0	0.7	0.7	1.0	0.6	0.3	0.2	0.2
σ	0.6	1.0	0.7	0.6	1.0	0.7	0.5	0.5	0.4

M, mean of all patients’ mean; SD, standard deviation; Σ, systematic setup uncertainty; σ, random setup uncertainty; ML, medial–lateral; SI, superior–inferior; AP, anterior–posterior.

ISSN: 1748-717X