Table 1.

Factors used in the calculation of the margin in both breath-hold and free breathing. Components are shown that apply for all patients.

Margin contributions	Random (R)/Systematic (S)	Cran-Caud [mm]	Vent-Dors [mm]	Med-Lat [mm]
Delineation uncertainty: caused by interpretation differences and contrast limitations	S	2.0	2.0	2.0
Accuracy of pre-treatment imaging: half of the voxel size	S	0.9	0.4	0.4
Accuracy of the dose calculation: determined by resolution	S	1.0	1.0	1.0
Inter-fraction movement: analysed from our patient group using the breath-hold procedure	S	0.2	0.4	0.2
Inter-fraction movement: analysed from our patient group using the breath-hold procedure	R	0.3	0.3	0.3
Deformation [14]	S	1.2	1.0	0.9
Match accuracy [14]	R	0.2	0.6	0.0
Stability during breath-hold (intra breath-hold stability; used for breath-hold only)	R	1.2	1.0	1.0
Accuracy of the cone beam CT system	S	0.5	0.5	0.5
Isocenter accuracy: derived from measurements in our department for an Elekta linac with Agility MLC	S	0.4	0.4	0.4
MLC accuracy	R	0.3	0.3	0.3