Table 2.

Results obtained for off-axis beams. C — values calculated from Gaussian fitting, R2 — coefficient of determination, delta — difference between profile points of inflection and nominal field size for given depth, delta1 – differences for open symmetrical fields between theoretical beam size and measurement from the same measurement series

Depth [mm]	C [mm]	R2	Field size calculated [mm]	Δ [mm]	Δ1 [mm]
6 MV, X1 = −100, X2 = 0, Y1 = −10, Y2 = 10, O
16	−91.1	0.959	90.8	0.8	0.5
	−0.2	0.977
50	−94.4	0.983	94.1	0.9	0.8
	−0.2	0.980
100	−99.4	0.993	99.1	0.9	0.7
	−0.2	0.976
200	−109.6	0.967	109.3	0.7	0.9
	−0.2	0.969
6 MV, X1 = 0, X2 = 50, Y1 = −50, Y2 = 0, O
16	0.8	0.989	44.8	1.0	1.0
	45.6	0.986
50	0.8	0.955	46.4	1.1	1.0
	47.2	0.996
100	0.8	0.979	48.8	1.2	0.9
	49.6	0.970
200	0.8	0.967	53.7	1.3	0.9
	54.5	0.962
16	−45.9	0.976	45.5	0.3	0.0
	−0.4	0.966
50	−47.6	0.992	47.1	0.4	0.0
	−0.5	0.976
100	−50.1	0.981	49.7	0.3	−0.3
	−0.4	0.979
200	−55.1	0.994	54.6	0.4	−0.2
	−0.5	0.995