Treatment planning comparison of volumetric modulated arc therapy employing a dual-layer stacked multi-leaf collimator and helical tomotherapy for cervix uteri

Table 3 Summary of the dose volume histogram analysis for the organs at risk for the node negative patients

Parameter	Objective	Halcyon (H)	Helical Tomotherapy (HT)	Difference (H-HT)	p
Bowel
Mean [Gy]	Minimise	20.5 ± 4.0	21.0 ± 3.0	−0.6 ± 1.7	0.7
V_40Gy [cm³]	≤100 ^a	186.9 ± 115.9	224.9 ± 102.2	−38.1 ± 22.2	< 0.001
V_30Gy [cm³]	≤350 ^a	360.9 ± 195.0	422.9 ± 134.2	−62.1 ± 72.1	0.02
V_15Gy [cm³]	≤600 ^b	1203.8 ± 332.9	1010.8 ± 320.9	192.9 ± 160.4	0.4
Sigmoid
D_1% [Gy]	≤47.3	46.1 ± 0.5	46.1 ± 0.8	−0.08 ± 0.89	0.78
Bladder
D_1% [Gy]	≤47.3	46.6 ± 0.2	46.0 ± 0.3	0.58 ± 0.28	< 0.001
V_40Gy [%]	≤75 ^a	50.4 ± 7.0	52.4 ± 8.3	−2.1 ± 6.6	0.35
V_30Gy [%]	≤85 ^a	69.6 ± 5.8	67.6 ± 7.2	2.0 ± 8.6	0.47
Rectum
D_1% [Gy]	≤47.3	46.2 ± 0.4	46.1 ± 0.6	0.10 ± 0.89	0.72
V_40Gy [%]	≤85 ^a	80.8 ± 10.8	88.1 ± 12.3	−7.2 ± 11.6	0.08
V_30Gy [%]	≤95 ^a	92.4 ± 6.4	97.4 ± 3.9	−5.0 ± 6.1	0.03
Left Fem. Head
D_1% [Gy]	≤50.0	38.7 ± 6.9	32.6 ± 11.7	6.1 ± 12.7	0.17
Mean [Gy]	^b	18.1 ± 2.7	11.7 ± 0.9	6.3 ± 2.2	< 0.001
Right Fem. Head
D_1% [Gy]	≤50.0	38.5 ± 4.4	36.5 ± 3.6	1.9 ± 4.4	0.20
Mean [Gy]	^b	18.8 ± 3..3	11.7 ± 0.9	6.9 ± 2.7	< 0.001
Left Kidney
Mean [Gy]	≤15	1.5 ± 0.7	1.5 ± 0.8	−0.01 ± 0.32	0.97
Right Kidney
Mean [Gy]	≤15	1.5 ± 1.0	1.6 ± 0.9	−0.11 ± 3.7	0.37
Body
D_1% [Gy]	≤47.3	41.9 ± 1.1	42.5±	0.85 ± 0.59	0.001
CI_36Gy	< 1.6 ^b	1.56 ± 0.08	1.82 ± 0.19	−0.26 ± 0.16	0.19
CI_43Gy	< 1.1 ^b	1.08 ± 0.05	1.16 ± 0.09	−0.08 ± 0.08	0.09
CI_Paddick	^b	0.91 ± 0.03	0.86 ± 0.04	0.05 ± 0.03	0.03

V_x%: volume receiving at least x% of the dose. D_x%: dose received by at least x% of the volume. CI = conformity index
^a: soft constraints, expected to be fulfilled in 70–80% of the patients according to EMBRACE II guidelines
^b: not included as optimisation constraint

ISSN: 1748-717X