Accuracy of Dose Delivery in Multiple Breath-Hold Segmented Volumetric Modulated Arc Therapy: A Static Phantom Study

Table 1

The monitor units per fraction, the gantry arc angles, and the beam-on-times required for noninterrupted delivery are shown for five VMAT clinical cases. When the beams were interrupted for five seconds with varied beam-on-times between interrupts, the number of VMAT segments was counted and recorded.

Case	MU/fx	Gantry arc angle (degree)	Beam-on-time (s)	Measured number of VMAT segments
				Beam-on-time between interrupts (s)
				10	15	20	30	40
1	514.4	195	210	29	17	12	8	6
2	390.7	160	97	14	8	6	4	3
3	588.5	230	137	21	12	9	6	4
4	786.3	360	214	32	18	13	8	6
5	544.2	360	198	30	17	12	8	6