A study of minimum segment width parameter on VMAT plan quality, delivery accuracy, and efficiency for cervical cancer using Monaco TPS

Purpose The purpose of this study was to study the influence of the minimum segment width (MSW) on volumetric modulated arc therapy (VMAT) plan quality, delivery accuracy, and efficiency for cervical cancer treatment. Methods Nineteen patients with cervical cancer were randomly selected to design VMAT plans. Three VMAT plans were generated for each patient incorporating MSWs of 0.5, 1.0, and 1.5 cm while other planning parameters remained constant using the Monaco treatment planning system (TPS) with 6 MV X rays delivered from an Elekta Synergy linear accelerator. Plan quality and delivery efficiency were evaluated based on dose‐volume histograms (DVHs), control points, monitor units (MUs), dosimetric measurement verification results, and plan delivery time. Results Except for the small difference in target dose coverage and maximum dose, there were no statistically significant differences between the other dosimetric parameters in the planning target volumes. The 1.0 and 1.5 cm MSW plans showed lower maximum doses to the spinal cord than the 0.5 cm plan; doses to other organs at risks were similar regardless of MSWs. The mean reductions of total MUs when compared with the 0.5 cm plan were 14.5 ± 6.1% and 20.9 ± 7.9% for MSWs of 1.0 and 1.5 cm, respectively. The calculated gamma indices using the 3% and 3 mm criteria were 96.2 ± 0.6%, 97.0 ± 0.6%, and 97.6 ± 0.6% for the 0.5, 1.0 and 1.5 cm MSW plans, respectively. The plan delivery times decreased with increasing MSWs (p