The effect of auto-planning parameter settings on the quality of automated cervical cancer plans

Abstract

PurposeThis study refines the parameters of automatic planning to improve plan quality and enhance the protection of organs at risk (OARs). Materials & methods30 cases of cervical cancer underwent manual (M-VMAT) and automated VMAT planning. The automated planning used five parameters: Engine Type (Biological and Non-Biological) and Use Cold-Spot ROIs (Yes and No) were qualitative; Tuning Balance (1–100%, default: 11%), Dose Fall-off Margin (1.0–4.5 cm, default: 2.6 cm), and Hot-Spot Maximum Goal (101–110%, default: 107%) were quantitative. The original automated plans (A1-VMAT) utilized default parameters, while the adjusted automated plans (A2-VMAT) utilized modified parameters. Dosimetric parameters and plan complexities were compared among M-VMAT, A1-VMAT, and A2-VMAT. ResultsCompared to M-VMAT, the A1-VMAT underperformed in protecting OARs. However, the A2-VMAT effectively addressed this issue. When adjusting “Use Cold-Spot ROIs” to “No”, “Tuning Balance” to 100%, and “Hot-Spot Maximum Goal” to 110%, while keeping the remaining parameters at their default settings, A2-VMAT significantly improved OAR protection in this study. Compared to A1-VMAT, the A2-VMAT showed only a slight increase in bowel's Dmax (approximately 2.11%, P < 0.05), while various OARs achieving significant dose reductions. Notably, there were significant reductions (over 30%, P < 0.05) in V35, V40 of rectum, V25, V30, V35 of femoral heads, and V10, V15, V20 of kidney. Furthermore, the efficacy of these five parameters was also observed in this study. Except for Engine Type, adjustments to the other parameters impacted Conformity Index, Homogeneity Index, and maximum dose (Dmax) for the PTV. Engine Type affected the average dose to OARs, and Hot-Spot Maximum influenced the Dmax for OARs overlapping with the PTV. ConclusionThe adjusted automated plan improved plan quality compared to the original automated plan, enhancing OAR protection. The adjusted plan demonstrated lower complexity than the manual plan.