Medical sciences (Basel, Switzerland) · 2026
VMAT for Head and Neck Cancer: What Is the Impact of the Optimization Parameters on the Treatment Plan Quality?
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Konstantinou Evgenia, Lyraraki Efrossyni, Mazonakis Michalis
Аннотация
OBJECTIVES: To evaluate the effectiveness of different optimization parameters on radiotherapy plan quality for seventeen head and neck cancer patients.
METHODS: Volumetric Modulated Arc Therapy with Simultaneous Integrated Boost (VMAT-SIB) plans, involving up to three tumors, were generated. For each participant, a reference plan (Plan_Ref) was created using dual-arc with 180 control points, 20° gantry-angle increment and 1 cm minimum segment width. Modified plans were developed with dose constraints and optimization settings constant by changing to single-arc, 150 and 200 control points, 0.5 cm minimum segment width, and 30° and 40° gantry-angle increments. These plans were referred to as Plan_Arc1, Plan_CP150, Plan_CP200, Plan_SW0.5, Plan_Inc30, and Plan_Inc40, respectively. D95% of planning target volumes (PTVs), homogeneity index (HI), monitor units (MUs), maximum dose (Dmax) of spinal cord, mandible, and brainstem were recorded. Statistical and Bland-Altman analysis was performed comparing the modified plans to Plan_Ref.
RESULTS: Average D95% values for PTV1, PTV2, and PTV3 ranged from 93.13 to 98.82%. Plan_SW0.5 provided superior target coverage and homogeneity with higher MUs than Plan_Ref. Plan_Arc1 significantly reduced PTV coverage and dose homogeneity, while increasing MUs compared with Plan_Ref (p < 0.05). The average Dmax as derived from all planning approaches was up to 43.86 Gy, 65.86 Gy, and 48.85 Gy for spinal cord, mandible and brainstem, respectively. For spinal cord, Plan_Ref led to significantly lower doses compared to Plan_Arc1 and Plan_Inc30, while the brainstem recorded statistically higher Dmax doses than Plan_Arc1. Significantly higher Dmax was observed for the mandible using Plan_SW0.5 (p < 0.05). However, for Dmax, the comparison plans showed good agreement with Plan_Ref based on Bland-Altman analysis.
CONCLUSIONS: The VMAT plan quality is strongly affected by the minimum segment width whereas no differences were observed with the modification of the number of control points.
METHODS: Volumetric Modulated Arc Therapy with Simultaneous Integrated Boost (VMAT-SIB) plans, involving up to three tumors, were generated. For each participant, a reference plan (Plan_Ref) was created using dual-arc with 180 control points, 20° gantry-angle increment and 1 cm minimum segment width. Modified plans were developed with dose constraints and optimization settings constant by changing to single-arc, 150 and 200 control points, 0.5 cm minimum segment width, and 30° and 40° gantry-angle increments. These plans were referred to as Plan_Arc1, Plan_CP150, Plan_CP200, Plan_SW0.5, Plan_Inc30, and Plan_Inc40, respectively. D95% of planning target volumes (PTVs), homogeneity index (HI), monitor units (MUs), maximum dose (Dmax) of spinal cord, mandible, and brainstem were recorded. Statistical and Bland-Altman analysis was performed comparing the modified plans to Plan_Ref.
RESULTS: Average D95% values for PTV1, PTV2, and PTV3 ranged from 93.13 to 98.82%. Plan_SW0.5 provided superior target coverage and homogeneity with higher MUs than Plan_Ref. Plan_Arc1 significantly reduced PTV coverage and dose homogeneity, while increasing MUs compared with Plan_Ref (p < 0.05). The average Dmax as derived from all planning approaches was up to 43.86 Gy, 65.86 Gy, and 48.85 Gy for spinal cord, mandible and brainstem, respectively. For spinal cord, Plan_Ref led to significantly lower doses compared to Plan_Arc1 and Plan_Inc30, while the brainstem recorded statistically higher Dmax doses than Plan_Arc1. Significantly higher Dmax was observed for the mandible using Plan_SW0.5 (p < 0.05). However, for Dmax, the comparison plans showed good agreement with Plan_Ref based on Bland-Altman analysis.
CONCLUSIONS: The VMAT plan quality is strongly affected by the minimum segment width whereas no differences were observed with the modification of the number of control points.