Dosimetry and Efficiency Comparison of Knowledge-Based and Manual Planning Using Volumetric Modulated Arc Therapy for Craniospinal Irradiation

Abstract

Background. Craniospinal irradiation (CSI) poses a challenge to treatment planning due to the large target, field junction, and multiple organs at risk (OARs) involved. The aim of this study was to evaluate the performance of knowledge-based planning (KBP) in CSI by comparing original manual plans (MP), KBP RapidPlan initial plans (RP_I), and KBP RapidPlan final plans (RP_F), which received further re-optimization to meet the dose constraints.

Methods. Dose distributions in the target were evaluated in terms of coverage, mean dose, conformity index (CI), and homogeneity index (HI). The dosimetric results of OARs, planning time, and monitor unit (MU) were evaluated.

Results. All MP and RP_F plans met the plan goals, and 89.36% of RP_I plans met the plan goals. The Wilcoxon tests showed comparable target coverage, CI, and HI for the MP and RP_F groups; however, worst plan quality was demonstrated in the RP_I plans than in MP and RP_F. For the OARs, RP_F and RP_I groups had better dosimetric results than the MP group (P < 0.05 for optic nerves, eyes, parotid glands, and heart). The planning time was significantly reduced by the KBP from an average of 677.80 min in MP to 227.66 min (P < 0.05) and 307.76 min (P < 0.05) in RP_I, and RP_F, respectively. MU was not significantly different between these three groups.

Conclusion. The KBP can significantly reduce planning time in CSI. Manual re-optimization after the initial KBP is recommended to enhance the plan quality.

Keywords: knowledge-based planning, RapidPlan, craniospinal irradiation, volumetric modulated arc therapy