Evaluation of Target Autocrop Function in Nasopharyngeal Carcinoma SIB IMRT Plan
Xiaojuan Duan, Lu chen, Yibing Zhou
Purpose A new target autocrop function was introduced in the Varian Eclipse™ treatment planning software (version 15.5 above). The study aimed to evaluate this new target autocrop impact on nasopharyngeal carcinoma (NPC) plan quality and delivery efficiency. Methods Randomly 66 approved NPC simultaneous integrated boost (SIB) intensity modulated radiation therapy (IMRT) treatment plans were retrospectively studied. The manual cropping-based plans served as reference and were designed using
... ng-window IMRT. Reference plans were re-optimized with identical planning parameters following the institutional clinical protocol except for the optimization objective of the manual cropping targets deleted. Additionally, each target within 5mm of another had one lower objective at 100% volume and one upper objective at 0% volume for the autocrop plans. Plan quality was assessed based on selected parameters, including TCP (tumor control probability), NTCP (normal tissue complication probability), conformality index (CI), homogeneity index (HI), and dose-volume characteristics. Additionally, the delivery efficiency, the total plan treatment time defined as a sum of monitor units (MUs) for each treated field, and delivery accuracy, γ passing rate of treatment plan quality assurance (QA) also were compared. Results Both the manual cropping plans and the autocrop plans could be approved by an experienced oncologist. Overall, the autocrop plans could provide approximately a 13% reduction in linac MU while maintaining comparable plan quality, radiobiological ranking, and accuracy to that of the manual cropping plans. Conclusions The new target autocrop tip facilitated the SIB IMRT plans for nasopharyngeal cancer patients. The autocrop could guarantee the quality and delivery accuracy of the radiotherapy plan, improved the planning efficiency, treatment efficiency, and reduced machine wear and tear. It was a promising tool for optimal plan selection for NPC SIB IMRT.