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Investigation of the Plan Quality for HyperArc Cranial Radiosurgery Using the Millennium MLC

E Flores-Martinez1*, G Kim2 , (1) Moores Cancer Ctr, Univ. of California, San Diego, La Jolla, CA, (2) University of California, San Diego, La Jolla, CA


(Sunday, 7/14/2019) 3:30 PM - 4:00 PM

Room: Exhibit Hall | Forum 4

Purpose: To evaluate the plan quality of HyperArc plans and compare it with RapidArc for the treatment of single metastatic cranial lesions.

Methods: A retrospective comparison between 10 plans previously treated with RapidArc using a ring-based planning approach and 10 plans treated with HyperArc was performed. The investigated plans treated single metastatic lesions with an equivalent diameter of less than 1.5 cm had on a single fraction with a dose prescription between 20 and 24 Gy. Patients were treated with a 6X FFF beam using a Truebeam linac equipped with a Milenium 120 MLC. The time required for planning was extracted from the Care Path. Plan quality was evaluated by measuring the maximum dose (Dmax), the conformity index (CI), the dose gradient index (GM) and the volume of normal brain receiving 10Gy or more (V10Gy). Paired sample Wilcoxon signed rank tests were performed to evaluate statistical differences at the p<0.05 level

Results: The average planning times were 2.7±2.3 h and 2.9±1.7 h for ring-based and HyperArc plans, respectively. Significant differences on Dmax (p=0.009) were observed between RapidArc (120.3±6.5%) and HyperArc (130.5±4.1%) plans. CI results were 1.3±0.1 for the RapidArc and 1.2±0.1 for the HyperArc while GM values were 0.4±0.0 for RapidArc and 0.3±0.0 using HyperArc (p=0.009). Normal brain V10Gy was 3.8±2.1 cc and 2.3±1.6 cc for RapidArc and HyperArc plans, respectively and not statistically significant difference was found at the p<0.05 level. For HyperArc plans, the RTOG CI, Paddick CI, GI and ICRU 83 HI were 1.3±0.2, 0.7±0.1, 3.9±0.4 and 0.2±0.0, respectively.

Conclusion: HyperArc provides a number of advantages that simplify the planning and delivery of cranial radiosurgery plans. Plan quality for HyperArc plans showed improved values of CI and GM and higher values for the maximum dose were observed. No significant differences were observed for normal brain V10Gy




TH- External beam- photons: treatment planning/virtual clinical studies

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