Program Information
Investigation of the Accuracy of Different Lung SBRT Plans Created in Eclipse Treatment Planning System
S YILDIRIM*, M CEBE , H MABHOUTI , P PACACI , E SERIN , E SANLI , D ESITMEZ , N KUCUK , M DOYURAN , E KUCUKMORKOC , M CAGLAR , D CANOGLU , R RZAZADE , H ACAR , H CAGLAR OZKOK , Medipol University Hospital, Istanbul, istanbul
Presentations
SU-I-GPD-SPS-4 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: In this study we aimed to investigate the dosimetric accuracy of different lung stereotactic body radiation therapy (SBRT) treatment plans created in Eclipse Treatment Planning System(TPS).
Methods: In the study free breathing (FB), static and four dimensional computed tomography (4DCT) scans were performed on a movable phantom. Images generated from this scans were exported to Eclipse TPS. In Eclipse TPS maximum intensity projection (MIP), average intensity projection (AIP) and minimum intensity projection (MinIP) composite images were generated. Treatment plans were created for each phase of 4DCT scan, PTV10PHASE, PTVMIP, PTVAIP, PTVMinIP, PTVFB, and PTVSTATIC. For each plan, Volumetric Modulated Arc Therapy (VMAT) treatment technique was performed and AAA dose calculation algorithm was used. After irradiation of created plans in Varian-Truebeam STx 2.0, doses measured by gafchromic films were compared with calculated doses using gamma index analysis.
Results: Mean beam-on time for PTV10PHASE, PTVMIP, PTVAIP, PTVMinIP, PTVFB, and PTVSTATIC plans was 4 minutes while it was 55 minutes for phase plans. The gamma passing rate evaluated from EBT3 films were 95.3%, 96.7%, 98.7%, 64.1%, 77.5% and 99.1% for PTV10PHASE, PTVMIP, PTVAIP, PTVMinIP, PTVFB, and PTVSTATIC plans respectively and ranged between 93 - 100% (96.5 ± 3.5%) for phase plans.
Conclusion: Regarding the short treatment time and its high gamma passing rate static plan result implies that breath-hold technique for patients who can hold their breath can be considered as the first choice of treatment technique. For patients who are not capable of holding their breath ITV based plans can be alternative treatment choice. Poor gamma passing rate for plans created from FB and MinIP images showed that these images are not appropriate for lung SBRT treatment plans.
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