(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: The purpose of this study is to report the efficiency gain and quality improvements in planning the whole brain with hippocampal sparing (HCSWB) cases using a shared RapidPLAN model.
Methods: A shared RapidPLAN model for HCSWB was imported from the Varian OncoPeer Cloud. Five previously treated WBHCS cases were used as model validation. Bilateral hippocampal contours were generated according to RTOG 0933 and expanded by 5mm for the hippocampal avoidance regions. Dose constraints were D100 (hippocampus) < 9Gy and V15Gy < 0.03cc. DVH and dose distribution of previously approved clinical plan (CP) and Rapidplan (RP) were compared. To meet our own clinical protocol, Dmean of cochlea < 30Gy was added to the shared model. Furthermore, we applied the final customized model to a recently enrolled HCSWB case with a simultaneous integrated boost (SIB).
Results: The model validation on the five previously treated cases showed comparable target coverage of homogeneity index (HI) and conformity index (CI) and OARs sparing between CP and RP, except hippocampus. The Dmeans of the hippocampus were significantly reduced by 24%: from 11.96 ± 1.47Gy to 9.05 ± 1.04Gy for all five cases (P< 0.01). V15Gy (hippocampus) of the five re-planned cases (RP) were less than 0.01cc. For the clinical case directly planned with RapidPLAN, the Dmax of the hippocampus, the hippocampus with 3mm-margin, and the hippocampus with 5mm-margin structures were 11Gy, 13.4Gy, and15 Gy for 0.09cc, respectively. The average planning time for these six cases was shortened from approximately two days to less than half a day.
Conclusion: Developing a custom RapidPlan model may not be feasible initially due to, e.g, insufficient number clinical cases. This study demonstrated the feasibility, efficiency gain, and quality improvements by utilizing a shared RapidPLAN model for HCSWB treatment planning after slight modification and clinical validation.
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