A Study to Quantify Dosimetric Consequences of Pancreatic Tumor Motion on the Robustness of IMRT Plans using a Motion Kernel Convolution Method

Abstract

Results: PTV coverage and IMRT QA passing rate were reduced significantly with an increase in the magnitude of pancreatic tumor motion. The V95% of PTV was reduced by 12% when 1.0 cm tumor motion was applied. By contrast, the CTV coverage was maintained when the magnitude of tumor motion was 1.0 cm. The V98% of CTV was reduced by 16% when the largest tumor motion (2.0 cm) was applied. The IMRT QA passing rate was ?80% when 1.5 cm motion was applied, which corresponds to a 23% and 6% reduction of the PTV and CTV coverage, respectively. Dose to OARs (small bowel, liver and kidneys) were not affected significantly with tumor motion. The general tendency in dose to the OAR was an increase in the low dose region and a decrease in the high dose region as the magnitude of motion increased. Conclusions: This study suggests that CTV coverage of pancreatic tumor can be maintained with IMRT delivery as long as the pancreatictumormotionis withinthePTV.TheCTVcoverage,however,decreasesiftheactualtumormotionmovesbeyondPTV. Therefore, 4D-CT or MRI shouldbe employedto evaluatethe extent of pancreatic tumor motion. Instead of a universal margin, the ITV should be used to take into account the pancreatic tumor motion. Author Disclosure: J. Shen, None; J.M. Metz, None; T. Zhu, None; J. Panetta, None; M.X. Welliver, None; J. Plastaras, None; V. BarAd, None; S. Both, None.