Abstract

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Title:: Effects of Body search strategy on dosimetric calculations for PTV and OAR in radiotherapy

Author(s):: YAO Kaining; WANG Ruoxi; YUE Haizhen; WANG Meijiao; WANG Hanlin; GONG Jian; ZHANG Yibao; WU Hao; Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiotherapy, Peking University Cancer Hospital & Institute, Beijing 100142, China

Keywords:: Keywords: whole-brain radiotherapy search strategy Body immobilization with double-sided mask dosimetric difference

Abstract:: Abstract: Objective To analyze the effects of the volume differences introduced by the parameter setting of automatic Body search strategy on the dosimetric calculations for planning target volume (PTV) and organs-at-risk in patients immobilization with double-sided mask. Methods Twenty-five patients immobilized with double-sided mask for whole-brain radiotherapy were enrolled in the study. Keeping the other parameters unchanged, the Body search conditions (smoothing level, CT value threshold and post-processing method) were changed for dose calculation. A total of 9 treatment schemes were designed. The dosimetric differences in PTV and organs-at-risk between parameter-changed plans and Default plan were analyzed. Results The smoothing level and CT values had significant effects on the dosimetric parameters of Body and PTV. In DSL0, DSL1, DSL2, HU-550 and HU-750 plans, the Dmean of PTV and the Dmax of Body was changed obviously. The average change in Body Dmean exceeded 400 cGy in HU-750 plan. Conclusion The default Body search strategy in the Eclipse treatment planning system is not suitable for all situations. The Body search under low smoothness and low HU has a great effect on dose calculation. For the patient immobilized with double-sided mask for whole-brain radiotherapy, the recommended smoothness level and HU threshold are 1 and -550 HU, respectively.