Abstract

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Title:: Errors of monitor units in step-and-shoot intensity-modulated radiotherapy plan

Author(s):: LI Xiaobo1; 2; CHEN Lifang3; ZHANG Jianping1; HUANG Miaoyun1; CHEN Yuangui1; XU Benhua1; 2; 1. Department of Radiation Oncology, Fujian Medical University Union Hospital, Fuzhou 350001, China; 2. Department of Medical Imaging Technology, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou 350001, China; 3. Department of Radiology, Fujian Medical University Union Hospital, Fuzhou 350001, China

Keywords:: ; Keywords: intensity-modulated radiotherapy; segments; monitor units; treatment planning system

Abstract:: Abstract: Objective To discuss the errors between planned delivered monitor units (PDM) and actual delivered monitor units (ADM) in three-dimensional step-and-shoot intensity-modulated radiotherapy (IMRT) plans and provide a reference for setting the minimum monitor units. Methods A total of 50 step-and-shoot IMRT plans with 4 842 segments were selected. For each segment, statistical analysis was performed on PDM and ADM, and the errors between PDM and ADM were determined. Results Significant differences were found between PDM average and ADM average (P<0.05). When PDM was relatively smaller, the relative errors between PDM and ADM were remarkably increased, and the maximum relative error reached 16.33%. Conclusion The error between PDM and ADM can’t be ignored in clinic. Under the premise of without affecting the planned dose distribution, when the error was within the acceptable limit of 5%, PDM should be greater than 8.49 MU; and when the error was within the acceptable limit of 3%, PDM should be greater than 14.46 MU.