Beam Characteristics at Low Dose Monitor Unit Settings for Vero4DRT

作     者：Hideharu Miura Shuichi Ozawa Shintaro Tsuda Masahiro Hayata Kiyoshi Yamada Yasushi Nagata 

作者机构：Hiroshima High-Precision Radiotherapy Cancer Center Hiroshima Japan Department of Radiation Oncology Institute of Biomedical & Health Science Hiroshima University Hiroshima Japan 

出 版 物：《International Journal of Medical Physics, Clinical Engineering and Radiation Oncology》 (医学物理学、临床工程、放射肿瘤学（英文）)

年 卷 期：2015年第4卷第4期

页      面：284-289页

学科分类：1002[医学-临床医学] 100214[医学-肿瘤学] 10[医学] 

主　　题：Vero4DRT Step-and-Shoot IMRT Low Monitor Unit Beam Characteristic 

摘      要：The stability of delivery of low monitor unit (MU) setting is important especially for step-and-shoot intensity-modulated radiotherapy (IMRT), because the nature of the technique is inherent to repeat beam on/off according to the number of the segments. This study evaluates the dose linearity and profile flatness/symmetry under low MU settings for Vero4DRT, a new linear-accelerator based irradiation system that currently implements step-and-shoot IMRT. To evaluate the dose linearity and flatness/symmetry, the point doses and beam profiles were measured as functions of MU and dose rates. The accuracy of dose delivery depended on the dose rate. Under all dose rates, the dose was linear within 1% above 5 MU and within 2% above 3 MU. The beam symmetry was degraded in-line compared with crossline, although both profiles were symmetric within 2% at all dose settings. The profile flatness was also within 2% above 5 MU at any dose rate and showed no significant variation among the low MU settings. To ensure stable beam delivery without increasing the treatment time of Vero4DRT, we recommend a delivery of 5 MU per segment at a dose rate of 500 MU/min.