Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan, ROC.
Medical Physics and Radiation Measurements Laboratory, Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan, ROC.
Sci Rep. 2017 Feb 27;7:43336. doi: 10.1038/srep43336.
The aim of this study was to understand the difference between the measured and calculated irradiation attenuations obtained using two algorithms and to identify the influence of couch attenuation on patient dose verification. We performed eight tests of couch attenuation with two photon energies, two longitudinal couch positions, and two rail positions. The couch attenuation was determined using a radiation treatment planning system. The measured and calculated attenuations were compared. We also performed 12 verifications of head-and-neck and rectum cases by using a Delta phantom. The dose deviation (DD), distance to agreement (DTA), and gamma index of pencil-beam convolution (PBC) verifications were nearly the same. The agreement was least consistent for the anisotropic analytical algorithm (AAA) without the couch for the head-and-neck case, in which the DD, DTA, and gamma index were 74.4%, 99.3%, and 89%, respectively; for the rectum case, the corresponding values were 56.2%, 95.1%, and 92.4%. We suggest that dose verification should be performed using the following three metrics simultaneously: DD, DTA, and the gamma index.
本研究旨在了解两种算法获得的测量和计算照射衰减之间的差异，并确定治疗床衰减对患者剂量验证的影响。我们进行了八项治疗床衰减测试，涉及两种光子能量、两种纵向治疗床位置和两种轨道位置。使用放射治疗计划系统确定治疗床衰减。比较测量值和计算值。我们还使用 Delta 体模对 12 例头颈部和直肠病例进行了验证。剂量偏差（DD）、符合度距离（DTA）和铅笔束卷积（PBC）伽玛指数验证几乎相同。对于没有治疗床的头颈部病例的各向异性分析算法（AAA），一致性最差，DD、DTA 和伽玛指数分别为 74.4%、99.3%和 89%；对于直肠病例，相应的值分别为 56.2%、95.1%和 92.4%。我们建议同时使用 DD、DTA 和伽玛指数这三个指标进行剂量验证。
