Estimation of effective imaging dose and excess absolute risk of secondary cancer incidence for four‐dimensional cone‐beam computed tomography acquisition
Estimation of effective imaging dose and excess absolute risk of secondary cancer incidence for four‐dimensional cone‐beam computed tomography acquisition
复制标题
四维锥形束计算机断层扫描采集的有效成像剂量和继发性癌症发病率超绝对风险的估计
DOI：
10.1002/acm2.12741
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发表时间：
2019
影响因子：
2.1
通讯作者：
Fujimoto Koya
中科院分区：
文献类型：
--
作者：
Yuasa Yuki;Shiinoki Takehiro;Onizuka Ryota;Fujimoto Koya
本研究的目的是使用Monte Carlo模拟估计四维锥形束计算机断层扫描（4D-CBCT）的器官等效剂量和有效成像剂量，并评价继发性癌症发病率的超额绝对风险（EXAR）。EGSnrc/BEAMnrc用于模拟TrueBeam直线加速器的机载成像仪（OBI）。具体而言，基于百分比深度剂量对OBI进行建模，并使用三维（3D）水体模测量偏心率。对于临床病例，使用EGSnrc/DOSXYZnrc模拟15名肺癌和肝癌患者。使用治疗计划系统定量肺、胃、骨髓、食管、肝脏、甲状腺、骨表面、皮肤、肾上腺、胆囊、心脏、肠、肾脏、胰腺和脾脏的平均吸收剂量，并计算每个器官的等效剂量。随后，有效剂量计算为当量剂量的加权和，并使用电离辐射生物效应（BEIR）VII模型确定每个器官的继发性癌症发病率的百分比。在3D-CBCT（胸部、骨盆）和4D-CBCT模式下，肺的有效剂量分别为3.9 ± 0.5、15.7 ± 2.0和7.3 ± 0.9 mSv，肝脏的有效剂量分别为4.2 ± 0.6、16.7 ± 2.4和7.8 ± 1.1 mSv。男性和女性的肺部EAR分别为7.3和10.7例/百万人年，而肝脏EAR分别为9.9和4.5例/百万人年。随着照射时间的延长，辐射剂量增加。在临床研究中，我们应该基于有效剂量和继发癌发生率的考虑使用4D-CBCT。
This study was conducted to estimate the organ equivalent dose and effective imaging dose for four‐dimensional cone‐beam computed tomography (4D‐CBCT) using a Monte Carlo simulation, and to evaluate the excess absolute risk (EAR) of secondary cancer incidence. The EGSnrc/BEAMnrc were used to simulate the on‐board imager (OBI) from the TrueBeam linear accelerator. Specifically, the OBI was modeled based on the percent depth dose and the off‐center ratio was measured using a three‐dimensional (3D) water phantom. For clinical cases, 15 lung and liver cancer patients were simulated using the EGSnrc/DOSXYZnrc. The mean absorbed doses to the lung, stomach, bone marrow, esophagus, liver, thyroid, bone surface, skin, adrenal glands, gallbladder, heart, intestine, kidney, pancreas and spleen, were quantified using a treatment planning system, and the equivalent doses to each organ were calculated. Subsequently, the effective dose was calculated as the weighted sum of the equivalent dose, and the EAR of the secondary cancer incidence was determined for each organ with the use of the biologic effects of ionizing radiation (BEIR) VII model. The effective doses were 3.9 ± 0.5, 15.7 ± 2.0, and 7.3 ± 0.9 mSv, for the lung, and 4.2 ± 0.6, 16.7 ± 2.4, and 7.8 ± 1.1 mSv, for the liver in the respective cases of the 3D‐CBCT (thorax, pelvis) and 4D‐CBCT modes. The lung EARs for males and females were 7.3 and 10.7 cases per million person‐years, whereas the liver EARs were 9.9 and 4.5 cases per million person‐years. The EAR increased with increasing time since radiation exposure. In clinical studies, we should use 4D‐CBCT based on consideration of the effective dose and EAR of secondary cancer incidence.