基于小鼠全身动态PET扫描估算16α-18F-17β-雌二醇的人体内辐射剂量

背景与目的：由小鼠全身动态PET显像数据获得药物在小鼠体内的生物分布，利用器官内剂量评估/指数模型分析软件(organ level inter dose assessment/exponential model，OLINDA/EXM)估算18F-fluo-roestradiol，18F-FES)在人体内的吸收剂量、全身有效剂量和有效剂量当量。方法：健康雌性KM小鼠尾静脉注射18F-FES后行160 min动态PET采集，经3D-OSEM/MAP算法重建获得PET图像。再行高分辨率CT显像，在PET/CT融合图像上，选取各脏器勾画感兴趣体积(volume of interest，VOI)，获得相应时间-活度曲线和其曲线下面积、滞留时间、成年女性体模对应各器官的滞留时间。依据美国核医学会医用内照射剂量学委员会提出的内照射剂量计算方法(MIRD体系)，利用OLINDA/EXM软件计算18F-FES在人体内的吸收剂量、全身有效剂量和有效剂量当量。最后所得数据与已公开发表计算18F-FES内照射剂量的文献数据行配对t检验，验证本文方法的有效性。结果：人体内胆囊壁、膀胱壁、小肠、上部大肠和肝脏的吸收剂量最高，分别为0.0725、0.0445、0.0430、0.0315和0.0282 mGy/MBq。大脑、皮肤、乳腺、心脏壁和甲状腺吸收剂量最低，分别为0.0052、0.0011、0.0012、0.0012和0.0013 mGy/MBq。对放射性敏感的器官如骨原细胞、胸腺和红骨髓的吸收剂量均较低，范围为0.0014~0.0218 mGy/MBq。全身平均吸收剂量为0.0147 mGy/MBq，全身有效剂量当量为0.0250 mGy/MBq，全身有效剂量为0.0190 mSv/MBq。对于常规注射185 MBq18F-FES，人体有效剂量为3.5150 mSv。与直接测量18F-FES在健康人体各主要脏器内吸收剂量的文献行配对t检验，差异无统计学意义(t=1.478，P=0.153)。结论：利用OLINDA/EXM软件根据小鼠全身动态PET/CT数据可有效估算18F-FES在人体内的吸收剂量和有效剂量。18F-FES可安全地用于人体，其有效剂量低于允许范围上限。该研究可为临床放心使用18F-FES提供依据。

Radiation dosimetry estimates of18F-fluoroestradiol based on whole-body PET imaging of mice

Background and purpose:In preparation for using this tracer in humans, this study estimated thedosimetry of18F-FES with the method established by MIRD based on whole-body PET imaging of mice.Methods:Three female mice receivedⅣ tail injections of18F-FES and were scanned for 160 min in an Inveon dedicated PET/CT scanner. This study selected some important organs (brain, lung, liver, heart wall, small intestine, large intestine, kidney and urinary bladder), computed their residence times. Then, the residence times in mice organs were converted to human values using scale factors based on differences between organ and body weights. OLINDA/EXM 1.1 software was used to compute the absorbed human doses in multiple organs for both adult female and adult male body phantoms. Results:The highest absorbed doses in gallbladder wall, urinary bladder wall, small intestine, upper large intestine and liver are 0.072 5, 0.044 5, 0.043 0, 0.031 5 and 0.028 2 mGy/MBq, respectively. The organs which have the lowest ab-sorbed doses were brain (0.005 2 mGy/MBq), followed by skin (0.001 1 mGy/MBq), breast (0.001 1 mGy/MBq), heart wall (0.001 2 mGy/MBq) and thyroid (0.001 2 mGy/MBq). The mean absorbed doses for the other major organs ranged from 0.009 5 to 0.023 5 mGy/MBq. The total mean effective dose is 0.019 0 mSv/MBq and the mean effective doses equivalent is 0.025 0 mGy/MBq. A 370-MBq injection of18F-FES leads to an estimated effective dose of 7.03 mSv for the female. There was no statistical difference in the doses results obtained from direct measurement of18F-FES ab-sorption in normal people between previous publications by others and our work.Conclusion:The whole-body mouse imaging can be used as a preclinical tool for initial estimation of the absorbed doses of18F-FES in humans. Furthermore, the potential radiation risk associated with18F-FES imaging is well within the accepted limits.