Vakili Shahabeddin, Shahbazi-Gahrouei Daryoush, Pourasbaghi Parastoo, Raeisi Elham
Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.
Department of Medical Physics, School of Medicine, Tarbiat Modares University, Tehran, Iran.
World J Nucl Med. 2021 Aug 20;20(4):342-348. doi: 10.4103/wjnm.wjnm_122_20. eCollection 2021 Oct-Dec.
The ventilation/perfusion (V/Q) single-photon emission computed tomography is the first method of diagnosis for pulmonary embolism in pregnant women. This study aimed to calculate the fetal absorbed dose and compare to recommended values in V/Q scan at three trimesters of pregnancy by Monte Carlo simulation (code MCNPX) using simulated phantoms, based on the adult female MIRD phantom. The collection of pregnant women phantoms (that of Stabin) was designed with changes in the MIRD phantom. Source organs were defined for each of the radiopharmaceuticals used in two scans, Xe and Kr for the lung and bladder and technetium diethylene-triamine-pentaacetate (Tc-DTPA) aerosol for lung ventilation scan. Also, technetium macroaggregated albumin (Tc-MAA) for lung ventilation scan, lung, bladder, and liver. Fetal absorbed dose was calculated and evaluated for the administration radiopharmaceuticals using the MCNP simulation output. For 200 MBq Tc-MAA, fetal absorbed dose was 1.01-1.97 mGy, which is higher than the values recommended by International Commission on Radiological Protection (ICRP). The same fetal absorbed dose was found for activities of 54 and 70 MBq in the third trimester. For Tc-DTPA-aerosol, fetal absorbed dose as a ventilation tracer was within the permitted range. For Xe and Kr, it was negligible. It is concluded that the fetus received the highest absorbed dose in the third trimester of pregnancy. For this reason, in this period of pregnancy, it is recommended to use the lower administration activity and her awareness must be done.
通气/灌注（V/Q）单光子发射计算机断层扫描是孕妇肺栓塞的首要诊断方法。本研究旨在通过基于成年女性MIRD体模的模拟体模，利用蒙特卡罗模拟（代码MCNPX）计算胎儿吸收剂量，并与妊娠三期V/Q扫描的推荐值进行比较。孕妇体模（Stabin体模）是在MIRD体模的基础上进行设计改变而收集的。为两次扫描中使用的每种放射性药物定义了源器官，肺部和膀胱扫描用的Xe和Kr，以及肺部通气扫描用的锝二乙三胺五乙酸（Tc-DTPA）气雾剂。此外，肺部通气扫描用的锝大颗粒白蛋白（Tc-MAA），以及肺部、膀胱和肝脏。利用MCNP模拟输出计算并评估给药放射性药物的胎儿吸收剂量。对于200 MBq的Tc-MAA，胎儿吸收剂量为1.01-1.97 mGy，高于国际放射防护委员会（ICRP）推荐的值。在妊娠晚期，54和70 MBq活度时的胎儿吸收剂量相同。对于Tc-DTPA气雾剂，作为通气示踪剂的胎儿吸收剂量在允许范围内。对于Xe和Kr，其剂量可忽略不计。结论是胎儿在妊娠晚期接受的吸收剂量最高。因此，在妊娠这个阶段，建议使用较低的给药活度，并且必须让孕妇知情。
