Kelaranta Anna, Kaasalainen Touko, Seuri Raija, Toroi Paula, Kortesniemi Mika
HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, PO Box 340, FI-00290 Helsinki, Finland Department of Physics, University of Helsinki, PO Box 64, FI-00014 Helsinki, Finland
HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, PO Box 340, FI-00290 Helsinki, Finland Department of Physics, University of Helsinki, PO Box 64, FI-00014 Helsinki, Finland.
Radiat Prot Dosimetry. 2015 Jul;165(1-4):226-30. doi: 10.1093/rpd/ncv097. Epub 2015 Apr 1.
The connection between recorded volumetric CT dose index (CTDI vol) and determined mean fetal dose (Df) was examined from metal-oxide-semiconductor field-effect transistor dose measurements on an anthropomorphic female phantom in four stages of pregnancy in a 64-slice CT scanner. Automated tube current modulation kept the mean Df fairly constant through all pregnancy stages in trauma (4.4-4.9 mGy) and abdomino-pelvic (2.1-2.4 mGy) protocols. In pulmonary angiography protocol, the mean Df increased exponentially as the distance from the end of the scan range decreased (0.01-0.09 mGy). For trauma protocol, the relative mean Df as a function of gestational age were in the range 0.80-0.97 compared with the mean CTDI vol. For abdomino-pelvic protocol, the relative mean Df was 0.57-0.79 and for pulmonary angiography protocol, 0.01-0.05 compared with the mean CTDI vol, respectively. In conclusion, if the fetus is in the primary beam, the CTDI vol can be used as an upper estimate of the fetal dose. If the fetus is not in the primary beam, the fetal dose can be estimated by considering also the distance of the fetus from the scan range.
通过在64层CT扫描仪中对处于四个孕期阶段的女性体模进行金属氧化物半导体场效应晶体管剂量测量，研究了记录的容积CT剂量指数（CTDI vol）与确定的胎儿平均剂量（Df）之间的关系。自动管电流调制使创伤（4.4 - 4.9 mGy）和腹盆腔（2.1 - 2.4 mGy）扫描方案在所有孕期阶段的胎儿平均剂量保持相当恒定。在肺血管造影扫描方案中，随着距扫描范围末端距离的减小，胎儿平均剂量呈指数增加（0.01 - 0.09 mGy）。对于创伤扫描方案，与平均CTDI vol相比，胎儿相对平均剂量随孕周的变化范围为0.80 - 0.97。对于腹盆腔扫描方案，相对平均Df为0.57 - 0.79，对于肺血管造影扫描方案，与平均CTDI vol相比分别为0.01 - 0.05。总之，如果胎儿位于主射束中，CTDI vol可作为胎儿剂量的上限估计值。如果胎儿不在主射束中，则还需考虑胎儿与扫描范围的距离来估计胎儿剂量。
