Jaffe Tracy A, Yoshizumi Terry T, Toncheva Greta I, Nguyen Giao, Hurwitz Lynne M, Nelson Rendon C
Department of Radiology, Duke University Medical Center, Erwin Rd., Box 3808, Durham, NC 27710, USA.
AJR Am J Roentgenol. 2008 Apr;190(4):860-4. doi: 10.2214/AJR.07.2925.
The objective of our study was to correlate the estimated fetal absorbed radiation dose derived by directly measured uterine doses in the early first trimester and the volume CT dose index (CTDI(vol)) for 16-MDCT of the maternal chest, abdomen, and pelvis.
Estimated absorbed fetal dose was measured using a metal oxide semiconductor field effect transistor (MOSFET) dosimeter that was placed in the uterus of an adult female anthropomorphic phantom. The phantom was scanned on a 16-MDCT scanner using three protocols. The scanning parameters for protocol A (trauma) were detector configuration, 16 x 0.625 mm; pitch, 1.75:1; rotation time, 0.5 second; 140 kVp; and 340 mA. The scanning parameters for protocol B (CT angiography) were detector configuration, 16 x 1.25 mm; pitch, 1.38:1; rotation time, 0.6 second; 140 kVp; and 300 mA. The scanning parameters for protocol C, which is the automated tube current modulation (ATCM) protocol previously used in the literature, were detector configuration, 16 x 1.25 mm; pitch, 0.938:1; rotation time, 0.5 second; 140 kVp; and 380 mA. The protocols were also modified for the ATCM mode; the CTDI(vol) was documented from the scanner's console. Correlation between these data was tested with a goodness-of-fit model.
Absorbed fetal radiation dose in the early first trimester correlated with the CTDI(vol) via a linear regression equation. For a constant tube current and peak voltage of 140 kVp, fetal dose (mGy) = 1.665 x CTDI(vol) (mGy) - 7.059. For the ATCM mode and a constant kVp of 140, fetal dose (mGy) = 2.151 x CTDI(vol) (mGy) - 2.200. The goodness of fit (R(2)) for the equations is 0.99 and 0.91, respectively.
In both the manual and ATCM modes, absorbed fetal radiation dose can be estimated from the CTDI(vol) obtained at the time of scanning independent of pitch and tube current-time product (mAs).
我们研究的目的是将孕早期通过直接测量子宫剂量得出的胎儿吸收辐射剂量，与用于孕妇胸部、腹部和骨盆的16层螺旋CT（MDCT）的容积CT剂量指数（CTDI(vol)）相关联。
使用置于成年女性人体模型子宫内的金属氧化物半导体场效应晶体管（MOSFET）剂量仪测量估计的胎儿吸收剂量。该模型在16层螺旋CT扫描仪上采用三种扫描方案进行扫描。方案A（创伤）的扫描参数为：探测器配置，16×0.625毫米；螺距，1.75:1；旋转时间，0.5秒；140千伏峰值电压（kVp）；340毫安。方案B（CT血管造影）的扫描参数为：探测器配置，16×1.25毫米；螺距，1.38:1；旋转时间，0.6秒；140 kVp；300毫安。方案C是文献中先前使用的自动管电流调制（ATCM）方案，其扫描参数为：探测器配置，16×1.25毫米；螺距，0.938:1；旋转时间，0.5秒；140 kVp；380毫安。这些方案也针对ATCM模式进行了修改；CTDI(vol)从扫描仪控制台记录。用拟合优度模型测试这些数据之间的相关性。
孕早期胎儿吸收辐射剂量通过线性回归方程与CTDI(vol)相关。对于管电流和峰值电压为140 kVp的情况，胎儿剂量（毫戈瑞，mGy）= 1.665×CTDI(vol)（mGy） - 7.059。对于ATCM模式和恒定kVp为140的情况，胎儿剂量（mGy）= 2.151×CTDI(vol)（mGy） - 2.200。这些方程的拟合优度（R²）分别为0.99和0.91。
在手动和ATCM模式下，均可根据扫描时获得的CTDI(vol)估计胎儿吸收辐射剂量，而与螺距和管电流 - 时间乘积（mAs）无关。
