Mayo Clinic Rochester, 200 First St, SW, Rochester, MN 55905, USA.
AJR Am J Roentgenol. 2010 Apr;194(4):881-9. doi: 10.2214/AJR.09.3462.
The objective of our study was to compare dose-length product (DLP)-based estimates of effective dose with organ dose-based calculations using tissue-weighting factors from publication 103 of the International Commission on Radiological Protection (ICRP) or dual-energy CT protocols.
Using scanner- and energy-dependent organ dose coefficients, we calculated effective doses for CT examinations of the head, chest, coronary arteries, liver, and abdomen and pelvis using routine clinical single- or dual-energy protocols and tissue-weighting factors published in 1991 in ICRP publication 60 and in 2007 in ICRP publication 103. Effective doses were also generated from the respective DLPs using published conversion coefficients that depend only on body region. For each examination type, the same volume CT dose index was used for single- and dual-energy scans.
Effective doses calculated for CT examinations using organ dose estimates and ICRP 103 tissue-weighting factors differed relative to ICRP 60 values by -39% (-0.5 mSv, head), 14% (1 mSv, chest), 36% (4 mSv, coronary artery), 4% (0.6 mSv, liver), and -7% (-1 mSv, abdomen and pelvis). DLP-based estimates of effective dose, which were derived using ICRP 60-based conversion coefficients, were less than organ dose-based estimates for ICRP 60 by 4% (head), 23% (chest), 37% (coronary artery), 12% (liver), and 19% (abdomen and pelvis) and for ICRP 103 by -34% (head), 37% (chest), 74% (coronary artery), 16% (liver), and 12% (abdomen and pelvis). All results were energy independent.
These differences in estimates of effective dose suggest the need to reassess DLP to E conversion coefficients when adopting ICRP 103, particularly for scans over the breast. For the evaluated scanner, DLP to E conversion coefficients were energy independent, but ICRP 60-based conversion coefficients underestimated effective dose relative to organ dose-based calculations.
本研究的目的是比较基于剂量长度乘积（DLP）的有效剂量估算值与基于出版物 103 号国际辐射防护委员会（ICRP）组织权重因子或双能 CT 协议的器官剂量计算值。
使用与扫描仪和能量相关的器官剂量系数，我们根据常规临床单能或双能协议，使用 1991 年 ICRP 出版物 60 号和 2007 年 ICRP 出版物 103 号中公布的组织权重因子，计算了头部、胸部、冠状动脉、肝脏和腹部及骨盆 CT 检查的有效剂量。还使用仅取决于身体部位的公布的转换系数，从各自的 DLP 生成有效剂量。对于每种检查类型，单能和双能扫描均使用相同的容积 CT 剂量指数。
使用器官剂量估算和 ICRP 103 组织权重因子计算的 CT 检查的有效剂量与 ICRP 60 值相比，分别降低了-39%（头部，-0.5 mSv）、14%（胸部，1 mSv）、36%（冠状动脉，4 mSv）、4%（肝脏，0.6 mSv）和-7%（腹部和骨盆，-1 mSv）。基于 ICRP 60 转换系数的 DLP 估算的有效剂量，分别比 ICRP 60 的器官剂量估算低 4%（头部）、23%（胸部）、37%（冠状动脉）、12%（肝脏）和 19%（腹部和骨盆），比 ICRP 103 低-34%（头部）、37%（胸部）、74%（冠状动脉）、16%（肝脏）和 12%（腹部和骨盆）。所有结果均与能量无关。
这些有效剂量估算值的差异表明，在采用 ICRP 103 时，需要重新评估 DLP 与 E 的转换系数，特别是对于乳房上方的扫描。对于评估的扫描仪，DLP 与 E 的转换系数与能量无关，但 ICRP 60 转换系数相对于器官剂量计算低估了有效剂量。
