Department of Radiology, Duke University Medical Center, Durham, NC 27710, USA.
AJR Am J Roentgenol. 2010 Aug;195(2):433-8. doi: 10.2214/AJR.09.3957.
The purpose of this study was to determine, using an anthropomorphic phantom, whether patients are subject to variable radiation doses based on scanner assignment for routine CT of the brain.
Twenty metal oxide semiconductor field effect transistor dosimeters were placed in the brain of a male anthropomorphic phantom scanned three times with a routine clinical brain CT protocol on four scanners from one manufacturer in four configurations and on one 64-MDCT scanner from another manufacturer. Absorbed organ doses were measured for skin, cranium, brain, lens of the eye, mandible, and thyroid. Effective dose was calculated on the basis of the dose-length product recorded on each scanner.
Organ dose ranges were as follows: cranium, 2.57-3.47 cGy; brain, 2.34-3.78 cGy; lens, 2.51-5.03 cGy; mandible 0.17-0.48 cGy; and thyroid, 0.03-0.28 cGy. Statistically significant differences between scanners with respect to dose were recorded for brain and lens (p < 0.05). Absorbed doses were lowest on the single-detector scanner. In the comparison of MDCT scanners, the highest doses were found on the 4-MDCT scanner and the dual-source 64-MDCT scanner not capable of gantry tilt. Effective dose ranged from 1.22 to 1.86 mSv.
According to the phantom data, patients are subject to different organ doses in the lens and brain depending on scanner assignment. At our institution with existing protocols, absorbed doses at brain CT are lowest with the single-detector CT scanner, followed by MDCT scanners capable of gantry tilt. On scanners without gantry tilt, CT of the brain should be performed with careful head positioning and shielding of the orbits. These precautions are especially true for patients who need repeated scanning and for pediatric patients.
本研究旨在通过人体模型确定，根据扫描仪分配情况，患者在进行常规脑部 CT 时是否会受到不同的辐射剂量。
将 20 个金属氧化物半导体场效应晶体管剂量计放置在一名男性人体模型的脑部，该模型使用常规临床脑部 CT 协议，在一家制造商的四台扫描仪上以四种配置进行三次扫描，并在另一家制造商的一台 64 排多层 CT 扫描仪上进行一次扫描。测量皮肤、颅骨、脑部、眼睛晶状体、下颌骨和甲状腺的器官吸收剂量。根据每个扫描仪记录的剂量长度乘积计算有效剂量。
器官剂量范围如下：颅骨 2.57-3.47 cGy；脑部 2.34-3.78 cGy；晶状体 2.51-5.03 cGy；下颌骨 0.17-0.48 cGy；甲状腺 0.03-0.28 cGy。在剂量方面，扫描仪之间存在统计学差异，脑部和晶状体有差异（p < 0.05）。单探测器扫描仪的吸收剂量最低。在多层 CT 扫描仪的比较中，4 排多层 CT 扫描仪和不能进行机架倾斜的双源 64 排多层 CT 扫描仪的剂量最高。有效剂量范围为 1.22-1.86 mSv。
根据体模数据，患者在进行脑部 CT 时，根据扫描仪的分配，眼部晶状体和脑部会受到不同的器官剂量。在我们机构的现有方案中，单探测器 CT 扫描仪的脑部 CT 吸收剂量最低，其次是能够进行机架倾斜的多层 CT 扫描仪。在没有机架倾斜的扫描仪上，进行脑部 CT 时应仔细定位头部并对眼眶进行屏蔽。对于需要重复扫描的患者和儿科患者，这些预防措施尤其重要。
