铋屏蔽联合器官管电流调制技术在颅脑CT检查中应用的体模研究

The phantom study of bismuth shielding combined with organ tube current modulation in brain CT

目的通过测量敏感器官的辐射剂量,评价铋屏蔽联合器官-管电流调制(X-care)技术在颅脑CT扫描中的应用价值。方法使用德国德国西门子公司炫速双源CT对头颈体模进行相同容积CT剂量指数(CTDIvol)下的X-care、铋屏蔽和X-care联合铋屏蔽3种方式扫描颅脑,及无铋屏蔽和铋屏蔽2种方式扫描双能量CT血管造影(DE-CTA)。选取铋屏蔽所在层面测量脑血管、邻近脑组织及脑脊液的CT值以及图像噪声,计算脑血管和脑实质的对比噪声比。通过放置热释光个人剂量计(TLD)的方式计算器官剂量当量(HT),并记录每次扫描后生成的CTDIvol和剂量长度乘积(DLP)。结果颅脑扫描在相同的CTDIvol下,采用X-care、铋屏蔽和X-care联合铋屏蔽3种扫描方法的HT,晶状体均值分别为(37.89±2.00)、(42.20±2.96)、(28.21±1.31)mSv,较颅脑常规序列扫描有明显下降(F=186.52,P<0.05);采用铋屏蔽和X-care联合铋屏蔽,HT,甲状腺为(0.77±0.07)和(0.89±0.08)mSv,较颅脑常规扫描和仅采用X-care有明显下降(F=103.26,P<0.05);DE-CTA采用铋屏蔽扫描后HT,晶状体和HT,甲状腺分别为(11.56±1.04)和(0.32±0.03)mSv,较屏蔽前有明显下降(t=5.07,P<0.05)。用与不用X-care、铋屏蔽及X-care联合铋屏蔽,颅脑常规扫描的噪声和对比信噪比(CNR)值无显著性改变;用与不用铋屏蔽,双能量CTA扫描的噪声和CNR无显著性改变。结论铋屏蔽联合器官管电流调制技术能够在保证一定图像质量的前提下,降低颅脑CT扫描中晶状体及甲状腺的器官剂量当量。

Objective To evaluate the application value of bismuth shielding combined with organ tube current modulation(X-care)in brain CT scanning by measuring the radiation dose of sensitive organs.Methods The head and neck phantom was scanned with Siemens dual source CT at the same volume CT dose index(CTDIvol)by X-care,bismuth shielding and x-care combined with bismuth shielding,and by dual energy CT angiography(DE-CTA)with and without bismuth shielding.The CT values of cerebral vessels,adjacent brain tissues and cerebrospinal fluid and image noise were measured,and the contrast noise ratio of cerebral vessels and brain parenchyma was calculated.Organ dose equivalent(HT)was calculated by placing thermoluminescent personal dosimeter(TLD),and CTDIvol and dose length product(DLP)were recorded after each scan.Results Under the same CTDIvol,the mean values of HT,lens with X-care,Bi shielding and X-care combined with Bi shielding were(37.89±2.00),(42.20±2.96)and(28.21±1.31)mSv,respectively,significantly lower than those of conventional sequence scanning(F=186.52,P<0.05).The values of HT,thyroid with Bi shielding and X-care combined with Bi shielding were(0.77±0.07)and(0.89±0.08)mSv,lower than those of routine brain scan and X-care(F=103.26,P<0.05).The values of HT,lens and HT,thyroidof DE-CTA with bismuth shielding were(11.56±1.04)and(0.32±0.03)mSv,respectively,significantly lower than those without bismuth shielding(t=5.07,P<0.05).There was no significant difference in noise and CNR in routine brain scan between with and without X-care,bismuth shielding and X-care combined with bismuth shielding.There was no significant difference in noise and CNR in dual energy CTA scanning between with and without Bi shielding.Conclusions Using bismuth shielding and organ tube current modulation,we can significantly reduce organ dose of lens and thyroid during brain CT scanning without sacrificing the image quality.