CT扫描野内表面防护不同材料的防护效果以及对图像质量的影响

目的 评价两种表面防护材料在CT扫描野内的辐射防护效果和扫描野的图像质量。方法 使用CTDI模体测量颈部扫描时周边的辐射量及CTDI_w，采用铋屏蔽和硫酸钙屏蔽为辐射防护材料的辐射量及CTDI_w，比较有无屏蔽以及两种屏蔽的防护效果差异。低剂量CT筛查60例，随机分为3组，分别为无屏蔽组以及使用铋屏蔽和硫酸钙屏蔽防护组，自动曝光控制扫描，管电压100 kV，参考管电流为23 mAs。对患者甲状腺和肺尖层面的图像质量评分，比较屏蔽对图像质量的影响。结果 模型研究中，无屏蔽组的探测点辐射量为6.17±0.21 mGy；小于床板侧（7.61±0.14）mGy和中心侧为（7.14±0.11）mGy（P<0.01）；而屏蔽组CTDI_w均小于无屏蔽组，且铋屏蔽组和硫酸钙屏蔽组与无屏蔽组CTDI_w分别为5.78、5.02、6.92 mGy（P<0.05）。临床研究中，3组低剂量筛查的有效剂量分别为（0.92±0.05）、（0.90±0.06）、（0.90±0.05）mSv（P>0.05）。3组甲状腺和肺尖成像质量均可满足诊断要求，且屏蔽组的甲状腺成像质量评分明显低于无屏蔽组（F=14.69，P<0.01），其中硫酸钙屏蔽组评分最低；3组肺尖图像质量评分间差异没有统计学意义（F=1.57，P>0.05）。结论 铋屏蔽与硫酸钙屏蔽均可以作为肺癌CT筛查的甲状腺表面屏蔽使用，不影响肺组织诊断。

The protective efficiency of different materials and the effect on the imaging quality of CT scanning

Objective To evaluate the radiation protection effect of two surface protective materials and the image quality of scanning field in CT field.Methods Bismuth and calcium sulphate for radiation protection materials, The CTDI phantom is used to measure the amount of radiation and CTDIw around the neck during the scan with bismuth and calcium sulphate as radiation protection material or no protection material. Comparison of the shielding effect with or without shielding was performed. 60 patients administrated with low-dose CT screening and were randomly divided into 3 groups:unshielded group, bismuth shielded group and calcium sulfate shielded group, automatic exposure control scanning model was set and tube voltage as 100 kv and reference for 23 mAs tube current. The effect of shielding on image quality was compared with the image quality score of the patients' thyroid and lung.Results The radiation dose of the unshielded group was 6.17±0.21 mGy. It was less than 7.61±0.14 mGy and the center side of the bed side was 7.14±0.11 mGy (P<0.01); The CTDI_w of the shielding group was less than that of the unshielded group, and the CTDIw of the bismuth shielding group and the calcium sulfate group was 5.78 mGy, 5.02 mGy, and 6.92 mGy (P<0.05). In clinical studies, the effective dose of 3 groups of low-dose screening was 0.92±0.05 mSv, 0.90 ±0.06 mSv, 0.90±0.05 mSv (P>0.05). Three groups of thyroid and lung tip imaging quality were met the requirements of diagnosis, and shielding set of thyroid imaging quality score was lower than that in group without shielding (F=14.69, P<0.01), which the lowest score of calcium sulphate shielding group; There was no statistically significant difference between the quality scores of the three groups (F=1.57, P>0.05).Conclusion Both bismuth shielding and calcium sulfate shielding can be used as the thyroid surface radiation protection for lung cancer screening without affecting lung tissue diagnosis.