扫描中心对体型特异性辐射剂量及图像噪声影响的体模实验研究  

The effect of scanning center on the size-specific dose estimates and image quality:a phantom study

作　　者：陈迢 张照喜[1] 彭伟[1] 郑丽丽[1] 陈浩[1] 贺瑶瑶 袁子龙[1] CHEN Tiao;ZHANG Zhaoxi;PENG Wei;ZHENG Lili;CHEN Hao;HE Yaoyao;YUAN Zilong(Depurtment of Radiology,Hubei Cancer Hospital,Wuhan 430079,China)

机构地区：[1]湖北省肿瘤医院放射科,湖北武汉430079

出　　处：《实用放射学杂志》2020年第3期479-482,共4页Journal of Practical Radiology

基　　金：科技部国家重点专项计划项目(2016YFC0103400)。

摘　　要：目的通过不同中心的头部、胸部及腹部CT扫描,探讨偏中心扫描对基于水等效直径(WED)的体型特异性剂量估计(SSDEWED)及图像质量的影响。方法利用螺旋CT对仿真人体模型进行头部、胸部及腹部不同中心扫描(检查床高度),头部扫描分别以外耳孔(0 cm)及其上、下各±2 cm及±4 cm为扫描中心,胸部及腹部则以腋中线(0 cm)及其上、下各±2 cm和±4 cm为扫描中心。记录各部位不同扫描中心的容积CT剂量指数(CTDIVOL),然后分别选取头部眼球最大层面、胸部、腹部中间层面图像,并记录体表最小ROI的平均CT值及面积,同时计算SSDEWED,并通过皮尔森相关性分析计算SSDEWED与床高的相关性。选取大小为2 cm^2圆形ROI测量该层面内密度均匀软组织区域CT值2次,记录其标准差(SD),以SD作为图像噪声。结果头部中心扫描时(0 cm)辐射剂量SSDEWED为79.09 mGy,床高增加4 cm(+4 cm)时,辐射剂量增加至84.14 mGy,床高降低4 cm(-4 cm)时,辐射剂量减少至75.22 mGy;胸部及腹部中心扫描时辐射剂量SSDEWED分别为8.17 mGy和7.97 mGy,床高增加3 cm(+3 cm)时,辐射剂量分别增加至9.40 mGy和9.40 mGy,床高降低4 cm(-4 cm)时,辐射剂量分别减少至6.92 mGy和6.64 mGy,各部位SSDEWED与床高线性相关(P<0.05);床高最高时噪声最小,床高最低时噪声最大。结论偏中心扫描主要通过影响CTDIVOL值进而造成SSDEWED的改变,因此正确选择扫描中心对患者辐射剂量的估算及图像质量均有重要意义。Objective To investigate the influence of searrning center on water equivalent diameter(WED)based on size-specific dose estimates(SSDEwed)and image quality by CT scanning of head,thorax and abdomen in different centers.Methods The anthropomorphic phantom,including head,thorax and abdomen were scanned at different center(table height),respectively.Head scanning was followed by the center of the external ear hole(0 cm)as the baseline,and was supplemented with 2 cm and 4 cm upward and downward the baseline as the scanning center.Similarly,thorax and abdomen were scanned with axillary midline at the center(0 cm),axillary midline up+2 cm,+4 cm and axillary midline down-2 cm,-4 cm,respectively.The volume CT dose index(CTDIvol)of each scanning center was recorded.Then,the average CT value and areas of the ROI fitted to the border of the phantom was recorded by selecting the images of the maximal cross-sectional image of the orbital center,and the middle level of thorax and abdomen.The SSDEwed was calculated and the correlation between SSDEwed and table height was calculated by Pearson correlation analysis.The CT value of the uniform soft tissue was obtained by measuring ROIs with a size of 2 cm^2 twice,and the standard deviation(SD)was recorded.Thus,SD was used as the image noise.Results The radiation dose SSDEwed were 79.09 mGy when the head center scanning(0 cm)was performed.When table height increased by 4 cm(+4 cm),the radiation dose in creased to 84.14 mGy.While the table height decreased by 4 cm(-4 cm),the radiati on dose decreased to 75.22 mGy.When the thorax and abdome n cen ter scan ning were performed,the radiation dose(SSDEWED)was 8.17 mGy and 7.97 mGy,respectively.When the table height increased by 3 cm(-3 cm),the radiation dose increased to 9.40 mGy and 9.40 mGy,respectively.While the table height decreased by 4 cm(-4 cm),the radiation dose decreased to 6.92 mGy and 6.64 mGy,respectively.The SSDEwed of each part was linearly related to table height(P<0.05).When the table height was the highest,the noise was

关 键 词：水等效直径 体型特异性剂量估计 辐射剂量 扫描中心 

分 类 号：R814.49[医药卫生—影像医学与核医学] R814.42[医药卫生—放射医学]