CT扫描床对受检患儿体型特异性辐射剂量估计方法影响的初步研究

To investigate the effect of scan table on CT size-specific dose estimate in children

目的探讨CT扫描床对儿童患者体型特异性辐射剂量估计(size-specific dose estimate, SSDE)的影响。方法回顾性收集在华中科技大学同济医学院附属湖北省肿瘤医院德国西门子公司SOMATOM Definition AS+ 64排128层CT机上行CT平扫的44例患儿,其中头部15例,胸部13例,腹盆腔16例;记录每位患儿的容积CT剂量指数(CTDIvol),并通过带及不带床板的方式对不同部位的图像进行勾画,计算带与不带床板的水等效直径(water equivalent diameter, WED)WED-T及WED-NT,最后计算出带与不带床板的SSDEWED-T及SSDEWED-NT,并用Bland-Altman软件以WED-NT及SSDEWED-NT作为参考来比较两种不同的方法所得到的WED和SSDEWED的差异。结果包含部分床板会导致WED值会被高估,在头部、胸部及腹盆部分别为0.10%、2.82%及2.54%;而SSDEWED值会被低估,分别是头部0.06%、胸部2.70%及腹盆腔1.59%。结论CT检查床板对患儿的SSDEWED存在一定的影响,在实际应用过程中应给予一定的关注。

Objective To investigate the effect of scan table on size-specific dose estimate (size-specific dose estimate, SSDE) in children′s CT scan. Methods CT imaging data and CTDIvol of 44 children (15 heads, 13 chests, 16 abdomen-pelvis) who underwent Siemens SOMATOM Definition AS+ 64 row 128-slice CT scan were retrospectively collected. CTDIvol of each patient was recored, WED (water equivalent diameter) was calculated by two different methods (with or without table), donated as WED-T and WED-NT, then the corresponding SSDEWED (SSDEWED-T and SSDEWED-NT) was calculated. And the SSDEWED-NT was used as reference to evaluate the difference between WED and SSDEWED obtained by two different methods. Results Including part of table will lead to the overestimate for WED, with mean differences of 0.10%, 2.82% and 2.54% for head, chest and abdomen-pelvis, respectively, while SSDEWED will be underestimated by 0.06%(head), 2.70%(chest) and 1.59%(abdomen-pelvis). Conclusions Including par of the patient table has a certain effect on SSDEWED for children, more attention should be paid for the application of SSDEWED.