不同体型特异性剂量估算值在儿童腹部CT检查中的应用

Application of different SSDE in abdomen CT of children

目的:比较儿童腹部CT检查时体型特异性剂量估算值(SSDE)[水当量直径(Dw),SSDEDw]和SSDE[有效直径(De),SSDEDe]间的差别,找出简便且能准确直观反映儿童腹部CT检查辐射剂量的方法。方法:前瞻性选取128例行腹部CT检查的0~16岁患儿,依据患儿年龄将其分为0~3岁组(39例)、4~7岁组(43例)和8~16岁组(46例)。从Extended BrillianceTM Workspace工作站剂量报表获得三组患儿的平均容积CT剂量指数(CTDIVOL),测量并计算三组患儿腹部前后径(AP)和左右径(LAT)的De,依据De对应的转换因子(fDe)得到SSDEDe;分析三组患儿组间De、Dw、fDe、fDw、SSDEDe及SSDEDw,比较三组患儿组内SSDEDe和SSDEDw计算方法下的直径、转换因子和SSDE。结果:三组患儿在De、Dw、fDe、fDw、CTDIVOL、SSDEDe及SSDEDw间的差异均有统计学意义(F=140.5,F=121.8,F=79.8,F=69.1,F=67.2,F=109.2,F=171.6;P<0.05);随着患儿年龄增大,De、Dw增大,而fDe、fDw、SSDEDe及SSDEDw减小;0~3岁组患儿De高于Dw10.3%,fDe低于fDw12.4%,SSDEDe低于SSDEDw13.1%,差异均有统计学意义(t=4.59,t=6.27,t=5.84;P<0.05);4~7岁组患儿De高于Dw10%,fDe低于fDw11.8%,SSDEDe低于SSDEDw的12.9%,差异均有统计学意义(t=6.37,t=5.94,t=4.57;P<0.05);8~16岁组患儿De高于Dw9.8%,fDe低于fDw10.4%,SSDEDe低于SSDEDw10.5%,差异均有统计学意义(t=8.42,t=6.09,t=5.61;P<0.05)。0~3岁组患儿SSDEDe、SSDEDw与平均SSDEDw(SSDEg)呈正相关(r=0.90,r=0.91;P<0.05);4~7岁组患儿SSDEDe、SSDEDw与SSDEg呈正相关(r=0.89,r=0.92;P<0.05);8~16岁组患儿SSDEDe、SSDEDw与SSDEg呈正相关(r=0.88,r=0.90;P<0.05)。结论:SSDEDw能更精确评估患儿的辐射剂量;腹部CT图像中间层面的SSDEDw是反映患儿辐射剂量简单准确的代表参数。

Objective:To compare the difference between water-equivalent diameter of size-specific dose estimate(SSDEDw)and effective diameter of SSDEDe(SSDEDe)in abdomen CT examination of children so as to find out a simple and intuitive method to reflect the radiation dose of abdomen CT examination on children.Methods:128 children(0-16 years)who underwent abdomen CT scan were prospectively selected.And they were divided into 0-3 years group(39 cases),4-7 years group(43 cases)and 8-16 years group(46 cases)according to ages of them.The average volume CT dose indexes(CTDIVOL)of three groups were obtained from the dose report forms of Extended BrillianceTM Workspace workstation.And the De of antero-posterior(AP)diameter and lateral(LAT)diameter of abdomen of three groups were measured and calculated.SSDE DE was obtained by the conversion factor(fDe)that was corresponding to De.And the De,Dw,fDe,fDw,SSDEDe and SSDEDw among three groups were analyzed.And the intra-group diameter,conversion factor and SSDE under SSDE De and SSDEDw of three group were compared.Results:The differences of De,Dw,fDe,fDw,CTDIVOL,SSDEDe and SSDEDw among three groups were significant(F=140.5,F=121.8,F=79.8,F=69.1,F=67.2,F=109.2,F=171.6,P<0.05).With the increasing of age,the De and Dw increased,while the fDe,fDw,SSDEDe and SSDEDw decreased.In 0-3 years group,De was higher 10.3%than Dw,fDe was lower 12.4%than f Dw and SSDEDe was lower 13.1%than SSDEDw,and the differences of them were significantly(t=4.59,t=6.27,t=5.84,P<0.05).In 4-7 year group,De was higher 10%than Dw,f De was lower 11.8%than fDw,SSDEDe was lower 12.9%than SSDEDw,the differences of them were significant(t=6.37,t=5.94,t=4.57,P<0.05).In 8-16 years group,De was higher 9.8%than Dw,f De was lower 10.4%than fDw,and SSDEDe was lowere 10.5%than SSDEDw(t=8.42,t=6.09,t=5.61,P<0.05).In 0-3 years group,SSDE De and SSDEDw were positively correlated with mean of SSDEDw(SSDEg)(r=0.90,r=0.91,P<0.05).In 4-7 years group,SSDE De and SSDEDw were positively correlated with mean of SSDEDw(SSDEg)(r=0.89,r=0.92,P<0.05).In 8-16 years group,SSDE De and SSDEDw were positively correlated with mean of SSDEDw(SSDEg)(r=0.88,r=0.90,P<0.05).Conclusion:SSDE Dw can more accurately assess the radiation dose on children;SSDE Dw at the middle lay of abdomen CT image is a simply and accurately representative parameter that reflects radiation dose on children.