Objective:To compare the differences between volumetric CT dose index(CTDIVOL)and size-specific dose estimate(SSDEDW)based on water equivalent diameter(DW)in radiation dose measurement and to explore a new method for fast calculation of SSDEDW.Methods:The imaging data of 1217 cases of head,1122 cases of chest,and 844 cases of abdomen-pelvis were analyzed retrospec-tively,and they were divided into four age groups:0～＜1 year、1～＜5 years、5～＜10 years and 10～＜15 years according to age.We manually measured the area of interest(AROI),CT value(CTROI),lat-eral diameter(LAT),and anteroposterior diameter(AP)of the median cross-sectional image of the standard scanning range,and the SSDEDW based on DW were calculated.The t-tests were used to com-pare the differences between CTDIVOL and SSDEDW in different age groups.Pearson correlation test were used to acquire the correlations between DE and age、DE and DW,conversion factor(f)and age.Median and average of f were then calculated for each age group.The errors between SSDEcalculation,cal-culated based on the median and mean,were compared with SSDEmeasure.Results:The CTDIVOL in the head was(9.46±1.35)mGy,and SSDEWD was(9.46±1.35)mGy;the difference was statistically signif-icant(t=58.87,P＜0.001);the CTDIVOL of chest was(2.64±0.86)mGy and SSDEWD was(5.13± 1.15)mGy,with a statistically significant difference(t=-220.99,P＜0.001);the CTDIVOL of abdo-men-pelvis was(3.02±1.46)mGy and SSDEWD was(5.79±2.03)mGy,the difference was also statisti-cally significant(t=-116.62,P＜0.001).The CTDIVOL was larger than SSDEWD in the head except for the 0～＜1-year subgroup and CTDIVOL was smaller than SSDEWD within each subset in the chest and abdomen pelvis.There were strong correlations between f and age(Head:r=0.83;Chest:r=0.90;Ab-domen-pelvis:r=0.86;P=0.000).According to statistics,the mean values of f at each examination site were 0.81～1.01 for the head,1.65～2.34 for the chest,and 1.71～2.35 for abdomen-pelvis;the median values of f at each examination site were 0.82～1.00 for the head,1.67～2.32 for chest and 1.71～2.34 for abdomen-pelvis.The SSDEDW could be accurately estimated using the mean f of each age.Conclu-sion:Applying the f average of each age can more accurately and quickly calculate size-specific dose es-timates,which is helpful for accurate control of CT radiation dose in children.
维普
万方数据