常规辐射剂量评估参数与体型特异性剂量评估在估算儿童心脏CT扫描辐射剂量的差异

Comparison of Traditional Radiation Dose Assessment Parameters and SSDE in Evaluating the Radiation Dose of CT Scan on Children with Congenital Heart Diseases

目的比较常规辐射剂量评估参数与体型特异性剂量评估(SSDE)在估算先天性心脏病(CHD)患儿CT扫描时所受辐射剂量的差异。方法将161例CHD患儿按年龄分为A组(<4个月)、B组(4个月~1岁)、C组(1~6岁)、D组(>6岁),采用Philips 128螺旋CT扫描仪对CHD患儿进行心脏CT增强扫描,在气管隆突层面测量每例患儿的左右径(LAT)、前后径(AP),测算患儿有效直径(ED),同时记录每例患儿的容积CT剂量指数(CTDIvol)值、剂量长度乘积(DLP)值、有效辐射剂量(ED*)值,计算SSDE。分析CTDIvol、DLP、ED*及SSDE之间的差异性。结果 A组CTDIvol和SSDE分别为(2.705±0.110)m Gy和(6.688±0.352)m Gy(t=-65.780,P<0.001),B组CTDIvol和SSDE分别为(2.699±0.166)m Gy和(6.394±0.429)m Gy(t=-66.191,P<0.001),C组CTDIvol和SSDE分别为(2.516±0.232)m Gy和(5.727±0.640)m Gy(t=-32.653,P<0.001),D组CTDIvol和SSDE分别为(2.580±0.147)m Gy和(5.098±0.289)m Gy(t=-15.540,P<0.001),SSDE值均大于CTDIvol值,且随着年龄增长差值越大,SSDE之间差值较CTDIvol之间差值更大。另采用Pearson相关分析对体重及CTDIvol、DLP、ED*、SSDE进行相关性分析,结果显示体重与CTDIvol之间无相关性(r=-0.138,P>0.05),而与DLP、ED*、SSDE存在相关性(r分别为0.232、0.232、-0.422,P<0.01)。结论 CTDIvol明显低估了患儿所受的辐射剂量,SSDE能够更准确地反映不同体型患儿进行心脏CT扫描时实际接受的辐射剂量。

Objective To compare the difference between traditional radiation dose assessment parameters and sizespecific dose estimates（ SSDE） in evaluating the radiation dose of CT scan on children with congenital heart diseases（ CHD）. Methods 161 children with CHD were divided into four groups： group A（ 4 months）,group B（ 4 months-1 years）,group C（ 1-6 years old） and group D（ 6 years）. Heart enhanced CT scan were performed on these children with CHD by a Philips 128-slices spiral CT scanner. The anterior-posterior dimension（ AP） and lateral dimension（ LAT） of each patient were measured at the level of carina. The effective diameters（ ED） were calculated by AP,LAT. SSDE were calculated by the recorded volumetric CT dose index（ CTDIvol）,dose-length product（ DLP） and the effective radiation dose（ ED＊）. We then studied the correlation between CTDIvol,DLP,ED＊and SSDE. Results CTDIvol and SSDE in Group A were（ 2. 705 ± 0. 110） m Gy and（ 6. 688 ± 0. 352） m Gy（ t =-65. 780,P〈0. 001）. CTDIvol and SSDE in Group B were（ 2. 699 ± 0. 166） m Gy and（ 6. 394 ± 0. 429） m Gy（ t =-66. 191,P〈0. 001）. CTDIvol and SSDE in Group C were（ 2. 516± 0. 232） m Gy and（ 5. 727 ± 0. 640） m Gy（ t =-32. 653,P〈0. 001）. CTDIvol and SSDE in Group D were（ 2. 580 ±0. 147） m Gy and（ 5. 098 ± 0. 289） m Gy（ t =-15. 540,P〈0. 001）. The data of SSDE is higher than CTDIvol and the gap is positively related to age. There is no correlation between weight and CTDIvol（ r =-0. 138,P〈0. 05）. But weight is related to DLP,ED and SSDE（ r = 0. 232,0. 232,-0. 422,P〈0. 01）. Conclusion The radiation dose of children is significantly underestimated by using CTDIvol. SSDE can reflect the real radiation dose in different figures of children in cardiac CT scan.