摘要:
Objective To study the methods to estimate absorbed dose to eye lens of infants from CT scanning using different protocols and try to find a practical quick way for estimating absorbed dose to eye lens.Methods By scanning one-year old anthropomorphic phantom using 7 kinds of different protocols,all TLDs were measured for final estimation of absorbed dose to eye lens using two different dose conversion methods.Meanwhile,linear regression equation was established between absorbed dose to eye lens and CTDI.Results Absorbed doses to eye lens of infants from children CT scanning using 7 kinds of different protocols were (9.96±0.69) mGy in head axis,(7.01±0.42) mGy in head helical,(12.60± 0.97) mGy in sinus,(12.97±0.42) mGy in inner ear,(0.63±0.03) mGy in neck soft tissue,(8.89± 0.44) mGy in cervical vertebra,and (0.34± 0.01) mGy in chest,respectively.There were statistically significant difference in doses among different groups (F =846.826,P < 0.05).For different scanning locations,there was linear relation between absorbed dose to eye lens and CTDI(r=0.986-0.999,P< 0.05).Conclusions Absorbed dose to eye lens of infants from children CT scaning with single dose may not be above threshold dose.In addition,absorbed dose to eye lens can be estimated quickly by linear regression equation between absorbed dose to eye lens and CTDI.%目的 探讨CT不同扫描方案检查所致婴幼儿眼晶状体吸收剂量估算方法,并寻求快速估算眼晶状体吸收剂量的实用方法.方法 通过设置7种临床标准扫描方案,对1岁年龄组仿真模体进行扫描,利用布放在模体不同位置的热释光探测器(TLD)测量剂量,最后测量结果分别用组织因子转换和个人剂量当量转换两种方法来估算眼晶状体吸收剂量,同时将眼晶状体吸收剂量与CT剂量指数(CTDI)建立线性回归方程.结果 7种临床标准儿童扫描方案CT检查所致的婴幼儿眼晶状体吸收剂量分别为(9.96±0.69) mGy(头部轴向)、(7.01±0.42) mGy(头部螺旋)、(12.60±0.97) mGy(副鼻窦)、(12.97±0.42) mGy(内耳高分辨)、(0.63±0.03) mGy(颈部软组织)、(8.89±0.44) mGy(颈部颈椎)和(0.34±0.01)mGy(胸部常规),不同组之间剂量差异有统计学意义(F=846.826,P<0.05).不同扫描部位,CTDI值与眼晶状体吸收剂量之间均存在线性关系(r=0.986~0.999,P<0.05).结论 采用儿童CT扫描条件,婴幼儿眼晶状体吸收剂量单次剂量范围一般不会超过阈剂量.另外,通过读取CTDI值,利用线性关系,可快速估算眼晶状体吸收剂量.