肺部低剂量螺旋CT扫描的放射剂量评估

Low-dose helical CT in screening lung cancer: evaluation of radiation dosage

目的 :评价肺部低剂量与常规剂量螺旋CT扫描的X线放射剂量比 ,为低剂量螺旋CT普查早期肺癌提供扫描参数。方法 :将 80例的健康者自愿随机等分成 2组 ,40例行肺部低剂量螺旋CT扫描 ;40例行常规剂量螺旋CT扫描 ;扫描范围从肺尖至肺底。从CT扫描序列设定栏上 ,分别记录 2种扫描方式的权重CT剂量指数 (CTDIw )、扫描长度、总扫描时间 ;最后计算出 2种扫描方法的平均剂量长度乘积 (DLP)、毫安秒及X线放射剂量。结果 :肺部低剂量扫描的权重剂量指数为 2 .9mGY ,是常规剂量扫描 ( 11.7mGY)的 2 5 % ;低剂量扫描的剂量长度乘积 (DLP)为 63 .4mGY·cm明显低于常规剂量扫描 2 48mGY·cm(P <0 .0 0 1) ;低剂量扫描的毫安秒为 915mAs ,明显低于常规剂量扫描 3 5 2 1mAs(P <0 .0 0 1) ;低剂量扫描的放射剂量为 70 .8mGY ,是常规剂量扫描 ( 2 74.7mGY)的 2 6%。讨论 :肺低剂量螺旋CT扫描的放射剂量是常规剂量扫描的 2 6% ,适用于肺癌高危人群的早期普查。

Objective:Objective:To evaluate the application of low dose helical CT of chest compared with conventional helical CT,and to optimize its scanning technique.Methods:80 healthy volunteers were randomized to undergo either the low dose helical CT (50mA) (n=40) or conventional helical CT (200mA) (n=40) at the following parameters of 120kVP,0.75s,10mm collimation and pitch 1.The weighted CT dose index (CTDIw),dose length product (DLP),milliampere seconds (mAs) and radiation dose from the two scanning methods were calculated.Results:CTDIw was 2.9mGY for low dose helical CT,and 11.7mGY for conventional helical CT,the ratio was 1:4.DLP (63.4mGY·cm) of low dose CT was lower than that of conventional CT (248mGY·cm) ( P <0.001)The mAs (915mAs) of low dose CT was smaller than that of conventional CT (3521mAs) (P<0.001).Mean radiation dose to chest was 70.8mGY for low dose CT,and 274.7mGY for conventional CT.The former was 26% of the latter.Conclusion:The radiation dose to chest produced by low dose helical CT is 26% of that of conventional helical CT.Low dose CT can be recommended to the screening for lung cancer in high risk population.