降低新生儿64层螺旋CT颅脑扫描辐射的研究

Study on the decrease in scanning radiation of 64 row of spiral CT to the neonatal brain

目的研究64层螺旋CT在新生儿颅脑扫描中可用的最低扫描参数,以达到降低辐射剂量,减少辐射损害的目的。方法用螺旋和切片2种不同扫描方式,采用逐渐降低扫描参数方法,得出新生儿颅脑64层螺旋CT扫描可用的最佳方法和最低扫描参数。固定KVP值120 kV和其他扫描参数,每次降低10 mAs;切片法低剂量组扫描参数从120 kV和60 mAs开始,螺旋法低剂量组扫描参数从120 kV和90 mAs开始。每组扫描20例患儿,每组扫描所得图像由3位高级职称影像诊断专家按图像清晰度、图像层次对比度,脑组织、脑室、脑沟具体解剖结构及病变显示能力标准,将图像质量分为优质、良好、一般、较差、差5个等级,分别被评为5、4、3、2、1分,3分及以上的图像认为满足诊断要求。结果64层螺旋CT螺旋扫描120 kV和60 mAs是可用的最低扫描参数。螺旋扫描120 kV和60 mAs的CT辐射剂量指数(CTDI)7.7 mGy、平均剂量长度体积(DLP)155.1 mGy.cm;切片扫描120 kV和30 mAs是最低参数。切片扫描120 kV和30 mAs的CTDI 5.19 mGy、平均DLP 41.9 mGy.cm。2组最低扫描参数剂量分别是常规螺旋扫描的40%和11%,同时切片扫描是螺旋扫描剂量的27%。由此,切片扫描较螺旋扫描剂量明显减低,约73%。结论64层螺旋CT新生儿颅脑扫描的最佳方法是切片扫描,可用的最低扫描参数是120 kV和30 mAs。

Objective To study the lowest parameter of scanning radiation in 64 row of spiral CT used in the neonatal brain,aiming to decrease radiation.Methods Spiral scanning and section scanning were used by gradually decreasing scanning parameter to find the best method and the lowest parameter used in the neonatal brain.KVP was fixed at 120 kV,other scanning parameter were gradually decreased by 10 mAs.Low dose group of section scanning began from 120 kV,60 mAs,low dose group of spiral scanning began from120 kV,90 mAs.Twenty newborn were scanned at each group,images of each group were diagnosed by three image diagnosis expert with senior title,according to image definition,gradation and contrast,concrete anatomy structure in brain tissue,ventricle,sulcus as well as detectabilities of lesions,divided into five levels,named as high,good,general,poor,worse quality：scored 5,4,3,2,1 respectively.≥3 were thought as qualified.Result 120 kV and 60 mAs was the lowest scanning parameter accesable in 64 row of spiral CT.CTDI was 7.7 mGy,DLP was 155.1 mGy·cm in spiral scanning.120 kV and 30 mAs was the lowest scanning parameter accesable in section scanning.CTDI was 5.19 mGy,DLP was 41.9 mGy·cm in section scanning.The scanning parameter of two group was 40% and 11% to general scanning respectively.The parameter in section scanning was 27% to that of spiral scanning.Accordingly,the parameter in 64 row of spiral CT used in skull brain of newborn was clearly decreased by 73%.Conclusion The best method in 64 row CT used in the neonatal brain is section scanning.The lowest scanning parameter is 120 kV and 30 mAs.