小儿头部多层螺旋CT检查的放射剂量评价

目的　评价小儿头部低剂量与常规剂量多层螺旋CT检查的放射剂量 ,为小儿头部多层螺旋CT检查提供扫描剂量参数。资料与方法　 (1)按年龄把 12 0例 0～ 6岁小儿分成 2组 ,患儿 <6个月 ,12 0kVp、90mAs扫描 30例 ;6个月～ 6岁 ,12 0kVp ,15 0mAs扫描 30例 ;常规扫描剂量为 12 0kVp、2 6 0mAs,依照上述年龄段各扫描 30例。其余扫描参数为 :准直 1.5mm ,层厚 6mm ,重建间隔 6mm ,床速 11.7mm/r,扫描时间 0 .75s。分别比较 2种扫描剂量产生的有效mAs、CT权重剂量指数 (weightedCTdoseindex ,CTDIw)及剂量长度乘积 (dose lengthproduct,DLP) ,并作 χ2检验。 (2 )由 3名医师盲法评价CT图像。按正常图像、图像有少许伪影、图像有严重伪影的等级对每帧图像进行质量评判 ,并进行统计学处理。结果　 (1)小儿各年龄段低剂量 (90mAs、15 0mAs)扫描的CTDIw为 17.2 8mGy、2 8.8mGy ,分别是常规剂量 (2 6 0mAs)扫描的 34.6 %、5 7.8% ;前者的DLP分别为 2 37mGy·cm、4 2 3mGy·cm ,明显低于后者的 6 83mGy·cm、731mGy·cm(P <0 .0 1)。 (2 ) 98%以上小儿头部低剂量CT图像可满足临床影像诊断需要 ,与常规剂量小儿头部图像相比无显著差异 (P >0 .0 5 )。结论　小儿头部低剂量多层螺旋CT扫描的辐射剂量为常规剂量扫描的 35

Evaluation of Radiation dose in Multislice Spiral CT for Pediatric Head

Objective To compare the radiation exposure delivered by low dose with standarddose multislice spiral CT (MSCT) in examination of pediatric head, and provide optimal CT scan parameters for pediatric head.Materials and Methods (1)120 volunteers were randomly assigned to undergo low dose or standard dose MSCT, 120 kVp, 90 mAs (n=30) scan for those at age less than 6 months, 150 mAs (n=30) scans for those at age from 6 months to 6 years, and 260 mAs (n=60) scans for both groups. The other scanning parameters were 0.75s, 1.5mm collimation, and 11.7 mm feed/rotation. Weighted CT dose index (CTDIw), dose length product (DLP), Effective mAs (eff.mAs) and total mAs produced by the every scanning protocol were compared. (2)CT images were evaluated by three doctors using blind method, and 3 degrees including normal image, image with few artifact, and image with excessive artifact, were employed and analyzed statistically.Results (1)CTDIw was 17.28 mGy for 90 mAs (34.6%), 28.85 mGy for 150 mAs (57.8%). DLP (237 mGycm for 90 mAs, 423 mGycm for 150 mAs scanning) of low-dose CT was lower than that (683 mGycm, 731 mGycm) of standard dose CT (all P<0.01). (2)98% low dose image was fully readable, which was no significant difference (P>0.05) with standard dose image.Conclusion Standard dose CT can be replaced by low-dose MSCT for examining pediatric head, radiation dose in pediatric head produced by low-dose CT was 35% or 57% of that produced by standard dose MSCT.