迭代算法(ASIR-V)在儿童腹部低剂量扫描中的应用研究

Effect of adaptive statistical iterative reconstruction-V technique on radiation dose reduction and image quality of pediatric abdominal CT

目的探讨迭代算法(ASIR-V)在儿童腹部低剂量扫描中的应用价值。方法 60例患儿随机分为三组,每组20例,扫描条件:管电压100 kV,自动毫安(10~450 mA),扫描时间0.5 s,螺距0.992,层厚2.5 mm,噪声指数:9。A组:ASIR-V:30%;B组:ASIR-V:50%;C组:ASIR-V:70%。每例分别测量肝门层面,右肾下极层面,耻骨联合层面背部肌肉SD的平均值为背景噪声指数,记录每个病例的剂量长度乘积,并根据公式换算有效剂量,分别对两组SD、ED分别进行独立样本t检验,P<0.05为差异有统计学意义,由两位工作10年以上医师进行独立阅片,对图像进行主观评分。结果三组病例SD分别10.28±1.03、11.34±0.82、9.34±1.67;DLP(m Gy·cm)分别为73.69±17.55、55.73±10.62、37.65±10.01;ED(m Sv)分别为2.57±0.43、1.78±0.76、1.28±0.75。三组SD值相当,任意两组差异无统计学意义(P>0.05)。随着ASIR-V级别的提高,ED降低,任意两组差异有统计学意义(P<0.05)。读片结果各病例图像质量良好(≥3分),两位医师图片一致性良好。结论随着ASIR-V水平的提高,图像噪声保持稳定,低辐射剂量有效降低,在儿童腹部CT扫描中有重要价值。

Objective To evaluate the effects of adaptive statistical iterative reconstruction V technique （ASIR-V） on radiation dose reduction and image quality in pediatric abdominal CT.Methods 60 children were randomized into three groups of 20.All children underwent abdominal CT with 2.5-mm slice thickness,9-HU noise index level of automatic current modulation,10-450 mA,and 100 kV on a 256-row CT scanner.The rotation time was 0.5 s and detector width was 120-160 mm.The presetting ASIR-V percentage was 30%,50% and 70% in Group A,Group B and Group C,respectively.The background noise index was measured as average standard deviations （SDs） on the posterior muscles at the level ofporta hepatis,right lower renal pole,and pubic symphysis.The dose-length product （DLP） was recorded and effective dose （ED） was computed.Statistical analyses were performed using independent sample t test and ANOVA.Results There was no significant difference （P〉0.05） in the SDs among the A （10.28±1.03 HU）,B （11.34±0.82 HU）,and C （9.34±1.67 HU） groups with DLPs of 3.69±17.55 mGy·cm,55.73±10.62 mGy ·cm,and 37.65±10.01 mGy ·cm,respectively.The ED decreased significantly （P〈0.01） with increasing ASIR-V percentage at 2.57±0.43 mSv,1.78±0.76 mSv,and 1.28±0.75 mSv,respectively.Conclusion The ASIR-V technique can effectively reduce the radiation dose without increasing image noise and is valuable in low-dose pediatric abdominal examination.