目的 探讨肝脏CT低剂量扫描参 数与其图像质量的相关性。方法 使用不 同管电流和不同螺距对同一动物的肝脏行 CT扫描，毫安分别选择20-300mA的不同数 值，螺距选用0.516和1.375两种，分析 管电流和螺距与图像质量和辐射剂量的关 系。结果 由20mA至300mA，容积CT剂量指 数(volume CT dose index,CTDIvol)和剂 量长度乘积(dose length product,DLP) 呈线性比例增加，20mA-140mA是300mA 所得CTDIvol/DLP值的6.67%-46.7%；在 管电流不同mA值的情况下，螺距0.516:1 得到的CTDIvol、DLP有统计学差异(P ＜0.05)，螺距1.375:1得到的 CTDIvol、 DLP有统计学差异(P＜0.05)。结论 CTDIvol与电流大小呈线性正相关，通过 电流的变化来控制CTDIvol的大小，在图 像质量满足诊断要求的前提下，控制电流 在250-300mA，螺距为1.375：1，可使辐 射剂量最低。

Objective To explore the correlation between the CT scanning parameters of liver spiral CT and its image quality. Methods To use different tube current from 20 mA to 300 mA and pitch of 0.516 and 1.375 on the same animal liver by helical CT scanning, and to analyze the correlation among tube current, pitch, image quality and radiation dose. Results From 20 mA to 300 mA, CTDIvol and DLP hah linear proportional increase, the CTDIvol/DLP value of 20mA-140 mA was 6.67% to 46.7% of that of 300 mA. Comparing the different condition of tube current, the difference of CTDIvol, DLP was statistically significant when pitch was 0.516:1 and 1.375:1 (P<0.05). Conclusion CTDIvol had a positive linear correlation with the change of tube current. The image quality can be ensured and the radiation can be reduced by control the tube current between 250 to 300mA and the pitch of 1.375:1.