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目的 研究宽束多排螺旋CT标称线束宽度与CT剂量指数(CTDI)测量效率的关系,为完善我国CT质量控制检测规范提供数据支持.方法 在一台128排螺旋CT上,分别使用100 mm笔形电离室和150 mm长PMMA体模组合,以及300 mm长杆电离室和450 mm长PMMA体模组合,测量从5～80 mm不同线束宽度下的CTDI100和CTDI300;用CTDI300近似代替CTDI∞,计算CTDI测量效率.利用IEC和IAEA出版物中建议的公式计算CTDI100,NT,比较计算值与CTDI300的差异.结果 不同线束宽度时模体中心位置的CTDI100的数值与CTDI300之间存在明显差异,随着线束宽度的增大CTDI测量效率随呈下降趋势,CTDI100与CTDI300的比值从线束宽度5 mm时的0.62,在线束宽度为80 mm时CTDI测量效率降至0.56.通过IEC和IAEA的修正公式,可以使CTDI100,NT与CTDI∞的比值保持在一个相对恒定的水平.结论 目前广泛使用的CT辐射剂量表征量对评价宽束多排螺旋CT剂量时缺乏准确性,通过修正公式能在一定程度上表征宽排CT探测器的剂量水平,关于如何准确表达宽束CT的剂量并采用简单的方法对其准确测量,国际社会仍然在进一步的研究中.“,”Objective To study the relationship between the nominal beam width and CTDI measurement efficiency of wide beam multi-slice spiral CT to provide data support for improving the specification for quality control testing of CT in China.Methods Dose measurements were performed on a 128 detector row CT scanner.The effect of beam widths on CTDI100 and CTDI300 was assessed for acquisitions from 5 mm to 80 mm.The CTDI100 is based on application of the readily available 150 mm long CT dose body phantoms and the 100 mm pencil ionization chamber.CTDI300 is supported by measurements with ex-tended 450 mm CT dose body phantom and a 300 mm long pencil CT ionization chamber.CTDI300 was used instead of CTDI∞ to calculate the CTDI measurement efficiency.An amended CTDI100.NT according to IEC and IAEA publications was calculated and compared with CTDI300.Results The CTDI100 measurement efficiency decreased with the increase of beam widths.The ratio of CTDI100 to CTDI300 was 0.62 from 5 am,at a beam width of 80 am,the measurement efficiency dropped to 0.56.Through the IEC and IAEA correction formula,the ratio of amended CTDI100,NT to CTDI∞ can be maintained at a relatively constant level.Conclusion The widely used CT dose index CTDI100 is lack of accuracy in evaluating the CT dose of widebeam multi-slice spiral CT.The correction formula can characterize the dose level of wide beam multi-slice spiral CT to a constant ratio.On how to accurately express and measure the dose of wide beam CT by a simple way,the international community is still on the road.