宽排CT探测器CT剂量指数应用初探

Discussion on CT dose index for wide beam CT scanner

目的:随着射线宽度的不断增加,传统CT剂量指数(CTDI)在表征CT剂量时遇到瓶颈问题,不能够很好地表征宽排CT探测器的剂量水平。本文探讨CTDI在CT宽排探测器剂量表征量方面的概念演化和应用方式。方法:介绍传统CTDI表征CT剂量的原理和方式,展示传统CTDI在表征宽排CT探测器时的局限性,阐述宽排CT探测器CTDI剂量表征量方式的演变过程,初步探讨宽排CT探测器CTDI表征和测量。结果:IEC在对传统CTDI进行修正的基础上推出分层次CTDI表征的方式,能更好适应宽排CT探测器的剂量表征。通过多点分次测量,新定义的分层次CTDI仍然可采用传统的150mm有机玻璃CT剂量体模和100mm电离室进行测量。结论:分层次CTDI表征方式能在保留传统CTDI基本概念和常规测试条件的基础上较好地表征宽排CT探测器的剂量水平。

Objective： With the increasing of beam width of CT scanner, traditional CT dose index（CTDI） encountered difficulties when expressing dosimetry for wide beam CT scanner. This article discussed the evolution and application of CTDI for wide beam CT scanners. Method： This article demonstrated principles of traditional CTDI and the limitation of it as a dosimetry for wide beam CT scanners, and introduced the evolution of CTDI for wide beam CT scanners and their principles and measurements. Results： IEC amended traditional CTDI and recommended a tiered approach to the definition of CTDI to be more adaptive for wide beam CT scanners. And with the approach of several time measurements at different locations, 150ram long PMMA phantom and 100mm long ion chamber could still be used for the measurements of new tiered CTDI. Conclusion： New tiered CTDI provided a more accurate dosimetry for wide beam CT scanners with a reservation of basic concept and measurement conditions of traditional CTDI.