不同对比剂下CT值和辐射剂量相关性的实验研究

Experimental study on correlation between CT value and radiation dosage with different contrast agents

目的:探讨在不同扫描参数下,血管内不同浓度对比剂的CT值、辐射剂量和图像质量的关系。方法:分别取1、2、3、4、5和6 ml的碘佛醇对比剂,分别与99、98、97、96、95和94 ml的生理盐水进行均匀混合。使用10 ml注射器在各组内抽取10 ml的溶液,采用西门子Definition AS 64层螺旋CT机对不同浓度的对比剂进行采集图像,曝光量分为400、300、200 m As 3组,对比不同模体内在不同曝光量下的CT值、辐射剂量和图像质量。结果:容积CT剂量指数(CT dose index volumes,CTDI_(vol))和剂量长度乘积(dose length product,DLP)在400 m As时分别为64.52 m Gy和273.4 m Gy·cm;300 m As时分别为48.44 m Gy和204.6 m Gy·cm;200 m As时分别为32.26 m Gy和136.3 m Gy·cm。6组不同模体在相同曝光量下所得到的CTDI_(vol)和DLP相同。6组模体随着模体浓度的升高,图像质量分值呈线性增加。结论:当靶血管内对比剂浓度较高时,使用低曝光量进行采集图像,会在不降低图像质量的基础上,降低辐射剂量。

Objective To explore the correlations between the CT value,radiation dosage and imaging quality with different scanning parameters and contrast agents.Methods There were 1,2,3,4,5 and 6 ml ioversol contrast agents mixed evenly with 99,98,97,96,95 and 94 ml normal saline,and 10 ml solution was extracted from each kind of mixed liquor with a10-ml syringe.Siemens Definition AS 64-slice CT was used to acquire images for concentrations of contrast agents with the parameters of 400,300 and 200 mAs.The CT values,radiation dosage and image quality were compared for different phantoms and mAs.Results CTDI_（vol） and DLP were 64.52 mGy and 273.4 mGy·cm respectively in case of 400 mAs,48.44 mGy and204.6 mGy·cm in case of 300 mAs,and 32.26 mGy and 136.3 mGy·cm in case of 200 mAs.Six phantoms gained the same values of CTDI_（vol） and DLP in case of the same mAs,and the image quality correlated linearly with the concentration of the phantom.Conclusion In case of high-concentration contrast agent in the targeted vessel,images can be acquired with low mAs to decrease radiation dosage without debasing image quality.