数字X线摄影辐射剂量与图像质量相关性的实验研究

目的:前瞻性研究不同X线辐射剂量与图像质量的相关性,以探索数字X线摄影(Digital radiography,DR)最适宜曝光量.方法:在仿真胸部体模中放置模拟网状、线状和结节病变结构.用125 kVp不同mAs,对体模及分辨率测试卡进行DR成像.4位放射陕师分别对所有图像进行阅片评分,同时测量入射体表剂量(Entrance surface dose,ESD)、均方根(Root mean squar,RMS)和空间分辨率.结果:ESD随着mAs的增加会增加,而RMS随着mAs的增加会降低;ESD增加至一定量时,空间分辨率达到极限值.曝光指数(Exposure index,EI)值1800以下的图像模拟微小结节显示不清,EI值2000以上的图像对模拟病变的检出高.结论:在保证DR图像质量的前提下,最优化的曝光剂量可以有效地减少辐射损伤.

The experimental study of correlation between the radiation dose and image quality in digital radiography

Objective: To prospectively research the correlation between the radiation dose and image quality in order to explore the optimization of exposure dose for digital radiography (DR). Methods:Simulated reticular, linear,and nodular structures were located in an anthropomorphic chest phantom.The phantom and resolution wedge were exposed by DR system with the same kilovoltage values (125 kVp) and different mAs sets.Four radiologists assessed all of the images.In addition,the entrance surface dose (ESD),root mean squar (RMS) and resolution were measured. Results:ESD was increasing along with mAs's enhancement,but RMS was decreasing when mAs was increasing. As long as the ESD increased to a certain degree, spatial resolution would go up to the limit. Images obtained with lower dose (EI＜1800)were obscure at the tiny nodular structure.Images of 2 000 El value could show clearly the Simulated lesion. Conclusion: The optimization of exposure dose for DR imaging may effectively decrease radiation injuries under the precondition of DR image quality to be guaranteed.