数字X线成像系统图像质量影响因素的实验研究

目的 比较非晶体硒平板探测器DR系统和CR系统的图像噪声、空间分辨率和入射体表剂量（ESD），研究数字X线图像质量影响因素的相关性。方法 采用相同管电压（125kVp）和不同mAs对仿真胸部体模用分辨率测试卡进行DR和CR曝光成像，测量ESD、空间分辨率，计算均方根（RMS）值，分析mA8、ESD、RMS及空间分辨率之间的变化关系。结果 两种系统的RMS随mAs的增加而降低，ESD随mAs的增加而增加。两种系统成像相同ESD时，DR的RMS略高于CR。ESD增加至一定量时，空间分辨率达到极限值（CR为3．1lp／mm，DR为3．4lp／mm）。结论 数字系统放射线剂量的改变会导致噪声、分辨率变化。适度的噪声水平对空间分辨率影响不明显。

Experimental study on the influence factors of image quality in digital X-ray imaging system

Objective To compare the data of image noise, spatial resolution and entrance surface dose（ESD） in chest imaging using an amorphous selenium flat-panel detector digital radiogrphy（DR）system with those data of a computed radiography（CR） system. To reasearch the correlation of influence factors of digital X - ray image quality. Methods An anthropomorphic chest phantom and resolution wedge were exposed by DR and CR system with the same kilovoltage values（125 kVp） and different mAs sets. ESD, spatial resolution was measured and root mean square（RMS） was calculated. The correlative changes caused by mAs, ESD, RMS and spatial resolution were analysed. Result For each digital system, RMS was decreasing when mAs was increasing, but ESD was increasing along with mAs＂ s enhancement. When the ESDs for DR and DR were equal, RMSs of the DR was just a little higher than those of the CR. As long as the ESD increases to a certain degree, spatial resolution will go up to the limit（CR was 3.1 lp/mm, DR was 3.4 lp/mm）. Conclusion Change of radiation dose will lead to change of the noise and resolution. Optimum noise level would not influence the spatial resolution of digital image markedly.