CT图像质量和辐射剂量的影响因素研究

目的对自动曝光技术性能进行定量评价。方法①在自动曝光方式下，检测肩部体模偏离扫描野中心时，噪声和有效mAs的变化。②在自动曝光和手动固定曝光方式下，对圆锥体模用头部和腹部方案分别进行螺旋扫描，比较2种曝光方式噪声和有效mAs随体模直径的变化。结果体模偏离扫描野中心25mm及以上时，图像的噪声在统计学上有显著差异．辐射剂量降低幅度依赖体模直径，体模位置明显影响图像质量和辐射剂量。结论在自动曝光方式下，体模位置明显影响图像质量和辐射剂量，辐射剂量降低幅度与体模的结构和大小有关。

Study on the factors influencing the image quality and radiation dosage of CT

Objective To quantitatively evaluate the image quality and radiation dosage antomatic exposure technique. Methods （1）The variations of noise and effective mAs with the departing of body module from the scanning field centre were examined in automatic exposure mode; （2）The noise and effective mAs in automatic mode and manual mode were compared by spiral scanning on head and abdomen. Results Noise was remarkably influenced when the body module was placed 25 mm away from the scanning field center. The amount of reduced radiation dosage depended on the diameter of body module and the position of body module affected the image quality and radiation dosage. Conclusion In the automatic exposure mode, the image quality and radiation dosage are remarkably affected by the positioning of body module. The decrease degree of radiation dosage is relating to the structure and size of body module.