The outer materials and the edge of FTO produce the main scatter of the object.In order to reduce the scatter of the edge of FTO and BPC, a graded collimator is used in the radiographic system.

• 利用坡度准直器对系统散射严重的区域进行的降散射，表明坡度准直器是一个很好的降散射器件，能有效提高图像质量。