All patients were examined with a SOMATOM Sensation 16-slice CT scanner (Siemens) using the following parameters:120 kV,100 mAs,0.75 mm collimation,1 mm reconstruction slice thickness and increment,a pitch factor of 1,and a FOV of 100?mm.

• 扫描参数为:120kV；100mAs；0.；75mm准直器宽度；螺距为1；重建层厚1mm；高分辨骨算法重建。