Ernst O, Gaillandre L, Mizrahi D, Sergent G, Bonvarlet P, L'Herminé C
Radiologie Est, CHU Lille.
J Radiol. 1995 Dec;76(12):1069-74.
In helical CT, there are 4 mains factors of quality: The in-plane spatial resolution that is the same in conventional CT; The spatial resolution on the Z axis, which is the slice thickness. The increase factor of the slice thickness between a conventional and a helical CT depends on the pitch and the reconstruction algorithm. The value of the increase factor can be easily calculated; The signal to noise ratio which depends on the collimation, the mA, the KV and the reconstruction algorithm. The signal to noise ratio is not depending on the table speed; The reconstruction interval which can be less than the slice thickness. Then the contrast of small lesion is improved and stair-step artifacts are reduced in 3D reformations.
在螺旋CT中，有4个主要的质量因素：平面内空间分辨率，与传统CT相同；Z轴上的空间分辨率，即层厚。传统CT与螺旋CT之间层厚的增加因子取决于螺距和重建算法。增加因子的值可以很容易地计算出来；信噪比，它取决于准直、毫安、千伏和重建算法。信噪比不取决于床速；重建间隔可以小于层厚。这样，在三维重建中，小病变的对比度得到改善，阶梯状伪影减少。
