Brink J A
Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, USA.
Radiol Clin North Am. 1995 Sep;33(5):825-41.
Care must be taken to optimally select settings for collimation, table feed, and reconstruction interval for successful helical CT and associated special application such as CT angiography. Thus, prospective planning is critical for optimal 3-D imaging. Generally, one wishes to minimize all of these parameters to maximize longitudinal resolution; however, one must be aware of the tradeoffs associated with these choices. Pixel noise increases with decreasing collimation. Limiting the table feed to a value equal to the collimation (pitch of 1:1) limits broadening of the effective slice thickness associated with the table motion but also limits the scan coverage. Generally, one may accept a table feed up to twice the collimation (pitch of 2:1) on modern equipment with current software. Reconstruction intervals should also be selected to satisfy the clinical need. When multiplanar and 3-D imaging is desired, the reconstruction interval should be selected such that at least two slices are generated per table increment.
为成功进行螺旋CT及相关特殊应用（如CT血管造影），必须谨慎为准直、床速和重建间隔选择最佳设置。因此，前瞻性规划对于获得最佳三维成像至关重要。一般来说，人们希望将所有这些参数降至最低以最大化纵向分辨率；然而，必须意识到这些选择所带来的权衡。像素噪声会随着准直的降低而增加。将床速限制为等于准直的值（螺距为1:1）可限制与床移动相关的有效层厚增宽，但也会限制扫描范围。一般而言，在配备当前软件的现代设备上，人们可以接受高达两倍准直（螺距为2:1）的床速。重建间隔也应根据临床需求进行选择。当需要多平面和三维成像时，重建间隔应选择为每床进床增量至少生成两层图像。
