Brink J A, Heiken J P, Wang G, McEnery K W, Schlueter F J, Vannier M W
Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, MO 63110.
Radiographics. 1994 Jul;14(4):887-93. doi: 10.1148/radiographics.14.4.7938775.
The performance of helical CT requires several user-defined parameters that exceed the requirements of conventional CT. One needs to carefully select the collimation, table increment, and reconstruction interval. Minimizing these parameters maximizes longitudinal resolution but with various trade-offs. Decreasing the collimation decreases the effective section thickness but increases pixel noise. Limiting the table increment to a pitch of 1 limits the broadening of the effective section thickness associated with the helical technique but also limits the coverage that can be achieved with a given helical scan. Our general practice is to minimize the collimation to cover the volume of interest and to accept a pitch up to 2, provided that we are using 180 degree interpolation. The reconstruction interval is also minimized to maximize longitudinal resolution but with trade-offs of increased image processing time, data storage requirements, and physician time for image review. For routine diagnosis, we recommend reconstruction of one to two sections per table increment, and, for multiplanar and three-dimensional imaging, we recommend at least three sections be reconstructed per table increment. The scan duration is dictated by both patient and machine factors.
螺旋CT的性能需要几个用户定义的参数，这些参数超出了传统CT的要求。需要仔细选择准直、床速和重建间隔。将这些参数最小化可最大化纵向分辨率，但会有各种权衡。减小准直会减小有效层厚，但会增加像素噪声。将床速限制为螺距1可限制与螺旋技术相关的有效层厚的增宽，但也会限制给定螺旋扫描所能达到的覆盖范围。我们的一般做法是将准直最小化以覆盖感兴趣的体积，并接受高达2的螺距，前提是我们使用180度插值。重建间隔也最小化以最大化纵向分辨率，但会增加图像处理时间、数据存储需求以及医生查看图像的时间。对于常规诊断，我们建议每床速增量重建一到两层，对于多平面和三维成像，我们建议每床速增量至少重建三层。扫描持续时间由患者和机器因素决定。
