Rockstroh G
Robert-Rössle-Klinik, Universitätsklinikum Charité der Humboldt-Universität zu Berlin.
Aktuelle Radiol. 1998 Nov;8(6):250-2.
The longitudinal resolution of spiral CT has been investigated in dependence on table increment and beam collimation by use of a phantom. The results show clearly that the pitch (ratio of table increment per tube rotation to beam collimation) alone does not allow one to draw any conclusions about the resolution. Thus, a large pitch can yield a better resolution than the pitch of 1. The individual parameters table increment and beam collimation are more relevant with regard to the resolution than the rate of pitch. An alteration of the pitch can be achieved in two different ways. An increase of the pitch by a decreased beam collimation improves the resolution. In contrast, an increase of the pitch by an increased table increment decreases the resolution. A good spatial resolution of objects with high contrast (bone, lung, enhanced vessels) needs a narrow beam collimation, even if a pitch as high as 2 is necessary for a given scanning coverage. A large pitch does not cause gaps in the data set. Moreover, the patient's radiation dose decreases.
通过使用体模，研究了螺旋CT的纵向分辨率与床速和准直宽度的关系。结果清楚地表明，仅螺距（每管旋转的床速与准直宽度之比）并不能让人对分辨率得出任何结论。因此，大螺距可能比螺距为1时具有更好的分辨率。就分辨率而言，床速和准直宽度这两个参数比螺距率更重要。改变螺距可以通过两种不同的方式实现。通过减小准直宽度来增加螺距可提高分辨率。相反，通过增加床速来增加螺距会降低分辨率。对于高对比度的物体（骨骼、肺部、强化血管），即使对于给定的扫描范围需要高达2的螺距，良好的空间分辨率也需要窄准直宽度。大螺距不会导致数据集出现间隙。此外，患者的辐射剂量会降低。
