Longitudinal sampling and aliasing in spiral CT.
Longitudinal sampling and aliasing in spiral CT.
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螺旋 CT 中的纵向采样和混叠。
DOI：
10.1109/42.750254
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Napel,S
中科院分区：
文献类型：
--
作者：
Yen,SY;Yan,CH;Rubin,GD;Napel,S
虽然已经对传统的计算机断层扫描（CT）图像进行了平面内混叠的分析，但螺旋CT中的纵向混叠还没有得到适当的研究。提出了螺旋CT三维采样方案的数学模型，并分析了其对纵向混叠的影响。他们使用CT模拟和实际体模扫描研究了纵向混叠作为螺旋插值算法、螺距和重建间隔的函数。作者的模型预测并验证了，对于等中心处的径向均匀对象，螺旋采样方案导致混叠光谱岛的空间变化抵消，这反过来又导致空间变化的纵向混叠。在扫描仪等中心处，混叠最小，但随着距离的增加，混叠迅速变得明显。作者的结果与已发表的在扫描仪等中心点处观察到的结果一致，并进一步提供了关于螺距、插值算法和重建间隔的偏离等中心点位置处的混叠条件的新见解。作者得出结论，在偏离等中心点位置的纵向混叠可能是显著的，并且其幅度和影响不能仅通过在扫描仪等中心点处进行的测量来预测。
Although analyses of in-plane aliasing have been done for conventional computed tomography (CT) images, longitudinal aliasing in spiral CT has not been properly in investigated. The authors propose a mathematical model of the three-dimensional (3-D) sampling scheme in spiral CT and analyze its effects on longitudinal aliasing. They investigated longitudinal aliasing as a function of the helical-interpolation algorithm, pitch, and reconstruction interval using CT simulations and actual phantom scans. The authors' model predicts, and they verified, that for a radially uniform object at the isocenter, the spiral sampling scheme results in spatially varying cancellation of the aliased spectral islands which, in turn, results in spatially varying longitudinal aliasing. The aliasing is minimal at the scanner isocenter, but worsens with distance from it and rapidly becomes significant. The authors' results agree with published results observed at the isocenter of the scanner and further provide new insight into the aliasing conditions at off-isocenter locations with respect to the pitch, interpolation algorithm, and reconstruction interval. The authors conclude that longitudinal aliasing at off-isocenter locations can be significant, and that its magnitude and effects cannot be predicted by measurements made only at the scanner isocenter.