NEW APPROACH TO INTERPOLATION IN COMPUTED TOMOGRAPHY
NEW APPROACH TO INTERPOLATION IN COMPUTED TOMOGRAPHY
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DOI：
10.1097/00004728-197811000-00010
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发表时间：
1978-01-01
影响因子：
1.3
通讯作者：
TALBERT, AJ
中科院分区：
文献类型：
--
作者：
BROOKS, RA;WEISS, GH;TALBERT, AJ
目前生产的大多数X射线扫描仪使用一种称为过滤反投影法的图像重建方法。数据采样有两个限制，这要求在反投影操作期间使用近似，从而导致重建图像中的错误。在这两种情况下，错误都与尖锐的边缘(如骨骼界面)相关。第一个限制是每个视图或投影包含有限数量的数据值n。这通常通过使用对过滤后的投影的分段线性或最近邻近似来处理。其结果是轻微的高频衰减，类似于平滑过滤器的衰减，还会产生频谱复制，从而产生云纹类型的伪像。这两种影响都可以通过使用更精细的采样间隔或通过高阶曲线近似来减少。第二个限制是存在有限数量的视图m。处理此问题的传统方法是用包含每个视图的1个值的离散和来替换.vphi-整数。这种方法在外围条纹的图案中，其强度取决于查看次数。提出了一种新的计算积分的方法，其中每个视图的贡献被计算为该视图的适当小片段上的平均值。当视点数目有限时(m<；n.pi/2)，新方法在不损失空间分辨率的情况下减少条纹伪影。为了M·西梅克。N.pi。4，新方法需要的计算时间大约是原来的两倍。
Most X-ray scanners presently in production use a method of image reconstruction called filtered back-projection. There are 2 limitations in data sampling which require that approximations be used during the back-projection operation, and hence result in error in the reconstructed image. In both cases the errors are associated with sharp edges such as bone interfaces. The first limitation is that each view, or projection, contains a finite number of data values, n. This is usually handled by using a piecewise-linear or nearest-neighbor approximation to the filtered projection. The result is a slight high frequency attenuation, similar to that of a smoothing filter, and also a spectrum replication, which produces a moire-type artifact. Both effects can be reduced by using a finer sampling interval or by high-order curvilinear approximations. The 2nd limitation is that there are a finite number of views, m. The conventional way of handling this problem is to replace the .vphi.-integral with a discrete sum containing 1 value from each view. This approach in a pattern of peripheral streaks whose intensity depends on the number of views. A new way to evaluate the integral is proposed in which the contribution from each view is computed as an average over an appropriate small segment of the view. When the number of views is limited (m < n .pi./2), the new method reduces the streak artifact with no loss in spatial resolution. For m .simeq. n .pi. 4, the new method requires approximately twice the computing time.