Bontus Claas, Köhler Thomas, Proksa Roland
Philips Research Laboratories, Sector Technical Systems, Röntgenstrasse 24-26, D-22 335 Hamburg, Germany.
Med Phys. 2003 Sep;30(9):2493-502. doi: 10.1118/1.1601913.
Recently, an exact reconstruction method for helical CT was published by A. Katsevich. The algorithm is of the filtered backprojection type and is, therefore, computationally efficient. Moreover, during backprojection, only data are used which correspond to an illumination interval of 180 degrees as seen from the object-point. We propose a new reconstruction method, which is applicable to data obtained with a 3-Pi acquisition [IEEE Trans. Med. Imaging 19, 848-863 (2000)]. The method uses the same filter types as the Katsevich algorithm, but the directions and the number of the filter lines are chosen differently. For the derivation of the new algorithm, we analyze the relationship of the Katsevich method and radon inversion. A certain radon plane can intersect with the backprojection interval related to a 3-Pi acquisition either once, three, or five times. In analogy to the definition of quasiexactness introduced by Kudo et al. for a 1-Pi acquisition, we use the term quasiexactness for algorithms on a 3-Pi acquisition, if radon planes with one or three intersections within the backprojection interval are treated correctly. Using the results on the relationship with radon inversion, we can prove that our algorithm is quasiexact in this sense. We use simulation results in order to demonstrate that the algorithm yields excellent image quality.
最近，A. Katsevich发表了一种用于螺旋CT的精确重建方法。该算法属于滤波反投影类型，因此计算效率高。此外，在反投影过程中，仅使用从物点看对应180度照明间隔的数据。我们提出了一种新的重建方法，它适用于通过3 - Pi采集获得的数据[《IEEE医学成像汇刊》19, 848 - 863 (2000)]。该方法使用与Katsevich算法相同的滤波器类型，但滤波器线的方向和数量选择不同。为了推导新算法，我们分析了Katsevich方法与拉东反演的关系。某个拉东平面与3 - Pi采集相关的反投影间隔可能相交一次、三次或五次。类似于Kudo等人针对1 - Pi采集引入的准精确性定义，如果在反投影间隔内具有一次或三次相交的拉东平面得到正确处理，我们将3 - Pi采集算法的术语称为准精确性。利用与拉东反演关系的结果，我们可以证明我们的算法在这个意义上是准精确的。我们使用模拟结果来证明该算法能产生出色的图像质量。
