摘要:
在传统的CT系统中,系统的硬件成本和计算量都是非常巨大的。本文深入分析了一种利用偏移放置的面阵探测器的锥束CT系统,在这种系统中X射线束仅仅覆盖被扫描物体的一半体积,投影数据在探测器方向上是截断的,探测器尺寸和投影数据量都减少为传统CT系统的一半。在这种扫描方式下,现有的重建方法是首先利用重排算法获得180度范围内的平行束投影数据,然后再利用滤波反投影(FBP)算法重建出物体的三维图像。但是重排算法不可避免地会引入误差,降低重建图像的空间分辨率。本文提出了一种反投影滤波(BPF)形式的直接反投影重建方法,该方法不需要对投影数据重排,直接反投影滤波重建出最终的图像。因此,该算法在数学上更简洁,计算速度更快,能够更多地保留重建图像的高频信息。最后,数值模拟实验结果验证了该系统和重建算法能够获得高质量的CT图像。
Abstract:
In a traditional cone-beam CT system,the cost of product and computation is very high.In this paper,we discuss a transversely truncated cone-beam X-ray CT system with a reduced size detector positioned off-center,in which X-ray beams only cover half of the object.The reduced detector size cuts the cost and the X-ray dose of the CT system.The existing reconstruction algorithm is to get the parallel projections in 180 degrees using rebinding method.Then,it uses filtered-back projection(FBP) algorithm to get the final images.But,rebinding will introduce blurring and reduce image resolution.Hence,we develop a BPF-type direct back projection algorithm.Different from the traditional rebinding methods,our algorithm directly back projects the pretreated projection data without rebinding.This makes the algorithm compact and computationally more efficient.Finally,some numerical simulations are done to validate the proposed algorithm.
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