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Development of High Speed and High Precision X-ray Image Reconstruction System in Computed Tomography for Soft Tissues Based on The Non-Uniform Sampling Theorem

基于非均匀采样定理的软组织计算机断层扫描高速高精度X射线图像重建系统的研制

基本信息

批准号：
15560356
负责人：
SASAKI Kimio
金额：
$ 1.6万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

For the purpose of developing a high speed and high precision X-ray CT image reconstruction system for soft tissues, we investigated the previously proposed 2D-image reconstruction method in computed tomography based on the non-uniform sampling theorem, from the viewpoints of both software and hardware implementations, in order to enhance its performance, i.e., sensitivity reduction to additive noises in projection data acquisition and highly speedy image reconstruction, and the following main results are obtained :(1)By automatically extracting the spatial frequency spectrum superior to the estimated mean level of the noises at high frequency, sensitivity of the system to them is reduced to an amount lower than that of the 2D-FT method, which is the most precise one of the conventional. As a result, precision of the system is enhanced by 6dB to 10dB, compared with that of the previously proposed one under the detected SNR of 40dB to 20dB, while its reduction being suppressed only by a … More n amount less than or equal to 0.5dB when no noise exists.(2)The newly developed method mentioned above is effective for reducing computation time. It can save 74% of the time by the previously proposed, but needs an extra time by the amount of 30% more than that by the conventional 2D-FT one. Since the developed method works further effectively with increase of the noise level, it is expected to reconstruct the image in a computation time comparable with the latter in actual applications.(3)With a high speed DSP board of floating point type, computation time is reduced to 64% of that by the previous method without any reduction of precision, while it is to 38% with reduced precision of about 10dB when the DSP of fixed point type being used. In this research, to detour storing the vast amount of sine and cosine table required for 2D-IDFT of non-uniformly sampled spatial frequency spectrum, the previously proposed speedy iterative algorithm based on the additive law of triangular functions is used, but contrary, the algorithm is considered to inhibit the high speed calculation ability by the pipeline processing equipped with the DSPs.(4)By computer simulation based on the developed algorithm of iterative parallel processing, it is confirmed that iteratively reconstructed images can be observed every a pre-designated amount of projection data is acquired, and the final image can be reconstructed almost in a computation time inversely proportional to the number of used personal computers, just after all the projection data have been acquired. Less

为了开发一种高速、高精度的软组织X射线CT图像重建系统，从软件和硬件两个方面研究了基于非均匀采样定理的计算机断层扫描二维图像重建方法，以提高其性能，（1）通过自动提取优于估计的高频噪声平均水平的空间频谱上级，使系统对噪声的敏感性降低到比传统方法中最精确的2D-FT方法低的程度。结果表明，在信噪比为40 ~ 20 dB的情况下，系统的精度比原系统提高了6dB ~ 10 dB，而其降低仅被抑制了 ...更多信息无噪声时，n ≤ 0.5dB。（2）上述新发展的方法对于减少计算时间是有效的。它可以节省74%的时间，由以前提出的，但需要额外的时间的数量比传统的2D-FT的一个30%以上。由于所开发的方法进一步有效地工作与噪声水平的增加，预计重建图像的计算时间与后者在实际应用中。（3）在浮点型高速DSP板上，计算时间减少到原方法的64%，而精度没有降低;在定点型DSP板上，计算时间减少到原方法的38%，精度降低约10 dB。针对非均匀采样空间频谱二维离散傅里叶变换（2D-IDFT）所需的大量正弦和余弦表的存储问题，本文采用了基于三角函数加法律的快速迭代算法，但DSP的流水线处理限制了算法的高速运算能力。(4)By基于所开发的迭代并行处理算法的计算机模拟证实，每次采集预定量的投影数据时，都可以观察到迭代重建的图像，并且几乎可以在与所使用的个人计算机的数量成反比的计算时间内重建最终图像，就在已经采集了所有的投影数据之后。少