共查询到19条相似文献,搜索用时 171 毫秒
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光学层析技术中常见迭代重建算法的误差分析 总被引:1,自引:1,他引:0
为了得到较好的重建结果,对光学层析技术中常见迭代重建算法中的代数重建算法(ART)和同时迭代重建算法(SIRT)的重建参数进行分析,通过选择重建参数和计算机数值模拟达到重建要求.计算机数值模拟证明了松弛因子的选择对迭代重建算法的重建结果有非常重要的影响.在ART算法中,其他重建条件一定,松弛因子太大或太小时重建误差都会增大,松弛因子在0.4~1.5范围内时重建精度基本满足要求,最优松弛因子约为0.8;在SIRT算法中,松弛因子在4~12范围内时重建精度基本满足要求,最优松弛因子约为12.总结出代数重建算法和同时迭代重建算法不同条件下松弛因子选择的规律.在ART算法中,投影方向数增加松弛因子减小, 每方向投影数与重建分辨率对松弛因子无影响,松弛因子一定的情况下,投影数太小或太大误差会增大.在SIRT算法中,投影方向数增加松弛因子减小,并且投影方向数增加一倍最优松弛因子约减小为原来的50%; 每方向投影数增加最优松弛因子减小,且投影数增加一倍,最优松弛因子约减小原来的50%; 重建分辨率增加,最优松弛因子增加. 相似文献
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一种正交二视角光学层析重建算法 总被引:1,自引:0,他引:1
提出了一种基于最大熵原理的正交二视角重建算法,该算法能够较好地重建多峰非对称待测场,且只需两个正交方向的投影数据。算法中融合了含有轴对称因子的先验知识,该先验知识可由两个正交方向的投影数据迭代算出,并分析了正交投影方向这个因素对重建结果的影响。通过计算机数值模拟,结果表明,融合先验知识的正交二视角重建算法与没有融合先验知识的正交二视角重建算法相比重建精度全面超出。其中,在两峰随机余弦高斯模拟待测场的情况下均方根误差减少了73%。在三峰随机高斯模拟待测场的情况下均方根误差减少了47%。该算法充分显示了在重建多峰非对称待测场时的优越性。同时,由于只需要两个正交方向的投影数据,可使实验系统得到简化。 相似文献
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针对光学计算机层析术(Optical Computerized Tomography,OCT)中有限角条件下的严重非完全数据重建问题,提出了正交投影采样,结合基于改进的代数重建术(ART)的先验知识算法,以在尽可能少的投影方向数下较好地重建含遮挡物的三维流场。通过计算机模拟,详细讨论了在有限角条件下含遮挡物的三维流场的非完全数据重建精度及误差分析。结果表明,在有限角及含遮挡物条件下,采用正交投影采样可以极大地减少严重非完全数据重建中的误差,提高重建精度,从而为将光学计算机层析术应用于非完全数据的实测中提供了参考。 相似文献
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在康普顿散射成像(CST)技术中可以结合透射成像重建出衰减系数来消除散射重建的非线性,但这样得到的投影矩阵带有误差。而CST重建问题的不适定性对噪声和投影矩阵的误差非常敏感,重建结果会有较大误差。针对此问题,基于压缩感知理论提出了一种新的CST重建算法。新方法将图像重建问题归结为一个图像的全变分(TV)最小化问题,并使用收敛速度较快的基于交替方向法的Split-Bregman方法进行求解。在仿真实验中,通过与代数重建技术(ART)进行比较,在测量数据充足和测量数据不足两种情况下,本文算法都具有更好的重建质量,证明了所提算法在重建精度和抗噪性能方面的优势。 相似文献
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基于压缩传感和代数重建法的CT图像重建 总被引:4,自引:0,他引:4
代数重建法(ART)是一种重要的CT图像重建方法,适合于不完全投影数据的图像重建,其缺点是重建速度慢。为提高图像重建的质量和速度,利用压缩传感理论提出了一种基于ART的高质量图像重建算法。该算法将CT图像的梯度稀疏性结合到ART图像重建中,在每次迭代中的投影操作结束后用梯度下降法调整全变差,减小图像梯度的l1范数。实验结果验证了该算法的有效性。 相似文献
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基于三投影方向的层析重建分析 总被引:2,自引:0,他引:2
针对传统的层析方法中,投影方向多、系统复杂等特点,提出了基于三个投影方向的层析重建方法.论文选取适用于少投影方向的代数迭代重建算法,采用参量修正方法,能较好的提高重建准确度和抑制椒盐噪音.同时对影响重建图像质量和速度的迭代次数、不同原图像结构对重建图像质量的影响进行了分析,给出了相应分析模拟结果.结果表明,迭代300次后,重建结果基本稳定.同时对于具有轴对称结构物体,三个方向投影数据能够较好地实现三维层析重建.分析结果为后期开展的基于单幅层析全息图的三维层析重建实验研究提供了理论依据. 相似文献
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针对传统的层析方法中,投影方向多、系统复杂等特点,提出了基于三个投影方向的层析重建方法.论文选取适用于少投影方向的代数迭代重建算法,采用参量修正方法,能较好的提高重建准确度和抑制椒盐噪音.同时对影响重建图像质量和速度的迭代次数、不同原图像结构对重建图像质量的影响进行了分析,给出了相应分析模拟结果.结果表明,迭代300次后,重建结果基本稳定.同时对于具有轴对称结构物体,三个方向投影数据能够较好地实现三维层析重建.分析结果为后期开展的基于单幅层析全息图的三维层析重建实验研究提供了理论依据. 相似文献
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A modified discrete algebraic reconstruction technique for multiple grey image reconstruction for limited angle range tomography 下载免费PDF全文
Zhiting Liang Yong Guan Gang Liu Xiangyu Chen Fahu Li Pengfei Guo Yangchao Tian 《Journal of synchrotron radiation》2016,23(2):606-616
The `missing wedge', which is due to a restricted rotation range, is a major challenge for quantitative analysis of an object using tomography. With prior knowledge of the grey levels, the discrete algebraic reconstruction technique (DART) is able to reconstruct objects accurately with projections in a limited angle range. However, the quality of the reconstructions declines as the number of grey levels increases. In this paper, a modified DART (MDART) was proposed, in which each independent region of homogeneous material was chosen as a research object, instead of the grey values. The grey values of each discrete region were estimated according to the solution of the linear projection equations. The iterative process of boundary pixels updating and correcting the grey values of each region was executed alternately. Simulation experiments of binary phantoms as well as multiple grey phantoms show that MDART is capable of achieving high‐quality reconstructions with projections in a limited angle range. The interesting advancement of MDART is that neither prior knowledge of the grey values nor the number of grey levels is necessary. 相似文献
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<正>With the development of the compressive sensing theory,the image reconstruction from the projections viewed in limited angles is one of the hot problems in the research of computed tomography technology.This paper develops an iterative algorithm for image reconstruction,which can fit most cases.This method gives an image reconstruction flow with the difference image vector,which is based on the concept that the difference image vector between the reconstructed and the reference image is sparse enough.Then the l_2-norm minimization method is used to reconstruct the difference vector to recover the image for flat subjects in limited angles.The algorithm has been tested with a thin planar phantom and a real object in limited-view projection data.Moreover,all the studies showed the satisfactory results in accuracy at a rather high reconstruction speed. 相似文献
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计算机断层成像(computed tomography,CT)技术在医学和工业无损检测中都具有非常广泛的应用,CT重建算法是其中的核心,而不完全角度重建问题则是实际应用中重建算法研究领域的一个热点和难点问题.近年来,随着稀疏优化理论与算法的飞速发展,基于稀疏优化的重建算法已经在不完全角度重建问题中得到了较广泛的应用,且表现出了良好的精度与速度性能.本文首先对稀疏优化的基本理论结论与常用算法进行了介绍;而后对稀疏优化理论在CT图像不完全角度重建中的应用进行归纳,分类介绍了其主要研究成果及稀疏优化所发挥的作用;最后对基于稀疏优化的不完全角度重建研究进行了展望. 相似文献
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Mojette变换是一种最小冗余采样的离散Radon变换,能够用较少角度的投影数据进行精确的计算层析(computed tomography,CT)重建,为少量投影角度CT技术的实现提供了一种新思路.投影角度的空间布局决定了层析重建最少所需投影的数量.为了获得Mojette变换层析技术中的最优投影空间角度布局方案,本文对三维Mojette变换数学模型及其精确重建条件进行了研究.以此为基础,在考虑实际探测器像素数目受限的条件下,提出了确定最优投影角度的方法.研究结果表明:所有探测器围绕被测物体在同一水平面内进行平行投影采集是最优的投影角度布局方案,此时投影模型为二维Mojette变换,所需的投影角度和探测器像素数最少,投影角度范围最小;若在实际的测量中该投影条件无法满足,则投影矢量中|pi|和|qi|的值越小越好.该研究可为实际层析系统的建立提供理论基础. 相似文献
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A new sparse tomography method for observing the rapid internal microstructure evolution of material, called the Algebraic Filtered-Back-Projection and Total Variation Minimization (AFBP-TVM) iteration sparse reconstruction algorithm, was proposed in this paper. The new algorithm was developed by combining the two techniques of the Algebraic Reconstruction Technique (ART) and the Filtered-Back-Projection (FBP) on the basis of analysis in linear space. A series of numerical reconstruction experiments were conducted to validate the new algorithm. The results indicated the new algorithm can obtain satisfactory reconstruction images from 1/6 of the projections that were used in traditional algorithms. So the time spent on projection acquisition process can be reduced to 1/6 of that in traditional tomography method. The quality of images reconstructed by new algorithm was better than other algorithms, which was evaluated by three quantitative parameters. The normalized average absolute distance criterion and the normalized mean square criterion, which were used to evaluate the relative error of the reconstruction results (smaller value means better quality of reconstruction), decreased from 0.3758 to 0.1272 and from 0.1832 to 0.0894 respectively. The standardized covariance criterion, which was used to evaluate the similarity level (greater value means higher accuracy of reconstruction), increased from 92.72% to 99.30%. Finally, the new algorithm was validated under actual experimental conditions. The results indicated that the AFBP-TVM algorithm obtained better reconstruction quality than other algorithms. It meant that the AFBP-TVM algorithm may be a suitable method for in situ investigation on material's rapid internal microstructure evolution in extreme complex environment. 相似文献
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Novel Fourier-based iterative reconstruction for sparse fan projection using alternating direction total variation minimization 下载免费PDF全文
Sparse-view x-ray computed tomography(CT) imaging is an interesting topic in CT field and can efficiently decrease radiation dose. Compared with spatial reconstruction, a Fourier-based algorithm has advantages in reconstruction speed and memory usage. A novel Fourier-based iterative reconstruction technique that utilizes non-uniform fast Fourier transform(NUFFT) is presented in this work along with advanced total variation(TV) regularization for a fan sparse-view CT. The proposition of a selective matrix contributes to improve reconstruction quality. The new method employs the NUFFT and its adjoin to iterate back and forth between the Fourier and image space. The performance of the proposed algorithm is demonstrated through a series of digital simulations and experimental phantom studies. Results of the proposed algorithm are compared with those of existing TV-regularized techniques based on compressed sensing method, as well as basic algebraic reconstruction technique. Compared with the existing TV-regularized techniques, the proposed Fourier-based technique significantly improves convergence rate and reduces memory allocation, respectively. 相似文献