共查询到19条相似文献,搜索用时 109 毫秒
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采用光谱分析技术,系列研究了已有代数迭代重建算法,并进一步研制了改进算法—简单自相关代数迭代重建算法(SSART)。采用数值模拟的方法模拟重建一个含遮挡物场,研究了SSART模拟效果和重建精度。作为对照,分析了已有的传统代数迭代算法同条件下的重建结果,包括基本代数迭代重建算法(ART)、联合代数迭代重建法(SART)和改进的联合代数迭代重建法(MSART)。重建精度用均方误差(MSE),绝对平均误差(AVE)和峰值相对误差(PE)三种误差指数标定。结果发现,SSART重建结果的三种误差指数都明显减小,其中MSE在10-4数量级上比ART的降低了26.6%,PE在10-2数量级降低了77.6%。因此,SSART重建含遮挡物模型场时,重建精度大幅度提高,重建效果明显改善,对传统代数迭代重建算法显著改进。 相似文献
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稀疏角度下图像重建算法的研究是发射光谱层析技术在场分布测量方面应用的关键问题。代数重建算法、同时迭代重建算法以及联合代数重建算法是其中应用较为广泛的迭代类图像重建算法。以蜡烛火焰为重建对象,利用均方差、峰值信噪比、结构相似性和图像平均梯度等图像质量评价指标来分析评价不同算法的图像重建效果,并发展了一种多指标优化算法融合的技术,充分利用三种算法的恢复重建优势,实现了火焰三维温度场的分区重建,重建温度误差在5%以内。实验结果证明,所发展的算法融合技术适用于火焰三维温度场的高质量重建。 相似文献
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烟羽断层重建质量受两方面条件限制:其中一个限制条件是遥感设备的时间分辨率。以往的研究多使用多轴差分吸收光谱仪(MAX-DOAS)进行CT重建,受采集数据速度的限制,重建图像的时间分辨率较低。另一个限制条件是,采集到的数据量有限,是典型的不完全角度重建。过去多使用代数迭代重建算法或统计迭代重建算法,重建图像受测量误差的影响比较大,分辨率较低且伪影较多。构造了基于成像差分吸收光谱技术(IDOAS)的光谱数据采集系统,与多轴差分吸收光谱仪构造的系统相比,数据采集的时间分辨率提高了160多倍,基本解决了时间分辨率的问题。提出了一种基于压缩感知理论和低三阶导数模型的烟羽断层重建算法--投影凸函数集低三阶导数法,简称为POCS-LTD。在投影的过程中,使用代数重建算法使重建图像符合投影方程;在全变分迭代的过程中使用了优化算法,将低三阶导数模型的全变分归一化值作为优化算法的迭代方向,前次迭代运算结果与本次投影运算的差值的模作为迭代步长。对重建算法进行了数值模拟,并以重建图像的接近度和一致性相关因子为指标,对重建结果进行了分析。数值模拟表明,算法具有良好的抗误差能力,与传统的低三阶导数法相比,本文提出的算法将重建接近度减小了80%以上。使用烟羽数据采集系统进行了外场实验,用POCS-LTD算法对外场实验的数据进行了烟羽重建,重建图像显示烟羽图像清晰,伪影得到了较好的抑制。介绍的烟羽断层数据采集系统和烟羽断层重建算法,提高了烟羽断层重建图像的时间分辨率,减少了重建图像的伪影,扩大了光谱测量技术的应用范围。 相似文献
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光声成像结合了光学成像和声学成像的优点,是一种高分辨率,高对比度的无损伤医学成像技术.一种改进的同步迭代算法应用于光声图像重建.仿真和模拟结果表明,与传统的代数迭代算法相比,在90°,135°,180°的有限场光声成像中,此算法对测量误差的校正和迭代次数的收敛上具有较大的优势,图像重建的速度和成像质量都有了明显的提高.实验中,一种圆形扫描结构的光声成像装置,用于180°的有限场扫描,利用改进的同步迭代算法,重建出了高对比度和高分辨率(60μm)的鸡胚胎光声血管图像.实验证明,这种算法的应用,大幅度减少了数据采集时间,为光声成像技术运用于实时监测血流灌注和肿瘤光动力治疗的血管损伤效应提供了潜在的应用价值.
关键词:
光声成像
有限角度
代数迭代算法
光声血管成像 相似文献
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《中国光学与应用光学文摘》2004,(4)
基于高斯机(GM)提出了一种新的少数投影CT图像重建算法。首先将图像重建问题转化为最大嫡准则下的优化问题,然后构造相应的GM模型,并采用双曲调度进行模拟退火,网络的稳定解就是重建问题的优化解。数值模拟结果表明,与联合代数重建技术(SART)相比,从投影角间距为450的4个不同的投影视角方向获取投影数据时,该算法具有较高的重建精 相似文献
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针对人体组织电导率的三维成像问题,提出一种改进的分层灵敏度磁共振电阻抗重建算法.利用单方向磁感应强度信息,对三维电导率图像实行分层重建,每层重建仅利用该层磁通密度分量测量数据,然后对单层重建结果进行修正以获得三维电导率重建图像.三介质长方体模型上的仿真实验证明,改进的分层重建算法改善了层间串扰现象,可以获得比一般分层算法甚至整体算法更高的图像分辨率,而且重建时间较整体算法显著减少;基于人体腿模型的仿真实验表明该算法对复杂模型三维重构的可行性;最后通过仿体实验验证算法的重建效果.改进的分层灵敏度重建算法降低了灵敏度矩阵法的计算机硬件需求,减少了重建时间,对MREIT的三维重建具有较高的成像精度和求解效率. 相似文献
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X射线折射衬度CT是一种基于相位衬度的断层成像技术,特别适合对由轻元素组成的生物、医学样品进行成像,可以观察到常规吸收衬度CT无法观察到的软组织内部微细结构,是一种具有巨大发展潜力的新成像方法.迭代重建算法和解析重建算法是计算机断层成像技术中并行发展的两种算法,虽然已经提出了几种X射线折射衬度CT的解析重建算法,可是还未见X射线折射衬度CT迭代重建算法的报道.研究了代数迭代重建算法在X射线折射衬度CT中的应用,比较分析了不同的投影数据排列方式对于折射衬度CT重建图像的影响,并对实验数据进行了图像重建,获得了满意的CT图像.研究结果表明,在相位衬度CT中,迭代重建算法相对于解析重建算法而言,能减少投影次数,降低曝光剂量,减少对生物样品的辐射损伤,在生物样品成像和投影数据不完整的情况下具有明显的优势.
关键词:
衍射增强成像
代数迭代算法
CT重建
同步辐射 相似文献
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简单自相关代数迭代重建算法 总被引:3,自引:3,他引:0
创建了简单自相关代数迭代重建算法(simple self-correlative algebraic reconstruction technique, SSCART),分析了其重建效果。采用数值模拟的方法,对代数迭代法(algebraic reconstruction technique, ART)与SSCART两种算法进行了计算机模拟,分析了模拟效果和重建精度。结果发现,SSCART算法的重建精度均方误差(mean square error, MSE)指标在10-4数量级上比ART的降低了65%[(ART的MSE值-SSCART的MSE)/ART的MSE],峰值相对误差(peak error, PE)指标在10-2数量级上降低了99.9%。计算上仅仅比ART多1个除数因子,所以SSCART具有算法简单、易于实现、重建精度高、稳定性好等优点。就作者检索的文献看是目前最优秀的代数迭代法。 相似文献
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Algebraic tomographic reconstruction of two-dimensional gas temperature based on tunable diode laser absorption spectroscopy 总被引:1,自引:0,他引:1
Junling Song Yanji Hong Guangyu Wang Hu Pan 《Applied physics. B, Lasers and optics》2013,112(4):529-537
Based on tunable diode laser absorption spectroscopy, the combustion gas temperature distribution was reconstructed using the algebraic iterative reconstruction technique. The effects of the projected angle and number of rays on the temperature reconstruction results for both fan beam and parallel beam were investigated. The flow field information was shown in detail. The reconstruction quality increased with increased ray number for both parallel- and fan-beam projections. The trend tended to be smooth when the total number of beams exceeded 100. A virtual ray method combined with the reconstruction algorithms was proposed. The virtual ray method is effective to improve the accuracy of reconstruction results for the symmetric and non-axisymmetric temperature distributions. Moreover, the temperature reconstruction of an infrared gas-field furnace is demonstrated, showing the virtual ray method can be applied to the combustion diagnostics. 相似文献
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Modified adaptive algebraic tomographic reconstruction of gas distribution from incomplete projection by a two-wavelength absorption scheme 总被引:1,自引:0,他引:1
A modified adaptive algebraic reconstruction technique (MAART) with an auto-adjustment relaxation parameter and smoothness regularization is developed to reveal the tomographic reconstruction of H 2 O distribution in combustion from incomplete projections. Determinations of relaxation parameter and regularization factor are discussed with regard to the consideration of improvement in reconstruction and reduction of computational burden. A two-wavelength scheme from tunable diode laser absorption measurement, 7444.36 and 7185.59 cm 1 , is used to simplify the nonlinear solution problem for obtaining the tomographic distributions of concentration and temperature simultaneously. Results of calculations demonstrate that MAART can perform the reconstruction results more efficiently with little complex modification and much lower iterations as compared with the traditional algebraic reconstruction technique (ART) or simultaneous iterative reconstruction technique (SIRT) methods. The stability of the algorithm is studied by reconstruction from projections with random noise at different levels to demonstrate the dependence of reconstruction results on precise line-of-sight measurements. 相似文献
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An iterative image reconstruction algorithm combined with forward and backward diffusion filtering for in‐line X‐ray phase‐contrast computed tomography
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Yuqing Zhao Mengyu Sun Dongjiang Ji Changhong Cong Wenjuan Lv Qi Zhao Lili Qin Jianbo Jian Xiaodong Chen Chunhong Hu 《Journal of synchrotron radiation》2018,25(5):1450-1459
In‐line X‐ray phase‐contrast computed tomography (IL‐PCCT) can reveal fine inner structures for low‐Z materials (e.g. biological soft tissues), and shows high potential to become clinically applicable. Typically, IL‐PCCT utilizes filtered back‐projection (FBP) as the standard reconstruction algorithm. However, the FBP algorithm requires a large amount of projection data, and subsequently a large radiation dose is needed to reconstruct a high‐quality image, which hampers its clinical application in IL‐PCCT. In this study, an iterative reconstruction algorithm for IL‐PCCT was proposed by combining the simultaneous algebraic reconstruction technique (SART) with eight‐neighbour forward and backward (FAB8) diffusion filtering, and the reconstruction was performed using the Shepp–Logan phantom simulation and a real synchrotron IL‐PCCT experiment. The results showed that the proposed algorithm was able to produce high‐quality computed tomography images from few‐view projections while improving the convergence rate of the computed tomography reconstruction, indicating that the proposed algorithm is an effective method of dose reduction for IL‐PCCT. 相似文献
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Deflection tomographic reconstruction of a complex flow field from incomplete projection data 总被引:1,自引:0,他引:1
Tomographic techniques are used for the investigation of complex flow fields by means of deflectometric methods. In this experiment, a modified algebraic reconstruction technique (ART) was applied to moiré deflection tomography. The algorithm was derived from the basic deflection formula and the deflection angles were used directly in iteration, which is completely different from the conventional ARTs with integral calculation that are commonly used in deflection tomography. A smoothing scheme was employed to improve the reconstruction under ill-posed conditions. The reconstruction technique was tested using simulated data for incompleteness conditions similar to those found in the experimental data. The complex density field with an opaque object in a supersonic wind tunnel was reconstructed from limited view angle projections, and the experimental reconstruction was then compared with the result obtained from the computational fluid dynamic analysis. The following paper details the experiment and discusses some measurement errors that occurred in the process. 相似文献
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Chunfang Li 《Optik》2013
Optical CT is now expanding into reconstruction from few views or limited-view range projection considering the economy and practicality. To solve the conflict of velocity and precision, which are two main aims that image reconstruction algorithm pursued, an innovative complex image reconstruction algorithm for real-time measurement of transient field is proposed. This method reconstructs computerized tomography (CT) image firstly by frequency spectrum approach reconstruction technique (FSART) and then by modified simultaneous algebraic reconstruction technique (MSART) and can give a fast and precise reconstruction to complicated transient field. 相似文献