共查询到17条相似文献,搜索用时 281 毫秒
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研究了光声信号声速失配时所起的声折射对光声成像的影响,提出了利用与组织声速匹配的耦合液进行光声成像,并配置了几种适合于组织声速的超声耦合液.实验结果表明,进行声速匹配后重建出的图像对比度有明显地提高,背景伪迹减少,分辨率由0.50 mm提高到0.15 mm,重建图像与实物十分吻合. 相似文献
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多种光声成像方法研究 总被引:1,自引:0,他引:1
阐述了光声成像的基本原理,综述了现有的几种光声成像方法、原理及成果。介绍了国内外多个研究小组在光声成像领域所取得的一些成果,主要包括:用超声探测器记录光声信号的滤波反投影算法光声成像;超声探测器结合声透镜的傅里叶方法;用探测光做载波调制光声信号,将光声信号转化为光信号,经光学系统解调,将样品像显示在CCD摄像机上的实时光声成像等。对比了几种光声成像方法,并提出了一些光声成像的新思路。 相似文献
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光声计算断层成像(PACT)是近年来迅速发展的一种无损生物医学成像技术,在生物医学领域有着较高的应用价值。为了获得高质量的光声图像,成像系统的信号采集装置需要配备高密度的阵列探测器。但在实际应用中,由于经济成本、制造工艺及成像时间等因素的限制,探测器的排布往往较为稀疏,难以实现稳定重建,导致重建图像中出现条纹伪影。为了解决这一问题,本文提出一种基于双域神经网络的PACT图像重建算法。该算法主要包含三个模块:数据域网络、反投影层和图像域网络,其中数据域网络和图像域网络可分别对光声数据和光声图像进行增强,以提升图像质量。为了对网络进行训练和测试,构建了一个血管仿真数据集和一个小鼠活体试验数据集。研究结果表明,所提算法可以有效地抑制条纹伪影,提升图像质量,并且重建性能优于其他重建算法。 相似文献
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为了实现对飞秒光丝内部空间结构特征的精细化描述,通过对光丝诱导形成超声信号的正向传播过程进行精细化模拟,然后采用通用反投影算法(UBP)、延迟叠加算法(DAS)和超优光声非负重构算法(SPANNER)等多种光声层析图像重建算法进行反向重建,理论验证了利用多元线性阵列探测的方式重建飞秒单丝和多丝轴向r-z截面图像的可行性。结果表明,当探测距离为3 mm时,单丝和多丝诱导形成的超声信号最大频率约为5 MHz;光声层析法能够较为准确地实现对单丝位置、r-z截面轮廓等信息的反演,但是不同图像重建算法重建效果差异较大。UBP重建算法对单丝的重建存在较为明显的伪影现象;DAS重建算法由于受到“有限孔径效应”的影响,高估了光丝的直径;SPANNER重建算法由于使用最优理论来改进非线性共轭梯度算子,实现了非负性和各向异性总变分正则化,可有效避免噪声干扰,因而对多丝图像的重建效果最好。该研究结果对于揭示光丝结构特征和促进基于光丝的大气应用研究具有一定的参考价值。 相似文献
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为了提高激光反射断层成像目标重构的图像质量,在目前激光反射断层成像普遍采用反投影算法重构图像的基础上,将CT成像中常用的迭代重建算法引入到激光反射断层成像的图像重构过程中。分析了反投影算法中的直接反投影、R-L和S-L滤波反投影以及迭代重建算法在图像重构中的性能特性。进行了仿真和外场实验,结果表明:在直接反投影基础上添加了滤波器的反投影算法在减小误差和抑噪能力上都明显提高;另外相比于反投影算法,代数迭代重建算法表现出更好的重建质量,且具有更强的抑噪性能。 相似文献
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The row action projection (RAP) method is used to increase the spatial resolution of images reconstructed via the filtered back projection (FBP) algorithm. An implementation of RAP is introduced which is computationally efficient and facilitates local adaptation of the projection operators. The local mean value as well as minimum and maximum bounds are used as constraints. The method is proposed to provide zoom-in capability, which yields a high-resolution estimate of a specified region of the image. Computer simulations demonstrate the new method to be very effective in recovering high-order spectral components of designated regions of the reconstructed image. 相似文献
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A new localized computerized tomography technique based on the multiresolution analysis (MRA) implementation of the discrete wavelet transform is proposed. Our technique is based upon viewing the projection data as a set of one-dimensional functions of the space variablet and decomposing each one into an approximation signal and a set of detail signals using MRA. The approximation signal and detiil signals associated with each projection are filtered using the ramp filter || of the standard reconstruction technique filtered back projection to generate the set of filtered projections. It is shown that only a very sparse set of projection data outside of the region of interest (ROI) is required to reconstruct a high-quality image of the ROI and a reasonable image outside of the ROI. Simulation results using the Shepp-Logan head phantom are presented to demonstrate the proposed technique. 相似文献
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A back projection of filtered projection (BKFIL) reconstruction algorithm is presented that is applicable to single-photon emission computed tomography (ECT) in the presence of a constant attenuating medium such as the brain. The filters used in transmission computed tomography (TCT)-comprised of a ramp multiplied by window functions?are modified so that the single-photon ECT filter is a function of the constant attenuation coefficient. The filters give good reconstruction results with sufficient angular and lateral sampling. With continuous samples the BKFIL algorithm has a point spread function that is the Hankel transform of the window function. The resolution and statistical properties of the filters are demonstrated by various simulations which assume an ideal detector response. Statistical formulas for the reconstructed image show that the square of the percent-root-mean-square (percent-rms) uncertainty of the reconstruction is inversely proportional to the total measured counts. The results indicate that constant attenuation can be compensated for by using an attenuation-dependent filter that reconstructs the transverse section reliably. Computer time requirements are two times that of conventional TCT or positron ECT and there is no increase in memory requirements. 相似文献
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大面积非晶硅平板探测器在工业透射射线成像领域得到越来越多的应用.基于FPD的圆轨道FDK型三维计算机层析成像技术(3D-CT)检测速度快,但成像质量不及2D-CT.为发挥3D-CT速度优势,抑制噪声,同时提高图像重建的质量,以由平板探测器得到的二维投影数据为研究对象,提出了一种对投影数据进行小波分解,分别对高频和低频进行两次滤波的投影预处理方法,然后将分别重建的图像叠加,最终得到高质量的重建图像.算法的仿真实验结果表明,重建图像质量得到明显改善,系统噪声得到抑制. 相似文献
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We present a dual-energy (DE) transmission computed tomography (CT) reconstruction method. It is statistically motivated and features nonnegativity constraints in the density domain. A penalized weighted least squares (PWLS) objective function has been chosen to handle the non-Poisson noise added by amorphous silicon (aSi:H) detectors. A Gauss-Seidel algorithm has been used to minimize the objective function. The behavior of the method in terms of bias/standard deviation tradeoff has been compared to that of a DE method that is based on filtered back projection (FBP). The advantages of the DE PWLS method are largest for high noise and/or low flux cases. Qualitative results suggest this as well. Also, the reconstructed images of an object with opaque regions are presented. Possible applications of the method are: attenuation correction for positron emission tomography (PET) images, various quantitative computed tomography (QCT) methods such as bone mineral densitometry (BMD), and the removal of metal streak artifacts. 相似文献