共查询到20条相似文献,搜索用时 15 毫秒
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Naoki Kanata Takeshi Yoshikawa Yoshiharu Ohno Tomonori Kanda Koji Uchida Kenta Izaki Takumi Fukumoto Yonson Ku Tomoo Itoh Kazuhiro Kitajima Satoru Takahashi Kazuro Sugimura 《Magnetic resonance imaging》2013
The purpose of this study was to assess the efficacy of arterial-dominant phase images of gadolinium–ethoxybenzyl–diethylenetriamine pentaacetic acid (EOB)-enhanced magnetic resonance imaging (MRI) for evaluation of arterial blood supply in hepatocellular carcinoma (HCC) in comparison with that of multiphasic dynamic computed tomography (CT). This study comprised 30 patients (22 men and 8 women, mean age: 68.0 years) with 40 pathologically proven HCCs (well differentiated: 3, moderately differentiated: 30, poorly differentiated: 7, mean diameter: 45.1 mm), all of whom underwent EOB-enhanced MRI and dynamic CT preoperative assessment. Regions of interest were placed over HCCs and the adjacent normal liver, and signal intensities or CT values were measured by two experienced abdominal radiologists on the arterial-dominant phase images of EOB-enhanced MRI and dynamic CT images. HCC-to-liver contrasts [Michelson's contrast: CM=(SHCC− SLiver)/(SHCC+ SLiver)] were calculated and compared among the modalities. HCC-to-liver contrasts were also visually scored on a 5-point scale and compared. The mean CM and visual score for dynamic CT were significantly higher than those for EOB-enhanced MRI. Good agreements were obtained among the two observers. Dynamic CT is a more suitable modality than EOB-enhanced MRI for evaluation of arterial blood supply in HCC. This should be taken into account for diagnosis and management of HCC. 相似文献
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This paper proposes a novel image fusion scheme based on contrast pyramid (CP) with teaching learning based optimization (TLBO) for visible and infrared images under different spectrum of complicated scene. Firstly, CP decomposition is employed into every level of each original image. Then, we introduce TLBO to optimizing fusion coefficients, which will be changed under teaching phase and learner phase of TLBO, so that the weighted coefficients can be automatically adjusted according to fitness function, namely the evaluation standards of image quality. At last, obtain fusion results by the inverse transformation of CP. Compared with existing methods, experimental results show that our method is effective and the fused images are more suitable for further human visual or machine perception. 相似文献
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Optical windows with external surfaces shaped to satisfy operational environment needs are known as special windows. A novel special window, a sphere-cone-polynomial (SCP) window, is proposed. The formulas of this window shape are given. An SCP MgF2 window with a fineness ratio of 1.33 is designed as an example. The field-of-regard (FOR) angle is ±75°. From the window system simulation results obtained with the calculated fluid dynamics (CFD) and optical design software, we find that compared to the conventional window forms, the SCP shape can not only introduce relatively less drag in the airflow, but also have the minimal effect on imaging. So the SCP window optical system can achieve a high image quality across a super wide FOR without adding extra aberration correctors. The tolerance analysis results show that the optical performance can be maintained with a reasonable fabricating tolerance to manufacturing errors. 相似文献
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OCT图像法测量折射率 总被引:2,自引:0,他引:2
基于光程匹配原理提出了一种用光学相干断层成像(OCT)系统获得的图像测量样品折射率的方法。通过分析光程匹配原理,给出用OCT图像法测量样品折射率的原理及过程。以玻璃载波片和黄瓜组织为样品进行实验。实验结果表明,用OCT图像法获得的载玻片和黄瓜组织的折射率测量值分别为1.499和1.353,与发表或已知的折射率结果相吻合,测试结果的随机误差可小于0.01。另外,使用OCT图像法通过短时间所采集的两幅图像可对横向扫描任意位置的折射率同时进行测量。该方法进一步简化了基于光程匹配原理的折射率测量法的过程,缩短了测量时间,是一种快速测量样品折射率的实用方法。 相似文献
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介绍了利用Mathematica软件包让普通微机通过声卡输出调试信号的方法,并直接用示波器观测了门电路的传输特性曲线。 相似文献
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César R. de Oliveira 《Journal of statistical physics》1988,53(3-4):603-612
A natural definition of an attractor as an invariant measure is given (based on the ergodic theory of axiom A diffeomorphisms) and some results are proved which support this definition. It is also proved that if an attractor has every characteristic exponent less than zero in a set of nonzero measure, then the support set of the attractor is an asymptotic stable periodic orbit. 相似文献
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Gradient echo images of coronal sections through the brains of normal rats have been recorded at 2.0 T both before and at various times after intravenous bolus administrations of a superparamagnetic iron oxide suspension. The decrease in NMR signal due to the transit of the contrast agent has been quantified as a function of time. The image immediately following the injection can be subtracted from that pre-contrast to reveal regional differences related to blood flow. 相似文献
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利用红外热成像系统可将物体的热分布转化为可视图像,并在监视器上以灰度级或伪彩色显示出来,从而得到被测目标的温度分布场。根据热成像测温原理以及红外图像的特点,在对室温热成像系统研究的基础上,对红外图像伪彩色编码进行了研究,提出一种新的伪彩色编码方法,即自动阈值法。利用自动阈值法可以在室温环境下,对目标的温度及其分布进行测量。在TMS320C6202和FPGA室温热成像系统中对提出的方法进行了验证。实验结果表明,该方法可使红外图像层次分明,容易分辨出不同的温度区域。 相似文献
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R. Matthew Ferguson Kannan M. Krishnan 《Journal of magnetism and magnetic materials》2009,321(10):1548-1551
Magnetic particle imaging (MPI) is a powerful new research and diagnostic imaging platform that is designed to image the amount and location of superparamagnetic nanoparticles in biological tissue. Here, we present mathematical modeling results that show how MPI sensitivity and spatial resolution both depend on the size of the nanoparticle core and its other physical properties, and how imaging performance can be effectively optimized through rational core design. Modeling is performed using the properties of magnetite cores, since these are readily produced with a controllable size that facilitates quantitative imaging. Results show that very low detection thresholds (of a few nanograms Fe3O4) and sub-millimeter spatial resolution are possible with MPI. 相似文献
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A hybrid strategy for geometric distortion correction of echo-planar images is demonstrated. This procedure utilizes standard field mapping for signal displacement correction and the so-called reverse gradient acquisition for signal intensity correction. (The term reverse gradient refers to an acquisition of two sets of echo-planar images with phase encoding gradients of opposite polarity.) The hybrid strategy is applied to human brain echo-planar images acquired with and without diffusion-weighting. A comparison of the hybrid distortion corrected images to those corrected with standard field mapping only demonstrates much better performance of the hybrid method. A variant of the hybrid method is also demonstrated which requires the acquisition of only one pair of opposite polarity images within a set of images. 相似文献
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A novel nonsubsampled contourlet transform (NSCT) based image fusion approach, implementing an adaptive-Gaussian (AG) fuzzy membership method, compressed sensing (CS) technique, total variation (TV) based gradient descent reconstruction algorithm, is proposed for the fusion computation of infrared and visible images.Compared with wavelet, contourlet, or any other multi-resolution analysis method, NSCT has many evident advantages, such as multi-scale, multi-direction, and translation invariance. As is known, a fuzzy set is characterized by its membership function (MF), while the commonly known Gaussian fuzzy membership degree can be introduced to establish an adaptive control of the fusion processing. The compressed sensing technique can sparsely sample the image information in a certain sampling rate, and the sparse signal can be recovered by solving a convex problem employing gradient descent based iterative algorithm(s).In the proposed fusion process, the pre-enhanced infrared image and the visible image are decomposed into low-frequency subbands and high-frequency subbands, respectively, via the NSCT method as a first step. The low-frequency coefficients are fused using the adaptive regional average energy rule; the highest-frequency coefficients are fused using the maximum absolute selection rule; the other high-frequency coefficients are sparsely sampled, fused using the adaptive-Gaussian regional standard deviation rule, and then recovered by employing the total variation based gradient descent recovery algorithm.Experimental results and human visual perception illustrate the effectiveness and advantages of the proposed fusion approach. The efficiency and robustness are also analyzed and discussed through different evaluation methods, such as the standard deviation, Shannon entropy, root-mean-square error, mutual information and edge-based similarity index. 相似文献
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干涉图特征信息自动采集方法 总被引:12,自引:1,他引:12
介绍了一种用于计算全息数字波面干涉仪中采用数字图像处理技术采集干涉图的特征信息的方法。它分为图像二值化、条纹细化、条纹修补、跟踪、标记、采样等步骤,对于没有闭合条纹的简单干涉图和有闭合条纹的复杂干涉图,都能得到较好结果。 相似文献
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对于在速调管中广泛使用的重入式谐振腔以及内部无漂移管的盒形腔,在忽略漂移管壁厚的前提下,导出了能够准确求解其谐振频率的本征方程,并在此基础上进一步计算了腔体的特性阻抗和固有品质因数。针对具体算例的应用表明,由解析式确定的腔体特性参数与SUPERFISH的数值结果具有很好的一致性。 相似文献
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By an elementary calculation we obtain the exact mean values of Minkowksi functionals for a standard model of percolating sets. In particular, a recurrence theorem for the mean Euler characteristic recently put forward is shown to be incorrect. Related previous mathematical work is mentioned. We also conjecture bounds for the threshold density of continuum percolation, which are associated with the Euler characteristic. 相似文献