Volume 27, Issue 4

A critical issue in image restoration is the problem of noise removal while keeping the integrity of relevant image information. Denoising is a crucial step to increase image quality and to improve the performance of all the tasks needed for quantitative imaging analysis. The method proposed in this paper is based on a 3-D optimized blockwise version of the nonlocal (NL)-means filter (Buades, , 2005). The NL-means filter uses the redundancy of information in the image under study to remove the noise. The performance of the NL-means filter has been already demonstrated for 2-D images, but reducing the computational burden is a critical aspect to extend the method to 3-D images. To overcome this problem, we propose improvements to reduce the computational complexity. These different improvements allow to drastically divide the computational time while preserving the performances of the NL-means filter. A fully automated and optimized version of the NL-means filter is then presented. Our contributions to the NL-means filter are: 1) an automatic tuning of the smoothing parameter; 2) a selection of the most relevant voxels; 3) a blockwise implementation; and 4) a parallelized computation. Quantitative validation was carried out on synthetic datasets generated with BrainWeb (Collins, , 1998). The results show that our optimized NL-means filter outperforms the classical implementation of the NL-means filter, as well as two other classical denoising methods [anisotropic diffusion (Perona and Malik, 1990)] and total variation minimization process (Rudin, , 1992) in terms of accuracy (measured by the peak signal-to-noise ratio) with low computation time. Finally, qualitative results on real data are presented.

图像恢复中的一个关键问题是在保持相关图像信息完整性的同时去除噪声。去噪是提高图像质量以及改善定量成像分析所需所有任务性能的关键步骤。本文提出的方法基于非局部均值（NL-means）滤波器（Buades等人，2005）的三维优化分块版本。NL-means滤波器利用研究图像中信息的冗余性来去除噪声。NL-means滤波器在二维图像上的性能已经得到验证，但减少计算负担是将该方法扩展到三维图像的关键问题。为了解决这一问题，我们提出了降低计算复杂度的改进措施。这些不同的改进措施能够在保持NL-means滤波器性能的同时大幅缩短计算时间。然后，我们提出了一个全自动且优化的NL-means滤波器版本。我们对NL-means滤波器的贡献包括：1）自动调整平滑参数；2）选择最相关的体素；3）分块实现；4）并行计算。定量验证在BrainWeb（Collins等人，1998）生成的合成数据集上进行。结果表明，与经典NL-means滤波器实现以及其他两种经典去噪方法（各向异性扩散（Perona和Malik，1990）和全变分最小化过程（Rudin等人，1992））相比，我们的优化NL-means滤波器在精度（以峰值信噪比衡量）方面表现更优，且计算时间更短。最后，给出了真实数据的定性结果。

This paper presents an efficient algorithm for segmenting different types of pulmonary nodules including high and low contrast nodules, nodules with vasculature attachment, and nodules in the close vicinity of the lung wall or diaphragm. The algorithm performs an adaptive sphericity oriented contrast region growing on the fuzzy connectivity map of the object of interest. This region growing is ope...

本文提出了一种高效算法，用于分割不同类型的肺结节，包括高对比度和低对比度结节、与血管相连的结节以及靠近肺壁或膈肌的结节。该算法在感兴趣对象的模糊连通性图上执行自适应球度导向对比区域生长。这种区域生长是开放的...

In this paper, a hybrid discriminative/generative model for brain anatomical structure segmentation is proposed. The learning aspect of the approach is emphasized. In the discriminative appearance models, various cues such as intensity and curvatures are combined to locally capture the complex appearances of different anatomical structures. A probabilistic boosting tree (PBT) framework is adopted ...

本文提出了一种用于脑解剖结构分割的混合判别/生成模型。该方法强调了学习方面。在判别外观模型中，结合了强度和曲率等多种线索，以局部捕捉不同解剖结构的复杂外观。采用概率提升树（PBT）框架...

Automated computer classification (ACC) techniques are needed to facilitate physician's diagnosis of complex diseases in individual patients. We provide an example of ACC using computational techniques within the context of cross-sectional analysis of magnetic resonance images (MRI) in neurodegenerative diseases, namely Alzheimer's dementia (AD). In this paper, the accuracy of our ACC methodology ...

自动计算机分类技术有助于医生对个体患者的复杂疾病进行诊断。本文以神经退行性疾病（即阿尔茨海默病）中的磁共振图像横断面分析为例，展示了使用计算技术的ACC方法。本文中，我们的ACC方法的准确性...

This paper presents a new deformable model using both population-based and patient-specific shape statistics to segment lung fields from serial chest radiographs. There are two novelties in the proposed deformable model. First, a modified scale invariant feature transform (SIFT) local descriptor, which is more distinctive than the general intensity and gradient features, is used to characterize th...

本文提出了一种新的可变形模型，利用基于人群和患者特定的形状统计从序列胸片中分割肺野。该可变形模型有两个新颖之处。首先，使用改进的尺度不变特征变换（SIFT）局部描述符，其比一般的强度和梯度特征更具区分性，用于描述图像特征。

We present a fast parallel algorithm to compute the nonequispaced fast Fourier transform on commodity graphics hardware (the GPU). We focus particularly on a novel implementation of the convolution step in the transform as it was previously its most time consuming part. We describe the performance for two common sample distributions in medical imaging (radial and spiral trajectories), and for diff...

我们提出了一种在商用图形硬件（GPU）上计算非等间距快速傅里叶变换的快速并行算法。我们特别关注变换中卷积步骤的新实现，因为该步骤以前是最耗时的部分。我们描述了医学成像中两种常见采样分布（径向和螺旋轨迹）的性能，以及不同...

We apply an information-theoretic cost metric, the symmetrized Kullback-Leibler (sKL) divergence, or $J$-divergence, to fluid registration of diffusion tensor images. The difference between diffusion tensors is quantified based on the sKL-divergence of their associated probability density functions (PDFs). Three-dimensional DTI data from 34 subjects were fluidly registered to an optimized target i...

我们将信息论成本度量——对称的Kullback-Leibler（sKL）散度或J散度——应用于扩散张量图像的流体配准。扩散张量之间的差异基于其相关概率密度函数（PDF）的sKL散度进行量化。来自34名受试者的三维DTI数据被流体配准到优化目标上...

This paper introduces a method to analyze the variability of the spine shape and of the spine shape deformations using articulated shape models. The spine shape was expressed as a vector of relative poses between local coordinate systems of neighboring vertebrae. Spine shape deformations were then modeled by a vector of rigid transformations that transforms one spine shape into another. Because ri...

本文介绍了一种利用铰接形状模型分析脊柱形状及脊柱形状变形变异性的方法。脊柱形状被表示为相邻椎体局部坐标系之间的相对位姿向量。然后通过刚性变换向量对脊柱形状变形进行建模，该向量将一个脊柱形状变换为另一个。由于变...

Estimating the residence times in tumor and normal organs is an essential part of treatment planning for radioimmunotherapy (RIT). This estimation is usually done using a conjugate view whole body scan time series and planar processing. This method has logistical and cost advantages compared to 3-D imaging methods such as Single photon emission computed tomography (SPECT), but, because it does not...

估计肿瘤和正常器官中的停留时间是放射免疫治疗（RIT）治疗计划的重要组成部分。这种估计通常使用共轭视图全身扫描时间序列和平面处理来完成。与三维成像方法（如单光子发射计算机断层扫描（SPECT））相比，该方法在后勤和成本方面具有优势，但由于它不...

Ultrasound (US) is among the most popular diagnostic techniques today. It is non-invasive, fast, comparably cheap, and does not require ionizing radiation. US is commonly used to examine the size, and structure of the thyroid gland. In clinical routine, thyroid imaging is usually performed by means of 2-D US. Conventional approaches for measuring the volume of the thyroid gland or its nodules may ...

超声（US）是当今最流行的诊断技术之一。它无创、快速、相对便宜，且不需要电离辐射。US常用于检查甲状腺的大小和结构。在临床常规中，甲状腺成像通常通过二维超声进行。传统测量甲状腺或其结节体积的方法可能...

This paper focuses on extracting and analyzing different spectral features from transrectal ultrasound (TRUS) images for prostate cancer recognition. First, the information about the images' frequency domain features and spatial domain features are combined using a Gabor filter and then integrated with the expert radiologist's information to identify the highly suspicious regions of interest (ROIs...

本文着重于从经直肠超声（TRUS）图像中提取和分析不同的频谱特征以识别前列腺癌。首先，利用Gabor滤波器将图像的频域特征和空间域特征信息相结合，然后与放射科专家的信息整合，以识别高度可疑的感兴趣区域（ROI...

An important problem of the analysis of functional magnetic resonance imaging (fMRI) experiments is to achieve some noise reduction of the data without blurring the shape of the activation areas. As a novel solution to this problem, recently the propagation–separation (PS) approach has been proposed. PS is a structure adaptive smoothing method that adapts to different shapes of activation areas. I...

功能性磁共振成像（fMRI）实验分析的一个重要问题是在不模糊激活区域形状的前提下实现数据的降噪。作为解决该问题的新方案，最近提出了传播-分离（PS）方法。PS是一种结构自适应平滑方法，能够适应不同形状的激活区域。...

Variation in computed tomography (CT) image grayscale and spatial geometry due to specimen orientation, magnification, voxel size, differences in X-ray photon energy and limited field-of-view during the scan, were evaluated in repeated micro-CT scans of iliac crest biopsies and test phantoms. Using the micro-CT scanner on beamline X2B at the Brookhaven National Laboratory's National Synchrotron Li...

由于标本方向、放大率、体素大小、X射线光子能量差异以及扫描过程中视野有限等因素导致的计算机断层扫描（CT）图像灰度和空间几何的变化，在髂嵴活检和测试体模的重复显微CT扫描中进行了评估。使用布鲁克海文国家实验室国家同步辐射光源X2B光束线上的显微CT扫描仪...

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