Volume 26, Issue 3

Medical image acquisition devices provide a vast amount of anatomical and functional information, which facilitate and improve diagnosis and patient treatment, especially when supported by modern quantitative image analysis methods. However, modality specific image artifacts, such as the phenomena of intensity inhomogeneity in magnetic resonance images (MRI), are still prominent and can adversely affect quantitative image analysis. In this paper, numerous methods that have been developed to reduce or eliminate intensity inhomogeneities in MRI are reviewed. First, the methods are classified according to the inhomogeneity correction strategy. Next, different qualitative and quantitative evaluation approaches are reviewed. Third, 60 relevant publications are categorized according to several features and analyzed so as to reveal major trends, popularity, evaluation strategies and applications. Finally, key evaluation issues and future development of the inhomogeneity correction field, supported by the results of the analysis, are discussed.

医学图像采集设备提供了大量的解剖和功能信息，这些信息在定量图像分析方法的支持下，便利并改善了诊断和患者治疗。然而，特定模态的图像伪影，例如磁共振图像（MRI）中的强度不均匀性现象，仍然显著，并可能对定量图像分析产生不利影响。本文回顾了已开发的众多用于减少或消除MRI强度不均匀性的方法。首先，根据不均匀性校正策略对方法进行分类。其次，回顾了不同的定性和定量评估方法。第三，根据若干特征对60篇相关出版物进行分类和分析，以揭示主要趋势、流行程度、评估策略和应用。最后，在分析结果的支持下，讨论了不均匀性校正领域的关键评估问题和未来发展。

The measurement of the brachial artery diameter is frequently used in clinical studies for evaluating the flow-mediated dilation and, in conjunction with the blood pressure value, for assessing arterial stiffness. This paper presents a system for computing the brachial artery diameter in real-time by analyzing B-mode ultrasound images. The method is based on a robust edge detection algorithm which...

肱动脉直径的测量常用于临床研究中评估血流介导的扩张，并联合血压值评估动脉僵硬度。本文提出了一种通过分析B型超声图像实时计算肱动脉直径的系统。该方法基于稳健的边缘检测算法，...

A family of alternating minimization algorithms for finding maximum-likelihood estimates of attenuation functions in transmission X-ray tomography is described. The model from which the algorithms are derived includes polyenergetic photon spectra, background events, and nonideal point spread functions. The maximum-likelihood image reconstruction problem is reformulated as a double minimization of ...

描述了一系列用于在透射X射线断层成像中寻找衰减函数极大似然估计的交替最小化算法。推导这些算法的模型包括多能光子谱、背景事件和非理想点扩展函数。将极大似然图像重建问题重新表述为双重最小化...

An approach to 3-D vessel axis tracking based on surface evolution is presented. The main idea is to guide the evolution of the surface by analyzing its skeleton topology during evolution, and imposing shape constraints on the topology. For example, the intermediate topology can be processed such that it represents a single vessel segment, a bifurcation, or a more complex vascular topology. The ev...

提出了一种基于表面演化的三维血管轴跟踪方法。主要思想是通过分析演化过程中表面的骨架拓扑结构，并施加形状约束来引导表面的演化。例如，中间拓扑可以被处理成代表单个血管段、分叉或更复杂的血管拓扑结构。该演...

To further improve pinhole single photon emission computed tomography (SPECT) imaging, there have been increasing interests in the use of nonstandard collimator designs and/or acquisition geometries. Homogeneous coordinates provide a compact and convenient framework to unify the geometric descriptions of the projection operators for these different imaging geometries, which may facilitate the impl...

为了进一步改进针孔单光子发射计算机断层扫描（SPECT）成像，人们对使用非标准准直器设计和/或采集几何的兴趣日益增加。齐次坐标提供了一个紧凑而方便的框架，可以统一这些不同成像几何的投影算子的几何描述，这可能有助于实现...

Spatial variations of the main field give rise to artifacts in magnetic resonance images if disregarded in reconstruction. With non-Cartesian k-space sampling, they often lead to unacceptable blurring. Data from such acquisitions are usually reconstructed with gridding methods and optionally restored with various correction methods. Both types of methods essentially face the same basic problem of ...

如果在重建过程中忽略主磁场的空间变化，会在磁共振图像中产生伪影。对于非笛卡尔k空间采样，这种变化通常会导致不可接受的模糊。来自此类采集的数据通常使用网格重建方法进行重建，并可选择使用各种校正方法进行恢复。两种方法本质上都面临相同的基本问题……

Accurate predictions of image variances can be useful for reconstruction algorithm analysis and for the design of regularization methods. Computing the predicted variance at every pixel using matrix-based approximations is impractical. Even most recently adopted methods that are based on local discrete Fourier approximations are impractical since they would require a forward and backprojection a...

准确预测图像方差对于重建算法分析和正则化方法设计非常有用。使用基于矩阵的近似计算每个像素的预测方差是不切实际的。即使最近采用的基于局部离散傅里叶近似的方法也不实用，因为它们需要前向和后向投影...

Coronary artery calcification (CAC) is quantified based on a computed tomography (CT) scan image. A calcified region is identified. Modified expectation maximization (MEM) of a statistical model for the calcified and background material is used to estimate the partial calcium content of the voxels. The algorithm limits the region over which MEM is performed. By using MEM, the statistical propertie...

基于计算机断层扫描（CT）图像对冠状动脉钙化（CAC）进行量化。识别钙化区域。采用改进的期望最大化（MEM）方法对钙化和背景材料的统计模型进行估计，以估算体素的部分钙含量。该算法限制了执行MEM的区域。通过使用MEM，统计特性...

A fast, robust, accurate, and automatic registration technique based on magnetic resonance (MR) active microcoils (active markers) for registration of tracked medical devices to preprocedural MR-images is presented. This allows for a straightforward integration of position measurement systems into clinical procedures. The presented method is useful for guidance purposes in clinical applications wi...

提出了一种基于磁共振（MR）主动微型线圈（主动标记）的快速、稳健、准确且自动的配准技术，用于将跟踪的医疗设备与术前MR图像进行配准。这使得位置测量系统能够直接集成到临床程序中。所提出的方法对于临床应用中的引导目的非常有用。

We have developed a nonparametric approach to the analysis of dynamic positron emission tomography (PET) data for extracting temporal characteristics of the change in endogenous neurotransmitter concentration in the brain. An algebraic method based on singular value decomposition (SVD) was applied to simulated data under both rest (neurotransmitter at baseline) and activated (transient neurotransm...

我们开发了一种非参数方法来分析动态正电子发射断层扫描（PET）数据，以提取大脑内源性神经递质浓度变化的时间特征。一种基于奇异值分解（SVD）的代数方法被应用于模拟数据，分别在静息（神经递质在基线）和激活（瞬态神经递质）状态下...

We introduce a family of fast algorithms for 2-D parallel-beam tomographic backprojection. They aggregate the projections in a hierarchical structure involving the shearing and addition of sparsely sampled images. The algorithms achieve a computational cost of O(N2 logP), when backprojecting an NtimesN pixel image from P projections. The algorithms provide a systematic means, guided by a Fourier-d...

我们介绍了一类用于二维平行束断层反投影的快速算法。它们通过一种涉及稀疏采样图像的剪切和相加的分层结构来聚合投影。当从P个投影反投影一个N×N像素的图像时，这些算法实现了O(N^2 log P)的计算成本。这些算法提供了一种系统的方法，在傅里叶变换的指导下...

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