Volume 28, Issue 1

In clinical magnetic resonance imaging (MRI), any reduction in scan time offers a number of potential benefits ranging from high-temporal-rate observation of physiological processes to improvements in patient comfort. Following recent developments in compressive sensing (CS) theory, several authors have demonstrated that certain classes of MR images which possess sparse representations in some transform domain can be accurately reconstructed from very highly undersampled K -space data by solving a convex lscr 1 -minimization problem. Although lscr 1 -based techniques are extremely powerful, they inherently require a degree of over-sampling above the theoretical minimum sampling rate to guarantee that exact reconstruction can be achieved. In this paper, we propose a generalization of the CS paradigm based on homotopic approximation of the lscr 0 quasi-norm and show how MR image reconstruction can be pushed even further below the Nyquist limit and significantly closer to the theoretical bound. Following a brief review of standard CS methods and the developed theoretical extensions, several example MRI reconstructions from highly undersampled K -space data are presented.

在临床磁共振成像（MRI）中，扫描时间的任何减少都能带来诸多潜在好处，从高时间速率观察生理过程到提高患者舒适度。随着压缩感知（CS）理论的最新发展，多位作者已经证明，通过求解一个凸的ℓ1最小化问题，可以从高度欠采样的K空间数据中准确重建出在某些变换域中具有稀疏表示的特定类别的MR图像。尽管基于ℓ1的技术非常强大，但它们本质上需要高于理论最小采样率的过采样程度，以确保能够实现精确重建。在本文中，我们提出了一种基于ℓ0拟范数同伦近似的CS范式的推广，并展示了如何将MR图像重建进一步推至奈奎斯特极限以下，并显著接近理论界限。在简要回顾标准CS方法和所发展的理论扩展之后，我们展示了几个从高度欠采样的K空间数据进行MRI重建的示例。

Bone age rating is associated with a considerable variability from the human interpretation, and this is the motivation for presenting a new method for automated determination of bone age (skeletal maturity). The method, called BoneXpert, reconstructs, from radiographs of the hand, the borders of 15 bones automatically and then computes ldquointrinsicrdquo bone ages for each of 13 bones (radius, ulna, and 11 short bones). Finally, it transforms the intrinsic bone ages into Greulich Pyle (GP) or Tanner Whitehouse (TW) bone age. The bone reconstruction method automatically rejects images with abnormal bone morphology or very poor image quality. From the methodological point of view, BoneXpert contains the following innovations: 1) a generative model (active appearance model) for the bone reconstruction; 2) the prediction of bone age from shape, intensity, and texture scores derived from principal component analysis; 3) the consensus bone age concept that defines bone age of each bone as the best estimate of the bone age of the other bones in the hand; 4) a common bone age model for males and females; and 5) the unified modelling of TW and GP bone age. BoneXpert is developed on 1559 images. It is validated on the Greulich Pyle atlas in the age range 2-17 years yielding an SD of 0.42 years [0.37; 0.47] 95% conf, and on 84 clinical TW-rated images yielding an SD of 0.80 years [0.68; 0.93] 95% conf. The precision of the GP bone age determination (its ability to yield the same result on a repeated radiograph) is inferred under suitable assumptions from six longitudinal series of radiographs. The result is an SD on a single determination of 0.17 years [0.13; 0.21] 95% conf.

骨龄评分与人类解释存在相当大的变异性，这促使我们提出一种新的自动确定骨龄（骨骼成熟度）的方法。该方法称为BoneXpert，从手部X光片自动重建15块骨的边界，然后计算13块骨（桡骨、u...）的“内在”骨龄。

We report new progress in developing the instrument and software platform of a combined X-ray mammography/diffuse optical breast imaging system. Particularly, we focus on system validation using a series of balloon phantom experiments and the optical image analysis of 49 healthy patients. Using the finite-element method for forward modeling and a regularized Gauss-Newton method for parameter recon...

我们报告了在开发联合X射线乳腺X线摄影/扩散光学乳腺成像系统的仪器和软件平台方面的新进展。特别地，我们专注于使用一系列气球体模实验和49名健康患者的光学图像分析进行系统验证。使用有限元方法进行正向建模，并使用正则化高斯-牛顿方法进行参数重构。

Rheumatoid arthritis (RA) is a chronic disease that affects and potentially destroys the joints of the appendicular skeleton. The precise and reproducible quantification of the progression of joint space narrowing and the erosive bone destructions caused by RA is crucial during treatment and in imaging biomarkers in clinical trials. Current manual scoring methods exhibit high interreader variabili...

类风湿关节炎（RA）是一种慢性疾病，影响并可能破坏四肢骨骼的关节。精确且可重复地量化RA引起的关节间隙狭窄进展和侵蚀性骨破坏，在治疗过程中以及临床试验中的影像生物标志物中至关重要。当前的手动评分方法存在较高的读者间变异...

A major disadvantage of magnetic resonance imaging (MRI) compared to other imaging modalities like computed tomography is the fact that its intensities are not standardized. Our contribution is a novel method for MRI signal intensity standardization of arbitrary MRI scans, so as to create a pulse sequence dependent standard intensity scale. The proposed method is the first approach that uses the p...

与其他成像方式（如计算机断层扫描）相比，磁共振成像的一个主要缺点是强度值未标准化。我们的贡献是一种新颖的方法，用于对任意MRI扫描进行信号强度标准化，以建立脉冲序列依赖的标准强度标度。所提出的方法是第一个使用...

The purpose of this research was to demonstrate the feasibility of a computerized auto-assessment method in which a computer-aided diagnosis (CADx) system itself provides a level of confidence for its estimate for the probability of malignancy for each radiologist-identified lesion. The computer performance was assessed within a leave-one-case-out protocol using a database of sonographic images fr...

本研究旨在证明计算机自动评估方法的可行性，该方法中计算机辅助诊断（CADx）系统自身为其对每位放射科医生识别的病灶的恶性概率估计提供置信水平。使用超声图像数据库在留一法交叉验证方案中评估计算机性能...

A new filter to restore radiographic images corrupted by impulsive noise is proposed. It is based on a switching scheme where all the pulses are first detected and then corrected through a median filter. The pulse detector is based on the hypothesis that the major contribution to image noise is given by the photon counting process, with some pixels corrupted by impulsive noise. Such statistics is ...

提出了一种新的滤波器，用于恢复被脉冲噪声破坏的放射摄影图像。该滤波器基于一种切换方案，首先检测所有脉冲，然后通过中值滤波器进行校正。脉冲检测器基于这样一个假设：图像噪声的主要贡献来自光子计数过程，部分像素受到脉冲噪声污染。这样的统计特性...

The polymeric implant material poly(lactide-co-glycolide) (PLGA) degrades by a process of bulk degradation, which allows it to be used for the controlled release of therapeutic molecules from implants and microspheres. The temporal characterization of PLGA microsphere degradation has been limited by the need to destructively monitor the samples at each time point. In this study, a noninvasive imag...

聚合物植入材料聚乳酸-羟基乙酸共聚物（PLGA）通过本体降解过程降解，使其可用于从植入物和微球中控制释放治疗分子。PLGA微球降解的时间表征一直受到需要在每个时间点破坏性监测样品的限制。在本研究中，一种非侵入性成像...

For positron emission tomography (PET) imaging, different reconstruction methods can be applied, including maximum likelihood (ML ) and maximum a posteriori (MAP) reconstruction. Postsmoothed ML images have approximately position and object independent spatial resolution, which is advantageous for (semi-) quantitative analysis. However, the complex object dependent smoothing obtained with MAP migh...

对于正电子发射断层成像（PET），可以应用不同的重建方法，包括最大似然（ML）和最大后验（MAP）重建。后平滑ML图像具有近似位置和对象无关的空间分辨率，这有利于（半）定量分析。然而，MAP获得的复杂对象依赖平滑可能...

The centerlines of tubular structures are useful for medical image visualization and computer-aided diagnosis applications. They can be effectively extracted by using a thinning algorithm that erodes an object layer by layer until only a skeleton is left. An object point is ldquosimplerdquo and can be safely deleted only if the resultant image is topologically equivalent to the original. Numerous ...

管状结构的中心线对于医学图像可视化和计算机辅助诊断应用非常有用。它们可以通过使用细化算法有效提取，该算法逐层侵蚀对象，直到只剩下骨架。只有当结果图像在拓扑上等价于原始图像时，对象点才是“简单的”，可以安全删除。众多……

Automated interpretation of complex images requires elaborate knowledge and model-based image analysis, but often needs interaction with an expert as well. This research describes expert interaction with a multiagent image interpretation system using only a restricted vocabulary of high-level user interactions. The aim is to minimize inter- and intra-observer variability by keeping the total numbe...

复杂图像的自动解释需要专业知识和基于模型的图像分析，但通常也需要与专家进行交互。本研究描述了专家与多智能体图像解释系统的交互，仅使用有限的高层用户交互词汇。其目的是通过保持总交互次数最少来最小化观察者间和观察者内的变异性。

Multicolor fluorescence in situ hybridization (M-FISH) techniques provide color karyotyping that allows simultaneous analysis of numerical and structural abnormalities of whole human chromosomes. Chromosomes are stained combinatorially in M-FISH. By analyzing the intensity combinations of each pixel, all chromosome pixels in an image are classified. Due to the overlap of excitation and emission sp...

多色荧光原位杂交（M-FISH）技术提供彩色核型分析，可以同时分析整个人类染色体的数量和结构异常。在M-FISH中，染色体被组合染色。通过分析每个像素的强度组合，图像中的所有染色体像素被分类。由于激发和发射光谱的重叠...

An algorithm was developed for the 2-D reconstruction of truncated and nontruncated uniformly attenuated data acquired from single photon emission computed tomography (SPECT). The algorithm is able to reconstruct data from half-scan (180$^{\circ}$ ) and short-scan (180$^{\circ}$ +fan angle) acquisitions for parallel- and fan-beam geometries, respectively, as well as data from full-scan (360 $^{\ci...

开发了一种用于从单光子发射计算机断层扫描（SPECT）采集的截断和非截断均匀衰减数据的二维重建算法。该算法能够分别从平行束和扇束几何的半扫描（180°）和短扫描（180°+扇角）采集数据，以及全扫描（360°）采集数据中进行重建。

A postprocessing technique is proposed for the correction of both translational and rotational motion artifacts in magnetic resonance imaging (MRI). The method consists of two steps: 1) k-space extrapolation to generate a motion-free reference, followed by 2) correlation with actual data to estimate motion. In this paper, two different extrapolation methods were investigated for the purpose of mot...

提出了一种后处理技术，用于校正磁共振成像（MRI）中的平移和旋转运动伪影。该方法包括两个步骤：1）k空间外推以生成无运动参考，然后2）与实际数据相关以估计运动。本文研究了两种不同的外推方法，用于...

Provides a listing of current committee members and society officers.

提供当前委员会成员和学会官员的列表。

Provides instructions and guidelines to prospective authors who wish to submit manuscripts.

为希望提交手稿的潜在作者提供指导和建议。

Presents the table of contents for this issue of the periodical.

提供本期期刊的目录。