Volume 24, Issue 6

Reconstruction of magnetic resonance images from data not falling on a Cartesian grid is a Fourier inversion problem typically solved using convolution interpolation, also known as gridding. Gridding is simple and robust and has parameters, the grid oversampling ratio and the kernel width, that can be used to trade accuracy for computational memory and time reductions. We have found that significant reductions in computation memory and time can be obtained while maintaining high accuracy by using a minimal oversampling ratio, from 1.125 to 1.375, instead of the typically employed grid oversampling ratio of two. When using a minimal oversampling ratio, appropriate design of the convolution kernel is important for maintaining high accuracy. We derive a simple equation for choosing the optimal Kaiser-Bessel convolution kernel for a given oversampling ratio and kernel width. As well, we evaluate the effect of presampling the kernel, a common technique used to reduce the computation time, and find that using linear interpolation between samples adds negligible error with far less samples than is necessary with nearest-neighbor interpolation. We also develop a new method for choosing the optimal presampled kernel. Using a minimal oversampling ratio and presampled kernel, we are able to perform a three-dimensional (3-D) reconstruction in one-eighth the time and requiring one-third the computer memory versus using an oversampling ratio of two and a Kaiser-Bessel convolution kernel, while maintaining the same level of accuracy.

从非笛卡尔网格上的数据重建磁共振图像是一个傅里叶逆问题，通常使用卷积插值（也称为网格化）来解决。网格化方法简单且鲁棒，其参数包括网格过采样比和核宽度，可用于在计算内存和时间之间权衡精度。我们发现，通过使用最小过采样比（1.125至1.375）而非通常采用的2，可以在保持高精度的同时大幅减少计算内存和时间。使用最小过采样比时，卷积核的恰当设计对保持高精度至关重要。我们推导了一个简单方程，用于在给定过采样比和核宽度的情况下选择最优的Kaiser-Bessel卷积核。此外，我们评估了预采样核（一种常用的减少计算时间的技术）的效果，发现使用线性插值在样本间进行插值比最近邻插值所需的样本数少得多，且引入的误差可忽略。我们还开发了一种选择最优预采样核的新方法。使用最小过采样比和预采样核，我们能够在八分之一的时间内完成三维重建，且所需计算机内存仅为使用过采样比为2和Kaiser-Bessel卷积核时的三分之一，同时保持相同的精度水平。

In this paper, we propose a combination of mean-shift-based tracking processes to establish migrating cell trajectories through in vitro phase-contrast video microscopy. After a recapitulation on how the mean-shift algorithm permits efficient object tracking we describe the proposed extension and apply it to the in vitro cell tracking problem. In this application, the cells are unmarked (i.e., no ...

本文提出了一种基于均值漂移的跟踪过程组合，以通过体外相差视频显微镜建立迁移细胞轨迹。在回顾了均值漂移算法如何实现高效目标跟踪之后，我们描述了所提出的扩展并将其应用于体外细胞跟踪问题。在该应用中，细胞未标记（即，无...）

A novel technique for despeckling the medical ultrasound images using lossy compression is presented. The logarithm of the input image is first transformed to the multiscale wavelet domain. It is then shown that the subband coefficients of the log-transformed ultrasound image can be successfully modeled using the generalized Laplacian distribution. Based on this modeling, a simple adaptation of th...

提出了一种利用有损压缩对医学超声图像进行去斑的新技术。首先将输入图像的对数变换到多尺度小波域。然后证明，对数变换后的超声图像的子带系数可以用广义拉普拉斯分布成功建模。基于此模型，提出了一种简单的自适应阈值方法，用于压缩子带系数，从而在去除斑点噪声的同时保留边缘。实验结果表明，该技术优于现有的去斑方法。

This paper reports a novel method to track brain shift using a laser-range scanner (LRS) and nonrigid registration techniques. The LRS used in this paper is capable of generating textured point-clouds describing the surface geometry/intensity pattern of the brain as presented during cranial surgery. Using serial LRS acquisitions of the brain's surface and two-dimensional (2-D) nonrigid image regis...

本文报告了一种使用激光测距扫描仪（LRS）和非刚性配准技术追踪脑移位的新方法。本文使用的LRS能够生成描述颅脑手术中脑表面几何形状/强度模式的纹理点云。通过连续获取脑表面的LRS图像并进行二维（2-D）非刚性图像配准...

In this paper, we present a two-stage algorithm for mammogram registration, the geometrical alignment of mammogram sequences. The rationale behind this paper stems from the intrinsic difficulties in comparing mammogram sequences. Mammogram comparison is a valuable tool in national breast screening programs as well as in frequent monitoring and hormone replacement therapy (HRT). The method presente...

本文提出了一种用于乳腺X线摄影配准的两阶段算法，即乳腺X线摄影序列的几何对齐。本文的基本原理源于比较乳腺X线摄影序列的内在困难。乳腺X线摄影比较在国家乳腺筛查计划以及频繁监测和激素替代疗法（HRT）中是一种有价值的工具。所提出的方法...

We present the development and validation of an image based speckle tracking methodology, for determining temporal two-dimensional (2-D) axial and lateral displacement and strain fields from ultrasound video streams. We refine a multiple scale region matching approach incorporating novel solutions to known speckle tracking problems. Key contributions include automatic similarity measure selection ...

我们提出并验证了一种基于图像的斑点跟踪方法，用于从超声视频流中确定时间二维（2D）轴向和侧向位移及应变场。我们改进了多尺度区域匹配方法，结合了针对已知斑点跟踪问题的新解决方案。关键贡献包括自动相似性度量选择，以及对跟踪窗口大小和形状的自适应调整，以提高在存在组织运动、衰减和噪声情况下的跟踪精度。该方法在模拟和实验超声数据上进行了验证，证明了其在高应变和噪声环境下优于传统方法的性能。

A new scheme for denoising magnetic resonance spectroscopy (MRS) signals is presented. This scheme is based on projecting noisy MRS signals in different domains, consecutively, and performing noise filtering operations in these domains. The domains are chosen such that the noise portion, which is inseparable from the desired signal in one domain, is separable in the other. A set of stable, linear,...

提出了一种用于磁共振波谱（MRS）信号去噪的新方案。该方案基于将噪声MRS信号连续投影到不同域中，并在这些域中执行噪声滤波操作。选择这些域使得在一个域中与期望信号不可分离的噪声部分在另一个域中是可分离的。一组稳定的、线性的...

This paper presents a new three-dimensional (3-D) wavelet-based scalable lossless coding scheme for compression of volumetric medical images. Aiming to improve the productivity of radiologists and the cost-effectiveness of the system, we strive to achieve high decoder throughput, random access to coded data volume, progressive transmission, and high compression ratio in a balanced design approach....

本文提出了一种新的基于三维小波的可扩展无损编码方案，用于压缩体积医学图像。为了提高放射科医生的生产力和系统的成本效益，我们力求在平衡的设计方法中实现高解码器吞吐量、对编码数据体的随机访问、渐进传输和高压缩比。

Thermoacoustic tomography (TAT) is an emerging imaging technique with potential for a wide range of biomedical imaging applications. In this correspondence, we propose an infinite family of weighted expectation maximization (EM) algorithms for reconstruction of images from temporally truncated TAT measurement data. The weighted EM algorithms are equivalent mathematically to the conventional EM alg...

热声断层扫描（TAT）是一种新兴的成像技术，具有广泛的生物医学成像应用潜力。在这篇论文中，我们提出了一类无限族的加权期望最大化（EM）算法，用于从时间截断的TAT测量数据中重建图像。加权EM算法在数学上等价于传统的EM算法...

Spatial independent component analysis (ICA) was used to study the temporal stationarity and spatial consistency of structured functional MRI (fMRI) noise. Spatial correlations have been used in the past to generate filters for the removal of structured noise for each time-course in an fMRI dataset. It would be beneficial to produce a multivariate filter based on the same principles. ICA is examin...

空间独立成分分析（ICA）被用于研究结构功能性磁共振成像（fMRI）噪声的时间平稳性和空间一致性。过去，空间相关性已被用于生成滤波器，以去除fMRI数据集中每个时间序列的结构噪声。基于相同原理生成多变量滤波器将是有益的。ICA正在检验...

The human cerebral cortex is a laminar structure about 3 mm thick, and is easily visualized with current magnetic resonance (MR) technology. The thickness of the cortex varies locally by region, and is likely to be influenced by such factors as development, disease and aging. Thus, accurate measurements of local cortical thickness are likely to be of interest to other researchers. We develop a par...

人类大脑皮层是一个约3毫米厚的分层结构，当前磁共振（MR）技术可以轻松可视化。皮层的厚度因区域而异，可能受到发育、疾病和衰老等因素的影响。因此，局部皮层厚度的精确测量可能对其他研究人员具有重要意义。我们开发了一个参数...

This paper presents a new magnetic resonance imaging (MRI) phase correction method. The linear phase correction method using autocorrelation proposed by Ahn and Cho (AC method) is extended to handle nonlinear terms, which are often important for polynomial expansion of phase variation in MRI. The polynomial coefficients are statistically determined from a cascade series of n-pixel-shift rotational...

本文提出了一种新的磁共振成像（MRI）相位校正方法。将Ahn和Cho提出的利用自相关的线性相位校正方法（AC方法）扩展到处理非线性项，这些项在MRI相位变化的多项式展开中通常很重要。多项式系数通过n像素移位旋转的级联系列统计确定...

Provides a listing of current staff, committee members and society officers.

提供当前工作人员、委员会成员和学会官员的列表。

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

介绍本期期刊的目录。

Describes the above-named upcoming conference event. May include topics to be covered or calls for papers.

描述上述即将举行的会议活动。可能包括涵盖的主题或征稿通知。

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提供对从业者和研究人员感兴趣的即将举行的会议活动的通知。

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

为准作者提供提交稿件的说明和指南。

Provides notice of upcoming special issue(s) of interest to practitioners and researchers.

为从业人员和研究人员提供即将出版的特刊通知。