Volume 16, Issue 3

The authors propose a modification of Wells et al. (ibid., vol. 15, no. 4, p. 429-42, 1996) technique for bias field estimation and segmentation of magnetic resonance (MR) images. They show that replacing the class other, which includes all tissue not modeled explicitly by Gaussians with small variance, by a uniform probability density, and amending the expectation-maximization (EM) algorithm appropriately, gives significantly better results. The authors next consider the estimation and filtering of high-frequency information in MR images, comprising noise, intertissue boundaries, and within tissue microstructures. The authors conclude that post-filtering is preferable to the prefiltering that has been proposed previously. The authors observe that the performance of any segmentation algorithm, in particular that of Wells et al. (and the authors' refinements of it) is affected substantially by the number and selection of the tissue classes that are modeled explicitly, the corresponding defining parameters and, critically, the spatial distribution of tissues in the image. The authors present an initial exploration to choose automatically the number of classes and the associated parameters that give the best output. This requires the authors to define what is meant by "best output" and for this they propose the application of minimum entropy. The methods developed have been implemented and are illustrated throughout on simulated and real data (brain and breast MR).

作者提出了对Wells等人（同上，第15卷，第4期，第429-42页，1996年）用于磁共振（MR）图像偏置场估计和分割技术的改进。他们表明，将包括所有未用小方差高斯显式建模的组织的“其他”类别替换为均匀概率密度，并适当修改期望最大化（EM）算法，可以得到显著更好的结果。接下来，作者考虑了MR图像中高频信息的估计和滤波，包括噪声、组织间边界和组织内微结构。作者得出结论，后滤波优于先前提出的预滤波。作者观察到，任何分割算法的性能，特别是Wells等人（以及作者的改进）的性能，在很大程度上受到显式建模的组织类别的数量和选择、相应的定义参数以及关键地，图像中组织的空间分布的影响。作者进行了初步探索，以自动选择能给出最佳输出的类别数量和相关参数。这要求作者定义“最佳输出”的含义，为此他们提出了应用最小熵。所开发的方法已在模拟和真实数据（脑和乳腺MR）上实现并加以说明。

Many image matching schemes are based on mapping coordinate locations, such as the locations of landmarks, in one image to corresponding locations in a second image. A new approach to this mapping (coordinate transformation), called the elastic body spline (EBS), is described. The spline is based on a physical model of a homogeneous, isotropic three-dimensional (3-D) elastic body. The model can ap...

许多图像匹配方案基于将一个图像中的坐标位置（如地标位置）映射到第二个图像中的对应位置。本文描述了一种新的映射方法（坐标变换），称为弹性体样条（EBS）。该样条基于均匀、各向同性三维弹性体的物理模型。该模型可以...

The authors describe a new approach to imaging neural current sources from measurements of the magnetoencephalogram (MEG) associated with sensory, motor, or cognitive brain activation. Many previous approaches to this problem have concentrated on the use of weighted minimum norm (WMN) inverse methods. While these methods ensure a unique solution, they do not introduce information specific to the M...

作者描述了一种从与感觉、运动或认知脑激活相关的脑磁图（MEG）测量中成像神经电流源的新方法。许多先前的方法都集中在使用加权最小范数（WMN）逆方法。虽然这些方法确保了唯一解，但它们没有引入M...

A number of digital imaging techniques in medicine require the combination of multiple images. Using these techniques, it is essential that the images be adequately aligned and registered prior to addition, subtraction, or any other combination of the images. This paper describes an alignment routine developed to register an image of a fixed object containing a global offset error, rotation error,...

许多医学数字成像技术需要将多个图像进行组合。在使用这些技术时，必须在图像相加、相减或任何其他组合之前，对图像进行充分的对齐和配准。本文描述了一种用于配准固定物体图像的对齐程序，该图像包含全局偏移误差、旋转误差等。

Receiver operating characteristic (ROC) analysis is an established method of measuring diagnostic performance in medical imaging studies. Traditionally, artificial neural networks (ANN's) have been applied as a classifier to find one "best" detection rate. Recently researchers have begun to report ROC curve results for ANN classifiers. The current standard method of generating ROC curves for an AN...

接收者操作特征（ROC）分析是衡量医学影像研究诊断性能的成熟方法。传统上，人工神经网络（ANN）被用作分类器来找到一种“最佳”检测率。最近研究人员开始报告ANN分类器的ROC曲线结果。目前为ANN生成ROC曲线的标准方法是...

An approach for tracking and quantifying the nonrigid, nonuniform motion of the left ventricular (LV) endocardial wall from two-dimensional (2-D) cardiac image sequences, on a point-by-point basis over the entire cardiac cycle, is presented. Given a set of boundaries, motion computation involves first matching local segments on one contour to segments on the next contour in the sequence using a sh...

提出了一种在整个心动周期中逐点追踪和量化左心室心内膜壁非刚性、非均匀运动的方法，该方法基于二维心脏图像序列。给定一组边界，运动计算首先涉及使用形状匹配将一个轮廓上的局部段与序列中下一个轮廓上的段进行匹配。

Lossless compression techniques are essential in archival and communication of medical images. Here, a new segmentation-based lossless image coding (SLIC) method is proposed, which is based on a simple but efficient region growing procedure. The embedded region growing procedure produces an adaptive scanning pattern for the image with the help of a very-few-bits-needed discontinuity index map. Alo...

无损压缩技术对于医学图像的存档和通信至关重要。本文提出了一种新的基于分割的无损图像编码（SLIC）方法，该方法基于一个简单但高效的区域生长过程。嵌入的区域生长过程借助一个只需极少比特的不连续性指标图，为图像生成自适应扫描模式。

We developed an objective and quantitative method of mapping the human visual field with positron emission tomography (PET) and magnetic resonance imaging (MRI). The regional cerebral blood flow (rCBF) images were acquired with H/sub 2//sup 15/O-PET under visual fixation as well as under visual stimulation with flickering diodes arranged along the ring at 0/spl deg/, 3/spl deg/, 7/spl deg/, 14/spl...

我们开发了一种利用正电子发射断层扫描（PET）和磁共振成像（MRI）对人视野进行客观定量映射的方法。在视觉固定以及沿0°、3°、7°、14°...环排列的闪烁二极管视觉刺激下，使用H2^15O-PET获取局部脑血流（rCBF）图像。

Methods for optimizing the acquisition, reconstruction and analysis of positron emission tomography (PET) images for functional brain mapping have been investigated. The scatter fraction and noise-equivalent count rate characteristics were measured for the ECAT 951/31R PET scanner operating in septa-extended two-dimensional (2-D) and septa-retracted three-dimensional (3-D) modes. The 3-D mode is s...

用于脑功能映射的正电子发射断层扫描（PET）图像的采集、重建和分析优化方法已得到研究。在隔片伸出二维（2-D）和隔片收回三维（3-D）模式下，测量了ECAT 951/31R PET扫描仪的散射分数和噪声等效计数率特性。3-D模式是...

This paper addresses the implementation of image processing and computer vision techniques to automate tracer flow extraction in images obtained by the photochromic dye technique. This task is important in modeled arterial blood flow studies. Currently, it is performed via manual application of B-spline curve fitting. However, this is a tedious and error-prone procedure and its results are nonrepr...

本文探讨了图像处理和计算机视觉技术在光致变色染料技术获取的图像中自动提取示踪剂流动的实现。该任务在模拟动脉血流研究中具有重要意义。目前，该过程通过手动应用B样条曲线拟合来完成。然而，这是一种繁琐且易出错的过程，其结果不具重现性。

Myocardial blood flow (rMBF) can be measured using dynamic positron emission tomography (PET) and bolus injection of H/sub 2//sup 15/O. Recent studies indicate that large errors in the estimates of flow (f/spl circ/) can be produced by time shifts between the true arterial input function and the measured input function [A(t)]. We have investigated this phenomenon further using A(t) derived from pa...

心肌血流量（rMBF）可通过动态正电子发射断层扫描（PET）和推注H₂¹⁵O进行测量。最近的研究表明，真实动脉输入函数与测量输入函数[A(t)]之间的时间偏移可能导致流量估计（f̂）出现较大误差。我们使用从pa...导出的A(t)进一步研究了这一现象。

This paper investigates the problem of providing suitable interpolation for scanline algorithms. These algorithms are of interest, as they are parallelizable. A structure for analyzing the problem is given. The theory in regard to resampling is developed in the context of a scanline algorithm for image rotation. The theory is compared to results arrived at in practice. Alternative interpolation sc...

本文研究了为扫描线算法提供合适插值的问题。这些算法由于可并行化而受到关注。给出了分析该问题的结构。重采样理论是在图像旋转的扫描线算法背景下发展的。将该理论与实践中得到的结果进行了比较。替代插值方案...