Volume 16, Issue 5

Image segmentation is the partition of an image into a set of nonoverlapping regions whose union is the entire image. The image is decomposed into meaningful parts which are uniform with respect to certain characteristics, such as gray level or texture. In this paper, we propose a methodology for evaluating medical image segmentation algorithms wherein the only information available is boundaries outlined by multiple expert observers. In this case, the results of the segmentation algorithm can be evaluated against the multiple observers' outlines. We have derived statistics to enable us to find whether the computer-generated boundaries agree with the observers' hand-outlined boundaries as much as the different observers agree with each other. We illustrate the use of this methodology by evaluating image segmentation algorithms on two different applications in ultrasound imaging. In the first application, we attempt to find the epicardial and endocardial boundaries from cardiac ultrasound images, and in the second application, our goal is to find the fetal skull and abdomen boundaries from prenatal ultrasound images.

图像分割是将图像划分为一组非重叠区域，这些区域的并集构成整个图像。图像被分解为具有某些特性（如灰度或纹理）一致的有意义部分。在本文中，我们提出了一种评估医学图像分割算法的方法，其中唯一可用的信息是由多位专家观察者勾画的边界。在这种情况下，分割算法的结果可以与多位观察者的勾画进行对比评估。我们推导了统计量，以判断计算机生成的边界与观察者手绘边界的一致性是否达到不同观察者之间的一致性水平。我们通过评估两种不同超声成像应用中的图像分割算法来说明该方法的使用。在第一个应用中，我们尝试从心脏超声图像中寻找心外膜和心内膜边界；在第二个应用中，我们的目标是从产前超声图像中寻找胎儿颅骨和腹部边界。

We propose the boundary shift integral (BSI) as a measure of cerebral volume changes derived from registered repeat three-dimensional (3-D) magnetic resonance (MR) [3D MR] scans. The BSI determines the total volume through which the boundaries of a given cerebral structure have moved and, hence, the volume change, directly from voxel intensities. We found brain and ventricular BSI's correlated tig...

我们提出边界位移积分（BSI）作为一种从配准重复三维磁共振（3D MR）扫描中得出的脑体积变化测量方法。BSI直接通过体素强度确定给定脑结构边界移动的总体积，从而得出体积变化。我们发现脑和脑室的BSI与...

Multiple sclerosis (MS) is a disease of the white matter. Magnetic resonance imaging (MRI) is proven to be a sensitive method of monitoring the progression of this disease and of its changes due to treatment protocols. Quantification of the severity of the disease through estimation of MS lesion volume via MR imaging is vital for understanding and monitoring the disease and its treatment. This pap...

多发性硬化（MS）是一种白质疾病。磁共振成像（MRI）已被证明是一种监测该疾病进展及其因治疗方案变化而改变的敏感方法。通过MRI估计MS病变体积来量化疾病严重程度对于理解和监测疾病及其治疗至关重要。本文...

Although current edge-following schemes can be very efficient in determining coronary boundaries, they may fail when the feature to be followed is disconnected (and the scheme is unable to bridge the discontinuity) or branch points exist where the best path to follow is indeterminate. Here, the authors present new deformable spline algorithms for determining vessel boundaries, and enhancing their centerline features. A bank of even and odd S-Gabor filter pairs of different orientations are convolved with vascular images in order to create an external snake energy field. Each fitter pair will give maximum response to the segment of vessel having the same orientation as the filters. The resulting responses across filters of different orientations are combined to create an external energy field for snake optimization. Vessels are represented by B-Spline snakes, and are optimized on filter outputs with dynamic programming. The points of minimal constriction and the percent-diameter stenosis are determined from a computed vessel centerline. The system has been statistically validated using fixed stenosis and flexible-tube phantoms. It has also been validated on 20 coronary lesions with two independent operators, and has been tested for interoperator and intraoperator variability and reproducibility. The system has been found to be specially robust in complex images involving vessel branchings and incomplete contrast filling.

尽管当前的边缘跟踪算法在确定冠状动脉边界时可以非常高效，但当要跟踪的特征不连续（且算法无法桥接不连续性）或存在分支点（最佳跟踪路径不确定）时，它们可能会失败。本文作者提出了新的可变形样条算法，用于确定血管边界并增强其...

This paper proposes an adaptive image enhancement method for mammographic images, which is based on the first derivative and the local statistics. The adaptive enhancement method consists of three processing steps. The first step is to remove the film artifacts which may be misread as microcalcifications. The second step is to compute the gradient images by using the first derivative operators. Th...

本文提出了一种基于一阶导数和局部统计的自适应乳腺X线图像增强方法。该自适应增强方法包括三个处理步骤。第一步是去除可能被误读为微钙化的胶片伪影。第二步是利用一阶导数算子计算梯度图像。

The current trend in attenuation correction for single photon emission computed tomography (SPECT) is to measure and reconstruct the attenuation coefficient map using a transmission scan, performed either sequentially or simultaneously with the emission scan. This approach requires dedicated hardware and increases the cost (and in some cases the scanning time) required to produce a clinical SPECT ...

当前单光子发射计算机断层扫描（SPECT）衰减校正的趋势是使用透射扫描测量和重建衰减系数图，该扫描可与发射扫描顺序或同时进行。这种方法需要专用硬件，并增加了临床SPECT...

Presents a new algorithm for the robust and accurate tracking of the aorta in cardiovascular magnetic resonance (MR) images. First, a rough estimate of the location and diameter of the aorta is obtained by applying a multiscale medial-response function using the available a priori knowledge. Then, this estimate is refined using an energy-minimizing deformable model which the authors define in a Ma...

提出一种新算法，用于在心血管磁共振（MR）图像中稳健准确地跟踪主动脉。首先，利用可用的先验知识，通过应用多尺度介质响应函数获得主动脉位置和直径的粗略估计。然后，使用作者定义的能量最小化可变形模型对该估计进行细化。

In recent years, many investigators have proposed Gibbs prior models to regularize images reconstructed from emission computed tomography data. Unfortunately, hyperparameters used to specify Gibbs priors can greatly influence the degree of regularity imposed by such priors and, as a result, numerous procedures have been proposed to estimate hyperparameter values, from observed image data. Many of ...

近年来，许多研究者提出使用吉布斯先验模型来正则化从发射计算机断层扫描数据重建的图像。不幸的是，用于指定吉布斯先验的超参数会极大影响这些先验所施加的正则化程度，因此，已提出许多从观测图像数据估计超参数值的方法。许多...

This paper outlines a simple, fast, and accurate method for automatically locating the nipple on digitized mammograms that have been segmented to reveal the skin-air interface. If the average gradient of the intensity is computed in the direction normal to the interface and directed inside the breast, it is found that there is a sudden and distinct change in this parameter close to the nipple. A n...

本文概述了一种简单、快速且准确的方法，用于在已分割以显示皮肤-空气界面的数字化乳腺X线照片上自动定位乳头。如果计算垂直于界面方向并指向乳房内部的平均强度梯度，就会发现该参数在乳头附近发生突然而明显的变化。一

A multiresolution statistical method for identifying clinically normal tissue in digitized mammograms is used to construct an algorithm for separating normal regions from potentially abnormal regions; that is, small regions that may contain isolated calcifications. This is the initial phase of the development of a general method for the automatic recognition of normal mammograms. The first step is...

一种用于识别数字化乳腺X线摄影中临床正常组织的多元统计方法，用于构建一种将正常区域与可能异常区域（即可能含有孤立钙化点的小区域）分离的算法。这是开发自动识别正常乳腺X线图像通用方法的初始阶段。第一步是...

This paper describes a new approach to reconstruction of the conductivity field in electrical impedance tomography. Our goal is to improve the tradeoff between the quality of the images and the numerical complexity of the reconstruction method. In order to reduce the computational load, we adopt a linearized approximation to the forward problem that describes the relationship between the unknown c...

本文描述了一种在电阻抗断层成像中重建电导率场的新方法。我们的目标是改善图像质量与重建方法数值复杂度之间的权衡。为了降低计算负荷，我们采用正向问题的线性化近似，描述未知电导率与测量数据之间的关系。

Presents the design of a positron emission tomograph (PET) with flexible geometry dedicated to in vivo studies of small animals (TierPET). The scanner uses two pairs of detectors. Each detector consists of 400 small individual yttrium aluminum perovskite (YAP) scintillator crystals of dimensions 2/spl times/2/spl times/15 mm/sup 3/, optically isolated and glued together, which are coupled to posit...

介绍一种用于小动物体内研究的柔性几何正电子发射断层扫描仪（TierPET）的设计。该扫描仪使用两对探测器。每个探测器由400个尺寸为2×2×15 mm³的小型钇铝钙钛矿（YAP）闪烁晶体组成，这些晶体光学隔离并粘合在一起，耦合到正电子...

Describes a method for identification of brain structures from MRI data sets. The bulk of the paper concerns an automatic system for finding the anterior and posterior commissures [(AC) and (PC)] in the midsagittal plane. These landmarks are key for the definition of the Talairach space, commonly used in stereotactic neurosurgery, in the definition of common coordinate systems for the pooling of f...

描述了一种从MRI数据集中识别脑结构的方法。论文主要涉及一个自动系统，用于在正中矢状面上寻找前连合和后连合。这些标志点对于定义Talairach空间至关重要，该空间常用于立体定向神经外科以及定义用于汇总数据的共同坐标系。

Electric currents are applied to body in numerous applications in medicine such as electrical impedance tomography, cardiac defibrillation, electrocautery, and physiotherapy. If the magnetic field within a region is measured, the currents generating these fields can be calculated using the curl operator. In this study, magnetic fields generated within a phantom by currents passing through an exter...

电流在医学中有许多应用，如电阻抗断层成像、心脏除颤、电灼和物理治疗。如果测量区域内的磁场，则可以利用旋度算子计算产生这些磁场的电流。在本研究中，通过外部电流在体模内产生的磁场...

Digital imaging fiber-optic transillumination (DIFOTI) is a novel method to detect and monitor dental caries, using light, a charge-coupled device (CCD) camera, and computer-controlled image acquisition. The advantages of DIFOTI over radiography include: no ionizing radiation, no film, real-time diagnosis, and higher sensitivity in detection of early lesions not apparent to X-ray, as demonstrated ...

数字成像光纤透照术（DIFOTI）是一种利用光、电荷耦合器件（CCD）相机和计算机控制图像采集来检测和监测龋齿的新方法。与放射照相相比，DIFOTI的优势包括：无电离辐射、无需胶片、实时诊断，以及对X射线不明显的早期病变具有更高的检测灵敏度，如...

As shown previously for two-dimensional geometries, anisotropy effects should not be ignored in electrical impedance tomography (EIT) and structural information is important for the reconstruction of anisotropic conductivities. Here, we describe the static reconstruction of an anisotropic conductivity distribution for the more realistic three-dimensional (3-D) case. Boundaries between different co...

正如先前针对二维几何结构所示，各向异性效应在电阻抗断层成像（EIT）中不应被忽视，结构信息对于重建各向异性电导率很重要。在此，我们描述了针对更逼真的三维（3-D）情况下的各向异性电导率分布的静态重建。不同区域之间的边界...

The recovery of a three-dimensional (3-D) model from a sequence of two-dimensional (2-D) images is very useful in medical image analysis. Image sequences obtained from the relative motion between the object and the camera or the scanner contain more 3-D information than a single image. Methods to visualize the computed tomograms can be divided into two approaches: the surface rendering approach an...

从一系列二维图像中恢复三维模型在医学图像分析中非常有用。通过物体与相机或扫描仪之间的相对运动获得的图像序列比单个图像包含更多的三维信息。可视化计算机断层扫描的方法可以分为两种：表面绘制方法和...

A range scanner is developed that can scan a gypsum dental cast and reconstruct the cast digitally for display and storage purposes. The scanner is based on subtractive light and computes the range values using optical triangulation. A fiducial marker is introduced that, when attached to a dental cast at the time of image acquisition, makes it possible to integrate multiview range images of the ca...

开发了一种范围扫描仪，可以扫描石膏牙模并数字重建用于显示和存储。该扫描仪基于减色光，利用光学三角测量计算距离值。引入了一个参考标记，在图像采集时附着在牙模上，使得能够整合牙模的多视角距离图像。

The method of constrained reconstruction, previously applied to magnetic resonance imaging (MRI), is extended to magnetic resonance spectroscopy. This method assumes a model for the MR signal. The model parameters are estimated directly from the phase encoded data. This process obviates the need for the fast Fourier transform (FFT) (which often exhibits limited resolution and ringing artifact). Th...

将先前应用于磁共振成像（MRI）的约束重建方法扩展至磁共振波谱学。该方法为MR信号建立模型，直接从相位编码数据估算模型参数。这一过程无需快速傅里叶变换（FFT）（FFT常显示有限的分辨率和振铃伪影）。

Fan-beam collimators with spatially varying focal lengths are used in single photon emission computed tomography (SPECT) to improve the imaging sensitivity and to reduce the reconstruction artifacts resulting from the truncation of projection data. An angular representation of the detector coordinates for the projection data is adopted to investigate several aspects of the reconstruction problem f...

扇束准直器具有空间变化焦距，用于单光子发射计算机断层扫描（SPECT），以提高成像灵敏度并减少投影数据截断导致的重建伪影。采用投影数据探测器坐标的角度表示来研究重建问题的几个方面...

The increase of low back problems has stimulated the development of different analysis and evaluation techniques. Among these methods, the direct linear transformation (DLT) technique is commonly used to reconstruct the spine in three dimensions by means of its known image coordinates on radiographs. Despite its efficiency and precision, general reconstruction of some standard anatomical landmarks...

腰椎问题的增加促进了不同分析和评估技术的发展。在这些方法中，直接线性变换（DLT）技术通常通过已知的X光片图像坐标来三维重建脊柱。尽管其高效且精确，但一些标准解剖标志的通用重建...

The duration of a positron emission tomography (PET) imaging scan can be reduced if the transmission scan of one patient which is used for emission correction can be synthesized by using the reference transmission scan of another patient. In this paper, we propose a new intersubjects PET emission scan registration method and PET transmission synthesis method by using the boundary information of th...

如果能够利用另一位患者的参考透射扫描来合成为发射校正所需的患者透射扫描，则可以缩短正电子发射断层扫描（PET）成像扫描的持续时间。在本文中，我们利用目标的边界信息，提出了一种新的跨患者PET发射扫描配准方法和PET透射合成方法。

In dynamic positron emission tomography (PET) data analysis, regions of interest (ROIs) are analyzed by fitting a parametric model to the time-activity curve acquired after a radio-labeled tracer has been introduced into the patient's bloodstream. This procedure can be carried out for multiple ROIs and/or multiple injections of the same or a different radiopharmaceutical. The approach presented he...

在动态正电子发射断层扫描（PET）数据分析中，通过将参数模型拟合到放射性标记示踪剂引入患者血流后获取的时间-活性曲线，分析感兴趣区域（ROI）。该过程可对多个ROI和/或多次注射相同或不同放射性药物进行。提出的方法...