Volume 19, Issue 3

Describes an automated method to locate and outline blood vessels in images of the ocular fundus. Such a tool should prove useful to eye care specialists for purposes of patient screening, treatment evaluation, and clinical study. The authors' method differs from previously known methods in that it uses local and global vessel features cooperatively to segment the vessel network. The authors evaluate their method using hand-labeled ground truth segmentations of 20 images. A plot of the operating characteristic shows that the authors' method reduces false positives by as much as 15 times over basic thresholding of a matched filter response (MFR), at up to a 75% true positive rate. For a baseline, they also compared the ground truth against a second hand-labeling, yielding a 90% true positive and a 4% false positive detection rate, on average. These numbers suggest there is still room for a 15% true positive rate improvement, with the same false positive rate, over the authors' method. They are making all their images and hand labelings publicly available for interested researchers to use in evaluating related methods.

描述了一种自动定位和勾勒眼底图像中血管的方法。该工具应有助于眼科专家进行患者筛查、治疗评估和临床研究。作者的方法与以往已知方法的不同之处在于，它协同使用局部和全局血管特征来分割血管网络。作者使用20幅图像的手动标记真值分割来评估其方法。操作特性曲线显示，在高达75%的真阳性率下，与匹配滤波器响应（MFR）的基本阈值处理相比，作者的方法将假阳性降低了多达15倍。作为基线，他们还将真值与第二次手动标记进行了比较，平均得到90%的真阳性和4%的假阳性检测率。这些数字表明，在相同的假阳性率下，作者的方法仍有15%的真阳性率提升空间。他们公开了所有图像和手动标记，供感兴趣的研究人员用于评估相关方法。

Presents a new approach to the correction of intensity inhomogeneities in magnetic resonance imaging (MRI) that significantly improves intensity-based tissue segmentation. The distortion of the image brightness values by a low-frequency bias field impedes visual inspection and segmentation. The new correction method called parametric bias field correction (PABIC) is based on a simplified model of the imaging process, a parametric model of tissue class statistics, and a polynomial model of the inhomogeneity field. The authors assume that the image is composed of pixels assigned to a small number of categories with a priori known statistics. Further they assume that the image is corrupted by noise and a low-frequency inhomogeneity field. The estimation of the parametric bias field is formulated as a nonlinear energy minimization problem using an evolution strategy (ES). The resulting bias field is independent of the image region configurations and thus overcomes limitations of methods based on homomorphic filtering. Furthermore, PABIC can correct bias distortions much larger than the image contrast. Input parameters are the intensity statistics of the classes and the degree of the polynomial function. The polynomial approach combines bias correction with histogram adjustment, making it well suited for normalizing the intensity histogram of datasets from serial studies. The authors present simulations and a quantitative validation with phantom and test images. A large number of MR image data acquired with breast, surface, and head coils, both in two dimensions and three dimensions, have been processed and demonstrate the versatility and robustness of this new bias correction scheme.

提出了一种新的校正磁共振成像（MRI）中强度不均匀性的方法，该方法显著改善了基于强度的组织分割。图像亮度值由于低频偏置场而失真，妨碍了视觉检查和分割。这种新的校正方法称为参数化偏置场校正（PABIC），基于一个简化模型……

Describes a new image processing technique for rapid analysis and visualization of tagged cardiac magnetic resonance (MR) images. The method is based on the use of isolated spectral peaks in spatial modulation of magnetization (SPAMM)-tagged magnetic resonance images. The authors call the calculated angle of the complex image corresponding to one of these peaks a harmonic phase (HARP) image and sh...

描述了一种新的图像处理技术，用于快速分析和可视化标记的心脏磁共振（MR）图像。该方法基于在空间磁化调制（SPAMM）标记的磁共振图像中使用孤立的频谱峰值。作者将对应于这些峰值之一的复图像的计算角度称为谐波相位（HARP）图像，并...

Recently, imaging techniques have become available which permit nondestructive analysis of the three-dimensional (3-D) architecture of trabecular bone (TB), which forms a network of interconnected plates and rods. Most osteoporotic fractures occur at locations rich in TB, which has spurred the search for architectural parameters as determinants of bone strength. Here, the authors present a new approach to quantitative characterization of the 3-D microarchitecture of TB, based on digital topology. The method classifies each voxel of the 3-D structure based on the connectivity information of neighboring voxels. Following conversion of the 3-D digital image to a skeletonized surface representation containing only one-dimensional (1-D) and two-dimensional (2-D) structures, each voxel is classified as a curve, surface, or junction. The method has been validated by means of synthesized images and has subsequently been applied to TB images from the human wrist. The topological parameters were found to predict Young's modulus (YM) for uniaxial loading, specifically, the surface-to-curve ratio was found to be the single strongest predictor of YM (r/sup 2/=0.69). Finally, the method has been applied to TB images from a group of patients showing very large variations in topological parameters that parallel much smaller changes in bone volume fraction (BVF).

近年来，成像技术的发展使得能够对松质骨（TB）的三维结构进行无损分析，松质骨形成由相互连接的板和杆组成的网络。大多数骨质疏松性骨折发生在富含TB的部位，这促使人们寻找作为骨强度决定因素的结构参数。在此，作者提出了一种新的方法...

The authors evaluated semiautomatic, voxel-based registration methods for a new application, the assessment and optimization of interventional magnetic resonance imaging (I-MRI) guided thermal ablation of liver cancer. The abdominal images acquired on a low-field-strength, open I-MRI system contain noise, motion artifacts, and tissue deformation. Dissimilar images can be obtained as a result of di...

作者评估了半自动、基于体素的配准方法在新应用中的表现，即介入性磁共振成像（I-MRI）引导下肝癌热消融的评估和优化。在低场强开放式I-MRI系统上获取的腹部图像包含噪声、运动伪影和组织变形。由于...

Considers the direct Fourier methods (DFM's) for reconstructing an image from its given X-ray projections. The main purpose here is to use concepts from numerical analysis to estimate the errors in the methods. The authors also suggest an alternative to the interpolations involved in the DFM's and estimate the number of terms involved. Realizing that one of the main reasons for the degradation of ...

考虑使用直接傅里叶方法（DFM）从给定的X射线投影重建图像。这里的主要目的是使用数值分析的概念来估计方法中的误差。作者还提出了DFM中涉及的插值的替代方案，并估计了涉及的项数。意识到...

Arterial diameter estimation from X-ray cine angiograms is important for quantifying coronary artery disease (CAD) and for evaluating therapy. However, diameter measurement in vessel cross sections /spl les/1.0 mm is associated with large measurement errors. The authors present a novel diameter estimator which reduces both magnitude and variability of measurement error. They use a parametric nonli...

从X射线电影血管造影中估计动脉直径对于量化冠状动脉疾病（CAD）和评估治疗效果非常重要。然而，直径小于或等于1.0毫米的血管截面的直径测量存在较大的测量误差。作者提出了一种新的直径估计方法，可减少测量误差的大小和变异性。他们使用参数化非线性模型来改善小血管的测量精度。

The authors develop a direct Fourier method (DFM) for reconstructing a function from its X-ray projections. They introduce a framework that can be used to get a quantitative comparison between different choices of basis functions in the step of resampling from polar to Cartesian coordinates. They use the framework to compare polynomial interpolation, approximated sinc-functions, Gaussians, splines...

作者开发了一种直接傅里叶方法（DFM），用于从X射线投影重建函数。他们引入了一个框架，可用于在从极坐标到笛卡尔坐标的重采样步骤中，对不同基函数选择进行定量比较。他们使用该框架比较了多项式插值、近似sinc函数、高斯函数、样条函数……

Optimal sampling schedule (OSS) design for both image-derived input and output functions in tracer kinetic modeling with positron emission tomography (PET) is investigated. This problem is very important in noninvasive PET dynamic cardiac studies where both the input function, i.e., the plasma time-activity curve (PTAC), and the output function, i.e., the tissue time-activity curve (TTAC), are obt...

研究了正电子发射断层扫描（PET）示踪动力学模型中图像导出输入和输出函数的最优采样方案（OSS）设计。这个问题在非侵入性PET动态心脏研究中非常重要，其中输入函数（即血浆时间-活动曲线PTAC）和输出函数（即组织时间-活动曲线TTAC）是通过...