Volume 23, Issue 4

A method is presented for automated segmentation of vessels in two-dimensional color images of the retina. This method can be used in computer analyses of retinal images, e.g., in automated screening for diabetic retinopathy. The system is based on extraction of image ridges, which coincide approximately with vessel centerlines. The ridges are used to compose primitives in the form of line elements. With the line elements an image is partitioned into patches by assigning each image pixel to the closest line element. Every line element constitutes a local coordinate frame for its corresponding patch. For every pixel, feature vectors are computed that make use of properties of the patches and the line elements. The feature vectors are classified using a kNN-classifier and sequential forward feature selection. The algorithm was tested on a database consisting of 40 manually labeled images. The method achieves an area under the receiver operating characteristic curve of 0.952. The method is compared with two recently published rule-based methods of Hoover et al. and Jiang et al. . The results show that our method is significantly better than the two rule-based methods (p<0.01). The accuracy of our method is 0.944 versus 0.947 for a second observer.

提出了一种用于视网膜二维彩色图像中血管自动分割的方法。该方法可用于视网膜图像的计算机分析，例如糖尿病视网膜病变的自动筛查。该系统基于提取图像脊线，这些脊线与血管中心线大致重合。脊线用于组成线元素形式的基元...

The watershed transform has interesting properties that make it useful for many different image segmentation applications: it is simple and intuitive, can be parallelized, and always produces a complete division of the image. However, when applied to medical image analysis, it has important drawbacks (oversegmentation, sensitivity to noise, poor detection of thin or low signal to noise ratio structures). We present an improvement to the watershed transform that enables the introduction of prior information in its calculation. We propose to introduce this information via the use of a previous probability calculation. Furthermore, we introduce a method to combine the watershed transform and atlas registration, through the use of markers. We have applied our new algorithm to two challenging applications: knee cartilage and gray matter/white matter segmentation in MR images. Numerical validation of the results is provided, demonstrating the strength of the algorithm for medical image segmentation.

分水岭变换具有有趣的特性，使其在许多不同的图像分割应用中非常有用：它简单直观，可以并行化，并且总是产生图像的完整分割。然而，当应用于医学图像分析时，它具有重要的缺点（过度分割、对噪声敏感、对薄结构或低信噪比结构的检测能力差...）

Noncontact optical measurements from diffuse media could facilitate the use of large detector arrays at multiple angles that are well suited for diffuse optical tomography applications. Such imaging strategy could eliminate the need for individual fibers in contact with tissue, restricted geometries, and matching fluids. Thus, it could significantly improve experimental procedures and enhance our ...

来自漫射介质的非接触光学测量可促进多角度大探测器阵列的使用，非常适合漫射光学断层成像应用。这种成像策略可消除与组织接触的单个光纤、受限几何形状和匹配液体的需求。因此，可显著改善实验流程并提升我们的...

Positron emission tomography (PET) of the cerebral glucose metabolism has shown to be useful in the presurgical evaluation of patients with epilepsy. Between seizures, PET images using fluorodeoxyglucose (FDG) show a decreased glucose metabolism in areas of the gray matter (GM) tissue that are associated with the epileptogenic region. However, detection of subtle hypo-metabolic regions is limited ...

脑葡萄糖代谢的正电子发射断层扫描（PET）已被证明在癫痫患者术前评估中有用。在癫痫发作间期，使用氟脱氧葡萄糖（FDG）的PET图像显示与致痫区相关的灰质（GM）组织区域葡萄糖代谢降低。然而，检测细微的低代谢区域是有限的……

Iterative image reconstruction algorithms play an increasingly important role in modern tomographic systems, especially in emission tomography. With the fast increase of the sizes of the tomographic data, reduction of the computation demands of the reconstruction algorithms is of great importance. Fourier-based forward and back-projection methods have the potential to considerably reduce the compu...

迭代图像重建算法在现代断层成像系统中发挥着越来越重要的作用，尤其是在发射断层成像中。随着断层成像数据量的快速增长，降低重建算法的计算需求变得非常重要。基于傅里叶的正向和反向投影方法有潜力大幅减少计算...

An efficient Gauss-Newton iterative imaging technique utilizing a three-dimensional (3-D) field solution coupled to a two-dimensional (2-D) parameter estimation scheme (3-D/2-D) is presented for microwave tomographic imaging in medical applications. While electromagnetic wave propagation is described fully by a 3-D vector field, a 3-D scalar model has been applied to improve the efficiency of the ...

提出了一种用于医学微波断层成像的高效高斯-牛顿迭代成像技术，该技术利用三维（3-D）场解耦合二维（2-D）参数估计方案（3-D/2-D）。虽然电磁波传播完全由三维矢量场描述，但为了提高计算效率，本文采用了三维标量模型。

We present a method of performing fast and accurate three-dimensional (3-D) backprojection using only Fourier transform operations for line-integral data acquired by planar detector arrays in positron emission tomography. This approach is a 3-D extension of the two-dimensional (2-D) linogram technique of Edholm. By using a special choice of parameters to index a line of response (LOR) for a pair o...

我们提出了一种方法，仅利用傅里叶变换操作对正电子发射断层扫描中平面探测器阵列获取的线积分数据进行快速准确的三维反投影。该方法是Edholm二维线图技术的三维扩展。通过使用特殊的参数选择来索引一对响应线（LOR），...

It is argued that positron annihilation into three photons, although quite rare, could still be used as a new imaging modality of positron emission tomography. The information gained when the three decay photons are detected is significantly higher than in the case of 511 keV two-gamma annihilation. The performance of three-gamma imaging in terms of the required detector properties, spatial resolu...

有人认为，正电子湮灭成三个光子虽然相当罕见，但仍可被用作正电子发射断层扫描的一种新的成像模式。当检测到三个衰变光子时，获得的信息明显高于511 keV双伽马湮灭的情况。三伽马成像在所需探测器特性、空间分辨率等方面的性能...

Image compression is indispensable in medical applications where inherently large volumes of digitized images are presented. JPEG 2000 has recently been proposed as a new image compression standard. The present recommendations on the choice of JPEG 2000 encoder options were based on nontask-based metrics of image quality applied to nonmedical images. We used the performance of a model observer [no...

图像压缩在医学应用中不可或缺，因为通常会产生大量数字化图像。JPEG 2000最近被提出作为一种新的图像压缩标准。目前关于JPEG 2000编码器选项选择的建议是基于应用于非医学图像的非任务型图像质量指标。我们使用模型观察者的性能[no...

It is well known that 40%-50% of hepatocellular carcinoma (HCC) do not show increased /sup 18/F-fluorodeoxyglucose (FDG) uptake. Recent research studies have demonstrated that /sup 11/C-acetate may be a complementary tracer to FDG in positron emission tomography (PET) imaging of HCC in the liver. Quantitative dynamic modeling is, therefore, conducted to evaluate the kinetic characteristics of this...

众所周知，40%-50%的肝细胞癌（HCC）不表现出 /sup 18/F-氟脱氧葡萄糖（FDG）摄取增高。最近的研究表明，/sup 11/C-乙酸盐可能是 FDG 在肝脏 HCC 的正电子发射断层扫描（PET）成像中的补充示踪剂。因此，进行定量动力学建模以评估其动力学特性...

The ideas of parallel imaging techniques, designed to shorten the acquisition time by the simultaneous use of multiple receive coils, can be adapted for parallel transmission of a spatially selective multidimensional RF pulse. In analogy to data acquisition, a multidimensional RF pulse follows a certain trajectory in k-space. Shortening this trajectory shortens the pulse duration. The use of multi...

并行成像技术的思路，通过同时使用多个接收线圈来缩短采集时间，可以适用于空间选择性多维射频脉冲的并行传输。与数据采集类似，多维射频脉冲在k空间中遵循特定轨迹。缩短该轨迹可缩短脉冲持续时间。使用多...

In this paper, we study the resolution properties of those algorithms where a filtering step is applied after every iteration. As concrete examples we take filtered preconditioned gradient descent algorithms for the Poisson log likelihood for PET emission data. For nonlinear estimators, resolution can be characterized in terms of the linearized local impulse response (LLIR). We provide analytic ap...

在本文中，我们研究了每次迭代后应用滤波步骤的算法的分辨率特性。具体例子是用于PET发射数据的泊松对数似然的滤波预条件梯度下降算法。对于非线性估计量，分辨率可以通过线性化局部脉冲响应（LLIR）来表征。我们提供了解析近似...

This paper describes a new method for assessing clinical parameters from a noisy regional time-activity curve (TAC) in tomographic gated blood-pool ventriculography. This method is based on a priori knowledge on the shape of a TAC, and shape approximation. The rejection method was used to generate different random Poisson deviates, covering standard count levels, of six representative TACs in orde...

本文描述了一种从断层门控血池心室造影中的噪声区域时间-活度曲线(TAC)评估临床参数的新方法。该方法基于对TAC形状的先验知识和形状近似。采用拒绝法生成六个代表性TAC的不同随机泊松偏差，覆盖标准计数水平，以...

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