Volume 22, Issue 3

We propose a robust wavelet domain method for noise filtering in medical images. The proposed method adapts itself to various types of image noise as well as to the preference of the medical expert; a single parameter can be used to balance the preservation of (expert-dependent) relevant details against the degree of noise reduction. The algorithm exploits generally valid knowledge about the correlation of significant image features across the resolution scales to perform a preliminary coefficient classification. This preliminary coefficient classification is used to empirically estimate the statistical distributions of the coefficients that represent useful image features on the one hand and mainly noise on the other. The adaptation to the spatial context in the image is achieved by using a wavelet domain indicator of the local spatial activity. The proposed method is of low complexity, both in its implementation and execution time. The results demonstrate its usefulness for noise suppression in medical ultrasound and magnetic resonance imaging. In these applications, the proposed method clearly outperforms single-resolution spatially adaptive algorithms, in terms of quantitative performance measures as well as in terms of visual quality of the images.

我们提出了一种用于医学图像噪声过滤的鲁棒小波域方法。该方法能够自适应地处理各种类型的图像噪声，并满足医学专家的偏好；通过单个参数，可以在保留（依赖于专家的）相关细节和降噪程度之间取得平衡。该算法利用关于显著图像特征在不同分辨率尺度上相关性的普遍有效知识，进行初步的系数分类。这种初步的系数分类用于经验性地估计代表有用图像特征的系数和主要代表噪声的系数的统计分布。通过使用局部空间活动的小波域指示器来实现对图像空间上下文的适应。该方法在实现和执行时间上都具有较低的复杂度。结果证明了它在医学超声和磁共振成像中噪声抑制的有效性。在这些应用中，无论在定量性能指标还是图像视觉质量方面，该方法都明显优于单分辨率空间自适应算法。

The nonparametric multiscale platelet algorithms presented in this paper, unlike traditional wavelet-based methods, are both well suited to photon-limited medical imaging applications involving Poisson data and capable of better approximating edge contours. This paper introduces platelets, localized functions at various scales, locations, and orientations that produce piecewise linear image approx...

本文提出的非参数多尺度血小板算法，不同于传统的基于小波的方法，既非常适用于涉及泊松数据的光子受限医学成像应用，又能更好近似边缘轮廓。本文介绍了血小板，即在不同尺度、位置和方向上的局部函数，它们产生分段线性图像近似...

Active shape models (ASMs) are often limited by the inability of relatively few eigenvectors to capture the full range of biological shape variability. This paper presents a method that overcomes this limitation, by using a hierarchical formulation of active shape models, using the wavelet transform. The statistical properties of the wavelet transform of a deformable contour are analyzed via princ...

主动形状模型往往受到相对较少特征向量无法捕捉生物形状变异全范围的限制。本文提出了一种克服该局限性的方法，通过使用小波变换构建分层主动形状模型。通过主成分分析，分析了可变形轮廓小波变换的统计特性。

Describes the feasibility of selecting a fractal feature vector based on M-band wavelet transform to classify ultrasonic liver images - normal liver, cirrhosis, and hepatoma. The proposed feature extraction algorithm is based on the spatial-frequency decomposition and fractal geometry. Various classification algorithms based on respective texture measurements and filter banks are presented and tes...

描述了基于M波段小波变换选择分形特征向量对超声肝脏图像（正常肝脏、肝硬化、肝肿瘤）进行分类的可行性。所提出的特征提取算法基于空间频率分解和分形几何。基于各自纹理测量和滤波器组的不同分类算法被提出并测试。

Several techniques based on the three-dimensional (3-D) discrete cosine transform (DCT) have been proposed for volumetric data coding. These techniques fail to provide lossless coding coupled with quality and resolution scalability, which is a significant drawback for medical applications. This paper gives an overview of several state-of-the-art 3-D wavelet coders that do meet these requirements a...

基于三维离散余弦变换的几种技术已被提出用于体数据编码。这些技术无法提供无损编码同时实现质量和分辨率可伸缩性，这对医学应用来说是一个重大缺陷。本文概述了几种满足这些要求的最先进的三维小波编码器……

We study lossy-to-lossless compression of medical volumetric data using three-dimensional (3-D) integer wavelet transforms. To achieve good lossy coding performance, it is important to have transforms that are unitary. In addition to the lifting approach, we first introduce a general 3-D integer wavelet packet transform structure that allows implicit bit shifting of wavelet coefficients to approxi...

我们研究使用三维整数小波变换对医学体积数据进行有损到无损压缩。为了实现良好的有损编码性能，使用酉变换非常重要。除了提升方法外，我们首先引入了一种通用的三维整数小波包变换结构，该结构允许对小波系数进行隐式位移以近似...

This paper presents a new algorithm for enhancement of microcalcifications in mammograms. The main novelty is the application of techniques we have developed for construction of filterbanks derived from the continuous wavelet transform. These discrete wavelet decompositions, called integrated wavelets, are optimally designed for enhancement of multiscale structures in images. Furthermore, we use a...

本文提出了一种用于乳腺X线图像中微钙化增强的新算法。主要创新在于应用我们开发的基于连续小波变换的滤波器组构建技术。这些离散小波分解被称为综合小波，针对图像中多尺度结构的增强进行了优化设计。此外，我们使用...

Addresses the problem of detecting significant changes in fMRI time series that are correlated to a stimulus time course. This paper provides a new approach to estimate the parameters of a semiparametric generalized linear model of the fMRI time series. The fMRI signal is described as the sum of two effects: a smooth trend and the response to the stimulus. The trend belongs to a subspace spanned b...

解决检测与刺激时间过程相关的fMRI时间序列中显著变化的问题。本文提供了一种新方法来估计fMRI时间序列的半参数广义线性模型的参数。fMRI信号被描述为两个效应的和：平滑趋势和对刺激的响应。趋势属于由...张成的子空间。

Describes a new filter for parametric images obtained from dynamic positron emission tomography (PET) studies. The filter is based on the wavelet transform following the heuristics of a previously published method that are here developed into a rigorous theoretical framework. It is shown that the space-time problem of modeling a dynamic PET sequence reduces to the classical one of estimation of a ...

描述了一种用于动态正电子发射断层扫描（PET）研究获得的参数图像的新型滤波器。该滤波器基于小波变换，遵循先前发表方法的启发式规则，此处将其发展成严格的理论框架。结果表明，对动态PET序列建模的时空问题简化为经典的估计问题。

A different approach to the problem of estimation of the ultrasound pulse spectrum, which usually arises as a part of ultrasound image restoration algorithms, is presented. It is shown that this estimation problem can be reformulated in terms of a de-noising problem. In this formulation, the log-spectrum of a radio-frequency line (RF-line) is viewed as a noisy measurement of the signal that needs ...

本文提出了一种不同的超声脉冲频谱估计方法，该问题通常作为超声图像恢复算法的一部分出现。研究表明，该估计问题可以重新表述为去噪问题。在这种表述中，射频线（RF-line）的对数谱被视为所需信号的有噪声测量...

We propose a fully three-dimensional (3-D) wavelet-based coding system featuring 3-D encoding/two-dimensional (2-D) decoding functionalities. A fully 3-D transform is combined with context adaptive arithmetic coding; 2-D decoding is enabled by encoding every 2-D subband image independently. The system allows a finely graded up to lossless quality scalability on any 2-D image of the dataset. Fast a...

我们提出了一种完全基于三维小波的编码系统，具有三维编码/二维解码功能。该系统将完全的三维变换与上下文自适应算术编码相结合；通过独立编码每个二维子带图像实现二维解码。该系统允许对数据集中的任何二维图像进行从精细分级到无损质量的可扩展性。快速访问...

We consider the problem of detecting clustered microcalcification in digitized mammograms using new wavelets with a high Sobolev regularity index. We experimentally assess the superiority of the new wavelets when compared with the classical ones.

我们考虑使用具有高Sobolev正则性指数的新小波检测数字化乳腺X光片中的簇状微钙化问题。我们通过实验评估了新小波与经典小波相比的优越性。

In tomographic medical devices such as single photon emission computed tomography or positron emission tomography cameras, image reconstruction is an unstable inverse problem, due to the presence of additive noise. A new family of regularization methods for reconstruction, based on a thresholding procedure in wavelet and wavelet packet (WP) decompositions, is studied. This approach is based on the...

在断层医学成像设备如单光子发射计算机断层扫描或正电子发射断层扫描相机中，由于加性噪声的存在，图像重建是一个不稳定的逆问题。研究了一种基于小波和小波包分解中的阈值处理的新正则化重建方法族。该方法基于...

A new method is proposed for activation detection in event-related functional magnetic resonance imaging (fMRI). The method is based on the analysis of selected resolution levels (a subspace) in the translation invariant wavelet transform (TIWT) domain. Using a priori knowledge about the activation signal and trends, we analyze their power in different resolution levels in the TIWT domain and sele...

提出了一种新方法用于事件相关功能磁共振成像（fMRI）中的激活检测。该方法基于在平移不变小波变换（TIWT）域中对所选分辨率级别（子空间）的分析。利用关于激活信号和趋势的先验知识，我们分析了它们在TIWT域中不同分辨率级别的功率，并选择...

We propose a new wavelet-based reconstruction method suited to three-dimensional (3-D) cone-beam (CB) tomography. It is derived from the Feldkamp algorithm and is valid for the same geometrical conditions. The demonstration is done in the framework of nonseparable wavelets and requires ideally radial wavelets. The proposed inversion formula yields to a filtered backprojection algorithm but the fil...

我们提出了一种新的基于小波的重建方法，适用于三维（3-D）锥束（CB）断层成像。该方法源于Feldkamp算法，并适用于相同的几何条件。证明是在非分离小波框架内完成的，并理想地需要径向小波。所提出的反演公式产生了一个滤波反投影算法，但...