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Coherent X-ray scattering is related to the electron density distribution by a Fourier transform, and therefore a window into the microscopic structures of biological samples. Current techniques of scattering rely on small-angle measurements from highly collimated X-ray beams produced from synchrotron light sources. Imaging of the distribution of scattering provides a new contrast mechanism which is different from absorption radiography, but is a lengthy process of raster or line scans of the beam over the object. Here, we describe an imaging technique in the spatial frequency domain capable of acquiring both the scattering and absorption distributions in a single exposure. We present first results obtained with conventional X-ray equipment. This method interposes a grid between the X-ray source and the imaged object, so that the grid-modulated image contains a primary image and a grid harmonic image. The ratio between the harmonic and primary images is shown to be a pure scattering image. It is the auto-correlation of the electron density distribution at a specific distance. We tested a number of samples at 60–200 nm autocorrelation distance, and found the scattering images to be distinct from the absorption images and reveal new features. This technique is simple to implement, and should help broaden the imaging applications of X-ray scattering.

相干X射线散射通过傅里叶变换与电子密度分布相关，因此是生物样品微观结构的一个窗口。当前的散射技术依赖于同步辐射光源产生的高度准直X射线束的小角测量。散射分布的成像提供了一种新的对比机制……

A new approach to the problem of multimodality medical image registration is proposed, using a basic concept from information theory, mutual information (MI), or relative entropy, as a new matching criterion. The method presented in this paper applies MI to measure the statistical dependence or information redundancy between the image intensities of corresponding voxels in both images, which is assumed to be maximal if the images are geometrically aligned. Maximization of MI is a very general and powerful criterion, because no assumptions are made regarding the nature of this dependence and no limiting constraints are imposed on the image content of the modalities involved. The accuracy of the MI criterion is validated for rigid body registration of computed tomography (CT), magnetic resonance (MR), and photon emission tomography (PET) images by comparison with the stereotactic registration solution, while robustness is evaluated with respect to implementation issues, such as interpolation and optimization, and image content, including partial overlap and image degradation. Our results demonstrate that subvoxel accuracy with respect to the stereotactic reference solution can be achieved completely automatically and without any prior segmentation, feature extraction, or other preprocessing steps which makes this method very well suited for clinical applications.

提出了一种解决多模态医学图像配准问题的新方法，该方法使用信息论中的基本概念——互信息（MI）或相对熵作为新的匹配准则。本文提出的方法应用互信息来测量两幅图像中对应体素图像强度之间的统计依赖性或信息冗余，并假设当图像几何对齐时互信息最大。互信息最大化是一个非常通用且强大的准则，因为未对该依赖关系的性质做任何假设，也未对所涉及模态的图像内容施加限制性约束。通过与立体定向配准解决方案的比较，验证了互信息准则在计算机断层扫描（CT）、磁共振（MR）和光子发射断层扫描（PET）图像刚体配准中的准确性，同时评估了其对于实现问题（如插值和优化）和图像内容（包括部分重叠和图像退化）的鲁棒性。结果表明，可以完全自动地实现相对于立体定向参考解的亚体素精度，且无需任何预先分割、特征提取或其他预处理步骤，这使得该方法非常适合临床应用。

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...

After conception and implementation of any new medical image processing algorithm, validation is an important step to ensure that the procedure fulfils all requirements set forth at the initial design stage. Although the algorithm must be evaluated on real data, a comprehensive validation requires the additional use of simulated data since it is impossible to establish ground truth with in vivo data. Experiments with simulated data permit controlled evaluation over a wide range of conditions (e.g., different levels of noise, contrast, intensity artefacts, or geometric distortion). Such considerations have become increasingly important with the rapid growth of neuroimaging, i.e., computational analysis of brain structure and function using brain scanning methods such as positron emission tomography and magnetic resonance imaging. Since simple objects such as ellipsoids or parallelepipedes do not reflect the complexity of natural brain anatomy, the authors present the design and creation of a realistic, high-resolution, digital, volumetric phantom of the human brain. This three-dimensional digital brain phantom is made up of ten volumetric data sets that define the spatial distribution for different tissues (e.g., grey matter, white matter, muscle, skin, etc.), where voxel intensity is proportional to the fraction of tissue within the voxel. The digital brain phantom can be used to simulate tomographic images of the head. Since the contribution of each tissue type to each voxel in the brain phantom is known, it can be used as the gold standard to test analysis algorithms such as classification procedures which seek to identify the tissue "type" of each image voxel. Furthermore, since the same anatomical phantom may be used to drive simulators for different modalities, it is the ideal tool to test intermodality registration algorithms. The brain phantom and simulated MR images have been made publicly available on the Internet (http://www.bic.mni.mcgill.ca/brainweb).

在构思和实现任何新的医学图像处理算法之后，验证是一个重要步骤，以确保该过程满足初始设计阶段提出的所有要求。虽然算法必须在真实数据上进行评估，但全面的验证还需要额外使用模拟数据，因为无法从体内数据建立金标准...

Image interpolation techniques often are required in medical imaging for image generation (e.g., discrete back projection for inverse Radon transform) and processing such as compression or resampling. Since the ideal interpolation function spatially is unlimited, several interpolation kernels of finite size have been introduced. This paper compares 1) truncated and windowed sine; 2) nearest neighbor; 3) linear; 4) quadratic; 5) cubic B-spline; 6) cubic; g) Lagrange; and 7) Gaussian interpolation and approximation techniques with kernel sizes from 1/spl times/1 up to 8/spl times/8. The comparison is done by: 1) spatial and Fourier analyses; 2) computational complexity as well as runtime evaluations; and 3) qualitative and quantitative interpolation error determinations for particular interpolation tasks which were taken from common situations in medical image processing. For local and Fourier analyses, a standardized notation is introduced and fundamental properties of interpolators are derived. Successful methods should be direct current (DC)-constant and interpolators rather than DC-inconstant or approximators. Each method's parameters are tuned with respect to those properties. This results in three novel kernels, which are introduced in this paper and proven to be within the best choices for medical image interpolation: the 6/spl times/6 Blackman-Harris windowed sinc interpolator, and the C2-continuous cubic kernels with N=6 and N=8 supporting points. For quantitative error evaluations, a set of 50 direct digital X-rays was used. They have been selected arbitrarily from clinical routine. In general, large kernel sizes were found to be superior to small interpolation masks. Except for truncated sine interpolators, all kernels with N=6 or larger sizes perform significantly better than N=2 or N=3 point methods (p/spl Lt/0.005). However, the differences within the group of large-sized kernels were not significant. Summarizing the results, the cubic 6/spl times/6 interpolator with continuous second derivatives, as defined in (24), can be recommended for most common interpolation tasks. It appears to be the fastest six-point kernel to implement computationally. It provides eminent local and Fourier properties, is easy to implement, and has only small errors. The same characteristics apply to B-spline interpolation, but the 6/spl times/6 cubic avoids the intrinsic border effects produced by the B-spline technique. However, the goal of this study was not to determine an overall best method, but to present a comprehensive catalogue of methods in a uniform terminology, to define general properties and requirements of local techniques, and to enable the reader to select that method which is optimal for his specific application in medical imaging.

图像插值技术在医学成像中常用于图像生成（例如，用于逆拉东变换的离散反投影）以及处理如压缩或重采样。由于理想插值函数在空间上是无限的，因此引入了多种有限大小的插值核。本文比较了：1）截断和加窗sinc；2）最近邻；3）线性；4）二次；5）三次B样条；6）三次；7）拉格朗日；以及8）高斯插值和近似技术，核大小从1×1到8×8。比较通过以下方式进行：1）空间和傅里叶分析；2）计算复杂度及运行时间评估；以及3）针对医学图像处理中常见情况的特定插值任务的定性和定量插值误差确定。对于局部和傅里叶分析，引入了标准化符号并推导了插值器的基本属性。成功的方法应为直流（DC）恒定且为插值器，而非DC不恒定或近似器。每种方法的参数根据这些属性进行调整。这产生了三个新颖的核，在本文中介绍并证明是医学图像插值的最佳选择之一：6×6 Blackman-Harris窗sinc插值器，以及具有N=6和N=8支撑点的C2连续三次核。对于定量误差评估，使用了50张直接数字X光片。这些X光片是从临床常规中任意选取的。总的来说，大核尺寸优于小插值掩模。除截断sinc插值器外，所有N=6或更大尺寸的核性能显著优于N=2或N=3点方法（p<<0.005）。然而，大尺寸核组内的差异并不显著。总结结果，如（24）中定义的具有连续二阶导数的三次6×6插值器可推荐用于大多数常见插值任务。它似乎是计算上最快的六点核。它提供了卓越的局部和傅里叶特性，易于实现，且误差很小。相同的特性也适用于B样条插值，但6×6三次插值避免了B样条技术产生的固有边界效应。然而，本研究的目标并非确定总体最佳方法，而是以统一的术语提供方法的全面目录，定义局部技术的一般属性和要求，并使读者能够选择最适合其特定医学成像应用的方法。

A new model-based vision (MBV) algorithm is developed to find regions of interest (ROI's) corresponding to masses in digitized mammograms and to classify the masses as malignant/benign. The MBV algorithm is comprised of 5 modules to structurally identify suspicious ROI's, eliminate false positives, and classify the remaining as malignant or benign. The focus of attention module uses a difference of Gaussians (DoG) filter to highlight suspicious regions in the mammogram. The index module uses tests to reduce the number of nonmalignant regions from 8.39 to 2.36 per full breast image. Size, shape, contrast, and Laws texture features are used to develop the prediction module's mass models. Derivative-based feature saliency techniques are used to determine the best features for classification. Nine features are chosen to define the malignant/benign models. The feature extraction module obtains these features from all suspicious ROI's. The matching module classifies the regions using a multilayer perceptron neural network architecture to obtain an overall classification accuracy of 100% for the segmented malignant masses with a false-positive rate of 1.8 per full breast image. This system has a sensitivity of 92% for locating malignant ROI's. The database contains 272 images (12 b, 100 /spl mu/m) with 36 malignant and 53 benign mass images. The results demonstrate that the MBV approach provides a structured order of integrating complex stages into a system for radiologists.

提出了一种新的基于模型的视觉（MBV）算法，用于在数字化乳腺X光片中识别与肿块对应的感兴趣区域（ROI），并将肿块分类为恶性/良性。该MBV算法由5个模块组成，用于结构性地识别可疑ROI、消除假阳性，并将剩余的分类为恶性或良性。注意力聚焦模块使用高斯差...

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 describe almost entirely automated procedures for estimation of global, voxel, and cluster-level statistics to test the null hypothesis of zero neuroanatomical difference between two groups of structural magnetic resonance imaging (MRI) data. Theoretical distributions under the null hypothesis are available for (1) global tissue class volumes; (2) standardized linear model [analysis of variance (ANOVA and ANCOVA)] coefficients estimated at each voxel; and (3) an area of spatially connected clusters generated by applying an arbitrary threshold to a two-dimensional (2-D) map of normal statistics at voxel level. The authors describe novel methods for economically ascertaining probability distributions under the null hypothesis, with fewer assumptions, by permutation of the observed data. Nominal Type I error control by permutation testing is generally excellent; whereas theoretical distributions may be over conservative. Permutation has the additional advantage that it can be used to test any statistic of interest, such as the sum of suprathreshold voxel statistics in a cluster (or cluster mass), regardless of its theoretical tractability under the null hypothesis. These issues are illustrated by application to MRI data acquired from 18 adolescents with hyperkinetic disorder and 16 control subjects matched for age and gender.

作者描述了几乎完全自动化的程序，用于估计全局、体素和簇级统计量，以检验两组结构磁共振成像（MRI）数据之间神经解剖学差异为零的零假设。零假设下的理论分布可用于（1）全局组织类别体积；（2）标准化线性模型[分析...

In the technique known as gridding, the data samples are weighted for sampling density and convolved with a finite kernel, then resampled on a grid preparatory to a fast Fourier transform. The authors compare the artifact introduced into the image for various convolving functions of different sizes, including the Kaiser-Bessel window and the zero-order prolate spheroidal wave function (PSWF). They also show a convolving function that improves upon the PSWF in some circumstances. >

在称为网格化的技术中，数据样本根据采样密度进行加权，并与有限核进行卷积，然后在网格上重新采样，以准备快速傅里叶变换。作者比较了不同大小的各种卷积函数引入图像的伪影，包括Kaiser-Bessel窗口和零阶扁长球面波函数（PSWF）。他们...

Magnetic resonance imaging (MRI) is unique in its ability to noninvasively and selectively alter tissue magnetization and create tagged patterns within a deforming body such as the heart muscle. The resulting patterns define a time-varying curvilinear coordinate system on the tissue, which the authors track with coupled B-snake grids. B-spline bases provide local control of shape, compact representation, and parametric continuity. Efficient spline warps are proposed which warp an area in the plane such that two embedded snake grids obtained from two tagged frames are brought into registration, interpolating a dense displacement vector field. The reconstructed vector field adheres to the known displacement information at the intersections, forces corresponding snakes to be warped into one another, and for all other points in the plane, where no information is available, a C/sup 1/ continuous vector field is interpolated. The implementation proposed in this paper improves on the authors' previous variational-based implementation and generalizes warp methods to include biologically relevant contiguous open curves, in addition to standard landmark points. The methods are validated with a cardiac motion simulator, in addition to in-vivo tagging data sets.

磁共振成像（MRI）具有独特的能力，能够非侵入性地、选择性地改变组织磁化，并在变形体（如心肌）内部创建标记模式。由此产生的模式定义了组织上随时间变化的曲线坐标系，作者使用耦合的B样条网格对其进行跟踪。B样条基提供了形状的局部控制、紧凑的表征...

Guidance systems designed for neurosurgery, hip surgery, and spine surgery, and for approaches to other anatomy that is relatively rigid can use rigid-body transformations to accomplish image registration. These systems often rely on point-based registration to determine the transformation, and many such systems use attached fiducial markers to establish accurate fiducial points for the registration, the points being established by some fiducial localization process. Accuracy is important to these systems, as is knowledge of the level of that accuracy. An advantage of marker-based systems, particularly those in which the markers are bone-implanted, is that registration error depends only on the fiducial localization error (FLE) and is thus to a large extent independent of the particular object being registered. Thus, it should be possible to predict the clinical accuracy of marker-based systems on the basis of experimental measurements made with phantoms or previous patients. This paper presents two new expressions for estimating registration accuracy of such systems and points out a danger in using a traditional measure of registration accuracy. The new expressions represent fundamental theoretical results with regard to the relationship between localization error and registration error in rigid-body, point-based registration. Rigid-body, point-based registration is achieved by finding the rigid transformation that minimizes "fiducial registration error" (FRE), which is the root mean square distance between homologous fiducials after registration. Closed form solutions have been known since 1966. The expected value (FRE/sup 2/) depends on the number N of fiducials and expected squared value of FLE, (FLE/sup 2/), but in 1979 it was shown that (FRE/sup 2/) is approximately independent of the fiducial configuration C. The importance of this surprising result seems not yet to have been appreciated by the registration community: Poor registrations caused by poor fiducial configurations may appear to be good due to a small FRE value. A more critical and direct measure of registration error is the "target registration error" (TRE), which is the distance between homologous points other than the centroids of fiducials. Efforts to characterize its behavior have been made since 1989. Published numerical simulations have shown that (TRE/sup 2/) is roughly proportional to (FLE/sup 2/)/N and, unlike (FRE/sup 2/), does depend in some way on C. Thus, FRE, which is often used as feedback to the surgeon using a point-based guidance system, is in fact an unreliable indicator of registration-accuracy. In this work the authors derive approximate expressions for (TRE/sup 2/), and for the expected squared alignment error of an individual fiducial. They validate both approximations through numerical simulations. The former expression can be used to provide reliable feedback to the surgeon during surgery and to guide the placement of markers before surgery, or at least to warn the surgeon of potentially dangerous fiducial placements; the latter expression leads to a surprising conclusion: Expected registration accuracy (TRE) is worst near the fiducials that are most closely aligned! This revelation should be of particular concern to surgeons who may at present be relying on fiducial alignment as an indicator of the accuracy of their point-based guidance systems.

设计用于神经外科、髋关节手术和脊柱手术以及其它相对刚体解剖结构的引导系统可以采用刚体变换实现图像配准。这些系统通常依赖点配准来确定变换，许多此类系统使用附着的基准标记来建立精确的配准基准点，这些点通过某种基准定位过程确定。准确性对这些系统至关重要，同样重要的是对准确性水平的了解。基于标记的系统（特别是那些标记植入骨中的系统）的一个优势是配准误差仅取决于基准定位误差（FLE），因此在很大程度上独立于被配准的特定对象。因此，应该能够根据使用模体或既往患者进行的实验测量来预测基于标记的系统的临床准确性。本文提出了两个新表达式来估计此类系统的配准准确性，并指出了使用传统配准准确性度量的危险性。新表达式代表了关于刚体点配准中定位误差与配准误差之间关系的基本理论结果。刚体点配准通过找到使“基准配准误差”（FRE）最小化的刚体变换来实现，该误差是配准后对应基准点之间的均方根距离。闭式解自1966年以来已知。期望值（FRE/sup 2/）取决于基准数量N和FLE的期望平方值（FLE/sup 2/），但在1979年发现（FRE/sup 2/）近似独立于基准配置C。这个令人惊讶的结果的重要性似乎尚未被配准学界充分认识到：由不良基准配置导致的差配准可能因为小的FRE值而显得良好。一个更关键和直接的配准误差度量是“目标配准误差”（TRE），即非基准质心的对应点之间的距离。自1989年以来一直努力描述其行为。已发表的数值模拟表明，（TRE/sup 2/）大致与（FLE/sup 2/）/N成正比，并且与（FRE/sup 2/）不同，它在某种程度上依赖于C。因此，经常用作基于点的引导系统外科医生反馈的FRE实际上是一个不可靠的配准准确性指标。在这项工作中，作者推导了（TRE/sup 2/）和单个基准的预期平方对准误差的近似表达式。他们通过数值模拟验证了这两个近似。前者表达式可用于在手术期间向外科医生提供可靠的反馈，并在术前指导标记放置，或至少警告外科医生潜在危险的基准放置；后者表达式得出一个令人惊讶的结论：预期配准准确性（TRE）在最接近对准的基准附近最差！这一发现对于目前可能依赖基准对准作为基于点的引导系统准确性指标的外科医生尤其值得关注。

This paper describes the use of color image analysis to automatically discriminate between oesophagus, stomach, small intestine, and colon tissue in wireless capsule endoscopy (WCE). WCE uses “pill-cam” technology to recover color video imagery from the entire gastrointestinal tract. Accurately reviewing and reporting this data is a vital part of the examination, but it is tedious and time consuming. Automatic image analysis tools play an important role in supporting the clinician and speeding up this process. Our approach first divides the WCE image into subimages and rejects all subimages in which tissue is not clearly visible. We then create a feature vector combining color, texture, and motion information of the entire image and valid subimages. Color features are derived from hue saturation histograms, compressed using a hybrid transform, incorporating the discrete cosine transform and principal component analysis. A second feature combining color and texture information is derived using local binary patterns. The video is segmented into meaningful parts using support vector or multivariate Gaussian classifiers built within the framework of a hidden Markov model. We present experimental results that demonstrate the effectiveness of this method.

本文描述了使用彩色图像分析在无线胶囊内窥镜（WCE）中自动区分食道、胃、小肠和结肠组织的方法。WCE使用“药丸相机”技术从整个胃肠道获取彩色视频图像。准确审查和报告这些数据是检查的重要部分，但繁琐且耗时。

A fast and simple algorithm for designing time-optimal waveforms is presented. The algorithm accepts a given arbitrary multidimensional $k$-space trajectory as the input and outputs the time-optimal gradient waveform that traverses $k$-space along that path in minimum time. The algorithm is noniterative, and its run time is independent of the complexity of the curve, i.e., the number of switches ...

提出了一种快速简单的算法用于设计时间最优波形。该算法接受给定的任意多维$k$空间轨迹作为输入，并输出沿该路径以最小时间遍历$k$空间的时间最优梯度波形。该算法非迭代，其运行时间与曲线的复杂度无关，即与开关次数...

One of the major drawbacks of magnetic resonance imaging (MRI) has been the lack of a standard and quantifiable interpretation of image intensities. Unlike in other modalities, such as X-ray computerized tomography, MR images taken for the same patient on the same scanner at different times may appear different from each other due to a variety of scanner-dependent variations and, therefore, the absolute intensity values do not have a fixed meaning. The authors have devised a two-step method wherein all images (independent of patients and the specific brand of the MR scanner used) can be transformed in such a may that for the same protocol and body region, in the transformed images similar intensities will have similar tissue meaning. Standardized images can be displayed with fixed windows without the need of per-case adjustment. More importantly, extraction of quantitative information about healthy organs or about abnormalities can be considerably simplified. This paper introduces and compares new variants of this standardizing method that can help to overcome some of the problems with the original method.

磁共振成像的主要缺点之一是缺乏对图像强度的标准和可量化解释。与其他模态（如X射线计算机断层扫描）不同，同一患者在同一扫描仪上不同时间拍摄的MR图像可能因多种扫描仪相关变化而彼此不同，因此，上述问题...

Based on the theory of approximation, this paper presents a unified analysis of interpolation and resampling techniques. An important issue is the choice of adequate basis functions. The authors show that, contrary to the common belief, those that perform best are not interpolating. By opposition to traditional interpolation, the authors call their use generalized interpolation; they involve a prefiltering step when correctly applied. The authors explain why the approximation order inherent in any basis function is important to limit interpolation artifacts. The decomposition theorem states that any basis function endowed with approximation order ran be expressed as the convolution of a B spline of the same order with another function that has none. This motivates the use of splines and spline-based functions as a tunable way to keep artifacts in check without any significant cost penalty. The authors discuss implementation and performance issues, and they provide experimental evidence to support their claims.

基于逼近理论，本文对插值和重采样技术进行了统一分析。一个重要问题是选择合适的基函数。作者表明，与普遍看法相反，表现最佳的基函数并非插值函数。与传统插值相反，作者称他们的使用为广义插值；当正确应用时，它涉及一个预滤波步骤。作者解释了任何基函数固有的逼近阶对于限制插值伪影的重要性。分解定理指出，任何具有逼近阶的基函数都可以表示为相同阶的B样条与另一个没有逼近阶的函数的卷积。这促使使用样条和基于样条的函数作为一种可调谐的方式来控制伪影，而无需显著增加成本。作者讨论了实现和性能问题，并提供了实验证据来支持他们的主张。

During the last few years, optical coherence tomography (OCT) has demonstrated considerable promise as a method of high-resolution intravascular imaging. The goal of this study was to apply and to test the applicability of the rotating kernel transformation (RKT) technique to the speckle reduction and enhancement of OCT images. The technique is locally adaptive. It is based on sequential applicati...

在过去几年中，光学相干断层成像（OCT）已展现出作为高分辨率血管内成像方法的巨大潜力。本研究旨在应用并测试旋转核变换（RKT）技术对OCT图像进行散斑抑制和增强的适用性。该技术具有局部自适应性，基于连续应用...

This paper presents a quantitative comparison of three types of information available for 52 patients scheduled for carotid endarterectomy: subjective classification of the ultrasound images obtained during scanning before operation, first- and second-order statistical features extracted from regions of the plaque in still ultrasound images from three orthogonal scan planes and finally a histologi...

本文对52名计划进行颈动脉内膜切除术患者的三种可用信息进行了定量比较：术前扫描过程中获得的超声图像的主观分类、从三个正交扫描平面的静止超声图像中的斑块区域提取的一阶和二阶统计特征，最后是组织学检查。

This paper presents two new rebinning algorithms for the reconstruction of three-dimensional (3-D) positron emission tomography (PET) data. A rebinning algorithm is one that first sorts the 3-D data into an ordinary two-dimensional (2-D) data set containing one sinogram for each transaxial slice to be reconstructed; the 3-D image is then recovered by applying to each slice a 2-D reconstruction method such as filtered-backprojection. This approach allows a significant speedup of 3-D reconstruction, which is particularly useful for applications involving dynamic acquisitions or whole-body imaging. The first new algorithm is obtained by discretizing an exact analytical inversion formula. The second algorithm, called the Fourier rebinning algorithm (FORE), is approximate but allows an efficient implementation based on taking 2-D Fourier transforms of the data. This second algorithm was implemented and applied to data acquired with the new generation of PET systems and also to simulated data for a scanner with an 18/spl deg/ axial aperture. The reconstructed images were compared to those obtained with the 3-D reprojection algorithm (3DRP) which is the standard "exact" 3-D filtered-backprojection method. Results demonstrate that FORE provides a reliable alternative to 3DRP, while at the same time achieving an order of magnitude reduction in processing time.

本文提出了两种新的重排算法，用于重建三维正电子发射断层扫描（PET）数据。重排算法首先将三维数据排序为普通二维数据集，其中包含每个待重建的横向切片的正弦图；然后通过对每个切片应用二维重建方法恢复三维图像...

An algorithm is presented for the fuzzy segmentation of two-dimensional (2-D) and three-dimensional (3-D) multispectral magnetic resonance (MR) images that have been corrupted by intensity inhomogeneities, also known as shading artifacts. The algorithm is an extension of the 2-D adaptive fuzzy C-means algorithm (2-D AFCM) presented in previous work by the authors. This algorithm models the intensity inhomogeneities as a gain field that causes image intensities to smoothly and slowly vary through the image space. It iteratively adapts to the intensity inhomogeneities and is completely automated. In this paper, the authors fully generalize 2-D AFCM to three-dimensional (3-D) multispectral images. Because of the potential size of 3-D image data, they also describe a new faster multigrid-based algorithm for its implementation. They show, using simulated MR data, that 3-D AFCM yields lower error rates than both the standard fuzzy C-means (FCM) algorithm and two other competing methods, when segmenting corrupted images. Its efficacy is further demonstrated using real 3-D scalar and multispectral MR brain images.

提出了一种用于二维和三维多光谱磁共振图像模糊分割的算法，这些图像受到强度不均匀性（也称为阴影伪影）的污染。该算法是作者先前工作中提出的二维自适应模糊C均值算法的扩展。该算法将强度不均匀性建模为一个增益场，导致图像强度在图像空间中平滑且缓慢地变化。它迭代地适应强度不均匀性，并且是完全自动化的。在本文中，作者将二维自适应模糊C均值算法完全推广到三维多光谱图像。由于三维图像数据的潜在大小，他们还描述了一种新的基于多网格的更快算法来实现。他们使用模拟的磁共振数据表明，在分割受污染的图像时，三维自适应模糊C均值算法比标准的模糊C均值算法和其他两种竞争方法具有更低的错误率。使用真实的三维标量和多光谱磁共振脑图像进一步证明了其有效性。

Using statistical methods the reconstruction of positron emission tomography (PET) images can be improved by high-resolution anatomical information obtained from magnetic resonance (MR) images. The authors implemented two approaches that utilize MR data for PET reconstruction. The anatomical MR information is modeled as a priori distribution of the PET image and combined with the distribution of t...

利用统计方法，正电子发射断层成像（PET）图像的重建可以通过从磁共振（MR）图像中获得的高分辨率解剖信息得到改善。作者实现了两种利用MR数据进行PET重建的方法。解剖MR信息被建模为PET图像的先验分布，并与...分布相结合。

Presents a fully automatic three-dimensional classification of brain tissues for Magnetic Resonance (MR) images. An MR image volume may be composed of a mixture of several tissue types due to partial volume effects. Therefore, the authors consider that in a brain dataset there are not only the three main types of brain tissue: gray matter, white matter, and cerebro spinal fluid, called pure classe...

提出了一种全自动的三维脑组织分类方法用于磁共振（MR）图像。由于部分体积效应，MR图像体素可能由多种组织类型混合而成。因此，作者认为在脑数据集中不仅存在三种主要脑组织类型：灰质、白质和脑脊液，称为纯类...

A comparison of six similarity measures for use in intensity-based two-dimensional-three-dimensional (2-D-3-D) image registration is presented. The accuracy of the similarity measures are compared to a "gold-standard" registration which has been accurately calculated using fiducial markers. The similarity measures are used to register a computed tomography (CT) scan of a spine phantom to a fluoroscopy image of the phantom. The registration is carried out within a region-of-interest in the fluoroscopy image which is user defined to contain a single vertebra. Many of the problems involved in this type of registration are caused by features which were not modeled by a phantom image alone. More realistic "gold-standard" data sets were simulated using the phantom image with clinical image features overlaid. Results show that the introduction of soft-tissue structures and interventional instruments into the phantom image can have a large effect on the performance of some similarity measures previously applied to 2-D-3-D image registration. Two measures were able to register accurately and robustly even when soft-tissue structures and interventional instruments were present as differences between the images. These measures were pattern intensity and gradient difference. Their registration accuracy, for all the rigid-body parameters except for the source to film translation, was within a root-mean-square (rms) error of 0.53 mm or degrees to the "gold-standard" values. No failures occurred while registering using these measures.

本文比较了六种基于强度的二维-三维（2-D-3-D）图像配准中的相似性度量。这些相似性度量的精度与使用基准标记精确计算的金标准配准进行了比较。这些相似性度量用于将脊柱模型的计算机断层扫描（CT）图像注册到荧光透视图像...

The accuracy of image-guided neurosurgery generally suffers from brain deformations due to intraoperative changes. These deformations cause significant changes of the anatomical geometry (organ shape and spatial interorgan relations), thus making intraoperative navigation based on preoperative images error prone. In order to improve the navigation accuracy, the authors developed a biomechanical mo...

图像引导神经外科的准确性通常受到术中变化导致的脑变形的影响。这些变形会引起解剖几何（器官形状和空间器官间关系）的显著变化，从而使基于术前图像的术中导航容易出错。为了提高导航精度，作者开发了一种生物力学模型...

The solution of impedance distribution in electrical impedance tomography is a nonlinear inverse problem that requires the use of a regularization method. The generalized Tikhonov regularization methods have been popular in the solution of many inverse problems. The regularization matrices that are usually used with the Tikhonov method are more or less ad hoc and the implicit prior assumptions are, thus, in many cases inappropriate. In this paper, the authors propose an approach to the construction of the regularization matrix that conforms to the prior assumptions on the impedance distribution. The approach is based on the construction of an approximating subspace for the expected impedance distributions. It is shown by simulations that the reconstructions obtained with the proposed method are better than with two other schemes of the same type when the prior is compatible with the true object. On the other hand, when the prior is incompatible with the true object, the method will still give reasonable estimates.

电阻抗成像中阻抗分布的求解是一个非线性逆问题，需要使用正则化方法。广义Tikhonov正则化方法在许多逆问题的求解中很受欢迎。通常与Tikhonov方法一起使用的正则化矩阵或多或少是特设的，因此隐含的先验假设在许多情况下是不合适的。在本文中，作者提出了一种构建与阻抗分布先验假设相一致的正则化矩阵的方法。该方法基于为预期的阻抗分布构建近似子空间。模拟结果表明，当先验与真实对象一致时，所提出的方法获得的重建结果优于其他两种同类方案。另一方面，当先验与真实对象不一致时，该方法仍能给出合理的估计。

A method is described for the automated detection of microcalcifications in digitized mammograms. The method is based on the Laplacian scale-space representation of the mammogram only. First, possible locations of microcalcifications are identified as local maxima in the filtered image on a range of scales. For each finding, the size and local contrast is estimated, based on the Laplacian response...

描述了一种用于数字化乳腺X线摄影中微钙化自动检测的方法。该方法仅基于乳腺X线摄影的拉普拉斯尺度空间表示。首先，在一系列尺度上，将微钙化的可能位置识别为滤波后图像中的局部最大值。对于每个发现，根据拉普拉斯响应估计其大小和局部对比度...