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When one integrates a function of two variables x,y - a point function f(P) in the plane - subject to suitable regularity conditions along an arbitrary straight line g then one obtains in the integral values F(g), a line function. In Part A of the present paper the problem which is solved is the inversion of this linear functional transformation, that is the following questions are answered: can every line function satisfying suitable regularity conditions be regarded as constructed in this way? If so, is f uniquely known from F and how can f be calculated? In Part B a solution of the dual problem of calculating a line function F(g) from its point mean values f(P) is solved in a certain sense. Finally, in Part C certain generalizations are discussed, prompted by consideration of non-Euclidean manifolds as well as higher dimensional spaces. The treatment of these problems, themselves of interest, gains enhanced importance through the numerous relationships that exist between this topic and the theory of logarithmic and Newtonian potentials. These are mentioned at appropriate places in the text.

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A new method is proposed to subtract the count of scattered photons from that acquired with a photopeak window at each pixel in each planar image of single-photon emission computed tomography (SPECT). The subtraction is carried out using two sets of data: one set is acquired with a main window centered at photopeak energy and the other is acquired with two subwindows on both sides of the main window. The scattered photons included in the main window are estimated from the counts acquired with the subwindows and then they are subtracted from the count acquired with the main windows. Since the subtraction is performed at each pixel in each planar image, the proposed method has the potential to be more precise than conventional methods. For three different activity distributions in cylinder phantoms, simulation tests gave good agreement between the activity distributions reconstructed from unscattered photons and those from the corrected data. >

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The use of the wavelet transform is explored for the detection of differences between brain functional magnetic resonance images (fMRIs) acquired under two different experimental conditions. The method benefits from the fact that a smooth and spatially localized signal can be represented by a small set of localized wavelet coefficients, while the power of white noise is uniformly spread throughout...

探索使用小波变换来检测在两种不同实验条件下获取的脑功能磁共振图像（fMRIs）之间的差异。该方法得益于这样一个事实：平滑且空间局部化的信号可以用少量局部小波系数表示，而白噪声的功率均匀分布在整个...

The usefulness of statistical clustering algorithms developed for automatic segmentation of lesions and organs in magnetic resonance imaging (MRI) intensity data sets suffers from spatial nonstationarities introduced into the data sets by the acquisition instrumentation. The major intensity inhomogeneity in MRI is caused by variations in the B1-field of the radio frequency (RF) coil. A three-step ...

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Describes an extrinsic-point-based, interactive image-guided neurosurgical system designed at Vanderbilt University, Nashville, TN, as part of a collaborative effort among the Departments of Neurological Surgery, Computer Science, and Biomedical Engineering. Multimodal image-to-image (II) and image-to-physical (IP) registration is accomplished using implantable markers. Physical space tracking is accomplished with optical triangulation. The authors investigate the theoretical accuracy of point-based registration using numerical simulations, the experimental accuracy of their system using data obtained with a phantom, and the clinical accuracy of their system using data acquired in a prospective clinical trial by 6 neurosurgeons at 4 medical centers from 158 patients undergoing craniotomies to respect cerebral lesions. The authors can determine the position of their markers with an error of approximately 0.4 mm in X-ray computed tomography (CT) and magnetic resonance (MR) images and 0.3 mm in physical space. The theoretical registration error using 4 such markers distributed around the head in a configuration that is clinically practical is approximately 0.5-0.6 mm. The mean CT-physical registration error for the: phantom experiments is 0.5 mm and for the clinical data obtained with rigid head fixation during scanning is 0.7 mm. The mean CT-MR registration error for the clinical data obtained without rigid head fixation during scanning is 1.4 mm, which is the highest mean error that the authors observed. These theoretical and experimental findings indicate that this system is an accurate navigational aid that can provide real-time feedback to the surgeon about anatomical structures encountered in the surgical field.

描述了一种基于外部点的交互式图像引导神经外科系统，由田纳西州纳什维尔的范德比尔特大学设计，是神经外科、计算机科学和生物医学工程系合作的一部分。使用植入式标记实现多模态图像到图像（II）和图像到物理（IP）配准。物理空间跟踪通过光学三角测量完成。作者通过数值模拟研究了基于点的配准的理论精度，使用体模数据验证系统的实验精度，并通过6位神经外科医生在4个医疗中心对158名接受开颅手术以切除脑部病变的患者的前瞻性临床试验数据评估了系统的临床精度。作者能够以约0.4毫米的误差在X射线计算机断层扫描（CT）和磁共振（MR）图像中确定标记位置，在物理空间中误差为0.3毫米。使用4个分布头部周围且临床实用的标记的理论配准误差约为0.5-0.6毫米。体模实验中CT-物理配准的平均误差为0.5毫米，扫描时使用刚性头部固定的临床数据平均误差为0.7毫米。扫描时未使用刚性头部固定的临床数据中CT-MR配准的平均误差为1.4毫米，这是作者观察到的最高平均误差。这些理论和实验结果表明，该系统是一种精确的导航辅助工具，可为外科医生提供手术区域中遇到的解剖结构的实时反馈。

Infrared thermal imaging of the skin has been used for several decades to monitor the temperature distribution of human skin. Abnormalities such as malignancies, inflammation, and infection cause localized increases in temperature which show as hot spots or as asymmetrical patterns in an infrared thermogram. Even though it is nonspecific, infrared thermology is a powerful detector of problems that affect a patient's physiology. While the use of infrared imaging is increasing in many industrial and security applications, it has declined in medicine probably because of the continued reliance on first generation cameras. The transfer of military technology for medical use has prompted this reappraisal of infrared thermology in medicine. Digital infrared cameras have much improved spatial and thermal resolutions, and libraries of image processing routines are available to analyze images captured both statically and dynamically. If thermographs are captured under controlled conditions, they may be interpreted readily to diagnose certain conditions and to monitor the reaction of a patient's physiology to thermal and other stresses. Some of the major areas where infrared thermography is being used successfully are neurology, vascular disorders, rheumatic diseases, tissue viability, oncology (especially breast cancer), dermatological disorders, neonatal, ophthalmology, and surgery.

红外热成像已被用于监测人体皮肤温度分布数十年。恶性肿瘤、炎症和感染等异常情况会导致局部温度升高，在红外热像图中表现为热点或不对称模式。尽管非特异性，红外热学是检测影响患者生理问题的强大工具。虽然红外成像在许多工业和安全应用中的使用正在增加，但在医学中却有所下降，这可能是因为持续依赖第一代相机。军事技术向医疗用途的转移促使了这次对医学红外热学的重新评估。数字红外相机的空间和热分辨率大大提高，并且有图像处理程序库可用于分析静态和动态捕获的图像。如果在受控条件下拍摄热像图，可以很容易地解释它们以诊断某些疾病，并监测患者对外界冷热等刺激的生理反应。红外热成像成功应用的一些主要领域是神经病学、血管疾病、风湿病、组织活力、肿瘤学（尤其是乳腺癌）、皮肤病、新生儿、眼科和外科手术。

In a previous study (J.B. West et al., J. Comput. Assist. Tomogr., vol. 21, p. 554-66, 1997) the authors demonstrated that automatic retrospective registration algorithms can frequently register magnetic resonance (MR) and computed tomography (CT) images of the brain with an accuracy of better than 2 mm, but in that same study the authors found that such algorithms sometimes fail, leading to error...

在之前的一项研究（J.B. West等人，《计算机辅助断层扫描杂志》，第21卷，第554-66页，1997年）中，作者证明了自动回顾性配准算法通常能够以优于2毫米的精度配准脑部磁共振（MR）和计算机断层扫描（CT）图像，但在同一研究中，作者发现此类算法有时会失败，导致误差...

An algorithm is developed that detects well-localized, unfragmented, thin edges in medical images based on optimization of edge configurations using a genetic algorithm (GA). Several enhancements were added to improve the performance of the algorithm over a traditional GA. The edge map is split into connected subregions to reduce the solution space and simplify the problem. The edge-map is then op...

一种算法被开发出来，基于遗传算法（GA）优化边缘配置，用于检测医学图像中定位良好、无碎片、细小的边缘。添加了几项增强功能以提高算法相对于传统GA的性能。边缘图被分割成连通的子区域以减少解空间并简化问题。然后对边缘图进行...

Preliminary evaluation of recently developed large-area flat panel detectors (FPDs) indicates that FPDs have some potential advantages: compactness, absence of geometric distortion and veiling glare with the benefits of high resolution, high detective quantum efficiency (DQE), high frame rate and high dynamic range, small image lag (<1%), and excellent linearity (/spl sim/1%). The advantages of the new FPD make it a promising candidate for cone-beam volume computed tomography (CT) angiography (CBVCTA) imaging. The purpose of this study is to characterize a prototype FPD-based imaging system for CBVCTA applications. A prototype FPD-based CBVCTA imaging system has been designed and constructed around a modified GE 8800 CT scanner. This system is evaluated for a CBVCTA imaging task in the head and neck using four phantoms and a frozen rat. The system is first characterized in terms of linearity and dynamic range of the detector. Then, the optimal selection of kVps for CBVCTA is determined and the effect of image lag and scatter on the image quality of the CBVCTA system is evaluated. Next, low-contrast resolution and high-contrast spatial resolution are measured. Finally, the example reconstruction images of a frozen rat are presented. The results indicate that the FPD-based CBVCT can achieve 2.75-1p/mm spatial resolution at 0% modulation transfer function (MTF) and provide more than enough low-contrast resolution for intravenous CBVCTA imaging in the head and neck with clinically acceptable entrance exposure level. The results also suggest that to use an FPD for large cone-angle applications, such as body angiography, further investigations are required.

最近开发的大面积平板探测器（FPD）的初步评估表明，FPD具有一些潜在优势：紧凑性、无几何失真和光晕，同时具有高分辨率、高探测量子效率（DQE）、高帧率、高动态范围、小图像滞后（<1%）和优异的线性度（/spl sim/1%）。新型FPD的这些优势使其成为锥束容积计算机断层扫描（CT）血管成像（CBVCTA）的有前景候选。本研究旨在表征一种用于CBVCTA应用的原型FPD成像系统。围绕改进的GE 8800 CT扫描仪设计和构建了一种基于FPD的原型CBVCTA成像系统。使用四个体模和一只冷冻大鼠对该系统在头颈部CBVCTA成像任务中进行评估。首先根据探测器的线性度和动态范围进行表征。然后确定CBVCTA的最佳千伏峰值选择，并评估图像滞后和散射对CBVCTA系统图像质量的影响。接下来测量低对比度分辨率和高对比度空间分辨率。最后展示冷冻大鼠的重建图像示例。结果表明，基于FPD的CBVCT可以在0%调制传递函数（MTF）下达到2.75线对/毫米的空间分辨率，并在临床可接受的入射暴露水平下为头颈部静脉内CBVCTA成像提供足够高的低对比度分辨率。结果还提示，将FPD用于大锥角应用（如体部血管成像）需要进一步研究。

An improved echo planar high-speed imaging technique using spiral scan is presented and experimental advantages are discussed. This proposed spiral-scan echo planar imaging (SEPI) technique employs two linearly increasing sinusoidal gradient fields, which results in a spiral trajectory in the spatial frequency domain (k-domain) that covers the entire frequency domain uniformly. The advantages of the method are: 1) circularly symmetric T2 weighting, resulting in a circularly symmetric point spread function in the image domain; 2) elimination of discontinuities in gradient waveforms which in turn will reduce initial transient as well as steady-state distortions; and 3) effective rapid spiral-scan from dc to high frequency in a continuous fashion, which ensures multiple pulsing with interlacing for further resolution improvement without T2 decay image degradation. Some preliminary experimental results will be presented and further possible improvements suggested.

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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……

This article presents a detailed description of an algorithm for the automatic detection of the mid-sagittal plane in three-dimensional (3-D) brain images. The algorithm seeks the plane with respect to which the image exhibits maximum symmetry. For a given plane, symmetry is measured by the cross-correlation between the image sections lying on either side. The search for the plane of maximum symme...

本文详细介绍了一种用于三维脑图像中矢状面自动检测的算法。该算法寻找使图像表现出最大对称性的平面。对于给定平面，对称性通过两侧图像区域之间的互相关来测量。寻找最大对称性平面的搜索...

This paper presents an algorithm for segmenting and measuring retinal vessels, by growing a “Ribbon of Twins” active contour model, which uses two pairs of contours to capture each vessel edge, while maintaining width consistency. The algorithm is initialized using a generalized morphological order filter to identify approximate vessels centerlines. Once the vessel segments are identified the netw...

本文提出了一种通过生长“双胞胎带”主动轮廓模型来分割和测量视网膜血管的算法，该模型使用两对轮廓捕捉每条血管边缘，同时保持宽度一致性。算法使用广义形态顺序滤波器初始化，以识别近似的血管中心线。一旦血管段被识别，网络...

Monte Carlo (MC) methods can accurately simulate scatter in X-ray imaging. However, when low noise scatter projections have to be simulated these MC simulations tend to be very time consuming. Rapid computation of scatter estimates is essential for several applications. The aim of the work presented in this paper is to speed up the estimation of noise-free scatter projections while maintaining the...

蒙特卡洛（MC）方法能够准确模拟X射线成像中的散射。然而，当需要模拟低噪声散射投影时，这些MC模拟往往非常耗时。快速计算散射估计对于多种应用至关重要。本文旨在加速无噪声散射投影的估计，同时保持...

The maximum likelihood (ML) expectation maximization (EM) approach in emission tomography has been very popular in medical imaging for several years. In spite of this, no satisfactory convergent modifications have been proposed for the regularized approach. Here, a modification of the EM algorithm is presented. The new method is a natural extension of the EM for maximizing likelihood with concave priors. Convergence proofs are given. >

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The notion of a linogram is introduced. It corresponds to the notion of a sinogram in the conventional representation of projection data in image reconstruction. In the sinogram, points which correspond to rays which go through a fixed point in the cross section to be reconstructed all fall on a sinusoidal curve. In the linogram, however, these points fall on a straight line. Thus, backprojection ...

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The magnetic particle imaging (MPI) imaging process is a new method of medical imaging with great promise. In this paper we derive the 1-D MPI signal, resolution, bandwidth requirements, signal-to-noise ratio (SNR), specific absorption rate, and slew rate limitations. We conclude with experimental data measuring the point spread function for commercially available SPIO nanoparticles and a demonstr...

磁粒子成像（MPI）成像过程是一种前景广阔的新型医学成像方法。本文推导了一维MPI信号、分辨率、带宽要求、信噪比（SNR）、比吸收率和压摆率限制。最后，我们通过实验数据测量了市售SPIO纳米颗粒的点扩散函数，并展示了一个演示。

Images captured with a typical endoscope show spatial distortion, which necessitates distortion correction for subsequent analysis. Here, a new methodology based on least squares estimation is proposed to correct the nonlinear distortion in the endoscopic images. A mathematical model based on polynomial mapping is used to map the images from distorted image space onto the corrected image space. Th...

使用典型内窥镜捕获的图像存在空间畸变，这需要畸变校正以便后续分析。本文提出了一种基于最小二乘估计的新方法来校正内窥镜图像中的非线性畸变。采用基于多项式映射的数学模型将图像从畸变图像空间映射到校正后的图像空间。

We give criteria for the distinguishability of two different conductivity distributions inside a body by electric current computed tomography (ECCT) systems with a specified precision. It is shown in a special case how these criteria can be used to determine the measurement precision needed to distinguish between two different conductivity distributions. It is also shown how to select the patterns...

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This paper presents a new reconstruction algorithm for both single- and dual-energy computed tomography (CT) imaging. By incorporating the polychromatic characteristics of the X-ray beam into the reconstruction process, the algorithm is capable of eliminating beam hardening artifacts. The single energy version of the algorithm assumes that each voxel in the scan field can be expressed as a mixture...

本文提出了一种用于单能量和双能量计算机断层扫描（CT）成像的新型重建算法。通过将X射线束的多色特性纳入重建过程，该算法能够消除射束硬化伪影。该算法的单能量版本假设扫描场中的每个体素可以表示为混合物...

We present here a new method to identify the position of the optic disc (OD) in retinal fundus images. The method is based on the preliminary detection of the main retinal vessels. All retinal vessels originate from the OD and their path follows a similar directional pattern (parabolic course) in all images. To describe the general direction of retinal vessels at any given position in the image, a geometrical parametric model was proposed, where two of the model parameters are the coordinates of the OD center. Using as experimental data samples of vessel centerline points and corresponding vessel directions, provided by any vessel identification procedure, model parameters were identified by means of a simulated annealing optimization technique. These estimated values provide the coordinates of the center of OD. A Matlab/spl reg/ prototype implementing this method was developed. An evaluation of the proposed procedure was performed using the set of 81 images from the STARE project, containing images from both normal and pathological subjects. The OD position was correctly identified in 79 out of 81 images (98%), even in rather difficult pathological situations.

我们在此提出一种新方法，用于识别视网膜眼底图像中视盘（OD）的位置。该方法基于对视网膜主要血管的初步检测。所有视网膜血管都起源于视盘，并且它们的路径在所有图像中都遵循类似的方向模式（抛物线走向）。为了描述图像中任何给定位置视网膜血管的一般方向，提出了一个几何参数模型，其中两个模型参数是视盘中心的坐标。利用任何血管识别程序提供的血管中心线点及其对应方向的实验数据样本，通过模拟退火优化技术识别模型参数。这些估计值提供了视盘中心的坐标。开发了实现该方法的Matlab原型。使用STARE项目中的81张图像（包含正常和病变受试者的图像）对所提方法进行了评估。在81张图像中，有79张（98%）正确识别了视盘位置，即使在相当困难的病变情况下也如此。

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。

Presents diffeomorphic transformations of three-dimensional (3-D) anatomical image data of the macaque occipital lobe and whole brain cryosection imagery and of deep brain structures in human brains as imaged via magnetic resonance imagery. These transformations are generated in a hierarchical manner, accommodating both global and local anatomical detail. The initial low-dimensional registration i...

介绍了猕猴枕叶和全脑冷冻切片图像以及通过磁共振成像的人类大脑深层脑结构的三维（3-D）解剖图像数据的微分同胚变换。这些变换以层次方式生成，兼顾全局和局部解剖细节。初始的低维配准...

Presents a model-based phase unwrapping method which represents the unwrapped phase function by a truncated Taylor series and a residual function. An efficient, noniterative computational algorithm is also proposed for calculating the model parameters from the phase derivatives. Sample experimental results are shown to demonstrate the effectiveness of the algorithm for extracting unwrapped phase i...

提出了一种基于模型的相位展开方法，该方法通过截断的泰勒级数和残差函数来表示展开的相位函数。还提出了一种高效的非迭代计算算法，用于从相位导数计算模型参数。示例实验结果表明了该算法在提取展开相位方面的有效性……