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Currently available tomographic image reconstruction schemes for optical tomography (OT) are mostly based on the limiting assumptions of small perturbations and a priori knowledge of the optical properties of a reference medium. Furthermore, these algorithms usually require the inversion of large, full, ill-conditioned Jacobian matrixes. In this work a gradient-based iterative image reconstruction (GIIR) method is presented that promises to overcome current limitations. The code consists of three major parts: (1) A finite-difference, time-resolved, diffusion forward model is used to predict detector readings based on the spatial distribution of optical properties; (2) An objective function that describes the difference between predicted and measured data; (3) An updating method that uses the gradient of the objective function in a line minimization scheme to provide subsequent guesses of the spatial distribution of the optical properties for the forward model. The reconstruction of these properties is completed, once a minimum of this objective function is found. After a presentation of the mathematical background, two- and three-dimensional reconstruction of simple heterogeneous media as well as the clinically relevant example of ventricular bleeding in the brain are discussed. Numerical studies suggest that intraventricular hemorrhages can be detected using the GIIR technique, even in the presence of a heterogeneous background.

目前可用于光学断层扫描（OT）的断层图像重建方案大多基于小扰动的限制性假设以及对参考介质光学特性的先验知识。此外，这些算法通常需要求解大型、满秩、病态的雅可比矩阵。本研究提出了一种基于梯度的迭代图像重建（GIIR）方法，有望克服现有局限性。该代码包含三个主要部分：（1）使用有限差分时间分辨扩散前向模型，根据光学特性的空间分布预测探测器读数；（2）描述预测数据与测量数据差异的目标函数；（3）一种更新方法，利用目标函数梯度在线最小化方案中提供前向模型光学特性空间分布的后续猜测。一旦找到目标函数的最小值，这些特性的重建即告完成。在介绍数学背景后，讨论了简单异质介质的二维和三维重建，以及临床上相关的脑室出血实例。数值研究表明，即使存在异质背景，GIIR技术也能检测到脑室内出血。

This paper presents a new nonrigid monomodality image registration algorithm based on $B$-splines. The deformation is described by a cubic $B$-spline field and found by minimizing the energy between a reference image and a deformed version of a floating image. To penalize noninvertible transformation, we propose two different constraints on the Jacobian of the transformation and its derivatives. T...

本文提出了一种基于B样条的非刚性单模态图像配准算法。变形由三次B样条场描述，并通过最小化参考图像与浮动图像变形版本之间的能量来求解。为了惩罚不可逆变换，我们提出了两种不同的约束条件，分别作用于变换的雅可比矩阵及其导数。...

A partial-differential equations (PDE)-based system for detecting the boundary of skin lesions in digital clinical skin images is presented. The image is first preprocessed via contrast-enhancement and anisotropic diffusion. If the lesion is covered by hairs, a PDE-based continuous morphological filter that removes them is used as an additional preprocessing step. Following these steps, the skin l...

提出了一种基于偏微分方程（PDE）的系统，用于检测数字临床皮肤图像中皮肤病变的边界。图像首先通过对比度增强和各向异性扩散进行预处理。如果病变被毛发覆盖，则使用基于PDE的连续形态学滤波器将其移除作为额外的预处理步骤。在这些步骤之后，皮肤病变...

Segmenting lesions is a vital step in many computerized mass-detection schemes for digital (or digitized) mammograms. The authors have developed two novel lesion segmentation techniques-one based on a single feature called the radial gradient index (RGI) and one based on simple probabilistic models to segment mass lesions, or other similar nodular structures, from surrounding background. In both m...

分割病变是许多计算机化数字（或数字化）乳腺X线摄影肿块检测方案中的关键步骤。作者开发了两种新颖的病变分割技术——一种基于单一特征即径向梯度指数（RGI），另一种基于简单的概率模型，用于从周围背景中分割肿块病变或其他类似结节结构。两种方法都……

This paper presents the adaptive axial interpolator (AAI), a novel spiral interpolation approach for multislice spiral computed tomography (CT) implemented in a clinical multislice CT scanner, the SOMATOM Volume Zoom (Siemens Medical Systems, Forchheim, Germany). The method works on parallel-beam data generated from the acquired fan-beam data by azimuthal rebinning. Spiral interpolation is perform...

本文介绍了自适应轴向插值器（AAI），这是一种用于多层螺旋计算机断层扫描（CT）的新型螺旋插值方法，已在临床多层螺旋CT扫描仪SOMATOM Volume Zoom（西门子医疗系统，德国福希海姆）中实现。该方法通过对采集的扇形束数据进行方位角重排，生成平行束数据。螺旋插值执行...

Computational burden is a major concern when an iterative algorithm is used to reconstruct a three-dimensional (3-D) image with attenuation, detector response, and scatter corrections. Most of the computation time is spent executing the projector and backprojector of an iterative algorithm. Usually, the projector and the backprojector are transposed operators of each other. The projector should mo...

当使用迭代算法重建具有衰减、探测器响应和散射校正的三维（3-D）图像时，计算负担是一个主要问题。大部分计算时间用于执行迭代算法的投影器和反投影器。通常，投影器和反投影器是互为转置的算子。投影器应该

A general reconstruction algorithm for magnetic resonance imaging (MRI) with gradients having arbitrary time dependence is presented. This method estimates spin density by calculating the weighted correlation of the observed free induction decay signal and the phase modulation function at each point. A theorem which states that this method can be derived from the conditions of linearity and shift ...

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White matter fiber bundles in the human brain can be located by tracing the local water diffusion in diffusion weighted magnetic resonance imaging (MRI) images. In this paper, a novel Bayesian modeling approach for white matter tractography is presented. The uncertainty associated with estimated white matter fiber paths is investigated, and a method for calculating the probability of a connection ...

人类大脑中的白质纤维束可以通过追踪扩散加权磁共振成像（MRI）图像中的局部水扩散来定位。本文提出了一种新颖的贝叶斯建模方法用于白质纤维束成像。研究了与估计的白质纤维路径相关的不确定性，并提出了计算连接概率的方法...

Parallel transmission is a very promising candidate technology to mitigate the inevitable radio-frequency (RF) field inhomogeneity in magnetic resonance imaging at ultra-high field. For the first few years, pulse design utilizing this technique was expressed as a least squares problem with crude power regularizations aimed at controlling the specific absorption rate (SAR), hence the patient safety...

平行传输是一项非常有前景的候选技术，旨在减轻超高场磁共振成像中不可避免的射频场不均匀性。在最初几年，利用该技术的脉冲设计被表述为一个最小二乘问题，并采用粗略的功率正则化来控制特定吸收率（SAR），从而确保患者安全……

Displacement encoding with stimulated echoes (DENSE) encodes myocardial tissue displacement into the phase of the MR image. Cine DENSE allows for rapid quantification of myocardial displacement at multiple cardiac phases through the majority of the cardiac cycle. For practical sensitivities to motion, relatively high displacement encoding frequencies are used and phase wrapping typically occurs. I...

位移编码刺激回波（DENSE）将心肌组织位移编码到MR图像的相位中。电影DENSE允许在大多数心动周期内以多个心相位快速量化心肌位移。为了对运动具有实际灵敏度，使用相对较高的位移编码频率，通常会发生相位包裹。本...

A study of different cubic interpolation kernels in the frequency domain is presented that reveals novel aspects of both cubic spline and cubic convolution interpolation. The kernel used in cubic convolution is of finite support and depends on a parameter to be chosen at will. At the Nyquist frequency, the spectrum attains a value that is independent of this parameter. Exactly the same value is fo...

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Trabecular bone (TB) is a complex quasi-random network of interconnected plates and rods. TB constantly remodels to adapt to the stresses to which it is subjected (Wolff's Law). In osteoporosis, this dynamic equilibrium between bone formation and resorption is perturbed, leading to bone loss and structural deterioration. Both bone loss and structural deterioration increase fracture risk. Bone's me...

松质骨是一个由相互连接的板状和杆状结构组成的复杂准随机网络。松质骨不断重塑以适应其所承受的应力（沃尔夫定律）。在骨质疏松症中，骨形成和骨吸收之间的动态平衡被打破，导致骨质流失和结构恶化。骨质流失和结构恶化都会增加骨折风险。骨的力学...

The authors detail the design and implementation of HANDX, a model-based computer vision system used in the domain of medical image processing. Given a digitized hand radiograph, HANDX segments out specific bones and measures particular parameters of the bones, without requiring specific characterization of noise variations in background contrast and anatomical differences which arise from patient...

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Remarkable progress in positron emission tomography (PET) development has occurred in recent years, in hardware, software, and computer implementation of image reconstruction. Recent development in PET scanners such as the high-resolution research tomograph (HRRT) developed by CTI (now Siemens) represents such a case and is capable of greatly enhanced resolution as well as sensitivity. In these PET scanners, the amount of coincidence line data collected contains more than $4.5\times 10^{9}$ coincidence lines of response generated by as many nuclear detectors as 120 000. This formidable amount of data and the reconstruction of this data set pose a real problem in HRRT and have also been of the major bottle neck in further developments of high resolution PET scanners as well as their applications. In these classes of PET scanners, therefore, obtaining one set of reconstructed images often requires many hours of image reconstruction. For example, in HRRT with full data collection in a normal brain scan (using SPAN 3), the image reconstruction time is close to 80 min, making it practically impossible to attempt any list-mode-based dynamic imaging since the image reconstruction time would take many days (as much as 43 h or more for 32–frame dynamic image reconstruction). To remedy this data-handling problem in image reconstruction, we developed a new algorithm based on the symmetry properties of the projection and backprojection processes, especially in the 3-D OSEM algorithm where multiples of projection and back-projection are required. In addition, the single-instruction multiple-data (SIMD) technique also allowed us to successfully incorporate the symmetry properties mentioned above, thereby effectively reducing the total image reconstruction time to a few minutes. We refer to this technique as the symmetry and SIMD-based projection-backprojection (SSP) technique or algorithm and the details of th

近年来，正电子发射断层扫描（PET）在硬件、软件和图像重建的计算机实现方面取得了显著进展。最近PET扫描仪的发展，例如CTI（现为西门子）开发的高分辨率研究断层扫描仪（HRRT）就是一个例子，它能够大大提高分辨率和灵敏度。在这些PET扫描仪中，收集到的符合线数据量包含超过4.5×10^9条符合响应线，由多达120,000个核探测器生成。这一庞大的数据量及其重建在HRRT中构成了一个实际问题，并且也是高分辨率PET扫描仪进一步发展及其应用的主要瓶颈之一。因此，在这类PET扫描仪中，获取一组重建图像通常需要数小时的图像重建时间。例如，在正常脑部扫描（使用SPAN 3）中，HRRT完全数据采集的图像重建时间接近80分钟，这使得任何基于列表模式的动态成像几乎不可能，因为图像重建时间需要数天（32帧动态图像重建需要43小时或更长时间）。为了解决图像重建中的这一数据处理问题，我们开发了一种基于投影和反投影过程对称性的新算法，特别是在需要多次投影和反投影的三维OSEM算法中。此外，单指令多数据（SIMD）技术也使我们能够成功结合上述对称性，从而有效将总图像重建时间减少到几分钟。我们将此技术称为基于对称性和SIMD的投影-反投影（SSP）技术或算法。

The noise-equivalent count-rate (NEC) performance of a neuro-positron emission tomography (PET) scanner has been determined with and without interplane septa on uniform cylindrical phantoms of differing radii and in human studies to assess the optimum count rate conditions that realize the maximum gain. In the brain, the effective gain in NEC performance for three-dimensions (3-D) ranges from >5 a...

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For the 3D-reconstruction of organ surfaces from tomograms, a shading method based on the partial volume effect is presented. In contrast to methods based on the depth and/or the angle of the voxel surface, here the gray-level gradient along the surface is used for shading. It is shown, that at least for bone and soft tissue surfaces, the results are superior to conventional shading. This is due t...

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A new method to correct the barrel distortion of an electronic endoscope image is presented. A correction model assuming circularly symmetric distortion is introduced with the following model parameters: the center of distortion and the coefficients of polynomials representing the distortion correction in the radial direction. If the imaging system is distortion-free, straight lines in the object ...

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Presents a new class of algorithms for penalized-likelihood reconstruction of attenuation maps from low-count transmission scans. We derive the algorithms by applying to the transmission log-likelihood a version of the convexity technique developed by De Pierro for emission tomography. The new class includes the single-coordinate ascent (SCA) algorithm and Lange's convex algorithm for transmission...

提出了一类新的算法，用于从低计数透射扫描数据中惩罚似然重建衰减图。我们通过对透射对数似然函数应用De Pierro为发射断层扫描开发的凸性技术的一个版本，推导出这些算法。新类别包括单坐标上升（SCA）算法和Lange的凸算法用于透射...

Dual-energy material density images obtained by prereconstruction-basis material decomposition techniques offer specific tissue information, but they exhibit relatively high pixel noise. It is shown that noise in the material density images is negatively correlated and that this can be exploited for noise reduction in the two-basis material density images. The algorithm minimizes noise-related dif...

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A method is presented to interpolate between neighboring slices in a grey-scale tomographic data set. Spatial correspondence between adjacent slices is established using a nonrigid registration algorithm based on B-splines which optimizes the normalized mutual information similarity measure. Linear interpolation of the image intensities is then carried out along the directions calculated by the re...

提出了一种在灰度断层数据集中对相邻切片进行插值的方法。利用基于B样条的非刚体配准算法建立相邻切片之间的空间对应关系，该算法优化了归一化互信息相似性度量。然后沿着由配准计算出的方向对图像强度进行线性插值...

This paper presents a novel speckle suppression method for medical B-scan ultrasonic images. An original image is first separated into two parts with an adaptive filter. These two parts are then transformed into a multiscale wavelet domain and the wavelet coefficients are processed by a soft thresholding method, which is a variation of Donoho's (1995) soft thresholding method. The processed coeffi...

本文提出了一种用于医学B超图像的新型散斑抑制方法。首先通过自适应滤波器将原始图像分为两部分。然后将这两部分变换到多尺度小波域，并采用Donoho（1995）软阈值方法的变体对小波系数进行处理。处理后的系数...

A method for the automatic measurement of femur length in fetal ultrasound images is presented. Fetal femur length measurements are used to estimate gestational age by comparing the measurement to a typical growth chart. Using a real-time ultrasound system, sonographers currently indicate the femur endpoints on the ultrasound display station with a mouse-like device. The measurements are subjectiv...

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The new spiral multislice computed tomography (CT) scanners and the significant increase in rotation speed offer great potential for cardiac imaging with X-ray CT. The authors have therefore developed the dedicated cardiac reconstruction algorithms 180/spl deg/ multislice cardio interpolation (MCI) and 180/spl deg/ multislice cardio delta (MCD) and here offer further details and validation. The al...

新型螺旋多层计算机断层扫描（CT）扫描仪以及旋转速度的显著提高为X射线CT心脏成像提供了巨大潜力。因此，作者开发了专门的心脏重建算法180°多层心脏插值（MCI）和180°多层心脏delta（MCD），并在此提供进一步的细节和验证。该算...

Modeling the hemodynamic response in functional magnetic resonance (fMRI) experiments is an important aspect of the analysis of functional neuroimages. This has been done in the past using parametric response function, from a limited family. In this contribution, the authors adopt a semi-parametric approach based on finite impulse response (FIR) filters. In order to cope with the increase in the n...

在功能性磁共振（fMRI）实验中，对血流动力学反应进行建模是功能性神经图像分析的一个重要方面。过去，这一直使用来自有限族的参数响应函数来完成。在这项贡献中，作者采用了一种基于有限脉冲响应（FIR）滤波器的半参数方法。为了应对n...

Artifacts can result when reconstructing a dynamic image sequence from inconsistent, as well as insufficient and truncated, cone beam single photon emission computed tomography (SPECT) projection data acquired by a slowly rotating gantry. The artifacts can lead to biases in kinetic model parameters estimated from time-activity curves generated by overlaying volumes of interest on the images. Howev...

当从由慢速旋转机架采集的不一致、不充分且截断的锥束单光子发射计算机断层扫描（SPECT）投影数据重建动态图像序列时，可能会产生伪影。这些伪影可能导致通过将感兴趣区域叠加在图像上生成的时间-活动曲线估计的动力学模型参数出现偏差。