Volume 18, Issue 3

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。

Clustered microcalcifications on X-ray mammograms are an important sign for early detection of breast cancer. Texture-analysis methods can be applied to detect clustered microcalcifications in digitized mammograms. In this paper, a comparative study of texture-analysis methods is performed for the surrounding region-dependence method, which has been proposed by the authors, and conventional textur...

X线乳腺照片上的成簇微钙化是早期检测乳腺癌的重要征象。纹理分析方法可应用于检测数字化乳腺X线照片中的成簇微钙化。本文对作者提出的周围区域依赖法和传统纹理分析方法进行了比较研究。

Systematic mapping of the variability in cortical sulcal anatomy is an area of increasing interest which presents numerous methodological challenges. To address these issues, the authors have implemented sulcal extraction and assisted labeling (SEAL) to automatically extract the two-dimensional (2-D) surface ribbons that represent the median axis of cerebral sulci and to neuroanatomically label th...

系统性绘制大脑皮层沟解剖的变异性是一个越来越受关注的领域，它提出了许多方法论上的挑战。为了解决这些问题，作者们实现了沟提取和辅助标记（SEAL），以自动提取代表脑沟中轴的二维表面带，并进行神经解剖学标记...

In tomographic imaging, dynamic images are typically obtained by reconstructing the frames of a time sequence independently, one by one. A disadvantage of this frame-by-frame reconstruction approach is that it fails to account. For temporal correlations in the signal. Ideally, one should treat the entire image sequence as a single spatio-temporal signal. However, the resulting reconstruction task ...

在断层成像中，动态图像通常通过独立逐帧重建时间序列的帧来获得。这种逐帧重建方法的一个缺点是未能考虑信号中的时间相关性。理想情况下，应将整个图像序列视为一个单一的时空信号。然而，由此产生的重建任务...

In this paper a temporal learning-filtering procedure is applied to refine the left ventricle (LV) boundary detected by an active-contour model. Instead of making prior assumptions about the LV shape or its motion, this information is incrementally gathered directly from the images and is exploited to achieve more coherent segmentation. A Hough transform technique is used to find an initial approx...

本文应用时间学习-滤波程序来优化由主动轮廓模型检测到的左心室（LV）边界。不是对LV形状或运动做出先验假设，而是直接从图像中逐步收集这些信息，并利用它们实现更一致的分割。使用霍夫变换技术来找到初始近似...

Many segmentation methods for thoracic volume data require manual input in the form of a seed point, initial contour, volume of interest etc. The aim of the work presented here is to further automate this segmentation initialization step. In this paper an anatomical modeling and matching method is proposed to coarsely segment thoracic volume data into anatomically labeled regions. An anatomical mo...

许多胸部体积数据的分割方法需要手动输入种子点、初始轮廓、感兴趣区域等。本文旨在进一步自动化该分割初始化步骤。本文提出了一种解剖建模和匹配方法，将胸部体积数据粗分割为解剖标记区域。一个解剖模...

A variety of applications and research directions in magnetic resonance imaging which require fast scan times have recently become popular. In order to satisfy many of the requirements of these applications, snapshot imaging methods, which acquire an entire image in one excitation, are often used. These snapshot techniques are relatively insensitive to motion and can allow rapidly occurring proces...

在磁共振成像中，需要快速扫描时间的各种应用和研究方向最近变得流行起来。为了满足这些应用的许多要求，通常使用在一次激励中获取整个图像的快照成像方法。这些快照技术对运动相对不敏感，并且可以允许快速发生的过程...

The final diagnosis in coronary angiography has to be performed on a large set of original images. Therefore, lossless compression schemes play a key role in medical database management and telediagnosis applications. This paper proposes a wavelet-based compression scheme that is able to operate in the lossless mode. The quantization module implements a new way of coding of the wavelet coefficient...

冠状动脉造影的最终诊断必须基于大量原始图像。因此，无损压缩方案在医疗数据库管理和远程诊断应用中起着关键作用。本文提出了一种基于小波的压缩方案，能够以无损模式运行。量化模块实现了一种新的小波系数编码方式...

Presents two variants of the EM algorithm for dynamic SPECT imaging, A version based on compartmental modeling which fits a sum of exponentials and a more general approach allowing for arbitrary decaying activities. The underlying probabilistic models are discussed and the incomplete and complete data spares are shown to be physically meaningful. The authors indicate that the second method, leadin...

介绍了动态SPECT成像的两种EM算法变体，一种基于隔室建模，拟合指数和，另一种更通用的方法允许任意衰减活动。讨论了潜在的统计模型，并展示了不完整和完整数据稀疏性在物理上的意义。作者指出，第二种方法，导致...

The computed radiography (CR) technique, also known as the storage phosphor imaging technique, has evolved to be a major candidate for large-scale implementation of digital radiography during the past decade, In order to obtain a reasonable spatial resolution, the storage phosphor plate used is generally limited in thickness. This leads to X-rays being only partially absorbed by the detector. Usef...

计算放射摄影（CR）技术，也称为存储荧光体成像技术，在过去十年中已发展成为大规模实施数字放射摄影的主要候选技术。为了获得合理的空间分辨率，所使用的存储荧光体板通常厚度有限，这导致X射线仅被探测器部分吸收。使...