Volume 18, Issue 5

In order to perform attenuation correction in emission tomography an attenuation map is required. The authors propose a new method to compute this map directly from the emission sinogram, eliminating the transmission scan from the acquisition protocol. The problem is formulated as an optimization task where the objective function is a combination of the likelihood and an a priori probability. The latter uses a Gibbs prior distribution to encourage local smoothness and a multimodal distribution for the attenuation coefficients. Since the attenuation process is different in positron emission tomography (PET) and single photon emission tomography (SPECT), a separate algorithm for each case is derived. The method has been tested on mathematical phantoms and on a few clinical studies. For PET, good agreement was found between the images obtained with transmission measurements and those produced by the new algorithm in an abdominal study. For SPECT, promising simulation results have been obtained for nonhomogeneous attenuation due to the presence of the lungs.

为了在发射断层扫描中进行衰减校正，需要衰减图。作者提出了一种新方法，直接从发射正弦图计算该图，从而消除了采集协议中的透射扫描。该问题被表述为一个优化任务，其中目标函数是似然函数和先验概率的组合。后者使用吉布斯先验分布来鼓励局部平滑，并使用衰减系数的多模态分布。由于正电子发射断层扫描（PET）和单光子发射断层扫描（SPECT）中的衰减过程不同，因此为每种情况推导了单独的算法。该方法已在数学体模和一些临床研究中进行了测试。对于PET，在腹部研究中，透射测量获得的图像与新算法产生的图像之间取得了良好的一致性。对于SPECT，由于肺的存在导致的非均匀衰减，获得了有希望的模拟结果。

Image registration is a real challenge because physicians handle many images. Temporal registration is necessary in order to follow the various steps of a disease, whereas multimodal registration allows us to improve the identification of some lesions or to compare pieces of information gathered from different sources. This paper presents an algorithm for temporal and/or multimodal registration of...

图像配准是一个真正的挑战，因为医生需要处理大量图像。为了跟踪疾病的不同阶段，时间配准是必要的，而多模态配准则使我们能够改善某些病变的识别或比较来自不同来源的信息。本文提出了一种用于眼底图像的时间和/或多模态配准算法...

For certain medical applications resampling of data is required. In magnetic resonance tomography (MRT) or computer tomography (CT), e.g., data may be sampled on nonrectilinear grids in the Fourier domain. For the image reconstruction a convolution-interpolation algorithm, often called gridding, can be applied for resampling of the data onto a rectilinear grid. Resampling of data from a rectilinea...

在某些医学应用中，需要对数据进行重采样。例如，在磁共振断层成像（MRT）或计算机断层成像（CT）中，数据可能在傅里叶域中的非直线网格上进行采样。为了进行图像重建，可以采用卷积插值算法（通常称为网格化）将数据重采样到直线网格上。从直线网格重采样数据...

The registration of retinal images is required to facilitate the study of the optic nerve head and the retina. The method the authors propose combines the use of mutual information as the similarity measure and simulated annealing as the search technique. It is robust toward large transformations between the images and significant changes in light intensity. By using a pyramid sampling approach co...

视网膜图像的配准是促进视神经头和视网膜研究所需的。作者提出的方法结合了互信息作为相似性度量和模拟退火作为搜索技术。它对图像之间的大变换和光强度的显著变化具有鲁棒性。通过使用金字塔采样方法…

This paper presents a tumor detection system for fully digital mammography. The processing scheme adopted in the proposed system focuses on the solution of two problems. One is how to detect tumors as suspicious regions with a very weak contrast to their background and another is how to extract features which characterize malignant tumors. For the first problem, a unique adaptive filter called the...

本文提出了一种用于全数字乳腺摄影的肿瘤检测系统。该系统采用的处理方案专注于解决两个问题：一是如何检测与背景对比度极弱的可疑区域中的肿瘤，二是如何提取表征恶性肿瘤的特征。针对第一个问题，提出了一种称为自适应滤波器的独特方法...

Evaluating precisely the temporal variations of lesion volumes is very important for at least three types of practical applications: pharmaceutical trials, decision making for drug treatment or surgery, and patient follow-up. Here, the authors present a volumetric analysis technique, combining precise rigid registration of three-dimensional (3-D) (volumetric) medical images, nonrigid deformation c...

精确评估病灶体积的时间变化对于至少三类实际应用非常重要：药物试验、药物治疗或手术的决策以及患者随访。作者提出了一种体积分析技术，结合三维（3D）医学图像的精确刚性配准、非刚性变形...

Since the work by Osher and Sethian (1988) on level-sets algorithms for numerical shape evolutions, this technique has been used for a large number of applications in numerous fields. In medical imaging, this numerical technique has been successfully used, for example, in segmentation and cortex unfolding algorithms. The migration from a Lagrangian implementation to a Eulerian one via implicit rep...

自Osher和Sethian（1988年）关于数值形状演化的水平集算法工作以来，该技术已被广泛应用于众多领域。在医学影像中，该数值技术已成功应用于例如分割和皮层展开算法。从拉格朗日实现到欧拉实现的迁移通过隐式表示...

Quantitative estimation of brain glucose metabolism (rCMRGlc) with positron emission tomography and fluorodeoxyglucose involves arterial blood sampling to estimate the delivery of radioactivity to the brain. Usually, for an intravenous injection of 30 s duration, an accurate input curve requires a frequency of one sample every 5 s or less to determine the peak activity in arterial plasma during th...

使用正电子发射断层扫描和氟脱氧葡萄糖定量估计脑葡萄糖代谢（rCMRGlc）涉及动脉采血以估计放射性物质向大脑的输送。通常，对于持续30秒的静脉注射，准确的输入曲线需要每5秒或更短时间采样一次，以确定动脉血浆中的峰值活性。

A differential index (DI) assignment scheme is proposed for the image encoding system in which a variable-length tree-structured vector quantizer (VLTSVQ) is adopted. Each source vector is quantized into a terminal node of VLTSVQ and each terminal node is represented as a unique binary vector. The proposed index assignment scheme utilizes the correlation between interblocks of the image to increas...

提出了一种差分索引（DI）分配方案，用于采用可变长度树结构矢量量化器（VLTSVQ）的图像编码系统。每个源矢量被量化为VLTSVQ的一个终端节点，每个终端节点表示为一个唯一的二进制向量。该索引分配方案利用图像块间的相关性来增加...