Volume 19, Issue 6

Traditional space-invariant regularization methods in tomographic image reconstruction using penalized-likelihood estimators produce images with nonuniform spatial resolution properties. The local point spread functions that quantify the smoothing properties of such estimators are space variant, asymmetric, and object-dependent even for space invariant imaging systems. The authors propose a new quadratic regularization scheme for tomographic imaging systems that yields increased spatial uniformity and is motivated by the least-squares fitting of a parameterized local impulse response to a desired global response. The authors have developed computationally efficient methods for PET systems with shift-invariant geometric responses. They demonstrate the increased spatial uniformity of this new method versus conventional quadratic regularization schemes in simulated PET thorax scans.

在采用惩罚似然估计器的层析图像重建中，传统的空间不变正则化方法会产生空间分辨率不均匀的图像。即使是空间不变的成像系统，量化此类估计器平滑特性的局部点扩散函数也是空间可变、非对称且依赖于物体的。作者针对层析成像系统提出了一种新的二次正则化方案，该方案通过将参数化局部脉冲响应的最小二乘拟合到期望的全局响应，从而提高空间均匀性。作者为具有移不变几何响应的PET系统开发了计算高效的方法。他们在模拟PET胸部扫描中展示了这种新方法相比传统二次正则化方案在空间均匀性上的提升。

Interpretation of magnetic resonance angiography (MRA) is problematic due to complexities of vascular shape and to artifacts such as the partial volume effect. The authors present new methods to assist in the interpretation of MRA. These include methods for detection of vessel paths and for determination of branching patterns of vascular trees. They are based on the ordered region growing (ORG) al...

由于血管形状的复杂性和部分容积效应等伪影，磁共振血管造影（MRA）的解释存在问题。作者提出了新的方法以辅助MRA的解释，包括血管路径检测和血管树分支模式确定的方法。这些方法基于有序区域生长（ORG）算法……

Development of complex software applications in image guided therapy (IGT) is often complicated by the fact that providing basic functionality for image processing and user interaction from a graphical user interfaces (GUI) requires considerable manpower for software development. The authors present a programming environment that combines the high-level image processing library AVW, in-house devel...

在图像引导治疗（IGT）中开发复杂的软件应用程序常常因一个事实而变得复杂：从图形用户界面（GUI）提供图像处理和用户交互的基本功能需要大量的人力进行软件开发。作者介绍了一种编程环境，它结合了高级图像处理库AVW、内部开发的...

Brachial artery flow-mediated vasodilation is increasingly used as a measure of endothelial function. High resolution ultrasound provides a noninvasive method to observe this flow-mediated vasodilation by monitoring the diameter of the artery over time following a transient flow stimulus. Since hundreds of ultrasound images are required to continuously monitor brachial diameter for the 2-3 min dur...

肱动脉血流介导的血管舒张功能越来越多地被用作内皮功能的衡量指标。高分辨率超声通过监测短暂血流刺激后动脉直径随时间的变化，提供了一种非侵入性方法来观察这种血流介导的血管舒张。由于需要数百张超声图像来持续监测肱动脉直径达2-3分钟...

A linearly scanned three-dimensional (3-D) ultrasound imaging system is considered. The transducer array is initially oriented along the x axis and aimed in the y direction. After being tilted by an angle /spl theta/ about the x axis, and then swiveled by an angle /spl phi/ about the y axis, it is translated in the z direction, in steps of size d, to acquire a series of parallel two-dimensional (2...

考虑一种线性扫描三维超声成像系统。换能器阵列最初沿x轴方向，指向y方向。在绕x轴倾斜角度/spl theta/，然后绕y轴旋转角度/spl phi/后，它以步长d沿z方向平移，以获取一系列平行的二维图像...

A procedure is described for deformable boundary detection of medical tools, called stents, in angiographic images. A stent is a surgical stainless steel coil that is placed in the artery in order to improve blood circulation in regions where a stenosis has appeared. Assuming initially a set of three-dimensional (3-D) models of stents and using perspective projection of various deformations of the...

描述了一种用于血管造影图像中医疗工具（称为支架）的可变形边界检测程序。支架是一种外科不锈钢线圈，放置在动脉中，以改善出现狭窄区域的血流循环。假设初始有一组三维（3-D）支架模型，并使用各种变形的透视投影...

Magnetic resonance spectroscopic imaging (MRSI) requires a relatively long time to sample k-space (the spatial frequency domain), effectively lowpass filtering the resulting reconstructed image. Ringing is especially problematic when a region of interest (ROI) is close to a bright region outside the ROI, since the bright region tends to create a ringing artifact into the ROI due to the lowpass nat...

磁共振波谱成像（MRSI）需要相对较长的时间来采样k空间（空间频率域），从而对重建图像进行低通滤波。当感兴趣区域（ROI）靠近ROI外的明亮区域时，振铃问题尤其严重，因为明亮区域由于低通特性容易在ROI中产生振铃伪影...

Motion artefact suppression remains an active topic in MRI. In this paper, the authors suggest that certain nonrigid, or spatially variant, characteristics of motion of an object can be represented by extending the work of Mitsa et al. (1989). This empirical extension uses a ghost distortion transfer function (GTDF) applied to the k-space (frequency domain) data. The authors demonstrate the variet...

运动伪影抑制仍然是MRI中的一个活跃话题。本文中，作者提出，通过扩展Mitsa等人(1989)的工作，可以表示物体运动的某些非刚性或空间变化的特性。这种经验扩展使用了一个应用于k空间（频域）数据的鬼影畸变传递函数（GTDF）。作者展示了多种...