Volume 19, Issue 7

Based on the theory of approximation, this paper presents a unified analysis of interpolation and resampling techniques. An important issue is the choice of adequate basis functions. The authors show that, contrary to the common belief, those that perform best are not interpolating. By opposition to traditional interpolation, the authors call their use generalized interpolation; they involve a prefiltering step when correctly applied. The authors explain why the approximation order inherent in any basis function is important to limit interpolation artifacts. The decomposition theorem states that any basis function endowed with approximation order ran be expressed as the convolution of a B spline of the same order with another function that has none. This motivates the use of splines and spline-based functions as a tunable way to keep artifacts in check without any significant cost penalty. The authors discuss implementation and performance issues, and they provide experimental evidence to support their claims.

基于逼近理论，本文对插值和重采样技术进行了统一分析。一个重要问题是选择合适的基函数。作者表明，与普遍看法相反，表现最佳的基函数并非插值函数。与传统插值相反，作者称他们的使用为广义插值；当正确应用时，它涉及一个预滤波步骤。作者解释了任何基函数固有的逼近阶对于限制插值伪影的重要性。分解定理指出，任何具有逼近阶的基函数都可以表示为相同阶的B样条与另一个没有逼近阶的函数的卷积。这促使使用样条和基于样条的函数作为一种可调谐的方式来控制伪影，而无需显著增加成本。作者讨论了实现和性能问题，并提供了实验证据来支持他们的主张。

The authors propose a novel imaging system useful in dermatology, more precisely, for the follow-up of patients with an increased risk of skin cancer. The system consists of a Pentium PC equipped with an RGB frame grabber, a three-chip charge coupled devices (CCD) camera controlled by the serial port and equipped with a zoom lens and a halogen annular light source. Calibration of the imaging syste...

作者提出了一种新颖的成像系统，可用于皮肤科，更准确地说是用于皮肤癌风险增加患者的随访。该系统由一台配备RGB帧抓取器的奔腾PC、一台通过串口控制并配备变焦镜头和环形卤素光源的三芯片电荷耦合器件(CCD)相机组成。成像系统的校准...

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...

Considers a novel three-dimensional (3-D) visualization technique based on surface flattening for virtual colonoscopy. Such visualization methods could be important in virtual colonoscopy because they have the potential for noninvasively determining the presence of polyps and other pathologies. Further, the authors demonstrate a method that presents a surface scan of the entire colon as a cine, an...

探讨一种基于表面展平的新型三维可视化技术用于虚拟结肠镜。此类可视化方法在虚拟结肠镜检查中可能很重要，因为它们有可能无创地确定息肉和其他病变的存在。此外，作者展示了一种方法，将整个结肠的表面扫描呈现为电影，...

Magnetic resonance imaging using the echo planar imaging (EPI) technique is particularly sensitive to main (B/sub 0/) field inhomogeneities. The primary effect is geometrical distortion in the phase encoding direction. Here, the authors present a method based on the conjugate gradient algorithm to correct for this geometrical distortion, by solving the EPI imaging equation. Two versions are presen...

使用回波平面成像（EPI）技术的磁共振成像对主磁场（B/sub 0/）不均匀性特别敏感。主要影响是相位编码方向上的几何失真。本文提出了一种基于共轭梯度算法的方法，通过求解EPI成像方程来校正这种几何失真。给出了两个版本...

Equalizing image noise has been shown to be an important step in automatic detection of microcalcifications in digital mammograms. In this study, an accurate adaptive approach for noise equalization is presented and investigated. No additional information obtained from phantom recordings is improved in the method, which makes the approach robust and independent of film type and film development characteristics. Furthermore, it is possible to apply the method on direct digital mammograms as well. In this study, the adaptive approach is optimized by investigating a number of alternative approaches to estimate the image noise. The estimation of high-frequency noise as a function of the grayscale is improved by a new technique for dividing the grayscale in sample intervals and by using a model for additive high-frequency noise. It is shown that the adaptive noise equalization gives substantially better detection results than does a fixed noise equalization. A large database of 245 digitized mammograms with 341 clusters was used for evaluation of the method.

研究表明，均衡图像噪声是数字乳腺X线图像中微钙化自动检测的重要步骤。本文提出并研究了一种精确的自适应噪声均衡方法。该方法无需从体模记录中获取额外信息，使得该方法稳健且独立于胶片类型和胶片显影过程。

In many medical applications, the number of available two-dimensional (2-D) images is always insufficient. Therefore, the three-dimensional (3-D) reconstruction must be accomplished by appropriate interpolation methods to fill gaps between available image slices. Here, the authors propose a morphology-based algorithm to interpolate the missing data. The proposed algorithm consists of several steps...

在许多医学应用中，可用的二维图像数量往往不足。因此，必须通过适当的插值方法填补图像切片之间的间隙，以完成三维重建。本文作者提出了一种基于形态学的算法来插值缺失数据。该算法包括几个步骤……

The morphological skeleton interpolation (MSI) algorithm is presented. It is an efficient, shape-based interpolation method used for interpolating slices in a three-dimensional (3-D) binary object. It is based on morphological skeletonization, which is used for two-dimensional (2-D) slice representation. The proposed morphological skeleton matching process provides translation, rotation, and scali...

提出了形态学骨架插值(MSI)算法。它是一种高效的、基于形状的插值方法，用于对三维(3-D)二值对象中的切片进行插值。该方法基于形态学骨架化，用于二维(2-D)切片表示。所提出的形态学骨架匹配过程提供了平移、旋转和缩放...

To define a healing function based on parameters measured on digitized images of wounds, and to use it to compare the rate of healing of two skin graft donor sites, one treated with petrolatum gauze (Pg) and the other with a topical preparation containing alginates (A). Digital photographs of donor sites (depth 0.6 mm) taken every two days between day 6 and day 12 were analyzed blind using the sam...

为了定义基于伤口数字化图像测量参数的愈合函数，并用该函数比较两种皮肤移植供体部位的愈合率，一种使用凡士林纱布（Pg）处理，另一种使用含藻酸盐的局部制剂（A）处理。对深度0.6毫米的供体部位，在第6天至第12天每两天拍摄数码照片，并进行盲法分析，使用相同的...

Magnetic resonance images are reconstructed from digitized raw data, which are collected in the spatial-frequency domain (also called k-space). Occasionally, single or multiple data points in the k-space data are corrupted by spike noise, causing striation artifacts in images. Thresholding methods for detecting corrupted data points can fail because of small alterations, especially for data points...

磁共振图像是从数字化原始数据重建的，这些数据在空间频率域（也称为k空间）中采集。偶尔，k空间数据中的单个或多个数据点会被尖峰噪声破坏，导致图像中出现条纹伪影。用于检测损坏数据点的阈值方法可能会因为微小的变化而失败，特别是对于数据点...

Because spiral magnetic resonance imaging (MRI) is more robust to motion artifacts than echo planar imaging (EPI), spiral imaging method is more suitable in real-time imaging applications where dynamic processes are to be observed. The major hurdle to use spiral imaging method in real-time applications is its slow reconstruction speed. Since spiral trajectories do not sample data on rectilinear gr...

由于螺旋磁共振成像（MRI）相比回波平面成像（EPI）对运动伪影更具鲁棒性，因此螺旋成像方法更适用于需要观察动态过程的实时成像应用。在实时应用中使用螺旋成像方法的主要障碍是其重建速度较慢。由于螺旋轨迹不是按矩形网格采样数据...

Three-dimensional (3-D) reconstructions of coronary bypass grafts performed from X-ray angiographic images may become increasingly important for the investigation of damaging mechanical stresses imposed to these vessels by the cyclic movement of the heart. Contrary to what the authors had experienced with coronary arteries, appreciable reconstruction artifacts frequently occur with grafts. In orde...

基于X射线血管造影图像进行的冠状动脉旁路移植术三维重建对于研究心脏周期性运动对这些血管施加的有害机械应力可能变得越来越重要。与作者在冠状动脉上的经验相反，旁路移植术中经常出现明显的重建伪影。为了...