基于分数阶非高斯模型的超声图像散粒噪声特性分析

医学超声图像在应用中遇到的一个重要问题是如何消除图像中由于散射现象的相干本质而引起的多径乘性散粒噪声. 稳定分布可以用来描述重拖尾非高斯尖峰脉冲信号和噪声.本文利用一种散粒噪声模型,通过分析与稳定分布建模,提出了一种基于稳定分布模型的超声图象散粒噪声建模的新方法.仿真结果表明,该建模方法能更好地描述乘性散粒噪声.     

Quantum Noise Suppression in X-ray Images using Fuzzy 2-D Wiener Filter

The noisy images are caused by decreasing quantity of the produced X-ray due to the deformation of the X-ray tube’s anode. While obtaining the image from low quantity X-ray, shot noise or quantum noise occurs, and this decreases the quality of the image. The aim of this study is to define the novel method called as Fuzzy 2-D Weiner filter (FWF-2D), which suppresses the shot noise from noisy image by avoiding any harm to the image details. With this filtering technique, it is possible to preserve the sharp-edge and the details of the image without any damage during suppressing the noise from images. FWF-2D is one of the best techniques to suppress the corrupted quantum noises due to damaged X-ray tube. The fuzzy rules used in this filter are aimed to distinguish noise pixels from image ones, and the Wiener Filter is working to remove noise pixels distinguished by these fuzzy rules. It is then possible to obtain clean images from damaged X-ray tubes by using FWF-2D technique.     

Impulse Noise Removal from Medical Images by Two Stage Quaternion Vector Median Filter

This paper presents a two-stage impulse noise removal filter from medical images. Quaternion is used to represent differences of two pixels. The pixels are sorted and assigned a rank based on the aggregated sum of pixel differences with other pixels inside the filtering window. The central pixel is considered as corrupted by an impulse if its rank is bigger than a predefined rank and the minimum difference between it and other pixels in the four edge direction inside the window is larger than a predefined threshold. The noisy pixel is replaced by output of vector median filter implemented using quaternion. For color images, both intensity and chromaticity components are used. Quaternion processes color images as single unit rather than as separated color channels. This preserves the correlation and three dimensional vector natures of the color channels. For grayscale medical images, the same algorithm is implemented by using the intensity difference between two pixels. Experimental results show improved performance of the proposed filter in suppressing the impulse noise while retaining the original image details comparing against other well-known filters.     

Adaptive Real-Time Removal of Impulse Noise in Medical Images

Noise is an important factor that degrades the quality of medical images. Impulse noise is a common noise caused by malfunctioning of sensor elements or errors in the transmission of images. In medical images due to presence of white foreground and black background, many pixels have intensities similar to impulse noise and hence the distinction between noisy and regular pixels is difficult. Therefore, it is important to design a method to accurately remove this type of noise. In addition to the accuracy, the complexity of the method is very important in terms of hardware implementation. In this paper a low complexity de-noising method is proposed that distinguishes between noisy and non-noisy pixels and removes the noise by local analysis of the image blocks. All steps are designed to have low hardware complexity. Simulation results show that in the case of magnetic resonance images, the proposed method removes impulse noise with an acceptable accuracy.     

基于混合滤波的避投影数据微分螺旋锥束CT重建

目的 本文将综合现有经典CT重建算法的优点,提出一种新的基于Hilbert-Ramp混合滤波的避投影数据微分螺旋锥束CT优质重建算法.方法 新算法采用Katsevich算法框架.将现有FDK类型算法和Katsevich算法的不同优点有机地融合.完全回避投影数据中关于探测器坐标变量的直接微分运算.结果 实验结果表明本文提出的新算法理论分析的正确性,有效地提高了螺旋锥柬CT重建图像的分辨率,减少了重建伪影.结论 文中提出的基于Hilbert-Ramp混合滤波的避投影数据微分螺旋锥束CT重建公式是对Katsevich重建公式的重要改进.同时Ramp滤波的引入可以针对不同的临床应用进行优化设计.     

冷冻电镜成像中噪声的滤波方法进展

1 冷冻电镜的发展背景 在人类基因组测定之后,人们发现仅从基因组序列的角度无法完整、系统地阐明生物体的功能,因此,研究以蛋白质为主体的生物大分子三维结构和功能之间的关系成为现代生命科学的一个重要研究领域,尤其是生物大分子高分辨率三维结构的研究甚至原子水平结构的研究[1-2].     

Suppression of Impulse Noise in Medical Images with the Use of Fuzzy Adaptive Median Filter

A new rule based fuzzy filter for removal of highly impulse noise, called Rule Based Fuzzy Adaptive Median (RBFAM) Filter, is aimed to be discussed in this paper. The RBFAM filter is an improved version of Adaptive Median Filter (AMF) and is presented in the aim of noise reduction of images corrupted with additive impulse noise. The filter has three stages. Two of those stages are fuzzy rule based and last stage is based on standard median and adaptive median filter. The proposed filter can preserve image details better then AMF while suppressing additive salt&pepper or impulse type noise. In this paper, we placed our preference on bell-shaped membership function instead of triangular membership function in order to observe better results. Experimental results indicates that the proposed filter is improvable with increased fuzzy rules to reduce more noise corrupted images and to remove salt and pepper noise in a more effective way than what AMF filter does.     

基于SVR插值的FBMC系统时变信道估计

与正交频分复用（OFDM）技术不同,5G候选技术之一的滤波器组多载波（FBMC）技术由于添加了原型滤波器的设计,各个载波之间不需要完全正交,也不需要插入循环前缀作为保护等操作。然而由于引入了固有的虚部干扰,相应的信道估计也更复杂。良好的信道估计和插值算法对于时刻跟踪时变信道响应的变化是十分必要的。本文提出了一种基于SVR插值的FBMC时变信道估计方法,采用辅助导频消除FBMC系统的虚部干扰,然后基于SVR进行时变信道插值。该算法利用已知的导频符号,在存在传输衰落及非线性噪声的情况下,使用SVR回归拟合估计信道响应系数。在仿真中,将信道矢量建模为单径慢时变瑞利衰落信道。结果表明,与传统算法相比,该方法在运算效率损失不大的情况下,对FBMC信道估计的效果有极大的改善,估计精度更高。     

MR Images Restoration With the Use of Fuzzy Filter Having Adaptive Membership Parameters

A new fuzzy adaptive median filter is presented for the noise reduction of magnetic resonance images corrupted with heavy impulse (salt and pepper) noise. In this paper, we have proposed a Fuzzy Adaptive Median Filter with Adaptive Membership Parameters (FAMFAMP) for removing highly corrupted salt and pepper noise, with preserving image edges and details. The FAMFAMP filter is an improved version of Adaptive Median Filter (AMF) and is presented in the aim of noise reduction of images corrupted with additive impulse noise. The proposed filter can preserve image details better than AMF while suppressing additive salt and pepper or impulse type noise. In this paper, we placed our preference on bell-shaped membership function with adaptive parameters instead of triangular membership function without variable coefficients in order to observe better results.     

基于Hermite微分算子的水平集MR图像分割方法

本文介绍一种基于Hermite微分算子用于MR图像分割的水平集方法。该方法采用Hermite微分算子来代替传统一阶差分算子。即在水平集曲线演化时函数微分用像素点的二阶邻域差值求得，而不是传统方法由一阶邻域决定。实验结果表明，对于相同的分割过程，运用了Hermite微分算子的水平集方法，其分割结果更加精确。尤其是对于由噪声等因素所引起的退化图像。其分割效果明显优于传统方法，而运算速度与传统方法相差无几。     

基于噪声相关性的惩罚加权最小二乘算法在低剂量数字乳腺层析成像中的应用

目的对投影数据方差的精确建模并结合DBT平板探测系统的噪声相关性构建精准噪声模型下的基于噪声相关性的惩 罚加权最小二乘算法在低剂量乳腺层析成像图像中的应用。方法首先对投影数据进行量子噪声和电子噪声建模,使以往常用 的近似噪声模型精准化,然后构建基于噪声相关性的惩罚加权最小二乘算法用于投影数据恢复;最后对处理后的投影数据采用 滤波反投影算法进行重建。结果对不同剂量下ACR标准体模数据进行处理得到的重建结果噪声明显降低,细节对比度提 高。恢复投影数据的重建图像与原始数据重建图像相比,CNRs和LSNRs提升了约3.6倍。结论对投影数据噪声抑制效果明 显,重建DBT图像质量有很大的提升。     

利用圆周探测和Gabor滤波器鉴别血管结构的新方法

为了自动判别造影图像中的血管终端、血管段、血管分支和两血管交叉等结构模式,提出了Gabor滤波器结合圆周探测的新方法.利用该方法进行血管的逐点顺序识别时,不易受血管径向强度变化和血管弯曲的影响.研究的意义在于:一方面能够为二维造影网像中血管树的量化描述和重建血管三结构提供有益的帮助,另一方面能够为血管疾病诊断提供基本的线索.实验分别用模拟图像和血管造影网像验证该方法,获得了满意的效果.     

一种基于二维匹配滤波器的掌纹识别算法

在掌纹识别算法中,基于Gabor滤波器和方向编码方法得到了广泛的研究和应用,但是此类方法一般使用Gabor滤波器提取特征,易受噪声和散焦等外界因素的影响。针对此问题,本文提出了一种基于匹配滤波器的算法。该算法使用二维匹配滤波器提取图像特征,采用双方向编码（DOC）匹配方法表征特征之间的相似度。实验结果表明,该算法对于噪声、散焦和平移等干扰都具有很好的鲁棒性,验证了该算法的可行性。     

Novel Design of Low Noise Preamplifier for Medical Ultrasound Transducers

A novel design of low noise amplifier for medical ultrasound transducers is described in this paper. Unlike conventional low noise preamplifiers, this design proposes a new circuit configuration which has electronically adjustable matching resistance that allows the preamplifier to be compatible with a variety of medical ultrasound transducers. The design employs current feedback operational amplifier to enhance the gain-bandwidth independence and improve the design slew rate. Simulation results show that the proposed design has very low output noise voltage spectral density and the level of this noise does not increase when its tunable matching resistance is increased or decreased.     

腓肠肌羽状角的超声自动测量

目的本文提出腓肠肌羽状角的一种基于超声射频信号的互相关自动测量方法。方法本文采集正常人体腓肠肌与仿真
腓肠肌体模的超声射频信号,重建超声图像,确定肌束的搜索起始点,采用互相关算法自动跟踪肌束膜和肌腱膜,绘出肌束线和
肌腱膜线,计算两线之夹角,即为腓肠肌羽状角,并检验自动与手动两种测量方法的可重复性及一致性。结果利用互相关自动
测量方法可准确测量出体膜中仿真肌束羽状角,其测量值的均值与理论值之间的差异小于1°。利用互相关自动测量方法与手
动测量方法获得的正常人体腓肠肌羽状角分别为20.48°±0.47°与21.49°±1.79°,两种方法的变异系数CV值均小于3%,均方根
误差均小于1°。Bland-Altman差值法分析结果表明两种方法的一致性良好。结论本文所提出的腓肠肌羽状角自动测量方法
是基于超声射频信号的互相关算法,其测量结果与手动测量结果基本一致,在较严重的噪声情况下仍可跟踪腓肠肌的肌束走
向,自动测量腓肠肌的羽状角。
     

下腔静脉滤器置入术后倾斜和穿孔的CT随访结果

目的CT（computedtomography）评估下腔静脉滤器（inferiorvellacavafilter,IVCF）置入后滤器倾斜和牢孔的临床价值。方法2010年1月至2012年10月对行IVCF置入术后的78例患者予CT随访,回顾性评估IVCF置入期间随访滤器异常的CT表现。结果78例患者滤器置入时间为12天一l6年,滤器发生倾斜的共22例,17例倾斜角大于15°。滤器侧方倾斜的平均倾斜角为9°±2°,15例大于15°：前后方倾斜的平均倾斜角为10°±3°,10例大于15°;9例滤器仅表现在一个方向上倾斜角度大于15°;8例滤器双向倾斜角度均大于15°。CT图像发现下腔静脉穿孔0—1级共71例,3—4级共7例,其中0级,68例,1级3例;2级3例;3级4例。结论CT能够较清晰地呈现下腔静脉滤器全貌并检测异常,可作为对滤器置入术后并发症及随访的有效方法。     

三维可视化在婴幼儿髋关节发育不良超声影像学中的应用

目的：通过三维重建技术对婴幼儿髋关节及其周围解剖结构骨形态特征进行重建与二维超声图像拟合以及图像的匹配,从而实现对婴幼儿髋关节发育状况的正确评价。方法选取婴幼儿新鲜尸体标本20具（其中男10具,女10具）,行64排螺旋CT骨盆扫描,将测量数据应用Amira 5.4.5软件建立髋关节三维图像,观察其骨形态特征及彼此的空间形态位置关系并进行二维超声平面的确定及超声图像的测量。结果二维超声髋关节冠状切面标准图像α、β角测量结果分别为（59.5±0.8）°、（56.2±0.5）°,三维虚拟现实图像α、β角测量结果分别为（61.5±0.4）°、（53.3±0.4）°,两者比较,差异均无统计学意义（均P〉0.05）。结论三维可视化图像能够清晰显示髋关节骨形态结构并进行二维超声平面的确定及超声图像的测量,验证了二维超声法可以准确地评价婴幼儿髋关节发育状况,二维超声法可以作为婴幼儿发育性髋关节脱位首选的检查方法。     

Design of a Biorthogonal Wavelet Transform Based R-Peak Detection and Data Compression Scheme for Implantable Cardiac Pacemaker Systems

Bradycardia can be modulated using the cardiac pacemaker, an implantable medical device which sets and balances the patient’s cardiac health. The device has been widely used to detect and monitor the patient’s heart rate. The data collected hence has the highest authenticity assurance and is convenient for further electric stimulation. In the pacemaker, ECG detector is one of the most important element. The device is available in its new digital form, which is more efficient and accurate in performance with the added advantage of economical power consumption platform. In this work, a joint algorithm based on biorthogonal wavelet transform and run-length encoding (RLE) is proposed for QRS complex detection of the ECG signal and compressing the detected ECG data. Biorthogonal wavelet transform of the input ECG signal is first calculated using a modified demand based filter bank architecture which consists of a series combination of three lowpass filters with a highpass filter. Lowpass and highpass filters are realized using a linear phase structure which reduces the hardware cost of the proposed design approximately by 50%. Then, the location of the R-peak is found by comparing the denoised ECG signal with the threshold value. The proposed R-peak detector achieves the highest sensitivity and positive predictivity of 99.75 and 99.98 respectively with the MIT-BIH arrhythmia database. Also, the proposed R-peak detector achieves a comparatively low data error rate (DER) of 0.002. The use of RLE for the compression of detected ECG data achieves a higher compression ratio (CR) of 17.1. To justify the effectiveness of the proposed algorithm, the results have been compared with the existing methods, like Huffman coding/simple predictor, Huffman coding/adaptive, and slope predictor/fixed length packaging.     

Non-invasive Health Status Detection System Using Gabor Filters Based on Facial Block Texture Features

Blood tests allow doctors to check for certain diseases and conditions. However, using a syringe to extract the blood can be deemed invasive, slightly painful, and its analysis time consuming. In this paper, we propose a new non-invasive system to detect the health status (Healthy or Diseased) of an individual based on facial block texture features extracted using the Gabor filter. Our system first uses a non-invasive capture device to collect facial images. Next, four facial blocks are located on these images to represent them. Afterwards, each facial block is convolved with a Gabor filter bank to calculate its texture value. Classification is finally performed using K-Nearest Neighbor and Support Vector Machines via a Library for Support Vector Machines (with four kernel functions). The system was tested on a dataset consisting of 100 Healthy and 100 Diseased (with 13 forms of illnesses) samples. Experimental results show that the proposed system can detect the health status with an accuracy of 93 %, a sensitivity of 94 %, a specificity of 92 %, using a combination of the Gabor filters and facial blocks.     

反激式开关电源的变压器电磁兼容性设计

对于带变压器拓扑结构的开关电源来说,变压器的电磁兼容性(EMC)设计对整个开关电源的EMC水平影响较大。本文以一款反激式开关电源为例,阐述了其传导共模干扰的产生、传播机理。根据噪声活跃节点平衡的思想,提出了一种新的变压器EMC设计方法。通过实验验证,与传统的设计方法相比,该方法对传导电磁干扰(EMI)的抑制能力更强,且能降低变压器的制作成本和工艺复杂程度。本方法同样适用于其他形式的带变压器拓扑结构的开关电源。