用于CT和MRI图像的轮廓波变换双水印算法

目的：为解决CT与MRI图像版权侵权与恶意破坏问题,通过结合轮廓波变换与斑点检测技术,提出一种基于轮廓波变换自动选择感兴趣区域（ROI）的双水印算法。方法：该算法通过斑点检测与奇异值分解,选取医学图像轮廓波低频域与诊断最相关的位置作为ROI,在ROI生成零水印图像用于保护图像的完整性,并将ROI生成的零水印与版权水印共同嵌入图像的非感兴趣区域。结果：该双水印算法与其他双水印算法相比,载体医学图像遭受攻击后的不可见性有很大提升,结构相似度达到94%以上。结论：斑点检测轮廓波双水印算法对常规攻击与几何攻击具有较好的鲁棒性,且对于载体医学图像视觉质量有明显提升。     

一种健壮透明盲检测的三重嵌入图像水印时域算法

提出了一种基于模数运算的三重嵌入图像水印时域算法。将图像划分为若干节,对每节最大、第二、第三等三个灰度值分别采用模2法嵌入水印。由于采用三重水印嵌入算法,因而有效地提高了健壮性。实验证明,该算法透明性好,健壮性较强,可盲水印检测,能抵抗裁剪、加噪、滤波、转换等攻击。     

彩色图像二值化算法及应用

目的:利用灰度/色度谱平坦化技术及彩色图像质量评价作为支撑,在给出严格的图像(含彩色图像)二值化概念的基础后,提出一种新的彩色图像二值化算法,此算法可以对图像进行挖掘和隐藏,并且还提出一种新的23位彩色图像格式。方法:采用Zadeh-X变换算法,保证变换前后的图像具有相同的平均亮度值,并利用保值二值化变换算法增加变换后的二值化图像色彩亮度。结果:提高了图像的对比度和可分辨性,使二值化图像增加了一种新的图像格式:23位位图格式,这种格式使图像的信息量大大减少,可便于压缩。结论:这种彩色二值化扩展了传统意义的黑白图像二值化的概念,使二值化的应用更加广泛,并且利用此方法还能对图像进行隐藏和挖掘,新的图像格式还可用来并提高了对比度,使图像的信息量大大减少,以便用于压缩。     

一种脑MRA图像自动分割算法及其在图像导引神经外科中的应用

图像导引神经外科技术是在神经外科手术过程中减小患者刨伤的有效方法。在这种方法中，医学图像分割质量的好坏直接影响着手术过程的准确性。本研究提出了一种新的基于MRA图像的自动分割算法，这种算法通过各向异性滤波，统计阈值分割，数学形态学滤波，和基于边界距离场的活动轮廓模型来对MRA图像进行自动分割和分割结果的可视化。数据实验表明用这种算法对MRA图像进行分割的结果可以有效地用于图像导引神经外科，并且算法具有一定的鲁棒性。     

基于小波包变换的数字水印方法

提出了一种基于小波分析的盲图像水印方法,本方法.利用小波包分解在图像和音频文件中构造信息冗余,嵌入的水印为二值图像,提取时不需原始信息和水印信息.对比试验结果证明,该方法能够抵抗常见的水印攻击,在经过加噪、平滑、缩放和压缩等信号处理后仍能保持稳健.     

基于模糊空间的骨膜显微图像识别

医学图像的目标描述往往是带有模糊性的。随着计算技术的发展,模糊逻辑理论渐被引入医学图像处理的理论研究和实际应用中。而采色医学图像和灰度图像具有不同的空间表达和模糊描述方式,其分析处理方法也有区别。我们阐述了一种基于模糊空间的彩色色骨膜显微图像识别,提出用模糊算法进行彩色图像增强、特征撮和自动分割,完成了对骨膜显微图像中的骨细胞的分割过程。通过对多幅实际采集的彩色图像进行处理,实验结果结果表明是一种     

基于互信息的多分辨率三维脑图像配准方法

在3D多模医学图像的配准方法中，最大互信息法精度高，鲁棒性强，使用范围广，本文将归一化互信息作为相似性测度，采用不同的采样范围和采样子集，使用Powell多参数优化法和Brent一维搜索算法对3DCT，MR和PET脑图像进行了刚体配准，为了加快配准速度，使用了多分辨的金字塔方法，对PET图像采用基于坐标的阈值选取方法对图像进行分割预算法，消除了大部分放射状背景伪影，美国万德贝尔大学对结果进行的评估证明配准精度可达亚体元级。     

基于互信息医学刚性图像配准方法的研究

目的:基于互信息的配准方法是医学图像配准领域的重要方法,具有鲁棒性,精度高等优点。本文探究医学刚性图像配准的有效算法和关键技术。方法:基于互信息配准方法,利用Powell多参数算法和改进的PV插值算法,得到两幅图像之间的最大互信息和最佳配准参数。结果:二维磨牙CT图像配准实验表明,配准速度快,精度提高,验证了插值方法的有效性。结论:方法和算法可提高配准速度,能有效抑制互信息目标函数的局部极值。     

从X线图像中提取标志物几何数据的方法研究

从X线图像中提取特定标志物的几何数据是基于X线图像手术导航系统中的一项关键技术。这些几何数据是X线图像几何变形校正及C形臂相机校准的基础。我们提出一种聚类算法用于特征数据的提取。该算法集成了自适应取阈算法和一种快速准连通分量标记算法的优势，仅需对原始灰度图像进行一次扫描处理即可提取出所需的特征数据。算法执行效率高、鲁棒性好。     

基于先验知识和MRF随机场模型的医学图像弹性配准方法

本研究提出了一种新的基于先验知识的弹性配准算法，首次把马尔可夫模型应用于图像的弹性配准方面。为了把关于变形场的先验知识融合到弹性配准过程中，本研究以马尔可夫随机场模型作为理论框架，以B样条为基函数来构造弹性变形模型，以弹性模型的B样条系数作为待估参数，以原图像和变形图像作为已知条件，把弹性变形模型和关于变形场的先验知识有机的融合到了马尔可夫随机场模型中，实现了一种基于变形场先验知识的弹性配准算法。这种新算法因为有变形场的先验知识，所以可以得到更好配准结果。本研究以变形场的平滑作为先验知识，可以有效改善局部极值的状况，提高算法的可靠性和鲁棒性。本研究分别对2D和3D图像进行了试验，试验结果证明了这种算法的有效性。     

Hiding clinical information in medical images: A new high capacity and reversible data hiding technique

A new high capacity and reversible data hiding scheme for e-healthcare applications has been presented in this paper. Pixel to Block (PTB) conversion technique has been used as an effective and computationally efficient alternative to interpolation for the cover image generation to ensure reversibility of medical images. A fragile watermark and Block Checksum (computed for each 4 × 4 block) have been embedded in the cover image for facilitating tamper detection and tamper localization, and hence content authentication at receiver. The EPR, watermark data and checksum data has been embedded using Intermediate Significant Bit Substitution (ISBS) to avoid commonly used LSB removal/replacement attack. Non-linear dynamics of chaos have been put to use for encrypting the Electronic Patient Record (EPR)/clinical data and watermark data for improving the security of data embedded. The scheme has been evaluated for perceptual imperceptibility and tamper detection capability by subjecting it to various image processing and geometric attacks. Experimental results reveal that the proposed system besides being completely reversible is capable of providing high quality watermarked images for fairly high payload. Further, it has been observed that the proposed technique is able to detect and localise the tamper. A comparison of the observed results with that of some state-of-art schemes show that our scheme performs better.     

Watermark Compression in Medical Image Watermarking Using Lempel-Ziv-Welch (LZW) Lossless Compression Technique

In teleradiology, image contents may be altered due to noisy communication channels and hacker manipulation. Medical image data is very sensitive and can not tolerate any illegal change. Illegally changed image-based analysis could result in wrong medical decision. Digital watermarking technique can be used to authenticate images and detect as well as recover illegal changes made to teleradiology images. Watermarking of medical images with heavy payload watermarks causes image perceptual degradation. The image perceptual degradation directly affects medical diagnosis. To maintain the image perceptual and diagnostic qualities standard during watermarking, the watermark should be lossless compressed. This paper focuses on watermarking of ultrasound medical images with Lempel-Ziv-Welch (LZW) lossless-compressed watermarks. The watermark lossless compression reduces watermark payload without data loss. In this research work, watermark is the combination of defined region of interest (ROI) and image watermarking secret key. The performance of the LZW compression technique was compared with other conventional compression methods based on compression ratio. LZW was found better and used for watermark lossless compression in ultrasound medical images watermarking. Tabulated results show the watermark bits reduction, image watermarking with effective tamper detection and lossless recovery.     

嵌入式零树小波编码在医学图像压缩中的应用

目的:对嵌入式零树小波编码算法提出改进,实现CT图像压缩。方法:分析嵌入式零树小波编码的原理和算法并探讨小波基的选择,针对嵌入式零树小波编码算法的缺点进行改进,研究设计实现改进算法的程序,进行CT图像压缩。结果:在相同压缩比的情况下,改进的嵌入式零树小波编码算法获得的峰值信噪比比原有算法获得的峰值信噪比高,特别是在高压缩比的情况下,图像的主观质量和峰值信噪比都有了较大的改善。结论:改进的嵌入式零树小波编码算法比原有EZW算法更加优越,能够满足医学图像的传输和诊断要求。     

基于Pocket PC的医学图像浏览器

目的：利用绑定精简版．NET开发框架的Visual Studio 2003．NET编程平台开发一个基于Pocket PC的医学图像浏览器。材料与方法：智能移动设备客户端通过安装应用程序，实现对Web服务器端医学信息的查询、提取、更新，以及对医学图像的浏览和处理。结果：在基于Windows CE的智能移动设备端，通过采用C／S（client／server）构架，利用医学图像浏览器，初步实现了医学图像的无线远程共享。结论：与大多数传统的PACS相比，基于Pocket PC的移动PACS组建简单，易于安装和使用。利用其独有的移动上网功能，突破了医学图像浏览的时间性和地域性的限制。     

A Region-Based Lossless Watermarking Scheme for Enhancing Security of Medical Data

This paper presents a lossless watermarking scheme in the sense that the original image can be exactly recovered from the watermarked one, with the purpose of verifying the integrity and authenticity of medical images. In addition, the scheme has the capability of not introducing any embedding-induced distortion in the region of interest (ROI) of a medical image. Difference expansion of adjacent pixel values is employed to embed several bits. A region of embedding, which is represented by a polygon, is chosen intentionally to prevent introducing embedding distortion in the ROI. Only the vertex information of a polygon is transmitted to the decoder for reconstructing the embedding region, which improves the embedding capacity considerably. The digital signature of the whole image is embedded for verifying the integrity of the image. An identifier presented in electronic patient record (EPR) is embedded for verifying the authenticity by simultaneously processing the watermarked image and the EPR. Combining with fingerprint system, patient’s fingerprint information is embedded into several image slices and then extracted for verifying the authenticity.     

基于最佳截断嵌入码块编码和离散小波变换的医学图像复合压缩算法

根据医学图像信息相对集中的特点,提出了一种基于最佳截断嵌入码块编码和离散小波变换的医学图像任意形状感兴趣区域复合压缩方法,通过对图像感兴趣区域和背景区采用不同的编码方式,提高了医学图像压缩比,并确保了医学图像感兴趣区域的高质量重建。实验表明:该方法在重建图像质量和压缩比方面均达到了较好的性能。     

基于边缘特征点匹配的临床X线自动全景成像研究

目的：本文提出了一种基于边缘特征点匹配的X线自动全景成像方法。方法：一,采用双正交小波变换与Canny算子相结合的算法实现X线图像的有效边缘提取,并通过矩阵计算得到特征点;二,利用Pearson相关系数和随机抽样一致算法来建立图像之间的相关性和匹配性;三,利用渐入渐出的融合算法实现X线无缝全景成像。结果：该算法可快速高质量地实现骨科临床无外部特征的X线图像序列全景拼接。结论：该算法对弱对比度的X线图像序列全景拼接具有很强的鲁棒性,允许X线图像序列之间存在较小的图像旋转和缩放差异,有助于减少X线使用剂量,具有较强的应用价值。     

Image reconstruction on PI-lines by use of filtered backprojection in helical cone-beam CT

Recently, we have derived a general formula for image reconstruction from helical cone-beam projections. Based upon this formula, we have also developed an exact algorithm for image reconstruction on PI-line segments from minimum data within the Tam-Danielsson window. This previous algorithm can be referred to as a backprojection-filtration algorithm because it reconstructs an image by first backprojection of the data derivatives and then filtration of the backprojections on PI-line segments. In this work, we propose an alternative algorithm, which reconstructs an image by first filtering the modified data along the cone-beam projections of the PI-lines onto the detector plane and then backprojecting the filtered data onto PI-line segments. Therefore, we refer to this alternative algorithm as the filtered-backprojection algorithm. A preliminary computer-simulation study was performed for validating and demonstrating this new algorithm. Furthermore, we derive a practically useful expression to accurately compute the derivative of the data function for image reconstruction. The proposed filtered-backprojection algorithm can reconstruct the image within any selected ROI inside the helix and thus can handle naturally the long object problem and the super-short scan problem. It can also be generalized to reconstruct images from data acquired with other scanning configurations such as the helical scan with a varying pitch.     

Medical image compression using DCT-based subband decomposition and modified SPIHT data organization

OBJECTIVE: The work proposed a novel bit-rate-reduced approach for reducing the memory required to store a remote diagnosis and rapidly transmission it. METHOD: In the work, an 8x8 Discrete Cosine Transform (DCT) approach is adopted to perform subband decomposition. Modified set partitioning in hierarchical trees (SPIHT) is then employed to organize data and entropy coding. The translation function can store the detailed characteristics of an image. A simple transformation to obtain DCT spectrum data in a single frequency domain decomposes the original signal into various frequency domains that can further compressed by wavelet-based algorithm. In this scheme, insignificant DCT coefficients that correspond to a particular spatial location in the high-frequency subbands can be employed to reduce redundancy by applying a proposed combined function in association with the modified SPIHT. RESULTS AND CONCLUSIONS: Simulation results showed that the embedded DCT-CSPIHT image compression reduced the computational complexity to only a quarter of the wavelet-based subband decomposition, and improved the quality of the reconstructed medical image as given by both the peak signal-to-noise ratio (PSNR) and the perceptual results over JPEG2000 and the original SPIHT at the same bit rate. Additionally, since 8x8 fast DCT hardware implementation being commercially available, the proposed DCT-CSPIHT can perform well in high speed image coding and transmission.