【作者】 梁斌；

【导师】 陈武凡；

【作者基本信息】 第一军医大学 ， 生物医学工程， 2004， 博士

【摘要】 近十年来，随着小波与分形理论研究的不断成熟，基于小波变换与分形的图像压缩成为图像编码的研究热点。同时，医学影像学也取得了突飞猛进的发展，新的成像方式层出不穷。在此趋势下，本论文进行了基于小波变换与分形理论的医学图像编码的研究，旨在提出新的适合医学图像特点的编码方法。论文的主要研究内容如下： 1)提出了基于小波变换的预测四叉树图像编码算法，该算法属于带内编码与带间编码的混合。将同一频带内系数分块，随比特面的移动，将块由大到小进行四叉树分裂，克服了固定大小块的不足。另外在编码中加入了预测过程，实现对块的裁剪，使块的形状更符合实际的情况。熵编码采用了基于上下文的算术编码，提出了四种上下文编码模型，可以灵活调整以合适不同医学图像的特点。 2)针对三维体成像设备产生的序列图像，提出了模糊聚类优化的序列图像快速分形压缩算法，它是一种基于单帧的序列图像帧间分形压缩算法。该算法首先使用LBG方法对序列图像组成的搜索空间样本集进行初始化，然后将模糊聚类优化方法应用于对样本集的软分类，匹配时通过用类内搜索取代全局搜索，将分形编码过程聚焦在最有效的局部范围内，从而减少了匹配次数，降低编码时间。相同运算环境下的仿真实验结果说明，在不影响信噪比和压缩比的前提下，与传统序列图像分形压缩算法相比，我们的OFC算法编码速度可提高大约5倍。更多还原

【Abstract】 With the maturity of the wavelet and fractal theory in recent years, image coding schemes based on these two theories have become the research focus. At the same time, medical imaging techniques have achieved tremendous advances, which provide various kinds of new image types that effectively increase the accuracy of the diagnosing of human diseases. Under this trend, the main research efforts are on putting forward new medical image coding schemes for telemedicine based on wavelet and fractal theories, which specially fit in with clinical requirements. The main contributions of my work are as follows:1) Proposing a novel Wavelet Image Coding scheme based on Predictive Quadtree-Split. This method hybridizes the intra-band and inter-band coding. Wavelet coefficients in same band are partitioned into many blocks, and the blocks split according to quadtree with the moving of bitplane. This kind of dynamic block spirting can overcome some shortcomings brought by fixed block size. At the same time, the algorithm introduces a predictive coding procedure to truncate the block and make the block’s shape fit in with the actual image. A context based arithmetic coder is adopted in entropy coding, and four different sets of models are designed for the arithmetic coder which could be adjust adaptively according to different kinds of medical images.2) Presenting a fast fraction coding scheme for fast sequence medical image coding based on the principle of OFC(Optimal Fuzzy Clustering). The algorithm makes use of LBG method to initialize the searching space, then fuzzy clustering algorithm is applied to give a soft classification of the searching space. Global searching is replaced by searching in the resulting classes and fractal coding is focused on the most effective local area, thus the new algorithm significantly reduce the matching times and coding complexity. Simulation resultsshow the computation time is reduced by 5 times compared with the traditional sequence image fractal coding schemes at the same PSNR level.更多还原