冠状动脉系统CT图像去噪研究

发布时间：2018-05-01 03:04

本文选题：冠状动脉系统 + 计算机断层图像　；参考：《天津工业大学》2017年硕士论文

【摘要】：在冠状动脉医学影像诊断领域中,低剂量计算机断层扫描技术(Low Dose Computed Tomography,LDCT)受到越来越多的学者和医学研究人员的关注。但是,剂量降低会伴随着的心脏重建图像退化,影响临床诊断。因此,在保证冠状动脉CT成像质量的同时又减少有害的辐射剂量具有重要的科学意义和应用前景。本文研究偏微分方程方法在冠状动脉系统低剂量CT图像去噪中的应用。在各向异性扩散模型基础上,提出了改进的4邻域偏微分降噪算法。针对PM模型的病态性,利用中值滤波后的冠状动脉投影图像代替原始图像梯度模值,并根据局部区域内各扩散方向的相邻像素的相关度差异性定义了归一权梯度函数,得到PMG模型,从而有效地实现噪声快速平滑和断层图像中冠状动脉分支细节的较好保留;考虑到冠状动脉投影图像在各阶段的统计特性变化规律和传统扩散门限选取困难的情况,应用当前邻域内梯度的绝对偏差均值计算图像的梯度门限值,并定义了时变扩散函数,得到PMC模型。该模型能够自适应调节噪声平滑和血管走支保留之间的平衡;将PMG模型与PMC模型进行融合,得到PMGC模型,以进一步提高降噪算法处理后的冠状动脉图像质量水平。最后,计算机仿真和冠状动脉CT扫描数据实验结果显示,改进算法能够获得更高质量的重建图像,并具有较好的运算效率,为临床分析提供了有效的数据支持。
[Abstract]:In the field of coronary artery medical imaging diagnosis, low Dose Computed tomography (LDCT) has attracted more and more scholars and medical researchers' attention. However, dose reduction can be associated with cardiac reconstruction image degradation, affecting clinical diagnosis. Therefore, it has important scientific significance and application prospect to ensure the quality of coronary artery CT imaging while reducing the harmful radiation dose. In this paper, the application of partial differential equation method in low dose CT image denoising of coronary artery system is studied. Based on the anisotropic diffusion model, an improved 4-neighborhood partial differential denoising algorithm is proposed. In view of the ill-condition of PM model, the coronary artery projection image after median filtering is used to replace the original image gradient, and the normalized weight gradient function is defined according to the difference of the correlation degree of adjacent pixels in each diffusion direction in the local region. The PMG model is obtained, which can effectively smooth the noise and preserve the details of coronary artery branch in the image. Considering the variation of the statistical characteristics of coronary artery projection images in various stages and the difficulty in selecting the traditional diffusion threshold, the gradient threshold value of the image is calculated by using the absolute deviation mean of the gradient in the current neighborhood, and the time-varying diffusion function is defined. The PMC model is obtained. The model can adaptively adjust the balance between noise smoothing and vascular branch retention, and fuse PMG model with PMC model to obtain PMGC model, so as to further improve the image quality of coronary artery after noise reduction algorithm. Finally, computer simulation and coronary artery CT scan data experiment results show that the improved algorithm can obtain higher quality reconstruction images, and has a better computational efficiency, which provides an effective data support for clinical analysis.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R541.4;R816.2;TP391.41

【参考文献】