针对应用迭代软阈值(IST)算法对基于低秩稀疏矩阵(L+S,low rank and sparse)分解模型的动态磁共振成像(MRI)图像进行重建存在重建精度一般和重建速度慢的问题,提出在矩阵L+S分解模型的基础上引入全变分(TV)正则项,达到进一步去噪声和去...针对应用迭代软阈值(IST)算法对基于低秩稀疏矩阵(L+S,low rank and sparse)分解模型的动态磁共振成像(MRI)图像进行重建存在重建精度一般和重建速度慢的问题,提出在矩阵L+S分解模型的基础上引入全变分(TV)正则项,达到进一步去噪声和去伪影,提高重建精度目的;利用非精确增广拉格朗日算法(IALM)达到快速重建的目的。通过对心脏灌注动态MRI成像和心电影MRI成像的仿真实验表明:对于L+S低秩稀疏矩阵分解模型的重建,IALM比IST算法速度更快,精度更高;模型引入TV正则项后再利用IALM重建,重建速度虽然比之前的IALM有所降低,但依然优于IST算法,并且重建精度高于之前的IALM。在L+S分解模型中引入TV正则项提高了MRI重建精度,运用IALM进行求解加快了重建速度,结合TV正则项和IALM达到了快速、高精度重建的目的。展开更多
Recently, dictionary learning(DL) based methods have been introduced to compressed sensing magnetic resonance imaging(CS-MRI), which outperforms pre-defined analytic sparse priors. However, single-scale trained dictio...Recently, dictionary learning(DL) based methods have been introduced to compressed sensing magnetic resonance imaging(CS-MRI), which outperforms pre-defined analytic sparse priors. However, single-scale trained dictionary directly from image patches is incapable of representing image features from multi-scale, multi-directional perspective, which influences the reconstruction performance. In this paper, incorporating the superior multi-scale properties of uniform discrete curvelet transform(UDCT) with the data matching adaptability of trained dictionaries, we propose a flexible sparsity framework to allow sparser representation and prominent hierarchical essential features capture for magnetic resonance(MR) images. Multi-scale decomposition is implemented by using UDCT due to its prominent properties of lower redundancy ratio, hierarchical data structure, and ease of implementation. Each sub-dictionary of different sub-bands is trained independently to form the multi-scale dictionaries. Corresponding to this brand-new sparsity model, we modify the constraint splitting augmented Lagrangian shrinkage algorithm(C-SALSA) as patch-based C-SALSA(PB C-SALSA) to solve the constraint optimization problem of regularized image reconstruction. Experimental results demonstrate that the trained sub-dictionaries at different scales, enforcing sparsity at multiple scales, can then be efficiently used for MRI reconstruction to obtain satisfactory results with further reduced undersampling rate. Multi-scale UDCT dictionaries potentially outperform both single-scale trained dictionaries and multi-scale analytic transforms. Our proposed sparsity model achieves sparser representation for reconstructed data, which results in fast convergence of reconstruction exploiting PB C-SALSA. Simulation results demonstrate that the proposed method outperforms conventional CS-MRI methods in maintaining intrinsic properties, eliminating aliasing, reducing unexpected artifacts, and removing noise. It can achieve comparable performance of reconstruction with the state-of-the-art methods even under substantially high undersampling factors.展开更多
文摘针对应用迭代软阈值(IST)算法对基于低秩稀疏矩阵(L+S,low rank and sparse)分解模型的动态磁共振成像(MRI)图像进行重建存在重建精度一般和重建速度慢的问题,提出在矩阵L+S分解模型的基础上引入全变分(TV)正则项,达到进一步去噪声和去伪影,提高重建精度目的;利用非精确增广拉格朗日算法(IALM)达到快速重建的目的。通过对心脏灌注动态MRI成像和心电影MRI成像的仿真实验表明:对于L+S低秩稀疏矩阵分解模型的重建,IALM比IST算法速度更快,精度更高;模型引入TV正则项后再利用IALM重建,重建速度虽然比之前的IALM有所降低,但依然优于IST算法,并且重建精度高于之前的IALM。在L+S分解模型中引入TV正则项提高了MRI重建精度,运用IALM进行求解加快了重建速度,结合TV正则项和IALM达到了快速、高精度重建的目的。
基金Project supported by the National Natural Science Foundation of China(Nos.61175012 and 61201422)the Natural Science Foundation of Gansu Province of China(No.1208RJ-ZA265)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.2011021111-0026)the Fundamental Research Funds for the Central Universities of China(Nos.lzujbky-2015-108 and lzujbky-2015-197)
文摘Recently, dictionary learning(DL) based methods have been introduced to compressed sensing magnetic resonance imaging(CS-MRI), which outperforms pre-defined analytic sparse priors. However, single-scale trained dictionary directly from image patches is incapable of representing image features from multi-scale, multi-directional perspective, which influences the reconstruction performance. In this paper, incorporating the superior multi-scale properties of uniform discrete curvelet transform(UDCT) with the data matching adaptability of trained dictionaries, we propose a flexible sparsity framework to allow sparser representation and prominent hierarchical essential features capture for magnetic resonance(MR) images. Multi-scale decomposition is implemented by using UDCT due to its prominent properties of lower redundancy ratio, hierarchical data structure, and ease of implementation. Each sub-dictionary of different sub-bands is trained independently to form the multi-scale dictionaries. Corresponding to this brand-new sparsity model, we modify the constraint splitting augmented Lagrangian shrinkage algorithm(C-SALSA) as patch-based C-SALSA(PB C-SALSA) to solve the constraint optimization problem of regularized image reconstruction. Experimental results demonstrate that the trained sub-dictionaries at different scales, enforcing sparsity at multiple scales, can then be efficiently used for MRI reconstruction to obtain satisfactory results with further reduced undersampling rate. Multi-scale UDCT dictionaries potentially outperform both single-scale trained dictionaries and multi-scale analytic transforms. Our proposed sparsity model achieves sparser representation for reconstructed data, which results in fast convergence of reconstruction exploiting PB C-SALSA. Simulation results demonstrate that the proposed method outperforms conventional CS-MRI methods in maintaining intrinsic properties, eliminating aliasing, reducing unexpected artifacts, and removing noise. It can achieve comparable performance of reconstruction with the state-of-the-art methods even under substantially high undersampling factors.
