基于敏感度仿真与全变分约束的并行磁共振成像算法研究

项目名称： 基于敏感度仿真与全变分约束的并行磁共振成像算法研究

项目编号： No.30800254

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 建筑科学

项目作者： 冯衍秋

作者单位： 南方医科大学

项目金额： 20万元

中文摘要： 磁共振成像是当前临床医学影像学的重要检查手段,但由于数据采集时间仍较长，易受各种伪影干扰，其应用受到诸多限制。并行磁共振成像利用阵列线圈的空间敏感度编码降低成像所必需的梯度编码步数，从而获得更快的扫描速度，成为缩短磁共振成像检查时间最有潜力的研究方向。并行磁共振成像研究目标是保证图像质量的前提下，实现尽可能大的加速倍数，而高质量的数据重建是实现该目标的重要保证。并行磁共振图像重建是一个典型的逆问题，当成像数据较少时，系统矩阵成为一个严重病态的矩阵，造成图像重建精度降低，不能为临床所接受；而且，由于敏感度分布受到多种因素的影响，很难事先得到准确的系统矩阵。针对以上难题，我们提出从阵列线圈的物理模型出发，通过电磁仿真技术获得先验的敏感度分布信息，导入基于低分辨率图像的敏感度估计框架，以减少系统矩阵误差；从重建问题的数学模型出发，引入非局部全变分约束，及非笛卡尔稀疏重建方法，以提升大加速因子下并行磁共振成像重建质量。实验结果表明，所提出的方法能够进一步提高磁共振扫描速度，并很好的保证了高加速因子下并行磁共振图像的重建质量。

中文关键词： 并行磁共振成像；图像重建；全变分；敏感度

英文摘要： Magnetic resonance imaging (MRI), one of the main means for medical imaging, is susceptible to kinds of artifacts for its long time of data collection. Consequently, its clinical application is kept within certain limits. Parallel MRI use spatial encoding from sensitivity map of array coils to supplement the gradient encoding and thereby accerlates the data scanning. Parallel MRI is becoming into the most potential approcach to shortening the time for MR image acquitization. One important research in parallel MRI is to get both high image quality and large accerlateing factor as possible, which is accomplished by the optimal reconstruction algorithm. The reconstruction of parallel MR data is a typical inverse problem. For little data can be available with large accerlate factor, the system matrix of the inverse problem is serious ill-conditioning. As a result, low-quality image is reconstructed. Furthermore, the accurate sensitivity map is difficult to acquire because the sensisitivy is influenced by many complicate factors. To solve these problems, we proposed to get the prior information of sensitivity using electromagnetic simulation from the physical model of array coil to reduce the error for systme matrix. At the same time, we will research on the reconstuction algorithm with total variation constraints to get high image quality when large accerlating factor is chosen.The experiments demonstrated that the proposed method accelerated the data scanning and veritified the exactly same image accuracy with large acceleration.

英文关键词： parallel MRI;image reconstruction;total variation;sensitivity