PARALLEL MRSI RECON WITH ARBITRARY TRAJECTORIES USING K-SPACE SPARSE MATRICES

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 使用非笛卡尔k空间轨迹（例如螺旋）的快速成像技术已被实施，以减少与体积MRSI相关的长扫描时间。通过利用多个接收线圈采集部分k空间数据并使用每个线圈的灵敏度曲线的知识进行重建，可以进一步减少扫描时间。利用笛卡尔网格上的k空间数据，可以使用基于图像域的SENSE算法或基于k空间域的GRAPPA算法来实现重建。对于非笛卡尔k空间数据，可以使用基于图像域的迭代SENSE算法或基于k空间域的PARS算法进行重建。虽然有效，这些非笛卡尔k空间数据重建方法遭受长的计算时间。在这项工作中，我们提出了一个并行MRSI重建方法与任意轨迹使用k-空间稀疏矩阵（KSPA）。该算法通过利用线圈灵敏度定义的卷积核的紧凑性来实现减少的计算时间和存储器需求。使用该算法的重建证明使用欠采样的螺旋k空间数据从体内研究与不同的减少因素。 方法和讨论： 为了编码化学位移信息，具有螺旋k空间轨迹的快速MRSI在重复的螺旋轨迹上采样数据点。利用KSPA算法，使用第一螺旋轨迹上的k空间数据计算重建矩阵，然后将其应用于剩余螺旋轨迹上的k空间数据，以估计重复笛卡尔网格上的完全采样的k空间数据。由于重构矩阵仅需要计算一次，因此可以显著减少重构时间。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Fast imaging techniques using non- Cartesian k-space trajectories, e.g. spiral, have been implemented to reduce the long scan times associated with volumetric MRSI. The scan time can be further reduced by acquiring partial k-space data with multiple receiving coils and reconstruct using the knowledge of each coil's sensitivity profile. With k-space data on a Cartesian grid, reconstruction can be achieved using image-domain based SENSE algorithm or k-space-domain based GRAPPA algorithm. For non-Cartesian k-space data, image-domain based iterative SENSE algorithm or k-space-domain based PARS algorithm can be used for the reconstruction. Although effective, these non-Cartesian k-space data reconstruction methods suffer from long computing times. In this work, we propose a parallel MRSI reconstruction method with arbitrary trajectories using k-space sparse matrices (KSPA). The algorithm achieves reduced computing times and memory requirements by taking advantage of the compactness of the convolution kernel defined by the coil sensitivity. Reconstruction using this algorithm is demonstrated using undersampled spiral k-space data from an in-vivo study with different reduction factors. Methods and Discussion: To encode chemical shift information, fast MRSI with spiral k-space trajectories samples data points on repeated spiral trajectories. With the KSPA algorithm, the reconstruction matrix is calculated using k-space data on the first spiral trajectory and then applied to k-space data on the remaining spiral trajectories to estimate the fully sampled k-space data on repeated Cartesian grids. Since the reconstruction matrix only needs to be computed once, significant reconstruction time can be reduced.