Gao Yun, Strakowski Stephen M, Reeves Stanley J, Hetherington Hoby P, Chu Wen-Jang, Lee Jing-Huei
Center for Imaging Research, University of Cincinnati College of Medicine, OH 45267, USA.
Magn Reson Med. 2006 Jun;55(6):1265-71. doi: 10.1002/mrm.20905.
Long acquisition times, low resolution, and voxel contamination are major difficulties in the application of magnetic resonance spectroscopic imaging (MRSI). To overcome these difficulties, an online-optimized acquisition of k-space, termed sequential forward array selection (SFAS), was developed to reduce acquisition time without sacrificing spatial resolution. A 2D proton MRSI region of interest (ROI) was defined from a scout image and used to create a region of support (ROS) image. The ROS was then used to optimize and obtain a subset of k-space (i.e., a subset of nonuniform phase encodings) and hence reduce the acquisition time for MRSI. Reconstruction and processing software was developed in-house to process and reconstruct MRSI using the projections onto convex sets method. Phantom and in vivo studies showed that good-quality MRS images are obtainable with an approximately 80% reduction of data acquisition time. The reduction of the acquisition time depends on the area ratio of ROS to FOV (i.e., the smaller the ratio, the greater the time reduction). It is also possible to obtain higher-resolution MRS images within a reasonable time using this approach. MRSI with a resolution of 64 x 64 is possible with the acquisition time of the same as 24 x 24 using the traditional full k-space method.
采集时间长、分辨率低和体素污染是磁共振波谱成像（MRSI）应用中的主要难题。为克服这些难题，开发了一种在线优化的k空间采集方法，称为顺序前向阵列选择（SFAS），以在不牺牲空间分辨率的情况下减少采集时间。从定位图像定义二维质子MRSI感兴趣区域（ROI），并用于创建支持区域（ROS）图像。然后使用ROS来优化并获取k空间的一个子集（即非均匀相位编码的一个子集），从而减少MRSI的采集时间。内部开发了重建和处理软件，以使用凸集投影法处理和重建MRSI。模型和体内研究表明，可获得高质量的MRS图像，同时数据采集时间可减少约80%。采集时间的减少取决于ROS与视野（FOV）的面积比（即该比例越小，时间减少越多）。使用这种方法还可以在合理的时间内获得更高分辨率的MRS图像。使用传统的全k空间方法，采集时间与24×24相同的情况下，有可能获得分辨率为64×64的MRSI。
