Three-Dimensional Hadamard-Encoded Proton Spectroscopic Imaging in the Human Brain Using Time-Cascaded Pulses at 3 Tesla
Three-Dimensional Hadamard-Encoded Proton Spectroscopic Imaging in the Human Brain Using Time-Cascaded Pulses at 3 Tesla
复制标题
DOI：
10.1002/mrm.25022
复制
发表时间：
2014-10-01
影响因子：
3.3
通讯作者：
Gonen, Oded
中科院分区：
文献类型：
--
作者：
Cohen, Ouri;Tal, Assaf;Gonen, Oded
为了降低三维阿达玛光谱成像的比吸收率(SAR)和化学位移(CSD)，并保持其点扩展函数(PSF)的优点，提出了一种2D纵向、1D横向HSI(L-HSI，T-HSI)序列的3D混合序列，并在3T(T)的体模和人脑中进行了演示。不是将每个选择性阿达玛射频(RF)脉冲与其N个单片分量叠加，而是在时间上级联它们，允许N倍更强的梯度，从而降低CSD。结果与相同重复时间、空间分辨率和网格大小的3D化学位移成像相比，该序列的信噪比(SNR)提高了10-15%，信号泄漏减少了8-16%。肌醇、胆碱、肌酸和N-乙酰天冬氨酸的体内信噪比分别为13.6、22+/-7、24+/-8和31+/-14。结论新的混合HSI序列提供了更好的定位PSF，降低了CSD，降低了3T的SAR。短而可变的TE允许以更高的SNR获取短的T-2和J-偶联代谢物。Magn Reson Med 72：923-933,2014。(C)2013年威利期刊公司。
PurposeTo reduce the specific-absorption-rate (SAR) and chemical shift displacement (CSD) of three-dimensional (3D) Hadamard spectroscopic imaging (HSI) and maintain its point spread function (PSF) benefits.MethodsA 3D hybrid of 2D longitudinal, 1D transverse HSI (L-HSI, T-HSI) sequence is introduced and demonstrated in a phantom and the human brain at 3 Tesla (T). Instead of superimposing each of the selective Hadamard radiofrequency (RF) pulses with its N single-slice components, they are cascaded in time, allowing N-fold stronger gradients, reducing the CSD. A spatially refocusing 180 degrees RF pulse following the T-HSI encoding block provides variable, arbitrary echo time (TE) to eliminate undesirable short T-2 species' signals, e.g., lipids.ResultsThe sequence yields 10-15% better signal-to-noise ratio (SNR) and 8-16% less signal bleed than 3D chemical shift imaging of equal repetition time, spatial resolution and grid size. The 13 6, 22 +/- 7, 24 +/- 8, and 31 +/- 14 in vivo SNRs for myo-inositol, choline, creatine, and N-acetylaspartate were obtained in 21 min from 1 cm(3) voxels at TE approximate to 20 ms. Maximum CSD was 0.3 mm/ppm in each direction.ConclusionThe new hybrid HSI sequence offers a better localized PSF at reduced CSD and SAR at 3T. The short and variable TE permits acquisition of short T-2 and J-coupled metabolites with higher SNR. Magn Reson Med 72:923-933, 2014. (c) 2013 Wiley Periodicals, Inc.