• Ouri Cohen, Assaf Tal, and Oded Gonen.
• Department of Radiology, New York University, New York, New York, USA; Biomedical Engineering, Columbia University, New York, New York, USA.
• Magn Reson Med. 2014 Oct 1; 72 (4): 923-33.

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° RF pulse following the T-HSI encoding block provides variable, arbitrary echo time (TE) to eliminate undesirable short T2 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 ≈ 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 T2 and J-coupled metabolites with higher SNR.Copyright © 2013 Wiley Periodicals, Inc.

26 keywords...

hide…