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k ‐Space filtering in 2D gradient‐echo breath‐hold hyperpolarized 3 He MRI: Spatial resolution and signal‐to‐noise ratio considerations
Author(s) -
Wild Jim M.,
Paley Martyn N.J.,
Viallon Magalie,
Schreiber Wolfgang G.,
van Beek Edwin J.R.,
Griffiths Paul D.
Publication year - 2002
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.10134
Subject(s) - image resolution , k space , dephasing , flip angle , fourier transform , imaging phantom , nuclear magnetic resonance , signal to noise ratio (imaging) , signal (programming language) , physics , optics , computer science , magnetic resonance imaging , medicine , quantum mechanics , radiology , programming language
In this work some of the factors that can influence the signal‐to‐noise ratio (SNR) and spatial resolution in MR images of inhaled hyperpolarized gases are systematically addressed. In particular, the effects of RF depletion of longitudinal polarization and image gradient diffusion dephasing were assessed in terms of their contribution to a k ‐space filter. By means of theoretical simulations and a novel method of experimental validation using a variable transverse magnetization of the 1 H signal, systematic quantitative and qualitative investigations of the effects of k ‐space filtering intrinsic to imaging of hyperpolarized gas were made. A 2D gradient‐echo image is considered for a range of flip angles with centric, sequential, and half‐Fourier Cartesian phase‐encoding strategies, and the results are assessed in terms of SNR and spatial resolution in the reconstructed images. Centric phase encoding was found to give the best SNR at higher flip angles, with a trade‐off in spatial resolution compared to sequential phase encoding. A half‐Fourier approach potentially offers increased SNR through the use of higher flip angles without compromising the spatial resolution, which is comparable to that achieved with sequential encoding. Magn Reson Med 47:687–695, 2002. © 2002 Wiley‐Liss, Inc.