Premium
Diffusion tensor imaging using partial Fourier STEAM MRI with projection onto convex subsets reconstruction
Author(s) -
Rieseberg Susanne,
Merboldt KlausDietmar,
Küntzel Matthias,
Frahm Jens
Publication year - 2005
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.20572
Subject(s) - diffusion mri , projection (relational algebra) , fourier transform , tensor (intrinsic definition) , fourier analysis , regular polygon , diffusion , nuclear magnetic resonance , mathematics , magnetic resonance imaging , physics , mathematical analysis , geometry , medicine , radiology , algorithm , thermodynamics
Diffusion‐weighted single‐shot STEAM MRI allows for diffusion mapping of the human brain without sensitivity to resonance offset effects. In order to compensate for its inherently lower SNR and speed than echo‐planar imaging, this work describes the use of partial Fourier encoding in combination with image reconstruction by the projection onto convex subsets algorithm. The method overcomes phase distortions in diffusion‐weighted partial Fourier acquisitions that disturb the conjugate complex symmetry of k ‐space and preclude the use of respective reconstruction techniques. In comparison with full Fourier encoding and a static flip angle for the STEAM readout pulses, experimental results at 2.9 T demonstrate a gain in relative SNR per unit time by 20% for 5/8 phase encoding with optimized variable flip angles. Simultaneously, the imaging time is reduced from about 670 ms (80 echoes) to 440 ms (50 echoes). Current implementations at 2 × 2 mm 2 in‐plane resolution comprise a protocol for clinical anisotropy studies (12 diffusion‐encoding gradient directions at 1000 s mm −2 ) covering 18 sections of 4‐mm thickness within a measurement time of 8.5 min (5 averages) and a version optimized for fiber tracking using 24 gradient directions and 38 sections of 2‐mm thickness yielding a measurement time of 29.5 min (4 averages). Magn Reson Med 54:486–490, 2005. © 2005 Wiley‐Liss, Inc.