Diffusion tensor imaging using partial Fourier STEAM MRI with projection onto convex subsets reconstruction
✍ Scribed by Susanne Rieseberg; Klaus-Dietmar Merboldt; Matthias Küntzel; Jens Frahm
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- English
- Weight
- 449 KB
- Volume
- 54
- Category
- Article
- ISSN
- 0740-3194
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✦ Synopsis
Abstract
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.