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- Title
Optimized in-phase and opposed-phase MR imaging for accurate detection of small fat or water fractions: theoretical considerations and experimental application in emulsions.
- Authors
Ballweg, Verena; Wojtczyk, Hanne; Roth, Nadine; Martirosian, Petros; Springer, Fabian; Schick, Fritz
- Abstract
Object: To optimize strategies and measurement parameters for quantification of small fat and water fractions (<10%) in mixtures of both components by 4-point in-phase and opposed-phase gradient-echo imaging and to compare theoretical results with in-vitro experiments using emulsions. Materials and methods: Theoretical analysis was based on steady-state signal equations for spoiled GRE-sequences and on relaxation properties of water and fat components. For quantification, signals were corrected for T2*-decay, T1-decay, and signal contributions from double bonds. Theoretical results were exemplarily compared to measurements at 1.5 T on emulsions with either low water or fat fractions (0.5-10%) using spoiled 2D- and 3D-GRE-sequences. Excitation flip angle was varied in order to determine suitable values for sensitive detection of small fat/water fractions. Results: Theoretical results and measurements correlated well, especially for 3D-sequences. Maximal sensitivity to a small signal fraction ( S and S, respectively), was provided at the Ernst angle of the lower concentrated component. For 2D-sequences, the nominal flip angle had to be increased for compensation of slice profile effects and B inhomogeneities. IP- and OP-echoes are recommended to be acquired in separate measurements with smallest possible receiver bandwidth to increase SNR/unit-time. Lowest detectable fat/water concentration in emulsions under typical conditions regarding spatial resolution and measuring time was approximately 1%. Conclusion: Using IP/OP-imaging with optimized parameters and post-processing, a sensitive and reliable detection of small fat/water fractions larger than 1% is possible in emulsions.
- Subjects
MAGNETIC resonance imaging; EMULSIONS; ELECTRON spin echoes; BANDWIDTHS; THREE-dimensional imaging
- Publication
MAGMA: Magnetic Resonance Materials in Physics, Biology & Medicine, 2011, Vol 24, Issue 3, p167
- ISSN
0968-5243
- Publication type
Article
- DOI
10.1007/s10334-011-0248-9