Optimized in-phase and opposed-phase MR imaging for accurate detection of small fat or water fractions: theoretical considerations and experimental application in emulsions
- نوع فایل : کتاب
- زبان : انگلیسی
- مؤلف : Verena Ballweg · Hanne Wojtczyk · Nadine Roth · Petros Martirosian · Fabian Springer · Fritz Schick
- چاپ و سال / کشور: 2011
Description
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 spoiledGRE-sequences and on relaxation properties of water and fat components. For quantification, signals were corrected for T 2.-decay, T 1- decay, and signal contributions from double bonds. Theoretical results were exemplarily compared to measurements at 1.5T on emulsions with either lowwater 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 (Sfat and Swater , 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 B1 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
Magn Reson Mater Phy (2011) 24:167–178 DOI 10.1007/s10334-011-0248-9Received: 6 September 2010 / Revised: 9 March 2011 / Accepted: 9 March 2011 / Published online: 27 March 201
