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Quantitative T 1 and proton density mapping with direct calculation of radiofrequency coil transmit and receive profiles from two‐point variable flip angle data

2016; Wiley; Volume: 29; Issue: 3 Linguagem: Inglês

10.1002/nbm.3460

1099-1492

Simon Baudrexel, Sarah C. Reitz, Stephanie Michelle Hof, René‐Maxime Gracien, Vinzenz Fleischer, Hilga Zimmermann, Amgad Droby, Johannes Klein, Ralf Deichmann,

Advanced NMR Techniques and Applications

Quantitative T 1 mapping of brain tissue is frequently based on the variable flip angle (VFA) method, acquiring spoiled gradient echo (GE) datasets at different excitation angles. However, accurate T 1 calculation requires a knowledge of the sensitivity profile B 1 of the radiofrequency (RF) transmit coil. For an additional derivation of proton density (PD) maps, the receive coil sensitivity profile (RP) must also be known. Mapping of B 1 and RP increases the experiment duration, which may be critical when investigating patients. In this work, a method is presented for the direct calculation of B 1 and RP from VFA data. Thus, quantitative maps of T 1 , PD, B 1 and RP can be obtained from only two spoiled GE datasets. The method is based on: (1) the exploitation of the linear relationship between 1/PD and 1/ T 1 in brain tissue and (2) the assumption of smoothly varying B 1 and RP, so that a large number of data points can be fitted across small volume elements where B 1 and RP are approximately constant. The method is tested and optimized on healthy subjects. Copyright © 2016 John Wiley & Sons, Ltd.