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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
Author(s) -
Baudrexel Simon,
Reitz Sarah C.,
Hof Stephanie,
Gracien RenéMaxime,
Fleischer Vinzenz,
Zimmermann Hilga,
Droby Amgad,
Klein Johannes C.,
Deichmann Ralf
Publication year - 2016
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3460
Subject(s) - flip angle , electromagnetic coil , sensitivity (control systems) , excitation , proton , radiofrequency coil , computational physics , physics , nuclear magnetic resonance , variable (mathematics) , point (geometry) , constant (computer programming) , optics , analytical chemistry (journal) , chemistry , mathematics , mathematical analysis , computer science , geometry , magnetic resonance imaging , electronic engineering , nuclear physics , chromatography , medicine , quantum mechanics , engineering , radiology , programming language
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.