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T 1 measurements in the human myocardium: The effects of magnetization transfer on the SASHA and MOLLI sequences
Author(s) -
Robson Matthew D.,
Piechnik Stefan K.,
Tunnicliffe Elizabeth M.,
Neubauer Stefan
Publication year - 2013
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.24867
Subject(s) - magnetization transfer , saturation (graph theory) , nuclear magnetic resonance , relaxation (psychology) , t2 relaxation , physics , chemistry , medicine , magnetic resonance imaging , mathematics , radiology , combinatorics
Purpose Quantitative mapping of the native T 1 of the heart using the modified look‐locker inversion recovery (MOLLI) technique provides high quality diagnostic information without requiring contrast agents. Previous work has considered the effects of T 2 relaxation on MOLLI T 1 measurements, finding that the T 1 measured by MOLLI is biased, and that Saturation‐recovery single‐Shot Acquisition generates a more precise T 1 . However, despite detailed experiments and simulation the exact relaxation times observed in vivo remain unexplained, but might be due to magnetization transfer (MT). Methods We used an MT simulation based on the Bloch‐McConnell equations to evaluate the most common MOLLI and saturation‐recovery single‐shot acquisition sequence variants. Results For myocardial tissue we find that the T 1 measured by saturation‐recovery single‐shot acquisition is insensitive to MT and T 2 , whereas MT reduces the T 1 measured by MOLLI (>10%) in addition to the effects due to T 2 relaxation. Conclusions The consequences of this T 1 underestimation by MOLLI are relevant. Increases in the actual T 1 and T 2 and decreases in MT will all result in an increase in T 1 measured by MOLLI. Myocardial infarction demonstrates increased native T 1 and T 2 and decreased MT, indicating that these biases enhance the sensitivity of MOLLI to detect this and possibly other cardiovascular disease states. Magn Reson Med 70:664–670, 2013. © 2013 Wiley Periodicals, Inc .