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Free‐breathing abdominal T 1 mapping using an optimized MR fingerprinting sequence
Author(s) -
Riel Max H. C.,
Yu Zidan,
Hodono Shota,
Xia Ding,
Chandarana Hersh,
Fujimoto Koji,
Cloos Martijn A.
Publication year - 2021
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.4531
Subject(s) - imaging phantom , robustness (evolution) , artificial intelligence , computer science , computer vision , flip angle , algorithm , mathematics , physics , magnetic resonance imaging , optics , chemistry , medicine , biochemistry , radiology , gene
In this work, we propose a free‐breathing magnetic resonance fingerprinting (MRF) method that can be used to obtain B 1 + ‐robust quantitative T 1 maps of the abdomen in a clinically acceptable time. A three‐dimensional MRF sequence with a radial stack‐of‐stars trajectory was implemented, and its k‐space acquisition ordering was adjusted to improve motion‐robustness in the context of MRF. The flip angle pattern was optimized using the Cramér–Rao Lower Bound, and the encoding efficiency of sequences with 300, 600, 900 and 1800 flip angles was evaluated. To validate the sequence, a movable multicompartment phantom was developed. Reference multiparametric maps were acquired under stationary conditions using a previously validated MRF method. Periodic motion of the phantom was used to investigate the motion‐robustness of the proposed sequence. The best performing sequence length (600 flip angles) was used to image the abdomen during a free‐breathing volunteer scan. When using a series of 600 or more flip angles, the estimated T 1 values in the stationary phantom showed good agreement with the reference scan. Phantom experiments revealed that motion‐related artifacts can appear in the quantitative maps and confirmed that a motion‐robust k‐space ordering is essential. The in vivo scan demonstrated that the proposed sequence can produce clean parameter maps while the subject breathes freely. Using this sequence, it is possible to generate B 1 + ‐robust quantitative maps of T 1 and B 1 + next to M 0 ‐weighted images under free‐breathing conditions at a clinically usable resolution within 5 min.