• Shohei Fujita, Akifumi Hagiwara, Masaaki Hori, Marcel Warntjes, Koji Kamagata, Issei Fukunaga, Christina Andica, Tomoko Maekawa, Ryusuke Irie, Mariko Yoshida Takemura, Kanako Kunishima Kumamaru, Akihiko Wada, Michimasa Suzuki, Yutaka Ozaki, Osamu Abe, and Shigeki Aoki.
• Department of Radiology, Juntendo University Hospital, Tokyo, Japan; Department of Radiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
• Magn Reson Imaging. 2019 Nov 1; 63: 235-243.

BackgroundPrevious methods for the quantification of brain tissue properties by magnetic resonance imaging were mainly based on two-dimensional acquisitions and were thus limited to a relatively low resolution in the slice direction compared to three-dimensional (3D) acquisitions. The 3D-quantification using an interleaved Look-Locker acquisition sequence with a T2 preparation pulse (3D-QALAS) sequence may allow for simultaneous acquisition of relaxometry parameters in high spatial resolution.PurposeTo evaluate bias, linearity, and day-to-day repeatability of relaxometry parameters, as well as tissue fraction maps, acquired with 3D-QALAS.Materials And MethodsScan-rescan test of the 3D-QALAS sequence was performed on a 1.5-T scanner with the International Society for Magnetic Resonance in Medicine/National institute of Standards and Technology system phantom and 10 healthy volunteers (7 male, 3 female; mean age, 23.2 ± 3.6 years). Simple linear regression analysis, Bland-Altman plots, and intrasubject coefficients of variation (CV) were used to assess the reliability of 3D-QALAS sequence-derived parameters. The T1, T2, proton density (PD), and myelin volume fraction (MVF) of in vivo brain regions were compared with values obtained using the multidynamic multi-echo sequence.ResultsIn the phantom study, the T1, T2, and PD values measured by 3D-QALAS showed strong linearity with the reference values (R2 = 0.998, 0.998, and 0.960 for T1, T2, and PD, respectively) and high repeatability (mean CV of 1.2%, 2.8%, and 2.9% for T1, T2, and PD, respectively). The T1, T2, PD, and MVF values of in vivo brain regions obtained with 3D-QALAS were highly consistent within subjects, with mean intrasubject CVs of 0.5%, 0.5%, 0.4%, and 1.6% for the T1, T2, PD, and MVF values, respectively.Conclusion3D-QALAS enables reliable measurement of T1, T2, PD, and MVF values of the whole brain in high spatial resolution across a clinically-relevant dynamic range.Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.

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