Elsevier

Magnetic Resonance Imaging

Volume 63, November 2019, Pages 235-243
Magnetic Resonance Imaging

Original contribution
Three-dimensional high-resolution simultaneous quantitative mapping of the whole brain with 3D-QALAS: An accuracy and repeatability study

https://doi.org/10.1016/j.mri.2019.08.031Get rights and content
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Abstract

Background

Previous 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.

Purpose

To evaluate bias, linearity, and day-to-day repeatability of relaxometry parameters, as well as tissue fraction maps, acquired with 3D-QALAS.

Materials and methods

Scan–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.

Results

In 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.

Conclusion

3D-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.

Abbreviations

BPV
Brain parenchymal volume
CSF
Cerebrospinal fluid
CV
Coefficient of variation
GM
Gray matter
ICC
Intraclass correlation coefficient
LOA
Limits of agreement
MDME
Multidynamic multi-echo
MRI
Magnetic resonance imaging
MVF
Myelin volume fraction
NoN
Other intracranial material
PD
Proton density
SD
Standard deviation
VOI
Volume of interest
WM
White matter

Keywords

Myelin
Proton density
Quantitative magnetic resonance imaging
Relaxation time
Relaxometry
Synthetic magnetic resonance imaging

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