Can T1 w/T2 w ratio be used as a myelin-specific measure in subcortical structures? Comparisons between FSE-based T1 w/T2 w ratios, GRASE-based T1 w/T2 w ratios and multi-echo GRASE-based myelin water fractions.
NMR Biomed
; 31(3)2018 03.
Article
em En
| MEDLINE
| ID: mdl-29315894
ABSTRACT
Given the growing popularity of T1 -weighted/T2 -weighted (T1 w/T2 w) ratio measurements, the objective of the current study was to evaluate the concordance between T1 w/T2 w ratios obtained using conventional fast spin echo (FSE) versus combined gradient and spin echo (GRASE) sequences for T2 w image acquisition, and to compare the resulting T1 w/T2 w ratios with histologically validated myelin water fraction (MWF) measurements in several subcortical brain structures. In order to compare these measurements across a relatively wide range of myelin concentrations, whole-brain T1 w magnetization prepared rapid acquisition gradient echo (MPRAGE), T2 w FSE and three-dimensional multi-echo GRASE data were acquired from 10 participants with multiple sclerosis at 3 T. Then, after high-dimensional, non-linear warping, region of interest (ROI) analyses were performed to compare T1 w/T2 w ratios and MWF estimates (across participants and brain regions) in 11 bilateral white matter (WM) and four bilateral subcortical grey matter (SGM) structures extracted from the JHU_MNI_SS 'Eve' atlas. Although the GRASE sequence systematically underestimated T1 w/T2 w values compared to the FSE sequence (revealed by Bland-Altman and mountain plots), linear regressions across participants and ROIs revealed consistently high correlations between the two methods (r2 = 0.62 for all ROIs, r2 = 0.62 for WM structures and r2 = 0.73 for SGM structures). However, correlations between either FSE-based or GRASE-based T1 w/T2 w ratios and MWFs were extremely low in WM structures (FSE-based, r2 = 0.000020; GRASE-based, r2 = 0.0014), low across all ROIs (FSE-based, r2 = 0.053; GRASE-based, r2 = 0.029) and moderate in SGM structures (FSE-based, r2 = 0.20; GRASE-based, r2 = 0.17). Overall, our findings indicated a high degree of correlation (but not equivalence) between FSE-based and GRASE-based T1 w/T2 w ratios, and low correlations between T1 w/T2 w ratios and MWFs. This suggests that the two T1 w/T2 w ratio approaches measure similar facets of subcortical tissue microstructure, whereas T1 w/T2 w ratios and MWFs appear to be sensitized to different microstructural properties. On this basis, we conclude that multi-echo GRASE sequences can be used in future studies to efficiently elucidate both general (T1 w/T2 w ratio) and myelin-specific (MWF) tissue characteristics.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Marcadores de Spin
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Imageamento por Ressonância Magnética
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Água
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Córtex Cerebral
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Bainha de Mielina
Tipo de estudo:
Prognostic_studies
Limite:
Adult
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Aged
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Aged80
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Female
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Humans
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Male
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Middle aged
Idioma:
En
Ano de publicação:
2018
Tipo de documento:
Article