Higher b-values improve the correlation between diffusion MRI and the cortical microarchitecture.

Sandy Mournet, G. Okubo, I. Koubiyr, B. Zhang, H. Kusahara, V. H. Prevost, N. Ichinose, B. Triaire, B. Hiba, V. Dousset, T. Tourdias
Neuroradiology. 2020-06-01; :
DOI: 10.1007/s00234-020-02462-4

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Mournet S(1)(2), Okubo G(3)(4), Koubiyr I(3), Zhang B(5), Kusahara H(6), Prevost VH(6), Ichinose N(6), Triaire B(6), Hiba B(7), Dousset V(3)(8), Tourdias T(3)(8).

Author information:
(1)Neurocentre Magendie, INSERM U1215, Université de Bordeaux, Bordeaux, France.
(2)Neuroimagerie diagnostique et thérapeutique, CHU de Bordeaux, Bordeaux, France.
(3)Neurocentre Magendie, INSERM U1215, Université de Bordeaux, Bordeaux, France.
(4)Department of Radiology, Tenri Hospital, Nara, Japan.
(5)Canon Medical systems Europe, Zoetermeer, Netherlands.
(6)Canon Medical Systems Corporation, Otawara, Japan.
(7)Centre de neuroscience cognitive, CNRS UMR 5229, Université Claude Bernard Lyon I, Lyon, France.
(8)Neuroimagerie diagnostique et thérapeutique, CHU de Bordeaux, Bordeaux, France.

PURPOSE: In diffusion MRI (dMRI), it remains unclear to know how much increase of
b-value is conveying additional biological meaning. We tested the correlations
between cortical microarchitecture and diffusion metrics computed from standard
(1000 s/mm2), high (3000 s/mm2), to very high (5000 s/mm2) b-value dMRI.

METHODS: Healthy volunteers were scanned with a dMRI pulse sequence that was
first optimized together with a T1-WI and T2-WI. Averaged cortical surface map of
estimated myelin (T1-WI/T2-WI) was compared with surface maps of mean diffusivity
(MD) computed from each b-value (MD1000, MD3000, and MD5000) and to surface map
of mean kurtosis (MK computed from the 0-, 1000-, to 3000-s/mm2 shells) in 360
cortical parcels using Spearman correlations, multiple linear regressions, and
Akaike information criteria (AIC).

RESULTS: Surface map from MD1000 showed variations not related to myelin but the
MD3000 and MD5000 maps inversely mirrored estimated myelin map; lower MD values
being observed in more myelinated cortical areas. MK mirrored myelinated cortical
areas. Quantitatively, Spearman correlations between myelin and MD became more
and more negative as long as b-values increased while the correlation was
positive between myelin and MK. Multiple regression models confirmed negative
associations between myelin and MD that were significantly better from MD1000 to
MD3000 and MD5000 (R2 = 0.33, p

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