Higher b -values improve the correlation between diffusion MRI and the cortical microarchitecture
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DIAGNOSTIC NEURORADIOLOGY
Higher b-values improve the correlation between diffusion MRI and the cortical microarchitecture Sandy Mournet 1,2 & G. Okubo 1,3 & I. Koubiyr 1 & B. Zhang 4 & H. Kusahara 5 & V. H. Prevost 5 & N. Ichinose 5 & B. Triaire 5 & B. Hiba 6 & V. Dousset 1,2 & T. Tourdias 1,2 Received: 28 March 2020 / Accepted: 18 May 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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 T2WI. 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 < 0.001; R2 = 0.43, p < 0.001; and R2 = 0.50, p < 0.001) and positive association between myelin and MK (R2 = 0.53, p < 0.001). Comparisons of the 3 statistical models showed the best performances with MK and MD5000 (AICMK < AICMD5000 < AICMD3000 < AICMD1000). Conclusion Higher b-values are more closely related to subtle cellular variations of the cortical microarchitecture. Keywords Diffusion tensor imaging . High-order diffusion MR methods . Cortex myeloarchitecture . Normal brain . Human study Sandy Mournet and G. Okubo contributed equally to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00234-020-02462-4) contains supplementary material, which is available to authorized users. * Sandy Mournet [email protected] 1
Neurocentre Magendie, INSERM U1215, Université de Bordeaux, Bordeaux, France
2
Neuroimagerie diagnostique et thérapeutique, CHU de Bordeaux, Bordeaux, France
3
Department of Radiology, Tenri Hospital, Nara, Japan
4
Canon Medical systems Europe, Zoetermeer, Netherlands
5
Canon Medical Systems Corporation, Otawara, Japan
6
Centre de neuroscience cognitive, CNRS UMR 5229, Université Claude Bernard Lyon I, Lyon, France
Abbreviations AIC A
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