Automated brain tissue and myelin volumetry based on quantitative MR imaging with various in-plane resolutions

Background and purpose. - Segmented brain tissue and myelin volumes can now be automatically calculated using dedicated software (SyMRI), which is based on quantification of R-1 and R-2 relaxation rates and proton density. The aim of this study was to determine the validity of SyMRI brain tissue and myelin volumetry using various in-plane resolutions. Methods. - We scanned 10 healthy subjects on a 1.5T MR scanner with in-plane resolutions of 0.8, 2.0 and 3.0 mm. Two scans were performed for each resolution. The acquisition time was 7-min and 24-sec for 0.8 mm, 3-min and 9-sec for 2.0 mm and 1-min and 56-sec for 3.0 mm resolutions. The volumes of white matter (WM), gray matter (GM), cerebrospinal fluid (CSF), non-WM/GM/CSF (NoN), brain parenchymal volume (BPV), intracranial volume (ICV) and myelin were compared between in-plane resolutions. Repeatability for each resolution was then analyzed. Results. - No significant differences in volumes measured were found between the different in-plane resolutions, except for NoN between 0.8 mm and 2.0 mm and between 2.0 mm and 3.0 mm. The repeatability error value for the WM, GM, CSF, NoN, BPV and myelin volumes relative to ICV was 0.97%, 1.01%, 0.65%, 0.86%, 1.06% and 0.25% in 0.8 mm; 1.22%, 1.36%, 0.73%, 0.37%, 1.18% and 0.35% in 2.0 mm and 1.18%, 1.02%, 0.96%, 0.45%, 1.36%, and 0.28% in 3.0 mm resolutions. Conclusion. - SyMRI brain tissue and myelin volumetry with low in-plane resolution and short acquisition times is robust and has a good repeatability so could be useful for follow-up studies. (C) 2017 Elsevier Masson SAS. All rights reserved.