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Purpose: New multiple sclerosis (MS) disease-modifying therapies (DMTs), which exert beneficial effects through prevention of relapse, limitation of disability progression, and improvement of patients' quality of life, have recently emerged. Nonetheless, these DMTs are not without associated complications (severe adverse events like. progressive multifocal leukoencephalopathy). Patient follow-up requires regular clinical evaluations and close monitoring with magnetic resonance imaging (MRI). Detection of new T2 lesions and potential brain atrophy measurements contribute to the evaluation of treatment effectiveness. Current MRI protocols for MS recommend the acquisition of an annual gadolinium (Gd) enhanced MRI, resulting in administration of high volume of contrast agents over time and Gd accumulation in the brain., Methods: A consensus report was established by neuroradiologists and neurologists from the French Observatory of MS, which aimed at reducing the number of Gd injections required during MS patient follow-up., Recommendations: The French Observatory of MS recommends the use of macrocyclic Gd enhancement at time of diagnosis, when a new DMT is introduced, at 6-month re-baseline, and when previous scans are unavailable for comparison. Gd administration can be performed as an option in case of relapse or suspicion of intercurrent disease such as progressive multifocal leukoencephalopathy. Other follow-up MRIs do not require contrast enhancement, provided current and previous MRI acquisitions follow the same standardized protocol including 3D FLAIR sequences., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Ever since gadolinium was found to deposit in the brain of patients with normal kidney function by Kanda et al. in 2014, several studies have been conducted to evaluate its effect on the patients' health. However, conflicting results were obtained regarding imaging in gadolinium retention. These finding were attributed to the chelating structure of the administered gadolinium-based contrast agent (GBCA): linear agents were found to accumulate in the dentate nucleus (DN) and the globus pallidus (GP) of subjects even after one dose. There are some contradictory results when assessing macrocyclic agents. In the following article, we review the basis of GBCAs characteristics and their side effects, as well as, the MRI studies that assessed the accumulation of gadolinium in the brain. Based on the results of several studies, in 2017, the European Medicine Agency requested the suspension of the marketing authorizations for three linear GBCAs: gadodiamide (Omniscan®), gadoversetamide (Optimark®) and gadopentate dimeglimine (Magnevist®) and limited the use of gadoxetate disodium (Primovist/Eovist®) and gadobenate dimeglumine (MultiHance®) to hepatic uptake for imaging poorly vascularized hepatic lesions. Accordingly, the FDA did not restrict GBCA use, but will continue to study their safety and urged clinicians to use these agents sparingly. All macrocyclic GBCAs continued however to be used as no available valid evidence linked them to brain gadolinium retention. Regardless of possible accumulation in the brain, there is no evidence to-date that gadolinium retention leads to any disease or disorders in subjects with normal renal function. Further investigations with long-term follow-up are needed.

Purpose: Gadolinium-based contrast agent (GBCA) effect on automated segmentation algorithms of subcortical gray matter (GM) is not fully known. The aim of this study is to determine gadolinium effect on the segmentation of the thalamus and whole brain tissue using different automated segmentation techniques., Methods: Eighty-four multiple sclerosis (MS) patients underwent an MRI acquisition of two 3DT1-weighted sequences with and without gadolinium injection among which 10 were excluded after image quality check. Manual thalamic segmentation considered as gold standard was performed on unenhanced T1 images. volBrain and FSL-Anat were used to automatically segment the thalamus on both enhanced and unenhanced T1 and the degree of similitude (DICE) values were compared between manual and automatic segmentations. Whole brain tissue segmentation (GM, white matter (WM), and lateral ventricles (LV)) was also performed using SIENAX. A paired samples t test was applied to test the significance of DICE value differences between the thalamic manual and automatic segmentations of both enhanced and unenhanced T1 images., Results: Significant differences (FSL-Anat 1.474% p < 0.001 and volBrain 1.990% p < 0.001) in DICE between thalamic manual and automatic segmentations on both enhanced and unenhanced images were observed. Automatic tissue segmentation showed a mean DICE of 81.5%, with LV having the lowest DICE value (74.2%). When compared to tissue segmentations, automatic thalamic segmentations by FSL-Anat or volBrain demonstrated a higher degree of similitude (FSL-Anat = 91.7% and volBrain = 90.7%)., Conclusion: Gadolinium has a significant effect on subcortical GM segmentation. Although significant, the observed subtle changes could be considered acceptable when used for region-based analysis in perfusion or diffusion imaging.