Acceleration of the Kinetics of Diffusion of Gadolinium in the Perilymphatic Structures of the Inner Ear.

The gadolinium contrast agents are now required to cross the blood-perilymph inner ear barrier after an intravenous administration in order to assess the endolymphatic structures in patients with vertigo or hearing loss, using MRI with delayed acquisition (at least 4 hours between injection and images acquisition).

This technique relies on the glymphatic diffusion of the gadolinium agents (Naganawa et al.,MRM Sci 2017) and has proved to be useful in patients with Meniere's Disease (Naganawa et al., AJNR 2014, Attyé et al., Eur Radiol 2018), Recurrent Peripheral Vestibulopathy (Attye et al., Eur Radiol 2015) or Otosclerosis (Mukaida et al., Otol Neurotol 2015), leading to numerous scientific publications over the last decade. The inner ear perilymph enhancement is particularly important to distinguish the saccule from the utricle, these inner ear structures were recently used to classify with imaging Meniere's Disease patient (Attye et al; European Radiology 2016).

We recently demonstrated in patients (Eliezer et al., J Neuroradiol 2018), comparing the effect of two macrocyclic contrast agents (Gd-DOTA, Dotarem® and Gd-DO3A-butrol, Gadovist®), that the Gd-DO3A-butrol better enhanced inner ear structures that Gd-DOTA, both with qualitative and quantitative analysis, allowing to more accurately diagnose endolymphatic hydrops in Meniere's Disease patients.

We have speculated that the differences in the physiochemical properties of Gd-contrast agents (concentration, relaxivity, osmalality) are determining factors to cross the blood-perilymph barrier.

These properties should allow scanning diseased patients earlier after contrast media administration, the delay between the injection and MRI acquisition being actually a limitation to expand this technique in the clinical setting, particularly with 1.5T magnets, due to the low Signal to Noise Ratio using 3D-FLAIR sequences analysis.