MRI assessment of iron deposition in multiple sclerosis.

Iron deposition in the human brain tissue occurs in the process of normal aging and in many neurodegenerative diseases. Elevated iron levels in certain brain regions are also an increasingly recognized finding in multiple sclerosis (MS). The exact mechanism(s) for this phenomenon and its implication in terms of pathophysiology and clinical significance are still largely unknown and debated. Reliable methods to exactly quantify brain iron are a first step to clarify these issues. Therefore, the aim of this review is to present currently available magnetic resonance imaging (MRI) techniques for the assessment of brain iron. These include relaxation time mapping, phase imaging, susceptibility-weighted imaging, susceptibility mapping, magnetic field correlation imaging, and direct saturation imaging. After discussing their advantages and disadvantages, existing MRI clinical correlations with brain iron concentration in MS are summarized and future research directions are shown.