High resolution Magnetization Transfer Ratio (MTR) mapping in Multiple Sclerosis

Introduction: Multiple Sclerosis (MS) is a condition that affects young adults typically aged 20-40 years, and involves inflammation and demyelination of neural axons in the brain and nervous system. Magnetization transfer (MT) imaging studies the interaction between water and macromolecular (e.g.Protein in Myelin) protons and can be a useful in studying the changes in normal appearing white matter (NAWM) and grey matter (GM). It has the ability to detect the activity of disease and monitor its progression [1]. The destruction of myelin of neural fibers in MS disease results in a reduction in magnetization transfer process between water and myelin which correlates well with physical disability in MS patients [2]. MT imaging at 7T benefits from high spatial resolution due to increased signal to noise ratio. Limitations due to high Specific Absorption Rate (SAR) can be resolved using an MT prepared turbo field echo sequence (MT-TFE) with pulsed saturation pulse. Previous work [3] has shown that the MTR distribution of normal appearing white matter (NAWM) in the brains of MS patients is different from that of healthy control subjects and varies with distance from lesion site. Here, we measure the distribution of MTR values at 7T, comparing WM in healthy controls with normal appearing WM in MS patients. Methods: Eight MS patients with Clinically Isolated Syndrome (CIS) (early MS) were recruited from Nottingham University Hospital. Six age and sex matched healthy volunteers were also recruited, and both groups were consented according to local ethics approval. Scanning was performed on a 7T Philips Achieva system. The scan protocol at 7T included 3D MPRAGE, 2D multi-slice FLAIR, T2*-w. T1 maps were derived using data acquired using a range of MPRAGE images (200x170x73 mm 3