Scan-rescan Reproducibility of Myelin Sensitive MRI Techniques
Condition: Myelin Integrity
MeSH terms: Hypersensitivity
Study type: Observational

Summary: 
      This study is to assess the variation in the measurements of myelin sensitive MRI techniques
      in both white and grey matter in the brain.
    

Detailed description: 
      Magnetization Transfer Imaging (MTI) permits the assessment of the integrity of
      macromolecules in brain tissue, such as myelin and cellular/axonal membrane components.

      Multi-echo Susceptibility-Based imaging (SBI) provides quantitative susceptibility maps and
      T2* maps that - when combined - permit the disentanglement of myelin from iron and various
      phases of myelin degradation.

      Myelin Water Imaging (MWI) quantifies the water trapped between myelin layers by separating
      the multiple water components in T2 relaxometry data. In fact, the presence of myelin on
      water pools bound to it provokes a loss in magnetic resonance (MR)-signal coherence, which is
      more rapid than the one characterizing the water pools located within the axons or in the
      cytoplasm.

      A method based on a spiral acquisition that achieves a myelin-specific signal in clinically
      compatible scan times is currently applied: T1 relaxometry (quantitative T1, qT1) - which
      measures the time that a perturbed nuclear spin distribution needs to get back to equilibrium
      in the longitudinal plane- is sensitive to a number of components of the brain tissue such as
      myelin, axonal diameter and the overall architectural organization of the brain tissue.

      Finally, multi-shell diffusion allows the application of mathematical models of diffusion
      compartments, which in part are influenced by myelin integrity.

      The goal of this study is to assess the stability of these techniques in scan-rescan
      experiment on 20 healthy subjects.
    

Intervention name(s): myelin sensitive MRI scan
Intervention type(s): Diagnostic Test
Intervention description(s): Acquisition of 3 myelin sensitive MRI scans as follows: 1. Two MRI during 1 day; the second after 30 min interval and a repositioning.
2. One MRI within one week after the first one.
The total scan time will be ~ 1 hour. T1 maps will be calculated after magnetization-prepared 2 rapid acquisition gradient echoes (MP2RAGE6) acquisition based on a product sequence. Magnetization Transfer (MT) sat maps will be calculated. Quantitative susceptibility mapping (QSM) maps will be reconstructed using an in-house implementation of the structural feature based collaborative reconstruction algorithm (SFCR). For the reconstruction of multi-shell diffusion data, AMICO10 Accelerated Microstructure Imaging via Convex Optimization (AMICO) from diffusion MRI data will be used. Myelin Water Fraction maps will be fitted voxel-wise using a Non-Negative Least Squares fitting.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        healthy subjects recruited by public announcements (i.e. advertisement/flyer) on the
        University Hospital's and the University's notice board
      
Keywords: Magnetization Transfer Imaging (MTI); Multi-echo Susceptibility-Based imaging (SBI); Myelin Water Imaging (MWI); T1 relaxometry (quantitative T1, qT1); multi-shell diffusion; myelin sensitive MRI techniques