title: Time-efficient, high-resolution, whole brain three-dimensional macromolecular proton fraction mapping.
abstract: OBJECTIVE
  Macromolecular proton fraction (MPF) mapping is a quantitative MRI method that reconstructs parametric maps of a relative amount of macromolecular protons causing the magnetization transfer (MT) effect and provides a biomarker of myelination in neural tissues. This study aimed to develop a high-resolution whole brain MPF mapping technique using a minimal number of source images for scan time reduction.
  
  
  METHODS
  The described technique was based on replacement of an actually acquired reference image without MT saturation by a synthetic one reconstructed from R1 and proton density maps, thus requiring only three source images. This approach enabled whole brain three-dimensional MPF mapping with isotropic 1.25 × 1.25 × 1.25 mm(3) voxel size and a scan time of 20 min. The synthetic reference method was validated against standard MPF mapping with acquired reference images based on data from eight healthy subjects.
  
  
  RESULTS
  Mean MPF values in segmented white and gray matter appeared in close agreement with no significant bias and small within-subject coefficients of variation (<2%). High-resolution MPF maps demonstrated sharp white-gray matter contrast and clear visualization of anatomical details, including gray matter structures with high iron content.
  
  
  CONCLUSIONS
  The proposed synthetic reference method improves resolution of MPF mapping and combines accurate MPF measurements with unique neuroanatomical contrast features.
authors.affiliation: Department of Radiology, University of Washington, Seattle, Washington, USA.|Research Institute of Biology and Biophysics, Tomsk State University, Tomsk, Russian Federation.
authors.forename: Vasily L
authors.initials: VL
authors.lastname: Yarnykh
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D015415:Biomarkers / Q000737:chemistry; D001921:Brain / Q000000981:diagnostic imaging; D001931:Brain Mapping / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional; D046911:Macromolecular Substances / Q000737:chemistry*; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D009186:Myelin Sheath / Q000737:chemistry; D009474:Neurons / Q000378:metabolism; D011522:Protons
chemical_list: D015415:Biomarkers; D046911:Macromolecular Substances; D011522:Protons
keywords: gray matter; macromolecular proton fraction; magnetic resonance imaging; magnetization transfer; myelin; white matter