title: Simultaneous measurement of total water content and myelin water fraction in brain at 3T using a T2relaxation based method.
abstract: This work demonstrates the in vivo application of a T2relaxation based total water content (TWC) measurement technique at 3T in healthy human brain, and evaluates accuracy using simulations that model brain tissue. The benefit of using T2relaxation is that it provides simultaneous measurements of myelin water fraction, which correlates to myelin content.
  
  
  
  T2relaxation data was collected from 10 healthy human subjects with a gradient and spin echo (GRASE) sequence, along with inversion recovery for T1mapping. Voxel-wise T2distributions were calculated by fitting the T2relaxation data with a non-negative least squares algorithm incorporating B1+inhomogeneity corrections. TWC was the sum of the signals in the T2distribution, corrected for T1relaxation and receiver coil inhomogeneity, relative to either an external water standard or cerebrospinal fluid (CSF). Simulations were performed to determine theoretical errors in TWC.
  
  
  
  TWC values measured in healthy human brain relative to both external and CSF standards agreed with literature values. Simulations demonstrated that TWC could be measured to within 3-4% accuracy.
  
  
  
  In vivo TWC measurement using T2relaxation at 3T works well and provides a valuable tool for studying neurological diseases with both myelin and water changes.
authors.affiliation: Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada. Electronic address: smeyers@ualberta.ca.
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Meyers
authors.affiliation: Medicine, University of British Columbia, 2211 Wesbrook Mall, Vancouver, BC V6T 2B5, Canada. Electronic address: shannon.kolind@ubc.ca.
authors.forename: Shannon H
authors.initials: SH
authors.lastname: Kolind
authors.affiliation: Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada; Radiology, University of British Columbia, 2211 Wesbrook Mall, Vancouver, BC V6T 2B5, Canada. Electronic address: mackay@physics.ubc.ca.
authors.forename: Alex L
authors.initials: AL
authors.lastname: MacKay
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001834:Body Water / Q000000981:diagnostic imaging* / Q000378:metabolism*; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005260:Female; D006801:Humans; D016018:Least-Squares Analysis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009186:Myelin Sheath / Q000378:metabolism*; D012016:Reference Values; D015203:Reproducibility of Results; D055815:Young Adult
keywords: In vivo; Magnetic resonance; Myelin water fraction; Proton density; T(2) relaxation; Water content