title: Molecular, dynamic, and structural origin of inhomogeneous magnetization transfer in lipid membranes.
abstract: To elucidate the dynamic, structural, and molecular properties that create inhomogeneous magnetization transfer (ihMT) contrast.
  
  
  
  Amphiphilic lipids, lamellar phospholipids with cholesterol, and bovine spinal cord (BSC) specimens were examined along with nonlipid systems. Magnetization transfer (MT), enhanced MT (eMT, obtained with double-sided radiofrequency saturation), ihMT (MT - eMT), and dipolar relaxation, T1D, were measured at 2.0 and 11.7 T.
  
  
  
  The amplitude of ihMT ratio (ihMTR) is positively correlated with T1Dvalues. Both ihMTR and T1Dincrease with increasing temperature in BSC white matter and in phospholipids and decrease with temperature in other lipids. Changes in ihMTR with temperature arise primarily from alterations in MT rather than eMT. Spectral width of MT, eMT, and ihMT increases with increasing carbon chain length.
  
  
  
  Concerted motions of phospholipids in white matter decrease proton spin diffusion leading to increased proton T1Dtimes and increased ihMT amplitudes, consistent with decoupling of Zeeman and dipolar spin reservoirs. Molecular specificity and dynamic sensitivity of ihMT contrast make it a suitable candidate for probing myelin membrane disorders. Magn Reson Med 77:1318-1328, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Swanson
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Dariya I
authors.initials: DI
authors.lastname: Malyarenko
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Mario L
authors.initials: ML
authors.lastname: Fabiilli
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Welsh
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Jon-Fredrik
authors.initials: JF
authors.lastname: Nielsen
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Ashok
authors.initials: A
authors.lastname: Srinivasan
mesh_terms: D000818:Animals; D002417:Cattle; D004058:Diffusion; D008051:Lipid Bilayers / Q000737:chemistry*; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008422:Materials Testing; D010743:Phospholipids / Q000737:chemistry*; D011522:Protons; D013696:Temperature; D066127:White Matter / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D010743:Phospholipids; D011522:Protons
keywords: lipid dynamics; magnetization transfer; myelin membrane; white matter