Abstract #0498

Orientation dependence of inhomogeneous magnetization transfer and dipolar order relaxation time in a phospholipid bilayer sample

Sarah Rosemary Morris^1,2,3, Rebecca Frederick¹, Alex L MacKay^1,2,4, Cornelia Laule^1,2,3,5, and Carl A. Michal¹

¹Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada, ²Radiology, University of British Columbia, Vancouver, BC, Canada, ³International Collaboration on Repair Discoveries, Vancouver, BC, Canada, ⁴UBC MRI Research Centre, Vancouver, BC, Canada, ⁵Pathology & Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada

Inhomogeneous magnetization transfer ratio (ihMTR) is reported to have significant orientation dependence in the brain, likely due to the anisotropy of dipolar couplings between methylene protons on the oriented lipids in myelin bilayers. We measured the orientation dependence of linewidth, dipolar relaxation time (T_1D) and ihMTR in an aligned phospholipid bilayer sample at 9.4T. ihMTR was maximized when the bilayers were parallel to B₀and minimized near the magic angle (~54.7°) despite the fact that T_1D is maximized there. This is in contrast to previous in vivo results which show maximal ihMTR for bilayers perpendicular to B₀.

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