Abstract #0305

IHMT: Is it misnamed? A simple theoretical description of "inhomogeneous" MT.

Alan P Manning¹, Kimberley L Chang², Alex MacKay^1,3, and Carl A Michal¹

¹Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada, ²Department of Neurology, University of British Columbia, Vancouver, BC, Canada, ³UBC MRI Research Centre, Department of Radiology, University of British Columbia, Vancouver, BC, Canada

Inhomogeneous MT (IHMT) shows promise for myelin-selectivity. Images acquired with soft prepulses at positive and negative offsets simultaneously show a reduced intensity compared to images with a single positive or negative offset prepulse. The leading hypothesis is that this works due to inhomogeneous broadening of the lipid proton line. Our results contradict this. We show that IHMT can be explained by a simple spin-1 model of a coupled methylene pair, and that it occurs in homogeneously-broadened systems (hair and wood). We propose the relevant timescales for IHMT are the dipolar coupling correlation time and the prepulse nutation period.

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