Magnetization transfer using inversion recovery during off-resonance irradiation |
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Authors: | Mangia Silvia De Martino Federico Liimatainen Timo Garwood Michael Michaeli Shalom |
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Affiliation: | a Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota School of Medicine, Minneapolis, MN 55455, USAb Department of Cognitive Neuroscience, University of Maastricht, Maastricht 6200, Netherlandsc Department of Biotechnology and Molecular Medicine, University of Eastern Finland, Kuopio 70211, Finland |
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Abstract: | Estimation of magnetization transfer (MT) parameters in vivo can be compromised by an inability to drive the magnetization to a steady state using allowable levels of radiofrequency (RF) irradiation, due to safety concerns (tissue heating and specific absorption rate (SAR)). Rather than increasing the RF duration or amplitude, here we propose to circumvent the SAR limitation by sampling the formation of the steady state in separate measurements made with the magnetization initially along the -z and +z axis of the laboratory frame, i.e. with or without an on-resonance inversion pulse prior to the off-resonance irradiation. Results from human brain imaging demonstrate that this choice provides a tremendous benefit in the fitting procedure used to estimate MT parameters. The resulting parametric maps are characterized by notably increased tissue specificity as compared to those obtained with the standard MT acquisition in which magnetization is initially along the +z axis only. |
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Keywords: | Exchange Solid pool Brain imaging Parametric mapping |
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