Jie Luo1, Xiang He2, D. Andre' d'Avignon1, Joseph J. H. Ackerman1, Dmitriy A. Yablonskiy2
1Department of Chemistry, Washington University, Saint Louis, MO, USA; 2Department of Radiology, Washington University, Saint Louis, MO, USA
High field, conventional GRE-MR phase images show superior contrast between gray and white matter in human brain. Possible origins of this contrast, such as magnetic susceptibility due to tissue lipids, non-heme iron, deoxyhemoglobin, and water-protein 1H exchange have been suggested, yet the genesis remains to be elucidated. Herein, separation of susceptibility and 1H exchange effects in protein solutions is described. The frequency shift due to protein susceptibility is about three times greater (and with opposite sign) compared to that due to 1H exchange. Further, significant protein content is cross-linked in vivo, possibly reducing frequency shift contributions from water-protein 1H exchange.