Molecular Size Dependency of Water Macromolecule Exchange Induced Frequency Shift

Kai Zhong¹, Karl-Heinz Smalla², Alexander Brensing¹, Oliver Speck¹

Previous study suggested that water macromolecule exchange (WME) processes could contribute significantly to the in vivo GM/WM contrast. In this study, we studied systematically the WME shift abilities of several proteins with different molecular weight (Mw) under neutral pH. It is found that the WME shift ability of macromolecules depends strongly on their size and can be quantitatively determined. A strong relationship between the macromolecule distribution and the corresponding in vivo frequency shift for phase imaging is thus predicted. This finding paves the way for phase imaging applications in pathologies with altered in vivo macromolecule content.