Assessment of Radiotherapeutic Effect on Brain Tumors by Dynamic Susceptibility Contrast MR Imaging:A Preliminary Report

Anion-exchange compositions are provided comprising anion-exchange functional groups comprising at least a first and a second nitrogen group, wherein the first nitrogen group is a quaternary amine and the second nitrogen group is selected from the group consisting of primary, secondary, tertiary or quaternary amines. Methods of making and using the compositions are also provided.