Contamination of Neurometabolite Amine-Water Proton Exchange to Amide Proton Transfer MRI

Xiaopeng Zong¹, Ping Wang¹, Seong-Gi Kim¹, Tao Jin¹

Amide-water proton transfer (APT) can be exploited to provide useful MRI contrast under various disease conditions. However, the APT-weighted signals (APTw) might be contaminated by other chemical exchange processes, such as fast amine-water proton exchange. To investigate this issue, we measured APTw of nine major neurometabolites in phantoms and estimated their contributions to the <I>in vivo</I> APTw contrast in ischemic rat brain. We found significant contributions from several metabolites to the APTw, which showed pH dependence opposite to the APTw signal <I>in vivo</I>. Thus, possible contaminations from neurometabolites should be considered when interpreting the sources of APTw contrast.