Imaging of Amide Proton Transfer (APT) and Nuclear Overhauser Effect (NOE) Using Chemical Exchange Rotation Transfer (CERT)

Zhongliang Zu¹, Junzhong Xu¹, Hua Li¹, Christopher C. Quarles¹, Mark D. Does¹, John C. Gore¹, Daniel F. Gochberg¹

CEST Z-spectra show dips from exchangeable sites (-NH2, -NH, and OH) at down field frequencies and from Nuclear Overhauser Enhancement (NOE) at up field frequencies. Quantitative mapping of such effects is difficult as conventional asymmetric analyses include contributions from both exchangeable sites and NOE. Here, we use a modified CEST method, chemical exchange ration transfer (CERT), to quantify amide proton transfer (APT) and NOE through subtraction of CEST signals at two irradiation flip angles instead of two frequency offsets. In vivo experiments on a rat brain with 9L tumor show interesting contrasts from APT and NOE.