Chemical Exchange Contrast with Off-Resonance Spin Locking

Feliks Kogan¹, Anup Singh¹, Kejia Cai¹, Mohammad Haris¹, Hari Hariharan¹, Ravinder Reddy¹

Chemical Exchange Saturation Transfer (CEST) has become a popular method for measurement of metabolites with exchangeable protons. Current CEST methods are plagued by direct saturation of water protons which leads to decreased SNR and CEST contrast. In this work, we demonstrate the feasibility of using an off-resonance spin-lock (SL) pulse for generating the exchange mediated contrast. We showed in phantom experiments that this new method can decrease direct water saturation and increase chemical exchange contrast. We also demonstrated the feasibility of using the SL method in vivo in human patellar cartilage and showed that the SL method was 15% more sensitive than conventional CEST.