Optimization of Spin-Lock Parameters for Chemical Exchange Imaging Contrast Enhancement by Maximizing Asymmetric Magnetization Transfer Ratio: A Theoretical Study

Jing Yuan¹, Qinwei Zhang¹, Anil T. Ahuja¹, Yi-Xiang Wang¹

Spin-lock technique, which is traditionally used to measure T1l relaxation time, can also be used for chemical exchange (CE) imaging. This study theoretically investigates the optimization of spin-lock frequency (FSL) and spin-lock time (TSL) to maximize the asymmetric magnetization transfer ratio for different proton exchange rates, by numerical simulations based on a two-pool R1l relaxation model derived from the Bloch-McConnell equations. Results show that spin-lock pulse with low FSL and long TSL is sensitive to detect slow CE processes while spin-lock pulse with high FSL and short TSL is useful for fast CE process study.