Quasi-steady-state (QUASS) CEST for robust quantification of tumor MT and APT effects by correction of saturation time and relaxation delay

To reduce CEST measurement’s dependence on long RF saturation duration (Ts) and relaxation delay (Td), we developed a post-processing strategy to derive the quasi-steady-state (QUASS) CEST from apparent measurements. The simulation and in-vivo experiment results show that the apparent MT and APT effects and their contrast substantially depend on Ts and Td. In comparison, the QUASS MT and APT effects and their difference between contralateral normal tissue and tumor exhibit little dependence on Ts and Td. To conclude, the QUASS CEST algorithm enables robust CEST quantification and offers a straightforward approach to standardize CEST measurements.