A T1-independent evaluation method for steady state CEST signals

Motivation: Steady state CEST (ssCEST) is an approach to accelerate CEST experiments, which typically require long measurement times. The ssCEST-signal generally depends not only on the concentration and exchange rate of the exchanging protons but also on the T1 relaxation of the tissue. Goal(s): The aim of the work was to develop a T1-independent ssCEST method. Approach: Based on the analytical equation for spoiled gradient echo ssCEST-signals, a new T1-independent evaluation metric based on a double-angle approach was derived and tested using simulations and phantom measurements. Results: The T1-independence of the derived evaluation metric and its applicability to potatoes as plant phantoms was demonstrated. Impact: The T1-dependence of spoiled gradient echo ssCEST-signals can be eliminated and corrected by using the proposed analytical evaluation metric based on a double-angle approach.