Clinical Pulsed CEST MRF Optimization using the Cramer-Rao Bound and Sequential Quadratic Programming

Motivation: The lack of a protocol optimization technique suitable for practical pulsed acquisition impedes the clinical translation of CEST MRF. Goal(s): To develop a pulsed CEST MRF protocol optimization method, enabling improved parameter discrimination ability and accelerated acquisition. Approach: The Cramer-Rao bound for variance assessment was employed on Bloch-McConnell-based simulated signals, followed by a numerical sequential quadratic programming optimization of MRF saturation pulse powers. Validation was performed using L-arginine phantoms for preclinical (7T) and clinical (3T) scanners. Results: The proposed optimization approach resulted in significantly lower CEST-MRF reconstruction error (p<0.001) compared to baseline and a drastically short acquisition time (<20 s). Impact: A pulsed CEST MRF optimization technique was developed, bridging the gap imposed by the lack of accurate analytical solutions and CEST optimization methods for practical clinical settings. The technique increases the translation potential of quantitative and rapid CEST imaging.