Optimization of pulsed saturation transfer MR fingerprinting (ST MRF) acquisition using the Cram\'er-Rao bound and sequential quadratic programming

Abstract

Purpose: To develop a method for optimizing pulsed saturation transfer MR fingerprinting (ST MRF) acquisition. Methods: The Cram\'er-Rao bound (CRB) for variance assessment was employed on Bloch-McConnell-based simulated signals, followed by a numerical sequential quadratic programming optimization and basin-hopping avoidance of local minima. Validation was performed using L-arginine phantoms and healthy human volunteers (n=4) at 3T while restricting the scan time to be less than 40 s. Results: The proposed optimization approach resulted in a significantly improved agreement with reference gold standard values in vivo, compared to baseline non-optimized protocols (8$\%$ lower NRMSE, 7$\%$ higher SSIM, and 15$\%$ higher Pearson's r value, p<0.001). Conclusion: The combination of the CRB with sequential quadratic programming and a rapid Bloch-McConnell simulator offers a means for optimizing and accelerating pulsed CEST and semisolid magnetization transfer (MT) MRF acquisition.