Mri contrast enhancement of magnetization prepared steady state sequence: an optimal control framework

The present work investigates the possibilities of enhancing MRI contrast between two target tissues in a three-dimensional Magnetization-Prepared Rapid Gradient-Echo (MP-RAGE) based on relaxation time's differences. The benefit lies in the adaptation of the GRAPE algorithm to the optimization of a magnetization preparation in a cyclic sequence without full recovery between each cycle. This numerical approach allows optimizing a magnetization preparation of an arbitrary number of radio frequency pulses to enhance contrast, taking in account the establishment of a steady state in the longitudinal component of the magnetization. In vivo validation on rat brain is performed at 11.7T and shows the benefit of an optimized T(2)Prep-IR compared to a simple inversion to enhance contrast between white and gray matter.