Balanced steady-state free precession (bSSFP) cardiac MRI benefits greatly from reduced repetition time (TR). Minimum TR is often limited by specific absorption rate (SAR) and hardware constraints. RF shimming can be used with parallel transmission (PTx) to work within such constraints, but direct minimization of TR is not straightforward since the constraints themselves vary as TR is reduced.
We present an extended RF shimming framework in which PTx degrees of freedom are simultaneously optimised with pulse sequence properties. The result is minimum TR bSSFP sequences that operate at the SAR limits and within hardware constraints for 3T cardiac MRI.