Absolute B1-Mapping from Repeated Varying Flip Angle RF Excitations
Axel L, Pai V, Manglik T, Cernicanu A, Kim D
New York University
The inhomogeneity of the RF pulse flip angle needs to be considered in quantitative studies. We propose a method to gauge this variation by calculating the actual B1 seen by each pixel in the field of view. The method relies on the acquisition of 40 measurements at different nominal flip angles and takes into account B0 inhomogeneity effects on the effective flip angle. We imaged a cylindrical phantom and calculated the B1 map and the corresponding effective flip angle map. The B1 calculation method is robust, and it shows important B1 and corresponding flip angle variations (up to 10%).