B0-Independent Quantitative Measurement of Low B1 Field for Human Cardiac MRI at 7T

Yuehui Tao¹, Aaron T. Hess¹, Graeme A. Keith¹, Christopher T. Rodgers¹, Matthew D. Robson¹

Cardiac MRI at 7T has several potential advantages over 1.5T and 3T, such as higher signal-to-noise ratio and higher resolution. A quantitative B1 map is routinely required at 7T to allow the management of large B1 variations across the heart. Conventional methods based on rectangular saturation pulse are not accurate in this case because of large B0 inhomogeneity and low flip angle from low maximum B1 power. We propose to use a non-selective broad-band full-passage HS8 pulse that is operating outside its adiabatic state to obtain B1 maps in situations where the B1 is low and the B0 is inhomogeneous such as for cardiac applications at 7T.