Flavio Carinci1,2, Federico von Samson-Himmelstjerna1,3, Davide Santoro1, Tomasz Lindel1,4, Matthias Dieringer1,5, Frank Seifert1,4, Jan Sobesky3,6, Thoralf Niendorf1,5
1Berlin Ultra-High Field Facility (BUFF), Max Delbrck Center for Molecular Medicine (MDC), Berlin, Germany; 2Department of Physics, Insubria University, Como, Italy; 3Center for Stroke Research Berlin (CSB), Charit Universitaetsmedizin Berlin, Berlin, Germany; 4Physikalisch-Technische Bundesanstalt (PTB); 5Experimental & Clinical Research Center (ECRC)), Charit Campus Berlin, Berlin, Germany; 6Department of Neurology, Charit Universitaetsmedizin Berlin, Berlin, Germany
In ultra-high field MRI the increase of signal to noise ratio comes together with longer T1 and shorter T2* relaxation times, higher specific absorption rates and higher B1 field inhomogeneities. Phase-based methods for B1 mapping have been shown to be more accurate than magnitude-based methods as the phase of the signal is insensitive to T1 relaxation effects and coil sensitivity profiles. In this work we compare four phase-based methods taken from literature and adapted to 7T MRI: the Mugler method, the Morrell method, the Santoro method and the Sacolick method. The methods are compared in terms of the sensitivity to the B1 and B0 inhomogeneities, SAR levels and repetition times, using simulations together with phantom and in vivo experiments.