Cem Murat Deniz1,2,
Leeor Alon2,3, Ryan Brown3, Hans-Peter Fautz4,
Daniel K. Sodickson3, Yudong Zhu3
1Center for
Biomedical Imaging , Department of Radiology, NYU School of Medicine, New York,
NY, USA; 2Sackler Institute of Graduate Biomedical Sciences, NYU
School of Medicine, New York, NY, USA; 3Center for Biomedical
Imaging, Department of Radiology, NYU School of Medicine, New York, NY, USA; 4Siemens
Medical Solutions, Erlangen, Germany
Specific absorption rate (SAR) management and excitation homogeneity are critical aspects of parallel radio frequency (RF) transmission pulse design at ultra high magnetic field strength. The design of RF pulses for multiple channels is generally based on the solution of regularized least squares optimization problems, for which the regularization term is selected to control the integrated or peak pulse waveform amplitude. Unlike for single channel transmission systems, the SAR of parallel transmission systems is significantly influenced by interferences between the electric fields of the various transmit elements, which are not taken into account using conventional regularization terms. This work explores the effects upon SAR behavior of incorporating measurable electric field interactions into parallel transmission RF pulse design. The results of phantom experiments show that the global SAR during parallel transmission decreases when electric field interactions are incorporated in pulse design optimization.
Keywords