Mohammad Mehdi Khalighi1, Manojkumar Saranathan2, William Grissom3, Adam B. Kerr4, Ron Watkins2, Brian K. Rutt2
1Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA; 2Department of Radiology, Stanford University, Stanford, CA, USA; 3Imaging Technologies Lab, General Electric Global Research, Garching B. Munchen, Germany; 4Department of Electrical Engineering, Stanford University, Stanford, CA, USA
B1+ inhomogeneity is a major issue at high field. We introduce a 3D spokes RF pulse designed to improve volumetric B1+ homogeneity; this is achieved by adding z-axis phase encoding to the more conventional 2D spokes pulse design. We show that 2ch pTx using our new 3D spokes pulses improves B1+ uniformity over a complete slab even compared to 2D spokes pulses, and more substantially (factor of 2) compared to conventional quadrature excitation. We have tested experimentally this new 3D spokes pulse concept on a 2-ch pTx-enabled 7T scanner and show the B1+ homogeneity benefits in phantoms and volunteer brain.