Abstract #0207

Parallel Transmit using 3D Spokes RF Pulses for Improved B1+ Homogeneity over 3D Volumes

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.