Parallel-transmission-enabled 3D T2-weighted imaging of the human brain at 7 Tesla

Purpose: At ultra-high magnetic field, B1 + and ΔB0 non-uniformities cause undesired contrast and signal inhomogeneities. Tailored radiofrequency (RF) pulses exploiting parallel transmission (pTX) have already demonstrated their ability to mitigate these phenomena, especially in the framework of T1-weighted imaging . Yet the design of refocusing pulses employed in T2-weighted imaging remains challenging due to the additional demand of a rotation of the magnetization vector. In this work, we use the gradient ascent pulse engineering (GRAPE) combined with the successfully demonstrated kT-point 4 method to design all the independent yet phase-coherent non-selective refocusing pulses of a variable flip angle turbo spin echo sequence (SPACE). Severe B1 + and ΔB0 inhomogeneities are thus mitigated and whole brain T2-weighted image quality is improved at 7 T.