Improved detection of homonuclear coupled spins with constant-time PRESS and broadband refocusing pulses

Introduction Constant-time point-resolved spectroscopy (CT-PRESS) [1] is a single voxel technique that simplifies the spectral pattern and permits the detection of Jcoupled resonances with high signal-to-noise ratio by using effective homonuclear decoupling [2]. The technique relies on non-selective refocusing, i.e., effective homonuclear decoupling is only achieved if the RF pulses refocus all the resonances in a J-coupled spin system. However, this cannot be achieved throughout the volume of the selected voxel due to the chemical-shift displacement error (CSDE) caused by the limited bandwidth of the sliceselective RF pulses, leading to signal loss for coupled resonances. In this study a broadband slice-selective 180° refocusing pulse (S-BURBOP [3]) was designed and implemented into CT-PRESS. It was evaluated and compared to a conventional Shinnar-Le Roux (SLR) pulse on a phantom and in vivo on healthy volunteers.