J-refocused semi-LASER spectroscopy at 7T: proof-of-concept and application in the human brain at 7T

Spin-echo sequences suffer from loss of signal due to J-modulation for coupled spins. Previously, it was shown that adding a π/2 pulse between two π pulses in a double spin-echo sequence partially refocuses some of the J-evolution. However, the potential of such sequence at ultrahigh field is limited due to the large chemical shift displacement error. Here, we propose a J-refocused variant of the sLASER sequence (J-sLASER) to improve quantification of J-coupled metabolites at ultrahigh field. Significant improvement in quantitation of J-coupled metabolites is illustrated using simulation, phantom and in vivo measurements in the human brain.