A SEmi-Adiabatic matched-phase spin echo (SEAMS) PINS pulse-pair for B sub(1)-insensitive simultaneous multislice imaging

Purpose Simultaneous multislice (SMS) imaging is a powerful technique that can reduce image acquisition time for anatomical, functional, and diffusion weighted magnetic resonance imaging. At higher magnetic fields, such as 7 Tesla, increased radiofrequency (RF) field inhomogeneity, power deposition, and changes in relaxation parameters make SMS spin echo imaging challenging. We designed an adiabatic 180 degree Power Independent of Number of Slices (PINS) pulse and a matched-phase 90 degree PINS pulse to generate a SEmi-Adiabatic Matched-phase Spin echo (SEAMS) PINS sequence to address these issues. Methods We used the adiabatic Shinnar Le-Roux (SLR) algorithm to generate a 180 degree pulse. The SLR polynomials for the 180 degree pulse were then used to create a matched-phase 90 degree pulse. The pulses were sub-sampled to produce a SEAMS PINS pulse-pair and the performance of this pulse-pair was validated in phantoms and in vivo. Results Simulations as well as phantom and in vivo results, demonstrate multislice capability and improved B sub(1)-insensitivity of the SEAMS PINS pulse-pair when operating at RF amplitudes of up to 40% above adiabatic threshold. Conclusion The SEAMS PINS approach presented here achieves multislice spin echo profiles with improved B sub(1)-insensitivity when compared with a conventional spin echo. Magn Reson Med 75:709-717, 2016.