Rebecca E Feldman1, Haisam M Islam2, Junqian Xu1,3, Priti Balchandani1. 1. Translational and Molecular Imaging Institution, Icahn School of Medicine at Mount Sinai, New York, New York, USA. 2. Bioengineering Department, Stanford University, Stanford, California, USA. 3. Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA.
Abstract
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° Power Independent of Number of Slices (PINS) pulse and a matched-phase 90° 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° pulse. The SLR polynomials for the 180° pulse were then used to create a matched-phase 90° 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 B1 -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 B1 -insensitivity when compared with a conventional spin echo.
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 SMSspin echo imaging challenging. We designed an adiabatic 180° Power Independent of Number of Slices (PINS) pulse and a matched-phase 90° 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° pulse. The SLR polynomials for the 180° pulse were then used to create a matched-phase 90° 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 B1 -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 B1 -insensitivity when compared with a conventional spin echo.
Keywords:
MRI; PINS; SEAMS; SEmi-Adiabatic Matched-Phase Spin Echo; power independent of number of slices; simultaneous multi-slice; spin echo; ultrahigh field
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