A SEmi-Adiabatic matched-phase spin echo (SEAMS) PINS pulse-pair for B1 -insensitive simultaneous multislice imaging

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biophysics
• Pulse Sequence Design

Background:

• Simultaneous multislice (SMS) imaging accelerates MRI acquisition.
• High magnetic fields (e.g., 7 Tesla) present challenges for SMS spin echo imaging due to RF inhomogeneity and power deposition.
• Existing SMS techniques struggle with B1-field variations at higher field strengths.

Purpose of the Study:

• To develop a novel pulse sequence for robust SMS spin echo imaging at high magnetic fields.
• To address challenges of RF inhomogeneity and power deposition in 7 Tesla SMS imaging.
• To design an adiabatic Power Independent of Number of Slices (PINS) pulse pair for improved B1-insensitivity.

Main Methods:

• Designed an adiabatic 180° PINS pulse using the Shinnar Le-Roux (SLR) algorithm.
• Generated a matched-phase 90° PINS pulse from the SLR polynomials.
• Developed the SEmi-Adiabatic Matched-phase Spin echo (SEAMS) PINS sequence.
• Validated the pulse-pair performance in phantom and in vivo experiments.

Main Results:

• Simulations, phantom, and in vivo results confirmed multislice imaging capability.
• The SEAMS PINS pulse-pair demonstrated improved B1-insensitivity.
• Effective performance was observed at RF amplitudes up to 40% above the adiabatic threshold.

Conclusions:

• The SEAMS PINS approach enables multislice spin echo imaging with enhanced B1-insensitivity.
• This method offers a significant improvement over conventional spin echo sequences in challenging high-field environments.
• The developed sequence is suitable for applications requiring faster and more reliable MRI acquisition at 7 Tesla.