RARE/turbo spin echo imaging with Simultaneous Multislice Wave-CAIPI.

Area of Science:

• Magnetic Resonance Imaging (MRI) Physics
• Medical Imaging Acceleration Techniques
• Radiofrequency Pulse Design

Background:

• Accelerated MRI is crucial for reducing scan times and improving patient comfort.
• Simultaneous MultiSlice (SMS) imaging allows exciting multiple slices concurrently, but often incurs g-factor penalties impacting image quality.
• High radiofrequency (RF) power deposition and Specific Absorption Rate (SAR) are limitations for advanced MRI sequences.

Purpose of the Study:

• To achieve highly accelerated RARE/Turbo Spin Echo (TSE) imaging.
• To implement Simultaneous MultiSlice (SMS) Wave-CAIPI acquisition.
• To reduce the g-factor penalty and SAR associated with accelerated imaging.

Main Methods:

• Employed SMS Wave-CAIPI, utilizing sinusoidal gradient waveforms for efficient k-space coverage and 3D aliasing spread.
• Introduced novel MultiPINS radiofrequency (RF) pulses to significantly decrease power deposition of multiband (MB) refocusing pulses.
• Explored the synergy of Wave-CAIPI and MultiPINS for enhanced encoding and reduced RF power.

Main Results:

• Achieved whole-brain coverage at 1 mm isotropic resolution in 70 seconds with an effective MB factor of 13.
• Demonstrated low g-factor penalties (gmax=1.34, gavg=1.12) with Wave-CAIPI and MultiPINS, significantly outperforming blipped-CAIPI (gmax=3.24).
• Reported substantial reductions in SAR (4.2x lower for MB, 1.9x lower for PINS) and peak RF power (19.4x lower for MB, 3.9x lower for PINS) compared to conventional pulses.

Conclusions:

• The combination of Wave-CAIPI and MultiPINS pulses enables highly accelerated RARE/TSE imaging.
• This approach significantly reduces SAR and RF power deposition.
• The technique achieves acceleration with minimal signal-to-noise ratio (SNR) penalty.