Near-contiguous spin echo imaging using matched-phase RF and its application in velocity-selective arterial spin...

Area of Science:

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

Background:

• Multislice MRI is limited by inter-slice crosstalk from imperfect slice profiles.
• Minimizing slice spacing is crucial for improving imaging efficiency and resolution.

Purpose of the Study:

• To minimize slice spacing in multislice imaging using matched-phase RF pulses.
• To demonstrate the application of this technique in velocity-selective arterial spin labeling (VSASL) for cerebral blood flow (CBF) imaging.

Main Methods:

• Designed a spin-echo matched-phase 90°-180° RF pulse pair using the Shinnar-Le Roux algorithm.
• Compared longitudinal and transverse slice profiles of matched-phase RF and sinc-based RF pulses via simulations and measurements.
• Performed VSASL in volunteers, calculating the standard deviation of CBF time series to assess ASL signal stability.

Main Results:

• Matched-phase RF pulses sharpened the longitudinal slice profile without signal-to-noise ratio loss.
• VSASL imaging with matched-phase RF pulses reduced the temporal standard deviation of CBF measurements by 33% (from 48 to 32 mL/100 g/min).
• Improved CBF image quality was observed using matched-phase RF pulses.

Conclusions:

• Near-contiguous multislice imaging is achievable with matched-phase RF pulses.
• This method effectively minimizes inter-slice crosstalk without compromising signal-to-noise ratio or signal stability.
• Matched-phase RF pulses enhance the quality of VSASL CBF imaging.