Reducing contamination while closing the gap: BASSI RF pulses in PASL

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Radiology

Background:

• Pulsed arterial spin labeling (PASL) is crucial for noninvasive brain perfusion measurement.
• Optimizing radiofrequency (RF) pulses is key to improving PASL accuracy by minimizing artifacts.
• Existing methods like FOCI and sinc pulses have limitations in selectivity and energy efficiency.

Purpose of the Study:

• To develop and evaluate Bandwidth-modulated selective saturation and inversion (BASSI) pulses for enhanced PASL.
• To minimize static spin contamination and enable smaller label gaps in PASL imaging.
• To compare the performance of BASSI pulses against conventional methods like FOCI and sinc pulses.

Main Methods:

• Parameterization of BASSI pulses for low RF energy PASL label pulses and selective saturation pulses.
• Simulations and phantom experiments comparing BASSI pulses with FOCI and sinc pulses.
• Development of a novel in vivo method to quantify static spin contamination.
• In vivo human studies comparing QUIPSS II/BASSI with Q2TIPS/FOCI sequences.

Main Results:

• BASSI pulses demonstrate high selectivity and uniform profiles.
• Simulations and phantom data show BASSI pulses outperform FOCI and sinc pulses in specific applications.
• The novel method successfully quantifies contamination effects.
• In vivo studies reveal a threefold reduction in residual contamination with QUIPSS II/BASSI compared to Q2TIPS/FOCI.
• High-quality in vivo perfusion images were acquired with a 2 mm label gap.

Conclusions:

• BASSI pulses offer superior performance for PASL applications, particularly in reducing static spin contamination.
• The developed BASSI-based PASL sequences allow for significantly improved accuracy and resolution.
• This work paves the way for more precise and efficient noninvasive perfusion imaging.