BISTRO: an outer-volume suppression method that tolerates RF field inhomogeneity

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Radiofrequency Pulse Design
• Signal Processing

Background:

• Achieving frequency-selective signal suppression in MRI is challenging, particularly with inhomogeneous radiofrequency (RF) fields from surface coils.
• Existing methods for outer-volume suppression (OVS) may struggle with RF field inhomogeneity, limiting their applicability.

Purpose of the Study:

• To introduce and evaluate a novel technique, B1-insensitive train to obliterate signal (BISTRO), for robust frequency-selective signal suppression.
• To demonstrate BISTRO's effectiveness for outer-volume suppression (OVS) in MRI, especially under RF field inhomogeneity.

Main Methods:

• BISTRO utilizes multiple amplitude- and frequency-modulated (FM) pulses interleaved with spoiler gradients.
• Bloch simulations were employed to elucidate BISTRO's principles and theoretical performance.
• Experimental validation was conducted using MRI and spectroscopic imaging on phantoms and in vivo animal and human brains.

Main Results:

• BISTRO demonstrated high-quality, broadband suppression with well-defined borders, utilizing offset-independent adiabaticity FM pulses.
• Simulations and experiments confirmed BISTRO's effectiveness in the presence of RF field inhomogeneity.
• The technique operates at attainable peak RF power levels with comparable RF energy deposition to existing OVS methods.

Conclusions:

• BISTRO provides a reliable method for frequency-selective signal suppression tolerant to RF field inhomogeneity.
• The technique is suitable for applications like water and outer-volume suppression in MRI using surface coils.
• BISTRO offers a practical and effective solution for challenging suppression tasks in magnetic resonance imaging.