Double half RF pulses for reduced sensitivity to eddy currents in UTE imaging

Area of Science:

• Magnetic Resonance Imaging
• Pulse Sequence Design

Background:

• Ultrashort echo time (ште) imaging using half radiofrequency (RF) pulse excitation faces challenges due to eddy currents from slice-select gradients distorting the RF pulse profile.
• This distortion can lead to inaccurate imaging and quantification, particularly for tissues with varying T2 relaxation times.

Purpose of the Study:

• To develop novel RF pulse designs that are less sensitive to eddy current-induced distortions in ште imaging.
• To improve slice selectivity and accuracy in quantitative MRI, especially for short T2 components.

Main Methods:

• Introduction of two new pulse designs: the double half pulse and the inverted double half pulse.
• Evaluation of T2-dependent slice profiles and their sensitivity to eddy currents.
• Experimental validation of improved slice selectivity and R2* quantitation accuracy.

Main Results:

• The double half pulse enhances slice selectivity for long T2 components.
• The inverted double half pulse effectively suppresses unwanted long T2 signal.
• Both pulses mitigate the contamination of the desired slice by out-of-slice signals.
• Substantially improved slice selectivity and R2* quantitation accuracy were demonstrated experimentally.

Conclusions:

• The presented RF pulses offer improved performance in ште imaging by reducing eddy current sensitivity.
• These pulses provide a more robust and potentially faster alternative to traditional gradient characterization methods for accurate MRI.
• The new pulse designs are effective for short T2 imaging and quantification.