Using adiabatic inversion pulses for long-T2 suppression in ultrashort echo time (UTE) imaging

Area of Science:

• Medical Imaging
• Magnetic Resonance Imaging (MRI)
• Biophysics

Background:

• Conventional MRI struggles to visualize tissues with very short T2 relaxation times.
• Tissues like tendons, menisci, calcifications, and cortical bone have short T2 values and are often obscured.
• Ultrashort echo time (UTE) imaging offers potential for visualizing these tissues.

Purpose of the Study:

• To develop and validate a novel method for suppressing long T2 tissue signals in UTE imaging.
• To improve the contrast and visualization of short T2 tissues.

Main Methods:

• Utilized adiabatic inversion pulses with narrow bandwidth to selectively invert long T2 components.
• Combined images prepared with and without inversion pulses for suppression.
• Incorporated fat suppression by applying pulses on fat and water resonances.
• Employed scaling factors to compensate for relaxation during preparation pulses.
• Adiabatic pulses ensure insensitivity to radiofrequency inhomogeneities.

Main Results:

• Demonstrated effective suppression of long T2 components using adiabatic inversion pulses.
• Simulations and phantom experiments validated the contrast enhancement and scaling factor selection.
• In vivo 2D UTE imaging of the ankle and lower leg showed robust long T2 suppression.
• Excellent visualization of cortical bone and tendons was achieved.

Conclusions:

• The proposed adiabatic inversion pulse method effectively suppresses long T2 tissues in UTE imaging.
• This technique significantly enhances the contrast of short T2 tissues, improving diagnostic capabilities.
• The method is robust and suitable for in vivo imaging of musculoskeletal structures.