Multiple echo multi-shot diffusion sequence.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biomedical Engineering
• Medical Physics

Background:

• Simultaneous measurement of T2 relaxation time and diffusion coefficients is valuable for applications like skeletal muscle imaging.
• Existing multi-echo single-shot MRI sequences face limitations due to long echo read-out times, resulting in long minimum echo times.
• This restricts their application to tissues with longer T2 values, necessitating alternative approaches.

Purpose of the Study:

• To develop and validate a multi-shot MRI approach for simultaneous measurement of T2 relaxation times and diffusion coefficients.
• To overcome the limitation of long echo times in existing single-shot sequences.
• To enable accurate assessment in tissues with short T2 values, such as skeletal muscle.

Main Methods:

• A multi-shot dual-echo Echo Planar Imaging (EPI) sequence was modified.
• The sequence incorporated diffusion gradients and echo navigators.
• Independent diffusion gradients were integrated into either of the two echoes to allow for shorter echo times.

Main Results:

• The multi-shot approach significantly reduced echo times compared to previous methods.
• T2 relaxation time and mean diffusivity measurements demonstrated good agreement with gold standard sequences.
• Validation was performed using phantom data and in vivo calf muscle scans from healthy volunteers.

Conclusions:

• A fast and accurate MRI method for simultaneous T2 and diffusion coefficient measurement has been developed.
• The proposed multi-shot technique effectively addresses limitations of prior sequences.
• The method shows promise for in vitro and in vivo applications, particularly in skeletal muscle studies.