Time-dependent diffusion MRI using multiple stimulated echoes

Area of Science:

• Magnetic Resonance Imaging
• Diffusion Tensor Imaging
• Biophysical Measurement

Background:

• Diffusion MRI is crucial for understanding tissue microstructure.
• Investigating diffusion-time dependency provides insights into water diffusion characteristics.
• Existing methods for acquiring diffusion-time dependent data can be time-consuming.

Purpose of the Study:

• To develop a novel, time-efficient pulse sequence for acquiring multiple diffusion-weighted images with distinct diffusion times in a single scan.
• To utilize multiple stimulated echoes (mSTE) combined with variable flip angles (VFA) for this purpose.

Main Methods:

• The proposed diffusion-weighted mSTE with VFA (DW-mSTE-VFA) sequence employs a series of RF pulses with VFA to generate multiple stimulated echoes.
• Each echo is acquired using an Echo Planar Imaging (EPI) echo train, enabling varying diffusion times within a single shot.
• The technique was validated on diffusion phantoms, fruit, and human brain and prostate tissues at 3T.

Main Results:

• DW-mSTE-VFA demonstrated high consistency (r=0.999) with a commercial spin-echo sequence for apparent diffusion coefficient (ADC) measurements in phantoms.
• The sequence showed similar diffusion-time dependency compared to standard stimulated echo sequences in fruit and brain.
• Significant diffusion-time dependency of ADC was observed in human brain (white and gray matter) and prostate (peripheral zone and central gland) tissues.

Conclusions:

• DW-mSTE-VFA is a time-efficient tool for diffusion MRI.
• This technique facilitates the investigation of diffusion-time dependency in various biological tissues.
• The findings highlight the importance of considering diffusion time in MRI studies.