The diffusion sensitivity of fast steady-state free precession imaging

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Physics

Background:

• Steady-state free precession (SSFP) imaging is sensitive to water diffusion and motion.
• Previous theory suggested smaller flip angles increase diffusion sensitivity in SSFP.
• Understanding SSFP's diffusion sensitivity is crucial for advanced MRI applications.

Purpose of the Study:

• To investigate the enhanced diffusion sensitivity of SSFP imaging at low flip angles.
• To elucidate the theoretical basis for SSFP's diffusion sensitivity using echo pathway analysis.
• To validate theoretical predictions with experimental data from phantoms and human subjects.

Main Methods:

• Utilized partial partition analysis to examine echo pathways in SSFP.
• Conducted experimental SSFP imaging studies on phantoms and human brain.
• Applied theoretical diffusion attenuation models to experimental data.

Main Results:

• Experimental data confirmed substantially greater signal attenuation with small flip angles (< 30 degrees).
• Theoretical models reasonably fit experimental data, showing flip angle and TR dependence.
• Observed larger diffusion coefficients than expected, potentially due to other tissue motions.

Conclusions:

• SSFP imaging with low flip angles offers significantly enhanced diffusion sensitivity compared to conventional spin-echo methods.
• Stimulated echo pathways with long diffusion times contribute to enhanced diffusion sensitivity at low flip angles.
• Further investigation is needed to differentiate diffusion from other motion artifacts in SSFP.