T₂ quantification in brain using 3D fast spin-echo imaging with long echo trains.

Area of Science:

• Magnetic Resonance Imaging
• Quantitative Imaging

Background:

• Three-dimensional fast spin-echo (3D FSE) sequences are increasingly utilized in brain imaging for their high isotropic resolution and efficiency.
• These sequences often employ long echo trains and reduced refocusing angles, necessitating investigation into their T2 quantification capabilities.

Purpose of the Study:

• To investigate T2 quantification using 3D FSE sequences with long echo trains.
• To achieve higher resolution T2 mapping compared to established 2D methods.
• To optimize 3D FSE sequence design for accurate T2 fitting and contrast preservation.

Main Methods:

• Exploration of 3D FSE sequence design, including constant and variable flip angle trains.
• Utilized extended phase graph and Bloch equation simulations for parameter optimization.
• Validated optimized parameters in phantom experiments and in vivo brain imaging, comparing with 2D techniques.

Main Results:

• Optimized variable echo-train 3D FSE demonstrated T2 measurement accuracy comparable to 2D methods.
• Achieved a three-fold increase in slice resolution compared to 2D methods, with visually evident improvements in 3D T2 maps.
• T2 fitting was enhanced, and results aligned with standard multi-echo spin echo within 8-ms confidence limits.

Conclusions:

• 3D FSE with optimized long echo trains and variable refocusing angles provides accurate T2 mapping.
• Offers significant high-resolution benefits, enabling isotropic views and avoiding magnetization transfer effects.
• Optimized 3D sequences are recommended for T2 mapping requiring high anatomical detail.