T₁-corrected fat quantification using chemical shift-based water/fat separation: application to skeletal muscle

Area of Science:

• Medical Imaging
• Biophysics
• Quantitative MRI

Background:

• Accurate quantification of intermuscular adipose tissue (IMAT) is crucial for metabolic health assessment.
• Chemical shift-based water/fat separation methods, such as iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL), are used for IMAT quantification.
• A significant confounding factor in IDEAL is the T(1) difference between muscle and fat, leading to overestimation of the fat fraction.

Purpose of the Study:

• To introduce a novel approach for water/fat separation in dual flip angle experiments.
• To develop a new strategy for selecting flip angles, termed the unequal small flip angle approach, to improve T(1) correction efficiency.
• To enhance the noise performance of T(1) correction in IMAT quantification.

Main Methods:

• Implementation of a novel water/fat separation technique for dual flip angle experiments.
• Development of the unequal small flip angle approach for selecting optimal flip angles.
• Comparison of noise performance against equal small flip angles and large flip angle methods.

Main Results:

• The unequal small flip angle approach demonstrates superior noise performance compared to existing methods.
• This novel approach improves the efficiency of the T(1) correction step in water/fat separation.
• Assumptions of T(1) independence for muscle water and fat signals at specific flip angles contribute to improved noise characteristics.

Conclusions:

• The unequal small flip angle approach offers a more noise-efficient method for T(1) correction in dual flip angle MRI.
• This technique can lead to more accurate intermuscular adipose tissue quantification by mitigating T(1) bias.
• The proposed method provides a valuable advancement for quantitative MRI in metabolic research.