A Novel CEST-Based Approach for Reliably Assessing Skeletal Muscle Oxidative Phosphorylation: OXCEST

Area of Science:

• Biomedical Engineering
• Magnetic Resonance Imaging
• Metabolic Imaging

Background:

• Skeletal muscle oxidative phosphorylation (OXPHOS) is crucial for energy metabolism.
• Accurate assessment of OXPHOS is vital for understanding muscle function and disease.
• Current methods for measuring OXPHOS have limitations in accessibility and resolution.

Purpose of the Study:

• To develop and validate a novel Chemical Exchange Saturation Transfer (CEST) MRI method, termed OXCEST, for mapping skeletal muscle OXPHOS.
• To assess the reliability and accuracy of the OXCEST method in quantifying creatine (Cr) recovery post-exercise.

Main Methods:

• The OXCEST method utilizes two frequency offsets to acquire creatine-weighted CEST maps.
• It models pre-exercise MTR_asym as a function of B₀ to account for field inhomogeneity.
• Post-exercise changes in MTR_asym are analyzed to quantify Cr-related recovery, validated against ³¹P-MRS.

Main Results:

• The B₀ correction function demonstrated high reliability across different muscle groups (R² > 0.87).
• OXCEST successfully captured exercise-induced increases in MTR_asym, showing mono-exponential recovery.
• OXCEST-derived creatine recovery time constant (T_Cr) showed significant correlation (R² = 0.83) with ³¹P-MRS T_PCr.

Conclusions:

• OXCEST provides a reliable method for assessing post-exercise creatine recovery in skeletal muscle.
• The developed OXCEST technique shows good agreement with the gold standard ³¹P-MRS.
• This novel MRI method holds promise for non-invasive evaluation of muscle metabolic function.