Creatine mapping of the brain at 3T by CEST MRI

Area of Science:

• Neuroimaging
• Biochemistry
• Magnetic Resonance Imaging

Background:

• Creatine (Cr) plays a vital role in cellular energy homeostasis.
• Accurate mapping of brain Cr concentrations is crucial for understanding neurological conditions.
• Current methods for Cr quantification in vivo have limitations.

Purpose of the Study:

• To evaluate the feasibility of creatine (Cr) mapping in the brain at 3 Tesla (3T) using guanidino (Guan) proton resonance.
• To investigate the contributions of Cr and proteins to the GuanCEST signal.
• To assess the potential of GuanCEST for intracellular pH mapping.

Main Methods:

• Utilized wild type and knockout mice with altered Cr concentrations.
• Applied two-step Bloch-McConnell fitting to quantify the Cr proton exchange rate.
• Simulated the pH response of GuanCEST to assess its pH mapping capabilities.

Main Results:

• A distinct Guan proton peak at 2.0 ppm was observed in mouse brains at 3T.
• The creatine chemical exchange saturation transfer (CrCEST) signal contributed approximately 23% to the total GuanCEST signal.
• An estimated exchange rate of 200-300 s⁻¹ was determined for Cr Guan protons.
• Simulations indicated GuanCEST's sensitivity to intracellular pH changes, particularly at lower B₁ field strengths.

Conclusions:

• Creatine chemical exchange saturation transfer (CrCEST) mapping is achievable at 3T.
• This technique holds promise for non-invasively detecting both intracellular pH and Cr concentration in the brain.
• Further research can explore its clinical applications in neurological disorders.