Using the amide proton signals of intracellular proteins and peptides to detect pH effects in MRI

Area of Science:

• Biomedical Imaging
• Biophysics
• Medical Physics

Background:

• Magnetic resonance imaging (MRI) traditionally uses water proton signals for physiological assessment.
• Developing novel MRI contrast mechanisms is crucial for advanced diagnostics.

Purpose of the Study:

• To demonstrate pH-sensitive MRI contrast using amide proton transfer (APT).
• To explore APT's potential for detecting acute stroke via pH changes.

Main Methods:

• Exploited exchange between water protons and endogenous mobile protein/peptide amide protons.
• Calibrated pH dependence using phosphorus spectroscopy and proton exchange spectroscopy.
• Noninvasively imaged pH effects in ischemic rat brain.

Main Results:

• Achieved sensitive detection of pH changes via amide proton transfer (APT).
• Demonstrated successful in vivo imaging of pH alterations in a rat stroke model.
• Established a link between pH, protein content, and MRI signal.

Conclusions:

• Amide proton transfer (APT) MRI provides intrinsic pH contrast.
• APT offers potential for diagnostic tools in clinical imaging, including stroke detection.
• This technique can also provide protein- and/or peptide-content contrast.