Amide Proton Transfer Imaging in the Central Nervous System: Recent Advances and Clinical Applications

Amide proton transfer (APT) imaging, as a novel magnetic resonance molecular imaging technique based on the chemical exchange saturation transfer (CEST) effect, indirectly reflects molecular-level information such as tissue protein concentration, pH, and microenvironment by detecting the exchange between intracellular free water and amide protons in proteins/peptides. Since it was first proposed by Professor Jinyuan Zhou in 2003, the technique has achieved significant progress in theoretical modeling, sequence optimization, and clinical translation, particularly in its expanding application to central nervous system diseases. In recent years, APT has been widely used for tumor grading, stroke staging, early identification of hypoxic-ischemic encephalopathy (HIE), and pathological tracking of neurodegenerative diseases. This review systematically summarizes the principles and advantages of APT imaging, with a focus on its recent applications in brain tumors, cerebral infarction, and neurodegenerative diseases. It also discusses signal variation characteristics and underlying mechanisms in different disease states, as well as current clinical applications and technical challenges.Keywords: Amide proton transfer (APT); chemical exchange saturation transfer (CEST); magnetic resonance molecular imaging; central nervous system (CNS); brain tumor; cerebral infarction; neurodegenerative disease