Molecular Imaging Using Endogenous Cellular Proteins.

Amide proton transfer (APT) imaging is a novel molecular MRI technique that generates image contrast based on endogenous cellular proteins in tissue. Theoretically, the APT-MRI signal depends primarily on the mobile amide proton concentration and amide proton exchange rates (which are related to tissue pH). The APT technique has been used for non-invasive pH imaging in stroke (where pH drops) and protein content imaging in tumor (where many proteins are overexpressed). Notably, it has been recently demonstrated in animal models that the APT-MRI signal is a unique imaging biomarker to distinguish between radiation necrosis and active tumor. In this paper, we will briefly introduce the basic principle of APT imaging and review its current successful applications for the imaging of stroke and the imaging of brain tumors in animal models and in patients.