Molecular imaging using endogenous molecules has generated a lot of interest because the methodology does not have the adverse effects of gadolinium (Gd) contrast agents and has clinical benefits in pediatric patients or patients with a contraindication for the use of an exogenous contrast agent.
Amide proton transfer (APT) imaging has recently emerged as an important contrast mechanism for magnetic resonance Imaging (MRI) in the field of molecular and cellular imaging which has higher sensitivity and spatial resolution than magnetic resonance spectroscopy technique.
Amide proton transfer (APT) imaging is a novel molecular MRI technique that detects low- concentration endogenous mobile proteins and peptides in tissue noninvasively. It can indirectly reflect intra cellular metabolic change and physiological and pathological information in vivo. APT imaging is able to detect tissue pH changes in stroke (where pH decreases) and identify the spatial extent and pathological grade of some tumors due to increased mobile protein and peptide.
APT imaging has added a new dimension to in vivo molecular imaging by its ability to demonstrate mobile proteins and physicochemical properties of tissue. High sensitivity in reflecting protein contents enables various applications in brain tumor imaging and stroke imaging in terms of diagnosis and treatment monitoring.
In this  review,  we  describe  the  basic  concepts  of APT imaging, particularly with regard to the benefit in clinics from the current literature .Clinical applications of APT imaging are described from two perspectives: in the diagnosis and  monitoring  of  the treatment response in brain tumor by reflecting endogenous mobile proteins and peptides, and in the potential for stroke imaging with respect to tissue acidity.