pH Imaging Using Chemical Exchange Saturation Transfer (CEST) MRI

Acid-base homeostasis is an essential process for maintaining proper pH levels in the body, with alterations in this process potentially signaling pathology. While monitoring urine pH, blood gases and other assays can provide information on the overall systemic pH, it is desirable to get more localized knowledge to assist diagnosis. Various non-invasive methods have been developed with Chemical Exchange Saturation Transfer (CEST) MRI now emerging as a particularly intriguing technology for detecting pH. In this review, we provide an overview of the paramagnetic and diamagnetic CEST probes available for producing pH maps, describe in depth the various methods to collect CEST MRI data and post-process the resulting images to create pH maps and describe how this has been applied for detecting renal injury, mapping the pH of tumors and monitoring the health of transplanted therapeutic cells. Finally, we will provide an outlook of the possibilities to translate this technology into patients.