Codes to generate figures of the NBM 2022 review article on CEST(B0) by Moritz Zaiss, Tao Jin, Seong-Gi Kim, and Daniel Gochberg doi will be shared here as soon as available
Theory of Chemical Exchange Saturation Transfer MRI in the context of different magnetic fields
Moritz Zaiss, Tao Jin, Seong-Gi Kim, and Daniel F Gochberg
Abstract
Chemical Exchange Saturation Transfer MRI is a versatile MRI method that provides contrast based on the level of molecular and metabolic activity. This contrast arises from indirect measurement of protons in low concentration molecules that are exchanging with the abundant water proton pool. The indirect measurement is based on magnetization transfer of rf-prepared magnetization from the small pool to the water pool. The signal can be modeled by the Bloch-McConnell equations combining standard magnetization dynamics and chemical exchange processes. In this article, we will review analytical solutions of the Bloch-McConnell equations and especially the derived CEST signal equations and their implications. The analytical solutions give direct insight on the dependency of measurable CEST effects on underlying parameters such as the exchange rate and concentration of the solute pools, but also on the system parameters such as the rf irradiation field B1 as well as the static magnetic field B0. These theoretical field strength dependencies and their influence on sequence design are highlighted herein. In vivo results of different groups making use of these field strength benefits/dependencies are reviewed and discussed.