Simulating Non‐linear Chemical and Physical (CAP) Dynamics of Signal Amplification By Reversible Exchange (SABRE)

The hyperpolarization of nuclear spins by using parahydrogen (pH2) is a fascinating technique that allows spin polarization and thus the magnetic resonance signal to be increased by several orders of magnitude. Entirely new applications have become available. Signal amplification by reversible exchange (SABRE) is a relatively new method that is based on the reversible exchange of a substrate, catalyst and parahydrogen. SABRE is particularly interesting for in vivo medical and industrial applications, such as fast and low‐cost trace analysis or continuous signal enhancement. Ever since its discovery, many attempts have been made to model and understand SABRE, with various degrees of simplifications. In this work, we reduced the simplifications further, taking into account non‐linear chemical and physical (CAP) dynamics of several multi‐spin systems. A master equation was derived and realized using the MOIN open‐source software. The effects of different parameters (exchange rates, concentrations, spin–spin couplings) on relaxation and the polarization level have been evaluated and the results provide interesting insights into the mechanism of SABRE. The CAP model. The first non‐linear chemical and physical (CAP) model for signal amplification by reversible exchange (SABRE) has been developed (see figure). It has proven a very useful open source tool for evaluating hyperpolarization and unknown kinetic parameters of SABRE and beyond.