Longitudinal (T1) relaxation is usually considered as disadvantageous for MRI with hyperpolarized (hp) spin systems as it leads to depolarization and hence to a loss in the observable signal. However, it has been demonstrated previously that quadrupolar T1 relaxation of the hyperpolarized noble gas isotope 83Kr (nuclear spin I = 9/2) can utilized to probe surfaces that are in contact with the noble gas. For example, surface quadrupolar relaxation (SQUARE) T1 maps of hp 83Kr are indicative of an emphysema model in excised rodent lungs . MRI at the very low resonance frequency of 83Kr (i.e. 11.5 MHz at 7 T) requires hyperpolarization through spin exchange optical pumping (SEOP) similar to that for the hp 129Xe production. However, as a consequence of quadrupolar relaxation, hp 83Kr cannot be concentrated from buffer gases of the laser pumping process through cryogenic separation or through membranes without depolarization. Therefore, a new production methodology was developed that uses molecular hydrogen as buffer gas during SEOP and its subsequent removal through catalytic combustion . Currently, novel instrumentation is being developed to make this approach feasible for clinical applications.
Similar to 83Kr MRI SQUARE contrast, paramagnetic relaxation of hp 129Xe can be applied to study surfaces, in particular for chemical engineering and materials science applications. Generally, MRI of fluid flow can probe the structure-transport relationship , and we use hp 129Xe to study gas transport and reactive zones in diesel catalysts that consist of materials with hierarchical pore structure. The accessibility of catalytic and paramagnetic centers can be probed through 129Xe relaxation measurements provide insights into catalytic activity in these systems.
 DML Lilburn et al., J. R. Soc. Interface, 12, (2015), 20150192.
 NJ Rogers et al., Proc. Nat. Acad. Sci., 113, (2016), 3146-3168.
 GE Pavlovskaya et al, Physical Review Fluids, 3, (2018), 044102_1-20.