Project Results

The initial 16 simulations have been completed on a standard 100 cc optical pumping cell. I found an unexpected instability in simulations with surfaces temperatures greater than 120 C. Although optical pumping setups have observed instabilities, the exact conditions are only known approximately. These results provide greater insight into the nature of the instability and guidance in how to proceed with a the second set of 16 simulations.  

About This Project

The American Lung Association estimates that 32 million Americans are affected by lung diseases, many of which are still not fully understood. Hyperpolarized xenon (HP Xe) MRI lung imaging is emerging as an important tool to better understand lung disease and develop treatments. However, the potency of HP Xe is up to three times less than its theoretical potential, which has hampered economical application. We’ve developed a computational model to identify inefficiencies in the process.

Ask the Scientists

What is the context of this research?

HP Xe gas is a powerful tool that is emerging as an important contrast agent for lung MRI. Due to the low tissue density, lung MRIs do not produce sufficient signal to resolve any structure. However, if a patient breathes in HP Xe before the scan, high resolution images of the lungs become relatively easy to produce. Researchers have used this gas to begin to better understand a number of lung diseases.

Unfortunately, the production of this gas is expensive. The production efficiencies have not met the expectations based on simple calculations. Important details of the process (for example gas flow patterns, convection, and gas density distributions) are not understood. These aspects are expected to strongly effect the production efficiencies and associated costs.

What is the significance of this project?

Recently, Freeman et al. (2014) determined that HP Xe production efficiency was 2-3 times less efficient than widely-used plug-flow models predicted. The reasons for these deficiencies is not yet known.

This project utilizes a new cost-effective, finite element method (FEM) model that is both expands upon previous studies(Fink et al. (2005), Fink et al. (2007) ) and provides a cost-effective platform for other researchers to explore new production setups. Previous FEM studies used prohibitivly expensive software (COMSOL), did not examine full, three-dimensional models, and used some simplifying assumptions. This study uses open-source (Elmer-CSC) software, a three-dimensional geometry, and more refined physical assumptions.

What are the goals of the project?

This project has two goals. The first is to validate a new, open-source FEM model for the production of HP Xe that includes all known fluid and thermodynamics, and also models diffusion of important intermediate species.

Two different geometries will be simulated under four common conditions. The results of these simulations will be compared to the efficiencies measured by Freeman et al. It is hypothesized that the model will accurately predict the deficiencies observed by Freeman.

The second goal is to investigate the causes of current inefficiencies in HP Xe production. In particular, it is hypothesized that convection currents in the reaction cell are more favorable when the cell is oriented vertically rather than horizontally.

See “More Information” for details.