An experimental model for MRI-detected measurements of oxygen uptake in the lungs

Oxygen, which is paramagnetic, influences the nuclear relaxation rate of Helium-3, and can be the limiting factor when hyperpolarized (HP) gases are used as inhaled contrast agents in MR lung imaging. The decay rate of a HP 3He NMR signal, acquired during a single breath-hold, will thus change as oxygen is exchanged with the bloodstream. We model this effect in vitro using a time-varying magnetic field gradient to mimic oxygen uptake in the lung. The goal of the study is to investigate the expected accuracy and precision with which oxygen concentrations and uptake rates can be extracted from lung imaging experiments performed in vivo. Particular emphasis is placed on the effects of varying signal-to-noise ratio and acquisition time. These experiments are expected to inform developments in the field of hyperpolarized gas MRI, and may lead to new tools for the treatment and detection of lung diseases and disorders.