Thermally Polarized 129Xe Phantom for MR Imaging and Elastography in 9.4T MRI

Respiratory diseases account for three of the top ten causes of death worldwide, causing more than 8 million deaths per year. One of the ways to tackle the problem is the improvement of early-diagnostic techniques: it can be accomplished first by meeting the demand for high quality images of the lungs’ airways to identify airspace obstructions and secondly, addressing the need for quantifying mechanical properties of the lung parenchyma, whose changes are often associated with disabling lung diseases. Magnetic resonance imaging with hyperpolarized 129Xe gas is a promising non-invasive imaging technique for high-resolution airspace imaging, and 129Xe magnetic resonance elastography (MRE) could be an interesting technique for estimating lung parenchyma mechanical properties. The presented study aimed to develop a 129Xe phantom for quality assessment in a pre-clinical MRI at 9.4 Tesla. Given the transiency of gas polarization, in order to have a long-lasting phantom, 129Xe is highly pressurized instead of hyperpolarized: the SNR is improved just by increasing 129Xe density inside the phantom. We provide a method to create a 129Xe phantom with easy accessible materials both MRI compatible and able to withstand high pressures. The phantom is filled with a customizable Xenon-Oxygen mixture to replicate different T1 relaxation times. Inside the phantom, a silicon gel is used to enable both proton and Xenon imaging, assisting with image registration and interpretation. The diffusion of the Xenon inside the gel has been demonstrated, showing a large chemical shift relative to the 129Xe in the gas phase (193 ppm). The solubility of the gas can be utilized in future works to demonstrate, for the first time, the feasibility of 129Xe MRE.