Hyperpolarized 129Xe phase-selective imaging of mouse lung at 9.4T using a continuous-flow hyperpolarizing system

Area of Science:

• Pulmonary Medicine
• Medical Imaging
• Biophysics

Background:

• Hyperpolarized (HP) 129Xe magnetic resonance (MR) imaging is a promising technique for evaluating lung function.
• Assessing regional gas diffusion, perfusion, and ventilation non-invasively is crucial for understanding lung physiology and disease.

Purpose of the Study:

• To utilize a continuous-flow hyperpolarizing (CF-HP) system for acquiring gas- and dissolved-phase 129Xe MR images of mouse lungs.
• To investigate the dynamics of xenon replenishment in the lung using phase-selective pulses and map the dissolved-to-gas phase xenon ratio.

Main Methods:

• Employed a continuous-flow hyperpolarizing (CF-HP) system and a standard gradient echo sequence with chemical shift selective excitation.
• Utilized a phase-selective 90-degree pulse to visualize xenon magnetization replenished during the repetition time (TR).
• Acquired both gas- and dissolved-phase 129Xe images to calculate the ratio of dissolved- to gas-phase 129Xe (Mdissolved/Mgas).

Main Results:

• Successfully acquired gas- and dissolved-phase 129Xe images from mouse lungs.
• Determined the ratio of dissolved- to gas-phase 129Xe (Mdissolved/Mgas) to be approximately 0.05 to 0.08 in peripheral lung regions.
• Observed that dissolved-phase 129Xe replenishment via diffusion and perfusion is faster than gas-phase replenishment via ventilation.

Conclusions:

• The continuous-flow hyperpolarizing system enables effective HP 129Xe imaging with longer TRs.
• Phase-selective pulses are valuable for visualizing specific xenon magnetization phases.
• This approach provides insights into lung gas transport mechanisms, distinguishing between ventilation, diffusion, and perfusion.