Validating in vivo hyperpolarized ¹²⁹ Xe diffusion MRI and diffusion morphometry in the mouse lung.

Area of Science:

• Pulmonary imaging
• Medical physics
• Animal models

Background:

• Diffusion and lung morphometry imaging with hyperpolarized gases offer noninvasive quantification of pulmonary microstructure.
• The influence of cardiac motion on these measurements has not been previously investigated.
• Validation of 129Xe diffusion morphometry against histology in mice is lacking.

Purpose of the Study:

• To investigate the effect of cardiac motion on diffusion imaging.
• To validate 129Xe diffusion morphometry in mice.
• To assess the utility of this technique in preclinical research.

Main Methods:

• Mice underwent gradient-echo-based diffusion imaging with and without cardiac gating.
• Apparent diffusion-coefficient (ADC) maps were generated.
• Diffusion-weighted images were analyzed using Bayesian probability theory to derive morphometric parameters, compared with histology.

Main Results:

• Cardiac gating showed no significant impact on ADC measurements (0.020 cm²/s).
• Diffusion morphometry yielded accurate acinar dimension measurements (e.g., alveolar sleeve depth, acinar duct radii) comparable to histology.
• High agreement was observed between imaging-derived and histological measurements.

Conclusions:

• Cardiac motion has a negligible effect on 129Xe ADC measurements in mice, suggesting minimal impact in humans.
• Hyperpolarized 129Xe diffusion morphometry provides accurate, noninvasive mapping of lung microstructure dimensions.
• This technique holds promise for quantifying pulmonary microstructure in mouse models of lung disease.