Airspace Dimension Assessment (AiDA) by inhaled nanoparticles: benchmarking with hyperpolarised Xe diffusion-weighted lung MRI.

Enlargements of distal airspaces can indicate pathological changes in the lung, but accessible and precise techniques able to measure these regions are lacking. Airspace Dimension Assessment with inhaled nanoparticles (AiDA) is a new method developed for in vivo measurement of distal airspace dimensions. The aim of this study was to benchmark the AiDA method against quantitative measurements of distal airspaces from hyperpolarised Xe diffusion-weighted (DW)-lung magnetic resonance imaging (MRI). AiDA and Xe DW-MRI measurements were performed in 23 healthy volunteers who spanned an age range of 23-70 years. The relationship between the Xe DW-MRI and AiDA metrics was tested using Spearman's rank correlation coefficient. Significant correlations were observed between AiDA distal airspace radius (r) and mean Xe apparent diffusion coefficient (ADC) (p < 0.005), distributed diffusivity coefficient (DDC) (p < 0.001) and distal airspace dimension (Lm) (p < 0.001). A mean bias of - 1.2 µm towards r was observed between Xe Lm and r, indicating that r is a measure of distal airspace dimension. The AiDA R intercept correlated with MRI Xe α (p = 0.02), a marker of distal airspace heterogeneity. This study demonstrates that AiDA has potential to characterize the distal airspace microstructures and may serve as an alternative method for clinical examination of the lungs.