Airspace Dimension Assessment (AiDA) by inhaled nanoparticles: benchmarking with hyperpolarised 129Xe diffusion-weighted lung MRI

Madeleine Petersson-Sjögren,Jakob Löndahl,Per Wollmer,Ho-Fung Chan,Graham Norquay,Jim M Wild,Lars E Olsson,Guilhem J Collier

doi:10.1038/s41598-021-83975-7

Madeleine Petersson-Sjögren, Jakob Löndahl + Show 6 more

Open Access

https://doi.org/10.1038/s41598-021-83975-7

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Journal: Scientific Reports	Publication Date: Feb 25, 2021
Citations: 9	License type: open-access

Affiliation: Lund University, University of Sheffield

Abstract

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 129Xe diffusion-weighted (DW)-lung magnetic resonance imaging (MRI). AiDA and 129Xe DW-MRI measurements were performed in 23 healthy volunteers who spanned an age range of 23–70 years. The relationship between the 129Xe DW-MRI and AiDA metrics was tested using Spearman’s rank correlation coefficient. Significant correlations were observed between AiDA distal airspace radius (rAiDA) and mean 129Xe apparent diffusion coefficient (ADC) (p < 0.005), distributed diffusivity coefficient (DDC) (p < 0.001) and distal airspace dimension (LmD) (p < 0.001). A mean bias of − 1.2 µm towards rAiDA was observed between 129Xe LmD and rAiDA, indicating that rAiDA is a measure of distal airspace dimension. The AiDA R0 intercept correlated with MRI 129Xe 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.

Highlights

Enlargements of distal airspaces can indicate pathological changes in the lung, but accessible and precise techniques able to measure these regions are lacking
Significant linear correlations were observed between radius of the lungs measured by AiDA (rAiDA) and 129Xe DW-magnetic resonance imaging (MRI) metrics apparent diffusion coefficient (ADC) (p < 0.005), distributed diffusivity coefficient (DDC) (p < 0.001) and LmD (p < 0.001) (Fig. 1a–c)
Bland–Altman analysis of rAiDA and 129Xe LmD showed a mean bias of − 1.2 μm (95% agreement limits − 36.0 to 33.6 μm) towards rAiDA (Fig. 2). rAiDA and LmD deviated less than 0.05% for the whole group and on average 8% between subjects

Summary

Introduction

Enlargements of distal airspaces can indicate pathological changes in the lung, but accessible and precise techniques able to measure these regions are lacking. The method is based on measurement of the Brownian diffusional restriction of the inhaled hyperpolarised gas atoms within the distal airspace walls This property is used to derive the apparent diffusion coefficient (ADC), which provides 3D in vivo information on the distal airspace microstructure. In addition to ADC, theoretical models of hyperpolarised gas diffusion within the lungs, such as the stretched exponential model (SEM)[6,7] and the cylinder airway model (CM)[8,9], can be used to derive distal airspace dimensions, analogous to those obtained through histological analysis These in vivo distal airspace measurements from hyperpolarised gas DW-MRI have shown good agreement with direct morphometric measurements in validation studies with lung specimens[8,10,11]. Further benchmarking of the technique with established methods of in vivo distal airspace assessment is required to evaluate the clinical potential of the AiDA technique

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