Quantitative<i>in vivo</i>assessment of lung microstructure at the alveolar level with hyperpolarized³He diffusion MRI

TLDR

Lung emphysema has been studied since the 17th century, yet quantitative localized characterization at the alveolar level remains elusive because traditional imaging and pulmonary function tests cannot provide this information. The study aims to report the first in vivo measurements of alveolar‑level lung geometry using 3He diffusion MRI in healthy subjects and severe emphysema patients. The authors use 3He diffusion MRI to measure alveolar‑level lung geometry and present a theory of anisotropic diffusion. Experimental data show highly anisotropic 3He diffusivity in the acinus, revealing marked differences between healthy and emphysematous lungs and suggesting the technique could aid early emphysema diagnosis.

Abstract

The study of lung emphysema dates back to the beginning of the 17th century. Nevertheless, a number of important questions remain unanswered because a quantitative localized characterization of emphysema requires knowledge of lung structure at the alveolar level in the intact living lung. This information is not available from traditional imaging modalities and pulmonary function tests. Herein, we report the first in vivo measurements of lung geometrical parameters at the alveolar level obtained with 3He diffusion MRI in healthy human subjects and patients with severe emphysema. We also provide the first experimental data demonstrating that 3He gas diffusivity in the acinus of human lung is highly anisotropic. A theory of anisotropic diffusion is presented. Our results clearly demonstrate substantial differences between healthy and emphysematous lung at the acinar level and may provide new insights into emphysema progression. The technique offers promise as a clinical tool for early diagnosis of emphysema.