Feasibility of longitudinal in vivo monitoring of pulmonary disease progression in mouse models using laboratory-based x-ray dark-field CT.

OBJECTIVE: Early alterations in pulmonary microstructure are central to the onset and progression of chronic obstructive pulmonary disease (COPD) and acute lung injury, yet these changes remain undetectable with conventional attenuation-based computed tomography (CT). Dark-field computed tomography is sensitive to small-angle x-ray scattering generated by intact alveolar structures; however, all prior in vivo studies have been cross-sectional and pseudo-longitudinal, precluding direct observation of disease evolution within the same subject. A longitudinal, microstructure-resolved imaging approach is needed to capture true disease trajectories, reduce inter-subject variability, and support preclinical therapeutic development. MATERIALS AND METHODS: We developed a dedicated dark-field CT imaging system and integrated workflow, including dose-optimized acquisition, a mouse-specific fixation device, motion compensation, pseudo-dark-field suppression, and deep learning-based three-dimensional lung segmentation, to support repeated imaging over 12 weeks in healthy, inflammatory-injury, and COPD mouse models. RESULTS: The dark-field coefficient (µd) showed distinct, model-specific temporal trajectories and appeared to reflect microstructural changes when attenuation (μ) remained stable. It exhibited pronounced left-right heterogeneity in the inflammatory-injury model and markedly different trajectories between two COPD mice under an identical protocol, underscoring inter-subject variability that the within-subject design captured. Overall, µd changed earlier than μ, and findings were consistent with terminal histology. CONCLUSION: Our results suggest the feasibility of long-term in vivo dark-field CT in preclinical lung studies. The dark-field coefficient shows promise as a potential noninvasive biomarker for early pulmonary damage, quantitative disease assessment, and therapy monitoring, supporting further investigation of longitudinal dark-field imaging in lung pathology and drug development. KEY POINTS: Question First laboratory-based longitudinal in vivo dark-field CT in mouse lung disease models over 12 weeks. Findings Dark-field signal showed more pronounced temporal variation than attenuation signal, with distinct model-specific trajectories. Relevance statement These findings establish a methodological foundation for longitudinal preclinical imaging of lung microstructure, which may support future translational research and the development of time-resolved imaging strategies for pulmonary disease.