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September 10, 2025

Quantification of Lung Ventilation Using Four‐Dimensional Dynamic Ultrashort Echo Time MRI for Differentiating Preserved Ratio Impaired Spirometry From Non‐Chronic Obstructive Pulmonary Disease Subjects

Key Points

Ventilation defect percentage (VDP) in smokers with normal spirometry showed no significant differences compared to COPD or PRISm.
VDP mildly correlated with parametric response map metrics including PRM Emphy % and LAA %.
Prospective, cross-sectional assessment included 90 subjects across three groups using four-dimensional dynamic UTE MRI.
Quantifying ventilation defects with 4D UTE MRI may support early identification of PRISm in at-risk individuals.

Abstract

ABSTRACT Background Radiation‐free four‐dimensional (4D) dynamic ultrashort echo time MRI (UTE MRI) enables quantification of ventilation defects in chronic obstructive pulmonary disease (COPD) and preserved ratio impaired spirometry (PRISm) populations. Purpose To quantify pulmonary ventilation using 4D UTE MRI in PRISm and COPD populations, and determine its ability to distinguish PRISm from non‐COPD subjects. Study Type Prospective, cross‐sectional. Subjects 90 subjects (25 COPD, 31 PRISm, and 34 with normal spirometry). Field Strength/Sequence Four‐dimensional dynamic UTE MRI at 3 T. Assessment All subjects underwent pulmonary function tests, paired inspiratory and expiratory chest CT, and 4D UTE MRI. Parametric response maps (PRM) were generated and voxels were classified as normal, emphysema, or functional small airway disease (fSAD). The percentage of low attenuation area (LAA%), PRM Emphy % and PRM fSAD % were determined. Ventilation defect maps were generated to derive ventilation defect percentage (VDP). Statistical Tests Kruskal‐Wallis test with Dunn‐Bonferroni post hoc correction was used. Agreement was assessed using Bland–Altman plots (95% limits of agreement LoA). Correlations were analyzed by Spearman's rank correlation coefficient ( r ). Significant predictors were identified through binary logistic regression. The significance threshold was set at p < 0.05. Results VDP in smokers with normal spirometry showed no significant differences compared to VDP in GOLD 1–2 COPD ( p = 0.98) or PRISm ( p = 1). VDP mildly correlated with PRM Emphy % ( r = 0.44), LAA% ( r = 0.38), and PRM fSAD % ( r = 0.25). VDP (odds ratio = 1.27, 95% confidence interval: 1.04–1.65) was a significant predictor for PRISm. The inter‐modality agreement demonstrated minimal systematic bias with mean differences of 0 (95% LoA: −2.41 to 2.41) for observer 1 and 0 (95% LoA: −2.45 to 2.45) for observer 2. Data Conclusion Free‐breathing 4D UTE MRI objectively quantifies total ventilation defects and may serve as a potential imaging tool for identifying early abnormalities in subjects at risk of PRISm. Evidence Level 1. Technical Efficacy Stage 2. Trial Registration: ClinicalTrial.gov identifier: NCT02100800

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