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.

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%), PRMEmphy% and PRMfSAD% 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 PRMEmphy% (r = 0.44), LAA% (r = 0.38), and PRMfSAD% (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: Chinese Clinical Trial Registry (http://www.chictr.org.cn), Registration number: ChiCTR2400094100.