Longitudinal Assessment of Patients With Cystic Fibrosis Lung Disease With Multivolume Noncontrast MRI and Spirometry

Abstract

Background: MRI has been suggested as a radiation-free imaging modality to investigate early structural alterations and regional functional impairment in cystic fibrosis (CF) lung disease.

Purpose/hypothesis: To compare functional and morphological MRI changes over the course of the disease to changes in spirometry.

Study type: Longitudinal retrospective study.

Population: Twenty patients with CF lung disease (at baseline, age = 16.5 (13.3-20.6) years, forced expiratory volume in 1 second (as % of predicted [%pred]) FEV₁ = 71 (59-87) %pred, forced expiratory flow at 25-75% of forced vital capacity FEF_25-75 = 39 (25-63) %pred.

Field strength/sequence: 1.5T / T₂ -weighted HASTE; T₂ -weighted TSE-PROPELLER; T₂ -weighted bSSFP; T₁ -weighted 3D GRE.

Assessment: Nonenhanced chest MRI and spirometry were retrospectively collected over a 3-year period from the initial recruitment visit. Images acquired at end-inspiration and end-expiration were registered by software using the optical flow method to measure expiratory-inspiratory differences in MR signal-intensity (Δ¹ H-MRI). Measures of CF functional impairment were defined from Δ¹ H-MRI: Δ¹ H-MRI median, Δ¹ H-MRI quartile coefficient of variation (QCV), and percent low-signal-variation volume (LVV). MR images were also evaluated by three readers using a CF-specific scoring system.

Statistical tests: Spearman correlation analysis, Spearman rank correlation analysis, linear mixed-effect model analysis, intraclass correlation coefficient.

Results: Functional imaging parameters and total morphological score correlated with all spirometric measures, as did subscores of bronchial wall thickening/bronchiectasis, mucus plugging, and consolidation. Overall, the percent change of Δ1H-MRI median correlated with the percent change of FEV₁ (ΔFEV₁ , r = 0.41, P < 0.01) and the percent change of FEF_25-75 (ΔFEF25-75%, r = 0.38, P < 0.01). The percent change of LVV correlated with ΔFEV₁ (r = -0.47, P < 0.001) and ΔFEF_25-75 (r = -0.50, P < 0.001).

Data conclusion: These preliminary results suggest that nonenhanced multivolume MRI may provide a feasible tool to regionally map early pulmonary alterations for longitudinal evaluation of CF lung disease, without exposing the patients to ionizing radiation.

Level of evidence: 3T TECHNICAL EFFICACY STAGE: 5.

Keywords: cystic fibrosis; lung function; structure-function relationship.