Characterization of Pulmonary Functional Abnormalities in Systemic Sclerosis Using Xenon MRI

BACKGROUND: Xenon MRI is increasingly used to evaluate patients with interstitial lung disease (ILD) and pulmonary hypertension (PH), both of which are common manifestations of systemic sclerosis (SSc). As such, Xe-MRI may be suited to interrogate lung function impairment in SSc. PURPOSE: To characterize xenon MRI signatures in SSc, toward evaluating the utility of xenon MRI as a method to elucidate mechanisms of regional lung function impairment in this population. STUDY TYPE: Prospective. POPULATION: Of 25 participants initially imaged, 21 participants (18 females) with SSc were included. Sixteen healthy volunteers (13 females) were enrolled. FIELDSTRENGTH/SEQUENCE: 3 T, 1-point Dixon imaging using xenon MRI. ASSESSMENT: Xenon MRI measures including ventilation defect percent, membrane uptake, red blood cell (RBC) transfer, RBC defect percent, and RBC oscillation amplitude were generated. Measures were compared across healthy and SSc groups and correlated with standard clinical measures, including demographics, pulmonary function tests, CT lung density measures, and pulmonary artery pressure. STATISTICAL TESTS: Due to a small number of male participants, statistical analysis was limited to female participants. Wilcoxon, t-tests, or Fisher's exact tests were used to compare between healthy and SSc groups. Pearson's correlation was used to correlate xenon MRI with clinical measures. p < 0.05 was considered significant. RESULTS: Despite a relatively mild burden of pulmonary disease, SSc participants exhibited significantly lower RBC/Membrane ratio (0.25 IQR, 0.10 vs. 0.34 0.05) and RBC transfer (0.22 ± 0.07 vs. 0.28 ± 0.07), and significantly greater RBC defect percent (22.8 IQR, 16.9 vs. 11.9 13.7) compared to healthy volunteers. DATA CONCLUSION: Xenon MRI measures, including RBC transfer, RBC/Membrane, and RBC defect percent were markedly different in female SSc patients compared to age-matched healthy volunteers, suggesting that xenon MRI may be an effective method for examining regional impairments to pulmonary gas exchange in SSc. EVIDENCE LEVEL: 2. TECHNICAL EFFICACY: Stage 2.