Longitudinal lung function assessment of patients hospitalised with COVID-19 using 1 H and 129 Xe lung MRI.

BACKGROUND: Microvascular abnormalities and impaired gas transfer have been observed in patients with COVID-19. The progression of pulmonary changes in these patients remains unclear.

RESEARCH QUESTION: Do patients hospitalised due to COVID-19 without evidence of architectural distortion on structural imaging show longitudinal improvements in lung function measured using 1 H and 129 Xe magnetic resonance imaging between 6-52 weeks after hospitalisation?

STUDY DESIGN AND METHODS: Patients who were hospitalised due to COVID-19 pneumonia underwent a pulmonary 1 H and 129 Xe MRI protocol at 6, 12, 25 and 51 weeks after hospital admission in a prospective cohort study between 11/2020 and 02/2022. Imaging protocol: 1 H ultra-short echo time, contrast enhanced lung perfusion, 129 Xe ventilation, 129 Xe diffusion weighted and 129 Xe spectroscopic imaging of gas exchange.

RESULTS: 9 patients were recruited (57±14 [median±interquartile range] years, 6/9 male). Patients underwent MRI at 6 (N=9), 12 (N=9), 25 (N=6) and 51 (N=8) weeks after hospital admission. Patients with signs of interstitial lung damage were excluded. At 6 weeks, patients demonstrated impaired 129 Xe gas transfer (red blood cell to membrane fraction) but lung microstructure was not increased (apparent diffusion coefficient and mean acinar airway dimensions). Minor ventilation abnormalities present in four patients were largely resolved in the 6-25 week period. At 12 weeks, all patients with lung perfusion data (N=6) showed an increase in both pulmonary blood volume and flow when compared to 6 weeks, though this was not statistically significant. At 12 weeks, significant improvements in 129 Xe gas transfer were observed compared to 6-week examinations, however 129 Xe gas transfer remained abnormally low at weeks 12, 25 and 51.

INTERPRETATION: 129 Xe gas transfer was impaired up to one year after hospitalisation in patients who were hospitalised due to COVID-19 pneumonia, without evidence of architectural distortion on structural imaging, whereas lung ventilation wa normal at 52 weeks.