Hyperpolarized Xenon MRI Scans Detect Abnormalities in Lungs of Long COVID Patients

The EXPLAIN study conducted by researchers at the University of Sheffield (Sheffield, UK) and University of Oxford (Oxford, UK) is using hyperpolarized xenon MRI scans to investigate possible lung damage in long COVID patients who experience breathlessness and were not hospitalized when they had COVID-19. These early results suggest that COVID-19 may result in persistent impairment in gas transfer and underlying lung abnormalities. However, the extent to which these abnormalities contribute to breathlessness is currently unclear.

Hyperpolarized xenon MRI requires the patient to lie in an MRI scanner and breathe in one litre of xenon gas that has had its atomic structure altered so it can be seen using MRI. Xenon is an inert gas that behaves in a very similar way to oxygen, so radiologists then can observe how the gas moves from the lungs into the bloodstream. A previous study using the same imaging method established that patients who had been hospitalized with COVID-19 had persistent lung abnormalities several months after they were discharged.

For this pilot study, the researchers recruited 36 patients who fell into three groups: People with long COVID who had normal CT scans; People who had been in hospital with COVID-19 and discharged more than three months previously, who had normal or nearly normal CT scans and who were not experiencing long COVID; and An age- and gender-matched control group who did not have long COVID symptoms nor had been hospitalized with COVID-19. In the initial results, the long COVID patients had abnormal hyperpolarized xenon MRI scans, indicating ‘significantly impaired gas transfer’ from the lungs to the bloodstream. However their CT scans showed normal results.

“We knew from our post-hospital COVID study that xenon could detect abnormalities when the CT scan and other lung function tests are normal,” said the study’s Chief Investigator, Fergus Gleeson, Professor of Radiology at the University of Oxford and Consultant Radiologist at Oxford University Hospitals NHS Foundation Trust. “What we’ve found now is that, even though their CT scans are normal, the xenon MRI scans have detected similar abnormalities in patients with long COVID. These patients have never been in hospital and did not have an acute severe illness when they had their COVID-19 infection. Some of them have been experiencing their symptoms for a year after contracting COVID-19.”

“Xenon MRI is uniquely placed to help understand why breathlessness persists in some patients post COVID,” said Professor Jim Wild and the Pulmonary, Lung and Respiratory Imaging Sheffield (POLARIS) research group at the University of Sheffield, who pioneered hyperpolarized xenon MRI. “Xenon follows the pathway of oxygen when it is taken up by the lungs and can tell us where the abnormality lies between the airways, gas exchange membranes and capillaries in the lungs.”

“These are interesting results and may indicate that the changes observed within the lungs of some patients with long COVID contribute to breathlessness. However, these are early findings and further work to understand the clinical significance is key,” said co-researcher Dr Emily Fraser, a Respiratory Consultant who leads the Oxford Post-COVID Assessment Clinic. “Extending this study to larger numbers of patients and looking at control groups who have recovered from COVID should help us to answer this question and further our understanding of the mechanisms that drive long COVID.”

Related Links:
University of Sheffield
University of Oxford