BIOMEDICAL 14 THE SCIENTIST
OPINION One-to-one
Below. Scans of healthy lungs (left) and COVID patient lungs (right).
ALTERED IMAGES
Scanning technology has identified hidden abnormalities in the lungs of long COVID patients
E
arly on in the pandemic, Professor Fergus Gleeson, Consultant Radiologist at Oxford University Hospitals NHS Foundation Trust, had the idea to use a scanning method to understand changes in lung physiology due to COVID-19. The non-invasive method of hyperpolarised xenon MRI scans has been used for some years to develop understanding of lung physiology in health and disease, and was pioneered by Professor Jim Wild and the Pulmonary, Lung and Respiratory Imaging Sheffield (POLARIS) research group at the University of Sheffield. Both Gleeson and Wild are among the research team in the EXPLAIN project – one of 19 studies into long COVID to receive £1.8 million government funding through the National Institute for Health Research, which uses hyperpolarised xenon MRI scans to look at ongoing lung damage in non-hospitalised COVID-19 patients. The project aims to improve understanding of long COVID, from diagnosis and treatment
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through to rehabilitation and recovery. Evidence has emerged in the latest pilot study from EXPLAIN, of lung abnormality in long COVID patients undetected by other scans. Participants lie in an MRI scanner and inhale one litre of xenon, which has been hyperpolarised so it can be seen using MRI. It takes only a few minutes and, because radiation exposure is not needed, can be repeated over time to see changes to the lungs. As xenon follows the pathways of oxygen when it is taken up by the lungs and can show where the abnormality lies between the airways, gas exchange membranes and capillaries in the lungs, radiologists can observe how the gas moves from the lungs into the bloodstream. A 2021 EXPLAIN study that scanned people who had been hospitalised due to COVID-19 established that they had persistent lung abnormalities several months after being discharged. Now a new EXPLAIN pilot study has investigated possible lung damage in COVID-19 patients who have not
been hospitalised but have experienced breathlessness months after a diagnosis.
Hidden impairments “Initially, we thought that there wouldn’t be any significant changes in lung gas transport, in comparison to healthy non-infected individuals, but how wrong we were,” says Dr James Grist, postdoctoral research scientist at the University of Oxford, and one of the researchers in the EXPLAIN study. “We were very surprised to see xenon gas transfer abnormalities in patients whose lungs otherwise looked healthy on conventional imaging.” Transfer of gas from the lungs to the bloodstream was “significantly impaired” in those study participants who have been diagnosed with long COVID, seen in long COVID clinics and who have had normal computerised tomography scans. “The extent of the changes in gas transfer between healthy participants and those who have had a COVID-19 infection was really surprising,” Grist says. “When we got our images from
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