Xenon gas MRI detects longer-term lung damage after COVID not picked up by routine CT scan

Reuters Health - 02/06/2021 - Hyperpolarized xenon-129 MRI (XeMRI) can detect lung abnormalities in patients with breathlessness following COVID-19 pneumonia that are not evident on routine tests, according to a preliminary report from researchers in the U.K.

In nine patients evaluated at three months or longer after hospital discharge for COVID-19, XeMRI showed alveolar-capillary diffusion limitation in all patients relative to healthy controls - despite normal or nearly normal chest CT scans and normal clinical measurements (D-dimer, hemoglobin and lung function tests), the researchers report in Radiology.

"The 129Xe MRI is pinpointing the parts of the lung where the physiology of oxygen uptake is impaired due to long standing effects of COVID-19 on the lungs, even though they often look normal on CT scans," study researcher Dr. Jim Wild of the University of Sheffield said in a news release.

"Many COVID-19 patients are still experiencing breathlessness several months after being discharged from hospital, despite their CT scans indicating that their lungs are functioning normally," Dr. Fergus Gleeson of the University of Oxford, who also worked on the study, said in the release.

"Our follow-up scans using hyperpolarized xenon MRI have found that abnormalities not normally visible on regular scans are indeed present, and these abnormalities are preventing oxygen getting into the bloodstream as it should in all parts of the lungs," added Dr. Gleeson.

"Although our small study did not recruit from long-COVID clinics, the results suggest that hyperpolarized Xenon MRI may be a potentially useful imaging modality in dyspneic patients with long-COVID, following hospital discharge at a mean of three months for COVID-19," the team writes in their paper.

"XeMRI appears to provide an explanation for patient symptoms not explained by other clinical data or imaging techniques, does not pose a radiation burden to the patient and can be completed in a single breath hold. XeMRI may also provide information on the extent to which gas exchange units in the lungs are affected, their duration and the time it takes for regeneration and recovery to occur," they add.

In an accompanying editorial, Dr. Olaf Dietrich of the University Hospital of the Ludwig Maximilian University of Munich, Germany, cautions that these are preliminary results of a prospective study in nine participants examined and scanned with XeMRI between three and eight months after hospital discharge for COVID-19 infection. None of them required invasive ventilation during hospitalization.

While the results are "promising with respect to assessment of patients with chronic post-COVID-19 symptoms," Dr. Dietrich says larger studies of XeMRI in better-defined patient subgroups are needed.

"Ideally, at least three sufficiently large groups should be compared using 129Xe MRI: healthy controls without a history of COVID-19, participants who fully recovered from COVID-19 without any persisting symptoms, and participants who still experience long COVID sequelae. The preliminary results . . . strongly suggest that such studies will substantially improve our knowledge about the causes and diagnosis of post-COVID-19 symptoms," Dr. Dietrich concludes.

Dr. Dietrich also noted that the cost of XeMRI is "considerable" and requires investment in dedicated equipment.

This work was supported by the National Consortium of Intelligent Medical Imaging.

SOURCE: https://bit.ly/3g31kiM Radiology, online May 25, 2021.

By Reuters Staff



Posted on 2 June 202122 June 2021