New model can detect long-COVIDs effects using simple, 2D chest X-rays

For patients dealing with lingering respiratory symptoms from the novel coronavirus, a chest X-ray can reveal only so much. The two-dimensional (2D) scans simply can’t distinguish compromised lung function. For that diagnosis, a more expensive, three-dimensional (3D) technique called a CT scan is necessary.

Yet many medical clinics in the United States don’t have CT scanning equipment, leaving so-called long-COVID patients with little information about their lung function.

That may change. In a new study, researchers at the University of Iowa have developed what is called a contrastive learning model. This model “learns” from composite 2D images constructed from 3D CT images to detect compromised lung function in long-COVID patients. Another technique, called transfer learning, then conveys lung diagnostic information from a CT scan to a chest X-ray, thus allowing chest X-ray equipment to detect abnormalities the same as if those patients had used a CT scan.

In the study, the researchers showed how their contrastive learning model could be applied to detect small airways disease, which is an early stage of compromised lung function in long-COVID patients. Of the long-COVID patients, the models were advanced enough to distinguish the severity of the compromised lung function, separating those with small airways disease from those with more advanced respiratory issues.

“The new element to the model is taking information from 3D CT scans showing lung volume and transferring that information to a model that will show these same characteristics in 2D images,” says Ching-Long Lin, Edward M. Mielnik and Samuel R. Harding professor and chair of the Department of Mechanical Engineering in the College of Engineering at Iowa. “Clinicians would be able to use chest X-rays to detect these outcomes. That’s the bigger perspective.”

The researchers based their modeling on CT scans of 100 people who were infected with the original COVID strain and went to UI Hospitals & Clinics for diagnosis for breathing problems between June and December 2020. Many of these long-COVID patients had small airways disease, a diagnosis reported by Alejandro Comellas, clinical professor of internal medicine-pulmonary, critical care, and occupational medicine, in a paper published last March in the journal Radiology.

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