Researchers at the annual RSNA meeting in Chicago have shown that photon-counting CT outperforms conventional CT in detecting subtle damage in the lungs of patients with persistent symptoms of COVID-19

Photon-counting CT, or photon-counting detector (PCD) CT, which has emerged in the last decade as a promising imaging tool, works by converting X-ray photons directly into an electrical signal. This avoids the intermediate step of conversion by means of a photodiode found in conventional CT scanners that use energy-integrating detectors. The result significantly reduces energy and signal loss at the detector site.

In September 2021, Siemens Healthineers received FDA approval for the NAEOTOM Alpha, the first photon-counting CT system cleared for the US market. Neurologica received FDA approval for its photon-counting CT system, the OmniTom Elite with PCD, in March 2022.
Previous studies have highlighted the advantages of photon-counting CT in other fields of radiology, such as cardiovascular and head-and-neck imaging, and now researchers are saying the technology could lead the way to earlier treatment and better outcomes for the growing number of people with COVID-related lung damage. They reached their conclusion by comparing photon-counting CT with conventional CT in 20 adults, mean age 54 years, who had one or more COVID-19-related persisting symptoms, such as cough and fatigue.

“In our study investigating lung abnormalities in symptomatic post-COVID patients, we were able to detect subtle lung abnormalities in 10 of 20 participants using PCD CT that were not seen in conventional CT,” said study senior author Dr. Benedikt Heidinger, from the department of biomedical imaging and image-guided therapy at the Medical University of Vienna in Austria. “Moreover, PCD CT has potential in decreasing radiation dose and in artifact reduction, representing direct benefits to patients.”

Photon-counting CT’s ability to detect these subtle lung abnormalities is especially important, Dr. Heidinger said, because patients with persistent symptoms following COVID-19 can develop irreversible lung damage known as lung fibrosis. Conventional CT is one of the primary methods for detecting and diagnosing lung fibrosis, but it can miss the subtle abnormalities indicative of early-stage fibrosis.

“Future trials including clinical outcomes such as quality of life, pulmonary function testing and histology will reveal the true benefit of this exciting new detector technology,” Dr. Heidinger said.

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