Subtle COVID-19 lung changes found through photon-counting CT scans

Photon-counting detector CT found more subtle lung abnormalities that may indicate irreversible lung fibrosis in symptomatic patients following COVID-19 infection than conventional CT, according to a study published in Radiology.

“Novel photon-counting detector technology has the potential to detect lung changes earlier and characterize them in greater detail, allowing for timely and personalized treatment allocation, more effective monitoring of treatment response and giving the opportunity to better understand how lung disease develops and progresses,” Florian Prayer, MD, PhD, of the department of biomedical imaging and image-guided therapy at the Medical University of Vienna, told Healio.

In a prospective study, Prayer and colleagues analyzed 20 adults (mean age, 54 years; 50% men) who had lasting COVID-19-related symptoms and two different CT scans taken in 1 day to determine if photon-counting detector (PCD) CT could detect more lung abnormalities than conventional energy-integrating detector (EID) CT in this patient population.

Researchers included participants that still had one or more symptoms related to COVID-19, such as resting or exertional dyspnea, cough and fatigue.

In order to evaluate the detectability of subtle lung abnormalities in the participants, researchers used a stepwise approach to first compare 1 mm EID CT and PCD CT images, then 0.4 mm and 1 mm PCD CT images, and lastly 0.2 mm and 0.4 mm PCD CT images .

Additionally, researchers analyzed image quality of both CT methods to see which performed better on the 5-point Likert scale — with scores ranging from –2, or definitely worse, to 2, or definitely better — and in terms of lung signal-to-noise ratios.

Of the total cohort, 15 participants (75%) had lung abnormalities detected by EID CT, with ground-glass opacities and linear bands, each in a total of 10 participants, being most common.

PCD CT detected additional lung abnormalities that were not captured by EID CT images in 10 participants, with bronchiolectasis detected most frequently in 10 participants, followed by reticulations in seven participants. Detecting 17 abnormalities in nine participants, 0.4 mm PCD CT images detected most of these additional findings.

“We were surprised to find subtle pathology of the smallest airways (bronchiolectasis) in a large proportion (half) of the study participants that was not seen using a current state-of-the-art CT scanner,” Prayer told Healio. “Interestingly, additional pathology was found only in cases where conventional CT scans showed other lung abnormalities.”

In a press release from the Radiological Society of North America, Benedikt Heidinger, MD, of the department of biomedical imaging and image-guided therapy at the Medical University of Vienna, said PCD CT scans may help patients with lasting COVID symptoms in more ways than better detection.

“PCD CT has potential in decreasing radiation dose and in artifact reduction, representing direct benefits to patients,” Heidinger said in the release.

In terms of subjective and objective image quality, 1 mm PCD CT images outperformed 1 mm EID CT with a Likert scale score of 1 (interquartile range [IQR], 1-2; P < .001) and based on lung signal-to-noise ratio (mean difference, 0.53 ± 0.96; P = .03), according to researchers.

Further, 0.4 mm PCD CT outperformed 1 mm PCD CT images (Likert scale score, 1; IQR, 1-1; P < .001), but researchers did not find a difference in subjective image quality between 0.4 mm and 0.2 mm PCD CT images.

Additionally, researchers observed lower lung signal-to-noise ratios when comparing 0.4 mm to 1 mm PCD CT images (–1.52 ± 0.68; P < .001) and 0.2 mm to 0.4 mm PCD CT images (–1.15 ± 0.43; P < .001).

“Future studies will determine the effect of the greater spatial resolution and spectral imaging applications made possible by photon-counting detectors in larger patient populations and in different (lung) diseases,” Prayer told Healio. “This will help to quantify the benefit of this technology for patients in terms of improved outcome and quality of life through earlier detection and classification of disease.”

For more information:

Florian Prayer, MD, PhD, can be reached at florian.prayer@meduniwien.ac.at.

Reference:

Photon-counting CT shows more post-COVID-19 lung damage. https://press.rsna.org/timssnet/media/pressreleases/14_pr_target.cfm?ID=2400. Published Nov. 29, 2022. Accessed Nov. 29, 2022.