ABSTRACT
Background Photon-counting detector (PCD) CT allows ultra-high-resolution lung imaging and may shed light on morphologic correlates of persistent symptoms after COVID-19. Purpose To compare PCD CT with energy-integrating detector (EID) CT for noninvasive assessment of post-COVID-19 lung abnormalities. Materials and Methods For this prospective study, adult participants with one or more COVID-19-related persisting symptoms (resting or exertional dyspnea, cough, and fatigue) underwent same-day EID and PCD CT scans between April 2022 and June 2022. EID CT 1.0mm images and, subsequently, 1.0mm, 0.4mm, and 0.2mm PCD CT images were reviewed for the presence of lung abnormalities. Subjective and objective EID and PCD CT image quality was evaluated using a 5-point Likert scale (-2 to 2) and lung signal-to-noise ratios (SNR). Results Twenty participants (mean age, 54 years ±16 [SD], 10 men) were included. EID CT showed post-COVID-19 lung abnormalities in 15 of 20 (75%) participants with a median involvement of 10% of lung volume [IQR 0-45%], and 3.5 lobes [IQR 0-5]. Ground-glass opacities (GGO) and linear bands (both 10 of 20 participants, 50%) were the most frequent findings on EID CT. PCD CT revealed additional lung abnormalities in 10 of 20 (50%) participants, most commonly bronchiolectasis (10 of 20, 50%). Subjective image quality was improved for 1.0mm PCD vs. 1.0mm EID CT images (1 [IQR 1-2], P<.001) and 0.4mm vs. 1.0mm PCD CT images (1 [IQR 1-1], P<.001), but not for 0.4mm vs. 0.2mm PCD CT images (0 [IQR 0-0.5], P=.26). PCD CT delivered higher lung SNR vs. EID CT 1.0mm images (mean difference 0.53 ± 0.96, P=.03), but lower SNRs for 0.4mm vs. 1.0mm images, and 0.2mm vs. 0.4mm images, respectively (-1.52 ± 0.68, P<.001 and -1.15 ± 0.43, P<.001). Conclusion Photon-counting detector CT outperformed energy-integrating detector CT with regard to visualization of subtle post-COVID-19 lung abnormalities and image quality.
ABSTRACT
BACKGROUND: Following coronavirus disease 2019 (COVID-19), a proportion of patients report prolonged or worsening symptoms and impairments. These symptoms are increasingly referred to as "long COVID" syndrome. They may be associated with radiological changes on computed tomography (CT) and pulmonary function impairment. OBJECTIVES: To discuss the role of long-term assessment of COVID-19 patients to determine which patients may benefit from follow-up. MATERIALS AND METHODS: This article presents the current results of clinical, radiological, and pulmonary function follow-up tests after COVID-19 pneumonia. RESULTS: Chronic fatigue and dyspnea are the most common persistent symptoms after COVID-19. Patients also present impaired exercise capacity. On CT, ground-glass opacities and parenchymal bands are the most common residual changes after COVID-19 pneumonia, histologically corresponding to organizing pneumonia. A proportion of patients who had severe COVID-19 pneumonia may show fibrotic-like changes during follow-up. Patients with severe acute infection may present with a restrictive syndrome with lower diffusing capacity for carbon monoxide (DLCO) and total lung capacity (TLC) values. Overall, significant and continuous improvement in all symptoms as well as radiomorphological and functional changes were observed over time. CONCLUSIONS: Patients with persistent symptoms after COVID-19 should be evaluated and treated in specialized post-COVID-19 clinics in a multidisciplinary manner.