18F-FDG PET-CT incidental lung findings in asymptomatic COVID-19 patients: evidences from the Italian core of the first pandemic peak

Document Type : Original Article


1 Department of Radiology, Papa Giovanni XXIII Hospital, Bergamo, Italy

2 School of Medicine, University of Milano Bicocca, Milano, Italy

3 Department of Nuclear Medicine, Papa Giovanni XXIII Hospital, Bergamo, Italy


Objective(s): To illustrate incidental 18F-FDG PET-CT findings and related CT alterations of suspicious pulmonary interstitial involvement in asymptomatic oncologic patients during the first COVID-19 outbreak in the core of Italian peak.
Methods: We retrospectively evaluated the 18F-FDG PET-CT follow-up examinations performed during the first Italian COVID-19 outbreak (March 3rd-April 15th, 2020) in 10 asymptomatic oncologic patients with a highly suspicious interstitial pulmonary involvement on CT. Six cases were confirmed SARS-CoV-2 by molecular tests. The following parameters were assessed: 1) lung involvement on co-registration CT as extension (laterality, number of lobes), pattern (ground-glass opacities/GGO, consolidations, mixed) and stage (early, progressive, peak, and absorption); 2) the maximum standardized uptake value (SUVmax) of lung lesions on 18F-FDG PET.
Results: The involved lobes were 5 in 5 cases (3 confirmed SARS-CoV-2), 2-4 in 4 cases and 1 in 1 case. GGO were found in all patients; 3 cases also showed a combination of GGO and peripheral consolidations (mixed). Five cases were suggestive for an early stage of interstitial pneumonia, 4 for progressive and 1 for peak. All the lung lesions showed increased FDG uptake. In early stages SUVmax ranged from 1.5 to 11, in progressive from 3.3 to 6.8, in peak from 2.4 to 7.7. SUVmax ranged 1.5-11 in patients with only GGO and 2.8-7.7 in those with mixed pattern.
Conclusions: 18F-FDG PET-CT findings in suspected COVID-19 pulmonary involvement of asymptomatic oncologic patients showed an increase in FDG uptake of GGO and consolidations, but with a wide and apparently nonspecific range of SUVmax values.


  1. Nishiura H, Kobayashi T, Miyama T, Suzuki A, Jung SM, Hayashi K et al. Estimation of the asymptomatic ratio of novel coronavirus infections (COVID-19). Int J Infect Dis. 2020; 94:154-155.
  2. Inui S, Fujikawa A, Jitsu M, et al. Chest CT Findings in Cases from the Cruise Ship “Diamond Princess'' with Coronavirus Disease 2019 (COVID-19). Radiol Cardiothorac Imaging. 2020; 2(2): e200110.
  3. Kronbichler A, Kresse D, Yoon S, Lee KH, Effenberger M, Shin JI. Asymptomatic patients as a source of COVID-19 infections: A systematic review and meta-analysis. Int J Infect Dis. 2020; 98:180-186.
  4. Qin Ch, Liu F, Yen TC, Lan X. 18F-FDG PET/CT findings of COVID-19: a series of four highly suspected cases. Eur J Nucl Med Mol Imaging. 2020; 47(5):1281-1286.
  5. Annunziata S, Bolton R C D, Kamani ChH, Prior JO, Albano D, Bertagna F et al. Role of 2-[18F]FDG as a Radiopharmaceutical for PET/CT in Patients with COVID-19: A Systematic Review. Pharmaceuticals (Basel). 2020; 13(11):377.
  6. Setti L, Kirienko M, Dalto SC, Bonacina M, Bombardieri E. FDG-PET/CT findings highly suspicious for COVID-19 in an Italian case series of asymptomatic patients. Eur J Nucl Med Mol Imaging. 2020; 47(7):1649-1656.
  7. Lütje S, Marinova M, Kütting D, Attenberger U, Essler M, Bundschuh RA. Nuclear medicine in SARS-CoV-2 pandemia: 18F-FDG-PET/CT to visualize COVID-19.Nuklearmedizin. 2020; 59(03):276-80.
  8. Chuang HH, Emery DJ, Campbell RM, Lu Y. FDG PET/CT in diagnosing COVID-19 infection in a cancer patient with exposure history but minimal symptoms. Clin Nucl Med. 2020; 45(8):656-658.
  9. Kwee TC, Kwee RM. Chest CT in COVID-19: what the radiologist needs to know. RadioGraphics. 2020; 40(7):1848-65.
  10. Boellaard R, Delgado-Bolton R, Oyen WJ, Giammarile F, Tatsch K, Eschner W, et al. FDG PET/CT: EANM procedure guidelines for tumour imaging: version 2.0. European journal of nuclear medicine and molecular imaging. 2015; 42(2):328-54.
  11. Pan F, Ye T, Sun P, Gui S, Liang B, Li L, et al. Time course of lung changes at chest CT during recovery from coronavirus disease 2019 (COVID-19). Radiology. 2020; 295(3):715-21.
  12. Vafea MT, Atalla E, Kalligeros M, Mylona E, Shehadeh F, Mylonakis E. Chest CT findings in asymptomatic cases with COVID-19: a systematic review and meta-analysis. Clinical radiology. 2020; 75(11):876. E 33-. e39.
  13. Oran DP, Topol EJ. Prevalence of asymptomatic SARS-CoV-2 infection: a narrative review. Annals of internal medicine. 2020; 173(5):362-7.
  14. Al-Sadeq DW, Nasrallah GK. The incidence of the novel coronavirus SARS-CoV-2 among asymptomatic patients: a systematic review. International Journal of Infectious Diseases. 2020; 98:372-80.
  15. Varble N, Blain M, Kassin M, Xu S, Turkbey EB, Amalou A, et al. CT and clinical assessment in asymptomatic and pre-symptomatic patients with early SARS-CoV-2 in outbreak settings. European radiology. 2021; 31(5):3165-76.
  16. Albano D, Bertagna F, Alongi P, Baldari S, Baldoncini A, Bartolomei M, et al. Prevalence of interstitial pneumonia suggestive of COVID-19 at 18F-FDG PET/CT in oncological asymptomatic patients in a high prevalence country during pandemic period: a national multi-centric retrospective study. European Journal of Nuclear Medicine and Molecular Imaging. 2021; 48: 2871–2882.
  17. Yuki K, Fujiogi M, Koutsogiannaki S. COVID-19 pathophysiology: A review. Clinical immunology. 2020; 215:108427.
  18. Thornton A, Fraioli F, Wan S, Garthwaite HS, Ganeshan B, Shortman RI, et al. Evolution of 18F-FDG-PET/CT findings in patients following COVID-19 pneumonia: An Initial Investigation. Journal of Nuclear Medicine. 2021; 62:8.
  19. Parekh M, Donuru A, Balasubramanya R, Kapur S. Review of the chest CT differential diagnosis of ground-glass opacities in the COVID era. Radiology. 2020; 297(3):E289-E302.
  20. Migliore M, Fornito M, Palazzolo M, Criscione A, Gangemi M, Borrata F, et al. Ground glass opacities management in the lung cancer screening era. Annals of translational medicine. 2018; 6(5).
  21. Zhang Y, Fu F, Chen H. Management of ground-glass opacities in the lung cancer spectrum. The Annals of thoracic surgery. 2020; 110(6):1796-804.
  22. Zhuo Y, Shan F, Yang S, Zhan Y, Shi Y, Zhang Z. Advances in differential diagnosis of pulmonary ground glass opacity on high resolution computed tomography and histopathology. Radiology of Infectious Diseases. 2020; 7(1):7-11.