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 Table of Contents     
LETTER TO THE EDITOR
Year : 2020  |  Volume : 35  |  Issue : 4  |  Page : 381-383  

Potential role of molecular imaging with 18F-fdg in diagnostic triage and follow-up of suspects with COVID-19 infection


1 Department of Nuclear Medicine and PET/CT, Kuwait Cancer Control Center, Ministry of Health, Shuwaikh, Kuwait; Department of Pharmacy, COMSATS University Islamabad, Lahore Campus, Lahore, Pakistan, Kuwait
2 Department of Pharmacy, COMSATS University Islamabad, Lahore Campus, Lahore, Pakistan
3 Pakistan Nuclear Regulatory Authority, Islamabad, Pakistan
4 Department of Bioinformatics, Hazara University, Dhodial, Mansehra, Khyber Pakhtunkhwa, Pakistan

Date of Submission20-Apr-2020
Date of Decision27-Apr-2020
Date of Acceptance01-May-2020
Date of Web Publication21-Oct-2020

Correspondence Address:
Dr. Rashid Rasheed
Department of Nuclear Medicine and PET/CT, Kuwait Cancer Control Center, Ministry of Health, Shuwaikh
Kuwait
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijnm.IJNM_76_20

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How to cite this article:
Rasheed R, Murtaza G, Rasheed S, Bashir Z. Potential role of molecular imaging with 18F-fdg in diagnostic triage and follow-up of suspects with COVID-19 infection. Indian J Nucl Med 2020;35:381-3

How to cite this URL:
Rasheed R, Murtaza G, Rasheed S, Bashir Z. Potential role of molecular imaging with 18F-fdg in diagnostic triage and follow-up of suspects with COVID-19 infection. Indian J Nucl Med [serial online] 2020 [cited 2020 Nov 30];35:381-3. Available from: https://www.ijnm.in/text.asp?2020/35/4/381/298754



Dear Editor,

Within 2 months after the WHO declared COVID-19 an epidemic, the number of confirmed cases has crossed three million worldwide, with an overall death toll of more than 0.2 million. Currently, RT-PCR is the standard of testing for COVID-19 suspects; however, recent published data show that RT-PCR can be true negative or false negative in the initial period despite positive computed tomographic (CT) findings, and on the other hand, it is reported to be positive even after 5–13 days or more after the discharge of patients after recovery. Similarly, the reported data showed that the new rapid immunology kits detecting serum IgM and IgG levels may also be negative in initial 5–7 days due to the absence or delay in immune response from the body. The disadvantage of the CT chest itself emerged as the fact that 50% of the patients lack CT findings in the initial incubation period and showed positive findings even after the clinical resolution of disease.[1] Guan et al. reported 1099 cases stating that no CT changes were found in the 17.9% of the nonsevere and even 2.9% of the severe cases. Therefore, in the light of above scenarios, where initial RT-PCR/CT are true negative, false negative, or there is suspicion of disseminated disease or multiorgan involvement, especially cardiac involvement, we suggest that the potential role of 18 F-FDGPET/CT needs further evaluation in COVID-19 pandemic.[2]


   18F-FDG: A radiopharmaceutical in Detecting Early Pneumonitis Top


Inflammatory cytokines and cells are an integral part of the immune system and are known to take up 18 F-FDG at the place of inflammation, allowing this agent to play an important role in the early diagnosis of inflammatory diseases. In acute lung injury, the rate of 18 F-FDG uptake reflects the state of inflammatory process activation, i.e., C-reactive protein, CD4, CD8, and interleukin-6, pointing to an acute inflammatory response. COVID-19 infection is believed to comprise initial infiltration of inflammatory cytokines into the lung, followed by delayed morphological changes that are apparent on high-resolution CT (HRCT) approximately 4–5 days' postinfection with a peak reported between 6 and 11 days, which gives 18 F-FDG the opportunity to detect/image early inflammation many days before anatomical changes of CT chest and help early triage/isolation of such patients.[3]


   Quantification of Inflammation and Prediction of Recovery Time Top


18 F-FDG PET/CT offers functional quantification of inflammation in terms of standardized uptake values (SUVs) and lesion glycolysis amid inflammation (LGAI), reflecting disease severity. This in turn can guide physicians in titration of medical therapy on case-to-case basis by categorizing them as mild, moderate, and severe. The recent data by Qin et al.[3] showed that 18 F-FDG PET scan can be used to monitor response to respiratory therapy and help determine a patient's recovery time by correlating with SUV. They showed that high 18 F-FDG uptake in COVID-19 pneumonia was related with longer recuperative times [Figure 1].
Figure 1: (a) MIP PET whole-body image demonstrating mutiorgan imaging in a single setting. (b-d) Coronal, sagittal, and axial (top to bottom) computed tomography, PET, and fused PET/computed tomographic images showing localization of 18F-FDG in ground glass opacities (GGOs) of COVID-19 pneumonia. (e-g) Axial images of multiple FDG-positive nodes in the mediastinum (Courtesy of Lan et al.)[3]

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   Response Evaluation and Detection of Recurrent/residual Disease Top


18 F-FDG PET/CT not only can differentiate inflammation from noninflammatory lesions on CT but can also detect inflammatory changes in the lung, earlier than the CT. As the cellular level metabolic changes occur first in pneumonitis followed by morphological CT changes, therefore the resolution of active inflammatory disease is seen earlier on 18F-FDG, than CT alone, which in turn can help in differentiate and follow residual lung inflammation, if any, post-discharge of COVID19 patient.. Demirev et al. showed that HRCT performed immediately following 18 F-FDG PET in the suspected case of pneumonia did not show any abnormalities in the lungs [Figure 2] until 3 days of onset of inflammation.[4]
Figure 2: Suggested schematic for the integration and evaluation of 18F-FDG PET/CT imaging in specific group of patients with negative RT-PCR/immunology. N.A.: Not available, NGS: Next-generation sequencing, PET/CT: 18F-FDG PET/CT

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In addition to early detection of COVID-19 pneumonia as discussed above,18 F-FDG PET/CT whole-body scan can concomitantly image multiorgan (involvement if any) in a single setting, which is not possible using a CT alone setting.


   Myocarditis Post-COVID-19 Infection Top


COVID-19 can effect cardiovascular system, effecting myocardium, pericardium, and vessels, and even preexisting ischemic conditions are worsened secondary to viral hypoxemia. Microvascular damage, myocyte damage, and changes in the fatty acid metabolism in viral myocarditis can be readily imaged with 18 F-FDG PET/CT at an early stage and if detected at early stage can save valuable lives.[5]

Regarding cost issues,18 F-FDG PET/CT is free in the entire gulf for their nationals, and for other regions, high cost of the imaging can be covered through research funding projects and grants wherever applicable.

In a nutshell, in the current COVID-19 pandemic,18 F-FDG PET/CT though high cost, if properly adjusted in protocol [Figure 2], can provide high sensitivity for early detection of pneumonitis, concomitant assessment of multiorgan involvement through whole-body imaging, quantification of inflammation using SUV/LGAI, follow-up of response to treatment, detecting residual disease, and recurrence, whereas CT scan is initially unremarkable and fails to detect subtle residual inflammation, and moreover, CT findings remains unchanged for a longer time period after recovery.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Lan L, Xu D, Ye G, Xia C, Wang S, Li Y, et al. Positive RT-PCR test results in patients recovered from COVID-19. JAMA 2020;323:1502-3.  Back to cited text no. 1
    
2.
Guan W, Ni Z, Hu Y, Liang W, Ou C, He J, et al. Clinical characteristics of coronavirus disease 2019 in China. New Engl. J. Med. 2020;382:1708-20. DOI: 10.1056/NEJMoa2002032.  Back to cited text no. 2
    
3.
Qin C, Liu F, Yen T, Lan X. 18F-FDG PET/CT Findings of COVID-19: A Series of Four Highly Suspected Cases. Eur J. Nucl. Med Mol. Imaging. 2020;47:1281-6. doi: 10.1007/s00259-020-04734-w. [Epub 2020 Feb 22].  Back to cited text no. 3
    
4.
Demirev AK, Kostadinova ID, Gabrovski IR. 18F-FDG PET/CT in patients with parenchymal changes attributed to radiation pneumonitis. Mol Imaging Radionucl Ther 2018;27:10712.  Back to cited text no. 4
    
5.
Guidance and Best Practices for Nuclear Cardiology Laboratories during the Coronavirus Disease 2019 (COVID-19) Pandemic: An Information Statement from ASNC and SNMMI. Available from: https://www.dicardiology.com/content/best-practices-nuclear-cardiology-laboratories-during-coronavirus-covid-19-pandemic. [Last accessed on 2020 Apr 02].  Back to cited text no. 5
    


    Figures

  [Figure 1], [Figure 2]



 

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