CASE 16884 Published on 14.07.2020

18-F FDG PET-CT appearances in COVID-19 patients: A Case Series

Section

Chest imaging

Case Type

Clinical Cases

Authors

Adeel Ejaz Syed, FRCR1; Alexander Zeinati, FRCR1; Roofia Tanvir, MBBS2; Erica Mulholland3, Nicola Mulholland, FRCR1; Marko Berovic, FRCR1

1. Department of Nuclear Medicine, Kings College Hospital, Denmark Hill, Brixton, London SE5 9RS

2. Department of Medicine, Maidstone Hospital, Hermitage Ln, Maidstone ME16 9QQ

3. Leicester Medical school, George Davies Centre, Lancaster Rd, Leicester LE1 7HA

Patient

59 years, female; 63 years, male; 83 years, female

Categories
Area of Interest Hybrid Imaging, Respiratory system ; Imaging Technique PET, PET-CT
Clinical History

We describe the 18-F FDG PET-CT appearances of COVID-19 in three outpatients.

Case 1: 59-year-old female with background lymphoma, presenting with shortness of breath

Case 2: 63-year-old male investigated for collapse

Case 3: 83-year-old female admitted with weight loss and raised C-Reactive Protein (CRP)

Imaging Findings

All three patients underwent an 18-Fluorine fluorodeoxyglucose positron emission tomography-computed tomography (18-F FDG PET-CT) study, with unenhanced free-breathing CT for attenuation correction.

In case 1, the PET-CT was performed 1 week after the patient’s acute presentation and revealed diffuse peripheral consolidation of basal predominance, which was intensely FDG-avid (SUVMax 7.6), no nodal enlargement and a complete metabolic response to lymphoma.

In case 2, the PET-CT was performed 2 weeks after the acute admission. Avid lymph nodes above and below the diaphragm in keeping with subsequently biopsy-proven lymphoma. In addition, moderate tracer uptake demonstrated in subpleural areas of ground-glass opacification (SUV max 3.7)

In case 3, the PET-CT was performed 5 weeks after acute admission to investigate possible vasculitis in a patient with eosinophilia and a splenic infarct. The scan demonstrated a photopaenic splenic infarct and non-FDG avid bilateral pleural effusions with no characteristic COVID-19 chest appearances.

Discussion

Background:

The coronavirus (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has a propensity for causing a potentially fatal pneumonia[1]. The infection fatality rate is estimated between 0.7% and 6.4%[2] with poorer outcomes identified for those with co-morbidities[3].

The use of imaging in diagnosis, particularly CT, has demonstrated increased sensitivity than RT-PCR testing[4]. The most common CT appearances of COVID-19 pneumonia are bilateral and subpleural areas of ground-glass opacification, lower lobe consolidation[5] and occasionally crazy-paving appearances[1]. However, these appearances are non-specific and encountered in other viral pneumonias such as influenza, SARS and MERS.

The emerging evidence is that microvascular thrombi are strongly associated with COVID-19 infection and contribute to the high D-dimer levels commonly seen in the typical blood changes. Correlating the CT findings with blood abnormalities of lymphopaenia, a raised CRP and raised D-dimer[6] is important in raising the possibility of COVID-19 infection.

Clinical perspective:

In case 1, the patient was admitted one week after the PET CT with shortness of breath. During the admission, she had a lymphopaenia of 0.8, a CRP of 187 and a D-dimer of 2892. Given the typical imaging and blood findings, she was treated clinically for COVID pneumonia despite a negative swab.

In case 2, PET CT was performed 3 days after the patient was discharged and 13 days after the positive swab. During admission, CRP was 174 and D-dimer was 1328.

In case 3, the PET CT was performed 34 days after the positive swab. At the time of the swab, the CRP was 286 and a lymphopaenia of 0.16.

Imaging perspective:

In both cases 1 and 2, the typical CT appearances of COVID-19 pneumonia are demonstrated with concomitant increased FDG-avidity. The addition of functional imaging allows us to interpret whether there is an active glycolytic process within ground glass lung infiltrates.

Patients with COVID-19 may be investigated for co-existent pathology as thromboembolic complications are being reported in multiple organs. In case 3, The PET was of value in excluding vasculitis or any residual COVID-19 related inflammation but it showed a splenic infarct, a possible late COVID-19 complication. 

Outcome:

All 3 patients in our series have been discharged home.

Take-home message:

During the pandemic and recovery phase, PET-CT imaging continues for non-COVID indications. It is important for the radiologist to recognise the variable whole body findings on metabolic imaging.

Differential Diagnosis List
COVID-19 pneumonia.
Viral pneumonia (influenza, MERS, SARS).
Atypical bacterial infection (mycoplasma).
Idiopathic organising pneumonia.
Chronic eosinophilic pneumonia.
Drug-induced injury.
Final Diagnosis
COVID-19 pneumonia.
Case information
URL: https://www.eurorad.org/case/16884
ISSN: 1563-4086