VRT and MIP demonstrate hypermetabolic parenchymal foci, indicative of infectious or inflammatory process

Incidental findings of COVID-19 in PET/CT imaging

By Misty Long, ARRT R.T.(R)(N), Siemens Healthineers, Hoffman Estates, IL, USA, and Lady Sawoszczyk, BS, CNMT,
NewYork-Presbyterian Hospital / Weill Cornell Medical Center, New York, New York, USA
Data and images courtesy of NewYork-Presbyterian Hospital / Weill Cornell Medical Center, New York, New York, USA

|2021-04-12
A 75-year-old male with diffuse large B-cell lymphoma (DLBCL)—6 months post-therapy following 3 cycles of a chemotherapy regimen—underwent PET/CT imaging to assess residual disease for subsequent treatment strategy.

Approximately 1 hour following the intravenous (IV) injection, a single-scan, whole-body acquisition was conducted on a Biograph mCT FlowTM scanner.
As observed in Figures 1 and 2, the PET/CT of the lungs shows bilateral, hypermetabolic ground-glass opacities (GGOs) on CT that correlate to PET tracer uptake.

In consideration of the ongoing COVID-19 pandemic, these incidental findings were deemed suspicious and the patient was referred for COVID-19 testing.

Test results confirmed the patient was positive for COVID-19.


PET/CT imaging is not indicated for the diagnosis of COVID-19. Only in-vitro diagnostic testing is currently the definitive method to diagnose COVID-19.
In January 2020, the World Health Organization (WHO) declared an international state of emergency in response to the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)—commonly known as COVID-19.1

COVID-19 is an infectious disease that primarily affects the lower respiratory tract and can remain asymptomatic or cause several flu-like symptoms. The spread of this disease predominantly occurs through the viral transmission of respiratory droplets when in close physical contact with another person. In severe cases, COVID-19 may cause interstitial pneumonia, which can evolve into acute respiratory distress syndrome, and subsequently, death.

Chest imaging remains an integral component of the work-up and staging of COVID-19, especially when assessing the patient for complications or disease progression. In April 2020, The Fleischner Society released a multinational consensus statement about the role of chest CT in patient management during the COVID-19 pandemic where they assess that imaging is indicated in patients highly suspected of COVID-19 with moderate-to-severe clinical features and a high pre-test probability of disease, as well as in patients with COVID-19 with a worsening respiratory status.3

The appearance of COVID-19 on a chest CT has been commonly observed in bilateral lungs as GGOs that are defined as hazy opacities with preservation of the underlying vascular and bronchial architecture and bronchovascular thickening.

In early phases, single or multiple GGOs or nodules may appear. The International Atomic Energy Agency (IAEA) issued guidance on chest CT and protocol dose optimization. Protocols with faster scanning should be preferred due to the high potential of motion artifacts from patients that are coughing and experiencing shortness of breath. The evaluation of most patients with COVID-19 infection consists of automatic or fixed kV less than or equal to 100, high pitch, fast rotation speed, lung kernel, and 2-3 mm for soft-tissue evaluation.5

Although PET/CT is not currently indicated for the evaluation of COVID-19, according to Fields et al, numerous reports have noted incidental localization of radiotracer in parenchymal lesions. These findings are consistent with data from Middle East Respiratory Syndrome-CoV cohorts, which suggest an ability to detect incidental localizations in subjects without clinical signs of disease.4

The value of PET/CT during the COVID-19 pandemic is within the scope of incidental detection of asymptomatic patients, which includes the incidental detection of sub-clinical disease burden that may play a role in curbing asymptomatic viral spread.4


According to Fields et al, the utilization of PET/CT in the “early detection of SARS-CoV-2 infection in patients who receive nuclear medicine imaging for unrelated clinical indications, such as the evaluation and staging of malignancy, is essential for providing prompt anticipatory care to vulnerable populations at high risk for rapid clinical decompensation.”4 Additionally, Kalra et al indicates ”PET/CT may be valuable for the overall assessment of COVID-19, as with disease progression, damage can occur to the kidneys and other organs, such as the heart, gastrointestinal tract, kidneys, and bone marrow.”6

Early diagnosis of COVID-19 pneumonia is not only crucial for appropriate patient management but also to help ensure essential post-exposure precautions are implemented for department and hospital staff as well as others who have been in contact with the patient.

Due to the complexity of COVID-19, PET/CT should be considered for its utility of differential diagnosis within incidental findings. Specifically, this case demonstrates how incidental findings in PET/CT imaging identified corresponding hypermetabolic parenchymal foci in the lungs, which led to further testing, and ultimately, identification of a positive COVID-19 diagnosis.

Scanner: Biograph mCT Flow 64
Imaging software: syngo®.via

PET

 

CT

Injected dose

11.2 mCi (414 MBq)

Tube voltage

100 kV

Post-injection delay

60 min

Tube current

63 mAs

Acquisition

1.0 mm/s
200 x 200 matrix

Slice collimation

3.0 mm

Slice thickness

3.0 mm

1

2

3

4

5

6