Sir,
The coronavirus disease-2019 (COVID-19) pandemic is spreading at an inexorable pace and infecting more and more people worldwide. Many infected individuals are asymptomatic, at least in the initial stages. A recent study has shown that 50%–75% of individuals infected with COVID-19 were asymptomatic.[1] Although nuclear medicine imaging is unlikely to be part of the armamentarium for initial diagnosis, there have been cases described in the recent past of incidental detection of COVID-19 in asymptomatic cases undergoing scans for other indications. In all probability, this occurrence is bound to increase in frequency. While nuclear medicine services need to stringently follow the standard guidelines mandatory for healthcare personnel, it is equally important to be conversant with the imaging hallmarks, atypical features, and pattern of evolution of changes induced by the disease.
The respiratory system is the site of primary involvement. All pulmonary lesions reported in the literature were FDG avid.[23456] The first report on FDG positron emission tomography (PET)/computed tomography (CT) findings came from Wuhan at a time when the COVID-19 outbreak was still unrecognized.[2] The four patients described in this report had FDG avid peripheral ground-glass opacities (GGOs) and/or consolidations in the multiple pulmonary lobes, along with FDG avid mediastinal, hilar, or subclavian lymphadenopathy. They had typical clinical symptomatology of COVID-19, and the diagnosis was made on retrospective review of the clinical, laboratory, and imaging data.
FDG avid pulmonary lesions have been incidentally detected in asymptomatic cases as well. In fact, a recent report from another high prevalence region describes similar findings on a group of six patients who underwent PET/CT for various malignancies.[3] They were asymptomatic not only at the time of imaging but also for a period of at least 2 weeks before the study and were carefully screened by a triage before entering the scanning unit. Nevertheless, the patients had FDG-positive GGOs and consolidation in both the lungs; most pronounced in the inferior lobes. The study also describes incidental detection of GGOs in a patient who underwent 131 I-single-photon emission computed tomography/CT – the lesions predictably did not demonstrate radioiodine uptake. The patients went on to develop respiratory symptoms and tested positive for COVID-19. Similar findings were subsequently published by another group on a series of five patients.[4]
The classic CT appearance of COVID-19 lesions is now well described in the literature. Initial stages show the presence of multilobar GGOs, predominantly in the periphery of the lung, mainly in the lower lobes. With time, the lesions increase in size and number and spread to the center. Disease progression is marked by consolidation, septal thickening, crazy paving, CT halo sign, lymphadenopathy, pleural effusion, and pneumothorax.[78]
An unusual presentation of COVID-19 is the development of acute necrotizing encephalopathy (ANE): a rare complication of influenza and other viral infections. COVID-related ANE has presented as areas of symmetric hypoattenuation within medial thalami on CT and as hemorrhagic rim enhancing lesions within bilateral thalami, medial temporal lobes, and subinsular regions on magnetic resonance imaging (MRI).[9] Although PET/CT findings have not yet been described, the disease per se arises due to intracranial cytokine storms, and hence, in all probability, it is likely to be FDG avid depending on the disease stage at the time of scanning. Cardiac involvement presenting as myocarditis and myopericarditis is also a well-recognized complication, which has been described on MRI as increased wall thickness with biventricular hypokinesia, interstitial edema, and left ventricular dysfunction with circumferential pericardial effusion.[10] Nuclear medicine scan findings of cardiac involvement in COVID are yet to be published.
A thorough preparedness to meet the challenges of handling a COVID patient (known or incidentally diagnosed) is imperative for every nuclear medicine facility.[11] Designation of an isolation room with negative air pressure is necessary. Use of standard (Personal protective equipment) PPE (with proper donning and doffing) for personnel and mask and gown for the patient is mandatory. Disinfection of scanner (as per the manufacturer's recommendations) and deep disinfection of scanner room are essential. The names of all personnel dealing with the patient should be recorded for contact tracing (if required). The principles of “time, distance, and shielding” in the appropriate context should be followed at all times.[11]
Sooner or later, COVID cases are bound to find their way into nuclear medicine imaging departments. Knowledge of the imaging spectrum and the standard operating procedures would enable a prompt and effective management of patients and personnel.
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Conflicts of interest
There are no conflicts of interest.
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