COVID-19: Findings in nuclear medicine from head to toe

Abstract

COVID-19 is a multisystemic disease, and hence its potential manifestations on nuclear medicine imaging can extend beyond the lung. Therefore, it is important for the nuclear medicine physician to recognize these manifestations in the clinic. While FDG-PET/CT is not indicated routinely in COVID-19 evaluation, its unique capability to provide a functional and anatomical assessment of the entire body means that it can be a powerful tool to monitor acute, subacute, and long-term effects of COVID-19. Single-photon scintigraphy is routinely used to assess conditions such as pulmonary embolism, cardiac ischemia, and thyroiditis, and COVID-19 may present in these studies. The most common nuclear imaging finding of COVID-19 vaccination to date is hypermetabolic axillary lymphadenopathy. This may pose important diagnostic and management dilemmas in oncologic patients, particularly those with malignancies where the axilla constitutes a lymphatic drainage area. This article aims to summarize the relevant literature published since the beginning of the pandemic on the intersection between COVID-19 and nuclear medicine.

Keywords: COVID-19; Nuclear medicine; PET-CT; SARS-CoV-2; Vaccination.

Fig. 1

Frontal cortical hypometabolism. 73-year-old male complaining of cognitive impairment after being hospitalized with severe COVID-19 pneumonia in the preceding year. Axial FDG-PET image demonstrated hypometabolism in the left greater than right frontal lobes (arrows).

Fig. 2

Subacute thyroiditis. Thyroid scan in a 52-year-old male demonstrating diffusely low technetium-99 m pertechnetate uptake in the thyroid gland 2 months after COVID-19 infection. This patient had new suppression of TSH. The imaging and laboratory findings suggested subacute thyroiditis.

Fig. 3

Tonsillitis and COVID-19 pneumonia. FDG-PET/CT axial fused images of a 61-year-old male with history of esophageal cancer and COVID-19. There is intense FDG uptake in the palatine tonsils (arrowheads). There were also FDG-avid subpleural ground glass opacities (arrows).

Fig. 4

Sinusitis in patient with COVID-19. Interim FDG-PET/CT in this 79-year-old male with diffuse large B-cell lymphoma and COVID-19 pneumonia demonstrated new FDG-avid mucosal thickening and secretions in the maxillary sinuses.

Fig. 5

COVID-19 pneumonia on PSMA-PET. MIP (left), axial fused (top right) and CT lung reconstruction (bottom right) images of F18-piflufolastat-PET/CT in a 76-year-old male with metastatic prostate cancer and COVID-19 pneumonia. There were extensive tracer-avid subpleural consolidative opacities in both lungs (arrows). PSMA-avid abdominal lymph nodes represented metastatic prostate cancer.

Fig. 6

Radiation recall pneumonitis following COVID-19 vaccination. A) Axial fused PET/CT image in a 67-year-old male with lung adenocarcinoma 4 days after receiving the 2nd dose of the mRNA-1273 vaccine demonstrates FDG-avid right subpectoral lymph nodes (arrowheads), FDG uptake in the right deltoid muscle (not shown) and FDG-avid consolidative opacities in the right upper and paramediastinal left upper lobes (arrows). B) FDG-PET/CT 2 months before when these findings were not present. C) Treatment plan of intensity modulated radiation therapy (IMRT) completed 19 months before presentation.

Fig. 7

Pulmonary embolism and COVID-19 pneumonia. FDG-PET/CT of a 64-year-old male with marginal zone lymphoma demonstrated FDG-avid subpleural consolidative and ground glass opacities (arrowheads, left image), as well as FDG uptake in the right lower lobar artery (arrow, left image), with corresponding filling defect noted on contrast-enhanced CT 4 days before (arrow, right image), consistent with acute pulmonary embolism, which also involved additional pulmonary arterial branches bilaterally.

Fig. 8

COVID-19 and pulmonary embolism. 72-year-old female who presented to the ED with shortness of breath and tested positive for SARS-CoV-2. Chest radiograph confirmed multifocal airspace opacification predominantly involving the peripheral right lung and lower left lung. Due to an extremely elevated D-dimer (>20 μg/mL) and renal insufficiency, a V/Q scan was ordered. Given that the patient had COVID-19, only perfusion imaging was obtained. Anterior and LAO projections demonstrated a wedge-shaped perfusion defect in the left midlung (black arrows), corresponding to an area which was relatively spared of opacification in the radiograph when compared to the rest of the lung parenchyma.

Fig. 9

Hypermetabolic lymphadenopathy following COVID vaccination. A) MIP and axial fused images of a 73-year-old female with lung adenocarcinoma demonstrating ¹⁸F-FDG-avid left axillary lymphadenopathy 3 days after receiving the second mRNA-1273 vaccine dose on the left arm. B) MIP and axial fused images of a 57-year-old female with well-differentiated appendiceal neuroendocrine tumor and ⁶⁸Ga-DOTATATE-avid right axillary lymphadenopathy 7 days after receiving the second BNT162b2 mRNA vaccine dose on the right arm. C) MIP and axial fused images of a 63-year-old male with recently diagnosed prostate cancer presenting with ¹⁸F-fluciclovine-avid right axillary lymphadenopathy 3 days after receiving the third dose of mRNA-1273 vaccine on the right arm.

Fig. 10

Deltoid uptake in following COVID-19 vaccination. FDG-PET/CT axial fused and sagittal MIP images of a 49-year-old female with history of metastatic breast cancer demonstrating characteristic elongated uptake in the left deltoid muscle 2 days after administration of the third mRNA-1273 vaccine dose (arrows).

Fig. 11

Panniculitis in patient with COVID-19. Fused axial FDG-PET/CT images in a 68-year-old male with melanoma and COVID-19 pneumonia who developed FDG-avid lung consolidative opacities (arrow), as well as multifocal areas of intense FDG uptake in the subcutaneous tissues of the torso (arrowheads), correlating with areas of fat stranding on CT, in keeping with panniculitis.