The Potential Roles of Nuclear Medicine in the Evaluation of Long Haulers From the COVID-19 Pandemic

Introduction: Although most studies on the symptomatology associated with the coronavirus disease 2019 (COVID-19) have been focused on the clinical presentations of hospitalized patients in acute settings, an increasing number of reports show a rise in “COVID-19 long haulers”—patients who continue to experience or develop persistent symptoms weeks or months after recovering from initial illness. Over 66-87% of COVID-19 patients reported at least one persistent symptom related to the disease, the most common of which includes: fatigue, cough, dyspnea, anosmia, headaches, arthralgia, and chest pain. These lingering symptoms affect those who experienced mild as well as moderate or severe COVID-19 both as inpatients and outpatients. The field of Nuclear Medicine offers non-invasive tests that has the potential to help monitor and evaluate COVID-19 long haulers.

Methods: We discuss the role of Nuclear Medicine in evaluating COVID-19 long-haulers by presenting the relevant techniques available in the field. We describe potential applications of these tests to provide both anatomic and functional evaluation with the potential to identify medical issues in the long-haulers.

Results: COVID-19 has been shown to be a disease that affects multiple organ systems in a variety of ways. Infection and inflammation due to COVID-19 can damage several organs, most notably the lungs, heart, and kidneys. In examining injuries in the lungs, the use of ¹⁸F-FDG PET not only highlights the ground-glass opacities and lung consolidations consistent with CT findings of COVID-19 patients, but also shows increased ¹⁸F-FDG uptake in specific infected areas such as the lymph nodes, allowing us to detect and accurately map the location of infection and inflammation. On the other hand, myocardial injury due to COVID-19 can be observed by myocardial perfusion scintigraphy. This is especially useful when assessing microcirculation and coronary flow reserve for risk stratification and therapeutic planning. Finally, due to the high incidence of acute kidney injuries and subsequent renal complications among COVID-19 patients, the use of renal scintigraphy with Tc-99m MAG-3 and DMSA may help identify renal injuries and scarring. Conclusion: Diagnostic procedures in Nuclear Medicine such as PET/CT and body scintigraphy has the potential to allow us to detect, monitor and evaluate COVID-19 disease complications and related organ damage in long-haulers. When utilized in conjunction to other imaging techniques, Nuclear Medicine can help provide additional anatomic and functional information to evaluate issues in COVID-19 long haulers.