Medicina Nuclear en la pandemia por COVID-19

We are at the algid point of the COVID-19 pandemic. The health care system is burdened as never before and despite this, it is responding to the health care pressure thanks to the thankless and efficient work of thousands of health care professionals and basic service workers.

It is a complex time, with new problems for which there was no preparation. Information is constantly flowing, but it is often equivocal or contradictory. We can attempt to make a preliminary analysis to assess how this situation is affecting Nuclear Medicine and the current and imminent repercussions. There is little data. In PubMed there are barely a dozen articles on COVID-19 and Nuclear Medicine. In fact, most are editoriales, letters, recommendations and a couple of series with very few patients. The points of greatest interest, which are naturally open to debate, seem to be those referring to the protection of health care providers, the management of positive patients or those suspected of having COVID-19 and some clinical questions related to indications and findings of Nuclear Medicine studies.

1

PROTECTION AND ORGANIZATION OF DEPARTMENTS

Different Spanish and international professional societies, the Nuclear Security Council itself, and autonomic health care authorities have elaborated very useful documents for the protection of personnel and guidelines of action for the practice of explorations or treatments in SARS CoV-2-positive patients or those with high suspicion of infection. The SERAM guideline (https://seram.es/index.php/informacion-coronavirus) is a good reference since it can be adapted because of its similarity with the procedures of Nuclear Medicine. In addition, the associations of Técnico Superior de Imagen para el Diagnóstico (TSID), SAGRA and the Asociación Catalana de Técnicos en Imagen para el Diagnóstico (ACTEDI) have produced a very useful and practical guideline endorsed by Spanish Society of Nuclear Medicine and Molecular Imaging (SEMNIM) to define the procedures of protection and safe management of patients in Nuclear Medicine Departments.

From a strategic point of view, several countries have adopted measures of different intensity for actions in Nuclear Medicine Departments in order to manage the pandemic. The editorial published this month in JNucl Med¹ is interesting in that different specialists discuss the preventive measures of contagion and criteria adopted for the management of patients in their respective centers in Europe and the United States. Obviously it is of great help to know the opinions of professionals from the countries involved from the onset of the epidemic who have already accumulated short, albeit intense, experience. Thus, the reports from China ^2,3 and Singapore ⁴ give an idea of the rigor of the measures adopted in the Nuclear Medicine Departments to avoid contagion between patients and professionals. In some countries in the Far East a negative swab for SARS-CoV-2 or a radiological study showing no images suggestive of COVID-19 is required before performing any nuclear medicine procedure ². Western countries have opted for questionnaires to determine whether patients have symptoms before performing a study, but it should be pointed out that in the largest series published the rate of COVID-19 pulmonary patterns is of 9% (6 out of 65 patients) in asymptomatic patients ⁵.

In brief, how can we reasonaby carry out our daily practice?

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  Program only studies and treatments which are urgent or critical for the therapeutic management of the patients. In most Nuclear Medicine Departments this would mean a 50% reduction in activity.

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  Space out the appointment times so that patients do not coincide in waiting areas. Forbid the presence of accompanying persons in the area, and if possible, place the patients individually in the service boxes.

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  Divide the staff into independent teams to cover the shifts, without contact among them to minimize the risk of contagion among the professionals.

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  Give individual questionnaires to the patients to detect symptoms. Some countries systematically take the temperature or perform more sensitive tests. Cancel the study in patients with symptoms and refer them according to the protocol of each institution.

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  Apply the cleaning protocols established in each center of not only the equipment (after each patient) but also the work surfaces (several times a day).

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  Revise the chest CT images in the SPECT/CT and PET/CT studies before the patient leaves the department. If these are suggestive of COVID-19, refer the patient according to the protocol established in each institution/autonomous community.

2

Indications and contraindications

Although Nuclear Medicine does not have a front line role in the diagnosis and treatment of COVID-19 disease, several aspects may affect the health care activity of this specialty. The appearance of radiological patterns of pneumonitis or pulmonary condensation are increasingly more frequent in asymptomatic patients who undergo hybrid CT studies for other generally oncological diseases ^6–8. Beyond notification of the medical team managing the patient, and taking into account that it is foreseen that the prevalence of this disease will continue to be high, the question is whether all patients attended in a Nuclear Medicine Department should be managed as a person who is potentially positive for SARS-CoV-2. This requires very strict individual protection of not only administrative personnel but also health care professionals and a permanent policy of temporal and spatial separation of the patients, especially in waiting rooms ².

Therefore, in view of the elevated probability that in the next months many patients will present the capacity of transmitting SARS-CoV-2, the practice of tests that generate aerosols (pulmonary ventilation) or high respiratory flow (as in stress myocardial perfusion studies) should be considered. In Spanish hospitals and in recent literature ^1,4 explorations of pulmonary ventilation have been suspended. Stress myocardial perfusion studies should be considered as a maneuver of risk and pharmacological tests are recommended instead ^4,6.

The indications for pulmonary scintigraphy with respect to the study of perfusion have been maintained. However, in the case of pulmonary thromboembolism (PTE), angioCT is recommended, and in the case of contraindication, a planar perfusion study should be performed, or if possible, SPECT/CT to evaluate the concordance or disconcordance of the perfusion defects with the radiological pattern ^1,10. The group from New York, headed by Leonard M. Freeman, proposes a diagnostic algorithm on suspicion of PTE in patients with COVID-19. With this algorithm the first option is angioCT, and if necessary, echo-doppler of the lower limbs to confirm deep vein thrombosis. Perfusion study would only be indicated in situations of contraindication for pulmonary angioCT. While a normal perfusion study clearly has a very high negative predictive value, all the patterns with defects of any characteristics should be evaluated as indeterminate ¹⁰. This is evidently a reasonable option, but it is not evidence based due to the scarce experience available at this time and should be analyzed in the near future to establish the real value of perfusion studies to rule out PTE or to detect intrapulmonary vascular alterations related to infection by SARS-CoV-2. In any case, if a ventilation study is to be carried out, the protection of the personnel and conditioning and cleaning of the room should follow the protocols for procedures with airway manipulation (cap, N95 mask, impermeable gown, hermetic glasses and disposable gloves).

There is also a great scarcity of data with regard to the possible value of ¹⁸F-FDG PET/CT in the evaluation of COVID-19. A relationship between the intensity of FDG uptake and the severity of the disease has been described, but its potential prognostic value is not known ^9,11. In the first publications, some characteristics of FDG uptake in the chest have been of note, showing the expected diffuse bilateral uptake, coinciding with the ground glass pattern or confluent condensation, in addition to foci of intense uptake in an elevated proportion of cases as well as a consistent absence of lymph node, hilar or mediastinal hypermetabolism. Possible alterations of the metabolic pattern in the central nervous system, hepatic or renal involvements described in the most severe cases remains to be determined, but in the studies published, FDG uptake was not detected outside the pulmonary area ^5,9. Another aspect that should be considered is the possible need for the diagnosis of endocarditis in COVID-19 patients. Studies with emission of aerosols such as transesophageal ultrasonography should be avoided in these patients, and the use of FDG-PET can be considered as the first option on suspicion of bacterial endocarditis ⁶.

Finally, it should be taken into account that, as during any crisis, there are opportunities for reflection and for reviewing our reality. Extreme superspecialization is becoming increasingly necessary to respond to the demands of accurate personalized medicine. However, many of us have been called on to treat patients, attend relatives, give clinical courses, visit wards together with surgeons, dermatologists, and internal medicine physicians, among others. The situation of extreme necessity requires returning to the essence of medicine, diluting specialties, and now we are only physicians and nurses working side by side to save lives. The future is uncertain. We do not know what will happen in the next months or years. We do not know what possible pandemics or health care catastrophes might eventually lie in wait for humanity. What is certain is that medical advances require specialization to achieve the levels of excellence for the professional work which will be demanded of us in the medicine of the future. It is also true that the basic medical training that allows the development of clinical judgment and health care rationale oriented to place patients as the focus of our care should not disappear from our area of knowledge or continuous training, not only to face situations such as that currently taking place but also because it is essential for our work as nuclear medicine physicians.