Lung Scintigraphy for Pulmonary Embolism Diagnosis in COVID-19 Patients: A Multicenter Study

Abstract

In patients with novel coronavirus disease 2019 (COVID-19) referred for lung scintigraphy because of suspected pulmonary embolism (PE), there has been an ongoing debate within the nuclear medicine community as to whether and when the ventilation imaging should be performed. Indeed, whereas PE diagnosis typically relies on the recognition of ventilation-perfusion (V/P) mismatched defects, the ventilation procedure potentially increases the risk of contamination to health-care workers. The primary aim of this study was to assess the role of ventilation imaging when lung scintigraphy is performed because of suspected PE in COVID-19 patients. The secondary aim was to describe practices and imaging findings in this specific population. Methods: A national registry was created in collaboration with the French Society of Nuclear Medicine to collect lung scans performed on COVID-19 patients for suspected PE. The practices of departments were assessed regarding imaging protocols and aerosol precautions. A retrospective review of V/P SPECT/CT scans was then conducted. Two physicians masked to clinical information reviewed each case by sequentially viewing perfusion SPECT, perfusion SPECT/CT, and V/P SPECT/CT images. The scans were classified into 1 of the 4 following categories: patients for whom PE could reasonably be excluded on the basis of perfusion SPECT only, perfusion SPECT/CT, or V/P SPECT/CT and patients with mismatched defects suggestive of PE according to the European Association of Nuclear Medicine criteria. Results: Data from 12 French nuclear medicine departments were collected. Lung scans were performed between March 2020 and April 2021. Personal protective equipment and dedicated cleaning procedures were used in all departments. Of the 145 V/Q SPECT/CT scans included in the central review, PE could be excluded using only perfusion SPECT, perfusion SPECT/CT, or V/P SPECT/CT in 27 (19%), 55 (38%), and 45 (31%) patients, respectively. V/P SPECT/CT was positive for PE in 18 (12%) patients, including 12 (67%) with a low burden of PE (≤10%). Conclusion: In this population of COVID-19 patients assessed with lung scintigraphy, PE could confidently be excluded without the ventilation imaging in only 57% of patients. Ventilation imaging was required to confidently rule out PE in 31% of patients. Overall, the prevalence of PE was low (12%).

Keywords: COVID-19; SPECT; pulmonary embolism; ventilation perfusion scintigraphy.

Graphical abstract

FIGURE 1.

Results of central review. P = perfusion.

FIGURE 2.

Examples of negative perfusion SPECT/CT results, with perfusion defects (arrows) matched with chest CT findings of COVID-19 disease. P = perfusion.

FIGURE 3.

Examples of false-positive perfusion SPECT/CT results. Perfusion SPECT images showed perfusion defects (arrows), without significant abnormality on CT images. Perfusion SPECT/CT scans would therefore have been read as positive for PE. However, ventilation SPECT demonstrated matched defects. V/Q SPECT/CT scans were therefore interpreted as negative for PE. P = perfusion; V = ventilation.

FIGURE 4.

Examples of positive V/P SPECT/CT results. Perfusion SPECT images showed perfusion defects (arrows), whereas coregistered ventilation SPECT images showed normal ventilation (mismatched V/P defects). P = perfusion; V = ventilation.