Perfusion lung scans during the pandemic: COVID-19 experience in a large trauma hospital

PURPOSE: To evaluate the results of perfusion only lung scans and the frequency of necessary addition of the ventilation part of the scans to diagnose acute pulmonary embolism (PE) during Corona Virus Disease of 2019 (COVID 19) pandemic. MATERIAL AND METHODS: We retrospectively reviewed perfusion lung scans’ results between April to December 2020. The images were interpreted by two experienced nuclear medicine physicians as daily routine studies. Ventilation images were performed only if deemed necessary for accurate diagnosis of acute PE. RESULTS: A total of 128 lung perfusion scans in 127 patients were included. The scans were interpreted with certainty using the modified PIOPID criteria in 122 patients (95.3%). The results included low probability for acute PE in 110 patients (85.9%), normal in 6 patients (4.7%) and high probability of acute PE in 6 patients (4.7%). Ventilation imaging were performed in 4 patients with high probability, after negative testing for COVID19. The other 2 high probability results were confirmed clinically and with radiologic imaging. Only 6 scans (4.7%) were interpreted as intermediate perfusion scans, two of which due to inability to differentiate old from new perfusion defects in patients with chronic thromboembolic disease. Thus, the true indeterminate results due to the lack of ventilation scan were encountered in only 4 intermediate probability lung scans (3.1%). Thus, the total number of requested ventilation scans was 8 scans (6.2%) when considering both the high and intermediate probability interpretations. Six scans were performed (2 in the intermediate and 4 in the high probability scans). The two ventilation scans performed in the intermediate probability changed the diagnosis to low probability and the four performed in the high probability confirmed the initial interpretation of high probability scans by perfusion only. CONCLUSION: The ventilation part of lung scans is required only in a small number of patients for certain interpretation of the result. Perfusion lung scans are sufficient for evaluation of acute PE with certainty in most patients.