Identification and Follow-up of COVID-19 Related Matching Ventilation and Perfusion Defects on Functional Imaging Using VQ SPECT/CT

Abstract

Purpose: Available clinical data have revealed that coronavirus disease 2019 (COVID-19) is associated with a risk of pulmonary microthrombosis and small airway disease. These patients present with varying degrees of perfusion abnormalities. The purpose of this study was to evaluate the use of a ventilation/perfusion single-photon emission computed tomography/computed tomography (VQ SPECT/CT) in the detection and follow-up of persistent lung perfusion abnormalities that were suspected to be due to pulmonary microthrombosis, small airway disease, or both.

Methods: A retrospective study was conducted at the department of nuclear medicine of Universitas Academic Hospital in Bloemfontein, South Africa. We reviewed the studies of 78 non-hospitalized patients with COVID-19 infection referred to our department from July 2020 to June 2021 for a perfusion only SPECT/CT study or a VQ SPECT/CT study. Pulmonary embolism was suspected in all 78 cases.

Results: Seventy-eight patients were studied. The median (interquartile range) age was 45 (41-58) years, and the majority (n = 69; 88.5%) were females. Twenty-two (28.2%) of these patients had matching VQ defects with mosaic attenuation on CT. All nine of the patients who had follow-up studies had these abnormalities persistently, even after 1 year.

Conclusion: We confirm that the VQ scan is a safe and effective tool to identify and follow-up recovered COVID-19 patients with persistent ventilation and perfusion abnormalities suspicious of small airway disease and pulmonary microthrombosis.

Keywords: COVID-19; Mosaic hypoattenuation; Pulmonary microthrombosis; Small airway disease; VQ SPECT/CT.

Fig. 1

Perfusion SPECT (above) and CT (below) of a 35-year-old female, who presented with persistent shortness of breath, 2 days after de-isolation following COVID-19. The SPECT images show a large perfusion defect in the medial segment of the right middle lobe, with corresponding mosaic hypoattenuation on the CT

Fig. 2

Perfusion SPECT (above) and ventilation SPECT (below) of the same patient in Fig. 1 a, performed a year after the baseline study shows persistence of the perfusion defect, which is matched on the ventilation images

Fig. 3

Perfusion SPECT (above) and CT (below) of a 35-year-old female, who presented with persistent chest pain and shortness of breath, 5 days after de-isolation following COVID-19. The SPECT images show a large perfusion defect in the medial segment of the right middle lobe, with corresponding mosaic hypoattenuation on the CT. However, there is evidence of calcification noted on CT in the affected segment

Fig. 4

Perfusion SPECT (above) and CT (below) of the same patient in Fig. 2 a, performed 1 year after the baseline study, showing persistence of the defect, despite being on anticoagulation therapy for 6 months. Note that the calcification is still present

Fig. 5

Perfusion SPECT images of a 15 year old female, with systemic lupus erythematosus, who presented with unexplained resting tachycardia and shortness of breath and a diagnosis of pulmonary embolism was made on a VQ SPECT/CT. The images below are the baseline study, showing large perfusion defects in the apical posterior segment of the left upper lobe and medial and lateral segments of the right middle lobe. The images above performed 6 months after initiation of therapeutic anticoagulation shows complete resolution of all the defects