key: cord-0710642-nwfnsv5l
authors: de Burgt, Alina van; Smit, Frits; Anten, Sander
title: Rubidium-82 PET/CT in COVID-19
date: 2021-08-17
journal: Radiol Case Rep
DOI: 10.1016/j.radcr.2021.08.027
sha: 2abb7a95ac7460ce68812c9f52b62c0e328d5581
doc_id: 710642
cord_uid: nwfnsv5l

A 56-year-old man presented to the emergency department with shortness of breath during the COVID-19 pandemic. Chest computed tomography angiography (CTa) showed bilateral peripheral ground-glass opacifications classified as CO-RADS 5, but no pulmonary embolism. To analyze the possibility of CTaundetectable pulmonary microthrombi and to rule out cardiac perfusion abnormalities, we decided to perform a rubidium-82 (82Rb) PET/CT. 82Rb PET/CT imaging in this patient yielded uptake in the pulmonary areas of ground-glass opacification and showed. Moreover, higher 82Rb uptake was shown in the lobe with the highest density on CT. The ejection fraction was normal (56%) and no pulmonary embolism or other defects were detected. To our knowledge, this is the first time 82Rb PET/CT was performed for suspected pulmonary microthrombi in a COVID-19 patient. This case report shows corresponding findings between 82Rb PET/CT and CTa imaging without and does not show any signs of microthrombi despite the elevated d-dimer. Even in the Response to Reviewers (without Author Details) areas of profound groundglass opacifications, the increased 82Rb uptake indicates that perfusion is adequate to acquire 82Rb uptake in the de pulmonary cells. 82Rb PET/CT is a promising imaging technique and might extend the diagnostic potential of conventional nuclear and radiological imaging imaging techniques as CTa in detecting pulmonary microthrombi or other minor perfusion defects. To show sufficient evidence for the use of 82Rb PET/CT in clinical practice for COVID-19, validation should take place in a future prospective clinical trial, studying a large patient cohort.

Since first emerging in China in late 2019, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide, overwhelming healthcare systems and resulting in more than 150 million people gettingto be infected and more thanover 3.5 million deaths globally [1] . Severe coronavirus disease 2019 (COVID-19) typically starts one week to ten days after the onset of symptoms and presents with fever, dyspneadyspnoea and hypoxia. Respiratory failure is the most common cause of death in COVID-19. Major complications are pneumonia, multisystem organ failure, and acute respiratory distress syndrome (ARDS) and venous orand arterial thromboembolic complications. [2,3] A hypercoagulable state associated with hyperinflammation is the most likely cause of these coagulation abnormalities which areis distinctive fromof disseminated intravascular coagulation (DIC). This particular hypercoagulable state has been referred to as COVID-19-associated coagulopathy (CAC) [4, 5] .

Pulmonary embolism (PE) can worsen pneumonia or ARDS associated respiratory failure. Autopsy studies have also showned widespread microthrombi in alveolar capillaries both in patients with and patients without segmental or subsegmental PE besides the usual detection of PE located in pulmonary segmental or subsegmental arteries [6, 7] . However, aAssessing patients for the occurrence of microthrombi using conventional imaging However, it is difficult however to evaluate the presence of microthrombi in the alveolar capillaries with conventional imaging due to the its small size of alveolar capillaries (5 to 10 micrometres (μm)) [8]. This may lead to under detection of pulmonary thrombosis and might refrain keep the patient from potential beneficial treatment with anticoagulation therapy. Therefore, PET/CT imaging with the perfusion tracer rubidium-82 ( 82 Rb) may provide functional information regarding the alveolar perfusion in COVID-19 patients with suspected pulmonary microthrombi and hence might guide treatment decision making.

A 56-year-old man presented to the emergency department with shortness of breath during the COVID-19 pandemic. He had been in his usual unremarkable state of health until one week earlier when he developed a cough, fatigue and progressive dyspneadyspnoea. He also experienced a syncope twice. Oropharyngeal PCR was positive for the SARS-CcoVv-2 virus. Work up revealed a CRP of 9 mg/L, an increased Alveolar-arterial gradient of 4.5 kPa and an elevated d-dimer of 4309 ug/L.

Chest computed tomography angiography (CTa) showed bilateral peripheral groundglass opacifications classified as CO-RADS 5 ( fig. 1 ), but no pulmonary embolism. The patient was admitted for oxygenation support.

To analyze the possibility of CTa-undetectable pulmonary microthrombi that could explain the syncope and to rule out cardiac perfusion and function abnormalities, we decided to perform 82 Rb PET/CT, as depicted in fig. 2 . 82 Rb is the most commonly used PET perfusion tracer for myocardial perfusion imaging [9] . It is a potassium analog that is rapidly extracted rapidlys from the blood and is taken up by the cardio myocytes which are dependent on coronary blood flow [10]. 82 Rb PET/CT imaging in this patient yielded uptake in the pulmonary areas of groundglass opacification.

Moreover, the left pulmonary upper lobe showed higher 82 Rb uptake compared to the remainder of the lung, which corresponded with the increased density in that lobe on CTa. The ejection fraction (EF) was normal (56%) and no pulmonary embolismPE or other defects were detected.

To our knowledge, this is the first time 82 Rb PET/CT was performed for suspected pulmonary microthrombi in a COVID-19 patient. This case report shows corresponding findings between 82 Rb PET/CT and CTa imaging and does not show any signs of microthrombi despite the elevated d-dimer.

Even in the areas of profound groundglass opacifications the increased 82 Rb uptake indicates that perfusion is adequate to acquire 82 Rb uptake in thede pulmonary cells. These findings therefore do not support the theory of pulmonary hypoperfusion in patients with Rb PET/CT is a promising imaging technique and might extend the diagnostic potential of conventional nuclear and radiological imaging techniques as CTa in detecting pulmonary microthrombi or other minor perfusion defects. To demonstrateshow sufficient evidence for the use of 82 Rb PET/CT in clinical practice for COVID-19, validation should take place in a future prospective clinical trial, which studiesstudying a large cohort of patientst cohort.

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. 

An interactive web-based dashboard to track COVID-19 in real time