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Aim: To assess the specificity of COVID-19- associated pneumonia detection by radiologists using a chest CT scan.Materials and methods: From mid-February to early March 2020, 65 patients have been retrospectively selected from the Moscow City Clinical Hospital database; all of them had been treated in an inpatient facility with a verified diagnosis of COVID-19. In addition, 75 patients from the Unified Radiological Information Service have been randomly selected. In December 2019, these outpatients had been sent by an attending physician for a chest CT scan with suspected pneumonia. The imaging studies showed non-specific inflammation signs in the lungs. All 140 scans were analyzed by seven radiologists from different Russian cities, who independently categorized each study as “COVID-19” or “Other pneumonia”.Results: Chest computed tomography had a 92% specificity in the differential diagnosis of COVID-19-associated pneumonia, and its specificity in the general population is expected to be at least 80% with a high probability. The inter-rater variability was low (coefficient of variation for specificity 12.6%). The sensitivity in our study was 76.2%, and the coefficient of variation for sensitivity 23.5%. These findings are generally consistent with other studies. The primary study limitation is the absence of a sample with confirmed pneumonia caused by other viruses.Conclusion: Chest CT is highly specific for the detection of COVID-19-associated pneumonia.

Background: Since 2017, a pilot project for lung cancer screening by chest low dose computed tomography (LDCT) has been implemented in Moscow. Patients to be included into the screening have risk factors for ischemic heart disease (IHD). The association between epicardial adipose tissue (EAT) volume and coronary artery atherosclerosis, IHD, and atrial fibrillation has been demonstrated previously.Aim: To demonstrate the feasibility of LDCTbased EAT volumetry using a dynamic (contracting) heart phantom.Materials and methods: The study was performed with the designed dynamic heart phantom and chest phantom in two stages. At stage I, two adipose tissue pieces were scanned inside and outside the chest phantom using CT and LDCT. At stage II, the dynamic heart phantom was scanned outside and inside the chest phantom. In addition, we scanned the heart phantom with a coronary calcium phantom. The contracting heart phantom was developed within three months. All scans of the phantom were performed within one day. We determined the adipose tissue thresholds in LDCT and the EAT volumetric error with both chest CT and LDCT. Measurements of the adipose tissue volumes were performed by the radiologist twice with semi-automatic software.Results: The results of stage I helped to identify optimal density thresholds for LDCT-based adipose tissue volumetry in lung cancer screening, ranging from -250 HU to -30 HU. The stage II results showed that for all heart phantom scanning variants, the average EAT volumetry error did not exceed 5%, except for the case of contracting heart phantom with added coronary calcium in a chest phantom with body mass index (BMI) 29 (-5.92%). Adding the coronary calcium phantom to the heart phantom in LDCT increased the error by an average of 4% in BMI 23 and BMI 29 chest phantoms.Conclusion: LDCT-based EAT volumetry with fat density threshold from -250 HU to -30 HU is feasible in lung cancer screening, including patients with coronary calcium. However, considering the phantom design, further patient studies, and correlation of EAT volumes between LDCT for lung cancer screening and сoronary CT angiography are required.