The detection of COVID-19 by reverse transcription polymerase chain reaction (RT-PCR) has varying sensitivity. CT of the chest can verify the infection in patients with clinical symptoms and a negative test result accelerating treatment and actions to prevent further contagion. However, CT employs ionizing radiation. The purpose of this study was to evaluate protocol settings, associated radiation exposure, image quality and diagnostic performance of a low-dose CT protocol in a university hospital setting.
Chest-CT examinations were performed on a single scanner (Somatom Definition Edge, Siemens Healthineers, Germany) in 105 symptomatic patients (60 male, 45 female). Images were evaluated with regard to protocol parameters, image quality, radiation exposure and diagnostic accuracy. Serial RT-PCR served as the standard of reference. Based on this reference standard sensitivity, specificity, positive and negative predictive values of CT with 95% confidence interval were calculated.
The mean effective dose was 1.3 ± 0.4 mSv (0.7 – 2.9 mSv) for the patient cohort (mean age 66.6 ± 16.7 years (19-94 years), mean BMI 26.6 ± 5.3 kg/m² (16-46 kg/m²)). A sensitivity of 100 [95% CI: 82-100]%, a specificity of 78 [95% CI: 68-86]%, a positive predictive value of 50 [95% CI: 33-67]% and a negative predictive value of 100 [95% CI: 95-100]% were obtained. No COVID-19 diagnoses were missed by CT. Image noise did not strongly correlate with BMI or patient diameter and was rated as average.
We presented a robust imaging procedure with a chest CT protocol for confident diagnosis of COVID-19. Even for an overweight patient cohort, an associated radiation exposure of only 1.3 ± 0.4 mSv was achieved with sufficient diagnostic quality to exclude COVID-19.
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