evaluation of ultra-low-dose chest computed tomography images in detecting lung lesions related to covid-19: a prospective study

Background: the present study aimed to evaluate the effectiveness of ultra-low-dose (uld) chest computed tomography (ct) in comparison with the routine dose (rd) ct images in detecting lung lesions related to covid-19. methods: a prospective study was conducted during april- september 2020 at shahid faghihi hospital affiliated with shiraz university of medical sciences, shiraz, iran. in total, 273 volunteers with suspected covid-19 participated in the study and successively underwent rd-ct and uld-ct chest scans. two expert radiologists qualitatively evaluated the images. dose assessment was performed by determining volume ct dose index, dose length product, and size-specific dose estimate. data analysis was performed using a ranking test and kappa coefficient (κ). p<0.05 was considered statistically significant. results: lung lesions could be detected with both rd-ct and uld-ct images in patients with suspected or confirmed covid- 19 (κ=1.0, p=0.016). the estimated effective dose for the rd-ct protocol was 22-fold higher than in the uld-ct protocol. in the case of the uld-ct protocol, sensitivity, specificity, accuracy, and positive predictive value for the detection of consolidation were 60%, 83%, 80%, and 20%, respectively. comparably, in the case of rd-ct, these percentages for the detection of groundglass opacity (ggo) were 62%, 66%, 66%, and 18%, respectively. assuming the result of real-time polymerase chain reaction as true-positive, analysis of the receiver-operating characteristic curve for ggo detected using the uld-ct protocol showed a maximum area under the curve of 0.78. conclusion: uld-ct, with 94% dose reduction, can be an alternative to rd-ct to detect lung lesions for covid-19 diagnosis and follow-up. an earlier preliminary report of a similar work with a lower sample size was submitted to the arxive as a preprint. the preprint is cited as: https://arxiv.org/abs/2005.03347