Marie Ludwig

Background The role and performance of chest CT in the diagnosis of the coronavirus disease 2019 (COVID-19) pandemic remains under active investigation. Purpose To evaluate the French national experience using chest CT for COVID-19, results of chest CT and reverse transcription polymerase chain reaction (RT-PCR) assays were compared together and with the final discharge diagnosis used as the reference standard. Materials and Methods A structured CT scan survey (NCT04339686) was sent to 26 hospital radiology departments in France between March 2, 2020, and April 24, 2020. These dates correspond to the peak of the national COVID-19 epidemic. Radiology departments were selected to reflect the estimated geographic prevalence heterogeneities of the epidemic. All symptomatic patients suspected of having COVID-19 pneumonia who underwent both initial chest CT and at least one RT-PCR test within 48 hours were included. The final discharge diagnosis, based on multiparametric items, was recorded. Data for each center were prospectively collected and gathered each week. Test efficacy was determined by using the Mann-Whitney test, Student t test, χ2 test, and Pearson correlation coefficient. P < .05 indicated a significant difference. Results Twenty-six of 26 hospital radiology departments responded to the survey, with 7500 patients entered; 2652 did not have RT-PCR test results or had unknown or excess delay between the RT-PCR test and CT. After exclusions, 4824 patients (mean age, 64 years ± 19 [standard deviation], 2669 male) were included. With final diagnosis as the reference, 2564 of the 4824 patients had COVID-19 (53%). Sensitivity, specificity, negative predictive value, and positive predictive value of chest CT in the diagnosis of COVID-19 were 2319 of 2564 (90%; 95% CI: 89, 91), 2056 of 2260 (91%; 95% CI: 91, 92), 2056 of 2300 (89%; 95% CI: 87, 90), and 2319 of 2524 (92%; 95% CI: 91, 93), respectively. There was no significant difference for chest CT efficacy among the 26 geographically separate sites, each with varying amounts of disease prevalence. Conclusion Use of chest CT for the initial diagnosis and triage of patients suspected of having coronavirus disease 2019 was successful. © RSNA, 2021 Online supplemental material is available for this article.

INTRODUCTION: Lung cancer screening in individuals at risk has been recommended by various scientific institutions. One of the main concerns for CT screening is repeated radiation exposure, with the risk of inducing malignancies in healthy individuals. Therefore, lowering the radiation dose is one of the main objectives for radiologists. The aim of this study is to demonstrate that an ultra-low dose (ULD) chest CT protocol, using recently introduced hybrid iterative reconstruction (ASiR-V, GE medical Healthcare, Milwaukee, Wisconsin, USA), is as performant as a standard 'low dose' (LD) CT to detect non-calcified lung nodules ≥4 mm. METHODS AND ANALYSIS: The total number of patients to include is 150. Those are referred for non-enhanced chest CT for detection or follow-up of lung nodule and will undergo an additional unenhanced ULD CT acquisition, the dose of which is on average 10 times lower than the conventional LD acquisition. Total dose of the entire exam (LD+ULD) is lower than the French diagnostic reference level for a chest CT (6.65 millisievert). ULD CT images will be reconstructed with 50% and 100% ASiR-V and LD CT with 50%. The three sets of images will be read in random order by two pair of radiologists, in a blind test, where patient identification and study outcomes are concealed. Detection rate (sensitivity) is the primary outcome. Secondary outcomes will include concordance of nodule characteristics; interobserver reproducibility; influence of subjects' characteristics, nodule location and nodule size; and concordance of emphysema, coronary calcifications evaluated by visual scoring and bronchial alterations between LD and ULD CT. In case of discordance, a third radiologist will arbitrate. ETHICS AND DISSEMINATION: The study was approved by the relevant ethical committee. Each study participant will sign an informed consent form. TRIAL REGISTRATION NUMBER: NCT03305978; Pre-results.

Introduction: Lung cancer screening using computed tomography (CT) is currently being discussed but repeated radiation exposure is a real concern. The aim of npUBD (NCT03305978), a prospective monocentric study, is to show that an ultra-low dose (UBD) CT using recently introduced iterative reconstruction (ASIR-V) is as efficient as a reference low-dose (BD) CT for the detection of ≥4mm uncalcified pulmonary nodules. Methods and analysis: For each patient included in the study (150 planned), a UBD CT is performed in addition to the reference BD CT. This additional UBD CT is reconstructed with 50 and 100% ASIR-V (UBD50; UBD100). The 3 anonymized series are read independently by 2 pairs of radiologists. The detection sensitivity of ≥4mm uncalcified pulmonary nodules with UBD CT versus BD CT is the main judgement criterion. Secondary objectives include concordance of nodules, emphysema and coronary calcifications. Interim results: Among the first 50 patients, 10 were secondarily excluded for the following reasons: ≥6 nodules in at least one lung (n=9) and BMI>35 (n=1). 55 nodules were identified in 26 patients on the reference BD. Mean effective dose is 1.3mSv for UBD and 0.1mSv for BD. The UBD versus BD detection rate is 72.7% (UBD50) and 76.4% (UBD100) (p>0.05), ranging respectively from 50 and 58.3% for ground glass nodules to 78.9 and 81.6% for solid nodules. Conclusion: The radiation dose delivered by UBD is <10% to that of BD CT. The intermediate results show a lower detection rate of ≥4mm pulmonary nodules than expected but need to be confirmed by the final analysis.