We greatly appreciate the comments [1] regarding our article [2] and thank the authors for their interest. The aim of our publication was indeed to highlight the potential benefit of spectral CT in the evaluation of coronavirus disease (COVID-19). Our study was a feasibility study, covering a short period during the first COVID-19 pandemic wave in France in early March 2020 (our article was submitted on April 30, 2020). This short period and the fact that we performed a retrospective investigation that included patients who underwent initial and follow-up chest CT on our spectral CT scanner explain the very small sample. However, our study was a preliminary work whose purpose was limited to determining whether spectral CT and notably electron density imaging performed better than conventional CT for detecting subtle ground-glass opacities at an early stage, thereby facilitating the semiquantitative assessment of lesion extent. A more detailed study of electron density imaging with a broader analysis of items in a larger number of patients is needed. Spectral imaging seems to also hold promise for detecting other COVID-19 lung features seen in different stages of the infection, but this point was not addressed in our preliminary study.

The potential role of CT in predicting disease progression and clinical outcomes is being investigated by many groups [3, 4]. Whether spectral CT adds to the information obtained with conventional CT and clinical variables warrants specific studies. A multicentric study on spectral CT including 97 patients with COVID-19 confirmed by reverse transcription–polymerase chain reaction whose clinical outcomes are known is being conducted in France; statistical analysis is in progress.

Although our study pursued a limited objective, we believe that the utility of electron density imaging in improving the detection of subtle ground-glass opacities and facilitating assessment of lung lesion extent is of interest to clinicians treating patients with COVID-19.