Quantification of the α_vβ₆ Integrin by PET/CT Imaging in the Lungs of Patients After SARS-CoV2 Infection and Comparison to Fibrotic Lungs

TO THE EDITOR: We were interested to read the recent article by Foster et al. (1) describing early experience of α_vβ₆ PET/CT imaging of the lungs after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

We would like to point out that the suggestion that the α_vβ₆ uptake in lung regions affected by SARS-CoV-2 is 3 times that which we reported previously for fibrotic lung (2) may be misleading. Foster et al. report an SUV_max of approximately 3.0 in SARS-CoV-2 and compare this with our reported value of 1.03 in subjects with idiopathic pulmonary fibrosis. However, our value is the SUV_mean averaged over the whole lung volume, which will be systematically lower than SUV_max. Although we did not perform an equivalent analysis, and the color scale in our example images (Lukey et al. (2), Fig. 1) was chosen to enable comparison with the healthy participants rather than visualization of the maximal value, we can confirm qualitatively that localized SUVs of 3.0 or more were observed widely in the fibrotic lung regions in our study.

Clearly, more data and appropriate analyses (3) would be needed to make a valid quantitative comparison, particularly given the potential influence of tissue fraction (4) and the known (micro)-vascular component of the SARS-CoV-2 disease mechanism (5), which might influence the blood signal.

We look forward to seeing more results from this important work in due course.

• © 2022 by the Society of Nuclear Medicine and Molecular Imaging.