Response to Bellaye et al. Measurement of hypoxia in the lung in idiopathic pulmonary fibrosis: a matter of control

We thank P-S. Bellaye and co-workers for their considered and insightful response. Given their finding of [18F]fluoromisonidazole ([18F]F-MISO) uptake in the bleomycin mouse model of fibrosis [1], we too were surprised not to demonstrate a similar signal in patients with idiopathic pulmonary fibrosis (IPF). However, as acknowledged, there are other examples of positron emission tomography (PET) tracers, such as cis-4-[18F]-fluoro-l-proline, yielding PET signals in animal lung fibrosis models that have not been replicated in humans with fibrotic lung disease [2, 3]. In vivo PET imaging in IPF patients shows no significant evidence of lung tissue hypoxia