Direct assessment of localised improvements in MCT in CF animal models – for example, in response to a CFTR airway gene therapy5– might provide a more rapid and targeted therapy-assessment than evaluation of whole lung changes, such as standard pulmonary function testing (e.g. FEV1), that may be insensitive to beneficial small changes and might take months to years to appear. Here, CFTR is linked to cystic fibrosis.