From the Unit of Academic Radiology (A.J.S., D.C., J.M.W.) and Design, Trials & Statistics (M.J.C.), The School of Health and Related Research, University of Sheffield, Sheffield, UK; and Sheffield Pulmonary Vascular Disease Unit (J.H., C.E., R.C., D.G.K.), and Radiology Department (S.R., S.T.), Royal Hallamshire Hospital, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK. (At 2014-01)
