Pulmonary artery involvement in takayasu arteritis. PET/CT versus CT angiography

Objectives. To report a patient with Takayasu arteritis in whom 18F-Fluorodeoxyglucose (FDG) positron emission tomography (PET)/computerised tomography (CT) failed to demonstrate pulmonary artery involvement. Methods. A patient with Takayasu arteritis underwent PET/CT and CT angiography before and one year after immunosuppressive treatment. Results. Before treatment, PET/CT showed increased FDG uptake in the aortic arch and epiaortic arteries; pulmonary arteries were not visualised. Follow-up PET/CT one year later demonstrated resolution of abnormal vascular FDG uptake. CT angiography of the chest/abdomen prior to treatment revealed circumferential thickening of the ascending aorta, aortic arch, supra-aortic branches, and left inferior intralobar pulmonary artery with normal lumen diameter (27 mm). After therapy, CT angiography revealed decreased aortic wall thickening with complete resolution of intralobar wall thickening. However, the lumen of the central pulmonary artery was increased (32 mm). Conclusion. PET/CT is very sensitive in depicting active vasculitis, but cannot visualise the pulmonary arteries, presumably because their diameter is below the power of detection of PET/CT. CT angiography or magnetic resonance angiography is required to evaluate pulmonary artery abnormalities.