The process of getting x-ray pictures of the oesophagus or the upper gastrointestinal (GI) tract (esophagus, stomach, and duodenum). The x-ray pictures are taken after the patient drinks a liquid that contains barium sulphate (a form of the silver-white metallic element barium). The barium sulphate coats and outlines the inner walls of the oesophagus and the upper GI tract so that they can be seen on the x-ray pictures.