This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
[{'content': 'Which of the following contrast is used for esophageal perforation? \nSelect and explain. \nA. Barium swallow, B. Gadolinium, C. Lohexol, D. Gastrograffin', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ref. Grainger and Allison's Diagnostic Radiology. Page. 13\n\xa0\nNon ionic water soluble contrast should be used in most cases of esophageal perforation such as Iohexol .\nWater soluble contrast should be used instead of barium contrast to prevent barium related inflammation of the mediastinum if there is perforation .", 'role': 'assistant'}]