This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Arterial Disorders, Subject name: Surgery
[{'content': 'Most reliable sign of injury to intrathoracic aorta is - \nSelect and explain. \nA. Presence of apical cap of pleural fluid, B. Depression of left main stem bronchous, C. Obliteration of aortic knob contour, D. Funny looking mediastenum', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. is \'c\' i.e., Obliteration of aortic knob contour * Several findings on the chest X ray are associated with the blunt injury to the intrathoracic great vessels.* The most reliable of these signs for the blunt aortic injury is loss of the aortic knob contour.Finding on Chest X-Ray Associated with Blunt Aortic InjuryPresence of widened mediastinum (> 8 cm at the aortic knob in adults)Deviation of the trachea, nasogastric tube, or endotracheal tube to the rightPresence of an apical cap of pleural fluidDepression of the left mainstem brochus > 140deg from trachea Obliteration of aortic knob contour"Funny" looking mediastinum', 'role': 'assistant'}]