This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ultrasonography, CT, and MRI, Subject name: Radiology
[{'content': 'Gadolinium is a contrast agent used for: \nSelect and explain. \nA. CT - angiography, B. Bronchography, C. MRI - Imaging, D. Contrast Sonography', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. (c) MRI - ImagingRef.: Harrison 19th ed. 1440* The most commonly used compounds for contrast enhancement are gadolinium-based and they improve the visibility of internal body structures in magnetic resonance imaging.* MRI contrast agents alter the relaxation times of atoms within body tissues where they are present after oral or intravenous administration.* This relaxation emits energy which is detected by the scanner and is mathematically converted into an image.* Gadolinium containing MRI contrast agents are used for enhancement of vessels in MR angiography or for brain tumor enhancement associated with the degradation of the blood-brain barrier.', 'role': 'assistant'}]