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: Radiology
[{'content': 'Inventor of orthopantomographic machine is: \nSelect and explain. \nA. Hounsfield, B. Roentgen, C. Kell, D. Numata', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Paatero and, independently, Numata were the first to describe the\xa0principles of panoramic radiography. Figure given shows a schematic view of the relationships between the X-ray source, the patient, the secondary collimator\xa0and the image receptor during panoramic image formation.', 'role': 'assistant'}]