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
Inventor of orthopantomographic machine is: 
Select and explain. 
A. Hounsfield, B. Roentgen, C. Kell, D. Numata
D: Numata
Answer: D: Numata 
Explanation: Paatero and, independently, Numata were the first to describe the principles of panoramic radiography. Figure given shows a schematic view of the relationships between the X-ray source, the patient, the secondary collimator and the image receptor during panoramic image formation.