A radiologist is a hospital doctor trained in radiation and in pictures of the inside of the body. A tidy learner-dictionary line may say they treat people with radiation, and that is not wholly false: some radiologists do procedures, and radiation belongs to their world. But the messy truth in most hospitals is this: the radiologist is the doctor who studies the X-rays and other scan pictures, then writes a report so other doctors know what they show. You often never meet them. You meet the radiographer who takes the picture; later your own doctor reads the radiologist’s words. The doctor whose main job is aiming a radiation beam at a cancer is more often called a radiotherapist, or a radiation oncologist. Students mix those titles constantly, and that is understandable — they all start with radio- and they all live in the same corridor.