X-ray machines produce an image on photographic film by using X-rays to expose the film in a way similar to visible light photography, but with the ability to pass through the body.
Here’s the step-by-step process:
- X-ray generation – Inside the X-ray tube, high-speed electrons collide with a metal target (usually tungsten), producing X-rays.
- Passing through the body – The X-rays travel toward the patient. Different tissues absorb X-rays at different rates:
- Dense tissues (bone, metal) absorb more X-rays, letting fewer reach the film.
- Soft tissues absorb less, letting more X-rays pass through.
- Film exposure – Behind the patient, there is a cassette containing X-ray-sensitive photographic film. The X-rays that pass through the body strike the film. Areas hit by more X-rays become more exposed, while areas blocked by dense tissue remain less exposed.
- Image formation – After exposure, the film is developed chemically.
- Heavily exposed areas (where X-rays passed easily) turn dark on the film.
- Light areas correspond to places where few X-rays reached the film (bones, dense objects).
- Resulting radiograph – The final image is a contrast pattern showing internal structures: bones appear white, soft tissues appear in shades of gray, and air-filled spaces appear black.