A strong magnet and radio pulses cause hydrogen nuclei in the body to emit signals. A computer turns those signals into cross-section images of the part being examined.
The method does not use ionizing radiation. Muscle, organs, and fluid show more clearly than bone, which is the reverse of a plain X-ray.
How the Pictures Are Made
- Magnet. A strong magnet acts on hydrogen nuclei in the body.
- Radio pulses. The pulses cause those nuclei to emit signals.
- Computer. The computer assembles the signals into cross-section images.
Soft Tissue and Bone
An X-ray sends ionizing radiation through the body and records one flat shadow. Dense bone blocks more of that beam, so bone is easy to see and soft tissue is harder to separate. This scan does the opposite: bone is less visible, and the slices separate muscle, organs, and fluid that would overlap on a single shadow.
| Plain question | This scan | X-ray |
| What makes the picture | A strong magnet and radio pulses | A beam of ionizing radiation |
| Kind of picture | Cross-section images | One flat shadow |
| Bone and soft tissue | Bone is less visible than soft tissue | Bone shows clearly, and soft tissue is harder to separate |
Metal That Can Move
Metal which can move is unsafe in the magnet, so movable metal stays out of the room. The hazard is the magnet itself. The scan still does not use ionizing radiation.
