Science
How does an MRI scanner work?
An MRI scanner works by using a powerful magnet and radio waves to map the water in your body. It nudges hydrogen atoms in your tissues, listens to the faint signals they send back, and builds detailed cross-sections — with no X-rays or radiation.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how an MRI scanner works.
Step by step
- 1A strong magnet (often superconducting) lines up hydrogen atoms in the body's water.
- 2A radio-wave pulse knocks those atoms out of alignment.
- 3As they snap back, they emit tiny signals the scanner detects.
- 4Different tissues return signals differently, building a detailed 3D image.
- 5It uses no ionizing radiation, unlike X-rays and CT scans.
Frequently asked questions
- Does an MRI use radiation?
- No. MRI uses magnetism and harmless radio waves, not ionizing radiation — a key advantage over X-rays and CT scans.
- Why is an MRI so loud?
- Rapidly switching magnetic-field coils vibrate strongly, producing the loud knocking and buzzing sounds during a scan.
- Why can't you wear metal in an MRI?
- The magnet is extremely strong and can violently pull metal objects, so loose metal and many implants are dangerous near the scanner.