Which brain imaging technique uses magnetic fields and radio waves rather than X-rays to create detailed images?

Magnetic resonance imaging, or MRI, uses magnetic fields and radio waves rather than X-rays to create detailed brain images.

In MRI, a strong magnetic field aligns some atomic nuclei, especially hydrogen protons in water. Radio-frequency pulses disturb that alignment, and the returning signals are measured and mathematically reconstructed into images. Different pulse sequences emphasize different tissue properties, allowing clinicians and researchers to distinguish gray matter, white matter, fluid, tumors, strokes, and other abnormalities.

MRI does not use ionizing radiation, unlike computed tomography, which uses X-rays. However, MRI has important safety considerations: some implants and metal objects can be hazardous in the scanner’s strong magnetic field. The procedure can also be noisy and uncomfortable for people with claustrophobia.

Functional MRI uses changes related to blood oxygenation to estimate regional brain activity. It does not record neurons directly and has slower timing than electrical methods such as EEG. MRI, CT, PET, and EEG therefore answer different scientific and medical questions.