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MRI scanner
1973 (Lauterbur's first MR image); first human body scan 1977; Damadian disputes credit· Invention or discovery· Medicine & surgery
DebatedHistorians or scientists disagree about what happened, when, or why.
A scanner that uses a strong magnet and radio waves to make detailed images of the body's soft tissues.
See it on the Technology & Medicine map →How it works
The body is mostly water, rich in hydrogen. A powerful magnet lines up hydrogen nuclei; radio pulses tip them over, and as they settle back they give off faint radio signals. Varying the magnetic field across the body reveals where each signal came from. Raymond Damadian reported in 1971 that tumours give different signals; Paul Lauterbur made the first image in 1973; Peter Mansfield developed fast imaging mathematics. Damadian's team scanned the first human body in 1977.
Why it mattered
It shows brain, spine, joints and organs in fine detail without ionizing radiation; functional MRI, from the early 1990s, even maps brain activity as people think.
How we know
Damadian's 1971 paper in Science, Lauterbur's 1973 paper in Nature, Mansfield's papers, the 2003 Nobel records, and Damadian's 'Indomitable' scanner at the Smithsonian.
Still unknown or debated
The 2003 Nobel went to Lauterbur and Mansfield; Damadian, who claimed he invented MRI, protested with full-page newspaper ads. How to weigh his role remains disputed.
Connections (2)
▸Faraday's electromagnetic induction lets coils read the signals of the MRI scannerWell documented
The connection
Faraday found in 1831 that a changing magnetic field makes current flow in a nearby wire. In an MRI scanner, hydrogen nuclei act like tiny spinning magnets; as they wobble after a radio pulse, their changing field induces a faint current in receiver coils. That current is the raw signal turned into images.
When and how
Faraday at the Royal Institution, London, August 1831; MRI's signal detection grew from 1946 nuclear magnetic resonance work by Felix Bloch at Stanford and Edward Purcell at Harvard.
How we know
MRI physics textbooks state the signal is picked up by electromagnetic induction in receiver coils, which is Faraday's law; the link is basic physics, not inference.
Debates and open questions
Not disputed. Engineering questions remain: stronger magnets give clearer signals, but very high-field scanners raise costs and safety questions.
▸CT scanner was followed by the MRI scannerWell documented
The connection
CT proved that a computer could turn many measurements into cross-section images, and its success created hospital demand for scanners. MRI used a similar reconstruction approach with a different signal: radio waves from hydrogen in a magnetic field instead of X-rays. It shows soft tissue such as brain, spine and joints better, without ionizing radiation.
When and how
CT in London, 1971; Lauterbur at Stony Brook, New York, 1973; Mansfield at Nottingham and Damadian in New York in the 1970s; commercial MRI scanners from the early 1980s.
How we know
Lauterbur's 1973 paper used back-projection, a CT-style reconstruction method, and EMI, CT's maker, also built early MRI research scanners.
Debates and open questions
Some argue MRI would have come anyway, since magnetic resonance was known from 1946; others think CT's commercial success made funding and hospital adoption far faster.