The world runs on rock · Story 8 of 12

The Body the metals inside medicine

A hospital scanner holds a magnet bathed in liquid helium and wound with niobium and titanium. A pacemaker runs on lithium inside a titanium case. A new hip is titanium and cobalt-chromium. And the most common nuclear scan depends on a handful of ageing reactors.

Scroll to open a scanner

A patient lies on the table of a large ring-shaped medical scanner lit in red while a clinician stands beside it — A medical scanner, from NASA's "Benefit from NASA" series on how digital image processing from the space programme moved into medicine. NASA (public domain).

Inside the ring

A magnet colder than space

Most MRI scanners use a superconducting magnet: coils of niobium-titanium wire that carry current with no resistance once cooled below about 9 kelvin. Liquid helium, which boils at 4.2 K, keeps them there.¹

Take it apart

Layers like a thermos

Cover a plastic shell
Vacuum vessel steel, keeping room heat out
Helium vessel about 1,500 to 2,000 litres of liquid helium in a typical magnet¹
Main coils niobium-titanium wire in copper
Gradient and radio coils close to the patient

Persistent current

Once the coils are charged, the current can run round them in a loop with no power supply at all, for as long as they stay cold.¹

The wire

Filaments in copper

Cut a wire across and it is a copper rod packed with fine niobium-titanium filaments. The copper supports them and, if the magnet warms and stops superconducting, gives the current somewhere safe to go.¹

NbTiCuHe

Follow the supply

1 · Helium

Helium is mostly recovered from natural gas. In 2025 the United States produced 81 million cubic metres, Qatar 63 million, Russia 18 million and Algeria 11 million, out of about 190 million worldwide. MRI took 15% of US helium use. The EU and US bans on Russian helium continued in 2025.²

Doha, Qatar, at night from orbit: a grid of orange and white lights along the coast

Doha, Qatar, at night from the International Space Station, May 2025. NASA (public domain).

2 · Titanium

Titanium metal starts as "sponge". China made 260,000 of the world's 370,000 tonnes in 2025, Japan 53,000. The United States made none; most of its titanium goes to aircraft, and some to medical implants.³

3 · Cobalt

The ball of many artificial hips is a cobalt-chromium alloy.⁴ DR Congo mined 74% of the world's cobalt in 2025.⁵

Inside a pacemaker

Lithium in a titanium shell

A pacemaker is sealed in titanium. Its battery, since Wilson Greatbatch's design of 1972, is a lithium-iodine cell that lasts about ten years.⁶

The lead

A thin insulated wire carries the pulses to the heart. Its electrodes are made of platinum-iridium, or titanium with an iridium surface, metals that do not corrode in the body.⁷

TiLiIPtIr

A new hip

Four parts, three materials

Stem titanium alloy for most cementless stems; cobalt-chromium for many cemented ones
Ball cobalt-chromium, or ceramic
Liner polyethylene, the new cartilage
Cup a titanium shell in the pelvis

Source: American Association of Hip and Knee Surgeons.⁴

Inside a round research-reactor hall: a central pool with railings, a tall containment wall and technicians in white — Inside NASA's Plum Brook research reactor, Ohio, 1961. It did not make medical isotopes, but the reactors that do are of this kind. NASA (public domain).

The scan that needs a reactor

Technetium-99m

About 80% of nuclear medicine procedures use technetium-99m, a short-lived isotope made from molybdenum-99, which is itself made by irradiating uranium targets in a few research reactors. The United States performs about half of these procedures worldwide.⁸

A handful of reactors

Where Mo-99 came from

In 2009 molybdenum-99 came from a handful of research reactors, the largest of them NRU at Chalk River in Canada, then 50 years old, and the High Flux Reactor at Petten in the Netherlands. NRU made about a third of the world's medical isotopes¹¹ and about half of the United States' Mo-99.⁹

14 May 2009

The reactor stops

NRU was shut down after a heavy-water leak was found in its vessel wall.¹¹ Petten's reactor had already been out from August 2008 to February 2009 and was due to close for repairs in early 2010.⁹¹⁰

2009 to 2010

Hospitals ration scans

By August a nuclear medicine department in London, Ontario, was receiving only 40% of its usual Mo-99. Like many clinics in Canada and the US it delayed non-urgent scans and switched patients to other tests. NRU's repairs ran into 2010.¹²

Why "critical"

No substitute in the clinic

None of these metals are used in large amounts in medicine; hospitals compete for them with chip plants, aircraft makers and rocket launches. When the supply of one breaks, it shows up as a postponed scan.

NbNiobiumBrazil 93% TiTitaniumsponge: China 70% CoCobaltDR Congo 74% CrChromiumSouth Africa 45% LiLithiumpacemaker cells PtPlatinum, iridiumelectrodes UUraniumMo-99 targets CuCoppermagnet wire

Next in the series: The Engine, the jet engine's hottest metals. Before this: The Shield, The Signal, The Rocket, The Magnet, The Battery, The Mind and The Chip.

Sources

Shares of world output are from USGS Mineral Commodity Summaries 2026 via our minerals data; helium and titanium sponge figures are from the USGS chapters below. The 3D models are illustrations, not engineering drawings or any one product. Photos: NASA, public domain.