The Korle Bu Teaching Hospital in Accra, Ghana—the third largest hospital in Africa—houses two radiation machines for treating cancer patients. Both are relatively new, purchased by Ghana’s Ministry of Health in the last few years.
Both produce powerful X-rays that can penetrate your skin to kill tumor cells in your body. People from all over Ghana, even outside the country, come to the hospital to use the machines for cancer therapy.
“We have patients from Nigeria, Togo, and the Ivory Coast coming to us for treatment,” says Joel Yarney, an oncologist at the hospital.
One machine produces X-rays by accelerating electrons close to the speed of light through an intricately built copper pipe, then slamming them into a heavy metal target.
It’s called a linear accelerator, or linac for short, and it’s a cousin of the Higgs boson-discovering Large Hadron Collider. The other, known as an isotopic teletherapy machine, produces X-rays as silvery cobalt-60 chunks inside a small canister eject X-rays and transform into nickel through radioactive decay. Doctors then direct the X-rays toward a patient’s tumor.
The isotopic technology saves lives. But it’s also responsible for some of the most serious radiation accidents in history aside from the nuclear reactor meltdowns at Chernobyl and Fukushima.
Invented more than 60 years ago, these radioactive material-based machines soon became a fundamental tool for cancer treatment. They usually use cobalt-60 as a radioactive source, although some versions use a compound of cesium-137, cesium chloride.
Around 40 years ago, American hospitals started to replace them with linacs, whose X-ray beam is much easier to shape—and today, US hospitals use them pretty much exclusively.
“All else being equal, a doctor would prefer to have a linac than a cobalt machine because it’s better cancer treatment,” says Miles Pomper of the James Martin Center for Nonproliferation Studies.
But hospitals throughout the developing world still use isotope therapy to treat their sick. It’s not just Ghana, but Mexico, India, China—the list goes on.
The International Atomic Energy Agency, the world’s nuclear watchdog, actually keeps track of the machines in each country in a public database, because radioactive material in the wrong hands can have terrifying consequences.
Cancer patients sit in a chemotherapy ward while receiving treatment at the Korle Bu Teaching Hospital in Accra.
In 1987, a junkyard owner in Goiânia, Brazil purchased a canister of cesium chloride from two scrap metal collectors. They’d broken the canister from an abandoned machine while scavenging a partly demolished hospital.
The junkyard owner noticed that the cesium chloride glowed blue and thought it could be pieces of a valuable gemstone. He gave some bits of it to family and friends and ended up contaminating the local area. Four people died from radiation poisoning, and 28 had to be hospitalized for serious radiation burns.
More recent events follow an eerily similar script: abandoned machine, unsuspecting scrap metal collector. In 2000, two scrap metal vendors in Samut Prakan, Thailand broke open a canister of cobalt with a hammer and chisel.
They’d bought the canister as part of an old radiation machine. In the handling and the transport of the radioactive source, three people died. In 2010, the owner of a scrap metal shop near Delhi, India, bought an old cobalt machine at an auction.
When dismantling the machine, he cut the cobalt source into pieces to test for value. One man actually carried a piece in his wallet after he forgot he’d put it there. Seven people were hospitalized, and one man died from radiation exposure.
These were accidents, but nuclear security experts are growing worried that someone with malicious intent could steal this material. You can’t make a nuclear explosive with a small disc of cobalt or cesium chloride, but you could make a dirty bomb or poison a city’s water supply.
“Terrorism is one of our concerns,” says Ferenc Dalnoki-Veress of the James Martin Center for Nonproliferation Studies.
It also disrupts the lives of people who aren’t even exposed to the radiation. “It creates panic, and it disrupts the economy,” says Dalnoki-Veress. “If you have a serious event, and people don’t know if they’re sick, they overwhelm the medical system.”
So Dalnoki-Veress and Pomper are working as part of an international coalition to replace cobalt and cesium machines with linacs. Some participating groups include the IAEA, physics laboratory extraordinaire CERN, the International Cancer Expert Corps, and more.
But it’s not as simple as just getting a hospital to buy a linac and throw the cobalt machine away. Current linacs aren’t designed for use in developing countries. They have built-in computers that can read a CT scan, beam shapes tailored to avoid damaging healthy tissue, and lots of settings to serve as many patient types as possible.
That also means they require extensive training to operate. And in the US, hospitals actually outsource their maintenance to specialized consultants unavailable in developing countries.
So people are trying to design a simpler linac. Dalnoki-Veress and Pomper’s group have been working on this problem for several years, and they will meet in Vienna next week to discuss the progress in their designs.
Last November, the US Department of Energy put out a call for linac designs that use less electricity and can operate smoothly even in power outages on backup generators.
US company Varian released a new model last month called the Halcyon with developing countries in mind. They’ve automated many steps in the linac’s operation. “Our approach is: Make it super easy to use, but make it high quality,” says Mu Young Lee, Varian’s director of new product solutions.
The machine will cost $2 million to $4 million, depending on the hardware and software types that a customer selects. Halcyon’s price is comparable to those of linacs in US hospitals, although they’re working to make machines at other price points, Lee says.
One of Halcyon’s first customers is the Icon Group, Australia’s largest private cancer care provider, which plans to use it both domestically and in southeast Asia.
Yarney’s hospital in Ghana installed its linac about a year ago—but they still haven’t started using it. That’s because the power goes out a lot, and they couldn’t get it to work consistently. “When the machine was switched on, there were some power issues,” Yarney says. They didn’t want its spotty behavior disrupting a patient’s radiation treatment, which typically lasts about five weeks.
The hospital recently purchased some hardware, a voltage regulator, that will allow the linac to operate more smoothly during power interruptions. But when they start using the linac later this year, they’ll definitely keep using the cobalt.
It operates more consistently and needs less power. “The cobalt machine is more robust,” says Yarney. Cobalt may be a safety risk—but he still has to see patients.
Source : wired