Once physicists started accelerating particles to high energies in the 1930s, it didn’t take them long to think of a killer app for this new technology: zapping tumors.
Standard radiation treatments, which had already been around for decades, send X-rays straight through the tumor and out the other side of the body, damaging healthy tissue both coming and going. But protons and ions — atoms stripped of electrons — slow when they hit the body and come to a stop, depositing most of their destructive energy at their stopping point. If you tune a beam of protons or ions so they stop inside a tumor, you can deliver the maximum dose of radiation while sparing healthy tissue and minimizing side effects. This makes it ideal for treating children, whose developing bodies are particularly sensitive to radiation damage, and for cancers very close to vital tissues such as the optic nerves or spinal cord.
Today, nearly 70 years after American particle physicist Robert Wilson came up with the idea, proton therapy has been gaining traction worldwide and in the United States, where 14 centers are treating patients and nine more are under construction. Ions such as carbon, helium and oxygen are being used to treat patients in Germany, Italy, China and Japan. More than 120,000 patients had been treated with various forms of charged-particle therapy by the end of 2013, according to the Particle Therapy Co-Operative Group.
New initiatives from CERN research center in Europe and the Department of Energy and National Cancer Institute in the United States are aimed at moving the technology along, assessing its strengths and limitations and making it more affordable.
And physicists are still deeply involved. No one knows more about building and operating particle accelerators and detectors. But there’s a lot more to know. So they’ve been joining forces with physicians, engineers, biologists, computer scientists and other experts to make the equipment smaller, lighter, cheaper and more efficient and to improve the way treatments are done.
“As you get closer to the patient, you leave the world accelerator physicists live in and get closer to the land of people who have PhDs in medical physics,” says Stephen Peggs, an accelerator physicist at Brookhaven National Laboratory.
“It’s alignment, robots and patient ergonomics, which require just the right skill sets, which is why it’s fun, of course, and one reason why it’s interesting — designing with patients in mind.”