Technology that was originally designed to test nuclear weapons is now being used to kill cancer cells with minimal damage to surrounding tissues.

There was a time when the word “nuclear” conjured up images of mushroom clouds and destruction. But in recent decades, nuclear technology has been recognized as a safe, reliable and emissions-free power source, and on the scientific scene it’s morphed from a force of destruction to one of healing. U.S. Department of Energy (DOE) research has made significant contributions to the growing and important field of nuclear medicine. Building on technology originally designed to test nuclear weapons, a team of scientists at Lawrence Livermore National Laboratory in Livermore, California, has designed a compact system to kill cancer cells, while doing minimal harm to the body’s surrounding tissue.

It’s called proton therapy, and at the present time the machines that deliver the cancer-killing proton beams are so large and costly that only six centers exist in the United States (25 throughout the world). But Livermore research has managed to come up with a design that’s smaller and cheaper, that will make the therapy much more accessible to hospitals and patients who need it.

Proton therapy is a cousin to the more familiar forms of radiation therapy that use a beam of X-rays to deliver their cancer-killing blow. As X-rays enter the body they crash into the cells in their path, giving up energy as they grind to a halt. That energy kills cells, which is great for cancer cells, but not for the healthy cells that make up the surrounding skin and tissues.

George Caparoso, one of the investigators on the project, explained that X-rays tend to give up their energy close to the surface of the body and are hard to target at precise depths. As a result, it’s often very difficult to successfully treat tumors that lie deep under the skin without inadvertently damaging other tissues and organs. As an example, a woman with breast cancer who has traditional radiation therapy likely is treating more than just the tumor in her breast. “What you’ll find is that you’ll get doses to the tumor, but you’ll also get doses to the lung and sometimes even to the heart,” Caparoso said.

But heavy protons behave fundamentally differently than the massless photons found in X-rays. They are easier to target and control. Proton therapy machines accelerate protons to a speed that corresponds to the precise depth of the tumor cells. “By adjusting the energy of the proton, you adjust how far in it stops,” said Caporoso. And what’s more, the protons do almost all their damage right when they hit the target, leaving neighboring cells virtually undisturbed.

But getting those weighty protons moving fast enough requires a big accelerator, a massive superstructure that’s three stories tall and costs $150 to 200 million. Caparoso and his colleagues had been working for years on reducing the size of X-ray machines used to image bombs, when he was asked by a colleague if he could do the same thing for proton machines used in medicine. A collaboration was born, and today the project is a few years away from being a commercial product that will fit into hospitals and radiation therapy treatment centers.

And while Caparoso’s group would like to use nuclear technology to replace X-rays that kill cancer, scientists at the Thomas Jefferson National Accelerator Facility (Jefferson Lab), another DOE nuclear physics lab, are developing nuclear imaging systems that in some cases are better than X-rays at finding and identifying certain tumors. A mammogram is an X-ray of the breast, and it’s the standard of care for detecting breast cancer. But because mammograms only show structural differences in tissue density, they can be misleading, explained Jefferson Lab scientist Drew Weisenberger.

“A tumor may have the same density as healthy tissue, but it behaves differently,” Weisenberger said. In mammograms of women’s breasts that have very dense tissue, or fibroids, it is difficult to differentiate between noncancerous and cancerous masses. This can lead to false-positive results or missed tumors.

A mammogram also may miss behavior, which is key to another imaging technology used to detect tumors. The technology takes advantage of the fact that tumors are living masses of cells with metabolic requirements different from healthy cells. For instance, many tumor cells often are growing and dividing at a high rate. This behavior can be identified by the use of radioactively tagged molecules called radiopharmaceuticals. By injecting a patient with a radiopharmaceutical, doctors can monitor where it goes with nuclear medicine imaging technology. If the radiopharmaceutical accumulates in one region of the breast, there is a good chance there’s a tumor, Weisenberger explained.

Jefferson Lab has improved on earlier nuclear medicine clinical devices that were not designed specifically for the breast. So why wasn’t nuclear medicine imaging being used to assist in breast cancer detection? The original units were too large and bulky, and clinicians weren’t convinced that they worked. “Because the resolution and sensitivity weren’t high enough; the results didn’t offer more than mammography,” said Weisenberger.

The compact nuclear medicine imaging system developed at Jefferson Lab uses a special crystal, called a scintillator, to detect the radiopharmaceutical and generate an image. Existing clinical systems were the size of a trash-can lid and not designed to distinguish small (centimeter-sized) masses in the breast. The Jefferson Lab device is smaller and more sensitive and provides higher-resolution images, while being about the same size as a mammography machine. Dilon Technologies of Newport News, Virginia, has licensed the technology and it is in clinical use.

Weisenberger says that a mammogram is the first step for all women, with nuclear medicine imaging serving as an additional, complementary tool. If one of his loved ones had breast cancer, Weisenberger said, he would insist on using the new technology.