Scientists at MIT, collaborating with an industrial team, are creating a proton-shooting system that could revolutionize radiation therapy for cancer. The goal is to get the system installed at major hospitals to supplement, or even replace, the conventional radiation therapy now based on x-rays.

The fundamental idea is to harness the cell-killing power of protons — the naked nuclei of hydrogen atoms — to knock off cancer cells before the cells kill the patient. Worldwide, the use of radiation treatment now depends mostly on beams of x-rays, which do kill cancer cells but can also harm many normal cells that are in the way.