During radiation, a beam of gamma rays hits a tumor and produces electrons that have a long path length, with electrons often traveling beyond the tumor and into healthy tissue. An electron is a different elementary particle than a neutron, with lighter mass and a negative charge.
In neutron therapy, a beam of neutrons is targeted at a tumor that has been injected with the chemical boron, a nonradioactive isotope. The neutrons cause the boron nuclei to split, releasing alpha particles that damage surrounding cells. The path length of alpha particles is the diameter of a few cells, much shorter than the path length of electrons. "Gamma rays often wander around in the healthy tissue," Grimes says. "Neutrons don't go very far once they hit matter."
Neutron beams used in these kinds of experiments are created with a machine called an accelerator. Ohio University's accelerator, which was built in 1968, speeds atomic particles to high energies -- up to 7 percent of the speed of light -- through a large dome charged to a high voltage by a moving belt.
What makes the university's accelerator unique are recent technological additions that allow it to measure the speed and number of neutrons with new levels of precision. In 1981, a 100-foot culvert was built into the side of a hill next to the university's accelerator laboratory. The culvert allows researchers to measure how long it takes neutrons to travel a certain distance.
Using this technology, researchers can determine the correct amount of
neutrons and the speed of neutrons needed to treat certain types of cancers and
tumors, Grimes says. For example, researchers would use a low-energy neutron
beam to target a tumor close to the skin, while a high-energy beam would be used
to target a m
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Contact: Melissa Rake
rake@ohio.edu
740-593-1891
Ohio University
3-Mar-1999