What Is a Proton Beam?

Proton beams are a highly specialized type of radiation therapy used in treating a number of cancerous tumors. Proton beam therapy has many advantages that make it a better choice for treatment than the standard (x-ray) radiation treatment.

Identification

The proton beams used in proton beam radiation therapy are produced by a particle accelerator, a highly specialized device that accelerates charged particles to high speeds with the use of electric fields.
Protons have a positive electric charge and are made to accelerate through the inner tube of the particle accelerator with the use of electromagnets that rapidly attract and repel the protons in turn, causing them to speed up. The particle accelerator is able to do this to a row of protons and then aim the resulting proton beam in a precise direction.

Function

In proton beam radiation therapy, the proton beam from a particle accelerator is aimed at a cancerous tumor. When the protons enter the body, they damage the DNA of the cancer cells, destroying that portion of the tumor.
As the protons leave the accelerator, they immediately begin to slow down; therefore, the proton beams are energized to a specific velocity that allows them reach the tumor before slowing down enough to cause substantial damage.

Benefits

In many ways, the use of proton beams as a form of radiation therapy is superior to traditional, x-ray based radiation. Conventional x-rays cannot be specifically targeted like proton beams, and they can damage healthy tissues. It is often difficult for physicians to determine how much radiation is too much or too little.
In addition, proton beams have been extremely successful at treating specific types of eye cancers that once required the removal of the eye.

Considerations

The biggest disadvantage of using proton beams as a radiation treatment is the staggering cost of the equipment. Particle acclerators must be housed in large buildings and require multi-story rotating machinery around the treatment chamber as well as shielding walls made of heavy concrete. It is not uncommon for facilities of this type to cost over $100 million.

Geography

There are a number of proton beam therapy centers in the United States, including the UC Davis Proton Facility in California, the Midwest Proton Radiotherapy Institute at Indiana University, and the University of Texas M.D. Anderson Cancer Center.

Resources

• Medicine Net provides information about the use of proton beams in therapy