ROCHESTER — The Mayo Clinic announced plans Tuesday to open proton beam cancer therapy centers in Minnesota and Arizona that will offer a better-targeted form of radiation treatment than conventional X-ray therapies.

The centers in Rochester and Phoenix will use a technology called pencil beam scanning, which Mayo officials said allows greater control over radiation doses, shorter treatment times and fewer side effects.

Mayo said it will use the technology primarily for treating some head and neck, breast, gastrointestinal, lung, spine and prostate cancers, as well as tumors in or near the eye.

“Pencil bean scanning is the most accurate, precise way that we have to administer radiation therapy today,” Dr. Robert Foote, chairman of Mayo’s radiation oncology department in Rochester, said in a video statement.

Proton therapy can be considerably more expensive than traditional radiation, in part because of the cost of the facilities. Medicare and most insurance companies normally cover it. But experts debate whether the cost is worth it for many common kinds of cancer that can be treated with less-expensive means, particularly prostate cancer. Mayo said in its news release that proton therapy is considered more cost-effective in selected patients.

Foote said it’s especially beneficial for children, who suffer the greatest long-term harm from conventional X-ray therapy because their organs are still developing.

Nine other proton therapy centers are already in operation across the country, according to the National Association for Proton Therapy. Two others are under construction. Four others are now in development, including Mayo’s. These will be the first in Minnesota and Arizona

Mayo said in its news release that few of the other proton therapy centers exclusively use pencil beam scanning, which uses a much narrower beam that a traditional proton treatments, thus allowing doctors to more accurately and safely destroy only tumor tissue while better minimizing damage to surrounding tissue.

Each of Mayo’s two centers will have four treatment rooms. The first are expected to open by late 2014 or early 2015 in both locations, with the rest opening six to 12 months later.

Rochester’s center will cost about $188 million, while Phoenix’s will cost around $182 million. About 500 construction jobs will be created in each location. The Minnesota program will ultimately employ more than 120 new staff members, with more than 130 others in Arizona.