The New York Times has the article A Pinpoint Beam Strays Invisibly, Harming Instead of Healing.

The treatment Ms. Faber received, stereotactic radiosurgery, or SRS, is one of the fastest-growing radiation therapies, a technological innovation designed to target tiny tumors and other anomalies affecting the brain or spinal cord, while minimizing damage to surrounding tissue.

Because the radiation is so concentrated and intense, accuracy is especially important. Yet, according to records and interviews, the SRS unit at Evanston lacked certain safety features, including those that might have prevented radiation from leaking outside the cone.
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Despite their complexity, the multipurpose devices are less regulated than their more simply designed competitor, the Gamma Knife, a device engineered specifically for stereotactic radiosurgery.
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For years, the Gamma Knife provided the necessary power and accuracy to accomplish its goal.

But many institutions could not afford it; the device costs upwards of $3 million and requires its own room, and treatments take longer. There is also the added difficulty of handling and replacing radioactive material.

“It doesn’t pay to have a Gamma Knife unless you have a large number of patients,” said Dr. Amols.

When I needed brain surgery for a meningioma, I am sure glad I was living close to Portland, Oregon where I could receive Gamma Knife Surgery from a doctor who had studied with the inventor of the machine.  It is too bad that the hospital could not figure out how to transfer the MRI results to a neurologist in Massachusetts after I moved back here.  So what if the neurologist here has no way of comparing my current condition to what it was just before and just after the surgery. I guess it is not important.  After all it only involves my life.