Advanced Imaging


Advanced Imaging Magazine

Updated: July 8th, 2008 05:26 PM CDT

Stereotactic Radiosurgery

Treatment Planning for Stereotactic Radiosurgery is One of the Most Complex and Interesting Imaging Applications in Use Today
Critical white matter nerve fibers within the brain are tracked using the iPlan software.
The BrainLAB AG beam shaper.
iPlan can facilitate treatment through image fusion.
Automatic organ (brain) segmentation at work with iPlan.
A dose plan being developed with iPlan.

By Leonard A. Hindus
Contributing Editor

Author's Note: In January of 2002 my wife, who had been extremely healthy up to that point, was diagnosed with advanced lung cancer. To make matters worse, they found that lung tumor had sent metastasis to her brain—brain tumors. That prospect was even more frightening than the lung cancer. The traditional treatments for brain tumors were equally threatening. Brain surgery was on option, if the tumor was operable. That carried unknown risks depending upon the location of the tumor. The other option was whole brain radiation. In order to deliver enough radiation to effect the tumor, the entire brain had to be exposed to high doses of radiation. Side effects could include memory loss, vision problems, even balance issues.

Then the Doctor discussed stereotactic radiosurgery (SRS). Pencil beams of radiation cross at the tumor delivering a killing dose to the tumor, but sparing the rest of the brain. On the evening before, my wife had an MRI (magnetic resonance imaging) of her head. The next morning she came into the center and they placed a lightweight frame on her head which they actually screwed in place into her skull. That sounds painful, but it wasn't. They gave her a CT scan with the frame in place.

Then came the hard part, waiting for hours while the doctors and the computer planned the treatment. The actual treatment itself lasted less than twenty minutes. We went home that afternoon. In fact, my wife was able to attend family get-together the next night. Not bad for outpatient brain surgery.

Stereotactic Radiosurgery (SRS) is a technique that delivers high energy photons with surgical precision by rotating the pencil beams around the point to be treated. Each beam carries a minimal amount of radiation, but the point where the beams cross gets a concentrated dose of radiation.

High energy photons pass all the way though the human body. So if you want to use X-rays to treat a tumor, you must irradiate all the healthy tissue in front of and behind the tumor. Some healthy tissue, such as the brain stem and spinal chord are extremely sensitive to and easily damaged by radiation.

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