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science. medicine. health.

CyberKnife


A new weapon in the battle against cancer

Courtney Miller

Fall 2005


cyberknife cancer radiation    Overcoming cancer has always been thought of as a battle--there are those who can win and those who cannot. From the debilitating effects of chemotherapy to the time spent recovering from surgery, surviving cancer becomes a full-fledged war with the body. Fortunately, there has been an explosion in the development and application of new techniques in the fight against cancer, and it seems that every field of cancer research is brimming with potential and hope. One of the most promising fields in medicine today is radiation oncology.

    Radiation has long since been an effective weapon in a physician’s arsenal against tumor control. In the 1950s, radiation was first used for patients with lymphoma. Doctors shot a very high dose of X-rays through the patient’s body in hopes of destroying the tumor and its ability to grow. Though this radiation was effective in killing tumors, it also damaged surrounding healthy cells. Recently, researchers have perfected a new technique that allows successful treatment sans excessive blood loss or even the use of scalpels. This novel surgical approach employs the CyberKnife, a giant robotic arm that delivers therapeutic radiation with incredible precision.

    Derived from a machine that manufactures automobiles, the CyberKnife was invented by researchers at Stanford University in 1998. The machine stands over 14 feet tall and is composed of three main parts: a compact linear accelerator (LINAC) and a robotic base and arm. The latter two components guide the radiation to exact locations on the patient’s body, which lies on a table beneath the machine. Mounted on the robot arm, the LINAC is responsible for holding and delivering the doses of radiation. A computer system located outside the CyberKnife room guides the robotic arm by using detailed imaging information and complicated mathematical processes that essentially create a three dimensional representation of the tumor. This information then directs the robotic arm to the tumor’s exact location. To ensure accuracy, information from the computer aligns with the data from the marker location to keep the radiation beams on track at all times. While the patient lies on a bed underneath the robotic arm, a series of X-ray and magnetic resonance imaging (MRI) machines surround the patient in order to report any patient movement to the computer. The CyberKnife is thus able to compensate for the patient’s motion by adjusting its pathway.

    Since the image-guided system allows the patient to relax or even sleep during the surgery, it provides a considerable advance in comfort over the older stereotaxic method, which required patients to wear a metal brace to prevent movement. To help steer the CyberKnife, surgeons place fiducial makers—which are gold particles readily visualized by most imaging technology—into the region in which they will operate. Previously, many tumors were considered inoperable because of the movement associated with the patient inhaling and exhaling. Now, however, with the placement of fiducial markers into the interior of the tumor, the computer can keep track of its location, despite any breathing or movement, and keep the radiation precisely on target. Although the placement of these markers requires a small surgery and an incision in the neck where the guide wire is placed, this a small price to pay for its life saving results.


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