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Winter 2003 AAMC Takes the Lead in Non-Invasive Brain Tumor SurgeryAnne Arundel Medical Center is one of only a few centers in the United States and the only Mid-Atlantic hospital to offer a revolutionary form of stereotactic radiosurgery to patients suffering from brain tumors using a new technology called Novalis® Shaped Beam SurgeryTM. This new technology, which offers enormous hope to patients with inoperable brain tumors, is available at AAMC because of the highly skilled and trained staff who will provide the treatment. They include Clinical Medical Physicist Robert Siddon, Ph.D., neurosurgeons Tim Burke, M.D., Thomas Ducker, M.D., Brian Sullivan, M.D. and radiation oncologists Angel E. Torano, M.D., Mary E. Young, M.D. Similar to the GammaKnife®, Novalis uses highly focused beams of radiation to irradiate tumors with the highest level of accuracy. However, unlike the GammaKnife, Novalis uses a special technique that exactly mirrors the tumor, thereby avoiding healthy brain tissue. In addition, Novalis has applications for tumors outside the brain, where as the GammaKnife is only used for brain tumors. Dr. Siddon, former chief of clinical physics at Harvard Medical School and associate professor of Health Science and Technology at the Massachusetts Institute of Technology, was instrumental in the development of the software used to create Novalis. While at Harvard in the mid ’80s, he wrote the computer programs that Novalis uses to provide the mirror-like image that makes Novalis revolutionary in the field of radiosurgery. “People in this region are indeed fortunate to have the technology and the experts—our radiation oncologists, neurosurgeons and Dr. Siddon — so close to home,” said Dr. Stanley Watkins, medical director for Oncology. He said the advent of regional hospitals providing the most advanced techniques to patients will become the norm at hospitals such as Anne Arundel Medical Center, where highly trained physicians specialize in different areas of medicine, without the encumbrances of teaching hospitals. What IS Stereotactic Radiosurgery? When a patient is diagnosed with a brain tumor, surgeons evaluate the size and location of the tumor before developing a treatment plan. Because the brain is the most delicate and sophisticated organ of the body, surgery to remove a tumor is often an unacceptable option for fear of harming healthy brain tissue during surgery. In such cases where surgery is not an option, surgeons will treat tumors with chemotherapy or radiation or a combination of the two. In chemotherapy, chemotherapeutic drugs are given to either inhibit the division of tumor cells or kill them. However, some drugs are not suitable for the treatment of brain tumors because they cannot pass the blood-brain barrier. Radiation therapy is used to kill the tumor cells and to shrink or destroy the tumor. The beam of radiation changes the DNA in cells, which prevents them from reproducing and ideally kills the tumor. To keep from destroying healthy brain tissue, small beams of radiation pass through the tumor area from several points outside the brain, thereby delivering a minimal amount of radiation to healthy tissue, but overlapping and delivering a lethal dose to the tumor area, or isocenter. This is why it’s called ‘stereotactic’. It’s not a single strong beam, but many weak beams. In the past, radiation therapy was not as precise as Novalis because some healthy tissue inevitably was damaged. Novalis uses an innovative approach to mirror the exact dimensions of the tumor by using a beam shaping device called a multi-leaf collimator, that moves a full 360 degrees around the head. By using a complicated series of equations, the exact dimensions of the tumor can be computed and the collimator programmed to deliver a beam of radiation that mirrors those dimensions. As the beam moves around the head, the leaves of the collimator move in and out in correlation to the tumor, thereby eradicating the tumor and avoiding healthy brain tissue. |
