New radiation technologies, some previously seen only in robotics laboratories, military sites, or even science fiction, are now emerging in oncology treatment rooms. They potentially allow physicians to provide radiation therapy that is more targeted, possibly causing less damage to surrounding tissue, enabling use of stronger radiation doses, and necessitating fewer treatments.
Since the 1890s, when it was first concluded that x-rays could be used for therapeutic as well as diagnostic purposes, researchers have continued to seek new methods for radiation therapy. The objective: to get a high dose of radiation to the tumor while protecting the surrounding normal tissue from radiation damage.
Robotic Vision
One approach, taken by a trio in Pittsburgh, was to equip a radiation accelerator with artificial vision. "Currently its the operator who knows where the patient isthe machine does not," said André M. Kalend, Ph.D., an associate professor of radiation oncology at the University of Pittsburgh Medical Center. "If we can make the machine sense the patient, then I think we have [taken] a giant step forward into knowing where the patient is at the instant of radiation."
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"Robotics artificial vision" (RAV) includes eight "eyes," or cameras, mounted on the walls of the treatment room and on the movable treatment machine. The eyes use charged coupled devices, or CCD vision, the main sensors used today for both human and robotics artificial vision.
The eyes work independently, focusing on the patients natural skin features. If the patient moves during treatment and is no longer aligned, the robotics system will shift the treatment table as needed to move the patient to original alignment.
Kalend and his colleagues have used volunteers to test the machines ability to recognize and track patients. They have not treated any patients with the technology; they are awaiting approval to begin clinical trials.
C. Norman Coleman, M.D., director of the Radiation Oncology Sciences Program at the National Cancer Institute, agreed that robotics and artificial intelligence could be useful. "Any way you take out uncertainty is a good thing, so taking away external motion is good," Coleman said. "But even when you have corrected for external anatomy, you still have to worry about internal organ motion. And there, again, we try to get more and more precise; every few millimeters becomes important. But if you get too precise you may miss the tumor."
Another technology called the CyberKnife, essentially image-guided robotic radiosurgery, has made its way into a handful of radiation therapy treatment rooms. The CyberKnife guides radiation to the tumor target using technology similar to that developed by the Pentagon to aim Cruise missiles during the Persian Gulf War.
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The CyberKnife uses the skeletal structure of the body as a reference frame for localizing the target instead of a rigid body or head frame that is commonly used. The computer controlling the radiation beam makes constant tiny corrections for the slightest movements. Fractionation of treatmentdelivery of radiation over a period of daysis also possible since the lesion is localized using image guidance technology rather than the stereotactic frame.
According to Adler, about 1,000 patients have been treated to date with the CyberKnife. Five sites in the United States are using it to treat tumors of the brain, the head and the neck region, and the upper cervical spinal cord. Of those sites, the Cleveland (Ohio) Clinic Foundation and Stanford University Medical Center are also treating tumors of the lung, pancreas, lumbothoracic spine, and prostate under investigational device exemptions.
"I think its clever," Coleman commented on the CyberKnife, "but I think its just another way to deliver radiation." He pointed out that the relatively large price tag might also be an issue for many institutions.
"I think technology takes you only so far. Theres only so much that you can optimize technology. Beyond that you have to work on the biologyunderstanding what radiation does in terms of activating molecular processes and what molecular processes in the cell make the cell resistant or sensitive to radiation. When you understand those, you can imagine radiation being used totally differently."
Coleman noted that in addition to the need to better understand the underlying biologic mechanisms, there also must be a way for the new technologies to not leave people behind, both radiologists and patients.
"I think were getting close to optimizing technology," he said. "Getting it down and then having it percolate into the community is tough because these are very expensive machines, and even more expensive than buying them is running them. We need to be able to have systems that can deliver goods to the vast majority of people."
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