Pittsburgh, PA -- July 26, 2004 -- New specialized imaging techniques and stereotactic approaches to radiation therapy are beginning to help radiation oncologists improve the quality of radiation therapy for the treatment of cancer and make it more widely applicable to a greater variety of cases.
Four prominent medical physicists made these observations at a symposium sponsored here yesterday by Varian Medical Systems (NYSE:VAR), in connection with the annual meeting of the American Association of Physicists in Medicine (AAPM).
The medical physicists, Timothy Fox, PhD, of Emory University in Atlanta; Fang-Fang Yin, PhD, of Henry Ford Health System in Detroit; Frank Bova, PhD, of the University of Florida in Gainesville; and Michael Lovelock, PhD, of Memorial Sloan-Kettering Cancer Center in New York, presented information from their clinical and research experience with new technologies for image-guided radiation therapy (IGRT) and the use of medical linear accelerators to deliver stereotactic radiosurgery.
Dynamic Targeting(tm) Image-Guided RadiationTherapy
In separate talks, Dr. Fox and Dr. Yin detailed their early experiences with Varian's new On-Board Imager(tm) system for IGRT, an automated, robotic device that uses low-dose, high-resolution imaging and sophisticated software tools to track tumor position and allow clinicians to adjust for position changes at the moment of treatment. Their institutions were the first in the U.S. to acquire Varian's On-Board Imager earlier this year and begin using it to position patients for treatment.
According to Dr. Fox, Emory clinicians found that most patients needed to be shifted up to three to four millimeters prior to treatment, in order to bring a targeted tumor into the best possible alignment with the treatment beam. Each treatment took an average of 17 minutes, including three to five minutes for imaging and repositioning, making the process efficient and clinically viable.
"As our physicians gain confidence in the precision of patient setups, they will be more confident about developing treatment plans that reduce the margin of healthy tissue treated," he said.
According to Dr. Yin, physicians at Henry Ford Health Center are planning to use their On-Board imager to develop a breast cancer treatment protocol that compensates for respiratory motion during treatment. "Dealing with the problem of respiratory motion when treating breast cancer has long been an issue for radiation oncologists," Dr. Yin said. "We feel that the On-Board Imager will be of tremendous value in helping us improve the quality of breast cancer treatments."
Dr. Bova talked about ways of using a medical linear accelerator--the treatment delivery machine used in radiation oncology departments--to deliver stereotactic radiosurgery, an ultra-precise technique that requires very accurate patient positioning because high doses of radiation are administered in a single treatment session. One of the early developers of what is now Varian's treatment planning software for stereotactic radiosurgery, Dr. Bova has pioneered the use of radiosurgical techniques for treating intra- and extra-cranial tumors.
"We've taken the classic radiosurgical approach used by neurosurgeons for the last 20 years, and proven that we can duplicate the results, not with specialized neurosurgical technology, but by using a medical linear accelerator outfitted with a 120-leaf multileaf collimator," a sophisticated beam-shaping device made by Varian Medical Systems. "The plans we create are not only as conformal, but they can be delivered much more efficiently with the linear accelerator than with traditional neurosurgery technologies," Dr. Bova said.
According to Dr. Bova, this opens the door to treating very small lesions in the brain or body with very high doses of radiation delivered in a single treatment session, with increased preservation of surrounding healthy tissues.
Using Cone-Beam CT Imaging for More Accurate Tumor Targeting
Dr. Lovelock presented data about how the use of a special form of three-dimensional imaging, cone-beam CT, can be expected to both "simplify the accurate delivery of radiation dose to tumors, and to enable entirely new treatment strategies" for treatment of tumors in the brain and body. According to Dr. Lovelock, studies at Memorial Sloan-Kettering Cancer Center are investigating how pre-treatment cone-beam CT scans could be used to yield accurate data about small rotational misalignments that occur during patient
"Cone-beam CT scanning has great potential for improving dose delivery to soft tissue structures" like the prostate, he said. "We're also looking into how we might use cone-beam CT to help us treat patients who have a small number of metastases with very high doses delivered in a single treatment session," he added.
"It's exciting, to see how medical physicists are using Varian technology to improve the quality of cancer care," said Richard M. Levy, chairman and CEO of Varian Medical Systems, sponsor of the symposium at which these presentations were made. "At Varian, we are committed to providing healthcare professionals with clinically powerful, cost-effective solutions for helping people beat cancer."