New Varian Medical Systems' Technology for Increasing Precision of Cancer Radiotherapy Gains FDA Clearance
(Health Wire)
A new technology for automatically controlling a radiation beam to compensate for tumor movement caused by a patient's breathing has just been granted FDA 510(k) clearance.
The new technology, called the RPM Respiratory Gating System from Varian Medical Systems Inc. (Palo Alto, CA), is being heralded as the latest breakthrough in treating cancerous tumors with ultra-precise x-ray beams.
A common standard of cancer care with expensive, heavy-ion machines in Japan, respiration-gated treatments were introduced at the University of California Davis Cancer Center in 1996 by Dr. Hideo Kubo. Dr. Kubo reported its technical feasibility using a Varian Medical Systems Clinic linear accelerator commonly found in most U.S. clinics. Since then, Dr. Kubo and Varian Medical Systems have jointly developed the current gating system. The RPM (real-time position management) Respiratory Gating System is an integral element in Varian Medical Systems' new generation of medical linear accelerators which radiation oncologists use to treat cancer.
Today, radiation is used in more than half of all cancer treatments due to its unique clinical advantages. Radiotherapy has become steadily more effective with new technologies that permit precise dose delivery. Preliminary calculations using RPM Respiratory Gating technology indicate that it is possible to reduce the radiation field to avoid hitting healthy, critical tissues while delivering higher doses to tumors. This should improve the chances of controlling tumors locally.
One of the ongoing challenges facing the radiation oncology community is how to deliver more cancer-killing energy to a tumor while simultaneously minimizing exposure to surrounding healthy tissue. Modern diagnostic imaging tools like CT scanners and computerized mechanical devices used to shape radiation beams are combined in treatment techniques called 3D conformal therapy.
The most advanced conformal technique in clinical use today is called Intensity Modulated Radiotherapy or IMRT. While these techniques are effective in sculpting radiation beams to the exact shape or volume of the tumor, they don't address the movement of a lesion when a patient breathes during radiotherapy treatment. Lung nodules, liver lesions, breast and chest wall tumors are subject to such motion.
To date, the standard technique has been to treat a larger area around the cancer, ensuring that the tumor receives radiation during its full range of motion. However, such over compensation subjects healthy tissue to the potentially harmful effects of radiation.
Varian Medical Systems' RPM Respiratory Gating System provides a low-cost and simple means of monitoring and correcting for patient motion during treatment. The system is also seen as a means for making IMRT and other conformal treatments even more precise. Using video technology, the system holds or "gates" the radiation beam when the tumor is beyond specified tolerances, and turns the beam on when the tumor is within the prescribed range. The technology automatically treats the tumor, and only the tumor, during those intervals when it falls within the desired location.