June 2007

The Department of Radiation Oncology's array of state-of-the-art equipment has recently gotten larger with the addition of new technology from Varian Medical Systems that allows physicians to target tumors more precisely by calculating their natural movement, thereby minimizing damage to nearby healthy tissues.

The new cone-bean computed tomography (CT) system works with the department's existing On-Board Imager, also known as Image Guided Radiation Therapy (IGRT) -- an automated system that uses high-resolution X-rays to produce contrasting images of cancerous tumors and surrounding soft tissue. Before the On-Board Imager, physicians would have to treat a larger area of the body near the cancerous tumor to compensate for tumor movement, as the radiation treatment would not be as effective if the entire tumor were not targeted. However, the new cone-beam CT technology works with the On-Board Imager to allow physicians to deliver the most accurate treatment possible.

The cone-beam CT system is part of the On-Board Imaging technology that is mounted directly on PAMF's existing Intensity-Modulated Radiation Therapy (IMRT) linear accelerator. Cone-beam CT images are created by continually generating X-ray images while rotating the imaging technology around the patient. By rotating the beam around the targeted region, the tumor can be observed, and its location measured, at many angles. This produces a highly accurate image of the tumor for final patient positioning and possible dose adjustments immediately before the accelerator delivers the radiation therapy.

To further account for tumor movement during the treatment process, the department's new RPM Respiratory Gating system, also from Varian, works with the other equipment to monitor tumor movement specifically due to respiration, or breathing. The system uses a sophisticated video monitor that captures a patient's breathing pattern. It can establish a baseline breathing pattern for a patient to account for any unanticipated movement, such as sneezing or coughing. This allows doctors to create treatment plans for patients in which the radiation beam only turns on to deliver a treatment dose when the tumor falls within the planned beam aperture, or path of the treatment beam.

"We can view a tumor's movement in the body as a patient breathes and deliver the treatments at the point in a patient's respiratory cycle where the tumor stands still," said Gordon Ray, M.D., head of the Department of Radiation Oncology. "Because this technology is so much more precise, we can reach and treat tumors that were once thought to be untreatable because of their proximity to vital organs and other soft tissue."

The Respiratory Gating system is designed to be used on any area where breathing may cause tumor motion, including but not limited to the lung, breast, liver, pancreas, kidney and organs in the pelvic region, such as the prostate.

"Our goal is to improve the precision and effectiveness of cancer treatment," said Dr. Ray. "This new technology allows PAMF to offer the safest, most advanced radiation treatments found only at a few hospitals and universities in the country. It puts PAMF at the forefront of radiation oncology."