Dynamic Edge Gating Radiotherapy Automates Response to Organ Motion

New radiotherapy technology automates the response to organ motion that occurs during the delivery of radiation to prostate cancer tumors in order to protect healthy tissue from unintended radiation. As a result, this technology may enable an additional decrease in the side effects associated with prostate radiotherapy, such as bowel and bladder incontinence and sexual dysfunction.

Calypso Medical Technologies, Inc. (Seattle, WA, USA), a developer of real-time localization technology used for the precise tracking of tumors, announced it has received 510(k) clearance from the U.S. Food and Drug Administration (FDA) to market the Calypso system with dynamic edge gating technology. The Calypso system, with its global positioning system (GPS) for the Body technology, utilizes miniature implanted Beacon transponders to provide precise, continuous information on the location of the tumor during external beam radiation therapy. The real-time position information provided by the Calypso system allows physicians to deliver maximum radiation directly to the tumor while sparing the surrounding healthy tissues and organs from exposure.

The new gating technology allows therapists to set motion thresholds that automatically signal radiation delivery to be stopped each time the targeted tissue moves outside the preset threshold. Previously the Calypso system, which provides target position information in the form of objective data, relied upon the therapist to manually intervene and halt radiation delivery when healthy tissue was in danger of receiving unintended radiation. Dynamic edge gating technology automates this function with an immediate signal to the linear accelerator so the radiation beam can be disabled or re-enabled in response to organ motion. The dynamic edge-gating feature will be compatible with linear accelerators, the equipment that produces the radiation beam, manufactured by Siemens Medical (Erlangen, Germany) and Varian Medical Systems (Palo Alto, CA, USA).

"The automatic response of the Calypso system to organ motion results in benefits to both the patient and the department,” said Lorraine Marshall Wright, chief marketing officer and vice president of Calypso Medical. "Holding the radiation beam when the target is outside of clinician-defined limits results in a safer, more uniform approach to radiation delivery, which may lead to a decrease in the side effects of prostate radiotherapy. Additionally, as with any automated process, improvements in workflow efficiency will be appreciated for maximizing throughput and enhancing the patient experience.”

Side effects result when the tumor moves outside of the radiation field in response to normal physiologic processes such as digestion, coughing and breathing, as well as small movements by the patient, while radiation is being delivered. As a result, healthy tissue receives the intended radiation, and at the same time, the tumor fails to receive the fully prescribed radiation dose thereby compromising effectiveness of the therapy. Whereas some side effects may resolve over time, many do not, leaving the patient with a significant impact to their quality of life.

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