Varian readies On-Board Imager

The FDA has signed off on a key imaging accessory for Varian's linear accelerators. The x-ray imaging subsystem, called On-Board Imager, will serve as an integrated, robotic platform for image-guided cancer treatment, improving the precision of cancer treatments by targeting and tracking tumors in real-time. A critical piece of the company's image-guided radiation therapy (IGRT) initiative, the automated subsystem will help physicians adjust the focus of radiation to fit changing tumor locations due to changes in patient positioning and motion caused by physiological processes such as respiration.

On-Board Imager will be mounted on the linear accelerator via robotically controlled arms that operate along three axes of motion, allowing them to be positioned optimally for the best view of the tumor. An amorphous silicon flat-panel detector records digital images showing internal anatomic landmarks, tracking motion of the tumor. The subsystem incorporates a 150-kV x-ray tube that assists in generating CT-quality images from a moving gantry.

On-Board Imager will be sold as an option on Varian's newly installed high-energy Clinac linear accelerators and as an upgrade for most digital Clinac accelerators already in place at clinical sites. It will be standard on Trilogy, a linear accelerator developed to support stereotactic and other advanced forms of radiotherapy. Trilogy was introduced as a prototype in October 2003 and received FDA 510(k) clearance in January. In concert with On-Board Imager, Trilogy will utilize radiographic, fluoroscopic, and, later this year, 3D cone-beam CT images.