Linear Accelerator Powers Novel Radiation Therapy System

A next-generation linear accelerator (linac)-based magnetic resonance imaging (MRI)-guided radiation therapy (RT) system improves treatment efficacy.

The ViewRay MRIdian Linac system integrates real-time MRI, linac-based RT delivery, and intelligent software automation to provide high-quality pretreatment images and continuous soft-tissue imaging during RT treatment, in real time, in order to accurately align the tumor to the treatment beams, adapt or reshape treatment volume, and to accommodate changes in the shape and location of the tumor and healthy internal structures.


The system includes a rotating gantry assembly that a houses a compact inline S-band 6 MV standing wave linac, with side-coupled cavities and double focused multi-leaf collimator technology; a patented magnetic and RF shielding technology that isolates the workings of the linac and the MRI system from each other; and a 0.35 T split magnet designed for unrestricted beam path, volumetric, and multi-planar soft tissue imaging. The system also includes a patient couch with three degrees of freedom, two in-room couch control panels, and a laser positioning system to facilitate initial patient setup.

A planning station helps define structures and constraints for initial planning and re-optimization of RT treatments and management of the treatment delivery process, and also supports subsequent reviews via a database server containing patient and machine data. A control console just outside the treatment room is paired to an operator console for MRI acquisition, patient positioning, dose prediction, and real-time tumor tracking. The MRIdian Linac system has been approved by the U.S. Food and Drug Administration (FDA).

“With MRI-guided radiation therapy, we're able to watch the movement of tumors and organs in the body as radiation is being delivered and adapt the dose of radiation in real time, to help ensure the maximum dose reaches the tumor and that surrounding healthy tissue is spared,” said Sasa Mutic, PhD, director of radiation oncology physics at Washington University School of Medicine. “This technology helps us treat tumors such those in the lung, liver, and pancreas, where increased precision is important due to nearby organs and other critical structures.”

A linac uses microwave technology to accelerate electrons, forming high energy x-rays that can be shaped to conform to the shape of the patient's tumor in a customized beam. The beam may be shaped either by blocks or a multileaf collimator incorporated into the head of the machine. RT can be delivered to the tumor from any angle by rotating the gantry and moving the treatment couch.